Preservative film with synergistic micropore barrier and preparation method thereof

Abstract

The invention relates to a microporous barrier synergistic preservative film and a preparation method thereof. The preservative film comprises a base film, an oxygen absorption coating and a covering layer, the base film sequentially comprises an outer layer, a blocking layer and an inner layer from outside to inside, and the inner layer is a heat sealing layer. The membrane surface is divided into a central perforation area and a circumferential sealing strip area, the central perforation area is provided with a micro perforation group penetrating through the base membrane, the circumferential sealing strip area is provided with an oxygen uptake coating and is packaged by being matched with a covering layer, the oxygen uptake coating and the micro perforation group are not overlapped on the membrane surface, and a heat sealing strip area is reserved on the edge of the membrane surface. The preservative film disclosed by the invention has the effects of slowing down the quality deterioration of fruits and vegetables and prolonging the storage shelf life, and also has controlled atmosphere stability and sealing reliability.

Description

Technical Field

[0001] This invention relates to the technical field of food preservation film, and in particular to a food preservation film with microporous barrier synergy and its preparation method. Background Technology

[0002] Plastic wrap is widely used for the storage and distribution of fresh produce such as fruits and vegetables. Fresh produce continues to respire and metabolize after harvest, and changes in the oxygen and carbon dioxide concentrations inside the packaging affect processes such as water loss, browning, softening, and microbial growth. Therefore, the control of gas transfer behavior by packaging materials has a significant impact on preservation effectiveness.

[0003] Currently, common practices include using multi-layer barrier films to reduce gas permeability, improving gas exchange capacity through perforation / microperforation, and reducing oxygen content inside the packaging by adding oxygen scavengers. However, these solutions often require trade-offs between barrier properties, permeability, and oxygen absorption under different operating conditions, and also need to consider heat sealing and packaging reliability, which can easily lead to problems such as unstable atmosphere control and insufficient adaptability.

[0004] Therefore, how to provide a preservation film that can stably regulate the internal gas environment of packaging and its preparation method, while taking into account the reliability of heat sealing, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned problems existing in the prior art and to provide a microporous barrier synergistic preservation film and its preparation method.

[0006] To achieve the above objectives, the first aspect of the present invention provides a microporous barrier synergistic preservation film, comprising a base film, an oxygen-absorbing coating, and a covering layer; The base film comprises an outer layer, a barrier layer, and an inner layer stacked sequentially from the outside to the inside, wherein the inner layer is a heat-sealing layer; The plastic wrap includes a central perforated area and a circumferential sealing strip area on its surface. The circumferential sealing strip area is continuously arranged along at least one side of the plastic wrap, and the central perforated area and the circumferential sealing strip area do not overlap on the film surface. The central perforated area is provided with a group of micro-perforations penetrating the outer layer, the barrier layer, and the inner layer. The pore size of the micro-perforation group is 20-150 μm, and the pore density is 50-5000 pores / m². 2 ; The circumferential sealing strip area is provided with a heat-sealing reserved strip area along the edge of the plastic wrap. The width of the heat-sealing reserved strip area is 2-15mm, and the oxygen-absorbing coating is not provided in the heat-sealing reserved strip area. The oxygen-absorbing coating is disposed on the inner surface of the inner layer and confined within the circumferential sealing strip area. The oxygen-absorbing coating includes a base coating and an oxygen-absorbing layer, with the base coating located between the inner layer and the oxygen-absorbing layer. The covering layer covers the oxygen-absorbing layer and is confined within the circumferential sealing strip area. The covering layer includes an encapsulation layer and a heat-sealing compatible layer.

[0007] As a further improvement of the present invention, the width of the circumferential sealing strip area is 5-60 mm, and the distance from the inner boundary of the circumferential sealing strip area to the nearest edge of the plastic wrap is 0-10 mm; the thickness of the oxygen-absorbing layer is 2-30 μm, and the oxygen-absorbing layer in the circumferential sealing strip area consists of multiple oxygen-absorbing coating strips extending along the edge direction of the plastic wrap, the width of a single oxygen-absorbing coating strip is 0.5-8 mm, and the spacing between two adjacent oxygen-absorbing coating strips is 0.5-12 mm; the pitch of the oxygen-absorbing coating strips is 1-5 times the center distance between two adjacent holes in the central perforation area.

[0008] As a further improvement of the present invention, the micro-perforated group is characterized in that it forms a regular array within the central perforated area, and the center distance between two adjacent holes is 2 to 25 mm.

[0009] As a further improvement of the present invention, the barrier layer is an ethylene-vinyl alcohol copolymer layer, wherein the ethylene molar fraction in the ethylene-vinyl alcohol copolymer is 24-48 mol%, and the thickness of the barrier layer is 3-20 μm.

[0010] As a further improvement of the present invention, the base coating comprises a modified polyolefin bonding resin and an inorganic thickening filler, wherein the modified polyolefin bonding resin is maleic anhydride-grafted polyethylene and / or maleic anhydride-grafted polypropylene, the inorganic thickening filler is fumed silica and / or nano-calcium carbonate, and the thickness of the base coating is 0.2 to 5 μm. The oxygen-absorbing layer comprises a polymer binder phase and oxygen-absorbing composite particles dispersed in the polymer binder phase. The oxygen-absorbing composite particles are prepared from metallic iron powder, sodium chloride, molecular sieve, and a water-soluble granulating agent. The metallic iron powder accounts for 60-90% of the mass of the oxygen-absorbing composite particles, sodium chloride accounts for 0.3-3%, molecular sieve accounts for 2-20%, and water-soluble granulating agent accounts for 3-15%. The water-soluble granulating agent is one or two of polyvinyl alcohol, sodium carboxymethyl cellulose, and polyvinylpyrrolidone. The median particle size of the oxygen-absorbing composite particles is 30-300 μm.

[0011] As a further improvement of the present invention, the encapsulation layer is one of ethylene-vinyl acetate copolymer, thermoplastic polyurethane or polyethylene, and the thickness of the encapsulation layer is 0.5 to 8 μm; The heat-sealable compatibility layer is linear low-density polyethylene and / or metallocene linear low-density polyethylene, and the thickness of the heat-sealable compatibility layer is 0.5 to 15 μm; The heat-sealing compatible layer is continuously disposed along the edge of the cling film and covers the circumferential sealing strip area; the encapsulation layer is confined within the circumferential sealing strip area and avoids the heat-sealing reserved strip area, and the encapsulation layer forms a 1-10 mm overlap width on the film surface over the outer boundary of the oxygen-absorbing layer.

[0012] A second aspect of the present invention provides a method for preparing the microporous barrier-synergistic preservation film as described above, comprising the following steps: S1, a base film comprising an outer layer, a barrier layer and an inner layer is prepared by co-extrusion, wherein the inner layer is a heat-sealing layer; S2, the inner surface of the inner layer of the base film is subjected to corona treatment, with a corona treatment power density of 0.5–3.0 kW·min / m. 2 ; S3, using a patterned coating method, the primer liquid is applied only to the circumferential sealing strip area and dried to form a primer layer, and a heat-sealing reserved strip area with a width of 2 to 15 mm is reserved along the edge of the plastic wrap in the circumferential sealing strip area; S4, using a patterned coating method, the oxygen-absorbing coating liquid is applied only to the circumferential sealing strip area and dried to form an oxygen-absorbing layer. The oxygen-absorbing layer consists of multiple oxygen-absorbing coating strips extending along the edge direction, and the oxygen-absorbing coating strips avoid the heat-sealing reserved strip area. S5, a covering layer is formed in the circumferential sealing strip area to cover the oxygen-absorbing layer, a sealing layer is first formed and avoids the heat-sealing reserved strip area, and then a heat-sealing compatible layer is formed continuously along the edge of the plastic wrap. S6, laser micro-perforation is performed in the central perforation area to form a group of micro-perforations that penetrate the base film, and the group of micro-perforations does not overlap with the oxygen-absorbing coating on the film surface.

[0013] As a further improvement of the present invention, the patterned coating method is one of gravure coating, flexographic coating or slot coating, and the width of the circumferential sealing strip area is limited to 5-60 mm by a mask, a positioning coating roller or a positioning doctor blade, and the width of the heat-sealing reserved strip area is limited to 2-15 mm.

[0014] As a further improvement of the present invention, the oxygen-absorbing composite particles are obtained by spray granulation, and the inlet air temperature for spray granulation is 120-200°C; the oxygen-absorbing coating liquid comprises 70-95% oxygen-absorbing composite particles and 5-30% polymer binder phase by weight of solid components, and the dry coating weight of the oxygen-absorbing layer is 0.5-12 g / m². 2 The drying temperature is 40–80°C, and the drying time is 1–10 min.

[0015] As a further improvement of the present invention, the laser micro-perforation uses a CO2 laser with a wavelength of 9.3 to 10.6 μm, a single pulse energy of 0.1 to 3.0 mJ, and a pulse frequency of 1 to 50 kHz.

[0016] The present invention, by adopting the above technical solution, has the following beneficial effects: (1) By setting the base film as a multi-layer structure consisting of an outer layer, a barrier layer, and a heat-sealing layer, and setting a micro-perforation array penetrating each layer in the central perforation area, the gas transfer between the inside and outside of the packaging is determined by two parts simultaneously. The first part is the permeation of the barrier layer. Oxygen, carbon dioxide, and water vapor need to pass through the barrier layer to be exchanged through the membrane material. The transfer speed of this part is relatively slow, mainly playing the role of limiting the overall exchange volume and preventing the gas from entering and exiting too quickly. The second part is the exchange of the micro-perforations. The micro-perforations are equivalent to providing several direct exchange channels on the membrane. Gases can enter and exit through the channels without passing through the barrier layer. This part is more sensitive to the exchange speed and is easily affected by changes in pore size and pore density. After the two parts are superimposed, the barrier layer provides a stable basic constraint, and the micro-perforations provide adjustable exchange compensation. With this setting, the micro-perforations are not randomly opened, but form a network of exchange points in a regular array. The pore size and pore density control the total exchange volume, and the center distance of the pore array controls the uniformity of the coverage of exchange points on the membrane surface and the difference in local exchange strength. This method can simultaneously constrain the overall exchange level and the exchange distribution, reduce atmosphere fluctuations caused by excessive local exchange, and make it easier for the atmosphere inside the packaging to form and remain within a predictable range.

[0017] (2) By concentrating the micro-perforation group in the central perforation area and separating it from the circumferential sealing strip, gas exchange mainly occurs in the central area, while sealing is mainly completed in the edge strip area. The central area is usually far from the heat seal line, the film structure is more continuous, and the processing and distribution of the pore structure are easier to maintain consistency. The edge strip area undertakes the main function of bag making and heat sealing, requiring a clean interface, continuous material, and stable melt flow. After separating the two, the perforation process does not need to make way for the heat seal line, and the heat sealing does not need to avoid the perforation area. This can reduce local weaknesses and air leakage sensitivity at the sealing point caused by the pore structure or processing marks, and improve the consistency of bag making and sealing.

[0018] (3) By setting the micro-perforation group as a regular array and limiting the center distance between adjacent holes, the distribution of holes can be controlled, not just the total number of holes. The regular array can avoid local clustering or local sparseness of holes. After the center distance is limited, the distance between holes will not change significantly with processing fluctuations. This allows the exchange points in the central perforation area to be distributed more evenly, reducing the situation where the exchange is too strong or too weak in some local areas.

[0019] (4) By setting a heat-sealing reserved strip area near the edge of the film in the circumferential sealing strip area, and limiting the oxygen-absorbing coating in this area, the area where the heat-sealing line is located is kept as the direct contact interface of the heat-sealing material. During heat sealing, the heat-sealing layer needs to be fully fused under pressure and temperature to form a continuous sealing line. If the heat-sealing interface is mixed with particulate systems such as iron powder and salts, inclusion points are likely to occur, resulting in local discontinuity or uneven thickness of the sealing line. The reserved strip area separates these particulate systems from the heat-sealing interface, keeping the material composition of the heat-sealing line uniform and the melt flow more stable.

[0020] (5) By setting the oxygen-absorbing coating as a two-layer structure of a primer and an oxygen-absorbing layer, the oxygen-absorbing layer is not directly attached to the surface of the heat-sealing layer, but rather to the primer. The primer uses grafted modified polyolefin resin, which has better compatibility with the heat-sealing layer and more stable adhesion. After adding tackifying fillers to the primer, the coating has stronger anti-sagging and anti-edge shrinkage capabilities. In this way, the oxygen-absorbing layer is less likely to peel, shrink at the edges, or fall off locally during coating and drying. The strip boundaries are also easier to keep clear.

[0021] (6) By setting the oxygen-absorbing layer as multiple coating strips extending along the membrane edge and limiting the strip width and spacing, the area occupied by the oxygen-absorbing material can be directly controlled according to the dimensions. Strip pattern coating can leave a clear blank area within the sealing strip area, preventing the oxygen-absorbing material from covering the heat-sealing reserved strip area. After limiting the strip width and spacing, the distribution of oxygen-absorbing material on the sealing edge per unit length is more consistent. This ensures the stable arrangement of the oxygen-absorbing material and facilitates the subsequent sealing of the overlay layer according to the same boundary.

[0022] (7) By limiting the pitch of the oxygen-absorbing coating strips to 1 to 5 times the center-to-center distance between two adjacent holes in the central perforated area, a corresponding relationship is established between the arrangement density of the perforated array and the arrangement density of the oxygen-absorbing coating strips. A smaller center-to-center distance between the perforations indicates that the exchange points are denser and the exchange capacity of the central area is stronger. In this case, the pitch of the oxygen-absorbing coating strips is constrained within the corresponding range, and the oxygen-absorbing coating strips will not be too sparse to match the exchange intensity. A larger center-to-center distance between the perforations indicates that the exchange points are sparser and the exchange capacity of the central area is weaker. The oxygen-absorbing coating strips will not be set too densely, avoiding an excessive difference between the oxygen absorption arrangement at the edge and the exchange capacity at the center.

[0023] (8) By using oxygen-absorbing composite particles in the oxygen-absorbing layer and limiting the median particle size range, the oxygen-absorbing material enters the coating system in a more stable particle morphology. Powders with excessively small median particle sizes are more likely to migrate towards the edges with the coating flow and are also more likely to accumulate or cause dust contamination during the drying process. By using composite particles and limiting the particle size, the particles have lower migration during the coating process, more uniform strip loading, and clearer boundaries. The particles also contain iron powder, salt, and molecular sieves, allowing the active components to exist in a composite manner in the coating, reducing local fluctuations caused by uneven dispersion of different powders. This is more conducive to the formation of a stable coating layer in the subsequent encapsulation layer.

[0024] (9) By setting the cover layer as a dual-layer structure of encapsulation layer and heat-sealing compatible layer, and limiting the coverage of each layer, the encapsulation function and heat-sealing function are separated. The heat-sealing compatible layer continuously covers the sealing strip area along the edge of the film, ensuring that the area corresponding to the heat-sealing line is always covered by a material suitable for heat sealing. The encapsulation layer only covers the oxygen-absorbing coating strip at the required locations, avoiding the heat-sealing reserved strip area, to prevent the encapsulation layer material from entering the heat-sealing interface. After the encapsulation layer forms an overlap width with the outer boundary of the oxygen-absorbing layer, the edge of the oxygen-absorbing coating strip is pressed down and continuously covered, reducing edge lifting or local exposure.

[0025] (10) By arranging laser micro-perforation after the completion of the oxygen-absorbing coating and the cover layer and only performing it in the central perforation area, the local heat effect and re-solidification edge introduced by the perforation process do not participate in the wetting, leveling and drying film formation process of the coating. This avoids the occurrence of edge shrinkage, burrs or uneven load near the perforation processing area of ​​the strip coating boundary, and ensures that the boundary of the oxygen-absorbing coating strip and the overlap boundary of the cover are determined separately by the coating and film-coating processes and remain consistent. Secondly, by first forming the encapsulation layer and making it avoid the heat-sealing reserved strip area, and then forming a heat-sealing compatible layer continuously set along the edge of the film, the oxygen-absorbing coating strip is first pressed by the encapsulation layer and the boundary is fixed by the overlap width. Subsequently, the heat-sealing interface is continuously covered by the heat-sealing compatible layer, thereby separating the encapsulation fixation of the particulate oxygen-absorbing system from the heat-sealing interface continuity, avoiding the material compromise and sealing fluctuation caused by a single covering step simultaneously taking into account both encapsulation and heat sealing. Furthermore, by performing corona treatment before applying the oxygen-absorbing layer and then sequentially applying the primer and oxygen-absorbing layer, the wetting and adhesion conditions of the strip coating are uniformly established before entering the particle system. The primer provides a stable bearing interface in advance, thereby reducing boundary drift caused by particle migration to the strip edge during the drying stage and improving the repeatability of strip width, spacing and other pattern parameters in production. Detailed Implementation

[0026] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0027] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0030] The present invention will now be described in detail with reference to specific embodiments, which are intended to understand rather than limit the invention.

[0031] Unless otherwise specified, the raw materials used in the following examples are: The outer resin uses Dow Chemical Co., Ltd. TM 608A low-density polyethylene.

[0032] The barrier layer resin used is Kuraray EVAL. TM F101B is an ethylene-vinyl alcohol copolymer.

[0033] The inner layer resin uses ExxonMobil Exceed TM m 1018 metallocene linear low-density polyethylene.

[0034] The primer bonding resin used is Dow BYNEL. TM 4109 Anhydride-modified polyolefin bonding resin.

[0035] The inorganic thickening filler used is Evonik's AEROSIL® 200 fumed silica.

[0036] The metallic iron powder used was Höganäs ASC100.29 reduced iron powder.

[0037] The molecular sieve used is Zeochem's 4A Purmol Powder molecular sieve powder.

[0038] The water-soluble granulating agent used is Kuraray POVAL. TM PVA-217 Polyvinyl alcohol.

[0039] The encapsulation layer resin used is Sancure from Lubrizol. TM2710 Waterborne polyurethane dispersion.

[0040] Sodium chloride was obtained from the analytical grade sodium chloride produced by Sinopharm Chemical Reagent Co., Ltd.

[0041] Example 1

[0042] This embodiment discloses a method for preparing a microporous barrier-synergistic preservation film, including the following steps: S1, Co-extrusion preparation of the base film: Three resins—outer layer, barrier layer, and inner layer—are used as the three-layer co-extrusion raw materials, with the outer layer resin being Dow Chemical Co., Ltd. TM 608A low-density polyethylene; the barrier layer resin is Kuraray EVAL. TM F101B ethylene-vinyl alcohol copolymer; inner layer resin uses ExxonMobil Exceed... TM m 1018 metallocene linear low-density polyethylene. The above three resins are placed in three extruders for melt extrusion and merged in the same composite die to form a three-layer melt flow. Then, they are extruded through an annular die to form a tubular preform, which is blown into shape, cooled and shaped, and then wound up to obtain the base film.

[0043] The thickness of each layer of the base film is as follows: outer layer thickness 20μm, barrier layer thickness 10μm, inner layer thickness 40μm, and total thickness 70μm. The base film surface is divided into regions to form a central perforated area and a circumferential sealing strip area. Specifically, taking a rectangular base film as an example, circumferential sealing strip areas are set along the four sides of the base film. The width of the circumferential sealing strip area on the film surface is 30mm, and the distance from the inner boundary of the circumferential sealing strip area to the nearest edge of the base film is 2mm. The central perforated area is the film surface area excluding the circumferential sealing strip area, ensuring that the central perforated area and the circumferential sealing strip area do not overlap on the film surface. Further, a heat-sealing reserved strip area is set along the edge of the base film within the circumferential sealing strip area. The width of the heat-sealing reserved strip area is 8mm. This heat-sealing reserved strip area is used as a blank strip area in subsequent processes where no oxygen-absorbing coating is applied.

[0044] S2, the base film obtained in step S1 is unfolded and run on a corona treatment machine. Only the inner surface of the inner layer is subjected to single-sided corona treatment, while the outer surface is not corona treated. The corona treatment uses an atmospheric pressure air atmosphere. The corona electrode is a ceramic-coated metal roller electrode, and the grounding roller is a metal cooling roller. The gap between the electrode and the film surface is set to 1.5 mm. The corona treatment power density is set to 1.50 kW·min / m³. 2 The corresponding operating parameters are set as follows: equipment output power 2.25 kW, membrane width 1.0 m, and linear velocity 30 m / min. This results in an energy input per unit area of ​​1.50 kW·min / m.2 The corona treatment is performed in a single pass, without repeated corona treatment.

[0045] S3, Patterned application of the primer layer and formation of heat-sealing pre-reserved strip areas: The primer liquid is prepared according to BYNEL by mass. TM 4109100, AEROSIL®2002, xylene 900; stir for 60 min and let stand for 30 min to degas. Use positioning coating so that the base coating is only located in the circumferential sealing strip area and avoids the heat-sealing reserved strip area; drying conditions are 70℃ for 3 min; the dry film thickness of the base coating is 1.0 μm.

[0046] S4, Patterned Coating of Oxygen Absorbing Layer: The oxygen-absorbing composite particles are formulated by mass percentage as follows: 80% ASC100.29 iron powder, 1% sodium chloride, 10% 4A Purmol Powder, and 79% PVA-21. Deionized water is added to prepare a slurry with a solid content of 30%. Spray granulation is performed at an inlet air temperature of 160℃ and an outlet air temperature of 90℃, resulting in composite particles with a D50 of 120μm. The oxygen-absorbing coating solution by solid mass percentage is 85% composite particles and 85% Sancure... TM 2710 (based on solids) 15%, adjusted to 38% solids content with deionized water. Strip-coating is employed, with strips extending along the film edge and avoiding the heat-sealing pre-reserved strip area; single strip width 3.0 mm, adjacent strip spacing 3.0 mm, and dry coating weight of the oxygen-absorbing layer 6.0 g / m³. 2 The drying conditions are 60℃ for 5 minutes; the dry film thickness of the oxygen-absorbing layer is 10μm. The pitch of the oxygen-absorbing coating strip is 30mm; the center-to-center distance between adjacent holes in the central perforated area is 10mm, so that the pitch is 3 times the center-to-center distance.

[0047] S5, Forming the Covering Layer: First, form an encapsulation layer in the circumferential sealing strip area, avoiding the heat-sealing reserved strip area, and overlap the outer boundary of the oxygen-absorbing layer with a width of 5 mm; the dry film thickness of the encapsulation layer is 3.0 μm, and the drying conditions are 50℃ for 5 min. Then, continuously form a heat-sealing compatible layer at the film edge, covering the entire circumferential sealing strip area (including the heat-sealing reserved strip area); the thickness of the heat-sealing compatible layer is 10 μm.

[0048] S6. Laser micro-perforation is performed in the central perforation area: a CO2 laser is used with a wavelength of 10.6 μm, a single pulse energy of 1.0 mJ, and a pulse frequency of 10 kHz; the aperture is 80 μm and the pore density is 800 pores / m²; the pore array is a regular array with a center-to-center distance of 10 mm between adjacent pores; the micro-perforation group and the oxygen absorption coating do not overlap on the film surface.

[0049] Example 2

[0050] The only difference between this embodiment and Embodiment 1 is the different values ​​of some material grades and process parameters in S1 to S6. The specific differences are as follows: In step S1, the barrier layer resin used is Kuraray EVAL. TM E105B; barrier layer thickness set to 5μm; outer layer thickness set to 25μm; inner layer thickness set to 35μm; total base film thickness set to 65μm.

[0051] The width of the circumferential sealing strip area is set to 20mm; the distance from the inner boundary of the circumferential sealing strip area to the nearest edge of the base film is set to 0mm; and the width of the heat-sealing reserved strip area is set to 5mm.

[0052] In step S2, the power density of the corona treatment was set to 0.80 kW·min / m²; the gap between the electrode and the film surface was set to 1.5 mm; and the linear velocity was set to 30 m / min.

[0053] In step S3, the primer formulation is set as: BYNEL TM 4109 100 parts by weight, AEROSIL®200 1 part by weight, xylene 950 parts by weight; drying conditions set at 70℃ for 2 min; base coating dry film thickness set at 0.5 μm.

[0054] In step S4, the oxygen-absorbing composite particle formula is set as follows: 82wt% ASC100.29 iron powder, 1wt% sodium chloride, 8wt% 4A molecular sieve, and 9wt% PVA-217; the spray granulation inlet air temperature is set to 150℃, the outlet air temperature to 85℃, and the composite particle D50 to 60μm. The solid ratio of the oxygen-absorbing coating liquid is set as follows: 90wt% oxygen-absorbing composite particles, Sancure... TM 2710 (solids) 10wt%; the solid content of the oxygen-absorbing coating solution is set at 32wt%. The width of a single oxygen-absorbing coating strip is set at 1.0mm, and the spacing between adjacent strips is set at 1.0mm; the dry coating weight of the oxygen-absorbing layer is set at 2.0g / m². 2 The drying conditions were set to 60℃ for 4 minutes; the dry film thickness of the oxygen-absorbing layer was set to 3μm. The pitch of the oxygen-absorbing coating strips was set to 80mm; the center-to-center distance between adjacent holes in the central perforated area array was set to 20mm, making the pitch four times the center-to-center distance.

[0055] In step S5, the dry film thickness of the encapsulation layer is set to 1.0 μm; the overlap width of the outer boundary of the oxygen-absorbing layer is set to 2 mm; and the drying conditions for the encapsulation layer are set to 50°C for 4 min. The thickness of the heat-sealing compatible layer is set to 5 μm.

[0056] In step S6, the CO2 laser single-pulse energy is set to 0.6 mJ, the pulse frequency is set to 8 kHz, the aperture is set to 30 μm, and the pore density is set to 100 pores / m². 2 The center distance between two adjacent holes in the hole array is set to 20mm.

[0057] Example 3

[0058] The only difference between this embodiment and Embodiment 1 is the different values ​​of some material grades and process parameters in S1 to S6. The specific differences are as follows: In step S1, the barrier layer resin used is Kuraray EVAL. TM E151B; barrier layer thickness set to 20μm; outer layer thickness set to 15μm; inner layer thickness set to 45μm; total base film thickness set to 80μm.

[0059] The width of the circumferential sealing strip area is set to 60mm; the distance from the inner boundary of the circumferential sealing strip area to the nearest edge of the base film is set to 10mm; and the width of the heat-sealing reserved strip area is set to 15mm.

[0060] In step S2, the corona treatment power density is set to 2.50 kW·min / m³. 2 The gap between the electrode and the film surface is set to 1.5 mm; the linear velocity is set to 30 m / min.

[0061] In step S3, the primer formulation is set as: BYNEL TM 41091 00 parts by weight, AEROSIL®200 4 parts by weight, xylene 800 parts by weight; drying conditions set at 75℃ for 4 min; base coating dry film thickness set at 4.0 μm.

[0062] In step S4, the oxygen-absorbing composite particle formula is set as follows: 78wt% ASC100.29 iron powder, 1wt% sodium chloride, 12wt% 4A molecular sieve, and 9wt% PVA-217; the spray granulation inlet air temperature is set to 190℃, the outlet air temperature to 95℃, and the composite particle D50 to 250μm. TM 2710 (solids) 30wt%; the solid content of the oxygen-absorbing coating solution is set at 42wt%. The width of a single oxygen-absorbing coating strip is set at 8.0mm, and the spacing between adjacent strips is set at 12.0mm; the dry coating weight of the oxygen-absorbing layer is set at 11.0g / m². 2 The drying conditions were set to 70℃ for 8 minutes; the dry film thickness of the oxygen-absorbing layer was set to 25 μm. The pitch of the oxygen-absorbing coating strips was set to 10 mm; the center-to-center distance between adjacent holes in the central perforated area array was set to 2 mm, making the pitch 5 times the center-to-center distance.

[0063] In step S5, the dry film thickness of the encapsulation layer is set to 8.0 μm; the overlap width of the outer boundary of the oxygen-absorbing layer is set to 10 mm; and the drying conditions for the encapsulation layer are set to 50°C for 6 min. The thickness of the heat-sealing compatible layer is set to 15 μm.

[0064] In step S6, the CO2 laser single-pulse energy is set to 1.6 mJ, the pulse frequency is set to 20 kHz, the aperture is set to 150 μm, and the pore density is set to 5000 pores / m². 2 The center distance between two adjacent holes in the hole array is set to 2mm.

[0065] Comparative Example 1

[0066] The only difference between this comparative example and Example 1 is that it does not have an oxygen-absorbing coating and a covering layer, as detailed below: S1, Co-extrusion preparation of the base film: The outer resin uses Dow Chemical Co., Ltd. TM 608A low-density polyethylene; the barrier layer resin is Kuraray EVAL. TM F101B ethylene-vinyl alcohol copolymer; inner layer resin uses ExxonMobil Exceed... TM m 1018 metallocene linear low-density polyethylene. A three-layer base film was obtained by co-extrusion, with the outer layer having a thickness of 20 μm, the barrier layer having a thickness of 10 μm, and the inner layer having a thickness of 40 μm, for a total thickness of 70 μm.

[0067] Define a central perforated area and a circumferential sealing strip area on the base membrane surface: the circumferential sealing strip area is continuously set along the four sides of the base membrane, with a strip width of 30 mm, and the distance from the inner boundary of the circumferential sealing strip area to the nearest edge of the base membrane is 2 mm; the central perforated area is the membrane surface area other than the circumferential sealing strip area, so that the central perforated area and the circumferential sealing strip area do not overlap on the membrane surface.

[0068] S2, Corona treatment of the inner surface of the base film inner layer: Only the inner surface of the inner layer is subjected to single-sided corona treatment, with a corona treatment power density of 1.50 kW·min / m. 2 The gap between the electrode and the film surface is 1.5 mm.

[0069] S3, laser micro-perforation is performed in the central perforation area: A CO2 laser with a wavelength of 10.6 μm, a single pulse energy of 1.0 mJ, and a pulse frequency of 10 kHz was used to form a micro-perforation group penetrating the base film in the central perforation region. The micro-perforation group had a pore size of 80 μm and a pore density of 800 pores / m². The micro-perforation group was a regular array with a center-to-center distance of 10 mm between adjacent pores.

[0070] Comparative Example 2

[0071] The only difference between this comparative example and Example 1 is that the micro-perforation group is not set, as detailed below: S1, Co-extrusion preparation of the base film: The outer resin uses Dow Chemical Co., Ltd. TM 608A low-density polyethylene; the barrier layer resin is Kuraray EVAL. TM F101B ethylene-vinyl alcohol copolymer; inner layer resin uses ExxonMobil Exceed... TM m 1018 metallocene linear low-density polyethylene. A three-layer base film was obtained by co-extrusion, with the outer layer having a thickness of 20 μm, the barrier layer having a thickness of 10 μm, and the inner layer having a thickness of 40 μm, for a total thickness of 70 μm.

[0072] Define a central perforation area and a circumferential sealing strip area on the base film surface: the circumferential sealing strip area is continuously set along the four sides of the base film, with a strip width of 30 mm, and the distance from the inner boundary of the circumferential sealing strip area to the nearest edge of the base film is 2 mm; a heat-sealing reserved strip area with a width of 8 mm is set near the edge of the base film in the circumferential sealing strip area; the central perforation area is the film surface area other than the circumferential sealing strip area, so that the central perforation area and the circumferential sealing strip area do not overlap on the film surface.

[0073] S2, Corona treatment of the inner surface of the base film inner layer: The inner surface of the inner layer was subjected to single-sided corona treatment, with a corona treatment power density of 1.50 kW·min / m²; the gap between the electrode and the film surface was 1.5 mm.

[0074] S3, patterned application of the base coat and formation of heat-sealing pre-reserved strip areas: The primer was prepared in the following proportions by weight: using Dow BYNEL... TM 100 parts by weight of 4109, 2 parts by weight of Evonik AEROSIL® 200, and 900 parts by weight of xylene were mixed; the mixture was stirred for 60 min and then allowed to stand for 30 min to degas. A targeted coating method was used, ensuring the primer was applied only to the circumferential sealing strip area and avoiding the heat-sealing pre-reserved strip area. The drying conditions were 70°C for 3 min to form a primer layer with a dry film thickness of 1.0 μm.

[0075] S4, Patterned coating oxygen-absorbing layer: The oxygen-absorbing composite granules are formulated by mass percentage as follows: 80% ASC100.29 iron powder, 1% sodium chloride (analytical grade, Sinopharm Chemical Reagent Co., Ltd.), 10% Zeochem 4A Purmol Powder molecular sieve, and Kuraray POVAL... TM PVA-217 9%; add deionized water to make a slurry with a solid content of 30%, spray granulation, inlet air temperature 160 ℃, outlet air temperature 90 ℃, to obtain composite particles with D50 of 120 μm.

[0076] The oxygen-absorbing coating solution, by solids mass percentage, is: 85% composite particles, using Lubrizol's Sancure... TM 2710 (based on solids) 15%, adjusted to 38% solids content with deionized water. A strip-based positioning coating method was used, ensuring the oxygen-absorbing coating solution was applied only to the circumferential sealing strip area and avoided the heat-sealing reserved strip area; the strips extended along the membrane edge direction, with a single strip width of 3.0 mm and a spacing of 3.0 mm between adjacent strips; the dry coating amount of the oxygen-absorbing layer was 6.0 g / m²; the drying conditions were 60 ℃ for 5 min to form the oxygen-absorbing layer, with a dry film thickness of 10 μm.

[0077] S5, forming a covering layer in the circumferential sealing strip area to cover the oxygen-absorbing layer: First, an encapsulation layer is formed. The encapsulation layer resin used is Sancure from Lubrizol. TM 2710, the encapsulation layer is confined within the circumferential sealing strip area and avoids the heat-sealing reserved strip area, and the encapsulation layer overlaps the outer boundary of the oxygen-absorbing layer on the film surface with a width of 5 mm; the drying conditions are 50 ℃ for 5 min, and the dry film thickness of the encapsulation layer is 3.0 μm.

[0078] A heat-sealing compatible layer is then formed. The heat-sealing compatible layer resin is ExxonMobil Exceed™ m 1018. The heat-sealing compatible layer is continuously set along the edge of the base film and covers the circumferential sealing strip area (including the heat-sealing reserved strip area). The thickness of the heat-sealing compatible layer is 10 μm.

[0079] Comparative Example 3

[0080] The only difference between this comparative example and Example 1 is that the microperforated group and the oxygen-absorbing coating overlap on the film surface, as detailed below: S1, Co-extrusion preparation of the base film: The outer resin uses Dow Chemical Co., Ltd. TM 608A low-density polyethylene; the barrier layer resin is Kuraray EVAL. TM F101B ethylene-vinyl alcohol copolymer; inner layer resin uses ExxonMobil Exceed... TM m 1018 metallocene linear low-density polyethylene. A three-layer base film was obtained by co-extrusion, with the outer layer having a thickness of 20 μm, the barrier layer having a thickness of 10 μm, and the inner layer having a thickness of 40 μm, for a total thickness of 70 μm.

[0081] Define a central perforation area and a circumferential sealing strip area on the base membrane surface: the circumferential sealing strip area is continuously set along the four sides of the base membrane, with a strip width of 30 mm, and the distance from the inner boundary of the circumferential sealing strip area to the nearest edge of the base membrane is 2 mm; a heat-sealing reserved strip area with a width of 8 mm is set near the edge of the base membrane in the circumferential sealing strip area; the central perforation area is the membrane surface area other than the circumferential sealing strip area.

[0082] S2, Corona treatment of the inner surface of the base film inner layer: Only the inner surface of the inner layer is subjected to single-sided corona treatment, with a corona treatment power density of 1.50 kW·min / m. 2 The gap between the electrode and the film surface is 1.5 mm.

[0083] S3, patterned application of the base coat and formation of heat-sealing pre-reserved strip areas: The primer was prepared in the following proportions by weight: using Dow BYNEL... TM 100 parts by weight of 4109, 2 parts by weight of Evonik AEROSIL® 200, and 900 parts by weight of xylene were mixed; the mixture was stirred for 60 min and then allowed to stand for 30 min to degas. A targeted coating method was used, ensuring the primer was applied only to the circumferential sealing strip area and avoiding the heat-sealing pre-reserved strip area. The drying conditions were 70°C for 3 min to form a primer layer with a dry film thickness of 1.0 μm.

[0084] S4, Patterned coating oxygen-absorbing layer: The oxygen-absorbing composite particles were formulated by mass percentage as follows: 80% ASC100.29 iron powder, 1% sodium chloride, 10% 4APurmol Powder molecular sieve, and 9% PVA-217. Deionized water was added to make a slurry with a solid content of 30%, which was then spray-granulated at an inlet air temperature of 160 ℃ and an outlet air temperature of 90 ℃ to obtain composite particles with a D50 of 120 μm.

[0085] The oxygen-absorbing coating solution, by solids mass percentage, is: 85% composite particles, using Sancure. TM 2710 (based on solids) 15%, adjusted to 38% solids content with deionized water. A strip-based positioning coating method was used, ensuring the oxygen-absorbing coating solution was applied only to the circumferential sealing strip area and avoided the heat-sealing reserved strip area; the strips extended along the membrane edge direction, with a single strip width of 3.0 mm and a spacing of 3.0 mm between adjacent strips; the dry coating amount of the oxygen-absorbing layer was 6.0 g / m²; the drying conditions were 60 ℃ for 5 min to form the oxygen-absorbing layer, with a dry film thickness of 10 μm.

[0086] S5, forming a covering layer in the circumferential sealing strip area to cover the oxygen-absorbing layer: First, an encapsulation layer is formed, using Sancure resin.TM 2710, the encapsulation layer is confined within the circumferential sealing strip area and avoids the heat-sealing reserved strip area, and the encapsulation layer overlaps the outer boundary of the oxygen-absorbing layer on the film surface with a width of 5 mm; the drying conditions are 50 ℃ for 5 min, and the dry film thickness of the encapsulation layer is 3.0 μm.

[0087] Then a heat-sealable compatibility layer is formed, using Exceed resin. TM m 1018, the heat-sealing compatible layer is continuously set along the edge of the base film and covers the circumferential sealing strip area (including the heat-sealing reserved strip area), and the thickness of the heat-sealing compatible layer is 10 μm.

[0088] S6, Perform laser microperforation to form a group of microperforations that overlap with the oxygen-absorbing coating: A CO2 laser with a wavelength of 10.6 μm, a single pulse energy of 1.0 mJ, and a pulse frequency of 10 kHz was used. Laser microperforation was performed in the region containing the circumferential sealing strip area, so that the resulting microperforation group overlapped with the oxygen-absorbing coating on the film surface. The pore size of the microperforation group was 80 μm, and the pore density was 800 pores / m². 2 The micro-perforated group is a regular array, with a center-to-center distance of 10mm between adjacent holes.

[0089] Performance testing

[0090] The plastic wrap prepared in Examples 1, 2, and 3, and the films prepared in Comparative Examples 1, 2, and 3 were used.

[0091] Bag specifications: Flat bag inner dimensions 180mm×220mm; each bag contains 250g of strawberries (selected for uniform ripeness, no mechanical damage, and individual fruit weight 12–18g).

[0092] Heat sealing conditions: heat sealing temperature 135℃, heat sealing pressure 0.25MPa, heat sealing time 1.2s; cold pressing and shaping 2s.

[0093] Storage conditions: refrigerate at 4°C for 10 days, then transfer to shelf conditions at 20°C for 2 days.

[0094] 1. Heat seal strength and seal integrity: (1) Heat sealing strength Take the heat-sealed edge of each sample bag and cut a 15 mm wide strip; stretch at 200 mm / min and measure the heat-sealed peel force; the result is expressed as N / 15 mm, and n=10 for each group.

[0095] (2) Leakage rate (air tightness) The water bath bubble method was used: the bag was filled with air until it was full (the pressure inside the bag was about 3 kPa), and then immersed in water for 30 seconds to observe continuous bubbles; n=10 per group, and the number of leaking bags was counted.

[0096] 2. Oxygen absorption capacity: To avoid interference from external oxygen supply due to microperforation, the oxygen uptake capacity test sample was taken from the circumferentially sealed strip area (the area without microperforation). The strip sample was cut into 50 mm × 50 mm pieces, and the mass was recorded; it was placed in a 1 L glass container with an initial gas composition of 2.0% O2 / 98.0% N2; after sealing, it was placed at 25 ℃; the O2 volume fraction at 0 h, 2 h, 6 h, and 24 h was measured using a headspace analyzer; n=3 for each group, and the average value was taken.

[0097] 3. Evolution of headspace gas within packaging: After each group of bags is filled, the headspace is measured immediately as Day 0. O2 / CO2 was measured at 4 ℃ on Day 2, Day 5, Day 7, and Day 10; then it was measured again after being transferred to a 20 ℃ shelf for 2 days (recorded as Day 12); n=3 per group at each time point.

[0098] 4. Strawberry quality indicators: Rot rate: The percentage of fruit that is moldy or rotten (%).

[0099] Weight loss rate: [(initial mass − final mass) / initial mass] × 100%.

[0100] Hardness: The force of piercing the flesh, with a piercing head diameter of 3 mm and a speed of 1 mm / s, is measured on average from 10 fruits per bag.

[0101] Odor rating: 1–5 points (1 = no odor, 5 = obvious fermentation / anaerobic odor), average of 3 people blind review.

[0102] Evaluation time points: Day 10 (4℃) and Day 12 (after 2 days at 20℃), n=3 bags per group.

[0103] The test results are shown in the table below: Table 1 Heat seal strength and leakage rate

[0104] Table 2 Oxygen Absorption Capacity

[0105] Table 3. Volume fraction of O2 in the headspace of strawberry packaging (%)

[0106] Table 4. CO2 volume fraction in the headspace of strawberry packaging (%)

[0107] Table 5 Strawberry quality results Day 10 (4℃)

[0108] Table 6 Strawberry quality results Day 12 (after 2 days on a 20℃ shelf)

[0109] Conclusion: (1) By comparing the heat seal strength and leakage rate, it can be seen that the heat seal strength of Examples 1 to 3 is maintained at 16.8 to 19.4 N / 15 mm and no air leakage bags appear. This indicates that by setting a heat seal reserved strip area in the circumferential sealing strip area and ensuring that the area does not contain oxygen-absorbing coating, and by adopting a structural arrangement in which the encapsulation layer avoids the heat seal reserved strip area and is continuously covered by the heat seal compatible layer, no sealing interface inclusions or sealing discontinuities will be introduced. Comparative Example 2 shows air leakage bags in the presence of an oxygen-absorbing system. Comparative Example 3 shows a significant decrease in heat seal strength and a high leakage rate due to the overlap of the perforation and oxygen-absorbing area. This indicates that when the particulate system or the perforation process affects the entry into the sealing interface, the sealing stability will be significantly weakened. The structural partitioning and the division of labor of the covering layer in Examples 1 to 3 can isolate such influences outside the sealing line.

[0110] (2) The oxygen absorption capacity test showed that Examples 1 to 3 could reduce the oxygen volume fraction in the container from 2.0% to below 0.20% within 24 hours at 25 °C. Specifically, Example 3 reduced it to 0.05%, Example 1 to 0.1%, and Example 2 to 0.2%, while the oxygen volume fraction in Comparative Example 1 remained unchanged. This result indicates that after the oxygen-absorbing material is dispersed as composite particles in the coating and forms an oxygen-absorbing layer in the circumferential sealing strip area, the oxygen absorption reaction can continue and has distinguishable strength levels. At the same time, the oxygen absorption capacity of Comparative Examples 2 and 3 is close to that of Example 1, indicating that the oxygen absorption capacity itself does not depend on whether there is micro-perforation, but rather on the formulation and loading level of the oxygen-absorbing layer.

[0111] (3) The changes in headspace gas over time in the packaging show that after 10 days of storage at 4 ℃ and 2 days of shelf transfer at 20 ℃, the headspace oxygen volume fraction of Examples 1 to 3 remained stable at about 5.0% to 9.1%, and the carbon dioxide volume fraction remained stable at about 10.0% to 15.0%, showing a relatively stable controlled atmosphere window. The oxygen volume fraction of Comparative Example 1 remained above 12.5% ​​for a long time, and the carbon dioxide was only about 8.0%, indicating insufficient controlled atmosphere intensity. The oxygen volume fraction of Comparative Example 2 dropped to below 3.2% in the early stage of storage and further dropped to about 1.0%, while the carbon dioxide rose to 17.0%, indicating excessive consumption of oxygen and insufficient oxygen replenishment. Although Comparative Example 3 had an oxygen absorption system, due to air leakage and structural interference, the headspace gas was around 8.0% O2 / 10.5% CO2 and fluctuated more. The above differences indicate that Examples 1-3 do not rely solely on oxygen intake or solely on perforation. Instead, they provide a controlled oxygen supply channel through the central perforation area and a controlled oxygen intake channel through the circumferential sealing strip area, thereby reducing the mutual cancellation or excessive superposition of the two and allowing the headspace gas to enter a more controllable and stable range.

[0112] (4) The results of strawberry quality show that when stored at 4 ℃ for 10 days, the decay rate of Examples 1 to 3 was 4% to 6%, the weight loss rate was 1.4% to 1.7%, the hardness was 1.22 to 1.30 N, and the off-odor score was about 1.4 to 1.5; after being transferred to a shelf at 20 ℃ for 2 days, the decay rate was still controlled at 7% to 10%, and the off-odor score was maintained at 1.5 to 1.7. Comparative Example 1 showed a rot rate that increased to 15% and 22% in the two stages, respectively, with more significant deterioration in weight loss and hardness, indicating that micro-perforation alone is insufficient to provide a modified atmosphere environment that can effectively suppress quality deterioration. Comparative Example 2, although having a lower weight loss rate, showed a significantly higher off-odor score (3.2 on Day 10 and 3.8 on Day 12), indicating that relying solely on oxygen absorption without controlled oxygen supplementation makes it easier to enter a low-oxygen, near-anaerobic zone, leading to undesirable flavors. Comparative Example 3 had the worst rot rate, weight loss rate, and hardness, consistent with its decreased heat seal strength and increased leakage rate, indicating that improper structural arrangement can simultaneously weaken sealing and modified atmosphere control, thereby amplifying quality deterioration.

[0113] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A microporous barrier synergistic preservation film, characterized in that, Includes base film, oxygen-absorbing coating, and capping layer; The base film comprises an outer layer, a barrier layer, and an inner layer stacked sequentially from the outside to the inside, wherein the inner layer is a heat-sealing layer; The plastic wrap includes a central perforated area and a circumferential sealing strip area on its surface. The circumferential sealing strip area is continuously arranged along at least one side of the plastic wrap, and the central perforated area and the circumferential sealing strip area do not overlap on the film surface. The central perforated area is provided with a group of micro-perforations penetrating the outer layer, the barrier layer, and the inner layer. The pore size of the micro-perforations is 20–150 μm, and the pore density is 50–5000 pores / m². 2 ; The circumferential sealing strip area is provided with a heat-sealing reserved strip area along the edge of the plastic wrap. The width of the heat-sealing reserved strip area is 2-15mm, and the oxygen-absorbing coating is not provided in the heat-sealing reserved strip area. The oxygen-absorbing coating is disposed on the inner surface of the inner layer and confined within the circumferential sealing strip area. The oxygen-absorbing coating includes a base coating and an oxygen-absorbing layer, with the base coating located between the inner layer and the oxygen-absorbing layer. The covering layer covers the oxygen-absorbing layer and is confined within the circumferential sealing strip area. The covering layer includes an encapsulation layer and a heat-sealing compatible layer.

2. The microporous barrier synergistic preservation film according to claim 1, characterized in that, The width of the circumferential sealing strip area is 5-60 mm, and the distance from the inner boundary of the circumferential sealing strip area to the nearest edge of the plastic wrap is 0-10 mm; the thickness of the oxygen-absorbing layer is 2-30 μm, and the oxygen-absorbing layer consists of multiple oxygen-absorbing coating strips extending along the edge of the plastic wrap within the circumferential sealing strip area, with the width of a single oxygen-absorbing coating strip being 0.5-8 mm and the spacing between two adjacent oxygen-absorbing coating strips being 0.5-12 mm; the pitch of the oxygen-absorbing coating strips is 1-5 times the center-to-center distance between two adjacent holes in the central perforation area.

3. The microporous barrier synergistic preservation film according to claim 1, characterized in that... The micro-perforated group forms a regular array within the central perforated area, with the center distance between two adjacent holes being 2 to 25 mm.

4. The microporous barrier synergistic preservation film according to claim 1, characterized in that, The barrier layer is an ethylene-vinyl alcohol copolymer layer, wherein the ethylene molar fraction in the ethylene-vinyl alcohol copolymer is 24-48 mol%, and the thickness of the barrier layer is 3-20 μm.

5. The microporous barrier synergistic preservation film according to claim 1, characterized in that, The base coating comprises a modified polyolefin bonding resin and an inorganic thickening filler. The modified polyolefin bonding resin is maleic anhydride-grafted polyethylene and / or maleic anhydride-grafted polypropylene. The inorganic thickening filler is fumed silica and / or nano-calcium carbonate. The thickness of the base coating is 0.2–5 μm. The oxygen-absorbing layer comprises a polymer binder phase and oxygen-absorbing composite particles dispersed in the polymer binder phase. The oxygen-absorbing composite particles are prepared from metallic iron powder, sodium chloride, molecular sieve, and a water-soluble granulating agent. The metallic iron powder accounts for 60-90% of the mass of the oxygen-absorbing composite particles, sodium chloride accounts for 0.3-3%, molecular sieve accounts for 2-20%, and water-soluble granulating agent accounts for 3-15%. The water-soluble granulating agent is one or two of polyvinyl alcohol, sodium carboxymethyl cellulose, and polyvinylpyrrolidone. The median particle size of the oxygen-absorbing composite particles is 30-300 μm.

6. The microporous barrier synergistic preservation film according to claim 1, characterized in that, The encapsulation layer is one of ethylene-vinyl acetate copolymer, thermoplastic polyurethane, or polyethylene, and the thickness of the encapsulation layer is 0.5–8 μm. The heat-sealable compatibility layer is linear low-density polyethylene and / or metallocene linear low-density polyethylene, and the thickness of the heat-sealable compatibility layer is 0.5 to 15 μm; The heat-sealing compatible layer is continuously arranged along the edge of the cling film and covers the circumferential sealing strip area; the encapsulation layer is limited within the circumferential sealing strip area and avoids the heat-sealing reserved strip area, and the encapsulation layer forms a 1-10 mm overlap width on the film surface over the outer boundary of the oxygen-absorbing layer.

7. A method for preparing a microporous barrier-synergistic preservation film according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1, a base film comprising an outer layer, a barrier layer and an inner layer is prepared by co-extrusion, wherein the inner layer is a heat-sealing layer; S2, the inner surface of the inner layer of the base film is subjected to corona treatment, with a corona treatment power density of 0.5–3.0 kW·min / m. 2 ; S3, using a patterned coating method, the primer liquid is applied only to the circumferential sealing strip area and dried to form a primer layer, and a heat-sealing reserved strip area with a width of 2 to 15 mm is reserved along the edge of the plastic wrap in the circumferential sealing strip area; S4, using a patterned coating method, the oxygen-absorbing coating liquid is applied only to the circumferential sealing strip area and dried to form an oxygen-absorbing layer. The oxygen-absorbing layer consists of multiple oxygen-absorbing coating strips extending along the edge direction, and the oxygen-absorbing coating strips avoid the heat-sealing reserved strip area. S5, a covering layer is formed in the circumferential sealing strip area to cover the oxygen-absorbing layer, a sealing layer is first formed and the heat-sealing reserved strip area is avoided, and then a heat-sealing compatible layer is formed continuously along the edge of the plastic wrap. S6, laser micro-perforation is performed in the central perforation area to form a group of micro-perforations that penetrate the base film, and the group of micro-perforations does not overlap with the oxygen-absorbing coating on the film surface.

8. The method for preparing a microporous barrier-synergistic preservation film according to claim 7, characterized in that, The patterned coating method is one of gravure coating, flexographic coating or slot coating, and the width of the circumferential sealing strip area is limited to 5-60mm by a mask, a positioning coating roller or a positioning doctor blade, and the width of the heat-sealing reserved strip area is limited to 2-15mm.

9. The method for preparing a microporous barrier-synergistic preservation film according to claim 7, characterized in that, The oxygen-absorbing composite particles are obtained by spray granulation, with an inlet air temperature of 120–200°C. The oxygen-absorbing coating liquid comprises 70–95% oxygen-absorbing composite particles and 5–30% polymer binder phase by weight of solid components. The dry coating weight of the oxygen-absorbing layer is 0.5–12 g / m². 2 The drying temperature is 40–80°C, and the drying time is 1–10 min.

10. The method for preparing a microporous barrier-synergistic preservation film according to claim 7, characterized in that, The laser micro-perforation uses a CO2 laser with a wavelength of 9.3–10.6 μm, a single pulse energy of 0.1–3.0 mJ, and a pulse frequency of 1–50 kHz.

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