Preservative paper preparation process constructed based on plant bionic crosslinking strategy

Abstract

The invention discloses a preservative paper preparation process constructed based on a plant bionic crosslinking strategy, which comprises the following steps: S1, dissolving polyvinyl alcohol in deionized water at 93-97 DEG C to form a homogeneous polyvinyl alcohol solution with the concentration of 1.5-3 wt%; s2, adding borax into the solution obtained in the step S1, and stirring at 88-92 DEG C at the stirring speed of 400-600r / min for 25-35 minutes to form a borax mediated pre-crosslinking system; s3, under the continuous alkaline condition, urea is added into the pre-crosslinking system obtained in the S2, stirring continues to be conducted for 25-35 min, and a PVA-urea hydrogen bond three-dimensional compact grid structure is constructed; and S4, sizing the composite coating obtained in the step S3 on the surface of quantitative 35-45 g / m < 2 > of base paper according to the coating weight of 2.5-3.0 g / m < 2 >, and drying at 60-105 DEG C for 8-12 minutes to form the preservative paper base material with the gradient cross-linked structure. By innovating a material modification and structure reconstruction process, the barrier property bottleneck of the paper-based material is broken through, and the barrier property, oil resistance and water resistance of the paper-based material are enhanced while the environment-friendly characteristic is maintained.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomass food packaging materials, and particularly relates to a preparation process of a fresh-keeping paper constructed based on a plant bionic cross-linking strategy. Background Art

[0002] As the core protective layer for maintaining food quality, food packaging needs to have multiple barrier functions against grease, water vapor and gas. Among current mainstream packaging materials, although petroleum-based plastics have excellent barrier properties and mechanical strength, they cause environmental pollution problems due to their difficulty in biodegradation; while traditional paper-based materials have the advantages of degradability and food safety, their inherent pore structure leads to significant hygroscopic characteristics, seriously restricting the food preservation effect.

[0003] The solution of the plastic film lamination composite technology used will cause the material to be difficult to recycle and have poor degradability, which does not conform to the environmental protection trend; and the inorganic coatings used are mainly through physical vapor deposition methods, but their processes are complex, the costs are high, and the coatings are brittle and easy to crack; the bio-based coatings used, although they can improve the barrier properties of the paper, have poor water resistance and insufficient mechanical strength. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a fresh-keeping paper constructed based on a plant bionic cross-linking strategy and its application, solving the above technical problems existing in the prior art.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A fresh-keeping paper constructed based on a plant bionic cross-linking strategy, comprising the following steps:

[0007] S1. Dissolve polyvinyl alcohol in deionized water at 93 - 97 °C to form a homogeneous polyvinyl alcohol solution with a concentration of 1.5 - 3 wt%.

[0008] S2. Add borax to the solution obtained in S1, and stir at a speed of 400 - 600 r / min for 25 - 35 min at 88 - 92 °C to form a borax-mediated pre-crosslinking system.

[0009] S3. Under continuous alkaline conditions, add urea to the pre-crosslinking system obtained in S2, and continue stirring for 25 - 35 min to construct a three-dimensional dense network structure of PVA-urea hydrogen bonds.

[0010] S4. Apply the composite coating obtained in S3 to the surface of the base paper with a basis weight of 35 - 45 g / m 2 at a coating amount of 2.5 - 3.0 g / m 2 , and dry at 60 - 105 °C for 8 - 12 min to form a fresh-keeping paper substrate with a gradient cross-linking structure.

[0011] The fresh-keeping paper forms the following performance parameters:

[0012] Water vapor transmission rate ≤ 15 g / m 2 ·24 h,

[0013] Oxygen transmission rate ≤ 5 cm 3 / m 2 ·24 h·0.1 MPa,

[0014] Tensile strength ≥ 80 MPa.

[0015] Further, in the S1, the molecular weight of polyvinyl alcohol is 70,000 - 100,000, and the degree of alcoholysis is 85 - 99%.

[0016] Further, in the S2, the addition amount of borax is 0.8 - 1.2% of the mass of polyvinyl alcohol, and the pH value of the cross-linking reaction is controlled at 8.5 - 9.5.

[0017] Further, in the S3, by adding ammonia water, the alkaline condition is controlled to maintain the pH value of the system at 9.0 - 10.0.

[0018] Further, the urea accounts for 1.3 - 1.7 wt% of the mass ratio in the pre-cross-linked system of S3.

[0019] Further, in the S4, a gradient heating method is adopted, specifically including:

[0020] The first stage: drying at 60 - 70 °C for 3 - 5 min;

[0021] The second stage: drying at 80 - 90 °C for 4 - 6 min;

[0022] The third stage: drying at 95 - 105 °C for 1 - 2 min.

[0023] Further, in the S4, the base paper is prepared by mixing bleached softwood pulp and hardwood pulp in a ratio of 1:1 - 1:3, and its air permeability ≤ 3 μm / Pa·s.

[0024] Further, in the light environment with a wavelength of 550 nm, the transparency of the fresh-keeping paper ≥ 85%.

[0025] The application of the fresh-keeping paper constructed based on the plant bionic cross-linking strategy, the fresh-keeping paper is used for packaging fresh fruits and vegetables, so that the shelf life of strawberries is extended to 7 - 9 days at 25 °C and 50% RH, and the weight loss rate ≤ 5%.

[0026] The recycling method of the fresh-keeping paper constructed based on the plant bionic cross-linking strategy includes the following steps,

[0027] S501. Ultrasonically treat the used fresh-keeping paper material in deionized water at 90 - 100 °C for 10 - 20 min to separate the PVA coating from the cellulose substrate;

[0028] S502. After the recovered fiber substrate is beaten to a beating degree of 35 - 45 °SR, it is re - formed into recycled paper with a basis weight of 38 - 42 g / m 2 ².

[0029] Advantages of the present invention:

[0030] 1. Borax used in the present invention as a cross - linker forms dynamic coordination bonds with the hydroxyl groups of PVA, which can enhance the water resistance of the coating; urea binds to PVA / cellulose through hydrogen bonds, fills the microscopic pores, and reduces the oxygen / water vapor permeability; the gradient drying process adopted can simulate the drying process of plants.

[0031] 2. The principles adopted in the present invention are all bio - based raw materials, which can be degraded in the soil within 50 days (the control PE film cannot be degraded). The formed coating can recover the fibers by dissolving in hot water, and the recycling rate is greater than 90%; and the water vapor transmission rate of the bio - film barrier of the present invention is ≤15 g / m 2 ²·24 h, and the oxygen transmission rate is ≤5 cm 3 / m 2 ²·24 h·0.1 MPa, and the tensile strength is ≥80 MPa; its overall process is compatible with existing papermaking equipment and does not require complex modification.

[0032] 3. The fresh - keeping paper adopted in the present invention can be widely used for fresh food packaging, oil - rich food grease - proof paper packaging, and pharmaceutical packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art.

[0034] Figure 1 For the appearance changes of strawberries during storage in Example 1 and Control Example 1;

[0035] Figure 2 For the appearance changes of Example 2 and Control Example 2 during the soil degradation experiment;

[0036] Figure 3 For the stress - strain curves of Example 3 and Control Example 3;

[0037] Figure 4 For the tensile strength and Young's modulus diagrams of Example 3 and Control Example 3;

[0038] Figure 5 For the thermal stability experiments of Example 3 and Control Example 3;

[0039] Figure 6 Scanning electron micrographs of Example 3 and Comparative Example 3;

[0040] Figure 7 Cyclic experiment diagram of Example 4. Specific implementation mode

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0042] Example 1

[0043] The embodiment of the present invention provides a preparation method of a fresh-keeping paper constructed based on a plant bionic cross-linking strategy, and the specific steps are as follows:

[0044] S1. Prepare a polyvinyl alcohol-based solution by hydrothermal dissolution: perform gradient heating and dissolution in deionized water at 95°C to form a homogeneous polyvinyl alcohol colloidal solution; the solid content control parameter of the polyvinyl alcohol-based solution in S1 is controlled by the mass ratio of molecular weight screening type polyvinyl alcohol to deionized water during the hydrothermal dissolution process to form a critical micelle concentration solution of 2 wt%.

[0045] S2. Construct a borax-mediated cross-linking system: Gradually feed borax into the solution obtained in S1 and complete pre-cross-linking of coordination bonds under the condition of constant temperature magnetic stirring at 90°C;

[0046] S3. Urea directed assembly process: Under the control of a continuous alkaline environment, introduce urea into the cross-linking system according to the stoichiometric ratio, and construct a three-dimensional dense structure through an intermolecular hydrogen bond network;

[0047] S4. Substrate functionalization treatment: Use a coating device to apply a composite coating to the surface of the base paper in a preset amount, and achieve coating interface stabilization through a gradient drying process. The structural parameter of the substrate in S4, the base paper selects a 40 g / m 2 Quantitative substrate to ensure the uniformity of the coating interface binding.

[0048] Select small tomatoes of the same size, cut the fresh-keeping paper to an appropriate size for packaging, and store it under the conditions of 25°C and a relative humidity of 50%. [[ID=3G]]

[0049] The fresh-keeping paper forms the following performance parameters:

[0050] Water vapor transmission rate ≤ 15 g / m 2 ·24 h,

[0051] Oxygen transmission rate ≤ 5 cm 3 / m 2·24 h·0.1 MPa,

[0052] Tensile strength ≥ 80 MPa.

[0053] Example 2

[0054] S1. Dissolve polyvinyl alcohol in deionized water at 95 °C to obtain a polyvinyl alcohol solution; the molecular weight of polyvinyl alcohol is 70,000, and the degree of alcoholysis is 85%.

[0055] S2. Add 10 mg of borax to the solution prepared in S1, then keep the temperature at about 90 °C and stir at a speed of 500 r / min for 30 min. The concentration of the polyvinyl alcohol solution is 2 wt%; the pH value is controlled at 8.5 - 9.0.

[0056] S3. Add 150 mg of urea to the solution obtained in S2 and continue to stir for 30 min, and keep the solution alkaline all the time; control the alkaline condition by adding ammonia water to maintain the pH value of the system at 9.0 - 9.5.

[0057] The solution obtained in S4 is quantitatively coated on the surface of the base paper (the base paper is 40 g / m 2 ) at 2.8 g / m 2 using a gradient heating method, specifically including: the first stage: drying at 65 °C for 4 min; the second stage: drying at 80 °C for 6 min; the third stage: drying at 105 °C for 1 min to obtain the required paper-based material fresh-keeping paper.

[0058] The formed fresh-keeping paper includes the following performance parameters:

[0059] The water vapor transmission rate is 12 g / m 2 ·24 h,

[0060] The oxygen transmission rate is 4 cm 3 / m 2 ·24 h·0.1 MPa,

[0061] The tensile strength is 82.1 MPa.

[0062] Evaluate its biodegradability in soil. Cut the fresh-keeping paper into samples of 21 cm × 29.7 cm, bury the samples at a depth of about 10 cm, and take pictures at regular intervals to record the change of the surface morphology. The experiment lasts for 50 days.

[0063] Example 3

[0064] S1. Dissolve polyvinyl alcohol in deionized water at 95 °C to obtain a polyvinyl alcohol solution; the molecular weight of polyvinyl alcohol is 80,000, and the degree of alcoholysis is 90%.

[0065] S2. Add 10 mg of borax to the solution prepared in S1, then keep the temperature at about 90 °C and stir for 30 min at a speed of 500 r / min. The concentration of the polyvinyl alcohol solution is 2 wt%. Control the pH value at 9.0 - 9.5.

[0066] S3. Add 150 mg of urea to the solution obtained in S2 and continue stirring for 30 min, and keep the solution alkaline all the time; control the alkaline condition by adding ammonia water to maintain the pH value of the system at 9.5 - 10.0.

[0067] S4. Quantitatively coat the obtained solution on the surface of the base paper (40 g / m 2 ) at 2.8 g / m 2 . Then adopt the gradient heating method, specifically including: the first stage: dry at 60 °C for 5 min; the second stage: dry at 90 °C for 4 min; the third stage: dry at 95 °C for 2 min to obtain the required paper-based material fresh-keeping paper.

[0068] The formed fresh-keeping paper includes the following performance parameters:

[0069] The water vapor transmission rate is 13 g / m 2 ·24 h,

[0070] The oxygen transmission rate is 4.2 cm 3 / m 2 ·24 h·0.1 MPa,

[0071] The tensile strength is 84.2 MPa.

[0072] First, cut the paper-based composite material sample into strip specimens of standard size, and then conduct the tensile strength test. All tests are carried out under standard environmental conditions (temperature 23 ± 1 °C, relative humidity 50 ± 2%).

[0073] Example 4

[0074] S1. Dissolve polyvinyl alcohol in deionized water at 95 °C to obtain a polyvinyl alcohol solution; the molecular weight of polyvinyl alcohol is 100000 and the degree of alcoholysis is 99%.

[0075] S2. Add 10 mg of borax to the solution prepared in S1, then keep the temperature at about 90 °C and stir for 30 min at a speed of 500 r / min. The concentration of the polyvinyl alcohol solution is 2 wt%. Control the pH value at 9.0 - 9.5.

[0076] S3. Add 150 mg of urea to the solution obtained in S2 and continue stirring for 30 min, and keep the solution alkaline all the time; control the alkaline condition by adding ammonia water to maintain the pH value of the system at 9.5 - 10.0.

[0077] S4. Coating the obtained solution quantitatively at 2.8 g / m 2 on the surface of the base paper (the base paper is 40 g / m 2 ), and then adopting a gradient heating method, specifically including: the first stage: drying at 70 °C for 3 min; the second stage: drying at 85 °C for 5 min; the third stage: drying at 105 °C for 1 min to obtain the required paper-based material fresh-keeping paper.

[0078] The formed fresh-keeping paper includes the following performance parameters:

[0079] The water vapor transmission rate is 15 g / m 2 ·24 h,

[0080] The oxygen transmission rate is 5 cm 3 / m 2 ·24 h·0.1 MPa,

[0081] The tensile strength is 85.2 MPa.

[0082] The steps of the fresh-keeping paper cycle experiment are as follows: First is the mechanical cycle. The used material is oscillated and dissolved in deionized water at 95 °C to separate the PVA coating from the fiber substrate, and the recovered fiber is recombined into a paper sheet after beating.

[0083] Blank Example 1

[0084] Cut the untreated base paper into appropriate sizes, select small tomatoes of the same size for packaging, and then store them under the conditions of 25 °C and a relative humidity of 50%.

[0085] Blank Example 2

[0086] Cut the PE plastic film into samples of 21 cm × 29.7 cm, bury the samples at a depth of about 10 cm, and take pictures at regular intervals to record the changes in the surface morphology. The experiment lasts for 50 days.

[0087] Blank Example 3

[0088] Cut the untreated base paper into strip specimens of standard sizes, and then conduct tensile strength tests. All tests are carried out under standard environmental conditions (temperature 23 ± 1 °C, relative humidity 50 ± 2%).

[0089] Blank Example 4

[0090] After conditioning the untreated base paper in a constant temperature and humidity environment (23 ± 1 °C, 50 ± 2%), cut it into standard rectangular test strips, and measure the tensile strength and elastic modulus.

[0091] Blank Example 5

[0092] Cut the untreated base paper into samples with a diameter of 10 cm. Subsequently, place the samples in a constant-temperature oven and set the temperatures to 60 °C and 120 °C respectively, and maintain for 30 minutes at each temperature.

[0093] Effect evaluation experiment

[0094] (1) Soil degradation experiment

[0095] To study the degradation behavior of the fresh-keeping paper and plastic in the natural environment, cut the two materials into samples of 21 cm × 29.7 cm respectively, and use the soil burial method to simulate the degradation environment. In the soil burial experiment, the samples are buried in the soil at a depth of 10 cm. By simulating the degradation conditions in the natural environment, systematically evaluate the degradation behavior of the fresh-keeping paper.

[0096] (2) Mechanical property test

[0097] Cut the paper-based composite material samples into strip specimens of standard size, and then conduct tensile strength tests. All tests are carried out under standard environmental conditions (temperature 23 ± 1 °C, relative humidity 50 ± 2%).

[0098] (3) Thermal stability experiment

[0099] To study the heat resistance of the fresh-keeping paper and plastic, cut the plastic film and fresh-keeping paper into samples with a diameter of 10 cm. Place the samples in a constant-temperature oven and set the temperatures to 60 °C and 120 °C respectively, and maintain for 30 minutes at each temperature. After taking out the samples, take pictures to record their deformation conditions, and measure the size changes of the samples to calculate the deformation rate.

[0100] Paper recycling experiment

[0101] The process of evaluating the recyclability of the paper-based composite material by the recycling experiment is as follows: First is the mechanical recycling. Oscillate and dissolve the used material in deionized water at 95 °C to separate the PVA coating and the fiber substrate, and the recycled fibers are recombined into paper sheets after beating.

[0102] Figure 1 It can be seen from the comparison of the storage of cherry tomatoes between Example 1 of the present invention and Control Group 1 that the treated example samples maintain a stable morphological structure and surface finish during the storage period, and the sensory deterioration rate is significantly lower than that of the control group. The visual commercial retention verifies the fresh-keeping efficacy advantage of the material.

[0103] Figure 2In Example 2, the weight loss rate in soil and water was significantly higher than that in the control example. Observations showed that obvious cracks and holes appeared on the surface of the example, and the fiber structure was gradually damaged, while only slight wear appeared on the surface of Control Example 2. These results indicate that the fresh-keeping paper has a faster degradation rate and higher environmental friendliness in the natural environment, while the degradation performance of plastics is poor, which may cause long-term pollution to the environment. The rapid degradation of the fresh-keeping paper is due to the synergistic effect of biology and physical chemistry.

[0104] Figure 3 Before failure, both Control Example 3 and Example 3 showed linear deformation characteristics. Among them, the tensile strength of the example reached 84.2 MPa, while the tensile strength of the control example was only 66.9 MPa, and the mechanical properties were significantly improved, with an increase of 25.9%.

[0105] Figure 4 The maximum tensile strength and elastic modulus of the example were much higher than those of the control example. The maximum tensile strength and elastic modulus of the example were 83.36 Mpa and 10197.47 Mpa respectively, while the maximum tensile strength and elastic modulus of the control example were 71.89 Mpa and 9845.53 Mpa respectively. The high tensile strength can withstand the stacking pressure during transportation and prevent the packaging of heavy items from bursting.

[0106] Figure 5 At 60 °C, no obvious deformation occurred in both Example 3 and Control Example 3, and the dimensional change rates were less than 1% and 0.5% respectively, indicating that both could maintain structural stability in a low-temperature environment. When the temperature rose to 120 °C, the plastic film began to show slight shrinkage and curling, and the dimensional change rate increased to about 5%, indicating its thermal softening; while the dimensional change rate of the fresh-keeping paper was only 1.5%, and no obvious deformation occurred, showing excellent thermal stability.

[0107] At 120 °C, significant deformation occurred in the control example, manifested as severe shrinkage and partial melting, and the dimensional change rate was as high as more than 15%. At 180 °C, the control example completely lost its structural stability, while the dimensions of the example basically did not change and no melting phenomenon occurred, only slight curling on the surface, indicating that it could still maintain high structural integrity at high temperatures.

[0108] Figure 6 The recycling stability of the paper-based composite material was verified through a closed-loop recycling process. The used material was thermally dissolved in deionized water at 95 °C to separate the cellulose substrate and the PVA coating, and the recycled fibers were re-prepared into recycled paper with a basis weight of 80 g / m 2 Judging from the appearance, there was no significant difference between the recycled paper and the original paper, and this result confirmed that the paper-based composite material had both recoverable mechanical properties and ecological sustainability.

[0109] Figure 7The surface of Comparative Example 4 presented a typical fiber network structure with relatively uniform fiber distribution, but there were obvious unevenness and pore structures. The coating layer of the Example uniformly covered the surface of the paper-based material, and the microcapsule particles were evenly distributed and tightly bound to the fibers. At a high magnification, the structure of the microcapsules could be clearly seen, and the interfacial bonding between the microcapsules and the paper-based material was tight, and no obvious peeling or falling-off phenomenon was observed, indicating that the coating layer had good adhesion.

[0110] The present invention uses cellulose as a substrate to composite polyvinyl alcohol, and through a bionic gradient cross-linking system regulated by borax, promotes the hydrogen bond combination of PVA and urea, thereby forming a dense structure, enhancing the oil resistance, water resistance, transparency and barrier property of the paper-based material. The paper-based material of the present invention can effectively block gases, water and oil, enabling food to be in a relatively stable environment, protecting the appearance of food and effectively extending the food preservation period, and the relatively high transparency allows for clearer printing.

[0111] The above has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A preparation process of fresh-keeping paper constructed based on a plant bionic cross-linking strategy, characterized in that, It includes the following steps: S1. Dissolve polyvinyl alcohol in deionized water at 93 - 97 °C to form a homogeneous polyvinyl alcohol solution with a concentration of 1.5 - 3 wt%. S2. Add borax to the solution obtained in S1, and stir at 88 - 92 °C for 25 - 35 min at a stirring speed of 400 - 600 r / min to form a borax-mediated pre-crosslinked system. S3. Under continuous alkaline conditions, add urea to the pre-crosslinked system obtained in S2, and continue stirring for 25 - 35 min to construct a three-dimensional dense grid structure of PVA-urea hydrogen bonds. S4. Apply sizing to the surface of the base paper with a basis weight of 35 - 45 g / m² at a coating amount of the composite coating obtained in S3 of 2.5 - 3.0 g / m², and dry it at 60 - 105 °C for 8 - 12 min to form a fresh-keeping paper substrate with a gradient cross-linked structure; 2 2 ​​ The food wrap has the following performance parameters: Water vapor transmission rate ≤ 15 g / m 2 ·24 h Oxygen transmission rate ≤ 5 cm 3 / m 2 ·24 h·0.1 MPa Tensile strength ≥ 80 MPa.

2. The preparation process of the fresh-keeping paper constructed based on the plant bionic cross-linking strategy according to claim 1, characterized in that, In S1, the molecular weight of polyvinyl alcohol is 70,000 - 100,000, and the degree of alcoholysis is 85 - 99%.

3. The preparation process of the fresh-keeping paper constructed based on the plant bionic cross-linking strategy according to claim 1, characterized in that, In S2, the addition amount of borax is 0.8 - 1.2% of the mass of polyvinyl alcohol, and the pH value of the crosslinking reaction is controlled at 8.5 - 9.

5.

4. The preparation process of the fresh-keeping paper constructed based on the plant bionic cross-linking strategy according to claim 3, wherein, In S3, by adding ammonia water, the alkaline condition is controlled to maintain the pH value of the system at 9.0 - 10.

0.

5. The preparation process of the fresh-keeping paper constructed based on the plant bionic cross-linking strategy according to claim 4, characterized in that, The urea accounts for 1.3 - 1.7 wt% of the mass ratio in the pre-crosslinked system in S3.

6. The preparation process of the fresh-keeping paper constructed based on the plant bionic cross-linking strategy according to claim 1, characterized in that, In S4, a gradient heating method is adopted, specifically including: The first stage: Dry at 60 - 70 °C for 3 - 5 min. The second stage: Dry at 80 - 90 °C for 4 - 6 min. The third stage: Dry at 95 - 105 °C for 1 - 2 min.

7. The preparation process of the fresh-keeping paper constructed based on the plant bionic cross-linking strategy according to claim 1, characterized in that, In S4, the base paper is prepared by mixing bleached softwood pulp and hardwood pulp in a ratio of 1:1 - 1:3, and its air permeability ≤ 3 μm / Pa·s.

8. The preparation process of the fresh-keeping paper constructed based on the plant bionic cross-linking strategy according to claim 1, characterized in that, The food wrap has a transparency ≥ 85% under the light environment with a wavelength of 550 nm.

9. Use of the fresh-keeping paper constructed based on the plant bionic cross-linking strategy according to any one of claims 1 to 8, characterized in that, The food wrap is used for packaging fresh fruits and vegetables, extending the shelf life of strawberries to 7 - 9 days at 25 °C and 50% RH, and the weight loss rate ≤ 5%.

10. The recycling method of the fresh-keeping paper constructed based on the plant bionic cross-linking strategy according to claims 1 to 8, characterized in that, It includes the following steps. S501. Ultrasonically treat the used food wrap material in deionized water at 90 - 100 °C for 10 - 20 min to separate the PVA coating and the cellulose substrate. After the recycled fiber substrate is beaten to a beating degree of 35 to 45° SR, it is re-pulped into recycled paper with a basis weight of 38 to 42 g / m 2 ².

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