Polyamide fresh-keeping composite film with oxygen absorption function and preparation method thereof

Abstract

The application discloses a polyamide fresh-keeping composite film with oxygen absorption function, which comprises, from top to bottom, a polyamide surface layer, a first oxygen absorption layer, a barrier core layer, a second oxygen absorption layer and a polyamide heat sealing layer; wherein the polyamide surface layer is composed of the following raw materials in mass percentage: 93-99% PA6, 0.5-3.5% slip agent and 0.5-3.5% opening agent; the first oxygen absorption layer and the second oxygen absorption layer are composed of the following raw materials in mass percentage: 10-38% PA6, 60-80% MXD6 and 2.0-10% modified oxygen absorption barrier agent; the modified oxygen absorption barrier agent is a layered inorganic particle loaded with an oxygen absorber; the barrier core layer is 100% EVOH; and the polyamide heat sealing layer is composed of the following raw materials in mass percentage: 87-99% copolymerized nylon, 0.25-2% opening agent, 0.25-1% slip agent and 0.5-10% water absorbing agent. The first oxygen absorption layer and the second oxygen absorption layer can effectively reduce the oxygen content in the package, maintain the freshness of the content by the synergistic effect of the layers, slow down the deterioration reaction of the content caused by oxygen, and achieve the fresh-keeping effect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polyamide film, and particularly relates to a polyamide fresh-keeping composite film with oxygen absorption function and a preparation method thereof. BACKGROUND

[0002] During packaging or storage, food is prone to spoilage, discoloration and other deterioration phenomena caused by oxygen, thereby affecting the quality of food, and even affecting the health of consumers. Moreover, nutrients in food are prone to deterioration in a high-oxygen environment, for example, fat can spoil and deteriorate in a high-oxygen environment, and pigments in food can also discolor or lose color due to the influence of oxygen, thereby affecting the color and flavor of food. Most aerobic bacteria and facultative anaerobic bacteria can grow well in an aerobic environment, and biochemical reactions can still occur even if the oxygen content is as low as 2-3%.

[0003] Modified atmosphere packaging and vacuum packaging are currently the main methods for reducing the oxygen content in packaging bags, but there is still a small amount (0.1-2.0%) of residual oxygen remaining in the packaging container.

[0004] Oxygen-absorbing packaging can absorb oxygen permeating into the packaging from the inside and the outside environment, keep the oxygen environment in the packaging at a low level, prevent the oxidation and deterioration of the contents of the packaging, maintain the freshness of the contents, and prolong the shelf life.

[0005] Iron-based bagged oxygen absorbers are the most widely used oxygen absorbers on the market. Iron powder oxygen absorbers are placed in small bags and then placed in food packaging bags. When the water activity in the packaging is high, the iron powder can actively absorb oxygen in the packaging bag, thereby reducing the oxygen content in the packaging bag. However, this form of bagged oxygen absorber has the risk of accidental ingestion and leakage, and because its main oxygen-absorbing component is iron or ferrous salt, it cannot pass through the metal detector on the packaging line, posing a safety hazard.

[0006] In view of the problems of the above-mentioned bagged iron-based oxygen absorber, people have begun to try to add organic oxygen absorbers to resins to prepare oxygen-absorbing films. Compared with bagged iron-based oxygen absorbers, oxygen-absorbing films have a broader market application prospect.

[0007] The Chinese patent application with the application number CN201811399199.4 discloses a high oxygen barrier film and its preparation method and application. The high oxygen barrier film comprises, from outside to inside, an outer layer A, a bonding layer B1, an oxygen absorbing layer C1, a bonding layer B2, a barrier layer D, a bonding layer B3, an oxygen absorbing layer C2 and a heat sealing layer E. The oxygen absorbing layers C1 and C2 are composed of an oxygen absorbing agent and a polyolefin resin, and the main component of the oxygen absorbing agent is ethyl propylene methacrylate and / or cyclohexene acrylate terpolymer. The high oxygen barrier film of the invention introduces an oxygen absorbing layer composed of an oxygen absorbing agent and a polyolefin resin. The oxygen absorbing agent can generate free radicals under ultraviolet irradiation before packaging, and the free radicals combine with oxygen to achieve the effect of oxygen absorption, effectively block the transmission of oxygen, and greatly improve the oxygen barrier performance of the film. However, the film has many layers, and the preparation process requires multiple processes to be carried out at the same time, which is relatively complicated. Therefore, there is an urgent need to research a polyamide fresh-keeping composite film with oxygen absorption function. SUMMARY

[0008] To solve the above problems, the present application provides a polyamide fresh-keeping composite film with oxygen absorption function and its preparation method. The present application gives the film good oxygen barrier property by setting the barrier core layer, effectively reduces the oxygen content in the package by setting the first and second oxygen absorbing layers, and maintains the freshness of the contents by the synergistic effect of each layer, slows down the deterioration reaction caused by oxygen, and achieves the effect of fresh-keeping.

[0009] The technical scheme of the present application is as follows:

[0010] One of the objects of the present application is to provide a polyamide fresh-keeping composite film with oxygen absorption function, which comprises, from top to bottom, a polyamide surface layer, a first oxygen absorbing layer, a barrier core layer, a second oxygen absorbing layer and a polyamide heat sealing layer.

[0011] The polyamide surface layer is composed of the following raw materials in mass percentage: 93-99% PA6, 0.5-3.5% slip agent, 0.5-3.5% opening agent.

[0012] The first and second oxygen absorbing layers are composed of the following raw materials in mass percentage: 10-38% PA6, 60-80% MXD6, 2.0-10% modified oxygen absorbing barrier agent. The modified oxygen absorbing barrier agent is a layered inorganic particle loaded with an oxygen absorbing agent.

[0013] The barrier core layer is 100% EVOH.

[0014] The polyamide heat sealing layer is composed of the following raw materials in mass percentage: 87-99% copolymer nylon, 0.25-2% opening agent, 0.25-1% slip agent, 0.5-10% water absorbing agent.

[0015] Further, in the modified oxygen-absorbing barrier agent, the layered inorganic particles are one or a combination of nano-silica, nano-mica, nano-montmorillonite, layered double hydroxide, kaolin, nano-alumina.

[0016] Further, in the modified oxygen-absorbing barrier agent, the oxygen absorber is one or a combination of ascorbic acid-based oxygen absorbers, unsaturated fatty acid-based oxygen absorbers, and phenolic hydroxyl-based oxygen absorbers.

[0017] Further, in the polyamide surface layer and the polyamide heat-seal layer, the slip agent is one or a combination of erucic acid amide, oleic acid amide, ethylene bis-stearamide, silicone powder, silicone oil, polyethylene wax, and oxidized polyethylene wax.

[0018] Further, in the polyamide surface layer and the polyamide heat-seal layer, the opening agent is one or a combination of silicon dioxide, talc, kaolin, calcium carbonate, clay, magnesium carbonate, barium carbonate, calcium phosphate, aluminum oxide, and titanium dioxide.

[0019] Further, in the barrier core layer, the ethylene molar content of the EVOH is 20-40% mol / L.

[0020] Further, in the polyamide heat-seal layer, the water-absorbing agent is one or a combination of calcium oxide and calcium hydroxide.

[0021] Further, the total thickness of the composite film is 30-90 μm, and the thickness ratio of the polyamide surface layer, the first oxygen-absorbing layer, the barrier core layer, the second oxygen-absorbing layer, and the heat-seal layer is 1:2:(1-2):2:(0.5-1).

[0022] The second object of the present application is to provide a preparation method of a polyamide freshness-keeping composite film with oxygen-absorbing function, comprising the following steps:

[0023] S1: weighing each raw material according to the set proportion, mixing each layer of raw material, and uniformly dispersing through a high-speed stirrer;

[0024] S2: melting and extruding each layer of raw material through a respective extruder, flowing out through a T-shaped die, and cooling on a chill roll to form an unstretched sheet;

[0025] S3: after the unstretched sheet is moisturized through a water tank, it is heated for transverse synchronous stretching;

[0026] S4: the stretched film is heat-set to obtain the polyamide freshness-keeping composite film with oxygen-absorbing function.

[0027] Further, in step S3, the stretching temperature is 160-210°C, and the stretching ratio is 2.5*2.5-3.2*3.2.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] The polyamide fresh-keeping composite film with oxygen absorption function provided by the present application can help maintain the freshness of the packaging content and effectively prolong the shelf life of the content. The first oxygen absorption layer and the second oxygen absorption layer can absorb the original oxygen in the package and the oxygen permeating into the package from the outside, effectively reducing the oxygen content in the package and slowing down the deterioration reaction caused by oxygen. In addition, the organic oxygen absorber used in the oxygen absorption layer also has certain antibacterial effect, which can inhibit the occurrence of spoilage reaction caused by microorganisms. The modified oxygen absorption barrier agent in the first oxygen absorption layer and the second oxygen absorption layer of the present application is a layered inorganic particle loaded with an oxygen absorber. The layered inorganic particle can not only improve the thermal stability of the oxygen absorber, but also form a "zigzag path" to extend the gas permeation path and hinder the diffusion of gas in the matrix, thereby improving the gas barrier property of the film. The raw materials MXD6 and EVOH of the first oxygen absorption layer and the second oxygen absorption layer of the present application both have good oxygen barrier property, but the barrier property of EVOH is negatively correlated with humidity, and the barrier property of MXD6 does not change with humidity. The MXD6 in the oxygen absorption layer can still maintain good oxygen barrier property in different humidity environments after the oxygen absorber loses its effectiveness. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The structure diagram of the polyamide fresh-keeping composite film with oxygen absorption function provided by the present application is shown.

[0031] In the figure, 1 is a polyamide surface layer, 2 is a first oxygen absorption layer, 3 is a barrier core layer, 4 is a second oxygen absorption layer, and 5 is a polyamide heat-sealing layer. DETAILED DESCRIPTION

[0032] The preferred embodiments will be described below, and the accompanying drawings will be referred to. Figure 1 The present application is further described below, and the endpoints of the ranges and any values disclosed in the present application are not limited to the precise values or ranges set forth; these ranges and values should be interpreted as approximations; the endpoints of the ranges of values and the individual values are included in the ranges; the individual values can be combined with each other to form one or more new ranges of values, which should be considered as specifically disclosed herein; the materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified; the experimental methods used in the following examples are conventional methods unless otherwise specified.

[0033] Example 1

[0034] The embodiment provides a polyamide fresh-keeping composite film with an oxygen absorption function, which comprises, from top to bottom, a polyamide surface layer, a first oxygen absorption layer, a barrier core layer, a second oxygen absorption layer and a polyamide heat sealing layer.

[0035] The polyamide surface layer is composed of the following raw materials in percentage by mass: 95% PA6, 2.5% slip agent, 2.5% opening agent.

[0036] The first oxygen absorption layer and the second oxygen absorption layer are composed of the following raw materials in percentage by mass: 30% PA6, 60% MXD6, 10% modified oxygen absorption barrier agent.

[0037] The modified oxygen absorption barrier agent is a layered inorganic particle loaded with an oxygen absorber.

[0038] The barrier core layer is 100% EVOH.

[0039] The polyamide heat sealing layer is composed of the following raw materials in percentage by mass: 95% copolymerized nylon, 2% opening agent, 1% slip agent, 2% water absorption agent.

[0040] In the embodiment, the modified oxygen absorption barrier agent is a cinnamic acid modified layered metal oxide, wherein the layered inorganic particle is zinc-aluminum-based LDHs, and the oxygen absorber is cinnamic acid.

[0041] In the embodiment, the slip agent in the polyamide surface layer and the polyamide heat sealing layer is erucic acid amide, and the opening agent is a combination of two kinds of silicon dioxide and talcum powder. In the barrier core layer, the ethylene molar content of EVOH is 30% mol / L. In the polyamide heat sealing layer, the water absorption agent is calcium oxide. The total thickness of the composite film is 40 mu m, and the thickness ratio of the polyamide surface layer, the first oxygen absorption layer, the barrier core layer, the second oxygen absorption layer and the heat sealing layer is 1:2:2:2:1.

[0042] The embodiment also provides a preparation method of a polyamide fresh-keeping composite film with an oxygen absorption function, comprising the following steps:

[0043] S1: weighing each raw material according to a set proportion, mixing each layer of raw material, and uniformly dispersing through a high-speed stirrer;

[0044] S2: melting and extruding each layer of raw material through a respective extruder, flowing out through a T-shaped die, and cooling on a chill roller to form an unstretched sheet;

[0045] S3: after the unstretched sheet is humidified through a water tank, the unstretched sheet is heated and synchronously stretched in the transverse direction;

[0046] S4: the stretched film is heat set to obtain the polyamide fresh-keeping composite film with an oxygen absorption function.

[0047] In step S3 of this embodiment, the stretching temperature is 200℃, and the stretching ratio is 3.0*3.0.

[0048] Embodiment 2

[0049] The polyamide fresh-keeping composite film with oxygen absorption function comprises, from top to bottom, a polyamide surface layer, a first oxygen absorption layer, a barrier core layer, a second oxygen absorption layer, and a polyamide heat-sealing layer.

[0050] The polyamide surface layer is composed of the following raw materials in mass percentage: 93% PA6, 3.5% slip agent, and 3.5% opening agent.

[0051] The first and second oxygen absorption layers are composed of the following raw materials in mass percentage: 38% PA6, 60% MXD6, and 2% modified oxygen absorption barrier agent.

[0052] The modified oxygen absorption barrier agent is layered inorganic particles loaded with an oxygen absorber.

[0053] The barrier core layer is 100% EVOH.

[0054] The polyamide heat-sealing layer is composed of the following raw materials in mass percentage: 99% copolymerized nylon, 0.25% opening agent, 0.25% slip agent, and 0.5% water absorption agent.

[0055] In this embodiment, the modified oxygen absorption barrier agent is nano montmorillonite modified by gallic acid, wherein the layered inorganic particles are nano montmorillonite, and the oxygen absorber is gallic acid.

[0056] In this embodiment, the slip agent in the polyamide surface layer and the polyamide heat-sealing layer is a combination of oleic acid amide and silicone oil, and the opening agent is kaolin. In the barrier core layer, the ethylene molar content of EVOH is 20% mol / L. In the polyamide heat-sealing layer, the water absorption agent is calcium oxide. The total thickness of the composite film is 40μm, and the thickness ratio of the polyamide surface layer, the first oxygen absorption layer, the barrier core layer, the second oxygen absorption layer, and the heat-sealing layer is 1:2:2:2:1.

[0057] The embodiment also provides a preparation method of a polyamide fresh-keeping composite film with oxygen absorption function, comprising the following steps:

[0058] S1: weigh each raw material according to the set proportion, mix each layer of raw material, and disperse uniformly through a high-speed stirrer;

[0059] S2: melt and extrude each layer of raw material through a respective extruder, flow out through a T-shaped die, and cool on a chill roller to form an unstretched sheet;

[0060] S3: After the unstretched sheet is moisturized by passing through a water tank, it is heated for transverse synchronous stretching;

[0061] S4: The stretched film is heat set to obtain the polyamide fresh-keeping composite film with oxygen absorption function.

[0062] In step S3 of this embodiment, the stretching temperature is 160°C, and the stretching ratio is 2.5*2.5.

[0063] Embodiment 3

[0064] The polyamide fresh-keeping composite film with oxygen absorption function comprises, from top to bottom, a polyamide surface layer, a first oxygen absorption layer, a barrier core layer, a second oxygen absorption layer, and a polyamide heat sealing layer.

[0065] The polyamide surface layer is composed of the following raw materials in mass percentage: 99% PA6, 0.5% slip agent, and 0.5% opening agent.

[0066] The first oxygen absorption layer and the second oxygen absorption layer are composed of the following raw materials in mass percentage: 15% PA6, 80% MXD6, and 5% modified oxygen absorption barrier agent.

[0067] The modified oxygen absorption barrier agent is layered inorganic particles loaded with an oxygen absorber.

[0068] The barrier core layer is 100% EVOH.

[0069] The polyamide heat sealing layer is composed of the following raw materials in mass percentage: 87% copolymerized nylon, 2% opening agent, 1% slip agent, and 10% water absorbing agent.

[0070] In this embodiment, the modified oxygen absorption barrier agent is tea polyphenol modified layered metal oxide, wherein the layered inorganic particles are magnesium aluminum-based LDHs, and the oxygen absorber is tea polyphenol.

[0071] In this embodiment, in the polyamide surface layer and the polyamide heat sealing layer, the slip agent is polyethylene wax, and the opening agent is a combination of calcium carbonate and clay. In the barrier core layer, the ethylene molar content of EVOH is 40% mol / L. In the polyamide heat sealing layer, the water absorbing agent is calcium oxide. The total thickness of the composite film is 40 pm, and the thickness ratio of the polyamide surface layer, the first oxygen absorption layer, the barrier core layer, the second oxygen absorption layer, and the heat sealing layer is 1:2:2:2:1.

[0072] The embodiment also provides a preparation method of a polyamide fresh-keeping composite film with oxygen absorption function, comprising the following steps:

[0073] S1: Weigh each raw material according to the set proportion, mix each layer of raw material, and disperse uniformly by a high-speed mixer.

[0074] S2: melt-extruding each layer of raw material through a respective extruder, flowing through a T-shaped die, and cooling on a chill roll to form an unstretched sheet;

[0075] S3: after moisturizing the unstretched sheet through a water tank, heating and performing transverse synchronous stretching;

[0076] S4: performing heat setting treatment on the stretched film to obtain the polyamide fresh-keeping composite film with oxygen absorption function.

[0077] In step S3 of this embodiment, the stretching temperature is 210°C, and the stretching ratio is 3.2*3.2.

[0078] Embodiment 4

[0079] This embodiment provides a polyamide fresh-keeping composite film with oxygen absorption function, which comprises, from top to bottom, a polyamide surface layer, a first oxygen absorption layer, a barrier core layer, a second oxygen absorption layer, and a polyamide heat sealing layer.

[0080] The polyamide surface layer is composed of the following raw materials in mass percentage: 93% PA6, 3.5% slip agent, and 3.5% opening agent.

[0081] The first and second oxygen absorption layers are composed of the following raw materials in mass percentage: 10% PA6, 80% MXD6, and 10% modified oxygen absorption barrier agent.

[0082] The modified oxygen absorption barrier agent is a layered inorganic particle loaded with an oxygen absorber.

[0083] The barrier core layer is 100% EVOH.

[0084] The polyamide heat sealing layer is composed of the following raw materials in mass percentage: 98% copolymerized nylon, 0.5% opening agent, 0.5% slip agent, and 1% water absorbing agent.

[0085] In this embodiment, the modified oxygen absorption barrier agent is a gallic acid modified layered metal oxide, wherein the layered inorganic particle is zinc-aluminum-based LDHs, and the oxygen absorber is gallic acid.

[0086] In this embodiment, in the polyamide surface layer and the polyamide heat sealing layer, the slip agent is a combination of two kinds of oxidized polyethylene wax, and the opening agent is kaolin. In the barrier core layer, the ethylene molar content of EVOH is 30% mol / L. In the polyamide heat sealing layer, the water absorbing agent is calcium oxide. The total thickness of the composite film is 40 μm, and the thickness ratio of the polyamide surface layer, the first oxygen absorption layer, the barrier core layer, the second oxygen absorption layer, and the heat sealing layer is 1:2:1:2:0.5.

[0087] The embodiment also provides a preparation method of the polyamide fresh-keeping composite film with oxygen absorption function, comprising the following steps:

[0088] S1: weighing each raw material according to a set proportion, mixing each layer of raw materials respectively, and uniformly dispersing through a high-speed stirrer;

[0089] S2: melting and extruding each layer of raw materials through a respective extruder, flowing out through a T-shaped die head, and cooling on a chill roller to form an unstretched sheet;

[0090] S3: after the unstretched sheet is moisturized through a water tank, the unstretched sheet is heated and transversely stretched synchronously;

[0091] S4: the stretched film is heat set to obtain the polyamide fresh-keeping composite film with oxygen absorption function.

[0092] In step S3 of the embodiment, the stretching temperature is 160°C, and the stretching ratio is 2.5*2.5.

[0093] Example 5

[0094] The embodiment is basically the same as example 1, except that in the embodiment, the water absorbent of the polyamide heat sealing layer is a combination of calcium oxide and calcium hydroxide. The total thickness of the polyamide fresh-keeping composite film of the embodiment is 30 μm, and the thickness ratio of the polyamide surface layer, the first oxygen absorption layer, the barrier core layer, the second oxygen absorption layer and the heat sealing layer is 1:2:1.5:2:0.8.

[0095] Example 6

[0096] The embodiment is basically the same as example 1, except that in the embodiment, the water absorbent of the polyamide heat sealing layer is calcium hydroxide. The total thickness of the polyamide fresh-keeping composite film of the embodiment is 90 μm.

[0097] In the embodiment, in the modified oxygen absorption barrier agent, the layered inorganic particles can also be selected from one or a combination of nano-silicon dioxide, nano-mica, nano-montmorillonite, layered double hydroxide, kaolin and nano-aluminum oxide, and the oxygen absorber can also be selected from one or a combination of ascorbic acid series oxygen absorbers, gallic acid series oxygen absorbers, unsaturated fatty acid series oxygen absorbers and natural classification oxygen absorbers; in the polyamide surface layer and the polyamide heat sealing layer, the slip agent can also be selected from one or a combination of erucic acid amide, oleic acid amide, ethylene bis-stearamide, silicone powder, silicone oil, polyethylene wax and oxidized polyethylene wax, and the opening agent can also be selected from one or a combination of silicon dioxide, talc, kaolin, calcium carbonate, clay, magnesium carbonate, barium carbonate, calcium phosphate, aluminum oxide and titanium dioxide.

[0098] Comparative Example 1

[0099] The difference from Example 1 is that the oxygen absorbing barrier in the first and second oxygen absorbing layers of the present comparative example is not modified by cinnamic acid.

[0100] Comparative Example 2

[0101] The difference from Example 1 is that the first and second oxygen absorbing layers of the present comparative example do not contain modified oxygen absorbing barrier.

[0102] The first and second oxygen absorbing layers of the present comparative example are composed of the following raw materials in mass percentage: 30% PA6, 70% MXD6.

[0103] Evaluation of implementation effect

[0104] The excellent effects achieved by the present application are further illustrated below by specific tests on the composite films prepared in Examples 1-6 and Comparative Examples 1-2:

[0105] Tensile strength and elongation at break: tested according to the relevant standards of GB / T 1040;

[0106] Oxygen transmission rate: tested according to the relevant standards of ASTM D3985;

[0107] Freshness retention: evaluated by sensory evaluation method. After the film is made into a bag and sealed with a certain amount of fresh garlic paste, it is stored in a cool place for one week, and then the appearance and flavor of the garlic paste are observed and compared. Freshness retention is rated as o (excellent), □ (good), △ (average), and × (poor).

[0108] The test results are shown in the following table:

[0109] Table 1 Performance test result statistics

[0110]

[0111] From the test results of Example 1 and Comparative Example 1, it can be seen that compared with Example 1, the unmodified layered inorganic particles in Comparative Example 1 have poor dispersibility in the polymer matrix, resulting in reduced mechanical properties of the film, and do not have oxygen absorbing barrier function, so the film has poor barrier properties.

[0112] From the test results of Example 1 and Comparative Example 2, it can be seen that compared with Example 1, Comparative Example 2 does not contain layered inorganic particles, and has poor barrier properties.

[0113] From the test results of Example 1 and commercially available ordinary BOPA / CPP composite film, it can be seen that compared with commercially available ordinary BOPA / CPP composite film, the polyamide surface layer, the first oxygen absorbing layer, the barrier core layer, the second oxygen absorbing layer, and the polyamide heat-sealing layer contained in Example 1 make the composite film have good barrier properties and freshness retention, which can help maintain the freshness of the packaged contents and effectively prolong the shelf life.

[0114] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all belong to the protection scope of the present application.

Claims

1. A polyamide freshness-keeping composite film with oxygen absorption function, characterized in that, The polyamide freshness-locking composite film with oxygen absorption function comprises, from top to bottom: a polyamide surface layer, a first oxygen absorption layer, a barrier core layer, a second oxygen absorption layer, and a polyamide heat-sealing layer; The polyamide surface layer is composed of the following raw materials in weight percentages: 93-99% PA6, 0.5-3.5%... Slip agent, 0.5-3.5% opening agent; The first and second oxygen-absorbing layers are composed of the following raw materials by mass percentage: 10-38% PA6, 60-80% MXD6, 2.0-10% modified oxygen-absorbing barrier agent; the modified oxygen-absorbing barrier agent is loaded with oxygen-absorbing... Layered inorganic particles of oxygen-producing agents; The barrier core layer is 100% EVOH; The polyamide heat-sealing layer is composed of the following raw materials in weight percentages: 87-99% copolynylon, 0.25-2% opening agent, 0.25-1% slip agent, and 0.5-10% water absorbent.

2. The polyamide freshness-keeping composite film with oxygen absorption function according to claim 1, characterized in that, In the modified oxygen-absorbing barrier agent, the layered inorganic particles are one or a combination of several of nano-silica, nano-mica, nano-montmorillonite, layered double hydroxides, kaolin, and nano-alumina.

3. The polyamide freshness-keeping composite film with oxygen absorption function according to claim 1, characterized in that, The modified oxygen-absorbing barrier agent is one or a combination of ascorbic acid-based oxygen-absorbing agents, unsaturated fatty acid-based oxygen-absorbing agents, and phenolic hydroxyl-based oxygen-absorbing agents.

4. The polyamide freshness-keeping composite film with oxygen absorption function according to claim 1, characterized in that, In the polyamide surface layer and the polyamide heat-sealing layer, the slip agent is one or a combination of several of the following: erucamide, oleamide, ethylene bis-stearamide, silicone powder, silicone oil, polyethylene wax, and oxidized polyethylene wax.

5. The polyamide freshness-keeping composite film with oxygen absorption function according to claim 1, characterized in that, In the polyamide surface layer and the polyamide heat-sealing layer, the opening agent is one or a combination of several of the following: silica, talc, kaolin, calcium carbonate, clay, magnesium carbonate, barium carbonate, calcium phosphate, alumina, and titanium dioxide.

6. The polyamide freshness-keeping composite film with oxygen absorption function according to claim 1, characterized in that, In the barrier core layer, the ethylene molar content of EVOH is 20-40% mol / L.

7. The polyamide freshness-keeping composite film with oxygen absorption function according to claim 1, characterized in that, In the polyamide heat-sealing layer, the water-absorbing agent is one or a combination of calcium oxide and calcium hydroxide.

8. The polyamide freshness-keeping composite film with oxygen absorption function according to claim 1, characterized in that, The total thickness of the composite film is 30-90 μm, wherein the thickness ratio of the polyamide surface layer, the first oxygen-absorbing layer, the barrier core layer, the second oxygen-absorbing layer, and the heat-sealing layer is 1:2:(1-2):2:(0.5-1).

9. The method for preparing a polyamide fresh-keeping composite film with oxygen absorption function according to any one of claims 1-8, characterized in that, Includes the following steps: S1: Weigh each raw material according to the set ratio, mix each layer of raw material separately, and disperse them evenly using a high-speed mixer; S2: The raw materials of each layer are melted and extruded through their respective extruders, flow out through the T-die, and cooled on the chiller roller to form an unstretched sheet; S3: After the unstretched sheet is humidified in a water tank, it is heated and stretched laterally simultaneously. S4: The stretched film is heat-set to obtain the polyamide freshness-locking composite film with oxygen absorption function.

10. The method for preparing a polyamide freshness-keeping composite film with oxygen absorption function according to claim 9, characterized in that, In step S3, the stretching temperature is 160-210℃, and the stretching ratio is 2.5*2.5-3.2*3.2.

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