Bamboo fiber-based food fresh-keeping packaging paper and preparation method thereof

Abstract

The invention relates to bamboo fiber-based food fresh-keeping packaging paper and a preparation method thereof. The preparation method of the bamboo fiber-based food fresh-keeping packaging paper comprises the following steps: respectively grinding bleached sulfate tender moso bamboo fibers and moso bamboo root fibers, and dispersing and mixing to obtain NBF / BRF mixed pulp; then adding the modified moso bamboo cellulose nanocrystals to obtain NBF / BRF / BNC composite slurry; making paper with pulp, forming, dehydrating and drying to obtain a bamboo paper sample A, uniformly spraying bamboo vinegar on the outer surface of the bamboo paper sample A, and finally performing hot pressing and drying to obtain the bamboo fiber-based food fresh-keeping packaging paper. Bamboo fiber raw materials with different characteristics are used for preparing the packaging paper for food preservation, the bamboo fiber-based food packaging paper is endowed with excellent mechanical strength, barrier property, hydrophobic property and antibacterial and mildew-proof capabilities, and the bamboo fiber-based food packaging paper can be used in the field of packaging materials for fruit and vegetable preservation.

Description

Technical Field

[0001] The invention relates to the technical field of food fresh-keeping packaging materials, and in particular to a bamboo fiber-based food fresh-keeping packaging paper and a preparation method thereof. Background Art

[0002] Bamboo is a fast-growing plant that can mature and grow again in a short period of time, which allows it to quickly supplement and replace the use of plastics, thereby reducing dependence on plastics and oil. In addition, bamboo can absorb a large amount of carbon dioxide during its growth process and can be completely biodegraded after use, without causing long-term pollution to the environment, making bamboo products have less impact on the environment during use. More importantly, China has abundant bamboo resources, which are widely distributed and planted in a large area, providing sufficient raw material guarantee for the "bamboo instead of plastic" industry. In addition, the planting and processing costs of bamboo are relatively low, which is conducive to reducing costs and improving economic benefits. In addition, bamboo has excellent plasticity and hardness, and can be made into raw bamboo packaging, bamboo woven products, and bamboo fiber packaging, etc., which can replace some plastic products. Therefore, replacing plastic with bamboo not only helps to reduce plastic pollution and respond to climate change, but also promotes the development of green industries and improves economic benefits. It is an environmentally friendly and sustainable development option.

[0003] Bamboo fiber is cellulose fiber extracted from naturally grown bamboo. Bamboo fiber itself has good air permeability, water absorption, strong wear resistance and good dyeability, and has natural antibacterial, antibacterial, mite removal and deodorization functions. Bamboo fiber-based packaging paper is receiving widespread attention from packaging companies, and various research institutes are also trying to use bamboo fiber to prepare packaging paper. However, there is little research and application of bamboo fiber packaging paper for food preservation. Therefore, how to develop a new type of bamboo fiber-based food preservation packaging paper is an urgent problem that needs to be solved. Summary of the invention

[0004] In view of the technical problems existing in the prior art, the first object of the present invention is to provide a method for preparing bamboo fiber-based food fresh-keeping packaging paper.

[0005] The second object of the present invention is to provide bamboo fiber-based food fresh-keeping packaging paper obtained by the above preparation method.

[0006] The third object of the present invention is to provide the application of the above-mentioned bamboo fiber-based food fresh-keeping packaging paper.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for preparing bamboo fiber-based food fresh-keeping packaging paper comprises the following steps:

[0009] (1) bleached sulfate tender bamboo fiber and bamboo root fiber are respectively subjected to pulping treatment to obtain NBF pulp with a beating degree of 35-40°SR and BRF pulp with a beating degree of 45-50°SR;

[0010] (2) dispersing the NBF slurry and the BRF slurry in step (1) to obtain NBF dispersion and BRF dispersion;

[0011] (3) uniformly mixing the NBF dispersion and the BRF dispersion in step (2) to obtain a NBF / BRF mixed slurry;

[0012] (4) adding the modified bamboo cellulose nanocrystals to the NBF / BRF mixed slurry obtained in step (3) under stirring conditions, mixing evenly, and obtaining a NBF / BRF / BNC composite slurry;

[0013] (5) papermaking, shaping, dehydrating, and drying the NBF / BRF / BNC composite slurry described in step (4) to obtain a bamboo paper sample A;

[0014] (6) In step (5), the outer surface of the bamboo paper sample A is evenly sprayed with bamboo vinegar, and dried to obtain a bamboo paper sample B;

[0015] (7) The bamboo paper sample B described in step (6) is subjected to heat pressing and drying to obtain a bamboo fiber-based food fresh-keeping packaging paper.

[0016] Preferably, the bleached sulfate tender bamboo fiber in step (1) has a length of 2 to 20 mm and a diameter of 10 to 25 μm; the length of the bamboo root fiber has a length of 5 to 30 mm and a diameter of 28 to 40 μm.

[0017] Preferably, the mass ratio of the bleached sulfate tender bamboo fiber to the bamboo root fiber in step (1) is 5:5 to 7:3.

[0018] Preferably, the young bamboo in step (1) is one-year-old young bamboo.

[0019] Preferably, the refining process in step (1) is performed using a double-disc refiner;

[0020] Preferably, the amount of the modified bamboo fiber nanocrystals added in step (4) is 4.0-7.0% of the mass of the NBF / BRF / BNC composite slurry.

[0021] Preferably, the slurry concentration of the NBF / BRF / BNC composite slurry in step (4) is 0.2-1.0% by mass.

[0022] Preferably, the concentration of the bamboo vinegar in step (6) is 3.5-5.0% by mass.

[0023] Preferably, the amount of bamboo vinegar sprayed on the outer surface of the bamboo paper sample A in step (6) is 2.0 to 5.0 g / m 2 .

[0024] Preferably, the pulping treatment conditions of the bleached sulfate tender bamboo fiber described in step (1) are: the pulping speed is 500-750r / min, and the pulping concentration is 4.0-5.0wt%; the pulping treatment conditions of the bamboo root fiber are: the pulping speed is 600-980r / min, and the pulping concentration is 2.5-3.5wt%.

[0025] Preferably, the stirring speed in step (4) is 4000-7000 r / min.

[0026] Preferably, the stirring in step (4) is carried out using an electric stirrer.

[0027] Preferably, the modified bamboo cellulose nanocrystals in step (4) have a length of 50 to 200 nm and a diameter of 2 to 30 nm; the modified bamboo cellulose nanocrystals are prepared by the following method: bleached sulfate bamboo pulp is hydrolyzed with organic acid, dialyzed, centrifuged, and then acetylated to obtain modified bamboo cellulose nanocrystals.

[0028] Preferably, the modified bamboo cellulose nanocrystals are prepared by the following method: 3.0-4.0 g of bleached kraft softwood pulp is slowly added to 50-70 mL of a 55-60% maleic acid solution, and stirred and hydrolyzed in a water bath at 45-50° C. for 45-50 minutes, and then the acid hydrolysis reaction is terminated by adding deionized water, and the solid is washed by centrifugation for multiple times to purify, and finally the purified solid is dialyzed, and centrifuged again to obtain a light blue solution, and concentrated by rotary evaporation to obtain bamboo cellulose nanocrystal water suspensions of different concentrations, and freeze-dried in a freeze drying oven for 48-72 hours to obtain bamboo cellulose nanocrystals of different concentrations. 5-10 g of bamboo cellulose nanocrystals are placed in a flask containing 50-80 mL of glacial acetic acid, the temperature is raised to 50-60° C., 10-20 mL of acetic anhydride reagent and 500 μL of dicyclohexylcarbodiimide are added respectively, and after reacting for 60-80 min, the precipitate is poured into ethanol to precipitate a white flocculent precipitate, which is then centrifuged, and then washed with ethanol for 3-5 times, and then washed with deionized water for 2-3 times by centrifugation, and finally an acetylated bamboo cellulose nanocrystal water suspension is obtained, which is placed in a freeze drying box for freeze drying for 48-72 h to obtain acetylated bamboo cellulose nanocrystals.

[0029] Preferably, the papermaking process in step (5) is carried out using an inclined mesh paper machine.

[0030] Preferably, the bamboo vinegar liquid in step (5) is sprayed on the upper surface and the lower surface of the bamboo paper sample A.

[0031] Preferably, the drying method in step (6) is: infrared drying at 100-180° C. for 30-50 min.

[0032] Preferably, the hot pressing conditions in step (7) are: temperature of 88-98° C., pressure of 28-36 MPa, and time of 15-30 min.

[0033] Preferably, the drying method in step (7) is: infrared drying at 82-90° C. for 10-20 min.

[0034] A bamboo fiber-based food fresh-keeping packaging paper is obtained by the preparation method.

[0035] The performance indicators of the bamboo fiber-based food fresh-keeping packaging paper are as follows: Basis weight: 54-60g / m 2 ;Tensile strength: 2.95~3.48kN / m;Tear strength: 658.4~737.2mN;Oxygen permeability: 446~523cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 118~157g / m 2 day; water contact angle: 106~128°; Cobb water absorption value: 6.7~13.5g / m 2 ; Antibacterial rate: 90~96%; Mildew resistance level is Level Ⅰ.

[0036] Application of the bamboo fiber-based food fresh-keeping packaging paper in food fresh-keeping packaging materials.

[0037] Preferably, the food fresh-keeping packaging material is a fresh-keeping packaging material used for packaging fruits and vegetables.

[0038] Preferably, the fruits and vegetables include apricots, lychees, strawberries, tomatoes and bamboo shoots.

[0039] The present invention has the following advantages:

[0040] 1. The present invention adopts moso bamboo as the basic raw material. Moso bamboo is a large bamboo material with the advantages of fast growth rate, wide distribution range, excellent fiber quality, strong regeneration ability, etc. The food preservation packaging paper prepared from different raw materials such as bamboo fiber, bamboo root, bamboo nanocellulose, bamboo vinegar liquid, etc. on the same bamboo can be naturally biodegraded, belongs to environmentally friendly packaging materials, can realize the use of bamboo instead of plastic in the field of food preservation packaging materials, and meets the dual carbon development goals.

[0041] 2. The bamboo fiber-based food fresh-keeping packaging paper prepared by the present invention is prepared by a reasonable compounding of two types of fiber raw materials on bamboo, making full use of the advantages of bamboo fibers in different parts of bamboo: bamboo root fibers are long and strong, which can significantly improve the physical strength of bamboo-based packaging paper; tender bamboo trunk fibers are delicate and soft, with good fiber morphology, which can ensure close bonding between fibers; in addition, bamboo fibers contain substances such as flavonoids and wax, have good air permeability and wear resistance, and have natural antibacterial, mite-removing, and deodorizing effects. Bamboo vinegar is a byproduct obtained by pyrolysis of bamboo, which is a liquid (pH value 2.5-3) made by burning bamboo for more than 5 years, containing organic acids, alcohols, phenols, esters and trace alkaline components, etc., and has the characteristics of mildew resistance, antibacterial, antioxidant, deodorizing and peculiar smell, which are all conducive to improving the food fresh-keeping effect of packaging paper, wherein, the esters in bamboo vinegar can also assist in improving the hydrophobic effect.

[0042] 3. The present invention adopts the method of adding nano-sized modified bamboo cellulose nanocrystals into the slurry, and the acetylated bamboo cellulose nanocrystals can not only be used as paper reinforcing fillers, but also have good moisture-proof and water-blocking effects. Acetylation improves the hydrophobicity, thermal stability and chemical stability of nanocellulose, while retaining its original biocompatibility and nano-size advantages. Acetylation modification can change the properties and surface characteristics of nanocellulose, so that BNC can form strong covalent bonds and hydrogen bonds with the hydroxyl groups on the surface of bamboo cellulose, which can increase the mechanical strength of the wrapping paper, improve the pore structure of the wrapping paper, and increase the barrier capacity. The addition of bamboo nanocellulose is conducive to improving the interface bonding between bamboo fibers, so that the wrapping paper exhibits good mechanical strength and barrier properties.

[0043] 4. The bamboo fiber, bamboo root fiber, bamboo nanocellulose and bamboo vinegar used in the present invention are all derived from moso bamboo, realizing the utilization of all components of a bamboo. The prepared bamboo fiber-based food fresh-keeping packaging paper has good mechanical properties, barrier properties, hydrophobic properties and antibacterial properties, and can be used in the field of food fresh-keeping packaging materials. It will promote the high-quality development of the bamboo industry and realize the high-value utilization of bamboo instead of plastic in the field of food packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The invention is a schematic flow chart of a method for preparing the bamboo fiber-based food fresh-keeping packaging paper.

[0045] Figure 2 The invention discloses a bamboo fiber-based food fresh-keeping packaging paper.

[0046] Figure 3 It is a surface scanning electron microscope image of the bamboo fiber-based food fresh-keeping packaging paper obtained in Example 1 of the present invention.

[0047] Among them, 1 is a bamboo paper base, and 2 is a bamboo vinegar coating. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. The test methods for which specific experimental conditions are not specified in the following examples are usually in accordance with conventional experimental conditions. Unless otherwise specified, the reagents and raw materials used in the present invention can be obtained commercially.

[0049] 1. The bleached sulfate tender bamboo fiber (NBF) involved in the embodiments and comparative examples of the present invention was obtained from the State Key Laboratory of Pulp and Paper Engineering, with a length of 2 to 20 mm and a diameter of 10 to 25 μm; the bamboo root fiber (BRF) was obtained from the State Key Laboratory of Pulp and Paper Engineering, with a length of 5 to 30 mm and a diameter of 28 to 40 μm. Bamboo vinegar was purchased from Shijiazhuang Hongsen Activated Carbon Co., Ltd. with a concentration of 20%.

[0050] 2. The modified bamboo cellulose nanocrystals (BNC) involved in the embodiments of the present invention and the comparative examples are prepared from bleached sulfate bamboo pulp by organic acid hydrolysis, dialysis, centrifugation, and acetylation modification. Specifically, 50-70 mL of a 55-60% maleic acid solution is placed in a water bath (water bath temperature: 45-50° C.). Accurately weigh 3.0-4.0 g of bleached sulfate softwood pulp and slowly add it to the 55-60% maleic acid solution, stirring and hydrolyzing for 45-50 min at 45-50° C. Add 10-15 times the volume of deionized water of the above reaction system to terminate the acid hydrolysis reaction. Then, a centrifugal separation method is used to wash the solids, the upper solution is removed, and the solid sediment in the lower layer continues to be washed with water, and this centrifugal washing process is repeated several times until the upper solution becomes turbid. The solid matter in the lower layer is collected, placed in a dialysis bag and placed in clean water for dialysis. Finally, the solid and liquid in the dialysis bag are centrifuged again to collect the upper light blue solution. After rotary evaporation and concentration, acetylated bamboo cellulose nanocrystal water suspensions of different concentrations can be obtained for later use. The suspensions are placed in a freeze drying oven for freeze drying for 48 to 72 hours to obtain bamboo cellulose nanocrystals. Among them, organic acids have mild properties and can be recycled and reused. 5-10 g of bamboo cellulose nanocrystals are placed in a flask containing 50-80 mL of glacial acetic acid, the temperature is raised to 50-60° C., 10-20 mL of acetic anhydride reagent and 500 μL of dicyclohexylcarbodiimide are added respectively, and after reacting for 60-80 minutes, the precipitate is poured into ethanol to precipitate a white flocculent precipitate, which is then centrifuged and then washed with ethanol for 3-5 times, and then washed with deionized water by centrifugation for 2-3 times to finally obtain an acetylated bamboo cellulose nanocrystal water suspension, which is placed in a freeze drying oven for freeze drying for 48-72 hours to obtain acetylated bamboo cellulose nanocrystals.

[0051] 3. The detection of various parameters involved in the embodiments of the present invention is carried out according to national standard detection methods and industry standards, specifically:

[0052] ①Quantitative (GB / T 451.2-2002);

[0053] ②Tensile strength (GB / T 453-2002);

[0054] ③Tear strength (GB / T 455-2002);

[0055] ④Oxygen permeability (GB / T 19789-2005);

[0056] ⑤ Water vapor transmission rate (GB / T 22921-2008);

[0057] ⑥ Water contact angle (GB / T 30447-2013);

[0058] ⑦Cobb water absorption value (GB / T 1540-2002). The lower the Cobb water absorption value, the better the water resistance of the paper;

[0059] ⑧Inhibition rate (GB15979-2002), the colonies selected were Staphylococcus aureus (ATCC29213) and Escherichia coli (ATCC8099), both purchased from Shanghai Collection Biotechnology Center;

[0060] ⑨ Mildew resistance grade test (GB / T 4768-2008), mildew resistance grades are divided into four grades: Ⅰ, Ⅱ, Ⅲ, and Ⅳ. The order of mildew resistance is: grade Ⅰ> grade Ⅱ> grade Ⅲ> grade Ⅳ.

[0061] Figure 1 The preparation process of the bamboo fiber barrier packaging paper of the present invention is shown, specifically, pulping treatment: bleached sulfate tender bamboo fiber and bamboo root fiber are respectively pulped to obtain NBF pulp and BRF pulp; dispersion treatment: NBF pulp and BRF pulp are dispersed to obtain NBF dispersion liquid and BRF dispersion liquid; uniform mixing: NBF dispersion liquid and the BRF dispersion liquid are uniformly mixed to obtain NBF / BRF mixed pulp; stirring and mixing: modified bamboo cellulose nanocrystals are added to the NBF / BRF mixed pulp under stirring conditions, and mixed uniformly to obtain NBF / BRF / BNC composite pulp; papermaking, molding, dehydration and drying: NBF / BRF / BNC composite pulp is papermade, molded, dehydrated, and dried to obtain bamboo paper sample A; surface spraying: bamboo vinegar liquid is uniformly sprayed on the outer surface of bamboo paper sample A, and dried to obtain bamboo paper sample B, wherein, as Figure 2As shown, bamboo vinegar is evenly sprayed on the upper and lower surfaces of bamboo paper sample A; hot pressing and drying: bamboo paper sample B is hot pressed and dried to obtain bamboo fiber-based food fresh-keeping packaging paper.

[0062] Example 1

[0063] This embodiment provides a method for preparing bamboo fiber-based food fresh-keeping packaging paper, and the specific preparation steps are as follows:

[0064] (1) Bleached sulfate young bamboo fiber (NBF, length 2-20 mm, diameter 10-25 μm) was refined in a double-disc refiner at a refining speed of 500 r / min and a refining concentration of 4.0 wt% to obtain NBF pulp with a beating degree SR of 35°; and bamboo root fiber (BRF, length 5-30 mm, diameter 28-40 μm) was refined in a double-disc refiner at a refining speed of 600 r / min and a refining concentration of 2.5 wt% to obtain BRF pulp with a beating degree SR of 45°.

[0065] (2) The NBF slurry and the BRF slurry are dispersed to obtain a NBF dispersion and a BRF dispersion.

[0066] (3) The NBF dispersion and the BRF dispersion were mixed evenly at an absolute dry mass ratio of 5:5 (i.e., the mass ratio of bleached sulfate tender bamboo fiber to bamboo root fiber) to obtain a NBF / BRF mixed slurry.

[0067] (4) Add modified bamboo cellulose nanocrystals (BNC, length 50-200 nm, diameter 2-30 nm) to the NBF / BRF mixed slurry under stirring (rotation speed 4000 r / min), the amount of modified bamboo fiber nanocrystals added is 4.0% of the absolute dry mass of the NBF / BRF / BNC composite slurry, mix evenly, and obtain NBF / BRF / BNC composite slurry.

[0068] (5) The NBF / BRF / BNC composite pulp was formed on an inclined wire paper machine at a pulp mass concentration of 0.2%, and then dehydrated and dried to obtain bamboo paper sample A.

[0069] (6) The upper and lower surfaces of bamboo paper sample A are evenly sprayed with bamboo vinegar liquid with a mass concentration of 3.5% and a spraying amount of 2.0 g / m 2 , and then use an electric infrared generator to infrared dry the paper sample at 100°C for 30 minutes to obtain bamboo paper sample B.

[0070] (7) Bamboo paper sample B was subjected to hot pressing treatment at a temperature of 88°C and a pressure of 28 MPa for 15 min, and then infrared drying was performed at 82°C for 10 min to obtain bamboo fiber-based food fresh-keeping packaging paper.

[0071] The cross-sectional scanning electron microscope image of the bamboo fiber-based food fresh-keeping packaging paper prepared in this embodiment is as follows: Figure 3 As shown, the performance indicators of the bamboo fiber-based food fresh-keeping packaging paper are as follows: Basis weight: 54g / m 2 ;Tensile strength: 2.95kN / m;Tear strength: 658.4mN;Oxygen permeability: 523cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 157g / m 2 ·day; Water contact angle: 106°; Cobb water absorption value: 13.5g / m 2 ; Antibacterial rate: 90%; Anti-mildew grade is Grade Ⅰ.

[0072] Example 2

[0073] This embodiment provides a method for preparing bamboo fiber-based food fresh-keeping packaging paper, and the specific preparation steps are as follows:

[0074] (1) Bleached sulfate young bamboo fiber (NBF, length 2-20 mm, diameter 10-25 μm) was refined in a double-disc refiner at a refining speed of 600 r / min and a refining concentration of 4.4 wt% to obtain NBF pulp with a beating degree SR of 37°; and bamboo root fiber (BRF, length 5-30 mm, diameter 28-40 μm) was refined in a double-disc refiner at a refining speed of 750 r / min and a refining concentration of 2.8 wt% to obtain BRF pulp with a beating degree SR of 47°.

[0075] (2) The NBF slurry and the BRF slurry are dispersed to obtain a NBF dispersion and a BRF dispersion.

[0076] (3) The NBF dispersion and the BRF dispersion were mixed evenly at an absolute dry mass ratio of 6:4 (i.e., the mass ratio of bleached sulfate tender bamboo fiber to bamboo root fiber) to obtain a NBF / BRF mixed slurry.

[0077] (4) Add modified bamboo cellulose nanocrystals (BNC, length 50-200 nm, diameter 2-30 nm) to the NBF / BRF mixed slurry under stirring (rotation speed 5000 r / min), the amount of modified bamboo fiber nanocrystals added is 5.0% of the absolute dry mass of the NBF / BRF / BNC composite slurry, mix evenly, and obtain NBF / BRF / BNC composite slurry.

[0078] (5) The NBF / BRF / BNC composite pulp was formed on an inclined wire paper machine at a pulp mass concentration of 0.5%, and then dehydrated and dried to obtain bamboo paper sample A.

[0079] (6) The upper and lower surfaces of bamboo paper sample A are evenly sprayed with bamboo vinegar liquid with a mass concentration of 4.0% and a spraying amount of 3.0 g / m 2 , and then use an electric infrared generator to infrared dry the paper sample at 140°C for 38 minutes to obtain bamboo paper sample B.

[0080] (7) Bamboo paper sample B was subjected to hot pressing treatment at a temperature of 92°C and a pressure of 30 MPa for 20 min, and then infrared drying was performed at 85°C for 14 min to obtain bamboo fiber-based food fresh-keeping packaging paper.

[0081] The performance indicators of the bamboo fiber-based food fresh-keeping packaging paper prepared in this embodiment are as follows: Basis weight: 56g / m 2 ;Tensile strength: 3.16kN / m;Tear strength: 687.3mN;Oxygen permeability: 501cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 143g / m 2 ·day; Water contact angle: 111°; Cobb water absorption value: 10.4g / m 2 ; Antibacterial rate: 92%; Anti-mildew grade is Grade Ⅰ.

[0082] Example 3

[0083] This embodiment provides a method for preparing bamboo fiber-based food fresh-keeping packaging paper, and the specific preparation steps are as follows:

[0084] (1) Bleached sulfate young bamboo fiber (NBF, length 2-20 mm, diameter 10-25 μm) was refined in a double-disc refiner at a refining speed of 700 r / min and a refining concentration of 4.8 wt% to obtain NBF pulp with a beating degree SR of 38°; and bamboo root fiber (BRF, length 5-30 mm, diameter 28-40 μm) was refined in a double-disc refiner at a refining speed of 850 r / min and a refining concentration of 3.2 wt% to obtain BRF pulp with a beating degree SR of 48°.

[0085] (2) The NBF slurry and the BRF slurry are dispersed to obtain a NBF dispersion and a BRF dispersion.

[0086] (3) The NBF dispersion and the BRF dispersion were mixed evenly at an absolute dry mass ratio of 7:4 (i.e., the mass ratio of bleached sulfate tender bamboo fiber to bamboo root fiber) to obtain a NBF / BRF mixed slurry.

[0087] (4) Add modified bamboo cellulose nanocrystals (BNC, length 50-200 nm, diameter 2-30 nm) to the NBF / BRF mixed slurry under stirring (rotation speed 6000 r / min), the amount of modified bamboo fiber nanocrystals added is 6.0% of the absolute dry mass of the NBF / BRF / BNC composite slurry, mix evenly, and obtain NBF / BRF / BNC composite slurry.

[0088] (5) The NBF / BRF / BNC composite pulp was formed on an inclined wire paper machine at a pulp mass concentration of 0.7%, and then dehydrated and dried to obtain bamboo paper sample A.

[0089] (6) The upper and lower surfaces of bamboo paper sample A are evenly sprayed with bamboo vinegar liquid with a mass concentration of 4.5% and a spraying amount of 4.0 g / m 2 , and then use an electric infrared generator to infrared dry the paper sample at 160°C for 45 minutes to obtain bamboo paper sample B.

[0090] (7) Bamboo paper sample B was subjected to hot pressing treatment at a temperature of 95°C and a pressure of 33 MPa for 25 min, and then infrared drying was performed at 88°C for 17 min to obtain bamboo fiber-based food fresh-keeping packaging paper.

[0091] The performance indicators of the bamboo fiber-based food fresh-keeping packaging paper prepared in this embodiment are as follows: Basis weight: 58g / m 2 ;Tensile strength: 3.31kN / m;Tear strength: 705.6mN;Oxygen permeability: 472cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 127g / m 2 ·day; Water contact angle: 117°; Cobb water absorption value: 8.3g / m 2 ; Antibacterial rate: 95%; Anti-mildew grade is Grade I.

[0092] Example 4

[0093] This embodiment provides a method for preparing bamboo fiber-based food fresh-keeping packaging paper, and the specific preparation steps are as follows:

[0094] (1) Bleached sulfate young bamboo fiber (NBF, length 2-20 mm, diameter 10-25 μm) was refined in a double-disc refiner at a refining speed of 750 r / min and a refining concentration of 5.0 wt% to obtain NBF pulp with a beating degree SR of 40°; and bamboo root fiber (BRF, length 5-30 mm, diameter 28-40 μm) was refined in a double-disc refiner at a refining speed of 980 r / min and a refining concentration of 3.5 wt% to obtain BRF pulp with a beating degree SR of 50°.

[0095] (2) The NBF slurry and the BRF slurry are dispersed to obtain a NBF dispersion and a BRF dispersion.

[0096] (3) The NBF dispersion and the BRF dispersion were mixed evenly at an absolute dry mass ratio of 7:3 (i.e., the mass ratio of bleached sulfate tender bamboo fiber to bamboo root fiber) to obtain a NBF / BRF mixed slurry.

[0097] (4) Add modified bamboo cellulose nanocrystals (BNC, length 50-200 nm, diameter 2-30 nm) into the NBF / BRF mixed slurry under stirring (rotation speed 7000 r / min), the amount of modified bamboo fiber nanocrystals added is 7.0% of the absolute dry mass of the NBF / BRF / BNC composite slurry, mix evenly, and obtain NBF / BRF / BNC composite slurry.

[0098] (5) The NBF / BRF / BNC composite pulp was formed on an inclined wire paper machine at a pulp mass concentration of 1.0%, and then dehydrated and dried to obtain bamboo paper sample A.

[0099] (6) The upper and lower surfaces of the bamboo paper sample A are evenly sprayed with bamboo vinegar liquid with a mass concentration of 5.0%, and the spraying amount is 5.0 g / m 2 , and then use an electric infrared generator to infrared dry the paper sample at 180°C for 50 minutes to obtain bamboo paper sample B.

[0100] (7) Bamboo paper sample B was subjected to hot pressing treatment at a temperature of 98°C and a pressure of 36 MPa for 30 min, and then infrared drying was performed at 90°C for 20 min to obtain bamboo fiber-based food fresh-keeping packaging paper.

[0101] The performance indicators of the bamboo fiber-based food fresh-keeping packaging paper prepared in this embodiment are as follows: Basis weight: 60g / m 2 ;Tensile strength: 3.48kN / m;Tear strength: 737.2mN;Oxygen permeability: 446cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 118g / m 2 ·day; Water contact angle: 128°; Cobb water absorption value: 6.7g / m 2 ; Antibacterial rate: 96%; Anti-mildew grade is Grade I.

[0102] Comparative Example 1

[0103] This comparative example provides a method for preparing a bamboo fiber-based food fresh-keeping packaging paper, and the specific preparation steps are as follows:

[0104] (1) Bleached sulfate young bamboo fiber (NBF, length 2-20 mm, diameter 10-25 μm) was refined in a double-disc refiner at a refining speed of 500 r / min and a refining concentration of 4.0 wt% to obtain NBF pulp with a beating degree of 35° SR.

[0105] (2) The NBF slurry is dispersed to obtain NBF fiber slurry.

[0106] (3) Add modified bamboo cellulose nanocrystals (BNC, length 50-200 nm, diameter 2-30 nm) to the NBF fiber slurry under stirring (rotation speed 4000 r / min), the amount of modified bamboo fiber nanocrystals added is 4.0% of the absolute dry mass of the NBF / BNC composite slurry, and mix evenly to obtain NBF / BNC composite slurry.

[0107] (4) The NBF / BNC composite pulp was formed on an inclined wire paper machine at a pulp mass concentration of 0.2%, and then dehydrated and dried to obtain bamboo paper sample A.

[0108] (5) The upper and lower surfaces of bamboo paper sample A are evenly sprayed with bamboo vinegar liquid with a mass concentration of 3.5% and a spraying amount of 2.0 g / m 2 , and then use an electric infrared generator to infrared dry the paper sample at 100°C for 30 minutes to obtain bamboo paper sample B.

[0109] (6) Bamboo paper sample B was subjected to hot pressing treatment at a temperature of 88°C and a pressure of 28 MPa for 15 min, and then infrared drying was performed at 82°C for 10 min to obtain bamboo fiber-based food fresh-keeping packaging paper.

[0110] The performance indicators of the bamboo fiber-based food fresh-keeping packaging paper prepared in this comparative example are as follows: Basis weight: 54g / m 2 ;Tensile strength: 1.84kN / m;Tear strength: 513.6mN;Oxygen permeability: 735cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 324g / m 2 ·day; Water contact angle: 92°; Cobb water absorption value: 33.1g / m 2 ; Antibacterial rate: 82%; Anti-mildew grade is Level Ⅰ.

[0111] Comparative Example 2

[0112] This comparative example provides a method for preparing a bamboo fiber-based food fresh-keeping packaging paper, and the specific preparation steps are as follows:

[0113] (1) Bleached sulfate young bamboo fiber (NBF, length 2-20 mm, diameter 10-25 μm) was refined in a double-disc refiner at a refining speed of 500 r / min and a refining concentration of 4.0 wt% to obtain NBF pulp with a beating degree SR of 35°; and bamboo root fiber (BRF, length 5-30 mm, diameter 28-40 μm) was refined in a double-disc refiner at a refining speed of 600 r / min and a refining concentration of 2.5 wt% to obtain BRF pulp with a beating degree SR of 45°.

[0114] (2) The NBF slurry and the BRF slurry are dispersed to obtain a NBF dispersion and a BRF dispersion.

[0115] (3) The NBF dispersion and the BRF dispersion were mixed evenly at an absolute dry mass ratio of 5:5 (i.e., the mass ratio of bleached sulfate tender bamboo fiber to bamboo root fiber) to obtain a NBF / BRF mixed slurry.

[0116] (4) The NBF / BRF mixed slurry was formed on an inclined wire paper machine at a slurry mass concentration of 0.2%, and then dehydrated and dried to obtain bamboo paper sample A.

[0117] (5) The upper and lower surfaces of bamboo paper sample A are evenly sprayed with bamboo vinegar liquid with a mass concentration of 3.5% and a spraying amount of 2.0 g / m 2 , and then use an electric infrared generator to infrared dry the paper sample at 100°C for 30 minutes to obtain bamboo paper sample B.

[0118] (6) Bamboo paper sample B was subjected to hot pressing treatment at a temperature of 88°C and a pressure of 28 MPa for 15 min, and then infrared drying was performed at 82°C for 10 min to obtain bamboo fiber-based food fresh-keeping packaging paper.

[0119] The performance indicators of the bamboo fiber-based food fresh-keeping packaging paper prepared in this comparative example are as follows: Basis weight: 54g / m 2 ;Tensile strength: 1.73kN / m;Tear strength: 503.8mN;Oxygen permeability: 752cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 316g / m 2 ·day; Water contact angle: 72°; Cobb water absorption value: 42.4g / m 2 ; Antibacterial rate: 78%; Anti-mildew grade is Level Ⅰ.

[0120] Comparative Example 3

[0121] This comparative example provides a method for preparing a bamboo fiber-based food fresh-keeping packaging paper, and the specific preparation steps are as follows:

[0122] (1) Bleached sulfate young bamboo fiber (NBF, length 2-20 mm, diameter 10-25 μm) was refined in a double-disc refiner at a refining speed of 500 r / min and a refining concentration of 4.0 wt% to obtain NBF pulp with a beating degree SR of 35°; and bamboo root fiber (BRF, length 5-30 mm, diameter 28-40 μm) was refined in a double-disc refiner at a refining speed of 600 r / min and a refining concentration of 2.5 wt% to obtain BRF pulp with a beating degree SR of 45°.

[0123] (2) The NBF slurry and the BRF slurry are dispersed to obtain a NBF dispersion and a BRF dispersion.

[0124] (3) The NBF dispersion and the BRF dispersion were mixed evenly at an absolute dry mass ratio of 5:5 (i.e., the mass ratio of bleached sulfate tender bamboo fiber to bamboo root fiber) to obtain a NBF / BRF mixed slurry.

[0125] (4) Add modified bamboo cellulose nanocrystals (BNC, length 50-200 nm, diameter 2-30 nm) to the NBF / BRF mixed slurry under stirring (rotation speed 4000 r / min), the amount of modified bamboo fiber nanocrystals added is 4.0% of the absolute dry mass of the NBF / BRF / BNC composite slurry, mix evenly, and obtain NBF / BRF / BNC composite slurry.

[0126] (5) The NBF / BRF / BNC composite pulp was formed on an inclined wire paper machine at a pulp mass concentration of 0.2%, and then dehydrated and dried to obtain bamboo paper sample A.

[0127] (6) Bamboo paper sample A was subjected to hot pressing treatment at a temperature of 88°C and a pressure of 28 MPa for 15 min, and then infrared drying was performed at 82°C for 10 min to obtain bamboo fiber-based food fresh-keeping packaging paper.

[0128] The performance indicators of the bamboo fiber-based food fresh-keeping packaging paper prepared in this comparative example are as follows: Basis weight: 54g / m 2 ;Tensile strength: 2.36kN / m;Tear strength: 612.5mN;Oxygen permeability: 673cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 468g / m 2 ·day; Water contact angle: 65°; Cobb water absorption value: 51.2g / m 2 ; Antibacterial rate: 71%; Anti-mildew grade is grade III.

[0129] Comparative Example 4

[0130] This comparative example provides a method for preparing a bamboo fiber-based food fresh-keeping packaging paper, and the specific preparation steps are as follows:

[0131] (1) Bleached sulfate bamboo fiber (BF, length 2-15 mm, diameter 27-52 μm) was refined in a double-disc refiner at a refining speed of 500 r / min and a refining concentration of 4.0 wt% to obtain BF pulp with a beating degree SR of 35°; bamboo shoot husk fiber (SF, length 5-20 mm, diameter 30-45 μm) was refined in a double-disc refiner at a refining speed of 600 r / min and a refining concentration of 2.5 wt% to obtain SF pulp with a beating degree SR of 45°.

[0132] (2) The BF slurry and the SF slurry are dispersed to obtain a BF dispersion and a SF dispersion.

[0133] (3) The BF dispersion and the SF dispersion were uniformly mixed at an absolute dry mass ratio of 5:5 (i.e., the mass ratio of the bleached sulfate bamboo fiber to the bamboo shoot shell fiber) to obtain a BF / SF mixed slurry.

[0134] (4) Adding nano-antibacterial bamboo powder (BP, particle diameter of 50-500 nm) to the BF / SF mixed slurry under stirring (rotation speed of 4000 r / min), the amount of nano-antibacterial bamboo powder added is 4.0% of the absolute dry mass of the BF / SF / BP composite slurry, and mixing evenly to obtain a BF / SF / BP composite slurry.

[0135] (5) The BF / SF / BP composite pulp was formed on an inclined wire paper machine at a pulp mass concentration of 0.2%, and then dehydrated and dried to obtain bamboo paper sample A.

[0136] (6) The upper and lower surfaces of bamboo paper sample A are uniformly sprayed with a 3.5% mass concentration of diquaternary ammonium salt chitosan and bamboo nanocellulose composite liquid, wherein the absolute dry weight ratio of diquaternary ammonium salt chitosan to bamboo nanocellulose is 5:5, and the spraying amount is 2.0 g / m 2 , and then use an electric infrared generator to infrared dry the paper sample at 100°C for 30 minutes to obtain bamboo paper sample B.

[0137] (7) Bamboo paper sample B was subjected to hot pressing treatment at a temperature of 88°C and a pressure of 28 MPa for 15 min, and then infrared drying was performed at 82°C for 10 min to obtain bamboo fiber-based food fresh-keeping packaging paper.

[0138] The performance indicators of the bamboo fiber-based food fresh-keeping packaging paper prepared in this comparative example are as follows: Basis weight: 54g / m 2 ;Tensile strength: 2.65kN / m;Tear strength: 616.8mN;Oxygen permeability: 562cm3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 183g / m 2 ·day; water contact angle: 69°; Cobb water absorption value: 46.7g / m 2 ; Antibacterial rate: 87%; Anti-mildew grade is IV.

[0139] Fruit and vegetable preservation experiment

[0140] The bamboo fiber-based packaging papers prepared in Examples 1, 2, 3, 4 and Comparative Examples 1, 2, 3, 4 were sealed to form packaging bags, and yellow apricots with similar colors, sizes, and shapes and without mechanical damage were selected, washed with clean water, naturally air-dried, and then packed into various types of paper-based packaging bags. Three parallel samples were set for each group, stored at room temperature for 9 days, and the packaging bags were opened and tested every 2 days (1, 3, 5, 7, and 9 days), and the preservation effect indicators of the packaging bags were recorded. The preservation effect indicators were mass loss rate, decay rate, and hardness. The test method was as follows:

[0141] (1) Determination of mass loss rate: The mass loss was measured by weighing. The yellow apricot samples were weighed once before and after storage, and the mass loss rate (R) was calculated as follows: R = (m1-m2) / m1×100%, where m1 is the mass of the yellow apricot before storage, g; m2 is the mass of the yellow apricot after storage, g.

[0142] (2) Determination of rot rate: The yellow apricot is considered rotten if the fruit is obviously rotten or moldy. The rot rate F is calculated as follows: F = (number of rotten fruits / total number of fruits) × 100%.

[0143] (3) Hardness measurement: The hardness index of yellow apricot was tested using a texture analyzer. The measurement parameters were: speed before test 1.0 mm / s, test speed 2.0 mm / s, speed after test 2.0 mm / s, trigger type was pressure, and trigger value was 5.0 gf.

[0144] Among them, the results of mass loss rate (%), decay rate (%), and hardness (g) are shown in Table 1, Table 2, and Table 3, respectively.

[0145] Table 1

[0146]

[0147] Table 2

[0148]

[0149]

[0150] Table 3

[0151]

[0152] As can be seen from the data in Table 1-3, the bamboo fiber-based food fresh-keeping packaging paper in Examples 1-4 has a better fresh-keeping effect than the packaging paper in Comparative Examples 1-4. Among them, compared with the packaging paper in Comparative Example 4, the fresh-keeping packaging paper in Examples 1-4 has a better fresh-keeping effect on freshly picked yellow apricots, and the yellow apricot corruption rate and quality loss rate are both reduced, and the hardness decreases relatively slowly, delaying the softening of the yellow apricots and maintaining the quality of the yellow apricots to the greatest extent. Therefore, through the analysis of the quality indicators of yellow apricots during storage, it can be seen that the bamboo fiber-based food fresh-keeping packaging paper in Examples 1-4 has a certain fresh-keeping effect on yellow apricots, can effectively inhibit the quality loss of yellow apricots, and improve the sensory quality of yellow apricots, thereby delaying the decay and deterioration of yellow apricots and achieving a longer shelf life. The bamboo fiber-based food fresh-keeping packaging paper in the present invention can improve the storage quality of yellow apricots and greatly reduce the corruption rate and nutritional value loss of yellow apricots.

[0153] Experimental study on hydrophobic properties of modified bamboo cellulose nanocrystals

[0154] This experiment compares the hydrophobic properties of the modified bamboo cellulose nanocrystals obtained by the preparation method of the present invention and the modified bamboo cellulose nanocrystals obtained by the conventional preparation method.

[0155] Comparative experimental steps: Place 50-70 mL of 55-60% sulfuric acid solution in a water bath (water bath temperature: 45-50°C). Accurately weigh 3.0-4.0 g of bleached kraft softwood pulp and slowly add it to the 55-60% sulfuric acid solution, stirring and hydrolyzing for 45-50 minutes at 45-50°C. Add 10-15 times the volume of deionized water of the above reaction system to terminate the acid hydrolysis reaction. Then use the centrifugal separation method to wash the solids, remove the upper solution, and continue to wash the solid sediment in the lower layer with water. Repeat this centrifugal washing process several times until the upper solution becomes turbid. Collect the solids in the lower layer, put them into a dialysis bag and place them in clean water for dialysis. Finally, centrifuge the solid and liquid in the dialysis bag again and collect the upper light blue solution. Rotary evaporation and concentration can obtain bamboo cellulose nanocrystal water suspensions of different concentrations for standby use. Put it into a freeze drying oven for freeze drying for 48 to 72 hours to obtain bamboo cellulose nanocrystals. Then put 5 to 10 g of bamboo cellulose nanocrystals into a flask containing 50 to 80 mL of glacial acetic acid, heat it to 50 to 60°C, add 10 to 20 mL of acetic anhydride reagent and 500 μL of perchloric acid respectively, react for 60 to 80 minutes, pour it into ethanol to precipitate white flocculent precipitate, then centrifuge, then wash it with ethanol 3 to 5 times, and then centrifuge and wash it with deionized water 2 to 3 times, finally obtain acetylated bamboo cellulose nanocrystal water suspension, put it into a freeze drying oven for freeze drying for 48 to 72 hours, and obtain acetylated bamboo cellulose nanocrystal solid powder.

[0156] The test data show that the water contact angle of the modified bamboo cellulose nanocrystal obtained by the present invention is 90.3°, while the water contact angle of the modified bamboo cellulose nanocrystal obtained by the comparative experiment is only 67.5°. Therefore, the hydrophobic performance of the modified bamboo cellulose nanocrystal obtained by the preparation method adopted by the present invention is better than that of the conventional preparation method. Among them, sulfuric acid is a corrosive acid, toxic, and non-recyclable.

[0157] In general, the present invention adopts bamboo as the basic raw material. Bamboo is a large bamboo material with the advantages of fast growth rate, wide distribution range, excellent fiber quality, strong regeneration ability, etc. The food preservation packaging paper prepared from different raw materials such as bamboo fiber, bamboo root, bamboo nanocellulose, bamboo vinegar liquid on the same bamboo can be naturally biodegraded, belongs to environmentally friendly packaging materials, and can realize the use of bamboo instead of plastic in the field of food preservation packaging materials. The bamboo fiber-based food preservation packaging paper prepared by the present invention is prepared by a reasonable compounding of two types of fiber raw materials on bamboo, making full use of the advantages of bamboo fibers from different parts of bamboo: bamboo root fibers are long and strong, which can significantly improve the physical strength of bamboo-based packaging paper; tender bamboo trunk fibers are delicate and soft, with good fiber morphology, which can ensure close bonding between fibers; in addition, bamboo fibers contain flavonoids, wax and other substances, have good air permeability and wear resistance, and have natural antibacterial, mite removal, deodorization and other effects. Bamboo vinegar is a byproduct obtained by pyrolysis of bamboo. It is a liquid (pH value 2.5-3) made by burning bamboo for more than 5 years. It contains organic acids, alcohols, phenols, esters and trace alkaline components, etc. It has the characteristics of mildew resistance, antibacterial, antioxidant, deodorization and peculiar smell, which are all conducive to improving the food preservation effect of packaging paper. Among them, the esters in the bamboo vinegar can also assist in improving the hydrophobic effect. The present invention adopts the addition of nano-sized modified bamboo cellulose nanocrystals in the slurry, and the bamboo cellulose nanocrystals modified by acetylation can not only be used as paper reinforcing filler, but also have good moisture-proof and water-blocking effect. Acetylation improves the hydrophobicity, thermal stability and chemical stability of nanocellulose, while retaining its original biocompatibility and nano-size advantages. Acetylation modification can change the properties and surface characteristics of nanocellulose, so that BNC can form strong covalent bonds and hydrogen bonds with the hydroxyl groups on the surface of bamboo cellulose, which can not only increase the mechanical strength of the packaging paper, but also improve the pore structure of the packaging paper and increase the barrier capacity. The addition of bamboo nanocellulose is conducive to improving the interface bonding between bamboo fibers, so that the packaging paper exhibits good mechanical strength and barrier properties. The bamboo fiber, bamboo root fiber, bamboo nanocellulose, and bamboo vinegar used in the present invention are all derived from moso bamboo, realizing the utilization of all components of a bamboo. The prepared bamboo fiber-based food fresh-keeping packaging paper has good mechanical properties, barrier properties, hydrophobic properties, and antibacterial properties, and can be used in the field of food fresh-keeping packaging materials, which will promote the high-quality development of the bamboo industry and realize the high-value utilization of bamboo instead of plastic in the field of food packaging.

[0158] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing bamboo fiber-based food fresh-keeping packaging paper, characterized in that: The following steps are involved: (1) bleached sulfate tender bamboo fiber and bamboo root fiber are respectively subjected to pulping treatment to obtain NBF pulp with a beating degree of 35-40°SR and BRF pulp with a beating degree of 45-50°SR; (2) dispersing the NBF slurry and the BRF slurry in step (1) to obtain NBF dispersion and BRF dispersion; (3) uniformly mixing the NBF dispersion and the BRF dispersion in step (2) to obtain a NBF / BRF mixed slurry; (4) adding the modified bamboo cellulose nanocrystals to the NBF / BRF mixed slurry obtained in step (3) under stirring conditions, mixing evenly, and obtaining a NBF / BRF / BNC composite slurry; (5) papermaking, shaping, dehydrating, and drying the NBF / BRF / BNC composite slurry described in step (4) to obtain a bamboo paper sample A; (6) In step (5), the outer surface of the bamboo paper sample A is evenly sprayed with bamboo vinegar, and dried to obtain a bamboo paper sample B; (7) The bamboo paper sample B described in step (6) is subjected to heat pressing and drying to obtain a bamboo fiber-based food fresh-keeping packaging paper.

2. The method for preparing a bamboo fiber-based food fresh-keeping packaging paper according to claim 1, characterized in that: The bleached sulfate tender bamboo fiber in step (1) has a length of 2 to 20 mm and a diameter of 10 to 25 μm; the bamboo root fiber has a length of 5 to 30 mm and a diameter of 28 to 40 μm; The mass ratio of the bleached sulfate tender bamboo fiber to the bamboo root fiber in step (1) is 5:5 to 7:3; The amount of the modified bamboo fiber nanocrystals added in step (4) is 4.0-7.0% of the mass of the NBF / BRF / BNC composite slurry; The slurry concentration of the NBF / BRF / BNC composite slurry in step (4) is 0.2-1.0% by mass.

3. The method for preparing a bamboo fiber-based food fresh-keeping packaging paper according to claim 1, characterized in that: The concentration of the bamboo vinegar in step (6) is 3.5-5.0% by mass; The amount of bamboo vinegar sprayed on the outer surface of the bamboo paper sample A in step (6) is 2.0 to 5.0 g / m 2 .

4. The method for preparing a bamboo fiber-based food fresh-keeping packaging paper according to claim 1, characterized in that: The pulping treatment conditions of the bleached sulfate tender bamboo fiber in step (1) are: the pulping speed is 500-750r / min, and the pulping concentration is 4.0-5.0wt%; the pulping treatment conditions of the bamboo root fiber are: the pulping speed is 600-980r / min, and the pulping concentration is 2.5-3.5wt%; The stirring speed in step (4) is 4000-7000 r / min.

5. The method for preparing a bamboo fiber-based food fresh-keeping packaging paper according to claim 1, characterized in that: The modified bamboo cellulose nanocrystals in step (4) have a length of 50 to 200 nm and a diameter of 2 to 30 nm; the modified bamboo cellulose nanocrystals are prepared by the following method: The bleached sulfate bamboo pulp is hydrolyzed by organic acid, dialyzed, centrifuged, and then modified by acetylation to obtain modified bamboo cellulose nanocrystals.

6. The method for preparing a bamboo fiber-based food fresh-keeping packaging paper according to claim 5, characterized in that: The modified bamboo cellulose nanocrystals are prepared by the following method: 3.0-4.0 g of bleached kraft softwood pulp is slowly added to 50-70 mL of a maleic acid solution having a concentration of 55-60%, and stirred and hydrolyzed in a water bath at 45-50° C. for 45-50 minutes. Subsequently, the acid hydrolysis reaction is terminated by adding deionized water, and the solid is washed by centrifugation for multiple times to purify. Finally, the purified solid is dialyzed, and centrifuged again to obtain a light blue solution, which is concentrated by rotary evaporation to obtain a bamboo cellulose nanocrystal water suspension of different concentrations, and the suspension is placed in a freeze drying oven for freeze drying for 48-72 hours to obtain bamboo cellulose nanocrystals of different concentrations. 5-10 g of bamboo cellulose nanocrystals are placed in a flask containing 50-80 mL of glacial acetic acid, the temperature is raised to 50-60° C., 10-20 mL of acetic anhydride reagent and 500 μL of dicyclohexylcarbodiimide are added respectively, and after reacting for 60-80 minutes, the precipitate is poured into ethanol to precipitate a white flocculent precipitate, which is then centrifuged and then washed with ethanol for 3-5 times, and then washed with deionized water by centrifugation for 2-3 times to finally obtain an acetylated bamboo cellulose nanocrystal water suspension, which is placed in a freeze drying oven for freeze drying for 48-72 hours to obtain acetylated bamboo cellulose nanocrystals.

7. The method for preparing a bamboo fiber-based food fresh-keeping packaging paper according to claim 1, characterized in that: The drying method in step (6) is: infrared drying at 100-180° C. for 30-50 min; The hot pressing conditions in step (7) are: temperature of 88-98° C., pressure of 28-36 MPa, and time of 15-30 min; The drying method in step (7) is: infrared drying at 82-90° C. for 10-20 minutes.

8. A bamboo fiber-based food fresh-keeping packaging paper, characterized in that: The method is obtained by the preparation method described in any one of claims 1 to 7.

9. Use of the bamboo fiber-based food fresh-keeping packaging paper according to claim 8 in food fresh-keeping packaging materials.

10. The use according to claim 9, characterized in that: The food fresh-keeping packaging material is a fresh-keeping packaging material used for packaging fruits and vegetables.

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