Degradable bamboo fiber express packaging bag and preparation method thereof

Abstract

The invention discloses a degradable bamboo fiber express packaging bag and a preparation method thereof, and belongs to the technical field of express packaging. The packaging bag is prepared from, by mass, 32-42 parts of pretreated bamboo fibers, 22-28 parts of poly (butylene succinate), 9-14 parts of modified nano calcium carbonate, 12-16 parts of polycaprolactone, 6-11 parts of acetylated chitosan and the like, and the key raw materials are all treated through an exclusive pretreatment or modification process. The preparation method comprises the steps of raw material plasma activation, segmented high-speed mixing, vacuum drying, precise-parameter twin-screw extrusion granulation, secondary drying, precise film blowing, high-precision heat-sealing bag making and the like, and the technological parameters of all the steps are clear. The product disclosed by the invention can be efficiently degraded in a natural environment, has excellent tensile resistance, puncture resistance and impact resistance, is stable and controllable in processing process, and is adaptive to actual requirements of express packaging and industrial batch production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmental protection materials, and particularly relates to a degradable bamboo fiber express packaging bag and a preparation method thereof. BACKGROUND

[0002] In today's society, with the rapid development of e-commerce, the express industry is growing explosively, and the use of express packaging bags is increasing sharply. Traditional express packaging bags are mostly made of petroleum-based plastics such as polyethylene and polypropylene. Although these materials have certain strength and toughness and can meet the basic protection needs in the express transportation process, they have fatal defects. They are extremely difficult to degrade in the natural environment and often take hundreds or even thousands of years to decompose, resulting in a large amount of plastic waste accumulation, causing serious pollution to soil, water and ecological system, and the problem of "white pollution" is becoming increasingly serious, which brings heavy burden to the earth's ecological environment. To address this challenge, researchers and industry practitioners actively explore degradable packaging materials to replace traditional plastics. Although some degradable materials have certain degradation performance, they still have many problems in actual application. For example, some biodegradable materials have a slow degradation rate in the natural environment and are difficult to effectively reduce the stock of plastic waste in a short period of time; some materials are prone to damage during use due to insufficient toughness and strength during the degradation process, and cannot fully meet the actual use requirements of express packaging. At the same time, biodegradable materials often have poor flowability and uniformity during processing, resulting in uneven quality of the final product, which seriously restricts the wide application of degradable materials in the field of express packaging. SUMMARY

[0003] The application provides a degradable bamboo fiber express packaging bag containing exclusive pretreated and modified raw materials (pretreated bamboo fiber, modified nano calcium carbonate, etc.) and a matching preparation method, which solves the problems of poor compatibility, difficult balance between degradation and mechanical properties, and fuzzy process parameters due to unmodified raw materials, and overcomes the deficiencies of low process precision and lack of functional components due to only conventional drying of raw materials and low process precision, and realizes efficient degradation and stable performance of the material.

[0004] To achieve the above-mentioned purposes, the technical scheme adopted by the application is as follows: A kind of degradation bamboo fiber express packaging bag, by mass parts, it is composed of the following components: pretreated bamboo fiber 32~42 parts, polybutylene succinate 22~28 parts, modified nano calcium carbonate 9~14 parts, polycaprolactone 12~16 parts, acetylated chitosan 6~11 parts, tributyl citrate 4~7 parts, doped titanium dioxide 2.5~4.5 parts, ethylene-vinyl acetate copolymer 6~9 parts, maleic anhydride grafted polyethylene 4~6 parts, antioxidant 1010 1.5~2.5 parts.The active group is formed on the surface of pretreated bamboo fiber, which can form stable intermolecular combination with degradable high molecular materials such as polybutylene succinate and polycaprolactone, modified nano calcium carbonate improves the dispersibility in the system through surface modification, synergistically enhances the mechanical strength of the material, acetylated chitosan optimizes the compatibility of the material, doped titanium dioxide helps to improve the degradation efficiency, and the synergistic effect of each component makes the packaging bag efficiently degrade in natural environment, while having tensile resistance, puncture resistance and impact resistance, meeting the protection requirements of express packaging, and the material system is suitable for industrial batch processing, solving the problem of poor compatibility of ordinary bamboo fiber with other raw materials, and difficult to balance material strength and degradation efficiency.

[0005] Further, the preparation process of the pretreated bamboo fiber is as follows: the bamboo fiber is placed in a sodium hydroxide solution with a mass concentration of 5.5~7.5%, soaked at a temperature of 65~75℃ for 2.2~2.8 hours, washed with deionized water to a pH value of 7.0±0.2, then placed in a silane coupling agent KH-560 ethanol solution with a mass concentration of 3.5~4.5%, stirred at a temperature of 52~58℃ and a rotation speed of 300~350r / min for 1.2~1.8 hours, filtered after reaction, and dried at a temperature of 85~95℃ for 4~6 hours to obtain the pretreated bamboo fiber.The pretreatment process can remove impurities on the surface of bamboo fiber and introduce active groups, avoiding the problem of weak material interface bonding and insufficient mechanical properties caused by direct mixing of bamboo fiber.

[0006] Further, the preparation process of the modified nano calcium carbonate is as follows: nano calcium carbonate is added to deionized water, ultrasonic dispersion is carried out for 15~20 minutes to obtain a suspension with a mass concentration of 8~12%, 3~5% of nano calcium carbonate by mass is added as stearic acid, stirred at a temperature of 70~80℃ and a rotation speed of 250~300r / min for 1.5~2.5 hours, centrifuged after reaction, dried at a temperature of 100~110℃ for 3~4 hours, and crushed through a 200~300 mesh sieve to obtain the modified nano calcium carbonate.The modification process improves the compatibility of nano calcium carbonate with high molecular materials, solving the problem of uneven material performance caused by easy aggregation of ordinary calcium carbonate.

[0007] Further, the preparation process of the acetylated chitosan is as follows: chitosan is dissolved in an acetic acid solution with a mass concentration of 2-3% to prepare a chitosan solution with a mass concentration of 5-8%, acetic anhydride accounting for 10-15% of the mass of chitosan is added, stirring is performed at a temperature of 40-50°C and a rotation speed of 200-250 r / min for 2-3 hours, after the reaction, a sodium hydroxide solution with a mass concentration of 5-8% is used to adjust the pH value to 7.0±0.2, a precipitate is separated out, after filtration, the precipitate is washed with deionized water for 3-5 times, and vacuum drying is performed at a temperature of 60-70°C for 5-7 hours to obtain the acetylated chitosan. The acetylation modification optimizes the processing fluidity of chitosan, and avoids the problem that chitosan is prone to caking when directly used, thereby affecting the uniformity of the material.

[0008] Further, the preparation process of the doped titanium dioxide is as follows: tetrabutyl titanate is dissolved in anhydrous ethanol to prepare a tetrabutyl titanate ethanol solution with a mass concentration of 15-20%, zinc nitrate accounting for 2-4% of the mass of the tetrabutyl titanate is added, a hydrochloric acid solution with a mass concentration of 1-2% is added dropwise to adjust the pH value to 2.0±0.2 after uniform stirring, hydrolysis is performed at a temperature of 60-70°C for 3-4 hours, a sol is formed, aging is performed at a temperature of 80-90°C for 12-16 hours, and then calcination is performed at a temperature of 500-600°C for 2-3 hours, and after cooling, the product is crushed and passed through a 300-400 mesh sieve to obtain the doped titanium dioxide. The doping process gives the titanium dioxide a better photocatalytic assisted degradation capacity, and makes up for the limitation that the degradation efficiency of the material depends on a single component.

[0009] Further, the volume ratio of ethanol to deionized water in the silane coupling agent KH-560 ethanol solution is 9:1, and nitrogen protection is adopted during the stirring reaction process to prevent the solution from being oxidized. The nitrogen protection can avoid the oxidation failure of the coupling agent, ensure the stability of the surface modification effect of the bamboo fiber, and further improve the bonding strength with the high polymer material.

[0010] Further, the stearic acid needs to be heated to 60-70°C to melt before being added to the nano calcium carbonate suspension, and ultrasonic assistance is adopted during the stirring reaction process, and the ultrasonic power is 150-200W. The ultrasonic assistance can promote the uniform coating of the stearic acid on the surface of the calcium carbonate, and avoid the problem of insufficient local strength of the material caused by uneven dispersion of the calcium carbonate.

[0011] Further, the acetic anhydride needs to be slowly added dropwise to the chitosan solution, the dropwise rate is 1-2 drops per second, and continuous stirring is performed during the dropwise process to prevent local excessive reaction. Slow dropwise and continuous stirring can ensure uniform acetylation reaction, avoid the problem that local excessive modification of chitosan affects the compatibility of the material, and solve the problem that chitosan is prone to agglomeration when directly mixed.

[0012] Further, in the preparation process of the tetrabutyl titanate ethanol solution, the tetrabutyl titanate needs to be slowly added to anhydrous ethanol under stirring at a stirring speed of 400-500 r / min to avoid local agglomeration. High-speed stirring can prevent the agglomeration of tetrabutyl titanate, ensure uniform subsequent doping reaction, and make titanium dioxide better play an auxiliary degradation role.

[0013] A preparation method of a degradable bamboo fiber express packaging bag, the method comprising the following steps: S1. Each raw material is weighed according to the mass fraction, the modified nano calcium carbonate and the doped titanium dioxide are put into a plasma treatment instrument, argon is introduced as a protective gas, surface activation treatment is carried out under the conditions of a treatment power of 220-280 W and a treatment time of 35-55 minutes; this step further improves the surface activity of the inorganic filler through plasma activation, and solves the problem of weak combination of the inorganic filler with the organic phase; S2. The modified nano calcium carbonate and the doped titanium dioxide treated in S1, polybutylene succinate, polycaprolactone, ethylene-vinyl acetate copolymer, and maleic anhydride grafted polyethylene are put into a high-speed mixer, mixed at a speed of 850-950 r / min and a temperature of 85-95℃ for 18-22 minutes, then acetylated chitosan and tributyl citrate are added, the speed is adjusted to 1050-1150 r / min and the temperature is adjusted to 95-105℃, and the mixture is continuously mixed for 22-28 minutes to obtain a premix; S3. The pretreated bamboo fiber is placed in a vacuum drying oven and dried at a temperature of 110-115℃ and a vacuum degree of -0.085 to -0.088 MPa for 3.5-4.5 hours to remove the internal moisture of the fiber; vacuum drying can completely remove the moisture, avoiding the problem of air bubbles caused by residual moisture during processing; S4. The premix obtained in S2 and the pretreated bamboo fiber dried in S3 are added to a twin-screw extruder, the screw speed is set to 160-190 r / min, the feeding speed is 9-11 kg / h, the temperature of each section of the extruder is set to: zone 1 142-148℃, zone 2 162-168℃, zone 3 178-182℃, zone 4 182-188℃, and the die temperature is 178-182℃, and after melt blending and extrusion, the plastic master batch is obtained by water cooling and granulation; precise control of the extrusion parameters can ensure sufficient melt blending of the material, solving the problem of unstable quality of the master batch caused by wide extrusion parameters; S5. The plastic master batch is placed in a hot air circulating drying oven and dried at a temperature of 82-88℃ for 2.2-2.8 hours to remove the residual moisture of the master batch; secondary drying further ensures the dryness of the master batch, avoiding defects in subsequent film blowing, which is better than a single drying step; S6. The dried plastic master batch is added to the film blowing machine, and the screw rotation speed is set to 65-75 r / min, the temperature of each section of the cylinder is set to: zone 1 152-158℃, zone 2 168-172℃, zone 3 172-178℃, and the die head temperature is set to 168-172℃, the blowing ratio is controlled to 2.8-3.2, the pulling speed is 6-7 m / min, and the film thickness is set to 0.05-0.07 mm; precise film blowing parameters can ensure uniform film thickness and stable mechanical properties, and can solve the problem of ambiguous film blowing parameters; S7. The film is rolled and sent to the bag making machine, and the hot sealing bag is made according to the preset size, the hot sealing temperature is set to 135-145℃, the hot sealing pressure is set to 0.35-0.45 MPa, and the hot sealing time is set to 1.2-1.8 seconds, and after bag making, the mouth is processed to get the degradation bamboo fiber express packaging bag; precise hot sealing parameters can ensure the sealing strength and meet the weight bearing demand of express packaging, which is better than the problem of too wide hot sealing parameter range.

[0014] Preferably, the argon flow of the plasma treatment instrument in S1 is controlled at 12-18 sccm, and the material is turned over every 10-15 minutes during the treatment process to ensure uniform activation of the material surface. Uniform activation can ensure consistent combination of inorganic fillers with organic phase, avoiding material performance fluctuation problem caused by uneven filler dispersion.

[0015] Preferably, the stirring paddle of the high-speed mixer in S2 is a double-layer spiral structure, the gap between the stirring paddle and the inner wall of the mixer is controlled at 3-4 mm, and the temperature is raised in stages during the mixing process, and the temperature rising rate is 2-3℃ / min. Double-layer spiral stirring and staged heating can improve mixing efficiency and uniformity, solving the problem of insufficient mixing of single stirring structure.

[0016] Preferably, the screw of the twin-screw extruder in S4 is a meshing type co-rotating twin screw with a length-diameter ratio of 42-44:1, and each section of the cylinder is equipped with a platinum resistance temperature sensor, and the temperature control accuracy is ±1℃. High-precision temperature control can ensure stable material melting state, avoiding the problem of master batch quality caused by rough temperature control.

[0017] Preferably, the die head of the film blowing machine in S6 is a ring-shaped gradual die head, the die head gap is controlled at 0.9-1.1 mm, the cold air temperature of the cold air ring at the die head outlet is controlled at 15-20℃, and the wind speed uniformity deviation is not more than ±0.5 m / s. Ring-shaped gradual die head and uniform cold air can ensure the film forming quality, which is different from the problem of uneven film thickness caused by ordinary die head.

[0018] Preferably, the automatic deviation correction device of the bag making machine in S7 adopts photoelectric induction type, the deviation correction response time is not more than 0.5 seconds, the tension control system adopts magnetic powder clutch, and the tension control accuracy is ±3%. High-precision deviation correction and tension control can ensure accurate bag making size, avoiding the problem of size deviation in the bag making process.

[0019] Advantages The present application realizes the dual core needs of "high strength protection" and "rapid degradation" required by express packaging through the synergistic effect of pretreated bamboo fiber (hydroxide impurity removal + silane coupling agent compatibility promotion), modified nano calcium carbonate (stearic acid coating + ultrasonic dispersion) and doped titanium dioxide (zinc doping to promote photocatalysis), so that the tensile strength of the product reaches 28.5~33.8MPa, the puncture resistance reaches 8.5~10.1N, and the 60-day degradation rate reaches 68.2~75.8%.

[0020] The present application details the whole process parameters: the power of plasma treatment is accurately 220~280W, the argon flow is 12~18sccm; the temperature of double screw extrusion is controlled in four zones (142~148℃ / 162~168℃, etc.), and the temperature accuracy is ±1℃; the blow-up ratio of film blowing is 2.8~3.2, and the pulling speed is 6~7m / min, so that the tensile strength deviation of the product is controlled within 5%, and the film thickness tolerance is ≤0.01mm, which can stably realize large-scale production.

[0021] The present application takes pretreated bamboo fiber (cost is only 1 / 3 of polylactic acid) as the core reinforcing phase, and the proportion is 32~42%, which greatly reduces the raw material cost; and all components are degradable, and there is no harmful residue after degradation. DETAILED DESCRIPTION The technical solutions in the embodiments of the present application are described clearly and completely, obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0022] Embodiment 1 Raw material composition (mass part): pretreated bamboo fiber 32 parts, polybutylene succinate 22 parts, modified nano calcium carbonate 9 parts, polycaprolactone 12 parts, acetylated chitosan 6 parts, tributyl citrate 4 parts, doped titanium dioxide 2.5 parts, ethylene-vinyl acetate copolymer 6 parts, maleic anhydride grafted polyethylene 4 parts, antioxidant 1010 1.5 parts. Preparation process: S1 plasma treatment (power 220 W, time 55 minutes, argon flow rate 12 seem); S2 step mixing (first 850 r / min, 85°C mixing for 22 minutes, then 1050 r / min, 95°C mixing for 28 minutes); S3 vacuum drying (110°C, -0.088 MPa, 4.5 hours); S4 extrusion (rotating speed 160 r / min, feeding 9 kg / h, temperature of each zone 142°C, 162°C, 178°C, 182°C, 178°C); S5 secondary drying (82°C, 2.8 hours); S6 film blowing (rotating speed 65 r / min, temperature of each zone 152°C, 168°C, 172°C, 168°C, blowing ratio 2.8, traction 6 m / min, thickness 0.07 mm); S7 heat sealing (135°C, 0.35 MPa, 1.8 seconds). Example 2 Raw material composition (mass parts): pretreated bamboo fiber 37 parts, polybutylene succinate 25 parts, modified nano calcium carbonate 11 parts, polycaprolactone 14 parts, acetylated chitosan 8 parts, tributyl citrate 5 parts, doped titanium dioxide 3.5 parts, ethylene-vinyl acetate copolymer 7 parts, maleic anhydride grafted polyethylene 5 parts, antioxidant 1010 2 parts. Preparation process: S1 plasma treatment (power 250 W, time 45 minutes, argon flow rate 15 seem); S2 step mixing (first 900 r / min, 90°C mixing for 20 minutes, then 1100 r / min, 100°C mixing for 25 minutes); S3 vacuum drying (112°C, -0.086 MPa, 4 hours); S4 extrusion (rotating speed 175 r / min, feeding 10 kg / h, temperature of each zone 145°C, 165°C, 180°C, 185°C, 180°C); S5 secondary drying (85°C, 2.5 hours); S6 film blowing (rotating speed 70 r / min, temperature of each zone 155°C, 170°C, 175°C, 170°C, blowing ratio 3.0, traction 6.5 m / min, thickness 0.06 mm); S7 heat sealing (140°C, 0.4 MPa, 1.5 seconds). Example 3 Raw material composition (mass parts): pretreated bamboo fiber 42 parts, polybutylene succinate 28 parts, modified nano calcium carbonate 14 parts, polycaprolactone 16 parts, acetylated chitosan 11 parts, tributyl citrate 7 parts, doped titanium dioxide 4.5 parts, ethylene-vinyl acetate copolymer 9 parts, maleic anhydride grafted polyethylene 6 parts, antioxidant 1010 2.5 parts. Preparation process: S1 plasma treatment (power 280 W, time 35 minutes, argon flow rate 18 sccm); S2 fractional mixing (first 950 r / min, 95°C mixing for 18 minutes, and then 1150 r / min, 105°C mixing for 22 minutes); S3 vacuum drying (115°C, -0.085 MPa, 3.5 hours); S4 extrusion (speed 190 r / min, feeding 11 kg / h, temperature of each zone 148°C, 168°C, 182°C, 188°C, 182°C); S5 secondary drying (88°C, 2.2 hours); S6 film blowing (speed 75 r / min, temperature of each zone 158°C, 172°C, 178°C, 172°C, blowing ratio 3.2, traction 7 m / min, thickness 0.05 mm); S7 heat sealing (145°C, 0.45 MPa, 1.2 seconds). Comparative Example 1 Raw material composition (mass parts) (according to the method disclosed in Publication No. CN114196145A): bamboo fiber 5 parts (without pretreatment), polyvinyl alcohol 25 parts, cassava starch 15 parts, calcium carbonate 10 parts (without modification), chitosan 5 parts (without acetylation), polyvinyl chloride 10 parts, antioxidant 8 parts, glycerol 10 parts, lubricant 2 parts.

[0023] Preparation process: according to the steps disclosed in Publication No. CN114196145A, stirring (120°C, 60 r / min, 30 minutes), polyvinyl alcohol dissolution (60°C, 400 r / min, 1 hour), vacuum drying (100°C), extrusion (140°C, 50 r / min), film blowing (thickness 0.5 mm). Comparative Example 2 Raw material composition (mass parts) (according to the method disclosed in Publication No. CN118852855A): polylactic acid 40 parts, polyphthalate 20 parts, starch 10 parts, polyvinyl alcohol 5 parts, bamboo fiber 2 parts (only dried at 80°C for 4 hours), wood powder 1 part, glycerol 1 part. Preparation process: according to the steps disclosed in Publication No. CN118852855A, drying (starch 60°C / 2h, bamboo fiber 80°C / 4h, wood powder 70°C / 3h), high-speed mixing (800 r / min, 5 minutes), extrusion (150°C, 50 r / min), film blowing (160°C, thickness 0.03 mm), heat sealing (120°C, 0.5 seconds). Comparative Example 3 Raw material composition (mass parts) (improved by mixing according to the method disclosed in publication numbers CN114196145A and CN118852855A): bamboo fiber 3 parts (CN118852855A drying process), polyvinyl alcohol 15 parts, polylactic acid 20 parts, polyethylene terephthalate 10 parts, starch 8 parts, calcium carbonate 5 parts (unmodified), chitosan 3 parts (unacetylated), glycerol 5 parts, antioxidant 4 parts.

[0024] Preparation process: combine the methods disclosed in publication numbers CN114196145A and CN118852855A, stirring (130°C, 70 r / min, 25 minutes), drying (bamboo fiber 90°C / 5h), extrusion (160°C, 80 r / min), film blowing (170°C, thickness 0.04 mm), heat sealing (130°C, 1 second). III. The detection results are shown in the following table: Based on the table detection results, the degradable bamboo fiber express packaging bags of embodiments 1-3 are significantly better than comparative examples 1-3 in various key performance indicators. In terms of mechanical properties, the tensile strength (28.5-33.8 MPa), elongation at break (255%-292%), and puncture resistance (8.5-10.1 N) of the embodiments are respectively increased by 43.8%, 57.8%, and 74.1% compared to the highest value of the comparative examples, which can better resist stretching, impact, and puncture damage during express delivery; the heat sealing strength (4.8-5.7 N / 15 mm) is increased by 78.1% compared to the highest value of the comparative examples, ensuring that the packaging bag is firmly sealed and not easily cracked. In terms of degradation performance, the 60-day degradation rate (68.2%-75.8%) of the embodiments is increased by 67.3% compared to the highest value of the comparative examples, which can quickly degrade in the natural environment and avoid white pollution. The overall data shows that the application realizes the synergistic optimization of material mechanical properties and degradation performance through exclusive pretreatment / modification of raw materials and precise process control, fully meeting the actual application requirements of express packaging.

[0025] Although embodiments of the application have been shown and described, it is to be understood that the application is not limited to the details of the foregoing embodiment, and that various changes in the form and details thereof can be made without departing from the spirit and scope of the application. The scope of the application is defined by the appended claims and their equivalents.

Claims

1. A biodegradable bamboo fiber express packaging bag, characterized in that: By mass parts, consisting of: pretreated bamboo fiber 32~42 parts, polybutylene succinate 22~28 parts, modified nano calcium carbonate 9~14 parts, polycaprolactone 12~16 parts, acetylated chitosan 6~11 parts, tributyl citrate 4~7 parts, doped titanium dioxide 2.5~4.5 parts, ethylene-vinyl acetate copolymer 6~9 parts, maleic anhydride grafted polyethylene 4~6 parts, antioxidant 1010 1.5~2.5 parts; The preparation process of the pretreated bamboo fiber is as follows: the bamboo fiber is placed in a sodium hydroxide solution with a mass concentration of 5.5~7.5%, soaked at a temperature of 65~75℃ for 2.2~2.8 hours, washed with deionized water until the pH value is 7.0±0.2, then placed in a silane coupling agent KH-560 ethanol solution with a mass concentration of 3.5~4.5%, stirred at a temperature of 52~58℃ and a rotation speed of 300~350r / min for 1.2~1.8 hours, filtered after the reaction, dried at a temperature of 85~95℃ for 4~6 hours, and the pretreated bamboo fiber is obtained.

2. The degradable bamboo fiber express packaging bag according to claim 1, characterized in that: The preparation process of the modified nano calcium carbonate is as follows: nano calcium carbonate is added to deionized water, ultrasonic dispersion is carried out for 15~20 minutes to obtain a suspension with a mass concentration of 8~12%, stearic acid accounting for 3~5% of the mass of nano calcium carbonate is added, stirred at a temperature of 70~80℃ and a rotation speed of 250~300r / min for 1.5~2.5 hours, centrifuged after the reaction, dried at a temperature of 100~110℃ for 3~4 hours, and the modified nano calcium carbonate is obtained by crushing through a 200~300 mesh sieve.

3. The degradable bamboo fiber express packaging bag according to claim 1, characterized in that: The preparation process of the acetylated chitosan is as follows: chitosan is dissolved in an acetic acid solution with a mass concentration of 2~3% to obtain a chitosan solution with a mass concentration of 5~8%, acetic anhydride accounting for 10~15% of the mass of chitosan is added, stirred at a temperature of 40~50℃ and a rotation speed of 200~250r / min for 2~3 hours, the pH value is adjusted to 7.0±0.2 using a sodium hydroxide solution with a mass concentration of 5~8% after the reaction, the precipitate is separated by filtration, washed with deionized water for 3~5 times, and vacuum dried at a temperature of 60~70℃ for 5~7 hours to obtain the acetylated chitosan.

4. The degradable bamboo fiber express packaging bag according to claim 1, characterized in that: The preparation process of the doped titanium dioxide is as follows: tetrabutyl titanate is dissolved in anhydrous ethanol to obtain a tetrabutyl titanate ethanol solution with a mass concentration of 15~20%, zinc nitrate accounting for 2~4% of the mass of tetrabutyl titanate is added, the pH value is adjusted to 2.0±0.2 by adding a hydrochloric acid solution with a mass concentration of 1~2% dropwise after stirring uniformly, hydrolysis is carried out at a temperature of 60~70℃ for 3~4 hours, the sol is formed, aging is carried out at a temperature of 80~90℃ for 12~16 hours, calcination is carried out at a temperature of 500~600℃ for 2~3 hours, the doped titanium dioxide is obtained by crushing through a 300~400 mesh sieve after cooling.

5. The degradable bamboo fiber express packaging bag according to claim 1, characterized in that: The volume ratio of ethanol to deionized water in the silane coupling agent KH-560 ethanol solution is 9:

1.

6. A method for preparing a biodegradable bamboo fiber express packaging bag, for preparing the express packaging bag according to any one of claims 1-5, characterized in that: The method comprises the following steps: S1. Each raw material is weighed according to the mass fraction, the modified nano calcium carbonate and the doped titanium dioxide are put into a plasma treatment instrument, argon is introduced as a protective gas, surface activation treatment is carried out under the conditions of a treatment power of 220-280 W and a treatment time of 35-55 minutes; this step further improves the surface activity of the inorganic filler through plasma activation, and solves the problem of weak combination of the inorganic filler with the organic phase; S2. The modified nano calcium carbonate, the doped titanium dioxide, polybutylene succinate, polycaprolactone, ethylene-vinyl acetate copolymer and maleic anhydride grafted polyethylene treated in S1 are put into a high-speed mixer, mixed at a speed of 850-950 r / min and a temperature of 85-95℃ for 18-22 minutes, then acetylated chitosan and tributyl citrate are added, the speed is adjusted to 1050-1150 r / min and the temperature is adjusted to 95-105℃, and the mixture is continuously mixed for 22-28 minutes to obtain a premix; S3. The pretreated bamboo fibers are placed in a vacuum drying oven and dried at a temperature of 110-115℃ and a vacuum degree of -0.085 to -0.088 MPa for 3.5-4.5 hours to remove the internal moisture of the fibers; S4. The premix obtained in S2 and the pretreated bamboo fibers dried in S3 are added to a twin-screw extruder, the screw speed is set to 160-190 r / min, the feeding speed is 9-11 kg / h, the temperature of each section of the extruder is as follows: zone 1, 142-148℃; zone 2, 162-168℃; zone 3, 178-182℃; zone 4, 182-188℃; and the die temperature is 178-182℃, and the molten blend is extruded, water-cooled and pelletized to obtain a plastic master batch; S5. The plastic master batch is placed in a hot air circulating drying oven and dried at a temperature of 82-88℃ for 2.2-2.8 hours to remove the residual moisture of the master batch; S6. The dried plastic master batch is added to a film blowing machine, the screw speed is set to 65-75 r / min, the temperature of each section of the cylinder is as follows: zone 1, 152-158℃; zone 2, 168-172℃; zone 3, 172-178℃; and the die temperature is 168-172℃, the blow ratio is controlled at 2.8-3.2, the drawing speed is 6-7 m / min, and a film with a thickness of 0.05-0.07 mm is blown; S7. The film is wound and sent to a bag making machine, and a bag is made by heat sealing according to the preset size, the heat sealing temperature is set to 135-145℃, the heat sealing pressure is 0.35-0.45 MPa, and the heat sealing time is 1.2-1.8 seconds, and the bag is punched after being made to obtain a degradable bamboo fiber express packaging bag.

7. The method of claim 6, wherein: In S1, the argon flow of the plasma treatment instrument is controlled at 12-18 sccm, and the material is turned over once every 10-15 minutes during the treatment process to ensure uniform surface activation of the material.

8. The method of claim 6, wherein: In S2, the stirring paddle of the high-speed mixer is a double-layer spiral structure, the gap between the stirring paddle and the inner wall of the mixer is controlled at 3-4 mm, and the temperature is raised in stages during the mixing process, and the temperature rising rate is 2-3℃ / min.

9. The method of claim 6, wherein: The die of the film blowing machine in the S6 is a ring-shaped gradual change die, the die gap is controlled at 0.9-1.1 mm, the cold air temperature of the cold air ring at the die outlet is controlled at 15-20 DEG C, and the wind speed uniformity deviation is not more than ±0.5 m / s.

10. The method of claim 6, wherein: The automatic deviation correcting device of the bag making machine in the S7 adopts a photoelectric induction type, the deviation correcting response time is not more than 0.5 seconds, the tension control system adopts a magnetic powder clutch, and the tension control precision is ±3%.

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