A modified plant fiber-containing degradable carton and a method for preparing the same

Abstract

The application discloses a modified plant fiber-containing degradable carton and a preparation method thereof, and relates to the technical field of carton production. The modified plant fiber-containing degradable carton is formed by splicing corrugated paperboards, and the preparation raw materials of the corrugated paperboard include the following components in parts by mass: modified plant fiber 45-60 parts, paper pulp 25-35 parts, biodegradable adhesive 5-10 parts, filler 5-15 parts, reinforcing agent 1-5 parts, waterproof agent 0.5-3 parts and deionized water 90-110 parts. Through the synergistic modification of alkali treatment and a special interface coupling agent, the hydrophilic hydroxyl groups on the surface of the natural plant fiber are effectively hydrophobized, the interface compatibility and dispersion uniformity between the fiber and the paper pulp matrix are significantly improved, the overall compressive strength and structural stability of the carton are greatly improved, and the problem of mechanical property reduction caused by directly using the natural plant fiber is overcome.

Description

Technical Field

[0001] This invention relates to the field of cardboard box production technology, specifically to a biodegradable cardboard box containing modified plant fibers and its preparation method. Background Technology

[0002] With increasingly stringent environmental regulations and growing consumer awareness of environmental sustainability, the logistics packaging industry has an increasingly urgent need for biodegradable and renewable materials. Natural plant fibers are widely available and biodegradable, making them an ideal material to replace some traditional wood pulp and reduce environmental footprint.

[0003] However, directly applying natural plant fibers to the production of corrugated cardboard for cartons presents significant technical bottlenecks. The surface of natural plant fibers is rich in polar hydroxyl groups, resulting in extremely high hydrophilicity. This leads to severe interfacial compatibility issues between the fibers and the hydrophobic pulp fibers that make up the cardboard matrix, as well as commonly used adhesives. These interfacial defects cause uneven dispersion of the plant fibers within the pulp matrix, resulting in weak bonding with the matrix and adhesives. Consequently, the mechanical properties of the finished cartons are significantly reduced, making them prone to collapse during logistics transportation. Simultaneously, delamination between cardboard layers is likely to occur, and due to the inherent hydrophilicity of the fibers, the cartons also exhibit poor water resistance and moisture resistance. These defects make it difficult for cartons containing unmodified natural plant fibers to meet the stringent strength requirements of actual logistics packaging, severely limiting their large-scale commercial application.

[0004] Therefore, there is an urgent need to develop a new type of cardboard box and its preparation method that can fully utilize the environmental advantages of natural plant fibers while overcoming their inherent defects through effective technical means, so that the final product has both good mechanical properties and durability. Summary of the Invention

[0005] The purpose of this invention is to address the problems in existing technologies where natural plant fibers, due to their strong surface hydrophilicity and poor interfacial compatibility with pulp matrix and adhesives, result in poor mechanical properties and water resistance in the prepared cartons. This invention provides a biodegradable carton containing modified plant fibers and its preparation method. This method aims to fully utilize the environmentally friendly and biodegradable advantages of natural plant fibers through effective fiber modification and process optimization, while ensuring that the final carton product possesses the mechanical strength and durability required for logistics packaging.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A biodegradable cardboard box containing modified plant fibers, wherein the biodegradable cardboard box is formed by splicing corrugated cardboard, and the raw materials for preparing the corrugated cardboard include the following components by weight: 45-60 parts modified plant fibers, 25-35 parts pulp, 5-10 parts biodegradable adhesive, 5-15 parts filler, 1-5 parts reinforcing agent, 0.5-3 parts waterproofing agent, and 90-110 parts deionized water;

[0008] The modified plant fiber is a natural plant fiber that has been treated with alkali and modified with an interface coupling agent.

[0009] The structure of the interfacial coupling agent is as follows: .

[0010] Furthermore, the natural plant fiber is selected from at least one of wood fiber, bamboo fiber, and straw fiber.

[0011] Furthermore, the method for preparing the modified plant fiber is as follows:

[0012] a. Alkali treatment: Crush natural plant fibers to 40-80 mesh, add them to sodium hydroxide solution, stir at 60-80℃ for 2-4 hours, filter after soaking, wash with deionized water until neutral, and dry at 80-105℃ until the moisture content is less than 3% to obtain alkali-treated fibers.

[0013] b. Coupling agent activation: Dissolve the interfacial coupling agent in anhydrous ethanol aqueous solution to prepare a modified solution, adjust the pH of the solution to 4-6, and hydrolyze and activate it at room temperature for 30-60 minutes;

[0014] c. Surface modification: Add the alkali-treated fiber to the modification solution in step b, heat to 50-70℃, stir and react for 3-5 hours to allow the interfacial coupling agent to fully dehydrate and condense with the hydroxyl groups on the fiber surface.

[0015] d. Post-processing: After the reaction is complete, the fiber is filtered out, and the residual coupling agent is removed by washing with anhydrous ethanol. Finally, it is vacuum dried at 100-110℃ to obtain the modified plant fiber.

[0016] The main function of plant fiber modification in this invention is to address the poor interfacial compatibility between natural plant fibers and hydrophobic pulp matrices and adhesives, caused by the high hydroxyl content and strong hydrophilicity of their surface. This is achieved through alkali treatment and interfacial coupling agent modification. By allowing the interfacial coupling agent to fully dehydrate and condense with the hydroxyl groups on the fiber surface, the modification process effectively improves the fiber dispersion uniformity and enhances bonding strength. This overcomes the defects of direct use of natural plant fibers, such as decreased mechanical properties of cardboard boxes, easy delamination, and poor water resistance, ensuring that degradable cardboard boxes are environmentally friendly while possessing sufficient strength to meet logistics packaging requirements.

[0017] Furthermore, the mass fraction of the sodium hydroxide solution in step a is 5%-10%.

[0018] Furthermore, in step b, the mass fraction of the modified solution is 2%-5%, and the reagent used to adjust the pH is glacial acetic acid.

[0019] Furthermore, the pulp is at least one of wood pulp, straw pulp, bamboo pulp, and recycled pulp.

[0020] Furthermore, the biodegradable adhesive is at least one of polylactic acid-based adhesive, starch-based adhesive, and chitosan-based adhesive.

[0021] Furthermore, the filler is at least one of nano-silica, talc, and calcium carbonate.

[0022] Furthermore, the reinforcing agent is at least one of nanocellulose whiskers, carboxymethyl cellulose, and chitosan.

[0023] Furthermore, the waterproofing agent is at least one of paraffin emulsion and alkyl alkenyl succinic anhydride.

[0024] A method for preparing a biodegradable cardboard box containing modified plant fibers includes the following steps:

[0025] S1. Raw material pretreatment: The modified plant fiber and pulp are crushed to 60-100 mesh and dried to a moisture content of less than 3% for later use; the filler and reinforcing agent are passed through an 80-120 mesh sieve to remove impurities for later use.

[0026] S2. Pulp dispersion: The pretreated pulp is added to the deionized water and stirred to disperse it into a uniform pulp suspension to obtain a pulp suspension;

[0027] S3. Mixing and Preparation: Pretreated modified plant fibers, fillers, and reinforcing agents are added sequentially to the pulp suspension, and the mixture is stirred at a constant temperature of 300-500 r / min for 30-60 minutes at 30-50℃ to obtain a premixed pulp; then the biodegradable adhesive and waterproofing agent are added to the premixed pulp, and stirring is continued for 20-40 minutes until all components are mixed evenly to obtain a mixed pulp;

[0028] S4. Corrugated board preparation: The mixed pulp is formed into base paper, and the thickness of the base paper is controlled to be 0.3-0.8 mm; the base paper is corrugated and bonded with the biodegradable adhesive at a bonding temperature of 80-100℃, a pressure of 0.3-0.6 MPa, a bonding time of 10-20 minutes, and then creasing is performed to obtain corrugated board;

[0029] S5. Carton forming: The corrugated cardboard is die-cut and creasing according to the preset size, and the edge waste is removed. It is then assembled by folding, nailing or gluing processes, and left to stand and cure for 2-4 hours to obtain a degradable carton containing modified plant fibers.

[0030] Furthermore, in step S3, the high-speed stirring process is stopped for 5 minutes every 20 minutes to prevent component agglomeration;

[0031] Furthermore, the biodegradable adhesive needs to be preheated to 30-40°C before being added to improve the adhesive effect.

[0032] Furthermore, in step S4, the amount of biodegradable adhesive applied is 8-15 g / m³. 2 .

[0033] Furthermore, the environmental conditions for static curing in step S5 are: temperature 20-30℃, relative humidity 40%-60%, and drying time 2-4 hours. After drying, the bonding strength of the cardboard box needs to be tested to ensure that there is no delamination or cracking.

[0034] Furthermore, the aforementioned biodegradable cardboard box containing modified plant fibers can be made from agricultural and forestry processing waste.

[0035] This invention addresses the core technical problems of poor interfacial compatibility between natural plant fibers and pulp matrix and adhesives due to their strong hydrophilicity, leading to decreased mechanical properties, easy delamination, and poor water resistance in cardboard boxes. This is achieved through the synergistic effects of the various formulation components, addressing issues from multiple dimensions including fiber interface modification, matrix forming, and performance enhancement. Specifically, the modified plant fibers undergo alkali treatment to remove surface impurities and etch hydroxyl groups. Then, a dedicated interfacial coupling agent is used to dehydrate and condense the fiber hydroxyl groups, achieving hydrophobic modification. This improves the fiber's dispersion compatibility with the hydrophobic pulp matrix and enhances the bond between the fiber and the matrix, laying the foundation for the cardboard box's mechanical properties. The pulp, acting as the matrix skeleton, forms a complementary fiber network with the modified plant fibers, improving overall formability and structural strength. The biodegradable adhesive combines degradability and adhesion, significantly improving the interfacial bonding with the modified fibers. Combined with a preheating process, this further strengthens interlayer adhesion, fundamentally solving the delamination problem. Fillers fill the gaps in the fiber network. The dense cardboard structure enhances rigidity and compression resistance, while the reinforcing agent cross-links with the fiber network, further improving the tensile and tear mechanical properties of the cardboard and compensating for the strength deficiencies caused by the application of plant fibers. The waterproofing agent forms a hydrophobic layer on the surface of the fibers and cardboard, which, combined with the hydrophobicity of the modified plant fibers themselves, doubles the water resistance and moisture-proof performance of the carton. At the same time, deionized water serves as a dispersion medium to ensure that the components are evenly dispersed during the preparation process, avoiding agglomeration and allowing each functional component to play its full role. Each component is precisely proportioned by weight, with modified plant fibers as the core functional phase, pulp as the matrix phase, adhesives as the connecting phase, fillers and reinforcing agents as the strengthening phase, and waterproofing agent as the protective phase. This multi-phase synergy constructs a corrugated cardboard system that combines good biodegradability, excellent interfacial bonding, high strength mechanical properties, and water resistance. The resulting degradable cardboard box fully utilizes the environmental advantages of natural plant fibers while meeting the actual requirements of logistics packaging for strength and durability.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] 1. Significantly improved mechanical properties: Through synergistic modification by alkali treatment and a proprietary interface coupling agent, the hydrophilic hydroxyl groups on the surface of natural plant fibers are effectively hydrophobized, significantly improving the interfacial compatibility and dispersion uniformity between the fibers and the pulp matrix. This greatly enhances the overall compressive strength and structural stability of the carton, overcoming the problem of decreased mechanical properties caused by directly using natural plant fibers.

[0038] 2. Enhanced adhesion and anti-delamination ability: The interfacial bonding between the modified plant fiber and the biodegradable adhesive is greatly improved. Combined with the optimized preheating and bonding process, the problem of easy delamination between layers is fundamentally solved, and a strong bond is achieved between the corrugated cardboard face paper, core paper and liner paper, ensuring that the carton maintains its structural integrity during logistics transportation.

[0039] 3. Significantly improved water and moisture resistance: The modified plant fiber itself has enhanced hydrophobicity, and combined with the hydrophobic protective layer formed on the surface of the fiber and the cardboard by the waterproofing agent, the water and moisture resistance of the carton is improved in two ways. This allows the carton to maintain a high strength retention rate in humid environments, effectively overcoming the defect of poor water resistance caused by the excessive hydrophilicity of natural plant fibers. Detailed Implementation

[0040] The following will provide a clear and complete description of the technical solutions of this invention. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0041] Preparation Example

[0042] Preparation of interfacial coupling agents:

[0043] ;

[0044] CAS number for raw material 1: 1135-24-6;

[0045] CAS number for raw material 2: 108-24-7;

[0046] Under nitrogen protection, 5.00 g of raw material 1 and 157 mg of 4-dimethylaminopyridine were first added to the reaction flask. Then, 50 mL of anhydrous dichloromethane was added using a syringe, and stirring was started. The reaction flask was placed in an ice-water bath to cool to 0°C. After the system cooled for 5 minutes, 7.18 mL of triethylamine was added dropwise using a dry syringe while maintaining stirring at 0°C. 3.64 mL of raw material 2 was transferred to a constant-pressure dropping funnel and slowly added to the reaction system at a rate of approximately 1 drop / second. After the addition was complete, the ice-water bath was removed, and the reaction solution was allowed to naturally warm to room temperature. The mixture was then stirred vigorously for 6 hours under a nitrogen atmosphere. After the reaction was completed, the reaction solution was cooled to 0°C, and the reaction was quenched by adding 1 M dilute hydrochloric acid aqueous solution very slowly. The mixture was transferred to a separatory funnel, and the organic phase was collected. The aqueous phase was extracted with dichloromethane, and all organic phases were combined. The organic layer was washed successively with deionized water and saturated brine. The washed organic phase was transferred to an Erlenmeyer flask, dried with an appropriate amount of anhydrous sodium sulfate, filtered to remove the desiccant, and the filtrate was collected in a pre-weighed round-bottom flask. The filtrate was concentrated under reduced pressure using a rotary evaporator to obtain a crude solid. Ethyl acetate was added to the flask containing the crude product and heated to a gentle boil to dissolve it completely. Then, hexane was slowly added dropwise with stirring until the solution became slightly turbid. Heating was stopped, and the mixture was allowed to cool naturally at room temperature for 2 hours to crystallize. Then, it was placed in a refrigerator at 4°C overnight. The next day, the precipitated crystals were collected by vacuum filtration through a Buchner funnel. The filter cake was washed twice with a small amount of ice-cold hexane / ethyl acetate mixed solvent. Finally, the filter cake was dried in a vacuum drying oven to constant weight to obtain 5.15 g of intermediate.

[0047] ;

[0048] CAS number for raw material 3: 919-30-2;

[0049] Under nitrogen protection, 5.15 g of the intermediate, 5.01 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 3.54 g of 1-hydroxybenzotriazole were added to the reaction flask. The flask was then resealed and purged with nitrogen once more. 80 mL of anhydrous dichloromethane was injected using a syringe, and stirring was started to suspend the solids in a uniform state. The reaction flask was placed in an ice-water bath to cool to 0 °C, and after stirring for 10 minutes, 9.49 mL of [amount missing] ... N,N-Diisopropylethylamine was stirred continuously at this temperature for 30 minutes. Then, 5.31 mL of raw material 3 was dissolved in 20 mL of anhydrous dichloromethane and added dropwise to the reaction flask over 20 minutes using a constant-pressure dropping funnel. After the addition was complete, the ice-water bath was removed, and the reaction system was allowed to react at room temperature with continuous stirring for 12 hours. After the reaction was complete, the reaction solution was diluted with 100 mL of cold dichloromethane, and the mixture was transferred to a separatory funnel and quickly washed sequentially with 0°C ice-saturated sodium bicarbonate aqueous solution, ice water, and ice-saturated saline solution. The organic phase was separated and allowed to stand immediately after each shaking. The organic phase was collected and transferred to an Erlenmeyer flask, dried with anhydrous sodium sulfate, and filtered through a sand core funnel lined with diatomaceous earth to remove the desiccant. The filter cake was washed with a small amount of dichloromethane, and the filtrates were combined to obtain the crude product. The crude product was subjected to rapid column chromatography using neutral silica gel pretreated with triethylamine, with petroleum ether / ethyl acetate gradient elution. The target component was collected, the solvent was removed under reduced pressure, and finally the mixture was dried under high vacuum for 4 hours on a vacuum oil pump to obtain 6.93 g of interfacial coupling agent.

[0050] Structural assessment:

[0051] NMR of interfacial coupling agents 1 HNMR(Chloroform-d)δ7.50(dd,1H),7.27-7.11(m,2H),7.02(d,1H),6.67(d,1H),6.32( t,1H),3.82(dd,9H),3.17(m,2H),2.38(s,3H),1.59(tt,2H),1.21(t,9H),0.75(t,2H).

[0052] Example 1

[0053] Preparation of a biodegradable cardboard box containing modified plant fibers:

[0054] 1. Preparation of modified plant fibers:

[0055] a. Alkali treatment: The bamboo fiber is crushed to 60 mesh and added to a sodium hydroxide solution with a mass fraction of 8%. The solution is stirred at a constant temperature of 70°C for 3 hours. After soaking, the solution is filtered and washed with deionized water until neutral. The solution is then dried at 90°C until the moisture content is less than 3% to obtain alkali-treated fiber.

[0056] b. Coupling agent activation: Dissolve the interface coupling agent in anhydrous ethanol aqueous solution to prepare a modified solution with a mass fraction of 3%, adjust the pH of the solution to 5 with glacial acetic acid, and hydrolyze and activate it for 45 minutes at room temperature;

[0057] c. Surface modification: The alkali-treated fiber is added to the modification solution in step b, heated to 60°C, and stirred for 4 hours to allow the interfacial coupling agent to fully dehydrate and condense with the hydroxyl groups on the fiber surface.

[0058] d. Post-processing: After the reaction is complete, the fiber is filtered out, and the residual coupling agent is removed by washing with anhydrous ethanol. Finally, it is vacuum dried at 105°C to obtain the modified plant fiber.

[0059] 2. Raw material components by weight:

[0060] 50 parts of modified plant fiber: the modified plant fiber prepared above;

[0061] 30 parts of pulp: bamboo pulp;

[0062] 8 parts of biodegradable adhesive: polylactic acid-based adhesive;

[0063] 10 parts of filler: nano-silica;

[0064] Three parts of reinforcing agent: nano-cellulose whiskers;

[0065] Waterproofing agent 1.5 parts: paraffin emulsion;

[0066] 100 portions of deionized water.

[0067] 3. Preparation method:

[0068] S1. Raw material pretreatment: The modified plant fiber and pulp are crushed to 80 mesh using a pulverizer and dried at 85°C until the moisture content is less than 3% for later use; the nano silica filler and nano cellulose whisker reinforcing agent are passed through a 100-mesh sieve to remove impurities for later use; the polylactic acid adhesive is preheated to 35°C for later use.

[0069] S2. Pulp dispersion: The pretreated pulp is added to deionized water and stirred and dispersed at 400 r / min for 40 minutes at 40℃ to form a uniform pulp suspension.

[0070] S3. Mixing and Modification: Pretreated modified plant fibers, nano-silica fillers, and nano-cellulose whisker reinforcing agents are added sequentially to the pulp suspension. The mixture is stirred at 40°C and 400 r / min for 50 minutes to obtain a premixed pulp. During the stirring process, the machine is stopped every 20 minutes and manually stirred for 5 minutes to prevent component agglomeration. Then, preheated polylactic acid adhesive and paraffin emulsion waterproofing agent are added to the premixed pulp, and stirring is continued for 30 minutes until all components are mixed evenly to obtain a mixed pulp.

[0071] S4. Corrugated board preparation: The mixed pulp is fed into a paper forming machine for sheet forming to produce a base paper with a thickness of 0.5 mm. The base paper is then heated and pressed by corrugating rollers to form B-type corrugations. Subsequently, the polylactic acid-based adhesive is applied to the top of the corrugations at an application rate of 12 g / m². 2 It is then bonded to another layer of base paper at a temperature of 90℃ and a pressure of 0.4MPa for 15 minutes, and then subjected to creasing treatment to obtain corrugated cardboard;

[0072] S5. Carton forming: The corrugated cardboard is die-cut and creasing according to the preset size, and the edge waste is removed. It is then folded and glued together by an automatic carton gluing machine. The formed carton blank is placed in an environment with a temperature of 25°C and a relative humidity of 50% and left to cure for 3 hours to obtain a degradable carton containing modified plant fibers.

[0073] Example 2-Example 3

[0074] The preparation of a biodegradable cardboard box containing modified plant fiber is carried out by referring to the preparation method in Example 1, except that the mass fractions of each raw material in the components are replaced, and other operations are kept the same as in Example 1. The specific mass fractions of the raw materials are shown in the table below.

[0075] Table 1. Mass proportions of raw materials in Examples 2-3

[0076]

[0077] Comparative Example 1

[0078] The preparation of a biodegradable cardboard box containing modified plant fibers is carried out by referring to the preparation method in Example 1, except that the modified plant fibers are replaced with natural plant fibers, and other operations are the same as in Example 1.

[0079] Comparative Example 2

[0080] The preparation of a biodegradable cardboard box containing modified plant fibers is carried out in accordance with the preparation method in Example 1. The natural plant fibers are only treated with alkali, without subsequent coupling agent activation, surface modification and post-treatment. Other operations are the same as in Example 1.

[0081] Comparative Example 3

[0082] The preparation of a biodegradable cardboard box containing modified plant fibers is carried out by referring to the preparation method in Example 1, except that the interfacial coupling agent in the natural plant fiber modification process is replaced with silane coupling agent KH550, and other operations are the same as in Example 1.

[0083] Comparative Example 4

[0084] The preparation of a biodegradable cardboard box containing modified plant fibers is carried out according to the preparation method in Example 1, without adding the reinforcing agent, and the other operations are the same as in Example 1.

[0085] Performance testing

[0086] 1. Cardboard box compression strength test: According to standard GB / T 4857.4-2008 "Packaging – Basic Tests for Transport Packaging – Part 4: Compression and Stacking Tests Using a Compression Testing Machine", the compression strength of the cardboard boxes prepared in the examples and comparative examples was tested, and the results are shown in the table below. kN

[0087] 2. Adhesion Performance Test: According to standard GB / T 6548-2011 "Determination of Adhesive Strength of Corrugated Board", 25mm × 100mm samples were cut from the corrugated board. The samples must contain the complete interlayer structure of the linerboard, core paper, and liner. A peel test device was used to test the adhesive strength of the samples, and any delamination or core paper breakage was observed. The results are shown in the table below. N / m

[0088] 3. Water resistance and moisture resistance test of cardboard boxes: According to standard GB / T 4857.9-2008 "Basic tests for transport packaging - Part 9: Spray test method", the cardboard boxes prepared in the examples and comparative examples were placed in a spray test chamber to simulate a natural rain environment. After spraying, the cardboard boxes were taken out and the surface moisture was drained. The compressive strength of the empty boxes was tested immediately, and the compressive strength retention rate after immersion in water was calculated. The results are shown in the table below.

[0089] Table 2. Performance Test Data Results

[0090]

[0091] As can be seen from the data in Table 2, the examples using the complete modification process and formulation system of this invention are significantly superior to the comparative examples in terms of compressive strength, adhesion, and water and moisture resistance. Specifically, the example group exhibits excellent mechanical strength, strong interlayer adhesion without delamination, and maintains a high strength retention rate even after immersion in water. In contrast, the unmodified natural plant fibers have the worst performance in all aspects. Although alkali treatment or the use of conventional silane coupling agents can improve the performance to some extent, it is still significantly insufficient. While the lack of reinforcing agents results in acceptable adhesion, the mechanical strength is greatly reduced. This indicates that the modified plant fiber formulation and preparation process of this invention can effectively solve the core problems of poor interfacial compatibility, decreased mechanical properties, and insufficient water resistance caused by the strong hydrophilicity of natural plant fibers, enabling biodegradable cartons to possess both environmental protection characteristics and comprehensive performance that meets the requirements of logistics packaging.

[0092] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A biodegradable cardboard box containing modified plant fibers, characterized in that, The degradable cardboard box is formed by splicing corrugated cardboard. The raw materials for preparing the corrugated cardboard include the following components by weight: 45-60 parts modified plant fiber, 25-35 parts pulp, 5-10 parts biodegradable adhesive, 5-15 parts filler, 1-5 parts reinforcing agent, 0.5-3 parts waterproofing agent, and 90-110 parts deionized water. The modified plant fiber is a natural plant fiber that has been treated with alkali and modified with an interface coupling agent. The structure of the interfacial coupling agent is as follows: .

2. The biodegradable cardboard box containing modified plant fibers according to claim 1, characterized in that, The natural plant fiber is selected from at least one of wood fiber, bamboo fiber, and straw fiber.

3. A biodegradable cardboard box containing modified plant fibers according to claim 1, characterized in that, The method for preparing the modified plant fiber is as follows: a. Alkali treatment: Crush natural plant fibers to 40-80 mesh, add them to sodium hydroxide solution, stir at 60-80℃ for 2-4 hours, filter after soaking, wash with deionized water until neutral, and dry at 80-105℃ until the moisture content is less than 3% to obtain alkali-treated fibers. b. Coupling agent activation: Dissolve the interfacial coupling agent in anhydrous ethanol aqueous solution to prepare a modified solution, adjust the pH of the solution to 4-6, and hydrolyze and activate it at room temperature for 30-60 minutes; c. Surface modification: Add the alkali-treated fiber to the modification solution in step b, heat to 50-70℃, stir and react for 3-5 hours to allow the interfacial coupling agent to fully dehydrate and condense with the hydroxyl groups on the fiber surface. d. Post-processing: After the reaction is complete, the fiber is filtered out, and the residual coupling agent is removed by washing with anhydrous ethanol. Finally, it is vacuum dried at 100-110℃ to obtain the modified plant fiber.

4. A biodegradable cardboard box containing modified plant fibers according to claim 1, characterized in that, The pulp is at least one of wood pulp, straw pulp, bamboo pulp, and recycled pulp.

5. A biodegradable cardboard box containing modified plant fibers according to claim 1, characterized in that, The biodegradable adhesive is at least one of polylactic acid-based adhesive, starch-based adhesive, and chitosan-based adhesive.

6. A biodegradable cardboard box containing modified plant fibers according to claim 1, characterized in that, The filler is at least one of nano-silica, talc, and calcium carbonate.

7. A biodegradable cardboard box containing modified plant fibers according to claim 1, characterized in that, The reinforcing agent is at least one of nano-cellulose whiskers, carboxymethyl cellulose, and chitosan; The waterproofing agent is at least one of paraffin emulsion and alkyl alkenyl succinic anhydride.

8. A method for preparing a biodegradable cardboard box containing modified plant fibers according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Raw material pretreatment: The modified plant fiber and pulp are crushed to 60-100 mesh and dried to a moisture content of less than 3% for later use; the filler and reinforcing agent are passed through an 80-120 mesh sieve to remove impurities for later use. S2. Pulp dispersion: The pretreated pulp is added to the deionized water and stirred to disperse it into a uniform pulp suspension to obtain a pulp suspension; S3. Mixing and Preparation: Pretreated modified plant fibers, fillers, and reinforcing agents are added sequentially to the pulp suspension, and the mixture is stirred at a constant temperature of 300-500 r / min for 30-60 minutes at 30-50℃ to obtain a premixed pulp; then the biodegradable adhesive and waterproofing agent are added to the premixed pulp, and stirring is continued for 20-40 minutes until all components are mixed evenly to obtain a mixed pulp; S4. Corrugated board preparation: The mixed pulp is formed into base paper, and the thickness of the base paper is controlled to be 0.3-0.8 mm; the base paper is corrugated and bonded with the biodegradable adhesive at a bonding temperature of 80-100℃, a pressure of 0.3-0.6 MPa, a bonding time of 10-20 minutes, and then creasing is performed to obtain corrugated board; S5. Carton forming: The corrugated cardboard is die-cut and creasing according to the preset size, and the edge waste is removed. It is then assembled by folding, nailing or gluing processes, and left to stand and cure for 2-4 hours to obtain a degradable carton containing modified plant fibers.

9. The method for preparing a biodegradable cardboard box containing modified plant fibers according to claim 8, characterized in that, In step S3, the high-speed stirring process is stopped every 20 minutes for 5 minutes to prevent component agglomeration. Before adding the biodegradable adhesive, it needs to be preheated to 30-40℃ to improve the adhesive effect.

10. A method for preparing a biodegradable cardboard box containing modified plant fibers according to claim 8, characterized in that, In step S4, the amount of biodegradable adhesive applied is 8-15 g / m³. 2 ; The environmental conditions for static curing in step S5 are: temperature 20-30℃, relative humidity 40%-60%, and drying time of 2-4 hours. After drying, the bonding strength of the carton needs to be tested to ensure that there is no delamination or cracking.

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