Highly breathable multilayer co-extruded film and process for its preparation

Abstract

The application relates to the technical field of co-extrusion films, and particularly discloses a high-breathability multilayer co-extrusion film and a preparation process thereof. The high-breathability multilayer co-extrusion film comprises an inner layer, an intermediate layer and an outer layer arranged in sequence, the inner layer is an ethylene-vinyl acetate copolymer layer, the intermediate layer is an ethylene-vinyl acetate copolymer layer, and the outer layer is a linear low-density polyethylene layer; the VA content in the inner layer is 25%-30%, and the VA content in the intermediate layer is 10%-15%; and the preparation method comprises the following steps: S1, extrusion; S2, stretching; and S3, corona treatment. The high-breathability multilayer co-extrusion film can be used in culture bags in the pharmaceutical field such as cell culture bags, and has the advantages of high breathability, high barrier property, low cost and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of co-extrusion film, more particularly, it relates to a high-breathability multilayer co-extrusion film and a preparation process thereof. BACKGROUND

[0002] Cell culture bags are disposable consumables necessary for the research and production of cell therapy drugs in the biopharmaceutical industry. Cell culture bags, as containers for the culture and expansion of suspended cells, need to have good oxygen and carbon dioxide permeability to facilitate gas exchange for cell growth and respiration, and need to block water vapor to prevent the loss of water in the culture solution.

[0003] Traditional cell culture bag materials are fluorinated ethylene propylene copolymer films, commonly known as FEP films. This material has good oxygen and carbon dioxide permeability and extremely low water vapor permeability, as well as good chemical stability and mechanical strength, so it is widely used for the culture and expansion of immune cells. However, FEP material has extremely low surface energy, and for some cells that need to grow on a surface, it cannot provide a surface for them to grow on, so the culture bags made of this material are only suitable for the culture of suspended cells. At the same time, the raw material of FEP film is relatively expensive, and the processing temperature is above 300℃, so the fluorine element can corrode metal and produce toxic gases at high temperatures, so the production equipment and environment have high requirements. These factors make the cost of FEP material cell culture bags high, and because the material contains halogen elements, its application in the biopharmaceutical field has been restricted. Therefore, how to obtain a low-cost cell culture bag with high breathability and high barrier property is a problem that needs to be solved. SUMMARY

[0004] In order to obtain a low-cost, high-breathability, and high-barrier cell culture bag, the present application provides a high-breathability multilayer co-extrusion film and a preparation process thereof, which adopts the following technical solution:

[0005] In the first aspect, the present application provides a high-breathability multilayer co-extrusion film, which comprises an inner layer, an intermediate layer, and an outer layer arranged in sequence, the inner layer is an ethylene-vinyl acetate copolymer layer, the intermediate layer is an ethylene-vinyl acetate copolymer layer, and the outer layer is a linear low-density polyethylene layer, the VA content in the inner layer is 25%-30%, and the VA content in the intermediate layer is 10%-15%.

[0006] By adopting the technical scheme, EVA is used as the inner layer, which has excellent chemical stability and basically has no small molecule substance precipitation during cell culture process. From the molecular structure, the higher the VA content, the greater the polymer polarity and the lower the crystallinity, and the EVA has good barrier property to polar water vapor molecules and good permeability to non-polar oxygen and carbon dioxide molecules. The low-VA-content EVA used as the middle layer can improve the mechanical property and transparency of the film. The LLDPE used as the outer layer can further improve the mechanical strength and outer surface hardness of the film, avoid scratching of the film during processing and use, and form a temperature difference between the inner and outer layers during subsequent processing, facilitating processing.

[0007] Optionally, the outer layer comprises the following raw materials by weight:

[0008] 100 parts of LLDPE;

[0009] 3-5 parts of polyvinyl alcohol;

[0010] 5-10 parts of calcined oyster shell powder.

[0011] By adopting the technical scheme, the calcined oyster shell powder is preferably added to the outer layer, which can fill the LLDPE to improve the mechanical strength of the LLDPE and thus reduce the possibility of scratching of the outer layer. When the outer layer contacts water vapor, the calcined oyster shell powder can expand through hydration reaction, the irregular surface and porous structure change, and the barrier effect of the outer layer on water vapor can be improved.

[0012] Optionally, the calcined oyster shell powder is a modified oyster shell powder modified by a coupling agent.

[0013] By adopting the technical scheme, the coupling agent is used to modify the calcined oyster shell powder, which effectively improves the dispersion effect of the calcined oyster shell powder in the LLDPE, so that the calcined oyster shell powder can uniformly and fully fill the LLDPE, and thus the outer layer obtains uniform strength and water vapor barrier effect.

[0014] Optionally, the outer layer further comprises 1-2 parts by weight of orange peel powder.

[0015] By adopting the technical scheme, the orange peel powder is preferably added to the outer layer, which can cooperate with the calcined oyster shell powder to fill the LLDPE, so as to further improve the mechanical strength of the outer layer. At the same time, the orange peel powder has a large amount of flavonoids and functional groups such as hydroxyl and carbonyl groups, so the orange peel powder can form strong hydrogen bonds with polyvinyl alcohol, further improving the mechanical strength of the outer layer and reducing the possibility of scratching of the co-extruded film.

[0016] Optionally, the outer layer is subjected to electron beam irradiation crosslinking modification.

[0017] By adopting the technical scheme, the outer layer is subjected to electron beam irradiation treatment, under the impact of high-energy electron beams, the outer layer is more likely to be cross-linked, thereby the Ca ions in the calcined oyster shell powder are less likely to migrate, can be combined with water vapor in the outer layer, and the outer layer has better water vapor barrier effect and is less likely to affect the cells in the cell culture bag.

[0018] Optionally, the irradiation cross-linking treatment is performed in an electron beam accelerator irradiation cabin, the irradiation dose is 60-80 KGy, and the pulling rate is 2-5 m / s.

[0019] By adopting the technical scheme, under the treatment of the appropriate dose of electron beams, the outer layer can be appropriately cross-linked and less likely to have more chain segment breakage, effectively inhibiting the migration of Ca ions and maintaining the appropriate mechanical strength of the outer layer.

[0020] Optionally, the total thickness of the co-extrusion film is 90-110 μm, and the light transmittance of the co-extrusion film is > 90%.

[0021] By adopting the technical scheme, the light transmittance of the co-extrusion film is optimized, so as to observe the cell breeding condition in the cell culture bag.

[0022] Optionally, the thickness of the inner layer is 20-30 μm, the thickness of the intermediate layer is 40-50 μm, and the thickness of the outer layer is 20-30 μm.

[0023] By adopting the technical scheme, the thicknesses of the inner layer, the intermediate layer and the outer layer are optimized, the intermediate layer is thicker, and the mechanical properties and the transparency of the co-extrusion film are improved.

[0024] In a second aspect, the application provides a preparation process of a high-air-permeability multi-layer co-extrusion film, which adopts the following technical scheme:

[0025] The preparation process of the high-air-permeability multi-layer co-extrusion film comprises the following steps:

[0026] S1, extrusion: the raw materials of the inner layer, the intermediate layer and the outer layer are put into a three-layer co-extrusion film blowing machine, and then extruded to obtain a rough blank;

[0027] S2, stretching: the rough blank is subjected to longitudinal stretching and transverse stretching, the stretching ratio of the longitudinal stretching is 1.2-1.5, and the stretching ratio of the transverse stretching is 1.8-2.5, to obtain a stretched film;

[0028] S3, corona treatment: the stretched film is cut into two films, and subjected to plasma corona treatment to obtain a co-extrusion film.

[0029] By adopting the technical scheme, the porosity and pore diameter of the microstructure of the co-extrusion film are increased through the step-by-step bidirectional stretching process after the film is blown and extruded, and the air permeability of the film is further improved. The two films subjected to the corona treatment are immediately laminated and rolled up, and are sealed after being double-packaged, so that the films are prevented from contacting the external environment. The effect of the inner surface treatment of the film can be maintained for 1-2 years.

[0030] Optionally, the parameters of the plasma corona treatment in the step S3 are as follows: power 2kW-5kW, treatment temperature 30-40℃, and treatment time 40-60s.

[0031] By adopting the technical scheme, the water contact angle of the film surface after the treatment is improved from 120-130° to 45-70°.

[0032] Optionally, the bidirectionally stretched film has a large number of 0.1-0.3μm pores formed in the interior, which is more conducive to the diffusion of gas, and the oxygen permeability of the film is greater than 4000(cm 3 / m 2 ·24h·0.1MPa), and the carbon dioxide permeability of the film is greater than 10000(cm 3 / m 2 ·24h·0.1MPa).

[0033] In summary, the present application has the following beneficial effects:

[0034] 1. In the present application, EVA is used as the inner layer, which has excellent chemical stability, and basically no small molecule substances are precipitated during long-term contact with the culture medium in the cell culture process. From the molecular structure, because EVA introduces acetic acid groups on the ethylene branch, the higher the VA content, the greater the polymer polarity and the lower the crystallinity, which has good barrier property to polar water vapor molecules, and good permeability to non-polar oxygen and carbon dioxide molecules. The use of EVA with low VA content as the intermediate layer can improve the mechanical properties and transparency of the film. The use of LLDPE as the outer layer can further improve the mechanical strength and outer surface hardness of the film, avoid scratching the film during the processing and use processes, and form a temperature difference between the inner and outer layers during the subsequent processing process, thereby facilitating processing.

[0035] 2. In the present application, calcined oyster shell powder is preferably added to the outer layer, which can fill LLDPE to improve the mechanical strength of LLDPE, thereby reducing the possibility of scratching the outer layer. When the outer layer contacts water vapor, the calcined oyster shell powder can expand through a hydration reaction, the irregular surface porous structure changes, and the barrier effect of the outer layer to water vapor can be improved.

[0036] 3. In the method of the present application, the porosity and pore diameter of the microstructure of the co-extrusion film are increased through the step-by-step bidirectional stretching process after the film is blown and extruded, and the air permeability of the film is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram of the present application providing a co-extruded film. DETAILED DESCRIPTION

[0038] The present application is further described in detail below in conjunction with the examples.

[0039] Preparation Example

[0040] Preparation Example of Calcined Oyster Shell Powder

[0041] Preparation Example 1

[0042] The oyster shells were washed, dried, and then knocked into small pieces, which were placed in a 600℃ muffle furnace for calcination for 6h, ground, and sieved through a 100 mesh sieve to obtain calcined oyster shell powder.

[0043] Preparation Example 2

[0044] The calcined oyster shell powder was mixed with anhydrous ethanol in equal mass to obtain a mixture, 1% of a titanate coupling agent (1% of a silane coupling agent) was added to the mixture, and the mixture was continuously stirred and vacuum dried to obtain modified oyster shell powder.

[0045] Preparation Example of Outer Layer Raw Material

[0046] Preparation Example 3

[0047] 100kg of LLDPE, 3kg of polyvinyl alcohol, and 5kg of the calcined oyster shell powder prepared in Preparation Example 1 were taken respectively, mixed in a high-speed mixer for 8min, and uniformly discharged to obtain an outer layer raw material.

[0048] Preparation Example 4

[0049] 100kg of LLDPE, 4kg of polyvinyl alcohol, and 8kg of the calcined oyster shell powder prepared in Preparation Example 1 were taken respectively, mixed in a high-speed mixer for 8min, and uniformly discharged to obtain an outer layer raw material.

[0050] Preparation Example 5

[0051] 100kg of LLDPE, 5kg of polyvinyl alcohol, and 10kg of the calcined oyster shell powder prepared in Preparation Example 1 were taken respectively, mixed in a high-speed mixer for 8min, and uniformly discharged to obtain an outer layer raw material.

[0052] Preparation Example 6

[0053] 100kg of LLDPE, 3kg of polyvinyl alcohol, and 5kg of the calcined oyster shell powder prepared in Preparation Example 2 were taken respectively, mixed in a high-speed mixer for 8min, and uniformly discharged to obtain an outer layer raw material.

[0054] Preparation Example 7

[0055] Take 100 kg of LLDPE, 3 kg of polyvinyl alcohol, 5 kg of calcined oyster shell powder prepared in Preparation Example 2 and 1 kg of orange peel powder (100 mesh) respectively, mix them in a high-speed mixer for 8 min, and uniformly discharge to obtain the outer layer raw material.

[0056] Preparation Example 8

[0057] Take 100 kg of LLDPE, 3 kg of polyvinyl alcohol, 5 kg of calcined oyster shell powder prepared in Preparation Example 2 and 2 kg of orange peel powder (100 mesh) respectively, mix them in a high-speed mixer for 8 min, and uniformly discharge to obtain the outer layer raw material.

[0058] Example

[0059] Example 1

[0060] In one aspect, the application provides a high-breathability multilayer co-extrusion film, comprising an inner layer, an intermediate layer and an outer layer arranged in sequence, the inner layer is an ethylene-vinyl acetate copolymer layer, the intermediate layer is an ethylene-vinyl acetate copolymer layer, and the outer layer is a linear low-density polyethylene layer, the VA content in the inner layer is 25%, and the VA content in the intermediate layer is 10%. The thickness of the inner layer is 20 μm, the thickness of the intermediate layer is 50 μm, and the thickness of the outer layer is 20 μm.

[0061] In another aspect, the application provides a preparation process of a high-breathability multilayer co-extrusion film, comprising the following steps:

[0062] S1, extrusion: the raw materials of the inner layer, the intermediate layer and the outer layer are put into a three-layer co-extrusion film blowing machine, and then extruded, the melt extrusion temperature of the inner layer is 120-130 ℃, the melt extrusion temperature of the intermediate layer is 130-140 ℃, and the melt extrusion temperature of the outer layer is 140-150 ℃, to obtain a rough blank;

[0063] S2, stretching: the rough blank is preheated by a preheating roller before stretching, the preheating temperature is 70-90 ℃, which is above the glass transition temperature of the material and below the melting temperature, then longitudinally stretched and transversely stretched, the stretching ratio of the longitudinal stretching is 1.2, after the longitudinal stretching, the film passes through a constant temperature oven at a uniform speed of 0.5 m / s for heat treatment, the heat treatment temperature is 80-100 ℃, the stretching ratio of the transverse stretching is 1.8, after the transverse stretching, the film passes through a constant temperature oven at a uniform speed of 0.3 m / s for heat treatment, the heat treatment temperature is 90-100 ℃, and then cooled and shaped by a cooling roller, the cooling temperature is 25-35 ℃, to obtain a stretched film;

[0064] S3, corona treatment: the stretched film is cut into two films, and then subjected to plasma corona treatment, the parameters of the plasma corona treatment are as follows: plasma generator power 2 kW, treatment temperature 30-40 ℃, treatment time 40-60 s, to obtain a co-extrusion film.

[0065] The step of corona treatment is specifically as follows: after being bidirectionally stretched, slitting conical blades are arranged on both sides along the winding direction, the blade edge is attached to the cylinder film folding edge, and the cylinder film passing through the blades is cut into two pieces of film. The two pieces of film pass through the low-temperature corona treatment equipment stacked up and down at the same time, the plasma generating electrode of the corona treatment equipment at the upper part is located at the lower end, when the upper piece of film passes, the electrode is powered on to release ionized high-energy particles from bottom to top to bombard the lower surface of the upper piece of film for corona treatment; the plasma generating electrode of the corona treatment equipment at the lower part is located at the upper end, when the lower piece of film passes, the electrode is powered on to release ionized high-energy particles from top to bottom to bombard the upper surface of the lower piece of film for corona treatment. The plasma generating electrode is distributed in a planar manner, and the generated high-energy particles can cover all surfaces of the film.

[0066] Example 2

[0067] In one aspect, the application provides a high-breathability multilayer co-extrusion film, comprising an inner layer, an intermediate layer and an outer layer arranged in sequence, the inner layer is an ethylene-vinyl acetate copolymer layer, the intermediate layer is an ethylene-vinyl acetate copolymer layer, and the outer layer is a linear low-density polyethylene layer, the VA content in the inner layer is 28%, and the VA content in the intermediate layer is 12%. The thickness of the inner layer is 25 μm, the thickness of the intermediate layer is 55 μm, and the thickness of the outer layer is 25 μm.

[0068] In another aspect, the application provides a preparation process of a high-breathability multilayer co-extrusion film, comprising the following steps:

[0069] S1, extrusion: after the raw materials of the inner layer, the intermediate layer and the outer layer are put into a three-layer co-extrusion film blowing machine, extrusion is performed, the melt extrusion temperature of the inner layer is 120-130°C, the melt extrusion temperature of the intermediate layer is 130-140°C, and the melt extrusion temperature of the outer layer is 140-150°C, to obtain a rough blank;

[0070] S2, stretching: the rough blank is preheated by a preheating roller before stretching, the preheating temperature is 70-90°C, which is above the glass transition temperature of the material and below the melting temperature, then longitudinal stretching and transverse stretching are performed, the stretching ratio of the longitudinal stretching is 1.4, after the longitudinal stretching, the film passes through a constant-temperature oven at a uniform speed of 0.5 m / s for heat treatment, the heat treatment temperature is 80-100°C, the stretching ratio of the transverse stretching is 2.2, after the transverse stretching, the film passes through a constant-temperature oven at a uniform speed of 0.3 m / s for heat treatment, the heat treatment temperature is 90-100°C, then the film is cooled and shaped by a cooling roller, the cooling temperature is 25-35°C, to obtain a stretched film;

[0071] S3, corona treatment: the stretched film is cut into two films, and plasma corona treatment is performed, the parameters of the plasma corona treatment are as follows: plasma generator power 3 kW, treatment temperature 30-40℃, treatment time 40-60 s, to obtain a co-extruded film.

[0072] The step of corona treatment is as follows: after bidirectional stretching, a cutting conical blade is arranged on both sides along the winding direction, the blade edge is attached to the cylinder film folding edge, and the cylinder film passing through the blade is cut into two films. The two films pass through the low-temperature corona treatment equipment stacked above and below at the same time. The plasma generation electrode of the upper corona treatment equipment is located at the lower end. When the upper film passes, the electrode is powered on to release ionized high-energy particles from bottom to top, which bombard the lower surface of the upper film for corona treatment. The plasma generation electrode of the lower corona treatment equipment is located at the upper end. When the lower film passes, the electrode is powered on to release ionized high-energy particles from top to bottom, which bombard the upper surface of the lower film for corona treatment. The plasma generation electrode is distributed in a planar manner, and the generated high-energy particles can cover all surfaces of the film.

[0073] Example 3

[0074] In one aspect, the present application provides a high-breathability multilayer co-extruded film, which comprises an inner layer, an intermediate layer and an outer layer arranged in sequence, the inner layer is an ethylene-vinyl acetate copolymer layer, the intermediate layer is an ethylene-vinyl acetate copolymer layer, and the outer layer is a linear low-density polyethylene layer. The VA content in the inner layer is 30%, and the VA content in the intermediate layer is 15%. The thickness of the inner layer is 30 μm, the thickness of the intermediate layer is 45 μm, and the thickness of the outer layer is 30 μm.

[0075] In another aspect, the present application provides a preparation process of a high-breathability multilayer co-extruded film, which comprises the following steps:

[0076] S1, extrusion: the raw materials of the inner layer, the intermediate layer and the outer layer are put into a three-layer co-extrusion film blowing machine, and then extruded, the melt extrusion temperature of the inner layer is 120-130℃, the melt extrusion temperature of the intermediate layer is 130-140℃, and the melt extrusion temperature of the outer layer is 140-150℃, to obtain a rough blank;

[0077] S2, stretching: the rough blank is preheated by a preheating roller before stretching, the preheating temperature is 70-90℃, which is above the glass transition temperature of the material and below the melting temperature, then longitudinal stretching and transverse stretching are performed, the stretching ratio of the longitudinal stretching is 1.5, the stretched film passes through a constant temperature oven at a uniform speed of 0.5 m / s for heat treatment, the heat treatment temperature is 80-100℃, the stretching ratio of the transverse stretching is 2.5, the stretched film passes through a constant temperature oven at a uniform speed of 0.3 m / s for heat treatment, the heat treatment temperature is 90-100℃, then the film is cooled and shaped by a cooling roller, the cooling temperature is 25-35℃, to obtain a stretched film;

[0078] S3, corona treatment: the stretched film is cut into two films, and plasma corona treatment is performed, the parameters of the plasma corona treatment are as follows: plasma generator power 5 kW, treatment temperature 30-40℃, treatment time 40-60 s, to obtain a co-extruded film.

[0079] The step of corona treatment is as follows: after bidirectional stretching, a cutting conical blade is arranged on both sides along the winding direction, the blade edge is attached to the cylinder film folding edge, and the cylinder film passing through the blade is cut into two films. The two films pass through the upper and lower stacked low-temperature corona treatment equipment at the same time, the plasma generating electrode of the upper corona treatment equipment is located at the lower end, when the upper film passes, the electrode is powered on to release ionized high-energy particles from bottom to top, which bombard the lower surface of the upper film for corona treatment; the plasma generating electrode of the lower corona treatment equipment is located at the upper end, when the lower film passes, the electrode is powered on to release ionized high-energy particles from top to bottom, which bombard the upper surface of the lower film for corona treatment. The plasma generating electrode is distributed in a planar manner, and the generated high-energy particles can cover all surfaces of the film.

[0080] Example 4

[0081] The difference from Example 1 is that the outer layer raw material is prepared in Preparation Example 3.

[0082] Example 5

[0083] The difference from Example 1 is that the outer layer raw material is prepared in Preparation Example 4.

[0084] Example 6

[0085] The difference from Example 1 is that the outer layer raw material is prepared in Preparation Example 5.

[0086] Example 7

[0087] The difference from Example 1 is that the outer layer raw material is prepared in Preparation Example 6.

[0088] Example 8

[0089] The difference from Example 1 is that the outer layer raw material is prepared in Preparation Example 7.

[0090] Example 9

[0091] The difference from Example 1 is that the outer layer raw material is prepared in Preparation Example 8.

[0092] Example 10

[0093] The difference from Example 1 is that the outer layer raw material is selected from the outer layer raw material prepared in Preparation Example 7; after step S3, the co-extrusion film is subjected to irradiation crosslinking treatment, and the irradiation crosslinking treatment step is as follows: the co-extrusion film after winding is unwound, the outer layer is towards the irradiation warehouse, and is drawn to the electron beam accelerator irradiation warehouse, the irradiation dose is 70 KGy, the drawing rate is 3 m / s, and after repeating three times, it is wound.

[0094] Comparative Example

[0095] Comparative Example 1

[0096] The culture bag used in this comparative example is a TARKRA culture bag.

[0097] Performance detection test

[0098] Outer layer strength test: the tensile strength of the co-extrusion film is tested by using a universal testing machine (WDW-10C), longitudinal stretching, and the stretching rate is 2 mm·min -1 .

[0099] Table 1 Performance detection table

[0100]

[0101] Table 2 Performance detection table (continued)

[0102]

[0103] It can be found from the performance detection comparison of Tables 1-2 that:

[0104] 1. It can be found from the comparison of Examples 1-3 and Comparative Example 1 that the co-extrusion film prepared in Examples 1-3 has improved performance in various aspects, which shows that the composition of the inner layer, the intermediate layer and the outer layer is preferred in the present application. The prepared co-extrusion film has good barrier property to polar water vapor molecules during cell culture process, and has good permeability to non-polar oxygen and carbon dioxide molecules, good mechanical property and transparency, and is not easy to be scratched, and temperature difference is not formed between the inner and outer layers during subsequent processing, which is convenient for processing.

[0105] 2. It can be found from the comparison of Examples 4-6 and Example 1 that the tensile strength of the co-extrusion film prepared in Examples 4-6 is improved, which shows that the calcined oyster shell powder can fill LLDPE in the present application to improve the mechanical strength of LLDPE, thereby reducing the possibility of scratching the outer layer. When the outer layer contacts with water vapor, the calcined oyster shell powder can swell through hydration reaction, the irregular surface porous structure changes, and the barrier effect of the outer layer to water vapor can be improved, but the addition of the filler reduces the permeability of oxygen and carbon dioxide to some extent.

[0106] 3, it can be found by comparing example 7 and example 1 that the tensile strength of the co-extrusion film prepared in example 7 is improved, which shows that the calcined oyster shell powder is modified by coupling agent in the application, which effectively improves the dispersion effect of the calcined oyster shell powder in LLDPE, so that the calcined oyster shell powder can uniformly and fully fill LLDPE.

[0107] 4, it can be found by comparing example 8-9 and example 1 that the tensile strength of the co-extrusion film prepared in example 8-9 is improved, which shows that the orange peel powder can cooperate with the calcined oyster shell powder to fill LLDPE in the application, so as to further improve the mechanical strength of the outer layer. At the same time, the orange peel powder contains a large amount of flavonoids and functional groups such as hydroxyl and carbonyl groups, so the orange peel powder can form strong hydrogen bond with polyvinyl alcohol, further improving the mechanical strength of the outer layer and reducing the possibility of scratching the co-extrusion film.

[0108] 5, it can be found by comparing example 10 and example 1 that the tensile strength of the co-extrusion film prepared in example 10 is improved, which shows that the outer layer is modified by crosslinking in the application. After electron beam irradiation crosslinking, the outer layer is more likely to crosslink, so that the Ca ions in the calcined oyster shell powder are not easy to migrate, which can be combined with water vapor in the outer layer, so that the outer layer has better water vapor barrier effect. At the same time, the crystallinity of LLDPE after crosslinking is reduced, the transparency is improved compared with examples 8 and 9, and the oxygen and carbon dioxide permeation performance is also improved.

[0109] The specific embodiment is only an explanation of the application, which is not a limitation of the application. Those skilled in the art can make modifications to the embodiment without creative contribution according to the needs after reading the specification, but as long as it is within the scope of the claims of the application, it is protected by the patent law.

Claims

1. A high gas permeable multilayer co-extruded film, characterized in that, The outer layer comprises the following raw materials by weight: 100 parts of LLDPE; 3-5 parts of polyvinyl alcohol; and 5-10 parts of calcined oyster shell powder; the calcined oyster shell powder is modified oyster shell powder modified by a coupling agent; and the outer layer further comprises 1-2 parts by weight of orange peel powder. The outer layer is subjected to electron beam irradiation crosslinking treatment; the irradiation crosslinking treatment is performed in an electron beam accelerator irradiation cabin at an irradiation dose of 60-80 KGy and a pulling rate of 2-5 m / s. The total thickness of the co-extruded film is 90-110 microns, and the light transmittance of the co-extruded film is > 90%.

2. The high permeability multilayer co-extruded film according to claim 1, characterized in that: The thickness of the inner layer is 20-30 microns, the thickness of the intermediate layer is 40-50 microns, and the thickness of the outer layer is 20-30 microns.

3. The high permeability multilayer co-extruded film according to claim 1, characterized in that: The method comprises the following steps:

4. A process for the preparation of a high permeability multilayer co-extruded film according to any one of claims 1 to 3, characterized in that, S1, extrusion: the raw materials of the inner layer, the intermediate layer and the outer layer are put into a three-layer co-extrusion film blowing machine, and then extruded to obtain a rough blank; S2, stretching: the rough blank is subjected to longitudinal stretching and transverse stretching; the stretching ratio of the longitudinal stretching is 1.2-1.5, and the stretching ratio of the transverse stretching is 1.8-2.5, to obtain a stretched film; S3, corona treatment: the stretched film is cut into two films, and is subjected to plasma corona treatment to obtain a co-extruded film. The parameters of the plasma corona treatment in step S3 are as follows: power 2kW-5kW, treatment temperature 30-40℃, and treatment time 40-60s.

5. The process for preparing a high permeability multilayer co-extruded film according to claim 4, characterized in that: ​

Images