High-strength wood-based nanocellulose film and method for producing the same

Abstract

The application discloses a kind of high-strength wood nanocellulose film and preparation method thereof, belong to nanocellulose film technical field.The preparation method provided by the application includes the following steps: biomass straw is heated and treated by alkali liquor with concentration of 6-10wt%, after washing and neutralization, cellulase is added to carry out enzymolysis, after inactivation, mechanical pulping is carried out, and wheat straw biochemical mechanical pulp is obtained;The fine fiber is obtained by defibrating and screening the wheat straw biochemical mechanical pulp, the fine fiber is subjected to ultra-micro particle grinding, and the nanocellulose dispersion liquid containing lignin is obtained, vacuum filtration, and drying is obtained.The reaction condition is mild in the preparation process, the production cost is low, and the obtained nanocellulose film has higher mechanical strength, and the breaking stress can reach nearly 100MPa.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanocellulose film, in particular to a high-strength lignin-containing nanocellulose film and a preparation method thereof. BACKGROUND

[0002] The information disclosed in the background of the present application is only intended to increase the understanding of the overall background of the present application and should not necessarily be regarded as acknowledging or implying in any form that the information constitutes prior art known to those skilled in the art.

[0003] Nanocellulose film has good biodegradability and renewability, and is expected to replace non-degradable plastic film to some extent. High-strength nanocellulose film will have a more extensive application space. Nanocellulose film is mainly prepared from nanocellulose by vacuum filtration, electrospinning or solution spin coating method, etc. Therefore, the performance of nanocellulose film is closely related to the performance of nanocellulose.

[0004] At present, nanocellulose is generally produced by using dissolving pulp, bleached chemical pulp and the like with more delignification and higher cellulose content, which causes waste of resources to some extent. A large amount of waste liquid is generated in the process, which increases the production cost and has an impact on the ecological environment. It has been found that nanocellulose containing lignin not only retains the characteristics of nanocellulose, but also has good dispersity, hydrophobicity, ultraviolet resistance and thermal stability due to the presence of lignin.

[0005] At present, the raw material of nanocellulose film mainly comes from high-purity fibers of wood, and the raw material cost is high. Moreover, the wood needs to be crushed in the prior art, and the preparation cost is high, and it is more difficult to produce on a large scale. Biomass straw (such as wheat straw, rice straw, corn straw, etc.) as an agricultural byproduct has high renewability, can realize sustainable supply, and has lower cost. However, the cellulose content is low (usually less than 40%), and it is more difficult to use. At the same time, the performance of nanocellulose film obtained from the biomass straw as raw material is significantly affected by the preparation conditions, and it is difficult to obtain nanocellulose film with high strength.

[0006] Therefore, how to provide a method for preparing high-strength nanocellulose film containing lignin from biomass straw as raw material is a problem to be solved. SUMMARY

[0007] Therefore, the present application provides a high-strength lignin-containing nanocellulose film and a preparation method thereof. The method provided in the present application uses biomass straw as raw material, and nanocellulose containing lignin is prepared by enzyme / chemical / mechanical method. The high-strength lignin-containing nanocellulose film is prepared therefrom, and the production cost is low, which is suitable for large-scale application.

[0008] In a first aspect, the present application provides a method for preparing a high-strength lignin-containing nanocellulose film, comprising the following steps:

[0009] The biomass straw is treated by heating with an alkali solution with a concentration of 6-10 wt%, and after washing and neutralization, cellulase is added for enzymatic hydrolysis, and after inactivation, mechanical pulping is performed to obtain wheat straw biochemical mechanical pulp; the wheat straw biochemical mechanical pulp is defibrated and screened to obtain fine fibers, and the fine fibers are subjected to ultrafine particle grinding to obtain a lignin-containing nanocellulose dispersion liquid, which is vacuum filtered and dried.

[0010] Preferably, the alkali solution is an aqueous solution of NaOH or KOH.

[0011] Preferably, the mass ratio of the biomass straw to the alkali solution is 1:(4-8).

[0012] Preferably, the heating treatment temperature is 90-100°C, and the heating treatment time is 40-60 min.

[0013] Preferably, the amount of cellulase used is 15-25 U / g; the solution in the enzymatic hydrolysis process is a citric acid-sodium citrate buffer solution, and the pH is 4.8-5.2.

[0014] Preferably, the enzymatic hydrolysis temperature is 50-60°C, and the enzymatic hydrolysis time is 50-70 min; the inactivation temperature is 95-100°C, and the inactivation time is 8-15 min.

[0015] Preferably, the defibration and screening step further comprises a step of latent heat elimination of the wheat straw biochemical mechanical pulp, and the latent heat elimination time is 50-80 min.

[0016] Preferably, the diameter of the fine fibers is less than 0.15 mm.

[0017] Preferably, the concentration of the lignin-containing nanocellulose dispersion liquid is 0.8-1.5 wt%.

[0018] In a second aspect, the present application provides a high-strength lignin-containing nanocellulose film prepared by the above preparation method.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] (1) The present application uses biomass straw as raw material, and through enzymatic / chemical / mechanical method, a lignin-containing nanocellulose is prepared, and then through vacuum filtration method, a nanocellulose film is prepared, the preparation process has mild reaction conditions and low production cost, and high-value utilization of biomass straw can be realized, which is suitable for large-scale application.

[0021] (2) The nanocellulose film prepared by the method has good strength, the film breaking stress is above 45 MPa, and the highest can reach nearly 100 MPa, and the transparency is good (>80%), and can be applied in the field of food packaging, and has good application prospect. DETAILED DESCRIPTION

[0022] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0023] The application provides a preparation method of high-strength wood nanocellulose film, comprising the following steps:

[0024] The biomass straw is treated by heating with an alkali solution with a concentration of 6-10wt%, and after washing and neutralization, cellulase is added for enzymolysis, and after inactivation, mechanical pulping is performed to obtain wheat straw biochemical mechanical pulp; the wheat straw biochemical mechanical pulp is defibrated and screened to obtain fine fibers, and the fine fibers are subjected to ultra-micro particle grinding to obtain a nanocellulose dispersion liquid containing lignin, and vacuum filtration and drying are performed.

[0025] The application does not make special restrictions on the source of the biomass straw, which can be selected from wheat straw, corn straw or rice straw, etc., and in one or more embodiments of the application, the biomass straw is preferably wheat straw.

[0026] The application further comprises the steps of dust removal and washing of the straw before the alkali solution heating treatment step, and the dust removal and washing process are not specially restricted, and the methods commonly used in the art can be used.

[0027] In the application, the alkali solution is an aqueous solution of NaOH or KOH, and more preferably an aqueous solution of NaOH. The application first uses an alkali solution (to a certain extent, the wax layer on the surface of the straw is damaged, and a part of the lignin in the raw material is removed). It is found that the concentration of the alkali solution will affect the lignin content, particle size and other properties of the nanocellulose containing lignin, thereby affecting the mechanical strength of the final nanocellulose film. When the concentration of the alkali solution is too low, the mechanical strength of the obtained nanocellulose film is low; when the concentration of the alkali solution is increased, the degree of lignin dissolution is correspondingly increased, the adhesion of lignin to the fibers is weakened, and the strength of the corresponding film is also increased to a certain extent. However, too high concentration of the alkali solution does not significantly improve the mechanical properties, and also leads to too low lignin content, thereby causing the hydrophobicity, ultraviolet resistance and thermal stability of the obtained nanocellulose film to decrease.

[0028] In the present application, the mass ratio of the biomass straw to the alkali solution is 1:(4-8), and more preferably 1:(4-6). Too much alkali solution will not greatly improve the effect, but will increase the difficulty of waste liquid treatment.

[0029] In the present application, the heating treatment temperature is 90-100℃, and the heating treatment time is 40-60min.

[0030] In the present application, the cellulase is used in an amount of 15-25U / g; the solution in the enzymolysis process is a citric acid-sodium citrate buffer solution, and the pH is 4.8-5.2. After the cellulase treatment, the cellulose becomes softer and more suitable for chemical processing.

[0031] In the present application, the enzymolysis temperature is 50-60℃, and the enzymolysis time is 50-70min; the inactivation temperature is 95-100℃, and the inactivation time is 8-15min.

[0032] In the present application, the mechanical pulping process is not specially limited, and the present application preferably adopts a high-concentration disc refiner comprising two disc refiners with disc refiner gaps of 0.5mm and 0.15mm, respectively. The skilled in the art can also make adjustments according to actual needs.

[0033] In the present application, the step of defibrating and screening is further preceded by a step of latent elimination of the wheat straw biochemical mechanical pulp, and the latent elimination time is 50-80min. The latent elimination reduces the fiber bending degree, and the screening efficiency is higher.

[0034] In the present application, the diameter of the fine fibers is below 0.15mm. The present application does not specially limit the defibrating and screening process and equipment, and the fine fibers obtained through defibrating and screening can ensure the uniformity of microfibrillation during subsequent ultrafine particle grinding, and can reduce energy consumption and improve the yield of lignin-containing nanocellulose.

[0035] The present application does not specially limit the specific steps of ultrafine particle grinding, and the present application preferably performs microfibrillation treatment through an ultrafine particle grinder, the concentration is 0.8-1.5wt%, and the adjustment gaps are +2, 0, -2, -5, and -8, respectively, and the cycle number of each stage is 8-10 times. Finally, a lignin-containing nanocellulose dispersion liquid is obtained, and the concentration of the lignin-containing nanocellulose dispersion liquid is 0.8-1.5wt%.

[0036] The present application also provides a high-strength lignin-containing nanocellulose film prepared by the above preparation method. The film breaking stress is above 30MPa, and can be up to nearly 100MPa, and the transparency is above 80%, and the film can be applied in the field of food packaging and the like, and has a good application prospect.

[0037] The technical solutions of the present application will be further described below in combination with specific embodiments.

[0038] Example 1

[0039] The present embodiment provides a method for preparing a high-strength lignin-containing nanocellulose film.

[0040] (1) Take 500 g of absolutely dry wheat straw, remove dust, wash, and measure the moisture content;

[0041] (2) Perform alkali pretreatment (6 wt% NaOH aqueous solution) on the wheat straw in step (1), with a solid-liquid ratio of 1:5; the treatment temperature is 95°C, the treatment time is 50 min, and the treatment is accompanied by thorough kneading; after the treatment, wash until neutral, place in a sealed bag to balance the moisture for 8 h, and measure the moisture content;

[0042] (3) Perform cellulase treatment on the wheat straw obtained in step (2), with an enzyme dosage of 20 U / g, under water bath conditions for 60 min, with a treatment temperature of 55°C, and with a citric acid-sodium citrate buffer solution as the solution during the enzyme treatment, with a pH of 5; the treatment is accompanied by thorough kneading, and after the treatment, deactivate at 100°C for 10 min;

[0043] (4) Perform mechanical treatment on the wheat straw in step (3), using a high-concentration disc grinder to continuously grind at both ends, with a gap of 0.5 mm and 0.15 mm in the two sections, respectively, to obtain the wheat straw biochemical mechanical pulp;

[0044] (5) Place the wheat straw biochemical mechanical pulp in step (4) into a sealed bag, add a certain amount of water, and place the whole in a 60°C constant-temperature water bath kettle for 60 min;

[0045] (6) Disperse and screen the wheat straw biochemical mechanical pulp in step (5) through a flat-screen pulp machine, with a screen gap of 0.15 mm; obtain fine fibers with a diameter of less than 0.15 mm;

[0046] (7) Perform microfibrillation treatment on the fine fibers in step (6) through a super-micro particle grinding machine, with a feeding concentration of 1 wt%; adjust the gap to +2, 0, -2, -5, and -8, respectively, and the number of cycles in each stage is 10 times; finally obtain a lignin-containing nanocellulose dispersion liquid;

[0047] (8) Perform vacuum filtration on the lignin-containing nanocellulose dispersion liquid obtained in step (7) to obtain a nanocellulose film. The basis weight of the nanocellulose film is 60 g / m 2 , and the wet film is compacted, and dried in a 50°C oven for 24 h.

[0048] The wheat straw bio-chemi-mechanical pulp fiber obtained in the embodiment has an average length of 0.809±0.008 mm and an average width of 27.1±0.2 μm; the lignin content of the obtained nanocellulose is 17.85 wt%, the average particle size of the nanocellulose is 3.98±0.97 nm, and the crystallinity is 64.78%; the transparency of the obtained nanocellulose film is 83.00%, the maximum stress of the film when breaking is 48.19 MPa, and the temperature at the maximum pyrolysis rate is 345.14℃.

[0049] Example 2

[0050] The embodiment provides a preparation method of a high-strength wood nanocellulose film.

[0051] (1) 500 g of absolute dry wheat straw was weighed, dusted, washed, and the moisture content was measured;

[0052] (2) The wheat straw in step (1) was subjected to alkali pretreatment (8 wt% NaOH aqueous solution), and the solid-liquid ratio was 1:5; the treatment temperature was 95℃, the treatment time was 50 min, and the treatment was carried out by rubbing sufficiently during the treatment; after the treatment, the wheat straw was washed to neutral, and was placed in a sealed bag to balance the moisture for 8 h, and the moisture content was measured;

[0053] (3) The wheat straw obtained in step (2) was subjected to cellulase treatment, and the enzyme dosage was 20 U / g; the treatment was carried out in a water bath for 60 min, and the treatment temperature was 55℃; the solution in the enzyme hydrolysis process was a citric acid-sodium citrate buffer solution, and the pH was 5; the treatment was carried out by rubbing sufficiently during the treatment; and after the treatment, the enzyme was inactivated by water at 100℃ for 10 min;

[0054] (4) The wheat straw in step (3) was subjected to mechanical treatment, and was continuously grinded by a high-concentration disc grinder at both ends; the gaps of the two sections were 0.5 mm and 0.15 mm respectively; and the obtained wheat straw bio-chemi-mechanical pulp was dried;

[0055] (5) The wheat straw bio-chemi-mechanical pulp in step (4) was placed in a sealed bag, a certain amount of water was added, and the whole was placed in a 60℃ constant-temperature water bath; and the treatment was carried out for 60 min;

[0056] (6) The wheat straw bio-chemi-mechanical pulp in step (5) was defibrated and dispersed, and was screened by a flat screen pulp machine; the screen gap of the flat screen pulp machine was 0.15 mm; and fine fibers with a diameter of less than 0.15 mm were obtained;

[0057] (7) The fine fibers in step (6) were subjected to microfibrillation treatment by a super-micro particle grinding machine; the feeding concentration was 1 wt%; the adjustment gaps were +2, 0, -2, -5 and -8 respectively; the circulation number of each stage was 10 times; and finally, a nanocellulose dispersion liquid containing lignin was obtained;

[0058] (8) The nanocellulose dispersion liquid containing lignin obtained in step (7) is vacuum filtered to obtain a nanocellulose film. The nanocellulose film has a mass per unit area of 60 g / m2. 2 The wet film is compacted by weight and dried in an oven at 50 °C for 24 h.

[0059] The wheat straw bio-chemical mechanical pulp obtained in this example has an average fiber length of 0.883 ± 0.021 mm and an average fiber width of 25.7 ± 0.1 μm. The nanocellulose obtained has a lignin content of 15.76 wt%, an average particle size of 3.88 ± 0.86 nm, and a crystallinity of 66.30%. The nanocellulose film obtained has a transparency of 89.03%, a maximum stress of 93.99 MPa when the film breaks, and a temperature of 344.6 °C at which the pyrolysis rate is the maximum.

[0060] Example 3

[0061] The difference between this example and Example 1 is that the alkali pretreatment in step (2) of this example uses a 10 wt% NaOH aqueous solution.

[0062] The wheat straw bio-chemical mechanical pulp obtained in this example has an average fiber length of 0.901 ± 0.015 mm and an average fiber width of 23.2 ± 0.3 μm. The nanocellulose obtained has a lignin content of 13.07 wt%, an average particle size of 3.63 ± 0.7 nm, and a crystallinity of 67.25%. The nanocellulose film obtained has a transparency of 91.21%, a maximum stress of 99.66 MPa when the film breaks, and a temperature of 329.16 °C at which the pyrolysis rate is the maximum.

[0063] Comparative Example 1

[0064] The difference between this comparative example and Example 1 is that the alkali pretreatment in step (2) of this comparative example uses a 2 wt% NaOH aqueous solution.

[0065] The wheat straw bio-chemical mechanical pulp obtained in this comparative example has an average fiber length of 0.699 ± 0.011 mm and an average fiber width of 29.9 ± 0.1 μm. The nanocellulose obtained has a lignin content of 21.70 wt%, an average particle size of 4.30 ± 1.03 nm, and a crystallinity of 56.92%. The nanocellulose film obtained has a transparency of 15.8%, a maximum stress of 26.56 MPa when the film breaks, and a temperature of 350.65 °C at which the pyrolysis rate is the maximum.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Example 1 is that the alkali pretreatment in step (2) of this comparative example uses a 4 wt% NaOH aqueous solution.

[0068] The wheat straw bio-chemi-mechanical pulp obtained in the present comparative example has an average fiber length of 0.758 ± 0.015 mm, an average fiber width of 30.1 ± 0.2 μm, a lignin content of 19.17 wt% in the obtained nanocellulose, an average particle size of 3.22 ± 0.8 nm, and a crystallinity of 59.25%. The obtained nanocellulose film has a transparency of 21.02%, a maximum stress of 29.30 MPa when the film is broken, and a temperature of 348.86 °C at which the pyrolysis rate is the maximum.

[0069] Comparative Example 3

[0070] The present comparative example differs from Example 1 in that the present comparative example does not perform the cellulase treatment step of step (3). The specific steps are as follows:

[0071] (1) 500 g of absolute dry wheat straw was weighed, dusted, washed, and the moisture content was measured;

[0072] (2) The wheat straw of step (1) was subjected to alkali pretreatment (6 wt% NaOH aqueous solution) at a solid-to-liquid ratio of 1:5, a treatment temperature of 95 °C, and a treatment time of 50 min, with sufficient kneading during the treatment. After the treatment, the wheat straw was washed to neutral, and the moisture content was measured after the wheat straw was equilibrated in a sealed bag for 8 h;

[0073] (3) The wheat straw of step (3) was subjected to mechanical treatment by using a high-concentration disk mill to continuously grind the pulp at both ends, with a gap of 0.5 mm and 0.15 mm in the two sections, respectively, to obtain the wheat straw bio-chemi-mechanical pulp;

[0074] (4) The wheat straw bio-chemi-mechanical pulp of step (4) was placed in a sealed bag, and a certain amount of water was added. The whole was placed in a 60 °C constant-temperature water bath, and was allowed to stand for 60 min;

[0075] (5) The wheat straw bio-chemi-mechanical pulp of step (5) was subjected to microfibrillation treatment by using a super-micro particle grinding machine, with an inlet concentration of 1 wt%, and a gap adjustment of +2, 0, -2, -5, and -8, respectively, and a cycle number of 10 times in each stage, to obtain a lignin-containing nanocellulose dispersion;

[0076] (6) The lignin-containing nanocellulose dispersion obtained in step (6) was subjected to vacuum filtration to obtain a nanocellulose film. The basis weight of the nanocellulose film was 60 g / m 2 , and the wet film was compacted by weight, and was dried in a 50 °C oven for 24 h.

[0077] The wheat straw bio-chemi-mechanical pulp fiber obtained in the present comparative example has an average length of 0.810 ± 0.004 mm and an average width of 29.1 ± 0.1 μm. The lignin content of the obtained nanocellulose is 17.05 wt%, the average particle size of the nanocellulose is 4.03 ± 0.9 nm, and the crystallinity is 62.52%. The transparency of the obtained nanocellulose film is 81.50%, the maximum stress of the film when it breaks is 39.20 MPa, and the temperature at the maximum pyrolysis rate is 345.15 °C.

[0078] Comparative Example 4

[0079] The present comparative example differs from Example 1 in that the present comparative example does not perform the defibrillation and screening step of step (6). The specific steps are as follows:

[0080] (1) 500 g of absolutely dry wheat straw was weighed, dusted, washed, and the moisture content was measured;

[0081] (2) The wheat straw of step (1) was subjected to alkali pretreatment (6 wt% NaOH aqueous solution) with a solid-liquid ratio of 1:5; the treatment temperature was 95 °C, the treatment time was 50 min, and the straw was kneaded thoroughly during the treatment. After the treatment, the straw was washed to neutral, and the moisture content was measured after the straw was equilibrated in a sealed bag for 8 h;

[0082] (3) The wheat straw obtained in step (2) was subjected to cellulase treatment, and the enzyme dosage was 20 U / g. The treatment was performed in a water bath for 60 min at a temperature of 55 °C. The solution during the enzyme treatment was a citric acid-sodium citrate buffer solution, and the pH was 5. The straw was kneaded thoroughly during the treatment, and the enzyme was inactivated by water at 100 °C for 10 min after the treatment;

[0083] (4) The wheat straw of step (3) was subjected to mechanical treatment, and a high-concentration disc refiner was used to continuously grind the straw at both ends. The gaps of the two sections were 0.5 mm and 0.15 mm, respectively. The obtained wheat straw bio-chemi-mechanical pulp was dewatered;

[0084] (5) The wheat straw bio-chemi-mechanical pulp of step (4) was placed in a sealed bag, and a certain amount of water was added. The whole was placed in a constant-temperature water bath at 60 °C for 60 min;

[0085] (6) The wheat straw bio-chemi-mechanical pulp of step (5) was subjected to microfibrillation treatment by a super-micro particle grinding machine. The feeding concentration was 1 wt%, and the adjustment gaps were +2, 0, -2, -5, and -8, respectively. The number of cycles in each stage was 10. Finally, a nanocellulose dispersion liquid containing lignin was obtained;

[0086] (7) The nanocellulose dispersion liquid containing lignin obtained in step (6) was subjected to vacuum filtration to obtain a nanocellulose film. The basis weight of the nanocellulose film was 60 g / m 2The wet film was compacted by weight, and dried in an oven at 50°C for 24h.

[0087] The wheat straw bio-chemical mechanical pulp fibers obtained by the present comparative example had an average length of 0.776±0.004mm and an average width of 23.7±0.1μm. The lignin content of the obtained nanocellulose was 17.65wt%, the average particle size of the nanocellulose was 4.12±1.89nm, and the crystallinity was 63.72%. The transparency of the obtained nanocellulose film was 82.89%, the maximum stress of the film when it broke was 36.22MPa, and the temperature at the maximum pyrolysis rate was 346.30°C.

[0088] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Various modifications and changes can be made by those skilled in the art based on the principles and spirit of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a high-strength wood-based cellulose nanofiber membrane, characterized in that, Includes the following steps: Biomass straw is heated with an 8-10 wt% alkaline solution, washed and neutralized, then enzymatically hydrolyzed with cellulase, inactivated, and mechanically milled to obtain wheat straw biochemical mechanical pulp; the wheat straw biochemical mechanical pulp is decomposed and sieved to obtain fine fibers, the fine fibers are then ground into ultrafine particles to obtain a lignin-containing nanocellulose dispersion, which is then vacuum filtered and dried to obtain the final product. The amount of cellulase used is 15~25 U / g; The alkaline solution is an aqueous solution of NaOH; The mass ratio of biomass straw to alkaline solution is 1:(4~8); The high-strength wood-based nanocellulose membrane has a tensile stress of over 45 MPa and a transparency of over 80%.

2. The preparation method according to claim 1, characterized in that, The heat treatment temperature is 90~100℃, and the heat treatment time is 40~60min.

3. The preparation method according to claim 1, characterized in that, The solution used in the enzymatic hydrolysis step is a citric acid-sodium citrate buffer solution with a pH of 4.8-5.

2.

4. The preparation method according to claim 1, characterized in that, The enzymatic hydrolysis temperature is 50~60℃, and the enzymatic hydrolysis time is 50~70min; the inactivation temperature is 95~100℃, and the inactivation time is 8~15min.

5. The preparation method according to claim 1, characterized in that, Before the sieving and screening step, the step of removing the fumed straw biochemical mechanical pulp is also included, with a fumed time of 50-80 minutes.

6. The preparation method according to claim 1, characterized in that, The diameter of the fine fibers is less than 0.15 mm.

7. The preparation method according to claim 1, characterized in that, The concentration of the lignin-containing nanocellulose dispersion is 0.8~1.5wt%.

8. The high-strength wood-based cellulose nanofilm prepared by the preparation method according to any one of claims 1 to 7.