Wood nanocellulose hydrophobic oil-resistant agent, preparation method and application

Abstract

The invention discloses a wood nanocellulose hydrophobic oil-resistant agent as well as a preparation method and application thereof, and belongs to the technical field of oil-resistant agent preparation. According to the preparation method of the wood nanocellulose hydrophobic oil-resistant agent provided by the invention, a hydrogen bond acceptor, a Bronsted acid donor and a Lewis acid metal salt are adopted to construct a ternary eutectic solvent, a lignin network in chemi-mechanical pulp is cooperatively cracked, and a catalytic environment is provided; synchronously adding chemi-mechanical pulp and a bio-based modifier coumaric acid-phytosterol ester into the solvent, and integrally completing in-situ nanocrystallization dissociation and surface hydrophobic esterification functionalization of the fibers in an inert atmosphere; and carrying out shearing dispersion assisted by dihydrolevoglucosenone, centrifugal purification and reduced pressure distillation on the reaction mixture to obtain the wood nanocellulose hydrophobic oil-resistant agent. According to the method, synchronous construction of efficient nano dissociation and a modified catalytic environment of the chemi-mechanical pulp is achieved through the ternary eutectic solvent, a nano-crystallization-hydrophobic oil-resistant modification integrated process is achieved, toxic and harmful substances are avoided, and the method is green and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of anti-oil agent preparation technology, specifically to a lignocellulosic nanocellulose hydrophobic anti-oil agent, its preparation method, and its application. Background Technology

[0002] Nanocellulose exhibits great potential in packaging, coating, and composite materials due to its excellent properties such as renewability, biodegradability, and high specific strength. However, its abundant hydroxyl groups on the surface make it hydrophilic, limiting its application in waterproofing and oil-resistant applications. Existing technologies typically employ a two-step process of first preparing nanocellulose and then modifying the surface for hydrophobicity. This process is lengthy, energy-intensive, and often uses fluorinated compounds or toxic silanes, which is inconsistent with the trend towards green chemistry.

[0003] Mechanical chemimetallic pulp, as a high-yield and low-cost pulp, is an ideal raw material for the preparation of nanocellulose. However, its high lignin content poses a challenge to traditional nano-sizing methods. Eutectic solvents, as a novel green solvent, have shown unique advantages in biomass pretreatment. However, existing technologies mostly focus on component dissociation rather than functional integration. Furthermore, most existing eutectic solvents are binary systems, which have limited dissociation effects on nano-sizing raw materials with high lignin content, such as mechanical chemimetallic pulp, and cannot simultaneously provide the catalytic environment required for the modification reaction.

[0004] Therefore, how to achieve efficient nano-sizing of chemical mechanical pulp has become a technical challenge that urgently needs to be overcome by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a lignocellulosic nanocellulose hydrophobic and oil-resistant agent, its preparation method, and its application, so as to overcome the problem that the nano-sizing efficiency of chemical mechanical pulp in the prior art is low and it is difficult to achieve efficient utilization.

[0006] The present invention solves the above-mentioned technical problems through the following technical solution: This invention provides a method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent, comprising the following steps: Hydrogen bond acceptor, Brønsted acid donor and Lewis acid metal salt are mixed in a predetermined molar ratio and heated to obtain a ternary eutectic solvent; A chemical slurry and coumaric acid-phytosterol ester were added to a ternary eutectic solvent, and the reaction was carried out under inert gas protection and stirring to obtain a reaction mixture. The reaction mixture was mixed with dihydro-L-glucanone, and after high-speed shearing and centrifugation, a preliminary dispersion was obtained. The supernatant in the preliminary dispersion was extracted and distilled under reduced pressure to obtain a lignocellulose nanoparticle hydrophobic anti-oil agent.

[0007] A further improvement of this invention is that the hydrogen bond acceptor is betaine; the Brønsted acid donor is p-toluenesulfonic acid; the Lewis acid metal salt is ferric chloride; and the preset molar ratio is specifically 1:(0.8~1.2):(0.3~0.7).

[0008] A further improvement of the present invention is that the mass ratio of the chemimechanical slurry to the ternary eutectic solvent is 1:10 to 1:40; and the weight of coumaric acid-phytosterol ester added to the ternary eutectic solvent is 10% to 40% of the dry weight of the chemimechanical slurry added to the ternary eutectic solvent.

[0009] A further improvement of the present invention is that the inert gas used in the reaction under inert gas protection and stirring conditions is nitrogen or argon; the stirring speed is 300~1500 rpm; the reaction time is 2~5 hours; and the reaction temperature is 90℃~120℃.

[0010] A further improvement of the present invention is that the solid content of the lignocellulosic nanocellulose hydrophobic and oil-resistant agent is 1% to 5%.

[0011] A further improvement of this invention is that coumaric acid-phytosterol esters are pre-synthesized via enzymatic catalytic esterification, specifically including the following steps: Coumaric acid and phytosterol were mixed, and 5% to 10% of a biocatalyst and molecular sieve were added to the mixture. The mixture was reacted in tert-amyl alcohol solvent at 50°C to 60°C for 24 to 72 hours. The mixture was then evaporated, filtered, and cooled to crystallize to obtain coumaric acid-phytosterol ester.

[0012] A further improvement of the present invention is that the biocatalyst is an acid-resistant whole-cell catalyst.

[0013] A further improvement of the present invention is that the volume ratio of the reaction mixture to dihydrolevulinolone is 1:(2~5); and the centrifugation speed is 8000~12000 rpm.

[0014] This invention provides a woody nanocellulose hydrophobic anti-oil agent, which is prepared by the method described above.

[0015] This invention provides an application of the above-described wood-based nanocellulose hydrophobic and oil-resistant agent for the preparation of environmentally friendly packaging coatings, waterproof textiles, polymer-reinforced composite materials, or 3D printing photocurable resin compositions.

[0016] Compared with the prior art, the positive and progressive effects of the present invention are as follows: The present invention provides a method for preparing a lignin-cellulose nanoparticle hydrophobic and oil-resistant agent. This method constructs a ternary eutectic solvent composed of a hydrogen bond acceptor, a Brønsted acid donor, and a Lewis acid metal salt. This solvent efficiently disrupts the lignin-cellulose bonds within the chemimechanical pulp fibers and the hydrogen bonds between cellulose molecules, achieving efficient nano-dissociation of the chemimechanical pulp. Using chemimechanical pulp directly as a raw material, it fully leverages its high yield and low cost advantages. Through the synergistic effect of the Brønsted acid donor and the Lewis acid metal salt, it not only possesses excellent nano-dissociation capabilities of the chemimechanical pulp but also simultaneously provides a highly efficient catalytic environment for subsequent hydrophobic modification reactions. By directly adding the chemimechanical pulp and coumaric acid-phytosterol ester to the ternary eutectic solvent for reaction, the subsequent product can be obtained simply by mixing with dihydro-L-glucanone and undergoing high-speed shearing and centrifugation. This allows the nano-dissociation and hydrophobic and oil-resistant modification of the chemimechanical pulp to be completed within the same system, shortening the process flow. Furthermore, the entire preparation process generates no toxic or harmful substances and produces no difficult-to-treat waste, adhering to green chemistry principles from raw materials to the entire process, thus enhancing environmental safety. Attached Figure Description

[0017] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 This is a schematic diagram of the preparation method of the lignocellulosic nanocellulose hydrophobic and oil-resistant agent of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. This is an explanation of the present invention and not a limitation thereof.

[0023] See Figure 1 This invention provides a method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent, comprising the following steps: Hydrogen bond acceptor, Brønsted acid donor and Lewis acid metal salt are mixed in a predetermined molar ratio and heated to obtain a ternary eutectic solvent; A chemical slurry and coumaric acid-phytosterol ester were added to a ternary eutectic solvent, and the reaction was carried out under inert gas protection and stirring to obtain a reaction mixture. The reaction mixture was mixed with dihydro-L-glucanone, and after high-speed shearing and centrifugation, a preliminary dispersion was obtained. The supernatant in the preliminary dispersion was extracted and distilled under reduced pressure to obtain a lignocellulose nanoparticle hydrophobic anti-oil agent.

[0024] This invention integrates nano-sizing and functionalization processes in a one-step process, uses a ternary eutectic solvent to efficiently treat chemimechanical pulp with high lignin content, and simultaneously achieves hydrophobic modification, thus solving the problems of long process, high energy consumption, and use of toxic substances in the two-step process of the prior art. Specifically, a ternary eutectic solvent is generated by mixing hydrogen bond acceptors, Brønsted acid donors, and Lewis acid metal salts in a predetermined molar ratio and heating. This solvent provides strong dissociation and catalytic capabilities, effectively addressing the high lignin content of the chemimechanical pulp and creating a suitable environment for subsequent reactions. A reaction mixture is generated by adding chemimechanical pulp and coumaric acid-phytosterol ester to the ternary eutectic solvent and reacting under inert gas protection and stirring conditions. This step ensures that while the chemimechanical pulp is nano-sized, the coumaric acid-phytosterol ester achieves simultaneous hydrophobic functionalization through esterification, avoiding additional modification steps. The reaction mixture is then mixed with dihydro-L-glucanone, subjected to high-speed shearing and centrifugation to generate a dispersion, and the supernatant is extracted and distilled under reduced pressure to obtain a lignocellulose nanoparticle hydrophobic anti-oil agent. This process promotes dispersion and separation, purifying the product to enhance its hydrophobic and anti-oil properties.

[0025] Specifically, the hydrogen bond acceptor is betaine; the Brønsted acid donor is p-toluenesulfonic acid; the Lewis acid metal salt is ferric chloride; and the preset molar ratio is 1:(0.8~1.2):(0.3~0.7).

[0026] By specifically defining the composition and preset molar ratio of the ternary eutectic solvent, the catalytic and dissociation properties of the solvent were optimized. Betaine was designated as the hydrogen bond acceptor, and its stable hydrogen bond acceptance ability promotes the uniform formation of the eutectic solvent, providing a reliable foundation for subsequent reactions. p-Toluenesulfonic acid was designated as the Brønsted acid donor, providing a strongly acidic environment to effectively catalyze the dissociation of the chemimechanical pulp and the modification reaction of coumaric acid-phytosterol esters. Ferric chloride was designated as the Lewis acid metal salt, which acts as a synergistic catalyst to enhance lignin dissociation and nanocellulose generation. The preset molar ratio was 1:(0.8~1.2):(0.3~0.7) to ensure that the components work synergistically within a reasonable range, avoiding insufficient catalytic activity or decreased dissociation efficiency caused by imbalance in the ratio, thereby achieving a highly efficient and stable solvent system.

[0027] Specifically, the mass ratio of the chemimechanical pulp to the ternary eutectic solvent is 1:10 to 1:40; the weight of coumaric acid-phytosterol ester added to the ternary eutectic solvent is 10% to 40% of the dry weight of the chemimechanical pulp added to the ternary eutectic solvent.

[0028] By limiting the mass ratio of chemimechanical slurry to ternary eutectic solvent and the addition ratio of coumaric acid-phytosterol ester, the reaction conditions can be optimized to ensure that the efficient nano-sizing and surface modification of the chemimechanical slurry are carried out simultaneously, thereby improving the stability of the hydrophobic and oil-resistant properties of the product and the preparation efficiency.

[0029] Specifically, the inert gas used in the reaction is nitrogen or argon under inert gas protection and stirring conditions; the stirring speed is 300~1500 rpm; the reaction time is 2~5 hours; and the reaction temperature is 90℃~120℃.

[0030] The inert gas is nitrogen or argon, which can isolate oxygen and prevent oxidation side reactions, ensuring that the reaction takes place in a stable environment and avoiding damage to the hydrophobic properties of the product. The stirring speed is set to 300~1500 rpm. Stirring within this range can promote uniform mixing of reactants, prevent excessively high local concentrations or uneven temperatures, and improve reaction efficiency and product consistency. The reaction time is controlled at 2~5 hours to ensure that the reaction proceeds fully without being too long, reducing energy consumption and by-product formation. The reaction temperature is limited to 90℃~120℃ to optimize reaction kinetics, accelerate the dissociation and modification process of nanocellulose, and avoid high-temperature decomposition or insufficient low-temperature reaction, ensuring the stability of the final anti-oil agent performance.

[0031] Specifically, the solid content of the lignocellulosic nanocellulose hydrophobic and oil-resistant agent is 1% to 5%.

[0032] Specifically, coumaric acid-phytosterol esters are pre-synthesized via enzymatic catalytic esterification, including the following steps: Coumaric acid and phytosterol were mixed, and 5% to 10% of a biocatalyst and molecular sieve were added to the mixture. The mixture was reacted in tert-amyl alcohol solvent at 50°C to 60°C for 24 to 72 hours. The mixture was then evaporated, filtered, and cooled to crystallize to obtain coumaric acid-phytosterol ester.

[0033] Pre-synthesized using an enzymatic esterification method, leveraging the specificity and mildness of biological processes, avoids toxic reagents commonly found in chemical synthesis, ensuring a green source of the modifier. Coumaric acid and phytosterols are mixed to directly integrate the reactants, simplifying operations, promoting homogeneous reactions, and reducing byproduct formation. A specific ratio of biocatalyst and molecular sieve is added. The biocatalyst efficiently catalyzes the esterification reaction within a 5%–10% range, reducing dosage and increasing conversion rate, while the molecular sieve adsorbs moisture or impurities, maintaining reaction equilibrium and improving yield and selectivity. The reaction is carried out in tert-amyl alcohol solvent at 50℃–60℃. Tert-amyl alcohol is chosen because its polarity is suitable for enzyme activity, avoiding toxic solvents, and the temperature range optimizes enzyme stability and reaction kinetics, preventing high-temperature inactivation. The reaction time is set for 24–72 hours, with a reasonable time window to ensure complete reaction while controlling energy consumption and side reactions. Post-treatment and recrystallization remove unreacted substances and impurities, purifying the product and ensuring the purity and suitability of the coumaric acid-phytosterol ester, providing high-quality raw materials for subsequent modification.

[0034] Specifically, the biocatalyst is an acid-resistant whole-cell catalyst.

[0035] Using acid-resistant whole-cell catalysts can maintain activity in the acidic environment of enzyme-catalyzed esterification reactions, avoiding deactivation and thus improving reaction reliability and product consistency.

[0036] Specifically, the volume ratio of the reaction mixture to dihydro-L-glucosidone is 1:(2~5); the centrifugation speed is 8000~12000 rpm.

[0037] The volume ratio is set to 1:2~5 to ensure that dihydro-L-glucanone can fully dilute the reaction mixture, promote uniform mixing under high-speed shearing, and avoid uneven dispersion or concentration imbalance caused by excessively high or low ratios. The centrifugation speed is controlled at 8000~12000 rpm to ensure effective separation of solid particles under high-speed rotation, obtain a stable dispersion, and avoid energy waste or equipment overload caused by excessive speed, thereby improving the overall process efficiency.

[0038] This invention provides a woody nanocellulose hydrophobic anti-oil agent, which is prepared by the method described above.

[0039] This invention provides an application of the above-described wood-based nanocellulose hydrophobic and oil-resistant agent for the preparation of environmentally friendly packaging coatings, waterproof textiles, polymer-reinforced composite materials, or 3D printing photocurable resin compositions.

[0040] In a specific embodiment of the present invention, a method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent specifically includes the following steps: Step 1: Construction of the reaction system: Mix the hydrogen bond acceptor betaine, the Brønsted acid hydrogen bond donor p-toluenesulfonic acid, and the Lewis acid metal salt ferric chloride in a molar ratio of 1:(0.8-1.2):(0.3-0.7) and heat to 60℃-90℃ to form a homogeneous and transparent ternary eutectic solvent.

[0041] In the ternary eutectic solvent, the hydrogen bond acceptor is betaine, the hydrogen bond donor of Brønsted acid is p-toluenesulfonic acid, and the Lewis acid metal salt is ferric chloride; the molar ratio of the three is 1: (0.8-1.2): (0.3-0.7).

[0042] Step 2: Add a certain amount of chemimechanical slurry and coumaric acid-phytosterol ester to the ternary eutectic solvent described in Step 1, stir thoroughly to mix, and react at 300-1500 rpm for 2-5 hours under inert gas protection at 90℃-120℃; wherein the mass ratio of the chemimechanical slurry to the eutectic solvent is 1:10 to 1:40; and the amount of coumaric acid-phytosterol ester added is 10% to 40% of the dry weight of the chemimechanical slurry.

[0043] During the stirring process, the ternary eutectic solvent works synergistically to dissociate the cell wall structure of the chemimechanical pulp, making it nano-sized; at the same time, under acidic conditions, the carboxyl groups of coumaric acid-phytosterol ester undergo in-situ esterification with the exposed hydroxyl groups of cellulose, hemicellulose and lignin, covalently grafting hydrophobic groups onto the surface of nanofibers, achieving in-situ hydrophobic modification.

[0044] Coumaric acid-phytosterol esters are pre-synthesized from coumaric acid and phytosterol via enzymatic catalytic esterification. A biocatalyst (5%-10% of the total weight of the reactants) and a molecular sieve are added to a mixture of coumaric acid and phytosterol, and the mixture is reacted in tert-amyl alcohol solvent at 50℃-60℃ for 24-72 hours. The ester is then post-treated and recrystallized. The inert gas is nitrogen or argon; the biocatalyst is an acid-resistant whole-cell catalyst.

[0045] Step 3: Cyrene Dispersion and Purification: After the reaction is complete, cool the system to 50℃-70℃. Slowly add the reaction mixture to 2-5 times its volume of the green solvent Cyrene under high-speed shearing for 10-30 minutes to form a preliminary dispersion. The DES system is diluted and destroyed by Cyrene, losing its solubility. The newly hydrophobically modified lignin nanocellulose, due to the good compatibility of its surface-grafted phytosterol chains with Cyrene, will be stably dispersed in Cyrene, resulting in a lignin nanocellulose dispersion. Unreacted esterifying agents, DES components, and other impurities have limited solubility in Cyrene and some will precipitate due to changes in solubility.

[0046] Step 4: Purify the product: Centrifuge the obtained dispersion at 8000-12000 rpm for 10-20 minutes to remove a small amount of incompletely nano-sized precipitate and impurities at the bottom, and collect the supernatant. Distill the supernatant under reduced pressure at 50℃-70℃ and concentrate it to a solid content of about 1%-3% to obtain the target product: lignocellulose nanoparticles hydrophobic and oil-resistant agent.

[0047] The preparation method provided by this invention integrates three key steps—"nano-sizing," "hydrophobic modification," and "solvent dispersion"—into a single reaction system, achieving extreme simplification of the process flow. From raw materials (chemical-mechanical slurry, bio-based modifier) ​​to the process (DES, Cyrene), renewable, low-toxicity, or harmless chemicals are used throughout, constructing a complete green technology platform. Significant synergistic effects are achieved: DES has a dual function—the ternary DES is both a highly efficient nano-sizing agent and a catalyst for esterification reactions, providing dual benefits; the resulting dispersion also contains nanocellulose. The synergistic effect of cyrene, the hydrophobic and oil-resistant properties of phytosterols, and the UV shielding and inherent hydrophobicity of lignin is significant. Cyrene, as a green medium, has excellent compatibility with hydrophobic modified products, can form a long-term stable dispersion, and can form a dense and smooth coating after its own volatilization. The final product is a ready-to-use dispersion that can be directly used for coating, impregnation, or as a masterbatch for composite materials, which greatly facilitates downstream applications. This Cyrene dispersion has good compatibility with most hydrophobic polymers, providing an ideal raw material for the preparation of high-performance bio-based composite materials.

[0048] The lignocellulose nanoparticle hydrophobic and oil-resistant agent prepared by the above method is a stable colloidal dispersion with Cyrene as the dispersion medium. It can be used in the preparation of environmentally friendly packaging coatings, waterproof textiles, polymer-reinforced composite materials or 3D printing photocurable resin compositions.

[0049] Example 1: A method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent includes the following steps: Step 1: Weigh out betaine and p-toluenesulfonic acid and mix them at a molar ratio of 1:0.8. Heat the mixture in an oil bath to 50°C and stir magnetically for 30 minutes. Then add a certain amount of ferric chloride (molar ratio 0.3) and continue stirring for 15 minutes until the suspension becomes a homogeneous transparent liquid, which becomes a ternary eutectic solvent (DES) (the synthesized ternary eutectic solvent has stronger properties for dissolving lignocellulose). Step 2: Add oven-dried poplar chemimechanical pulp and coumaric acid-phytosterol ester to the ternary eutectic solvent (DES) synthesized in Step 1 at a solid-liquid ratio of 1:15, add a biocatalyst, and purge with nitrogen; after heating at 110°C and 800 rpm with magnetic stirring for 3.5 h, a woody nanocellulose solution is obtained. The coumaric acid-phytosterol ester is pre-synthesized from coumaric acid and phytosterol via enzymatic catalytic esterification. A biocatalyst (5% of the total weight of the reactants) and a molecular sieve are added to a mixture of coumaric acid and phytosterol, and the mixture is reacted in tert-amyl alcohol solvent at 60°C for 48 hours. The tert-amyl alcohol is recovered by rotary evaporation at 50–80°C and 0.08–0.1 MPa. The mixture is then filtered, cooled, and crystallized to obtain the coumaric acid-phytosterol ester. The added biocatalyst is an acid-resistant whole-cell catalyst.

[0050] Step 3: After the reaction is complete, lower the temperature of the viscous reaction solution to 60°C and slowly add it dropwise to twice the volume of Cyrene at a high speed of 10,000 rpm. Continue high-speed shearing for 20 minutes to form a preliminary dispersion.

[0051] Step 4: Centrifuge the mixture at 10,000 rpm for 15 minutes, collect the supernatant, and distill it under reduced pressure at 55°C to concentrate it to a solid content of 2.5%, obtaining a brown, homogeneous and stable target dispersion with a yield of 65%.

[0052] The dispersion was coated onto filter paper and dried in an oven at 80°C for 5 minutes. The static water contact angle of the coating was measured to be 142°±3°, and the resistance level to vegetable oil (olive oil) reached level 8 (TAPPI T559 standard).

[0053] Example 2: A one-pot method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent includes the following steps: Step 1: Weigh out betaine and p-toluenesulfonic acid and mix them in a molar ratio of 1:1. Heat the mixture in an oil bath to 70°C and stir magnetically for 20 minutes. Then add a certain amount of ferric chloride (molar ratio 0.5) and continue stirring for 10 minutes until the suspension becomes a homogeneous transparent liquid, which becomes a ternary eutectic solvent (DES) (the synthesized ternary eutectic solvent has stronger properties for dissolving lignocellulose). Step 2: Add oven-dried poplar chemimechanical pulp and coumaric acid-phytosterol ester to the ternary eutectic solvent (DES) synthesized in Step 1 at a solid-liquid ratio of 1:20, add a biocatalyst, and purge with nitrogen; after heating and stirring at 90°C and 1200 rpm for 4 hours, a woody nanocellulose solution is obtained. The coumaric acid-phytosterol ester is pre-synthesized from coumaric acid and phytosterol via enzymatic catalytic esterification. A biocatalyst (8% of the total weight of the reactants) and molecular sieve are added to a mixture of coumaric acid and phytosterol, and the mixture is reacted in tert-amyl alcohol solvent at 50°C for 60 hours. The tert-amyl alcohol is recovered by rotary evaporation at 50–80°C and 0.08–0.1 MPa. The mixture is then filtered, cooled, and crystallized to obtain the coumaric acid-phytosterol ester. The added biocatalyst is an acid-resistant whole-cell catalyst.

[0054] Step 3: After the reaction is complete, lower the viscous reaction solution to 55°C and slowly add it dropwise to 4 times the volume of Cyrene at a high speed of 11,000 rpm. Continue high speed shearing for 20 minutes to form a preliminary dispersion.

[0055] Step 4: Centrifuge the mixture at 15,000 rpm for 5 minutes, collect the supernatant, and distill it under reduced pressure at 60°C to concentrate it to a solid content of 3%, obtaining a brown, homogeneous and stable target dispersion with a yield of 62%.

[0056] The dispersion was coated onto A4 printing paper and dried in an oven at 80°C for 10 minutes. The static water contact angle of the coating was measured to be 148°±3°, and the resistance level to vegetable oil (olive oil) reached level 8 (TAPPI T559 standard).

[0057] Example 3: A one-pot method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent includes the following steps: Step 1: Weigh out betaine and p-toluenesulfonic acid and mix them at a molar ratio of 1:1.2. Heat the mixture in an oil bath to 60°C and stir magnetically for 15 minutes. Then add a certain amount of ferric chloride (molar ratio 0.7) and continue stirring for another 15 minutes until the suspension becomes a homogeneous transparent liquid, which becomes a ternary eutectic solvent (DES) (the synthesized ternary eutectic solvent has stronger properties for dissolving lignocellulose). Step 2: Add oven-dried poplar chemimechanical pulp and coumaric acid-phytosterol ester to the ternary eutectic solvent (DES) synthesized in Step 1 at a solid-liquid ratio of 1:10, add a biocatalyst, and purge with nitrogen; after heating at 110°C and 1200 rpm with magnetic stirring for 2 seconds, a woody nanocellulose solution is obtained. The coumaric acid-phytosterol ester is pre-synthesized from coumaric acid and phytosterol via enzymatic catalytic esterification. A biocatalyst (10% of the total weight of the reactants) and molecular sieve are added to a mixture of coumaric acid and phytosterol, and the mixture is reacted in tert-amyl alcohol solvent at 55°C for 48 hours. The tert-amyl alcohol is recovered by rotary evaporation at 50–80°C and 0.08–0.1 MPa. The mixture is then filtered, cooled, and crystallized to obtain the coumaric acid-phytosterol ester. The added biocatalyst is an acid-resistant whole-cell catalyst.

[0058] Step 3: After the reaction is complete, lower the viscous reaction solution to 50°C and slowly add it dropwise to 3 times the volume of Cyrene at a high speed of 9000 rpm. Continue high speed shearing for 18 minutes to form a preliminary dispersion.

[0059] Step 4: Centrifuge the mixture at 11,000 rpm for 12 minutes, collect the supernatant, and distill it under reduced pressure at 50°C to concentrate it to a solid content of 2%, obtaining a brown, homogeneous and stable target dispersion with a yield of 66%.

[0060] The dispersion was coated onto A4 printing paper and dried in an oven at 80°C for 10 minutes. The static water contact angle of the coating was measured to be 144°±2°, and the resistance level to vegetable oil (olive oil) reached level 7 (TAPPI T559 standard). The only difference between Examples 4 and 5 and Example 2 is the molar ratio of betaine, p-toluenesulfonic acid, and ferric chloride. Therefore, they will not be described in detail. Please refer to Table 1 for a summary of the parameters and results of each example.

[0061]

[0062] The preparation of nanocellulose using poplar chemimechanical pulp not only meets the requirements of low-carbon economic development, but also has certain practical significance for expanding the research on nanocellulose.

[0063] Based on the unique component properties of poplar chemimechanical pulp (cellulose content 44%, hemicellulose content 18%, lignin content approximately 28%), the product, after eutectic solvent-assisted esterification modification, is directly or after further treatment and stably dispersed in the green solvent Cyrene to form a ready-to-use lignin-cellulose nanoparticle hydrophobic dispersion (yield can reach over 60%, yielding nanoparticles with diameters between 10-50 nm). This dispersion combines environmental friendliness with high performance, opening up new avenues for the application of nanoparticle cellulose in the field of high-end hydrophobic materials.

[0064] The preparation method provided by this invention uses poplar APMP chemimechanical pulp as raw material, and places it together with coumaric acid-phytosterol ester in a ternary eutectic solvent composed of betaine, p-toluenesulfonic acid, and ferric chloride. Nano-sizing and in-situ hydrophobic esterification are achieved simultaneously through a one-step reaction. The reaction product does not require separation; it can be directly dispersed and purified using the green solvent Cyrene to obtain a stable hydrophobic and oil-resistant agent dispersion. This invention features a high degree of process integration and is environmentally friendly, achieving a direct conversion from low-cost raw materials to high-performance products. The resulting product exhibits excellent hydrophobic and oil-resistant properties and diverse applications, showing broad prospects in paper surface treatment, green packaging, textile coatings, and bio-based composite materials.

[0065] Finally, it should be noted that the embodiments listed above are merely one or more specific manifestations of the technical solution of this invention. Their purpose is to clearly illustrate the concept, principle, and application of this invention through specific examples, and is by no means intended to limit the scope of protection of this invention to these specific embodiments. In fact, the true value of this invention lies in its proposed technical ideas and innovations, rather than its manifestations or implementation methods.

[0066] For those skilled in the art, after thoroughly reading and understanding the technical solution of this invention, they are fully capable of making various changes, modifications, or equivalent substitutions to the specific implementation of the invention based on their own professional knowledge and skills. These changes may include, but are not limited to: adjusting the range of technical parameters, optimizing the algorithm flow to improve efficiency, and replacing some technical components to achieve better compatibility or reduce costs. As long as these modified technical solutions substantially retain the technical features claimed by the original invention, that is, they can still achieve the core functions and effects of this invention, then these changes should be considered to fall within the scope of protection of the pending claims of this invention.

[0067] Furthermore, with the continuous progress and development of technology, new technical means and methods are constantly emerging, which provides ample space for further improvement and perfection of this invention. Therefore, the scope of protection of this invention should also include reasonable and foresightful improvements and extensions based on existing technology. As long as these improvements and extensions do not depart from the basic principles and core concepts of this invention, they should be considered equivalents of this invention and are equally protected by patent rights.

Claims

1. A method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent, characterized in that, Includes the following steps: Hydrogen bond acceptor, Brønsted acid donor and Lewis acid metal salt are mixed in a predetermined molar ratio and heated to obtain a ternary eutectic solvent; A chemical slurry and coumaric acid-phytosterol ester were added to a ternary eutectic solvent, and the reaction was carried out under inert gas protection and stirring to obtain a reaction mixture. The reaction mixture was mixed with dihydro-L-glucanone, and after high-speed shearing and centrifugation, a preliminary dispersion was obtained. The supernatant in the preliminary dispersion was extracted and distilled under reduced pressure to obtain a lignocellulose nanoparticle hydrophobic anti-oil agent.

2. The method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent according to claim 1, characterized in that, The hydrogen bond acceptor is betaine; the Brønsted acid donor is p-toluenesulfonic acid; the Lewis acid metal salt is ferric chloride; the preset molar ratio is 1:(0.8~1.2):(0.3~0.7).

3. The method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent according to claim 1, characterized in that, The mass ratio of the chemimechanical pulp to the ternary eutectic solvent is 1:10 to 1:40; the weight of coumaric acid-phytosterol ester added to the ternary eutectic solvent is 10% to 40% of the dry weight of the chemimechanical pulp added to the ternary eutectic solvent.

4. The method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent according to claim 1, characterized in that, The reaction is carried out under inert gas protection and stirring conditions. The inert gas is nitrogen or argon; the stirring speed is 300~1500 rpm; the reaction time is 2~5 hours; and the reaction temperature is 90℃~120℃.

5. The method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent according to claim 1, characterized in that, The solid content of the lignocellulosic nanocellulose hydrophobic and oil-resistant agent is 1%~5%.

6. The method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent according to claim 1, characterized in that, Coumaric acid-phytosterol esters are pre-synthesized via enzymatic catalytic esterification, specifically including the following steps: Coumaric acid and phytosterol were mixed, and 5% to 10% of a biocatalyst and molecular sieve were added to the mixture. The mixture was reacted in tert-amyl alcohol solvent at 50°C to 60°C for 24 to 72 hours. The mixture was then evaporated, filtered, and cooled to crystallize to obtain coumaric acid-phytosterol ester.

7. The method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent according to claim 6, characterized in that, The biocatalyst is an acid-resistant whole-cell catalyst.

8. The method for preparing a lignocellulosic nanocellulose hydrophobic and oil-resistant agent according to claim 1, characterized in that, The volume ratio of the reaction mixture to dihydro-L-glucosidone was 1:(2~5); the centrifugation speed was 8000~12000 rpm.

9. A lignocellulosic nanocellulose hydrophobic and oil-resistant agent, characterized in that, It was prepared using the method described in any one of claims 1 to 8 for preparing the lignocellulosic nanocellulose hydrophobic and oil-resistant agent.

10. The application of the lignocellulosic nanocellulose hydrophobic and oil-resistant agent as described in claim 9, characterized in that, Used to prepare environmentally friendly packaging coatings, waterproof textiles, polymer-reinforced composites, or 3D printing photocurable resin compositions.

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