A three-layer co-extruded toughened BOPEN film and its preparation method

Abstract

The present application relates to the field of films, and more particularly to a three-layer co-extruded toughened BOPEN film and its preparation method. A three-layer co-extruded toughened BOPEN film comprises a PEN resin core layer and two modified PEN resin outer layers, wherein the PEN resin core layer is positioned between the two modified PEN resin outer layers. The PEN resin core layer is composed of PEN resin, and the modified PEN resin outer layers contain the following raw materials in parts by weight: 70-85 parts PEN resin; 15-22 parts maleic anhydride-grafted polyolefin elastomer composite silica; 2-10 parts toughening agent; and 0.6-1.2 parts antioxidant. This application has the characteristics of improving the toughness and barrier properties of the BOPEN film.

Description

Technical Field

[0001] The present application relates to the field of films, and in particular to a three-layer co-extruded toughened BOPEN film and a preparation method thereof. Background Art

[0002] Polyethylene naphthalate (PEN) is a high-performance polyester commercialized in the 1990s. Its molecular structure differs from that of polyethylene terephthalate (PET) in that the benzene ring in the PET molecule is replaced by a naphthalene ring. The higher rigidity of the naphthalene ring gives PEN unique mechanical, optical, and electrical properties, including airtightness, heat resistance, chemical stability, and the ability to form liquid crystals.

[0003] Currently, PEN applications typically involve melt-extruding PEN resin into thin sheets, which are then stretched longitudinally and transversely to produce biaxially oriented polyethylene naphthalate (BOPEN) film. BOPEN features high heat resistance, excellent strength and rigidity, and good barrier properties. It maintains excellent electrical insulation properties even in high-temperature and high-humidity environments. It also exhibits excellent chemical and oil resistance, dimensional stability, and minimal shrinkage, making it a preferred choice for high-end electrical insulation, magnetic recording materials, and heat-resistant, high-shielding packaging.

[0004] However, the high rigidity of PEN's naphthalene ring reduces the toughness of BOPEN film, resulting in shortcomings such as brittleness and difficulty in stretching. To enhance the toughness of BOPEN film, toughening agents are generally added to the PEN resin for toughening modification. However, the addition of toughening agents reduces the overall strength and rigidity of the material, thereby reducing the material's airtightness and allowing gas molecules to easily penetrate the material. Therefore, excessive addition of toughening agents often leads to a significant decrease in the barrier properties of BOPEN film. Summary of the Invention

[0005] In order to improve the toughness and barrier properties of the BOPEN film, the present application provides a three-layer co-extruded toughened BOPEN film and a preparation method thereof.

[0006] In a first aspect, the present application provides a three-layer co-extruded toughened BOPEN film, which adopts the following technical solution: a three-layer co-extruded toughened BOPEN film, comprising a PEN resin core layer and two modified PEN resin outer layers, wherein the PEN resin core layer is located between the two modified PEN resin outer layers; the PEN resin core layer is composed of PEN resin, and the modified PEN resin outer layers contain the following raw materials in parts by weight:

[0007] 70-85 parts of PEN resin;

[0008] 15-22 parts of maleic anhydride grafted polyolefin elastomer composite silica;

[0009] 2-10 parts of toughening agent;

[0010] 0.6-1.2 parts of antioxidant.

[0011] By adopting the above technical solution, silica can strengthen and stabilize the internal structure of the PEN resin and prevent it from sticking. By compounding with the maleic anhydride-grafted polyolefin elastomer, the compatibility of silica with the PEN resin is improved, thereby further exerting the reinforcing effect of silica, allowing silica to fully fill the loose network in the PEN system, further improving the structural stability of the modified PEN resin, and thus facilitating the improvement of the barrier properties and toughness of the modified PEN resin. At the same time, the maleic anhydride-grafted polyolefin elastomer can also have a toughening effect, which is beneficial to further improve the toughness of the modified PEN resin. Secondly, the toughness of the modified PEN resin is further improved by the combination of a toughening agent. Therefore, the BOPEN film with a three-layer structure composed of a modified PEN resin outer layer and a PEN resin core layer can achieve improvements in toughness and barrier properties under the action of the modified PEN resin. Moreover, with the support of the PEN resin core layer, the BOPEN film is provided with good rigidity, while effectively improving the barrier properties of the BOPEN film.

[0012] Preferably, the raw materials for preparing the maleic anhydride grafted polyolefin elastomer composite silica include maleic anhydride grafted polyolefin elastomer, silane coupling agent and silica, and the weight ratio of the maleic anhydride grafted polyolefin elastomer, silane coupling agent and silica is (4-7): (1.5-2.3): (15-20).

[0013] By adopting the above technical solution, silica is modified by a silane coupling agent to obtain silane coupling agent-modified silica, thereby improving the binding property of silica and maleic anhydride grafted polyolefin elastomer, which is conducive to the stable composite of maleic anhydride grafted polyolefin elastomer and silica, thereby improving the compatibility between silica and PEN resin, and enabling the reinforcing and stabilizing effect of silica to be more stably exerted, which is conducive to achieving the improvement of the barrier properties and toughness of the modified PEN resin. In addition, the toughness of the modified PEN resin is further improved by the maleic anhydride grafted polyolefin elastomer, which is conducive to the stable improvement of the toughness and barrier properties of the BOPEN film.

[0014] Preferably, the silane coupling agent is an aminosilane coupling agent.

[0015] By adopting the above technical solution, silica is modified by an aminosilane coupling agent, and the amino group in the aminosilane coupling agent reacts with the maleic anhydride in the maleic anhydride grafted polyolefin elastomer to form a chemical bond, thereby improving the connection stability between the silane coupling agent-modified silica and the maleic anhydride grafted polyolefin elastomer, which is conducive to the stable modification of the maleic anhydride grafted polyolefin elastomer on silica, and further improving the compatibility between silica and PEN resin, thereby further improving the toughness and barrier properties of the modified PEN resin, so as to achieve further improvement in the toughness and barrier properties of the BOPEN film.

[0016] Preferably, the aminosilane coupling agent is selected from KH-550.

[0017] Preferably, the toughening agent comprises glycidyl methacrylate and ethylene-butyl acrylate copolymer, and the weight ratio of glycidyl methacrylate to ethylene-butyl acrylate copolymer is (2-5): (1.7-2.9).

[0018] By adopting the above technical solution, glycidyl methacrylate and ethylene-butyl acrylate copolymer are combined in a certain proportion, so that the two can complement each other, which is conducive to fully exerting the toughening effect of the toughening agent, thereby effectively improving the toughness of the modified PEN resin; secondly, the epoxy group in glycidyl methacrylate can react and connect with the maleic anhydride in the maleic anhydride grafted polyolefin elastomer composite silica to form a tighter cross-linked network structure, further improving the oxygen barrier properties and maintaining good toughness, so as to obtain a BOPEN film with higher toughness and barrier properties.

[0019] Preferably, the maleic anhydride grafted polyolefin elastomer has a maleic anhydride grafting rate of 3-5%.

[0020] By adopting the above technical solution, the maleic anhydride grafting rate is 3-5%, which is conducive to promoting the compounding of maleic anhydride grafted polyolefin elastomer and silica, so that the modification effect of maleic anhydride grafted polyolefin elastomer on silica can be effectively realized, so as to give full play to the reinforcing effect of silica; and it is conducive to improving the compatibility of maleic anhydride grafted polyolefin elastomer in modified PEN resin, so as to effectively exert the toughening effect of maleic anhydride grafted polyolefin elastomer, thereby further improving the toughness and barrier properties of the modified PEN resin, and then achieving the improvement of the toughness and barrier properties of the BOPEN film.

[0021] Preferably, the antioxidant includes a phosphite antioxidant and a phenolic antioxidant, and the weight ratio of the phosphite antioxidant to the phenolic antioxidant is (0.2-0.4): (0.6-0.8).

[0022] By adopting the above technical solution, the phosphite antioxidant and the phenolic antioxidant are combined in a certain proportion, so that the two produce a synergistic effect, which is beneficial to improving the antioxidant effect of the antioxidant, thereby further improving the antioxidant property and stability of the modified PEN resin.

[0023] Preferably, the phosphite antioxidant is selected from antioxidant 168.

[0024] Preferably, the phenolic antioxidant is selected from antioxidant 1010.

[0025] Preferably, the thickness ratio of the modified PEN resin outer layer, the PEN resin core layer, and the modified PEN resin outer layer is 1:(2-3.5):1.

[0026] By adopting the above technical solution, the modified PEN resin outer layer, the PEN resin core layer, and the modified PEN resin outer layer are combined at a thickness ratio of 1: (2-3.5): 1, which is beneficial to obtaining a three-layer BOPEN film with excellent toughness and barrier properties.

[0027] In a second aspect, the present application provides a method for preparing a three-layer co-extruded toughened BOPEN film, using the following preparation scheme:

[0028] A method for preparing a three-layer co-extruded toughened BOPEN film comprises the following steps:

[0029] S1. The modified PEN resin and the PEN resin were respectively fed into two single-screw extruders, and then the modified PEN resin was melted at 280-300 ℃, while the PEN resin was melted at 265-285 ℃;

[0030] S2 by 240-290 ℃ multi-layer co-extrusion die, the molten modified PEN resin and PEN resin co-extruded, and then calendered 25-35 ℃ cast sheet to obtain a three-layer structure having a thickness of 200-220μm thick sheet;

[0031] S3. The thick sheet is transferred into the longitudinal stretching zone, first preheated by a 110-120 ℃ preheating roller to preheat the thick sheet, and then longitudinally stretched by a 130-150 ℃ stretching roller to stretch the thick sheet;

[0032] S4. After completing longitudinal stretching, the thick sheet enters the preheating zone of the transverse stretching oven and is preheated at 110-125°C. The thick sheet is then transferred to the stretching zone and transversely stretched at 140-150°C to obtain a prefabricated film. The prefabricated film is then transferred to the shaping zone and heated and shaped at 210-230°C. Finally, it is cooled and rolled up to obtain a three-layer co-extruded toughened BOPEN film.

[0033] By adopting the above technical solution, the three-layer co-extruded toughened BOPEN film obtained by the above preparation method has the characteristics of structural stability, and the step-by-step stretching method can improve the uniformity of the film material, which is conducive to the stable realization of the improvement of the toughness and barrier properties of the BOPEN film.

[0034] Preferably, the modified PEN resin is prepared by: first, drying the PEN resin at 100-110° C. for 3-4 hours; then, introducing the dried PEN resin, maleic anhydride grafted polyolefin elastomer composite silica, toughening agent, and antioxidant into a twin-screw extruder, and melt-mixing the raw materials of the modified PEN resin at 265-275° C. to obtain a melt-mixed preform of the modified PEN resin; then, extruding the melt-mixed preform of the modified PEN resin through an extrusion die at 280-290° C. to form pellets, and finally discharging the pellets and drying them at 100-110° C. for 3-4 hours to obtain modified PEN resin pellets.

[0035] By adopting the above technical scheme, the above preparation method is conducive to fully melt-mixing the PEN resin, maleic anhydride grafted polyolefin elastomer composite silica, toughening agent and antioxidant, thereby obtaining a structurally stable modified PEN resin with good toughness and barrier properties, which is conducive to improving the toughness and barrier properties of the BOPEN film.

[0036] Preferably, the preparation method of the maleic anhydride grafted polyolefin elastomer composite silica is as follows: first, a silane coupling agent, silica and a solvent are mixed and heated to 40-50° C., stirred and reacted for 30-50 minutes, and after the reaction is completed, the filtrate is filtered, the filter body is collected, and the filter body is dried to obtain silane coupling agent modified silica, wherein the weight ratio of the silane coupling agent, silica and solvent is (1.5-2.3):(15-20):(65-75); then, the maleic anhydride grafted polyolefin elastomer and the silane coupling agent modified silica are mixed and put into a twin-screw extruder, and then the maleic anhydride grafted polyolefin elastomer and the silane coupling agent modified silica are melt-mixed at 180-190° C. to obtain a melt-mixed preform; finally, the melt-mixed preform is extruded and granulated through an extrusion die head at 270-280° C. to obtain maleic anhydride grafted polyolefin elastomer composite silica particles.

[0037] By adopting the above technical solution, a silane coupling agent-modified silica with good surface activity is prepared; then, a maleic anhydride-grafted polyolefin elastomer and the silane coupling agent-modified silica are melt-mixed through a twin-screw extruder, and the silane coupling agent and maleic anhydride are promoted to react and connect, so that the maleic anhydride-grafted polyolefin elastomer is grafted onto the silica, thereby improving the structural stability of the maleic anhydride-grafted polyolefin elastomer composite silica, and further obtaining a maleic anhydride-grafted polyolefin elastomer composite silica with a stable structure and strong surface properties.

[0038] Preferably, the solvent is selected from ethanol.

[0039] In summary, this application includes at least one of the following beneficial technical effects:

[0040] 1. Silica reinforces and stabilizes the internal structure of the PEN resin, while also providing an anti-sticking effect. Compounding with the maleic anhydride-grafted polyolefin elastomer improves the compatibility of silica with the PEN resin, further enhancing the reinforcing effect of silica. This allows silica to fully fill the loose network in the PEN system, further improving the structural stability of the modified PEN resin and thereby enhancing the barrier properties and toughness of the modified PEN resin. Furthermore, the maleic anhydride-grafted polyolefin elastomer also provides a toughening effect, further enhancing the toughness of the modified PEN resin. Furthermore, the toughness of the modified PEN resin is further enhanced by the addition of a toughening agent. Therefore, the BOPEN film, comprising a three-layer structure of a modified PEN resin outer layer and a PEN resin core layer, exhibits improved toughness and barrier properties under the action of the modified PEN resin. Furthermore, the PEN resin core layer, with its support, provides the BOPEN film with good rigidity, effectively enhancing its barrier properties.

[0041] 2. Modifying silica with a silane coupling agent to obtain silane coupling agent-modified silica improves the binding properties of silica and maleic anhydride-grafted polyolefin elastomer, which is conducive to the stable composite of maleic anhydride-grafted polyolefin elastomer and silica, thereby improving the compatibility between silica and PEN resin and enabling the reinforcing and stabilizing effect of silica to be more stably exerted, thereby facilitating the improvement of the barrier properties and toughness of the modified PEN resin. Furthermore, the toughness of the modified PEN resin is further improved by the maleic anhydride-grafted polyolefin elastomer, thereby facilitating the stable improvement of the toughness and barrier properties of the BOPEN film.

[0042] 3. The combination of glycidyl methacrylate and ethylene-butyl acrylate copolymer in a certain proportion allows the two to complement each other, which is conducive to fully exerting the toughening effect of the toughening agent, thereby effectively improving the toughness of the modified PEN resin; secondly, the epoxy group in glycidyl methacrylate can react and connect with the maleic anhydride in the maleic anhydride grafted polyolefin elastomer composite silica to form a cross-linked network structure, further improving the compatibility of the toughening agent in the modified PEN resin, thereby achieving further improvement in the toughness of the modified PEN resin, and obtaining a BOPEN film with higher toughness. DETAILED DESCRIPTION

[0043] The present application is further described in detail below with reference to the embodiments.

[0044] The PEN resin is made from Japanese Teijin brand TN8065S.

[0045] The maleic anhydride grafted polyolefin elastomer uses American Exxon maleic anhydride grafted polyolefin elastomer with a maleic anhydride grafting rate of 3-5%;

[0046] The ethylene-butyl acrylate copolymer is an ethylene-butyl acrylate copolymer with a brand number of 2308 from Arkema, France;

[0047] Preparation Example

[0048] Preparation Example 1

[0049] Preparation method of maleic anhydride grafted polyolefin elastomer composite silica:

[0050] First, 0.15 kg of KH-550, 1.5 kg of silica and 6.5 kg of ethanol are mixed, heated to 40° C., and stirred for reaction for 30 minutes. After the reaction is completed, the mixture is filtered, the filtrate is collected, and the filtrate is dried to obtain silane coupling agent-modified silica. Next, 0.4 kg of a maleic anhydride-grafted polyolefin elastomer having a maleic anhydride grafting rate of 3% and the silane coupling agent-modified silica are mixed and fed into a twin-screw extruder. The maleic anhydride-grafted polyolefin elastomer and the silane coupling agent-modified silica are then melt-mixed at 180° C. to obtain a melt-mixed preform. Finally, the melt-mixed preform is extruded through an extrusion die head at 270° C. to produce granules to obtain maleic anhydride-grafted polyolefin elastomer composite silica particles.

[0051] Preparation Example 2

[0052] Preparation method of maleic anhydride grafted polyolefin elastomer composite silica:

[0053] First, 0.23 kg of KH-550, 2 kg of silica and 7.5 kg of ethanol are mixed, heated to 50° C., and stirred for reaction for 50 minutes. After the reaction is completed, the mixture is filtered, the filtrate is collected, and the filtrate is dried to obtain silane coupling agent-modified silica. Next, 0.7 kg of a maleic anhydride-grafted polyolefin elastomer having a maleic anhydride grafting rate of 5% and the silane coupling agent-modified silica are mixed and fed into a twin-screw extruder. The maleic anhydride-grafted polyolefin elastomer and the silane coupling agent-modified silica are then melt-mixed at 190° C. to obtain a melt-mixed preform. Finally, the melt-mixed preform is extruded through an extrusion die at 280° C. to produce granules to obtain maleic anhydride-grafted polyolefin elastomer composite silica particles.

[0054] Preparation Example 3

[0055] Preparation method of modified PEN resin:

[0056] First, 7 kg of PEN resin was dried at 100° C. for 3 hours. Next, the dried PEN resin, 1.5 kg of the maleic anhydride-grafted polyolefin elastomer composite silica prepared in Preparation Example 1, 0.2 kg of a toughening agent, and 0.06 kg of an antioxidant were placed in a twin-screw extruder. The raw materials for the modified PEN resin were melt-mixed at 265° C. to obtain a melt-mixed preform of the modified PEN resin. The melt-mixed preform of the modified PEN resin was then extruded through an extrusion die at 280° C. to form pellets. The pellets were discharged and dried at 100° C. for 3 hours to obtain modified PEN resin pellets.

[0057] The toughening agent consists of 0.11 kg of glycidyl methacrylate and 0.09 kg of ethylene-butyl acrylate copolymer; and the antioxidant consists of 0.015 kg of antioxidant 168 and 0.045 kg of antioxidant 1010.

[0058] Preparation Example 4

[0059] Preparation method of modified PEN resin:

[0060] First, 8.5 kg of PEN resin was dried at 110° C. for 4 hours. Next, the dried PEN resin, 2.2 kg of the maleic anhydride-grafted polyolefin elastomer composite silica prepared in Preparation Example 2, 1 kg of a toughening agent, and 0.12 kg of an antioxidant were placed in a twin-screw extruder. The raw materials of the modified PEN resin were melt-mixed at 275° C. to obtain a melt-mixed preform of the modified PEN resin. The melt-mixed preform of the modified PEN resin was then extruded through an extrusion die at 290° C. to form pellets. The pellets were discharged and dried at 110° C. for 4 hours to obtain modified PEN resin pellets.

[0061] The toughening agent consists of 0.63 kg of glycidyl methacrylate and 0.37 kg of ethylene-butyl acrylate copolymer; and the antioxidant consists of 0.04 kg of antioxidant 168 and 0.08 kg of antioxidant 1010.

[0062] Preparation Example 5

[0063] Preparation method of modified PEN resin:

[0064] The difference between this preparation example and preparation example 4 is that 1 kg of glycidyl methacrylate is used as the toughening agent.

[0065] Preparation Example 6

[0066] Preparation method of modified PEN resin:

[0067] The difference between this preparation example and preparation example 4 is that 1 kg of ethylene-butyl acrylate copolymer is specifically selected as the toughening agent.

[0068] Comparative Preparation Example 1

[0069] Preparation method of modified PEN resin:

[0070] The difference between this comparative preparation example and preparation example 4 is that no maleic anhydride grafted polyolefin elastomer composite silica is added.

[0071] Comparative Preparation Example 2

[0072] Preparation method of modified PEN resin:

[0073] The difference between this comparative preparation example and Preparation Example 4 is that an equal amount of silane coupling agent-modified silica prepared in Preparation Example 2 is used to replace the maleic anhydride grafted polyolefin elastomer composite silica, that is, no maleic anhydride grafted polyolefin elastomer composite silica is added, and 2.2 kg of silane coupling agent-modified silica prepared in Preparation Example 2 is added.

[0074] Comparative Preparation Example 3

[0075] Preparation method of modified PEN resin:

[0076] The difference between this comparative preparation example and preparation example 4 is that an equal amount of silica is used to replace the maleic anhydride grafted polyolefin elastomer composite silica, that is, no maleic anhydride grafted polyolefin elastomer composite silica is added, and 2.2 kg of silica is added.

[0077] Example

[0078] Example 1

[0079] Preparation of a three-layer co-extruded toughened BOPEN film:

[0080] S1. The modified PEN resin and PEN resin of Preparation Example 3 were respectively fed into two single-screw extruders, and then melted at 280°C for the modified PEN resin, while at 265°C for the PEN resin was melted;

[0081] S2. The molten modified PEN resin and PEN resin were coextruded through a multi-layer coextrusion die at 240 ° C, and then cast by a calender at 25 ° C to obtain a three-layer thick sheet with a thickness of 200 μm, and the thickness ratio of the modified PEN resin outer layer, the PEN resin core layer, and the modified PEN resin outer layer was 1:2:1;

[0082] S3. The thick sheet is transferred into the longitudinal stretching zone, first preheated by a 110°C preheating roller to preheat the thick sheet, and then longitudinally stretched by a 130°C stretching roller to stretch the thick sheet;

[0083] S4. After completing longitudinal stretching, the thick sheet enters the preheating zone of the transverse stretching oven and is preheated at 110°C. The thick sheet is then transferred to the stretching zone and transversely stretched at 140°C to obtain a prefabricated film. The prefabricated film is then transferred to the shaping zone and heated and shaped at 210°C. Finally, the film is cooled and rolled up to obtain a three-layer co-extruded toughened BOPEN film.

[0084] Example 2

[0085] Preparation of a three-layer co-extruded toughened BOPEN film:

[0086] S1. The modified PEN resin and PEN resin of Preparation Example 4 were respectively put into two single-screw extruders, and then at 300 ℃, the modified PEN resin was melted, while at 285 ℃, the PEN resin was melted;

[0087] S2. The molten modified PEN resin and PEN resin were coextruded through a multi-layer coextrusion die at 290 ° C, and then cast by a calender at 35 ° C to obtain a three-layer thick sheet with a thickness of 220 μm, and the thickness ratio of the modified PEN resin outer layer, the PEN resin core layer, and the modified PEN resin outer layer was 1:3.5:1;

[0088] S3. The thick sheet is transferred into the longitudinal stretching zone, first preheated by a 120°C preheating roller to preheat the thick sheet, and then longitudinally stretched by a 150°C stretching roller to stretch the thick sheet;

[0089] S4. After completing longitudinal stretching, the thick sheet enters the preheating zone of the transverse stretching oven and is preheated at 125°C. The thick sheet is then transferred to the stretching zone and transversely stretched at 150°C to obtain a prefabricated film. The prefabricated film is then transferred to the shaping zone and heated and shaped at 230°C. Finally, the film is cooled and rolled up to obtain a three-layer co-extruded toughened BOPEN film.

[0090] Example 3

[0091] Preparation of a three-layer co-extruded toughened BOPEN film:

[0092] The difference between this embodiment and embodiment 2 is that the modified PEN resin is specifically selected from the modified PEN resin prepared in Preparation Example 5.

[0093] Example 4

[0094] Preparation of a three-layer co-extruded toughened BOPEN film:

[0095] The difference between this embodiment and embodiment 2 is that the modified PEN resin is the modified PEN resin prepared in preparation example 6.

[0096] Comparative Example

[0097] Comparative Example 1

[0098] The difference between this comparative example and Example 2 is that the modified PEN resin is specifically selected from the modified PEN resin prepared in Comparative Preparation Example 1.

[0099] Comparative Example 2

[0100] The difference between this comparative example and Example 2 is that the modified PEN resin is specifically selected from the modified PEN resin prepared in Comparative Preparation Example 2.

[0101] Comparative Example 3

[0102] The difference between this comparative example and Example 3 is that the modified PEN resin is specifically selected from the modified PEN resin prepared in Comparative Preparation Example 3.

[0103] Performance test data

[0104] Test 1: Referring to GB / T 13022-1991 "Test method for tensile properties of plastic films", test specimens were made of the three-layer co-extruded toughened BOPEN films prepared in Examples 1-4 of the present application and Comparative Examples 1-3. The tensile strength test of the test specimens was performed in accordance with the standard at a test speed of 100 mm / min. The test results are shown in Table 1.

[0105] Test 2: Referring to GB / T 13022-1991 "Test method for tensile properties of plastic films", test specimens were made of the three-layer co-extruded toughened BOPEN films prepared in Examples 1-4 of the present application and Comparative Examples 1-3. The test specimens were subjected to elongation at break test according to the standard at a test speed of 100 mm / min. The test results are shown in Table 1.

[0106] Test 3: Referring to GB / T 26253-2010 "Plastic film and sheeting - Determination of water vapor transmission rate - Infrared detector method", the three-layer co-extruded toughened BOPEN films prepared in Examples 1-4 and Comparative Examples 1-3 of the present application were made into test specimens. Then, under the test conditions of temperature of 25°C and relative humidity of 90%, the water vapor transmission rate of the test specimens was tested with reference to GB / T 26253-2010 "Plastic film and sheeting - Determination of water vapor transmission rate - Infrared detector method". The test results are shown in Table 1.

[0107] Test 4: Test specimens of the three-layer co-extruded toughened BOPEN films prepared in Examples 1-4 and Comparative Examples 1-3 were prepared with reference to GB / T 19789-2005 "Plastic Film and Sheeting for Packaging Materials - Oxidative Permeability Test - Coulometric Method" and subjected to oxygen permeability testing in accordance with the standard. The oxygen permeability was calculated and recorded. The test results are shown in Table 1.

[0108] Table 1 Summary of performance test results

[0109]

[0110] Combining Example 2 with Comparative Example 1 and the data in Table 1, it can be seen that the elongation at break of Example 2 is significantly higher. At the same time, the water vapor permeability and oxygen permeability of Example 2 are also significantly lower than those of Comparative Example 1, indicating that the addition of maleic anhydride grafted polyolefin elastomer composite silica to prepare modified PEN resin can effectively improve the toughness and barrier properties of the modified PEN resin, thereby achieving improvement in the toughness and barrier properties of the three-layer co-extruded BOPEN film under the action of the modified PEN resin.

[0111] Combining Comparative Example 1 with Comparative Examples 2-3 and the data in Table 1, it can be seen that compared with Comparative Example 1, the elongation at break of Comparative Example 3 is improved, while the water vapor permeability and oxygen permeability are reduced. However, relative to Example 2, the improvement and reduction are relatively small, indicating that the addition of silica alone has little effect on improving the toughness and barrier properties of the modified PEN resin, thereby making the improvement of the toughness and barrier properties of the three-layer co-extruded BOPEN film not obvious; and according to Comparative Example 2, Comparative Example 2 adds silane coupling agent to modify silica to prepare the modified PEN resin, but the silane coupling agent has little effect on silica. The modification of silica does not significantly promote the improvement of the toughness and barrier properties of the modified PEN resin, indicating that the maleic anhydride grafted polyolefin elastomer needs to be composite-modified with the silane coupling agent modified silica to achieve better results. It can be seen that the silica needs to be modified with a silane coupling agent first to improve the binding property of silica and the maleic anhydride grafted polyolefin elastomer, and then the maleic anhydride grafted polyolefin elastomer is added and composited with the silane coupling agent modified silica to effectively improve the toughness and barrier properties of the modified PEN resin, thereby helping to improve the toughness and barrier properties of the three-layer co-extruded BOPEN film.

[0112] Combining Example 2 with Examples 3-4 and the data in Table 1, it can be seen that when glycidyl methacrylate or ethylene-butyl acrylate copolymer is used alone as a toughening agent to synthesize the modified PEN resin, the toughness and barrier properties of the BOPEN film are both reduced, and when ethylene-butyl acrylate copolymer is used alone as a toughening agent to synthesize the modified PEN resin, the toughness and barrier properties of the BOPEN film decrease even more; it can be seen that the combination of glycidyl methacrylate and ethylene-butyl acrylate copolymer in a specific proportion can effectively improve the toughness and barrier properties of the modified PEN resin, which is conducive to better improving the toughness and barrier properties of the three-layer co-extruded BOPEN film, and under the action of glycidyl methacrylate, the internal structure of the modified PEN resin can be effectively strengthened, thereby achieving further improvement in the toughness and barrier properties of the three-layer co-extruded BOPEN film.

[0113] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A three-layer co-extruded toughened BOPEN film, characterized in that: The invention comprises a PEN resin core layer and two modified PEN resin outer layers, wherein the PEN resin core layer is located between the two modified PEN resin outer layers; the PEN resin core layer is composed of PEN resin, and the modified PEN resin outer layers contain the following raw materials in parts by weight: 70-85 parts of PEN resin; 15-22 parts of maleic anhydride grafted polyolefin elastomer composite silica; 2-10 parts of toughening agent; 0.6-1.2 parts of antioxidant; The raw materials for preparing the maleic anhydride grafted polyolefin elastomer composite silica include maleic anhydride grafted polyolefin elastomer, silane coupling agent and silica, and the weight ratio of the maleic anhydride grafted polyolefin elastomer, silane coupling agent and silica is (4-7): (1.5-2.3): (15-20); The silane coupling agent is an aminosilane coupling agent; the silica is modified by the aminosilane coupling agent, and the amino group in the aminosilane coupling agent reacts with the maleic anhydride in the maleic anhydride grafted polyolefin elastomer to form a chemical bond; The toughening agent comprises glycidyl methacrylate and ethylene-butyl acrylate copolymer, and the weight ratio of the glycidyl methacrylate and ethylene-butyl acrylate copolymer is (2-5): (1.7-2.9); The maleic anhydride grafted polyolefin elastomer has a maleic anhydride grafting rate of 3-5%.

2. A three-layer co-extruded toughened BOPEN film according to claim 1, characterized in that: The antioxidant includes a phosphite antioxidant and a phenolic antioxidant, and the weight ratio of the phosphite antioxidant to the phenolic antioxidant is (0.2-0.4): (0.6-0.8).

3. The three-layer co-extruded toughened BOPEN film according to claim 1, characterized in that: The thickness ratio of the modified PEN resin outer layer, the PEN resin core layer, and the modified PEN resin outer layer is 1:(2-3.5):

1.

4. A method for preparing a three-layer co-extruded toughened BOPEN film, characterized in that: The method for preparing a three-layer co-extruded toughened BOPEN film according to any one of claims 1 to 3 comprises the following steps: S1. The modified PEN resin and the PEN resin were respectively fed into two single-screw extruders, and then the modified PEN resin was melted at 280-300 ℃, while the PEN resin was melted at 265-285 ℃; S2 by 240-290 ℃ multi-layer co-extrusion die, the molten modified PEN resin and PEN resin co-extruded, and then calendered 25-35 ℃ cast sheet to obtain a three-layer structure having a thickness of 200-220μm thick sheet; S3. The thick sheet is transferred into the longitudinal stretching zone, first preheated by a 110-120 ℃ preheating roller to preheat the thick sheet, and then longitudinally stretched by a 130-150 ℃ stretching roller to stretch the thick sheet; S4. After completing longitudinal stretching, the thick sheet enters the preheating zone of the transverse stretching oven and is preheated at 110-125°C. The thick sheet is then transferred to the stretching zone and transversely stretched at 140-150°C to obtain a prefabricated film. The prefabricated film is then transferred to the shaping zone and heated and shaped at 210-230°C. Finally, it is cooled and rolled up to obtain a three-layer co-extruded toughened BOPEN film.

5. The method for preparing a three-layer co-extruded toughened BOPEN film according to claim 4, characterized in that: The preparation method of the modified PEN resin comprises the following steps: first, drying the PEN resin at 100-110° C. for 3-4 hours; then, adding the dried PEN resin, maleic anhydride grafted polyolefin elastomer composite silica, a toughening agent, and an antioxidant into a twin-screw extruder; and melt-mixing the raw materials of the modified PEN resin at 265-275° C. to obtain a melt-mixed preform of the modified PEN resin; then, extruding the melt-mixed preform of the modified PEN resin through an extrusion die at 280-290° C. to form pellets, and finally discharging the pellets and drying them at 100-110° C. for 3-4 hours to obtain modified PEN resin pellets.

6. The method for preparing a three-layer co-extruded toughened BOPEN film according to claim 4, characterized in that: The preparation method of the maleic anhydride grafted polyolefin elastomer composite silica comprises the following steps: first, mixing a silane coupling agent, silica and a solvent, heating the mixture to 40-50° C., stirring and reacting the mixture for 30-50 minutes, filtering and collecting the filtrate after the reaction is completed, and drying the filtrate to obtain silane coupling agent modified silica, wherein the weight ratio of the silane coupling agent, silica and solvent is (1.5-2.3):(15-20):(65-75); then, mixing the maleic anhydride grafted polyolefin elastomer and the silane coupling agent modified silica and feeding the mixture into a twin-screw extruder; then, melt-mixing the maleic anhydride grafted polyolefin elastomer and the silane coupling agent modified silica at 180-190° C. to obtain a melt-mixed preform; and finally, extruding the melt-mixed preform through an extrusion die head at 270-280° C. to produce granules to obtain maleic anhydride grafted polyolefin elastomer composite silica particles.

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