One-way easy-tear composite packaging film and preparation method and application thereof

Abstract

The present invention discloses a unidirectional easy-tear composite packaging film and a preparation method and application thereof, belonging to the technical field of packaging films. The unidirectional easy-tear composite packaging film of the present invention comprises an outer layer, an intermediate layer and an inner layer stacked in sequence; the outer layer comprises the following raw materials: low-density polyethylene, high-density polyethylene, metallocene polyethylene, metallocene polypropylene, polyether polyamine and dibenzoyl peroxide; the intermediate layer comprises the following raw materials: low-density polyethylene, high-density polyethylene and ultra-high molecular weight polyethylene; the inner layer comprises the following raw materials: carboxylated graphene oxide, amino multi-walled carbon nanotubes, organic montmorillonite, protonated polypropylene imine, low-density polyethylene, high-density polyethylene. The packaging film prepared by the present invention not only has easy-tear performance, but also has storage stability, high temperature resistance, low temperature resistance and good mechanical properties. The comprehensive performance of the packaging film is excellent, which expands its application range.

Description

Technical Field

[0001] The invention belongs to the technical field of packaging films, and in particular relates to a one-way easy-tear composite packaging film and a preparation method and application thereof. Background Art

[0002] Packaging film plays a vital role in the packaging industry. It protects products, prolongs shelf life, and facilitates use. Packaging film can be divided into many types according to its material, purpose and characteristics: polyethylene film, polypropylene film, polyester film, polyvinyl chloride film, nylon film, polyurethane film, biodegradable film, easy-tear film, shrink film and anti-fog film, etc.

[0003] Easy-tear film is a specially designed packaging film that is designed to be easy to tear by hand and is suitable for scenarios where the package needs to be opened quickly. The film is easy to tear and has excellent sealing properties. Easy-tear film is widely used in many industries, including but not limited to food packaging, such as candy, biscuits and snacks; medical supply packaging, especially those disposable products that require easy opening and hygiene; personal care products, such as cosmetics and shampoo; electronic product packaging, such as small electronic devices such as batteries and chargers; and pharmaceutical packaging, such as tablets and capsules. The application field of easy-tear film is very wide. Due to the different application fields and different filling materials, the single tearing performance and sealing performance of the easy-tear film can no longer meet the requirements of various application fields for easy-tear film. Existing easy-tear films also have the following disadvantages:

[0004] (1) When the tear film is filled with some granular products or special-shaped products, it is easy to be damaged during transportation and storage, resulting in product failure and loss.

[0005] (2) After the tear film is filled with products, it is usually necessary to store it in a low-temperature or high-temperature environment according to the properties of the product itself. However, the low-temperature environment and the high-temperature environment will affect the tear film itself, causing its mechanical properties to deteriorate and even break.

[0006] (3) If the tear film is filled with products that need to be stored for a long time, external factors such as humidity and oxygen will also affect the performance of the tear film, shortening the service life of the tear film.

[0007] (4) When the tear film is filled with some acidic or alkaline substances, it will corrode the tear film, causing the tear film to fail and the stored substances to leak.

[0008] Therefore, there is an urgent need for an easy-to-tear packaging film with high mechanical strength, high temperature resistance, low temperature resistance, chemical environment resistance and long service life. Summary of the invention

[0009] The purpose of the present invention is to provide a one-way easy-tear composite packaging film and a preparation method and application thereof, so as to solve the problems of low mechanical strength, poor high temperature resistance, poor low temperature resistance and short service life of the above-mentioned easy-tear film. The packaging film prepared by the present invention not only has easy-tear performance, but also has storage stability, high temperature resistance, low temperature resistance and good mechanical properties. The comprehensive performance of the packaging film is excellent, and its application range is expanded.

[0010] To achieve the above-mentioned object, the first aspect of the present invention provides a unidirectional easy-tear composite packaging film, comprising an outer layer, an intermediate layer and an inner layer stacked in sequence;

[0011] The outer layer comprises the following raw materials in parts by weight:

[0012]

[0013] The middle layer includes the following raw materials in parts by weight:

[0014] 40-50 parts of low-density polyethylene

[0015] High-density polyethylene 20-30 parts

[0016] 30-45 parts of ultra-high molecular weight polyethylene;

[0017] The inner layer comprises the following raw materials in parts by weight:

[0018]

[0019] Preferably, the melt mass flow rate of the low-density polyethylene is 70 g / 10 min and the density is 0.918 g / cm 2 ; The melt mass flow rate of high-density polyethylene is 8.0g / 10min and the density is 0.957g / cm 2 The melt mass flow rate of ultra-high molecular weight polyethylene is 2.0 g / 10 min and the density is 0.947 g / cm 2 .

[0020] Low-density polyethylene was purchased from Zhangmutou Hailan Plastic Processing Factory in Dongguan City, model number is MG70.

[0021] High-density polyethylene was purchased from Dongguan Canhui New Material Technology Co., Ltd., model ME8000.

[0022] Ultra-high molecular weight polyethylene was purchased from Zhejiang Shending Chemical Materials Co., Ltd., model UHMW-PE.

[0023] In order to ensure easy tearing, the current easy-tear composite packaging film often has the problem of low mechanical strength. When filled with some angular and granular materials, it is more likely to be damaged during transportation and storage. In order to solve the above problems and increase the mechanical strength of the packaging film, the present invention specifically adds carbon materials and montmorillonite in the inner layer, wherein the carbon materials include graphene oxide and multi-walled carbon nanotubes. Analysis of the reasons: Graphene oxide has a very high Young's modulus and fracture strength, which can significantly improve the tensile strength and elastic modulus of the composite material. Carbon nanotubes have extremely high strength and elastic modulus, which can effectively enhance the tensile strength and toughness of the composite material. Montmorillonite enhances the mechanical strength of the packaging film by intercalation or peeling.

[0024] The present invention continues to develop and find that although the addition of carbon materials and montmorillonite can improve the mechanical properties of the packaging film, it is difficult to maintain the mechanical strength of the packaging film under high and low temperature conditions, resulting in a decrease in the mechanical properties of the packaging film and cannot be used. The present invention uses functionalized carbon materials and montmorillonite to replace pure carbon materials and montmorillonite. The specific substances used are carboxylated graphene oxide, amino multi-walled carbon nanotubes and organic montmorillonite. The above functionalized groups can increase the compatibility between carbon materials and montmorillonite and other organic substances polyethylene, and improve high temperature resistance and low temperature resistance. Analysis of the reasons: Carboxylated graphene oxide has high thermal stability and is not easily decomposed under high temperature conditions. Carboxylated graphene oxide can form a stronger interaction between its carboxyl group and the polymer matrix, further improve the thermal stability of the composite material, and can also maintain a certain toughness at low temperatures to prevent brittle cracking. Aminated multi-walled carbon nanotubes themselves have very high thermal conductivity and thermal stability. Aminated modification can improve the interaction between carbon nanotubes and polymer matrices, improve the toughness of the packaging film, and help to improve the flexibility of the material at low temperatures without brittle cracking. Organic montmorillonite can improve the thermal stability of packaging films. Its layered structure can act as an insulating layer at high temperatures, reducing heat transfer to the polymer matrix. Especially at low temperatures, it can enhance the toughness of the packaging film through intercalation or peeling, so that it still maintains good performance at low temperatures.

[0025] The present invention continues to study and find that, although the modification of the inorganic material added above can improve the high temperature resistance and low temperature resistance of the packaging film, since the material packaged by the packaging film is generally prevented from being stored in the air containing oxygen and water, the storage time needs to be determined according to the material filled in the packaging film. Once the filled material is stored for too long, more than two years, with the invasion of oxygen and water, it will affect the life of the packaging film, and then the filled material will deteriorate. In view of this problem, the present invention continues to add protonated polypropylene imine to improve the inorganic material and increase the storage stability of the packaging film. Analysis of the reasons: The cationic properties of protonated polypropylene imine interact electrostatically with the anions or hydrophilic groups on the surface of inorganic materials such as carboxylated graphene oxide, amino multi-walled carbon nanotubes and organic montmorillonite, thereby enhancing the interfacial interaction between the inorganic material and the organic polymer matrix. The cation exchange liquid prepared with protonated polypropylene imine in the present invention helps the inorganic material to be evenly dispersed in the polymer matrix, avoiding agglomeration, and plays an important role in improving the storage stability of the packaging film. After the inorganic material is modified, its surface properties change, which can reduce the adsorption and penetration of water molecules, thereby improving the resistance of the packaging film to humidity. The layered structure formed by materials such as graphene oxide can serve as a physical barrier to reduce the ability of water molecules to penetrate the packaging film. The modified inorganic material can form a dense protective layer to reduce the chance of oxygen molecules contacting the polymer matrix, thereby reducing the possibility of oxidation reactions. Therefore, better interface interaction between the modified inorganic material and the polymer matrix can improve the overall structural stability of the composite material, so that it maintains good physical and chemical properties under long-term storage conditions. The inner layer in the present invention can not only improve the water and oxygen resistance of the packaging film, but also improve the corrosion resistance of the inner layer, which is convenient for the packaging film to be filled with corrosive substances.

[0026] Preferably, the total amine content of the polyether polyamine is 224.0 to 381.5 mgKOH / g.

[0027] The polyether polyamines were purchased from Shandong Pinshang New Materials Co., Ltd., with models T-403 and D-400.

[0028] The outer layer in the present invention is in direct contact with the external environment, and the water and oxygen resistance of the outer layer needs to be further improved to ensure that the outside and inside of the packaging film are not affected by the external environment, thereby improving the service life of the packaging film as a whole. The present invention not only uses low-density polyethylene, high-density polyethylene, metallocene polyethylene and metallocene polypropylene as mixed materials, but also adds polyether polyamine and initiator dibenzoyl peroxide to make the whole chemical reaction, increase the degree of cross-linking, and form a denser protective film. Analysis of the reasons: The cross-linking reaction of the above substances can form a three-dimensional network structure, which reduces the chance of water molecules penetrating into the interior of the packaging film, thereby improving the barrier properties of the packaging film. After cross-linking, the gaps between the polymer chains are reduced, which reduces the adsorption and diffusion capacity of water molecules, thereby reducing water penetration. The cross-linking reaction of the above substances can limit the movement of the polymer chains, reduce the formation of free radicals, and thus reduce the possibility of oxidation reactions. The cross-linked polymer network structure is more stable and not easily attacked by oxygen, so the service life of the packaging film can be extended.

[0029] The polyether polyamine in the present invention is a part of the crosslinking, and the total amine amount directly affects the degree of the crosslinking reaction. An appropriate total amine amount can ensure that the crosslinking between polymer chains is appropriate, neither excessive nor insufficient, so as to obtain the best mechanical strength and durability.

[0030] Preferably, the melt index of the metallocene polyethylene is 3.7 g / 10 min, and the melt index of the metallocene polypropylene is 30 g / 10 min.

[0031] Metallocene polyethylene was purchased from Shanghai Gongying Plastic Chemical Co., Ltd., model AT 6111.

[0032] Metallocene polypropylene was purchased from Suzhou Lutuo Materials Co., Ltd., model number M8825KZ.

[0033] Preferably, the diameter of the carboxylated graphene oxide is 0.5 to 5 μm, and the thickness is 0.8 to 1.2 nm; the outer diameter of the amino-modified multi-walled carbon nanotube is 8 to 15 μm, and the length is 50 μm.

[0034] Carboxylated graphene oxide was purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., model number XF004.

[0035] Aminated multi-walled carbon nanotubes were purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., model number XF003.

[0036] Organic montmorillonite was purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., model XFI45.

[0037] Preferably, the thickness of the outer layer is 20 to 30 μm.

[0038] Preferably, the thickness of the intermediate layer is 50-60 μm.

[0039] Preferably, the thickness of the inner layer is 20 to 30 μm.

[0040] A second aspect of the present invention provides a method for preparing a unidirectional easy-tear composite packaging film, comprising the following steps:

[0041] a) mixing the raw materials according to the respective recipes of the outer layer and the middle layer to obtain an outer layer mixture and a middle layer mixture respectively;

[0042] b) dissolving polypropylene imine in ethanol to form a solution, wherein the mass volume ratio of polypropylene imine to ethanol is 1-5 g:100 mL, adding hydrochloric acid to the solution to adjust the pH value of the solution to 3-4, and continuously stirring to complete the protonation process of the polypropylene imine;

[0043] The protonated polypropylene imine solution is transferred to a rotary evaporator for rotary evaporation to remove the solvent, and then filtered to remove solid impurities, and then activated carbon is added, the amount of activated carbon added is 0.5% to 0.8% of the volume of the protonated polypropylene imine solution, stirred for 30 to 60 minutes, filtered to remove the activated carbon, dried and recrystallized to obtain protonated polypropylene imine, and the protonated polypropylene imine is added to ethanol to form a cation exchange liquid, the mass concentration of the protonated polypropylene imine in the cation exchange liquid is 10% to 20%, and is set aside;

[0044] c) mixing the carboxylated graphene oxide, the amino multi-walled carbon nanotubes and the organic montmorillonite in parts by weight to obtain a mixture;

[0045] d) gradually adding the mixture into the cation exchange liquid and stirring for 30 to 60 minutes, and then heating at 60 to 65° C. for 2 to 4 hours. After the reaction is completed, filtering, washing and drying to obtain a modified inorganic material;

[0046] e) mixing the inorganic material with the low-density polyethylene and the high-density polyethylene in the inner layer to obtain an inner layer mixture;

[0047] f) adding the outer layer mixture, the middle layer mixture and the inner layer mixture into three hoppers of an extruder respectively, and performing a three-layer co-extrusion blown film process, the temperature of the extruder is 180-230° C., to obtain a film;

[0048] g) cooling and winding the film to obtain a unidirectional easy-tear composite packaging film.

[0049] CAS of polypropyleneimine: 121263-90-9.

[0050] A third aspect of the present invention provides an application of a one-way easy-tear composite packaging film in the fields of food packaging, medical product packaging, personal care product packaging, pharmaceutical packaging and electronic product packaging.

[0051] Therefore, the present invention adopts the above-mentioned one-way easy-tear composite packaging film and its preparation method and application, which have the following beneficial effects:

[0052] 1. The use of metallocene polyolefin, low-density polyethylene and high-density polyethylene in the present invention can significantly enhance the mechanical strength of the easy-tear film, wherein the use of metallocene polyolefin (such as metallocene polyethylene and metallocene polypropylene) can improve the tensile strength and toughness of the film, and different combinations of low-density polyethylene and high-density polyethylene provide good flexibility and impact resistance. The specific melt flow rates of various substances ensure the plasticity and formability of the materials during processing, which helps to form a film with a more uniform structure and higher strength.

[0053] 2. The use of metallocene polyolefin, low-density polyethylene and high-density polyethylene in the present invention can also significantly enhance the temperature resistance of the easy-tear film. Among them, high-density polyethylene has good heat resistance and can ensure that the packaging film remains stable under high temperature conditions. Due to its special molecular structure, metallocene polyolefin improves the toughness of the film under extreme temperature conditions. The specific melt flow rate helps to control the fluidity of the material at different temperatures, so that the film also has good flexibility in low temperature environments.

[0054] 3. The addition of inorganic materials in the present invention can improve the barrier properties. The addition of carboxylated graphene oxide and amino multi-walled carbon nanotubes can effectively block the penetration of water vapor and oxygen, and reduce the possibility of moisture or oxidation of packaging. Organic montmorillonite, as a nano-scale filler, helps to build a denser barrier layer and further reduce the permeability of gas and moisture.

[0055] 4. The addition of polyether polyamine as an additive in the present invention can improve the resistance of the film to chemicals, especially for some products containing active chemical ingredients, such as certain medicines and personal care products. The use of protonated polypropyleneimine can increase the chemical stability and corrosion resistance of the film, and also help to improve the adhesion between the layers of materials.

[0056] 5. The inorganic filler in the inner layer of the present invention (such as carboxylated graphene oxide, amino multi-walled carbon nanotubes, etc.) can improve the surface properties of the film after surface modification, making it easier to tear.

[0057] The technical solution of the present invention is further described in detail below through embodiments. DETAILED DESCRIPTION

[0058] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and a specific operation process, but the present invention is not limited to this embodiment.

[0059] Example 1

[0060] This embodiment provides a unidirectional easy-tear composite packaging film, comprising an outer layer, a middle layer and an inner layer stacked in sequence;

[0061] The outer layer comprises the following raw materials in parts by weight:

[0062]

[0063] The middle layer includes the following raw materials in parts by weight:

[0064] 45 parts of low density polyethylene

[0065] High density polyethylene 25 parts

[0066] 40 parts of ultra high molecular weight polyethylene;

[0067] The inner layer comprises the following raw materials in parts by weight:

[0068]

[0069] The melt mass flow rate of low-density polyethylene is 70g / 10min and the density is 0.918g / cm 2 The low-density polyethylene was purchased from Zhangmutou Hailan Plastic Processing Factory in Dongguan City, model number is MG70.

[0070] The melt mass flow rate of high-density polyethylene is 8.0g / 10min and the density is 0.957g / cm 2 High-density polyethylene was purchased from Dongguan Canhui New Material Technology Co., Ltd., model ME8000.

[0071] The melt mass flow rate of ultra-high molecular weight polyethylene is 2.0 g / 10 min and the density is 0.947 g / cm 2 Ultra-high molecular weight polyethylene was purchased from Zhejiang Shending Chemical Materials Co., Ltd., model UHMW-PE.

[0072] The total amine content of the polyether polyamine is 342.2-381.5 mgKOH / g. The polyether polyamine is purchased from Shandong Pinshang New Materials Co., Ltd. with a model number of T-403.

[0073] The melt index of the metallocene polyethylene is 3.7 g / 10 min. The metallocene polyethylene is purchased from Shanghai Gongying Plastic Chemical Co., Ltd. with a model number of AT 6111.

[0074] The melt index of metallocene polypropylene is 30 g / 10 min. The metallocene polypropylene is purchased from Suzhou Lutuo Materials Co., Ltd., model number is M8825KZ.

[0075] The sheet diameter of carboxylated graphene oxide is 0.5-5 μm, and the thickness is 0.8-1.2 nm. The carboxylated graphene oxide is purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., and the model is XF004.

[0076] The outer diameter of the aminated multi-walled carbon nanotubes is 8-15 μm, and the length is 50 μm. The aminated multi-walled carbon nanotubes are purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., and the model number is XF003.

[0077] Organic montmorillonite was purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., model XFI45.

[0078] CAS of polypropyleneimine: 121263-90-9.

[0079] This embodiment also provides a method for preparing a unidirectional easy-tear composite packaging film, comprising the following steps:

[0080] a) mixing the raw materials according to the respective recipes of the outer layer and the middle layer to obtain an outer layer mixture and a middle layer mixture respectively;

[0081] b) dissolving polypropylene imine in ethanol to form a solution, wherein the mass volume ratio of polypropylene imine to ethanol is 3 g:100 mL, adding hydrochloric acid to the solution to adjust the pH value of the solution to 3.5, and continuously stirring to complete the protonation process of the polypropylene imine;

[0082] The protonated polypropylene imine solution is transferred to a rotary evaporator for rotary evaporation to remove the solvent, and then filtered to remove solid impurities, and then activated carbon is added, the amount of activated carbon added is 0.6% of the volume of the protonated polypropylene imine solution, stirred for 40 minutes, filtered to remove the activated carbon, dried and recrystallized to obtain protonated polypropylene imine, and the protonated polypropylene imine is added to ethanol to form a cation exchange liquid, the mass concentration of the protonated polypropylene imine in the cation exchange liquid is 15%, and is set aside;

[0083] c) mixing the carboxylated graphene oxide, the amino multi-walled carbon nanotubes and the organic montmorillonite in parts by weight to obtain a mixture;

[0084] d) gradually adding the mixture into the cation exchange liquid and stirring for 50 minutes, and then heating at 62° C. for 3 hours. After the reaction is completed, filtering, washing and drying to obtain a modified inorganic material;

[0085] e) mixing the inorganic material with the low-density polyethylene and the high-density polyethylene in the inner layer to obtain an inner layer mixture;

[0086] f) adding the outer layer mixture, the middle layer mixture and the inner layer mixture into three hoppers of an extruder respectively, and performing a three-layer co-extrusion blown film process, the temperature of the extruder is 225° C., to obtain a film; the thickness of the outer layer is 25 μm, the thickness of the middle layer is 55 μm, and the thickness of the inner layer is 25 μm;

[0087] g) cooling and winding the film to obtain a unidirectional easy-tear composite packaging film.

[0088] Example 2

[0089] The difference between this embodiment and embodiment 1 is that the formula of the packaging film is different.

[0090] A one-way easy-tear composite packaging film, comprising an outer layer, a middle layer and an inner layer stacked in sequence;

[0091] The outer layer comprises the following raw materials in parts by weight:

[0092]

[0093] The middle layer includes the following raw materials in parts by weight:

[0094] 48 parts of low density polyethylene

[0095] High-density polyethylene 21 parts

[0096] 42 parts of ultra high molecular weight polyethylene;

[0097] The inner layer comprises the following raw materials in parts by weight:

[0098]

[0099] Comparative Example 1

[0100] The difference between this comparative example and Example 1 is that the carboxylated graphene oxide in the inner layer is replaced by graphite oxide powder, and the graphite oxide powder is purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., model XF003, sheet diameter: 0.5-5 μm, thickness: 1-3 nm.

[0101] Comparative Example 2

[0102] The difference between this comparative example and Example 1 is that the inner layer replaces the amino multi-walled carbon nanotubes with multi-walled carbon nanotubes, which are purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., model XFM10, with a length of 0.5-2 μm and a diameter of 8-15 nm.

[0103] Comparative Example 3

[0104] The difference between this comparative example and Example 1 is that the inner layer uses inorganic montmorillonite instead of organic montmorillonite, which is purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd. and has a model number of XFI44.

[0105] Comparative Example 4

[0106] The difference between this comparative example and Example 1 is that the polypropylene imine in the inner layer is not protonated.

[0107] Comparative Example 5

[0108] The difference between this comparative example and Example 1 is that no protonated polypropyleneimine is added to the inner layer.

[0109] Comparative Example 6

[0110] The difference between this comparative example and Example 1 is that the total amine content of the polyether polyamine in the outer layer is 52.2-58.9 mgKOH / g, and the polyether polyamine is purchased from Shandong Pinshang New Materials Co., Ltd., model number T-2000.

[0111] Comparative Example 7

[0112] The difference between this comparative example and Example 1 is that no polyether polyamine is added to the outer layer.

[0113] Comparative Example 8

[0114] The difference between this comparative example and Example 1 is that only metallocene polyethylene is added to the outer layer, and an equal amount of metallocene polyethylene is used to replace metallocene polypropylene.

[0115] Comparative Example 9

[0116] The difference between this comparative example and Example 1 is that only metallocene polypropylene is added to the outer layer, and an equal amount of metallocene polypropylene is used to replace metallocene polyethylene.

[0117] Performance Testing

[0118] (1) The packaging films prepared in Examples 1-2 and Comparative Examples 1-9 were subjected to mechanical strength tests, specifically using the film tensile properties test method GB / T1040.3-2006 to conduct tensile properties tests.

[0119] Table 1 Mechanical properties test results

[0120]

[0121]

[0122] (2) The packaging films prepared in Examples 1-2 and Comparative Examples 1-9 were placed at 100° C. for 12 h, taken out, and allowed to cool to room temperature. The tensile properties were tested and the tensile strength retention and elongation at break retention were calculated.

[0123] The packaging films prepared in Examples 1-2 and Comparative Examples 1-9 were placed at -20°C for 12 hours, taken out, and allowed to cool to room temperature. Tensile properties were tested, and the tensile strength retention and elongation at break retention were calculated.

[0124] Tensile strength retention rate = (tensile strength of untreated packaging film - tensile strength of packaging film after high temperature or low temperature treatment) / tensile strength of untreated packaging film × 100%

[0125] Retention rate of elongation at break = (elongation at break of untreated packaging film - elongation at break of packaging film after high temperature or low temperature treatment) / elongation at break of untreated packaging film × 100%.

[0126] Table 2 Temperature resistance test results

[0127]

[0128] (3) The packaging films prepared in Examples 1-2 and Comparative Examples 1-9 were placed in a sealed test box, and water vapor and oxygen were added into the sealed test box, wherein the humidity was 85% RH, the oxygen concentration was 30%, and the temperature was 50°C. After being placed for 7 days, the packaging films were taken out, cooled to room temperature, and subjected to a tensile performance test to calculate the tensile strength retention rate and the elongation at break retention rate.

[0129] Table 3 Storage stability test results

[0130]

[0131] (4) The packaging films prepared in Examples 1-2 and Comparative Examples 1-9 were placed in a 3% dilute sulfuric acid solution at 30°C for 3 days, then taken out and cleaned with pure water. The tensile properties were tested and the tensile strength retention and elongation at break retention were calculated.

[0132] The packaging films prepared in Examples 1-2 and Comparative Examples 1-9 were placed in a 3% sodium hydroxide solution at 30°C for 3 days, then taken out, cleaned with pure water, and subjected to a tensile performance test to calculate the tensile strength retention rate and elongation at break retention rate.

[0133] Table 4 Corrosion resistance test results

[0134]

[0135]

[0136] It can be seen from the above performance test results that the packaging films prepared in Examples 1-2 have the advantages of easy tearing, corrosion resistance, storage stability, strong mechanical strength and temperature resistance. In particular, the comprehensive performance of Example 1 is the most outstanding, which is mainly due to the optimization and improvement of the composition formula of the outer layer and the inner layer.

[0137] However, the comparative examples are significantly inferior to the embodiments in the corresponding performance tests because they do not adopt the necessary technical solutions. In comparative example 1, the type of carboxylated graphene oxide is changed, and non-functionalized graphite oxide powder is used. From the results, it can be seen that the effects of mechanical strength, temperature resistance, storage stability and acid and alkali resistance are reduced, proving that the functionalization of graphene oxide has an important influence on the improvement of the comprehensive performance of the packaging film. In comparative example 2, the type of amino-modified multi-walled carbon nanotubes is changed, and non-functionalized multi-walled carbon nanotubes are used. From the results, it can be seen that the comprehensive performance of the packaging film is also reduced. In comparative example 3, the type of organic montmorillonite is changed, and inorganic montmorillonite is used. From the results, it can be seen that the comprehensive performance of the packaging film is also reduced. From comparative examples 1-3, it can be seen that after the added inorganic filler is functionalized, the compatibility between the inorganic filler and the polymer matrix can be improved, thereby improving the comprehensive performance of the packaging film. The polypropylene imine in Comparative Example 4 was not protonated. From the results, it can be seen that the comprehensive properties of the packaging film, such as mechanical strength, temperature resistance, and corrosion resistance, all decreased, indicating that the protonation of polypropylene imine plays an important role in improving the comprehensive properties of the packaging film. In Comparative Example 5, no protonated polypropylene imine was added. From the results, it can be seen that the comprehensive properties of the packaging film further decreased compared with Comparative Example 4, indicating that protonated polypropylene imine plays an important role in further increasing the binding performance between the inorganic filler and the polymer matrix and further improving the comprehensive properties of the packaging film. In Comparative Example 6, the total amine amount of the polyether polyamine in the outer layer was changed. From the results, it can be seen that the various properties of the packaging film all decreased to varying degrees, indicating that the total amine amount of the polyether polyamine is directly related to the occurrence of the cross-linking reaction of the outer layer, affecting the cross-linking density. Only within the appropriate total amine amount range can the comprehensive properties of the packaging film be improved. In Comparative Example 7, no polyether polyamine was added. From the results, it can be seen that compared with Comparative Example 6, the various properties of the packaging film prepared in Comparative Example 7 further decreased, indicating that the addition of polyether polyamine has an important influence on improving the performance of the packaging film. Comparative Examples 8 and 9 respectively use a metallocene polyolefin. From the results, it can be seen that when a metallocene polyolefin (metallocene polyethylene or metallocene polypropylene) is used, the comprehensive performance of the packaging film is significantly reduced, indicating that the simultaneous addition of two metallocene polyolefins can construct a denser outer film structure and improve the overall performance of the packaging film. The above experimental results further prove the importance of the technical solution defined in the present invention for its technical effect.

[0138] Therefore, the present invention adopts a unidirectional easy-tear composite packaging film with the above structure and its preparation method and application. The prepared packaging film not only has easy-tear performance, but also has storage stability, high temperature resistance, low temperature resistance and good mechanical properties. The comprehensive performance of the packaging film is excellent, which expands its application range.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A one-way easy-tear composite packaging film, characterized in that: It includes an outer layer, an intermediate layer and an inner layer stacked in sequence, in parts by weight; The outer layer includes the following materials: 35~45 parts of low density polyethylene High-density polyethylene 45~55 parts Metallocene polyethylene 3~5 parts Metallocene polypropylene 10~15 parts Polyether polyamine 10~15 parts 0.5~2 parts of dibenzoyl peroxide; The middle layer includes the following materials: 40~50 parts of low density polyethylene High-density polyethylene 20~30 parts 30-45 parts of ultra-high molecular weight polyethylene; The inner layer includes the following materials: 2.5~3.5 parts of carboxylated graphene oxide Aminated multi-walled carbon nanotubes 0.75~1.5 parts 3~5 parts of organic montmorillonite Protonated polypropylene imine 10~15 parts 30~50 parts of low density polyethylene High-density polyethylene 20-35 parts; The diameter of carboxylated graphene oxide is 0.5~5μm, and the thickness is 0.8~1.2nm; the outer diameter of amino-modified multi-walled carbon nanotubes is 8~15μm, and the length is 50μm; The total amine content of polyether polyamine is 224.0~381.5mgKOH / g; The method for preparing a packaging film comprises the following steps: a) mixing the raw materials according to the respective recipes of the outer layer and the middle layer to obtain an outer layer mixture and a middle layer mixture respectively; b) dissolving polypropylene imine in ethanol to form a solution, wherein the mass volume ratio of polypropylene imine to ethanol is 1-5 g:100 mL, adding hydrochloric acid to the solution to adjust the pH value of the solution to 3-4, and continuously stirring to complete the protonation process of the polypropylene imine; The protonated polypropylene imine solution is transferred to a rotary evaporator for rotary evaporation to remove the solvent, and then filtered to remove solid impurities, and then activated carbon is added, the amount of activated carbon added is 0.5-0.8% of the volume of the protonated polypropylene imine solution, stirred for 30-60 minutes, filtered to remove the activated carbon, dried and recrystallized to obtain protonated polypropylene imine, and the protonated polypropylene imine is added to ethanol to form a cation exchange liquid, the mass concentration of the protonated polypropylene imine in the cation exchange liquid is 10-20%, and is set aside; c) mixing carboxylated graphene oxide, amino-modified multi-walled carbon nanotubes and organic montmorillonite in parts by weight to obtain a mixture; d) gradually adding the mixture into the cation exchange liquid and stirring for 30-60 minutes, and then heating at 60-65°C for 2-4 hours. After the reaction is completed, filtering, washing and drying are performed to obtain a modified inorganic material; e) mixing the inorganic material with the low-density polyethylene and high-density polyethylene in the inner layer to obtain an inner layer mixture; f) adding the outer layer mixture, the middle layer mixture and the inner layer mixture into three hoppers of an extruder respectively, and performing a three-layer co-extrusion blown film process, the temperature of the extruder is 180-230° C., and obtaining a film; g) Cooling and winding the film to obtain a unidirectional easy-tear composite packaging film.

2. The one-way tearable composite packaging film according to claim 1, characterized in that: The melt mass flow rate of low-density polyethylene is 70g / 10min and the density is 0.918g / cm 2 ; The melt mass flow rate of high-density polyethylene is 8.0g / 10min and the density is 0.957g / cm 2 The melt mass flow rate of ultra-high molecular weight polyethylene is 2.0 g / 10 min and the density is 0.947 g / cm 2 .

3. The one-way tearable composite packaging film according to claim 1, characterized in that: The melt index of the metallocene polyethylene is 3.7 g / 10 min, and the melt index of the metallocene polypropylene is 30 g / 10 min.

4. The one-way tearable composite packaging film according to claim 1, characterized in that: The thickness of the outer layer is 20~30μm.

5. The one-way tearable composite packaging film according to claim 1, characterized in that: The thickness of the middle layer is 50~60μm.

6. The one-way tearable composite packaging film according to claim 1, characterized in that: The thickness of the inner layer is 20~30μm.

7. Use of the unidirectional easy-tear composite packaging film according to any one of claims 1 to 6 in the fields of food packaging, medical product packaging, personal care product packaging, pharmaceutical packaging and electronic product packaging.

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