Composite packaging film and method for producing the same

Abstract

The application provides a composite film packaging film, which comprises an inner layer, an intermediate layer and an outer layer, the inner layer comprises polyethylene; the intermediate layer comprises ethylene-vinyl alcohol copolymer, and the intermediate layer is at least partially covered on the inner layer; the outer layer comprises polyethylene, cellulose and hemicellulose, and the outer layer is at least partially covered on the intermediate layer; wherein the inner layer and the intermediate layer and the intermediate layer and the outer layer are combined through an adhesive; and the intermediate layer is provided with at least one layer. The composite film material of the application shows superior performance in barrier property, moisture resistance, mechanical strength and environmental protection performance through the design of the multi-layer structure, and is suitable for the packaging of oxygen-sensitive products, can provide good physical protection, and meets the environmental protection requirements.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of packaging materials, and in particular, relates to a composite packaging film and a preparation method thereof. BACKGROUND

[0002] Composite film materials are widely used due to their excellent barrier properties and mechanical properties. The barrier properties of the composite film materials are usually determined by the OTR (oxygen transmission rate) index. The lower the OTR value, the better the barrier property. The OTR of the high-barrier composite film materials on the market is usually below 10. The demand is usually met by increasing EVOH or PVDC materials. Although the demand for some high-barrier requirements can be met by increasing such materials through one-time film blowing, it is difficult for such materials to meet the requirements of some composite film materials with a barrier property of 0.5 or below. SUMMARY

[0003] The present application aims to solve at least one of the above technical problems.

[0004] To this end, the first object of the present application is to provide a composite packaging film.

[0005] The second object of the present application is to provide a preparation method of the composite packaging film.

[0006] To achieve the first object of the present application, the present application provides a composite film material, which comprises an inner layer, an intermediate layer and an outer layer. The inner layer comprises polyethylene. The intermediate layer comprises ethylene-vinyl alcohol copolymer, and the intermediate layer is at least partially covered on the inner layer. The outer layer comprises polyethylene, cellulose and hemicellulose, and the outer layer is at least partially covered on the intermediate layer. The inner layer and the intermediate layer, and the intermediate layer and the outer layer are combined by an adhesive. The intermediate layer is provided with at least one layer.

[0007] Compared with the prior art, the technical effects achieved by adopting the technical scheme are as follows: the composite film material of the application comprises an inner layer, an intermediate layer and an outer layer, the polyethylene of the inner layer ensures that the composite film material does not react chemically when in contact with the contents, while providing good sealing performance to prevent the penetration of moisture or gas; the ethylene-vinyl alcohol copolymer as the intermediate layer material mainly provides high-efficiency barrier property, especially for oxygen, carbon dioxide and other gases, which is very crucial for prolonging the shelf life of food or other products; the combination of the outer layer material includes polyethylene, cellulose and hemicellulose, which provides wear resistance, physical strength and certain biodegradability, the polyethylene provides the waterproof performance of the outer layer, and the cellulose and hemicellulose can form a dense structure, which not only blocks the entry of gas, but also enhances the mechanical strength and environmental protection of the film; the adhesive is used to composite the layers together, so that the composite film can maintain its interlayer bonding strength for a long time while maintaining flexibility, thereby ensuring that the film material has stable structure and performance during use; the composite film material of the application has superior performance in barrier property, moisture resistance, mechanical strength and environmental protection performance through the design of the multi-layer structure, which is not only suitable for the packaging of oxygen-sensitive products, but also provides good physical protection while meeting the environmental protection requirements.

[0008] In addition, the technical scheme provided by the application can also have the following technical features:

[0009] In the above technical features, the outer layer comprises a plastic layer and a fiber layer, the plastic layer comprises polyethylene, and the plastic layer at least partially covers the intermediate layer; the fiber layer comprises cellulose and hemicellulose, and the fiber layer at least partially covers the plastic layer; wherein the cellulose is nanometer original cellulose; the thickness of the fiber layer accounts for 10%-25% of the thickness of the entire outer layer.

[0010] Compared with the prior art, the technical effects achieved by adopting the technical scheme are as follows: the polyethylene in the plastic layer continues to provide its basic waterproofness, sealing property and physical resistance, the polyethylene covers the intermediate layer, thereby protecting the intermediate layer and enhancing the integrity of the overall structure; nanometer original cellulose is used, which has better barrier property and cooperates with hemicellulose to further enhance oxygen barrier property; the thickness of the fiber layer accounts for 10%-25% of the thickness of the entire outer layer, thereby ensuring the balance between mechanical performance and flexibility of the outer layer, and the moderate thickness of the fiber layer can effectively improve the physical performance of the film without making the film too rigid or losing elasticity.

[0011] In any of the above technical features, the thickness of the inner layer is 5-20 microns; and / or the thickness of the intermediate layer is 10-20 microns; and / or the thickness of the outer layer is 15-30 microns.

[0012] Compared with the prior art, the technical effects achieved by the technical scheme are as follows: the thickness range of the inner layer determines the basic moisture resistance, flexibility and sealing performance of the composite film, a thicker inner layer can improve the moisture resistance and durability of the film, and a thinner inner layer can help to maintain the softness of the material and reduce the cost, the use of the above-mentioned thickness of the inner layer can accurately control the moisture resistance of the composite film and ensure that the moisture-sensitive contents are fully protected; the thickness of the middle layer directly affects the barrier performance of the composite film, especially the barrier effect of oxygen and other gases, a thicker middle layer usually provides higher barrier performance, but it may also increase the weight and cost of the material, the use of the above-mentioned thickness of the middle layer enables the middle layer to provide sufficient barrier performance without adversely affecting the overall flexibility of the film, and the comprehensive performance of the material is maintained; the thickness of the outer layer affects the physical resistance, wear resistance and environmental protection of the film, the use of the above-mentioned thickness of the outer layer can improve the tear resistance and wear resistance of the composite film and ensure that it has sufficient physical protection capability during transportation and storage; reasonable thickness of each layer can also enhance the overall performance balance of the composite film, ensuring that it provides excellent functions while maintaining good flexibility, lightweight and environmental protection.

[0013] In any of the above technical features, the oxygen transmission rate of the composite film material is less than 0.5 cm 3 / (m 2 ×24h×0.1MPa); and / or the water vapor transmission rate of the composite film material is less than 0.2 g / m 2 ×24h.

[0014] Compared with the prior art, the technical effects achieved by the technical scheme are as follows: the low oxygen transmission rate ensures that the products in the package are not affected by oxidation, greatly prolonging the shelf life of easily oxidizable substances and maintaining the freshness and quality of the products; the low water vapor transmission rate means that the composite film material can effectively prevent external water vapor from entering the package and protect the contents from a humid environment, which is crucial for maintaining the quality of dry products such as dry food, electronic components, etc.; by strictly controlling the oxygen transmission rate and water vapor transmission rate of the composite film material, its barrier performance can be significantly improved, making it suitable for packaging products sensitive to gas and moisture.

[0015] To achieve the second object of the present application, the present application provides a preparation method of a composite film material for preparing the composite film material of any one of the above technical features, the preparation method comprising:

[0016] S100, respectively preparing plastic layers, middle layers, inner layers and fiber solutions;

[0017] S200, sequentially compounding from top to bottom in the order of plastic layer, middle layer and inner layer, and obtaining a first intermediate body through film blowing treatment;

[0018] S300, coating a fiber solution on the plastic layer of the first intermediate body, and obtaining a composite film material through annealing treatment;

[0019] The adhesive layers are arranged between the inner layer and the intermediate layer and between the intermediate layer and the outer layer.

[0020] Compared with the prior art, the technical effects achieved by the technical scheme are as follows: the materials of the layers are prepared respectively, the formula of each layer can be adjusted independently to meet the performance requirements of the final composite film, the prepared fiber solution can ensure that the nanocellulose and hemicellulose are uniformly distributed during the coating process and play their roles, the plastic layer, the intermediate layer and the outer layer are combined together to form the first intermediate body with a basic structure through layer-by-layer compounding and film blowing treatment, the film blowing treatment can enhance the compactness and uniformity of the material and ensure the close combination between the layers, after the fiber solution is coated, the nanocellulose and hemicellulose form a uniform fiber layer on the surface of the plastic layer through annealing treatment, which helps to solidify and stabilize the fiber layer, the adhesive layers are arranged between the inner layer and the intermediate layer and between the intermediate layer and the outer layer to ensure the firm combination between the layers and prevent separation or peeling between the layers, and the preparation method ensures the performance indicators of the composite film material, including high strength, excellent gas and moisture barrier properties, and good environmental protection properties, through precise process control and material treatment.

[0021] In any of the technical features above, S300 comprises:

[0022] S301, coating a cross-linking agent on the plastic layer of the first intermediate body, then coating a fiber solution, and obtaining a second intermediate body through first annealing treatment;

[0023] S302, performing second annealing treatment on the second intermediate body to obtain a composite film material.

[0024] Compared with the prior art, the technical effects achieved by the technical scheme are as follows: coating the cross-linking agent on the surface of the plastic layer can promote the chemical bonding between the nanocellulose and hemicellulose in the fiber solution and between them and the plastic layer, the first annealing treatment further promotes the completion of these chemical reactions and solidifies to form a more stable structure, the purpose of the second annealing treatment is to further strengthen and stabilize the structure of the composite film, so that the combination between the layers is more firm, and the overall performance of the material is improved; through the use of the cross-linking agent and the double annealing treatment, strong chemical bonding is formed between the fiber layer and the plastic layer of the composite film, which significantly enhances the interlayer bonding force, so that the film material is not easy to delaminate or break when subjected to mechanical stress.

[0025] In any of the technical features above, the temperature of the first annealing treatment is 60-80℃; and / or the temperature of the second annealing treatment is 50-70℃; and / or the cooling rate of the first annealing treatment is 0.8-1.2℃ / min; and / or the cooling rate of the second annealing treatment is 1-1.5℃ / min.

[0026] Compared with the prior art, the technical effects achieved by adopting the technical solution are as follows: the temperature of the first annealing treatment determines the efficiency and degree of cross-linking reaction, and the use of the above temperature range can promote the chemical reaction between the cross-linking agent and the components in the fiber solution, so that a stable bond is formed between the fiber layer and the plastic layer; the use of the above cooling rate for the first annealing treatment can control the crystallinity of nanocellulose and hemicellulose on the surface of the plastic layer, thereby improving the mechanical strength and wear resistance of the composite film; the temperature of the second annealing treatment further affects the final structure and physical properties of the composite film, and the use of the above temperature range can eliminate residual stress and stabilize the material structure, but it cannot be too high to avoid thermal damage to the material; the use of the above cooling rate for the second annealing treatment can further optimize the physical properties of the material, ensuring its reliability in actual application.

[0027] In any of the technical features above, the time of the first annealing treatment is 0.5-1h; and / or the time of the second annealing treatment is 0.5-1h.

[0028] Compared with the prior art, the technical effects achieved by adopting the technical solution are as follows: the time of the first annealing treatment affects the degree of reaction between the cross-linking agent and the fiber solution and the plastic layer, and the use of the above time makes nanocellulose and hemicellulose form a stable cross-linking network on the surface of the plastic layer, so that the internal structure of the material is improved, internal defects and unevenness are reduced, and the composite film has higher quality and consistency; the second annealing treatment is mainly used to further stabilize the material structure, reduce internal residual stress, and improve the long-term use performance of the material; by precisely controlling the time of the first annealing treatment and the second annealing treatment, the material can maintain good physical properties and dimensional stability during long-term use, and its durability and anti-aging ability are enhanced.

[0029] In any of the technical features above, in S200, the film blowing treatment further includes a pre-heating treatment; the pre-heating treatment is an infrared pre-heating treatment.

[0030] Compared with existing technologies, the technical effects achieved by this solution are as follows: Infrared preheating enables materials to soften uniformly when heated, thereby improving their fluidity and allowing them to spread more evenly during the blown film process, forming a dense and uniform film structure; through preheating, the layers of materials can better penetrate and bond with each other during the blown film process, enhancing the interlayer adhesion of the composite film and reducing the generation of delamination or bubbles; infrared preheating also helps to reduce stress concentration in the material during the blown film process, reducing quality defects caused by temperature differences, while improving production efficiency and reducing the defect rate.

[0031] In any of the above technical features, the preheating temperature is 50℃-55℃.

[0032] Compared with existing technologies, the technical effects achieved by this solution are as follows: controlling the preheating temperature within a suitable range allows for optimal molecular chain mobility of the material, improving material flowability and ensuring uniform distribution and thickness consistency of the film during the blown film process. Excessive temperature may lead to thermal degradation or over-softening of the material, while excessively low temperature may cause material cracking or surface unevenness during the blown film process. The aforementioned preheating temperature helps the materials of each layer to fuse better during the blown film process, enhances interlayer adhesion, and reduces the generation of delamination, bubbles, or other defects.

[0033] The technical effects that can be achieved by adopting the technical solution of the present invention are as follows:

[0034] 1. The composite membrane material of the present invention exhibits superior performance in terms of barrier properties, moisture resistance, mechanical strength, and environmental protection through its multi-layer structure design. It is not only suitable for packaging products that are sensitive to oxygen, but also provides good physical protection while taking into account environmental protection requirements.

[0035] 2. A fiber layer is provided outside the outer plastic layer. The fiber layer includes cellulose and hemicellulose. The cellulose is nano-protocellulose, which has better barrier properties. Together with hemicellulose, it can further enhance oxygen barrier properties.

[0036] 3. The preparation method of the composite membrane material of the present invention ensures the various performance indicators of the composite membrane material through precise process control and material treatment, including high strength, excellent gas and moisture barrier properties, and good environmental protection characteristics. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings to be used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 A schematic view of a composite film material according to an embodiment of the present application;

[0039] Figure 2 A schematic view of a composite film material according to an embodiment of the present application; Figure 1 A partial enlarged view of A in FIG. 1;

[0040] Legend: 100 - inner layer, 200 - intermediate layer, 300 - outer layer, 310 - fiber layer, 320 - plastic layer. DETAILED DESCRIPTION

[0041] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the following will further describe the present application in combination with the drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments.

[0043] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the following will describe the specific embodiments of the present application in combination with Figure 1 The specific embodiments of the present application will be described in detail.

[0044] In the related art, high-barrier composite film materials are usually obtained by adding EVOH or PVDC materials to meet the requirements, and the OTR is usually below 10. Although only one film blowing is needed to meet some high-barrier requirements by adding such materials, it is difficult to meet the composite film material with higher barrier requirements below 0.5.

[0045] Therefore, the present application provides a composite packaging film and a preparation method thereof, which further improves the barrier property by coating a fiber coating layer on the surface of the outer layer.

[0046] Specifically, the embodiments of the present application provide a composite film material, which comprises an inner layer 100, an intermediate layer 200 and an outer layer 300. The inner layer 100 comprises polyethylene; the intermediate layer 200 comprises ethylene-vinyl alcohol copolymer, and the intermediate layer 200 is at least partially covered on the inner layer 100; the outer layer 300 comprises polyethylene, cellulose and hemicellulose, and the outer layer 300 is at least partially covered on the intermediate layer 200; wherein the inner layer 100 and the intermediate layer 200, and the intermediate layer 200 and the outer layer 300 are combined by an adhesive; and the intermediate layer 200 is provided with at least one layer.

[0047] Preferably, the composite film material of the embodiments of the present application comprises an inner layer 100, a middle layer 200 and an outer layer 300, the polyethylene of the inner layer 100 ensures that the composite film material does not chemically react when in contact with the contents, while providing good sealing performance to prevent the penetration of moisture or gas; the ethylene-vinyl alcohol copolymer as the middle layer 200 material mainly serves to provide high-efficiency barrier properties, especially for oxygen, carbon dioxide and other gases, which is crucial for extending the shelf life of food or other products, the ethylene-vinyl alcohol copolymer middle layer 200 greatly enhances the barrier properties of the composite film, preventing external oxygen and other gases from entering the packaging interior; the combination of the outer layer 300 material includes polyethylene, cellulose and hemicellulose, providing wear resistance, physical strength and certain biodegradability, the polyethylene provides the water resistance of the outer layer 300, and the cellulose and hemicellulose can form a dense structure, which not only prevents the entry of gas and the like, but also enhances the mechanical strength and environmental friendliness of the film; the layers are combined together by an adhesive, the composite film can maintain its interlayer bonding strength for a long time while maintaining flexibility, ensuring that the film material has stable structure and performance during use.

[0048] Further, the outer layer 300 comprises a plastic layer 320 and a fiber layer 310, the plastic layer 320 comprises polyethylene, and the plastic layer 320 at least partially covers the middle layer 200; the fiber layer 310 comprises cellulose and hemicellulose, and the fiber layer 310 at least partially covers the plastic layer 320; wherein the cellulose is nanometer primary cellulose; the thickness of the fiber layer 310 accounts for 10%-25% of the thickness of the entire outer layer 300.

[0049] Preferably, the polyethylene in the plastic layer 320 continues to provide its basic water resistance, sealing performance and physical resistance, the polyethylene covers the middle layer 200, playing a role in protecting the middle layer 200 and enhancing the overall structural integrity; nanometer primary cellulose is used, which has better barrier properties, and cooperates with hemicellulose to further enhance oxygen barrier properties, and hemicellulose has stronger fluidity, which can further fill the pores that may exist in the nanometer cellulose structure, further enhancing the barrier properties; the thickness of the fiber layer 310 accounts for 10%-25% of the thickness of the entire outer layer 300, ensuring the balance between the mechanical properties and flexibility of the outer layer 300, and the moderate thickness of the fiber layer 310 can effectively improve the physical properties of the film without making the film too stiff or losing elasticity.

[0050] Preferably, reasonable thickness of each layer can also enhance the overall performance balance of the composite film, ensuring that it provides excellent functions while maintaining good flexibility, lightweight and environmental protection; the thickness range of the inner layer 100 determines the basic moisture resistance, flexibility and sealing of the composite film, a thicker inner layer 100 can improve the moisture resistance and durability of the film, while a thinner inner layer 100 helps to maintain the softness of the material and reduce costs, the thickness of the inner layer 100 is 5-20 microns, which can accurately control the moisture resistance of the composite film and ensure that the moisture-sensitive contents are fully protected.

[0051] Preferably, the thickness of the intermediate layer 200 directly affects the barrier performance of the composite film, especially the barrier effect of oxygen and other gases, a thicker intermediate layer 200 will generally provide higher barrier properties, but it may also increase the weight and cost of the material, the thickness of the intermediate layer 200 is 10-20 microns, so that the intermediate layer 200 can provide sufficient barrier performance without adversely affecting the overall flexibility of the film, maintaining the overall performance of the material.

[0052] Preferably, the thickness of the outer layer 300 affects the physical resistance, wear resistance and environmental protection of the film, and the thickness of the outer layer 300 is 15-30 microns, which can improve the tear resistance and wear resistance of the composite film, ensuring that it has sufficient physical protection during transportation and storage.

[0053] Preferably, by strictly controlling the oxygen transmission rate and water vapor transmission rate of the composite film material, its barrier performance can be significantly improved, making it suitable for packaging products sensitive to gas and moisture; the oxygen transmission rate of the composite film material is less than 0.5 cm 3 / (m 2 ×24h×0.1MPa), low oxygen transmission rate ensures that the products inside the package will not be affected by oxidation, greatly extending the shelf life of easily oxidized substances and maintaining the freshness and quality of the products.

[0054] Further, the water vapor transmission rate of the composite film material is less than 0.2 g / m 2 ×24h, low water vapor transmission rate means that the composite film material can effectively prevent external water vapor from entering the package, protecting the contents from a humid environment, which is crucial for maintaining the quality of dry products such as dry food, electronic components, etc.

[0055] In some embodiments of the present application, the preparation method of the composite film material comprises:

[0056] S100, respectively preparing plastic layers, intermediate layers, outer layers and fiber solutions;

[0057] S200, sequentially composite from top to bottom according to the order of plastic layer, intermediate layer and outer layer, and obtain a first intermediate body after blown film treatment;

[0058] S300, coating the fiber solution on the plastic layer of the first intermediate body, and performing annealing treatment to obtain the composite film material;

[0059] The adhesive layer is arranged between the inner layer and the intermediate layer and between the intermediate layer and the outer layer.

[0060] Preferably, each layer material is prepared respectively, and the formula of each layer can be adjusted independently to meet the performance requirements of the final composite film. The prepared fiber solution can ensure uniform distribution of nanocellulose and hemicellulose during the coating process, and the nanocellulose and hemicellulose can play their roles. Through layer-by-layer compounding and film blowing, the plastic layer, the intermediate layer and the outer layer are combined together to form a first intermediate body with a basic structure. The film blowing process can enhance the compactness and uniformity of the material and ensure the close combination between the layers. After coating the fiber solution, the nanocellulose and hemicellulose form a uniform fiber layer on the surface of the plastic layer through annealing treatment. The annealing treatment helps to solidify and stabilize the fiber layer. The fibers can form a dense structure during the drying process, and a high level of hydrogen bonds is formed in the structure. The adhesive layer is arranged between the inner layer and the intermediate layer and between the intermediate layer and the outer layer. The adhesive layer is preferably an adhesive resin adhesive layer, which ensures the firm combination between the layers and prevents separation or peeling between the layers. The preparation method ensures the performance indicators of the composite film material, including high strength, excellent gas and moisture barrier properties, and good environmental characteristics, through precise process control and material processing.

[0061] Further, the preparation method of nanocellulose comprises:

[0062] S101, after the cellulose is pretreated by oxidation using TEMPO (2, 2, 6, 6-tetramethylpiperidine-1-oxyl), the cellulose is subjected to homogenization treatment and ultrasonic treatment in sequence to obtain nanocellulose.

[0063] Preferably, the solvent of the fiber solution is a deep eutectic solvent (DESs). DESs are similar to ionic liquids, but have lower cost and are more environmentally friendly. DESs are preferably a mixture of a hydrogen bond acceptor and a hydrogen bond donor. For example, the hydrogen bond acceptor includes choline chloride and betaine, and the hydrogen bond donor includes lactic acid, malic acid and oxalic acid. The dissolution temperature is preferably 60-120℃. Ultrasonic stirring or microwave heating is preferably used during dissolution to improve the dissolution efficiency.

[0064] Preferably, the hemicellulose is extracted by alkali extraction. NaOH with an alkalinity of 3%-5% is preferably added to the raw material to adjust the pH to 2-5, so that the hemicellulose is precipitated. After centrifugal separation, the mixture of anhydrous ethanol and acetone is used to wash to neutral, and the hemicellulose is obtained.

[0065] Preferably, S300 comprises:

[0066] S301, after coating the cross-linking agent on the plastic layer of the first intermediate, coating the fiber solution, and after the first annealing treatment, obtaining the second intermediate;

[0067] S302, the second annealing treatment is performed on the second intermediate to obtain the composite film material.

[0068] Preferably, coating the cross-linking agent on the surface of the plastic layer can promote the chemical bonding between nanocellulose and hemicellulose in the fiber solution and between them and the plastic layer, and the first annealing treatment further promotes the completion of these chemical reactions and solidification to form a more stable structure. The purpose of the second annealing treatment is to further strengthen and stabilize the structure of the composite film, so that the bonding between the layers is more firm, and the overall performance of the material is improved. Through the use of cross-linking agent and double annealing treatment, strong chemical bonding is formed between the fiber layer and the plastic layer of the composite film, which significantly enhances the interlayer bonding force, so that the film material is not easy to delaminate or break when subjected to mechanical stress.

[0069] Preferably, the temperature of the first annealing treatment determines the efficiency and degree of cross-linking reaction, the temperature of the first annealing treatment is 60-80℃, which can promote the chemical reaction between the cross-linking agent and the components in the fiber solution, so that the fiber layer and the plastic layer form a stable combination, the cooling rate of the first annealing treatment is 0.8-1.2℃ / min, which can control the crystallinity of nanocellulose and hemicellulose on the surface of the plastic layer, thereby improving the mechanical strength and wear resistance of the composite film.

[0070] Further, the temperature of the second annealing treatment further affects the final structure and physical properties of the composite film, the temperature of the second annealing treatment is 50-70℃, which can eliminate residual stress and stabilize the material structure, but cannot be too high to cause thermal damage to the material, the cooling rate of the second annealing treatment is 1-1.5℃ / min, which can further optimize the physical properties of the material to ensure its reliability in actual application.

[0071] Preferably, the time of the first annealing treatment affects the degree of reaction of the cross-linking agent between the fiber solution and the plastic layer, the time of the first annealing treatment is 0.5h-1h, so that the nanocellulose and hemicellulose form a stable cross-linked network on the surface of the plastic layer, the internal structure of the material is perfected, the internal defects and unevenness are reduced, and the quality and consistency of the composite film are ensured; the time of the second annealing treatment is 0.5h-1h, which can further stabilize the material structure, reduce the internal residual stress, and improve the long-term use performance of the material; by accurately controlling the time of the first annealing treatment and the second annealing treatment, the material can maintain good physical properties and dimensional stability during long-term use, and its durability and anti-aging ability are enhanced.

[0072] Preferably, before the film blowing treatment in S200, a pre-heating treatment is further included; the pre-heating treatment is an infrared pre-heating treatment.

[0073] Preferably, the infrared pre-heating can make the material uniformly soften when heated, thereby improving its flowability, so that the material can be more uniformly expanded during the film blowing process, forming a dense and uniform film layer structure; through the pre-heating treatment, the materials in each layer can better penetrate and bond with each other during the film blowing process, enhancing the interlayer adhesion of the composite film and reducing the generation of delamination or bubbles; the infrared pre-heating also helps to reduce stress concentration of the material during the film blowing process, reduce quality defects caused by temperature difference, and at the same time improve production efficiency and reduce the rate of defective products.

[0074] Further, the temperature of the pre-heating treatment is 50℃-55℃, which can make the molecular chain activity of the material reach the best, improve the flowability of the material, and ensure the uniform distribution and thickness consistency of the film material during the film blowing process; too high temperature may cause thermal degradation or excessive softening of the material, and too low temperature may cause the material to break or the surface to be uneven during the film blowing process; using the above pre-heating temperature helps the materials in each layer to better fuse during the film blowing process, enhances the interlayer adhesion, and reduces the generation of delamination, bubbles or other defects.

[0075]

Embodiment 1

[0076] The embodiment provides a composite film material, which comprises, from bottom to top, an inner layer, an intermediate layer and an outer layer, the inner layer comprises polyethylene, the intermediate layer comprises ethylene-vinyl alcohol copolymer, and the outer layer comprises a polyethylene plastic layer and a fiber layer, the thickness of the inner layer is 5μm, the thickness of the intermediate layer is 20μm, the thickness of the outer layer is 20μm, and the thickness of the fiber layer accounts for 10% of the thickness of the entire outer layer, and the preparation method of the composite film material comprises:

[0077] S100, respectively preparing a plastic layer, an intermediate layer, an inner layer and a fiber solution;

[0078] S200, sequentially composite from top to bottom in the order of plastic layer, middle layer and outer layer, and obtain a first intermediate body after infrared preheating and film blowing treatment;

[0079] S300, coat the fiber solution on the plastic layer of the first intermediate body, and obtain a composite film material after annealing treatment;

[0080] S300, coat the fiber solution on the plastic layer of the first intermediate body, and obtain a composite film material after annealing treatment;

[0081] S301, coat the crosslinking agent on the plastic layer of the first intermediate body, then coat the fiber solution, and perform first annealing treatment at 80°C, with a cooling rate of 0.8°C / min to obtain a second intermediate body;

[0082] S302, perform second annealing treatment on the second intermediate body at 70°C, with a cooling rate of 1.5°C / min to obtain a composite film material;

[0083] The adhesive resin adhesive layers are arranged between the inner layer and the middle layer and between the middle layer and the outer layer; the fiber solution is a mixed solution of nanocellulose and hemicellulose, and the nanocellulose is obtained from a supplier.

[0084]

Embodiment 2

[0085] The embodiment provides a composite film material which comprises, from bottom to top, an inner layer, a middle layer and an outer layer, the inner layer comprises polyethylene, the middle layer comprises ethylene-vinyl alcohol copolymer, and the outer layer comprises a polyethylene plastic layer and a fiber layer, the thickness of the inner layer is 10μm, the thickness of the middle layer is 15μm, the thickness of the outer layer is 30μm, the thickness of the fiber layer accounts for 25% of the thickness of the entire outer layer, and the preparation method of the composite film material comprises the following steps:

[0086] S100, respectively prepare a plastic layer, a middle layer, an inner layer and a fiber solution;

[0087] S200, sequentially composite from top to bottom in the order of plastic layer, middle layer and inner layer, and obtain a first intermediate body after infrared preheating at 52°C and film blowing treatment;

[0088] S300, coat the fiber solution on the plastic layer of the first intermediate body, and obtain a composite film material after annealing treatment;

[0089] S300, coat the fiber solution on the plastic layer of the first intermediate body, and obtain a composite film material after annealing treatment;

[0090] S301, coat the crosslinking agent on the plastic layer of the first intermediate body, then coat the fiber solution, and perform first annealing treatment at 75°C, with a cooling rate of 1.0°C / min to obtain a second intermediate body;

[0091] S302, performing second annealing treatment on the second intermediate at 50 DEG C, a cooling rate of the second annealing treatment being 1.0 DEG C / min, to obtain the composite film material;

[0092] The inner layer, the intermediate layer and the outer layer are sequentially arranged from bottom to top, the inner layer comprises polyethylene, the intermediate layer comprises ethylene-vinyl alcohol copolymer, the intermediate layer is provided with two layers, the outer layer comprises a polyethylene plastic layer and a fiber layer, the thickness of the inner layer is 10 microns, the thickness of the intermediate layer is 20 microns, the thickness of the outer layer is 20 microns, the thickness of the fiber layer accounts for 20% of the thickness of the entire outer layer, and the preparation method of the composite film material comprises the following steps:

[0093] Embodiment 3

[0094] The embodiment provides a composite film material, which comprises an inner layer, an intermediate layer and an outer layer from bottom to top, the inner layer comprises polyethylene, the intermediate layer comprises ethylene-vinyl alcohol copolymer, the intermediate layer is provided with two layers, the outer layer comprises a polyethylene plastic layer and a fiber layer, the thickness of the inner layer is 10 microns, the thickness of the intermediate layer is 20 microns, the thickness of the outer layer is 20 microns, the thickness of the fiber layer accounts for 20% of the thickness of the entire outer layer, and the preparation method of the composite film material comprises the following steps:

[0095] S100, respectively preparing a plastic layer, an intermediate layer, an inner layer and a fiber solution;

[0096] S200, sequentially compounding the plastic layer, the intermediate layer and the inner layer from top to bottom, and performing infrared preheating at 55 DEG C, to obtain a first intermediate after film blowing treatment;

[0097] S300, coating the fiber solution on the plastic layer of the first intermediate, and performing annealing treatment, to obtain the composite film material;

[0098] S300 comprises the following steps:

[0099] S301, coating a crosslinking agent on the plastic layer of the first intermediate, then coating the fiber solution, and performing first annealing treatment at 60 DEG C, a cooling rate of the first annealing treatment being 1.2 DEG C / min, to obtain a second intermediate;

[0100] S302, performing second annealing treatment on the second intermediate at 50 DEG C, a cooling rate of the second annealing treatment being 1.5 DEG C / min, to obtain the composite film material;

[0101] The inner layer, the intermediate layer and the outer layer are sequentially arranged from bottom to top, the inner layer comprises polyethylene, the intermediate layer comprises ethylene-vinyl alcohol copolymer, the intermediate layer is provided with two layers, the outer layer comprises a polyethylene plastic layer and a fiber layer, the thickness of the inner layer is 10 microns, the thickness of the intermediate layer is 20 microns, the thickness of the outer layer is 20 microns, the thickness of the fiber layer accounts for 20% of the thickness of the entire outer layer, and the preparation method of the composite film material comprises the following steps:

[0102] S101, performing oxidation pretreatment on cellulose by using TEMPO, and then performing homogenization treatment and ultrasonic treatment in sequence, to obtain nanometer primary cellulose.

[0103] Embodiment 4

[0104] The embodiment provides a composite film material, which comprises, from bottom to top, an inner layer, an intermediate layer and an outer layer, the inner layer comprises polyethylene, the intermediate layer comprises ethylene-vinyl alcohol copolymer, the intermediate layer is provided with two layers, the outer layer comprises a polyethylene plastic layer and a fiber layer, the thickness of the inner layer is 5 microns, the thickness of the intermediate layer is 15 microns, the thickness of the outer layer is 30 microns, the thickness of the fiber layer accounts for 18% of the thickness of the entire outer layer, and the preparation method of the composite film material comprises the following steps:

[0105] S100, respectively preparing a plastic layer, an intermediate layer, an inner layer and a fiber solution;

[0106] S200, sequentially compounding the plastic layer, the intermediate layer and the inner layer from top to bottom, and after infrared preheating at 50 DEG C, performing a film blowing treatment to obtain a first intermediate body;

[0107] S300, coating the fiber solution on the plastic layer of the first intermediate body, and performing annealing treatment to obtain the composite film material;

[0108] S300 comprises the following steps:

[0109] S301, coating a crosslinking agent on the plastic layer of the first intermediate body, then coating the fiber solution, and performing first annealing treatment at 60 DEG C, wherein the cooling rate of the first annealing treatment is 0.8 DEG C / min to obtain a second intermediate body;

[0110] S302, performing second annealing treatment on the second intermediate body at 50 DEG C, wherein the cooling rate of the second annealing treatment is 1 DEG C / min to obtain the composite film material;

[0111] The inner layer and the intermediate layer, and the intermediate layer and the outer layer are provided with an adhesive resin adhesive layer; the fiber solution is a mixed solution of nanometer original cellulose and hemicellulose, and the nanometer original cellulose is obtained by outsourcing.

[0112] The preparation method of the nanometer original cellulose comprises the following steps:

[0113] S101, performing oxidation pretreatment on the cellulose by using TEMPO, and then performing homogenization treatment and ultrasonic treatment in sequence to obtain the nanometer original cellulose.

[0114]

Performance test

[0115] Barrier property test

[0116] Under the condition of 25 DEG C and 0% RH, oxygen transmission rate test and water vapor transmission rate test are performed on the composite film materials of examples 1-4, and the test results are shown in Table 1.

[0117] Table 1

[0118] Abrasion resistance test

[0119] The composite film materials of Examples 1-4 were subjected to abrasion resistance tests according to ASTM F3300-2018, and the test results were all qualified.

[0120] Tear strength test

[0121] The composite film materials of Examples 1-4 were subjected to tear strength tests according to GB / T 529-2008, and the test results are shown in Table 2.

[0122] Table 2

[0123] From the above results, it can be seen that the composite film materials of the examples have good barrier properties, abrasion resistance and high tear strength, especially the composite film materials in Examples 3 and 4, which may be due to the special preparation process of nanocellulose and the double-layer intermediate layer used in Examples 3 and 4.

[0124] The above description is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can make equivalent replacements or changes within the technical range disclosed by the present application according to the technical solution and inventive concept of the present application, which should be covered within the protection scope of the present application.

Claims

1. A composite packaging film, characterized in that, It includes an inner layer (100), a middle layer (200), and an outer layer (300). The inner layer (100) comprises polyethylene; The intermediate layer (200) comprises an ethylene-vinyl alcohol copolymer, and the intermediate layer (200) at least partially covers the inner layer (100); The outer layer (300) includes a plastic layer (320) and a fiber layer (310), the fiber layer (310) including cellulose and hemicellulose, the fiber layer (310) at least partially covering the plastic layer (320), the plastic layer (320) including polyethylene, and the plastic layer (320) at least partially covering the intermediate layer (200); The inner layer (100) and the intermediate layer (200), and the intermediate layer (200) and the outer layer (300) are bonded together by an adhesive; the cellulose is nano-protocellulose, and the thickness of the fiber layer (310) accounts for 10%-25% of the total thickness of the outer layer (300); The intermediate layer (200) has at least one layer.

2. The composite packaging film according to claim 1, characterized in that, The thickness of the inner layer (100) is 5μm-20μm; and / or The thickness of the intermediate layer (200) is 10μm-20μm; and / or The outer layer (300) has a thickness of 15μm-30μm.

3. The composite packaging film according to claim 1, characterized in that, The oxygen permeability of the composite packaging film is less than 0.5 cm. 3 / (m 2 ×24h×0.1MPa); and / or The water vapor transmission rate of the composite packaging film is less than 0.2 g / m³. 2 ×24h.

4. A method for preparing a composite packaging film, characterized in that, The method for preparing the composite packaging film as described in any one of claims 1-3 comprises: S100, prepare the plastic layer, intermediate layer, inner layer and fiber solution respectively; S200: The plastic layer, the intermediate layer and the inner layer are laminated together in the order of top to bottom, and the first intermediate is obtained by blown film processing; S300: Coat the fiber solution onto the plastic layer of the first intermediate, and then anneal it to obtain the composite packaging film; An adhesive layer is provided between the inner layer and the intermediate layer, and between the intermediate layer and the inner layer; The fiber solution is a mixed solution of nano-protocellulose and hemicellulose.

5. The preparation method according to claim 4, characterized in that, The S300 includes: S301. After coating the plastic layer of the first intermediate with a crosslinking agent, a fiber solution is then coated on it. After a first annealing treatment, a second intermediate is obtained. S302. Perform a second annealing treatment on the second intermediate to obtain the composite packaging film.

6. The preparation method according to claim 5, characterized in that, The temperature of the first annealing treatment is 60℃-80℃; and / or The temperature of the second annealing treatment is 50℃-70℃; and / or The cooling rate of the first annealing treatment is 0.8℃ / min-1.2℃ / min; and / or The cooling rate of the second annealing process is 1℃ / min-1.5℃ / min.

7. The preparation method according to claim 5, characterized in that, The first annealing process takes 0.5-1 hour; and / or The second annealing process takes 0.5-1 hour.

8. The preparation method according to claim 4, characterized in that, In S200, The blown film process also includes a preheating treatment; The preheating treatment is an infrared preheating treatment.

9. The preparation method according to claim 8, characterized in that, The preheating temperature is 50℃-55℃.

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