Method for preparing lignin-containing bagasse fiber based on ternary eutectic solvent

Abstract

The invention provides a method for preparing lignin-containing bagasse fibers based on a ternary eutectic solvent, and belongs to the technical field of component separation treatment. The method for preparing the lignin-containing bagasse fiber based on the ternary eutectic solvent comprises the following steps that pretreated bagasse and the ternary eutectic solvent are mixed and stirred for a reaction, cooling is conducted after the reaction is completed, washing is conducted after solid-liquid separation, and the lignin-containing bagasse fiber is obtained; the ternary eutectic solvent is composed of choline chloride, oxalic acid and lactic acid in a molar ratio of 1: (0-2): (1-3); the temperature of the mixing and stirring reaction is 90-120 DEG C, and the mixing and stirring reaction is carried out under normal pressure. The whole reaction process is carried out at lower temperature and lower pressure intensity, the operation is simple, the high-quality bagasse fibers with different lignin and cellulose contents can be extracted, and the subsequent research on the influence of the existence of different lignin contents on the performance of the cellulose and the high-value utilization of the bagasse fibers is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of component separation and treatment, and particularly relates to a method for preparing lignin-containing bagasse fibers based on a ternary deep eutectic solvent. Background Art

[0002] Lignocellulose is a basic component of plants and trees, which is mainly composed of three main components: cellulose, hemicellulose, and lignin. Utilizing lignocellulose resources can obtain high-value biological products to reduce the dependence on fossil fuels. Therefore, the rational utilization of lignocellulose has become an important strategy to address the global energy and environmental crises.

[0003] The separation of lignocellulose is a key link to improve the utilization efficiency of cellulose and lignin. However, due to the strong interaction between lignin and cellulose, lignocellulosic biomass is difficult to process, thereby reducing the separation and utilization rate of lignocellulose. In addition, some studies have shown that adding an appropriate amount of lignin to cellulose can improve the mechanical and chemical properties of cellulose-based materials. Therefore, if the co-separation of cellulose and lignin can be achieved, it is also an effective means to improve lignocellulose, which is of great significance for the high-value utilization of lignocellulose.

[0004] Previously, some scholars used deep eutectic solvents to extract single lignin at different temperatures and obtained the optimal lignin yield by controlling conditions such as temperature. Although the deep eutectic solvent pretreatment technology shows excellent performance in lignin extraction and has the advantages of easy preparation, low cost, green and pollution-free, etc., how to obtain cellulose with different lignin contents is still an important problem that needs to be solved urgently. Summary of the Invention

[0005] To solve the above technical problems, the present invention proposes a method for preparing lignin-containing bagasse fibers based on a ternary deep eutectic solvent. By using the ternary deep eutectic solvent to regulate the lignin content inside the bagasse fibers, lignin-containing bagasse fibers that can be used for ultraviolet protection films and antibacterial packaging films are obtained, realizing the high-value utilization of lignocellulose.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention:

[0008] A method for preparing lignin-containing bagasse fibers based on a ternary deep eutectic solvent, comprising the following steps:

[0009] Mix the pretreated bagasse with a ternary deep eutectic solvent (DES) and stir to react. After the reaction is completed, cool it, separate the solid and liquid, and wash to obtain the lignin-containing bagasse fiber; the ternary deep eutectic solvent is composed of choline chloride (ChCl), oxalic acid (OA), and lactic acid (LA) with a molar ratio of 1∶(0 - 2)∶(1 - 3) (where the dosage of OA is not 0).

[0010] Technical principle: In the ternary deep eutectic solvent composed of choline chloride (ChCl), oxalic acid (OA), and lactic acid (LA), choline chloride acts as a hydrogen bond acceptor, and oxalic acid and lactic acid together act as hydrogen bond donors. The introduction of the third component can selectively dissolve lignin by adjusting hydrogen bonds and π-π interactions, and cellulose is well retained; moreover, the ternary deep eutectic solvent can quickly break the "anti-depolymerization barrier" of lignin, thereby increasing the degradation rate of lignin. The DES used in the present invention for extracting lignin-containing bagasse fiber is composed of ChCl, OA, and LA with a molar ratio of 1∶(0 - 2)∶(1 - 3), where the dosage of OA is not 0. In the presence of OA, the efficiency of extracting lignin-containing bagasse fiber by DES is higher than that without OA. The addition of OA reduces the degree of polymerization of the lignin-containing bagasse fiber and promotes fiber degradation. However, as the proportion of OA in the DES increases, the β-O-4′ structure in lignin is damaged and the lignin extraction rate decreases. Therefore, in order to obtain lignin-containing bagasse fiber with appropriate lignin and cellulose contents, the present invention limits the molar ratio of ChCl, OA, and LA in the DES to 1∶(0 - 2)∶(1 - 3).

[0011] The temperature of the mixing and stirring reaction is 90 - 120 °C and it is carried out under normal pressure.

[0012] Furthermore, the addition amount of the bagasse in the ternary deep eutectic solvent is 2.5 wt%.

[0013] Furthermore, the pretreatment of the bagasse includes the following steps: Wash the bagasse with water, dry, crush, and pass through an 80 - 100 mesh sieve, and then dry the obtained bagasse powder again to obtain the pretreated bagasse.

[0014] Furthermore, the ternary deep eutectic solvent is obtained by weighing the choline chloride, oxalic acid, and lactic acid according to the molar ratio, mixing them, and heating and stirring in an oil bath at 80 - 90 °C.

[0015] Furthermore, the ternary deep eutectic solvent is composed of choline chloride, oxalic acid, and lactic acid with a molar ratio of 1∶(0.5 - 2)∶(1 - 2.5).

[0016] Furthermore, the ternary eutectic solvent is composed of choline chloride, oxalic acid and lactic acid with a molar ratio of 1∶0.5∶2.5; or, the ternary eutectic solvent is composed of choline chloride, oxalic acid and lactic acid with a molar ratio of 1∶1∶2;

[0017] or, the ternary eutectic solvent is composed of choline chloride, oxalic acid and lactic acid with a molar ratio of 1∶1.5∶1.5;

[0018] or, the ternary eutectic solvent is composed of choline chloride, oxalic acid and lactic acid with a molar ratio of 1∶2∶1.

[0019] Among them, the optimal composition is: the molar ratio of choline chloride, oxalic acid and lactic acid is 1∶1∶2.

[0020] The second technical solution of the present invention:

[0021] A lignin-containing bagasse fiber prepared by the above method.

[0022] Furthermore, the cellulose content in the lignin-containing bagasse fiber is 76wt%-81wt%, the lignin content is 8wt%-15wt%, and the crystallinity is 66%-69%.

[0023] If the lignin-containing bagasse fiber contains excessive lignin or low amounts of cellulose, it will have a negative impact on the mechanical properties of the cellulose-based material. Therefore, strictly controlling the lignin and cellulose in the lignin-containing bagasse fiber is crucial for improving the performance of the cellulose-based material.

[0024] The third technical solution of the present invention:

[0025] The application of the lignin-containing bagasse fiber in preparing an ultraviolet protection film and a moisture-resistant tensile film.

[0026] Compared with the prior art, the present invention has the following advantages and technical effects:

[0027] (1) By using ternary eutectic solvents with different ratios, the present invention realizes the preparation of lignin-containing bagasse fibers at a lower reaction temperature and normal pressure. The method of the present invention can selectively regulate the lignin content while causing less damage to the cellulose structure, which is beneficial to the separation of each component of the raw material and the high-value utilization of the raw material. In addition, the ternary eutectic solvent in the present invention is easy to prepare and has a low cost, belonging to a green solvent.

[0028] (2) The entire reaction process of the present invention is carried out at a lower temperature and lower pressure, with simple operation, and high-quality bagasse fibers with different lignin and cellulose contents can be extracted, which is convenient for subsequent research on the influence of the presence of different lignin contents on the properties of cellulose and the high-value utilization of bagasse fibers. Description of the Drawings

[0029] The accompanying drawings that form a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0030] Figure 1 is the microscopic morphology diagram of untreated raw bagasse;

[0031] Figure 2 is the microscopic morphology diagram of the pretreated bagasse prepared in step (1) of Example 1;

[0032] Figure 3 is the microscopic morphology diagram of the lignin-containing bagasse fiber prepared in Example 2;

[0033] Figure 4 is the microscopic morphology diagram of the lignin-containing bagasse fiber prepared in Example 3;

[0034] Figure 5 is the microscopic morphology diagram of the lignin-containing bagasse fiber prepared in Example 4;

[0035] Figure 6 is the microscopic morphology diagram of the lignin-containing bagasse fiber prepared in Comparative Example 1. Detailed Description of the Invention

[0036] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation to the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation manners of the present invention.

[0037] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0038] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0039] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the description of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of the present invention are obvious to those skilled in the art. The description and examples of the present invention are merely exemplary.

[0040] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0041] An embodiment of the present invention provides a method for preparing lignin-containing bagasse fibers based on a ternary deep eutectic solvent, comprising the following steps:

[0042] Mix and stir the pretreated bagasse with the ternary deep eutectic solvent (DES) for reaction, cool after the reaction is completed, wash after solid-liquid separation to obtain the lignin-containing bagasse fibers; the ternary deep eutectic solvent is composed of choline chloride (ChCl), oxalic acid (OA), and lactic acid (LA) with a molar ratio of 1∶(0-2)∶(1-3) (where the dosage of OA is not 0);

[0043] The temperature of the mixing and stirring reaction is 90-120°C and is carried out under normal pressure (101.325 kPa).

[0044] In a preferred embodiment of the present invention, the addition amount of the bagasse in the ternary deep eutectic solvent is 2.5 wt%.

[0045] In a preferred embodiment of the present invention, the pretreatment of the bagasse includes the following steps: Wash the bagasse with water to remove water-soluble impurities in the bagasse, dry it at 60°C for 24 h, then place it in a crusher for sufficient crushing, sieve it through an 80-100 mesh sieve after crushing, and dry the obtained bagasse powder at 60°C for 24 h again to obtain the pretreated bagasse, which is sealed in a sealed bag for storage for use.

[0046] In a preferred embodiment of the present invention, the ternary deep eutectic solvent is obtained by weighing the choline chloride, oxalic acid, and lactic acid according to the molar ratio, mixing them, and heating and stirring in an oil bath at 80-90°C. Specifically, it includes the following steps:

[0047] Add choline chloride, oxalic acid, and lactic acid to a beaker according to the molar ratio, heat and stir continuously in an oil bath at 80-90°C until a clear liquid is obtained, which is the ternary deep eutectic solvent.

[0048] In a preferred embodiment of the present invention, the ternary deep eutectic solvent is composed of choline chloride, oxalic acid, and lactic acid with a molar ratio of 1∶(0.5-2)∶(1-2.5); for example:

[0049] The ternary eutectic solvent is composed of choline chloride, oxalic acid and lactic acid with a molar ratio of 1:0.5:2.5; or

[0050] The ternary eutectic solvent is composed of choline chloride, oxalic acid and lactic acid with a molar ratio of 1:1:2; or

[0051] The ternary eutectic solvent is composed of choline chloride, oxalic acid and lactic acid with a molar ratio of 1:1.5:1.5; or

[0052] The ternary eutectic solvent is composed of choline chloride, oxalic acid and lactic acid with a molar ratio of 1:2:1.

[0053] An embodiment of the present invention also provides lignin-containing bagasse fibers prepared by the above method.

[0054] Furthermore, the cellulose content in the lignin-containing bagasse fibers is 76wt%-81wt%, the lignin content is 8wt%-15wt%, and the crystallinity is 66%-69%.

[0055] All raw materials used in the embodiments of the present invention are obtained by purchasing on the market.

[0056] The technical solution of the present invention will be further described below through examples.

[0057] Example 1

[0058] (1) Wash the bagasse (see the microscopic morphology diagram in Figure 1 ) with water to remove water-soluble impurities in the bagasse, dry it at 60°C for 24h, then place it in a crusher for sufficient crushing, sieve it through an 80-mesh sieve after crushing, and dry the obtained bagasse powder again at 60°C for 24h to obtain pretreated bagasse (see the microscopic morphology diagram in Figure 2 ), and pack it into a sealed bag for sealed storage for later use;

[0059] (2) Take choline chloride, oxalic acid and lactic acid according to a molar ratio of 1:0.5:2.5 and add them to a beaker, heat them in an oil bath at 80°C and stir continuously until a clear liquid is obtained, which is the ternary eutectic solvent;

[0060] (3) Place the ternary eutectic solvent obtained in step (2) in a container and stir while heating. When the temperature of the ternary eutectic solvent rises to 120°C, add the bagasse prepared in step (1) to the ternary eutectic solvent at a solid content of 2.5wt% under normal pressure and stir for reaction. After the reaction is completed, cool it, perform solid-liquid separation by suction filtration with a funnel, wash the obtained solid 10 times with ethanol, and then dry it at 60°C to obtain lignin-containing bagasse fibers.

[0061] Example 2

[0062] (1) Wash the bagasse with water to remove the water-soluble impurities in the bagasse. After drying at 60 °C for 24 h, place it in a crusher for sufficient pulverization. After pulverization, sieve it through a 100-mesh sieve. The obtained bagasse powder is dried again at 60 °C for 24 h to obtain the pretreated bagasse, which is then sealed in a sealed bag for storage for later use;

[0063] (2) Take choline chloride, oxalic acid, and lactic acid according to a molar ratio of 1:1:2 and add them to a beaker. Heat them in an oil bath at 80 °C and stir continuously until a clear liquid is obtained, which is the ternary deep eutectic solvent;

[0064] (3) Place the ternary deep eutectic solvent obtained in step (2) in a container and stir while heating. When the temperature of the ternary deep eutectic solvent rises to 110 °C, add the bagasse prepared in step (1) to the ternary deep eutectic solvent at a solid content of 2.5 wt% under atmospheric pressure and stir to react. After the reaction is completed, cool it, and perform solid-liquid separation by suction filtration with a funnel. Wash the obtained solid 10 times with ethanol, and then dry it at 60 °C to obtain lignin-containing bagasse fibers (see the microscopic morphology diagram in Figure 3 ).

[0065] Example 3

[0066] (1) Wash the bagasse with water to remove the water-soluble impurities in the bagasse. After drying at 60 °C for 24 h, place it in a crusher for sufficient pulverization. After pulverization, sieve it through a 100-mesh sieve. The obtained bagasse powder is dried again at 60 °C for 24 h to obtain the pretreated bagasse, which is then sealed in a sealed bag for storage for later use;

[0067] (2) Take choline chloride, oxalic acid, and lactic acid according to a molar ratio of 1:1.5:1.5 and add them to a beaker. Heat them in an oil bath at 80 °C and stir continuously until a clear liquid is obtained, which is the ternary deep eutectic solvent;

[0068] (3) Place the ternary deep eutectic solvent obtained in step (2) in a container and stir while heating. When the temperature of the ternary deep eutectic solvent rises to 110 °C, add the bagasse prepared in step (1) to the ternary deep eutectic solvent at a solid content of 2.5 wt% under atmospheric pressure and stir to react. After the reaction is completed, cool it, and perform solid-liquid separation by suction filtration with a funnel. Wash the obtained solid 10 times with ethanol, and then dry it at 60 °C to obtain lignin-containing bagasse fibers (see the microscopic morphology diagram in Figure 4 ).

[0069] Example 4

[0070] (1) Wash the bagasse with water to remove the water-soluble impurities in the bagasse. After drying at 60 °C for 24 h, place it in a crusher for sufficient pulverization. After pulverization, pass through a 100-mesh sieve. The obtained bagasse powder is dried again at 60 °C for 24 h to obtain the pretreated bagasse, which is packed into a sealed bag and stored sealed for use;

[0071] (2) Take choline chloride, oxalic acid and lactic acid according to a molar ratio of 1:2:1 and add them to a beaker. Heat in an oil bath at 80 °C and stir continuously until a clear liquid is obtained, which is the ternary deep eutectic solvent;

[0072] (3) Place the ternary deep eutectic solvent obtained in step (2) in a container and stir while heating. When the temperature of the ternary deep eutectic solvent rises to 110 °C, add the bagasse prepared in step (1) to the ternary deep eutectic solvent at a solid content of 2.5 wt% under normal pressure and stir for reaction. After the reaction is completed, cool, and perform solid-liquid separation by suction filtration with a funnel. Wash the obtained solid with ethanol 10 times, and then dry at 60 °C to obtain lignin-containing bagasse fibers (for the microscopic morphology diagram, see Figure 5 ).

[0073] Example 5

[0074] (1) Wash the bagasse with water to remove the water-soluble impurities in the bagasse. After drying at 60 °C for 24 h, place it in a crusher for sufficient pulverization. After pulverization, pass through a 90-mesh sieve. The obtained bagasse powder is dried again at 60 °C for 24 h to obtain the pretreated bagasse, which is packed into a sealed bag and stored sealed for use;

[0075] (2) Add choline chloride, oxalic acid and lactic acid to a beaker according to the molar ratio of Example 2. Heat in an oil bath at 90 °C and stir continuously until a clear liquid is obtained, which is the ternary deep eutectic solvent;

[0076] (3) Place the ternary deep eutectic solvent obtained in step (2) in a container and stir while heating. When the temperature of the ternary deep eutectic solvent rises to 90 °C, add the bagasse prepared in step (1) to the ternary deep eutectic solvent at a solid content of 2.5 wt% under normal pressure and stir for reaction. After the reaction is completed, cool, and perform solid-liquid separation by suction filtration with a funnel. Wash the obtained solid with ethanol 10 times, and then dry at 60 °C to obtain lignin-containing bagasse fibers.

[0077] Comparative Example 1

[0078] Same as Example 1, the only difference is that the deep eutectic solvent does not contain oxalic acid, and the specific steps are as follows:

[0079] (1) Wash the bagasse with water to remove the water-soluble impurities in the bagasse. After drying at 60 °C for 24 h, place it in a crusher for sufficient pulverization. After pulverization, sieve it through an 80-mesh sieve. Then dry the obtained bagasse powder again at 60 °C for 24 h to obtain the pretreated bagasse, and put it into a sealed bag for storage for later use;

[0080] (2) Take choline chloride, oxalic acid and lactic acid according to a molar ratio of 1:0:3 and add them to a beaker. Heat in an oil bath at 80 °C and stir continuously until a clear liquid is obtained, which is the deep eutectic solvent;

[0081] (3) Place the deep eutectic solvent obtained in step (2) in a container and stir while heating. When the temperature of the deep eutectic solvent rises to 90 °C, add the bagasse prepared in step (1) to the deep eutectic solvent according to a solid content of 2.5 wt% under normal pressure and stir to react. After the reaction is completed, cool it, and perform solid-liquid separation by suction filtration with a funnel. Wash the obtained solid with ethanol 10 times, and then dry it at 60 °C to obtain lignin-containing bagasse fibers (see the micrograph in Figure 6 ).

[0082] Comparative Example 2

[0083] Same as Example 1, the difference is only that the composition of the ternary deep eutectic solvent is different, and the specific steps are as follows:

[0084] (1) Wash the bagasse with water to remove the water-soluble impurities in the bagasse. After drying at 60 °C for 24 h, place it in a crusher for sufficient pulverization. After pulverization, sieve it through an 80-mesh sieve. Then dry the obtained bagasse powder again at 60 °C for 24 h to obtain the pretreated bagasse, and put it into a sealed bag for storage for later use;

[0085] (2) Take choline chloride, oxalic acid and lactic acid according to a molar ratio of 1:3:1 and add them to a beaker. Heat in an oil bath at 80 °C and stir continuously until a clear liquid is obtained, which is the ternary deep eutectic solvent;

[0086] (3) Place the ternary deep eutectic solvent obtained in step (2) in a container and stir while heating. When the temperature of the ternary deep eutectic solvent rises to 120 °C, add the bagasse prepared in step (1) to the ternary deep eutectic solvent according to a solid content of 2.5 wt% under normal pressure and stir to react. After the reaction is completed, cool it, and perform solid-liquid separation by suction filtration with a funnel. Wash the obtained solid with ethanol 10 times, and then dry it at 60 °C to obtain lignin-containing bagasse fibers.

[0087] Comparative Example 3

[0088] Same as Example 1, the difference is only that the composition of the deep eutectic solvent is different, and the specific steps are as follows:

[0089] (1) Wash the bagasse with water to remove the water-soluble impurities in the bagasse. After drying at 60 °C for 24 h, place it in a crusher for sufficient pulverization. After pulverization, sieve it through an 80-mesh sieve. The obtained bagasse powder is dried again at 60 °C for 24 h to obtain the pretreated bagasse, which is then sealed in a sealed bag for storage for later use;

[0090] (2) Take choline chloride, oxalic acid and lactic acid in a molar ratio of 1:0.5:0 and add them to a beaker. Heat in an oil bath at 80 °C and stir continuously until a clear liquid is obtained, which is the deep eutectic solvent;

[0091] (3) Place the deep eutectic solvent obtained in step (2) in a container and stir while heating. When the temperature of the deep eutectic solvent rises to 120 °C, add the bagasse prepared in step (1) to the deep eutectic solvent at a solid content of 2.5 wt% under normal pressure and stir to react. After the reaction is completed, cool it, and perform solid-liquid separation by suction filtration with a funnel. Wash the obtained solid with ethanol 10 times, and then dry it at 60 °C to obtain lignin-containing bagasse fibers.

[0092] Comparative Example 4

[0093] Same as Example 1, the difference is only that the composition of the ternary deep eutectic solvent is different, and the specific steps are as follows:

[0094] (1) Wash the bagasse with water to remove the water-soluble impurities in the bagasse. After drying at 60 °C for 24 h, place it in a crusher for sufficient pulverization. After pulverization, sieve it through an 80-mesh sieve. The obtained bagasse powder is dried again at 60 °C for 24 h to obtain the pretreated bagasse, which is then sealed in a sealed bag for storage for later use;

[0095] (2) Take choline chloride, oxalic acid and glycerol in a molar ratio of 1:0.5:2.5 and add them to a beaker. Heat in an oil bath at 80 °C and stir continuously until a clear liquid is obtained, which is the ternary deep eutectic solvent;

[0096] (3) Place the ternary deep eutectic solvent obtained in step (2) in a container and stir while heating. When the temperature of the ternary deep eutectic solvent rises to 120 °C, add the bagasse prepared in step (1) to the ternary deep eutectic solvent at a solid content of 2.5 wt% under normal pressure and stir to react. After the reaction is completed, cool it, and perform solid-liquid separation by suction filtration with a funnel. Wash the obtained solid with ethanol 10 times, and then dry it at 60 °C to obtain lignin-containing bagasse fibers.

[0097] Performance test

[0098] Comparison Figures 1 - 6 It can be seen that as the oxalic acid content increases, the average particle size of the bagasse fibers gradually decreases.

[0099] The lignin content of raw sugarcane bagasse and the residual solid bagasse fiber of DES-pretreated sugarcane bagasse was determined by the NREL measurement method. The cellulose content was determined by the nitric acid-ethanol method using the national standard GB / T 2677.10-1995. The cellulose, lignin content, and crystallinity of the pretreated sugarcane bagasse obtained in step (1) of Example 1 and the lignin-containing bagasse fibers obtained in Examples 1-5 and Comparative Examples 1-4 were measured, and the results are shown in Table 1.

[0100] Table 1 Performance test results of examples and comparative examples

[0101] Component Bagasse Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Cellulose wt% 51.12 71.80 80.93 80.83 77.29 76.56 Lignin wt% 23.23 16.51 9.77 8.75 11.35 14.45 Crystallinity % 56.15 63.64 67.41 67.55 68.39 66.35 Component Example 5 Comparative Example 2 Comparative Example 3 Comparative Example 4 Cellulose wt% 87.17 84.53 74.21 70.60 Lignin wt% 8.53 10.37 15.77 19.40 Crystallinity % 65.45 62.04 56.74 50.21

[0102] As can be seen from Table 1, with the increase in the oxalic acid ratio, the removal rate of lignin by the ternary eutectic solvent first increases and then decreases, the lignin content in the remaining solid crude fiber first decreases and then increases; the cellulose content first increases and then decreases, and the loss of hemicellulose changes little. The separation method of the present invention can rapidly, efficiently, and mildly regulate the lignin content in sugarcane bagasse cellulose, the main structure of cellulose is not damaged, the reaction conditions are mild, and the safety is high.

[0103] Application example

[0104] (1) The bagasse fibers prepared in Comparative Example 1 and Examples 1-4 were respectively dispersed in deionized water, placed in a high-pressure homogenizer for homogenization, and homogenized 5 times respectively at pressures of 200 MPa, 500 MPa, and 1000 MPa. A bagasse nanofibrillated cellulose aqueous solution with a concentration of 0.2 wt% was prepared. It was stored at -4°C.

[0105] (2) Take 300 mL of the above-prepared bagasse nanofibrillated cellulose aqueous solution, place a PTFE polytetrafluoroethylene filter membrane with a pore size of 0.22 μm on a sintered glass funnel, and after drying the water of the bagasse nanofibrillated cellulose aqueous solution on the sintered glass funnel, take it out to obtain an LCNF film, place it in a blast drying oven, and dry it at 35°C for 4 hours. The dried LCNF film was placed between two smooth steel plates and subjected to hot pressing treatment with a hot press. The temperature was set at 130°C, the pressure was 4 MPa, and the time was 3 hours to obtain a hot-pressed lignin-containing nanofibrillated cellulose film.

[0106] The mechanical properties of the film were measured with a universal tensile testing machine. The film specimen to be tested was cut into a size of 70 mm × 10 mm, the clamping distance was set at 30 mm, and the tensile rate during the test was 5 mm / min. Before the wet strength test, the sample needs to be soaked in deionized water for 15 min.

[0107] The transmittance of the film was measured with a UV-spectrophotometer, and the measurement results were corrected according to a thickness of 100 μm.

[0108] The wet tensile strength and ultraviolet light transmittance of the nanocellulose films prepared from the lignin-containing bagasse fibers obtained in Examples 1-4 and Comparative Example 1 were measured, and the results are shown in Table 2.

[0109] Table 2 Test results of the film properties of Examples 1-4 and Comparative Example 1

[0110]

[0111]

[0112] It can be seen from Table 2 that the bagasse fibers obtained by the method of the present invention have excellent wet tensile strength and ultraviolet-visible light transmittance. Therefore, it shows that the bagasse fibers of the present invention can be used in the preparation of ultraviolet protection films and anti-wet tensile films.

[0113] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for preparing lignin-containing bagasse fiber based on a ternary deep eutectic solvent, characterized in that: The following steps are involved: The pretreated bagasse is mixed with a ternary low eutectic solvent for stirring and reacting, and after the reaction is completed, the mixture is cooled, and the solid-liquid separation is followed by washing to obtain the lignin-containing bagasse fiber; the ternary low eutectic solvent is composed of choline chloride, oxalic acid and lactic acid in a molar ratio of 1:(0-2):(1-3), wherein the amount of oxalic acid is not 0; The mixing and stirring reaction is carried out at a temperature of 90-120° C. and is carried out under normal pressure.

2. The method for preparing lignin-containing bagasse fiber based on a ternary deep eutectic solvent according to claim 1, characterized in that: The amount of the pretreated bagasse added to the ternary deep eutectic solvent is 2.5 wt %.

3. The method for preparing lignin-containing bagasse fiber based on a ternary deep eutectic solvent according to claim 1, characterized in that: The pretreatment of bagasse comprises the following steps: washing the bagasse with water, drying, crushing and passing through a 80-100 mesh sieve, and drying the obtained bagasse powder again to obtain pretreated bagasse.

4. The method for preparing lignin-containing bagasse fiber based on a ternary deep eutectic solvent according to claim 1, characterized in that: The preparation method of the ternary deep eutectic solvent comprises the steps of weighing the choline chloride, oxalic acid and lactic acid in a molar ratio, mixing them, and heating and stirring them in an oil bath at 80-90° C.

5. The method for preparing lignin-containing bagasse fiber based on a ternary deep eutectic solvent according to claim 1, characterized in that: The ternary deep eutectic solvent consists of choline chloride, oxalic acid and lactic acid in a molar ratio of 1:(0.5-2):(1-2.5).

6. The method for preparing lignin-containing bagasse fiber based on a ternary deep eutectic solvent according to claim 5, characterized in that: The ternary deep eutectic solvent consists of choline chloride, oxalic acid and lactic acid in a molar ratio of 1:1:

2.

7. A lignin-containing bagasse fiber prepared by the method according to any one of claims 1 to 6.

8. The lignin-containing bagasse fiber according to claim 7, characterized in that: The cellulose content of the lignin-containing bagasse fiber is 76wt%-81wt%, the lignin content is 8wt%-15wt%, and the crystallinity is 66%-69%.

9. Use of the lignin-containing bagasse fiber according to any one of claims 7 to 8 in the preparation of ultraviolet protection films and moisture-resistant stretch films.

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