Three-bubble nine-layer co-extrusion production process of high-barrier heat-shrinkable cover film

Abstract

The invention is applicable to the technical field of cover films, and provides a three-bubble nine-layer co-extrusion production process of a high-barrier heat-shrinkable cover film, which comprises the following steps: weighing raw materials of each layer; melting each layer of raw materials through a screw rod, extruding in a nine-layer circular extruder, and superposing multiple layers to form a film blank; the film blank is rapidly cooled and formed by cooling water at the temperature of 5-20 DEG C, and then enters an infrared heating system to be heated to the blowing temperature of 80-90 DEG C; the film blank is longitudinally stretched, compressed air is introduced for transverse inflation, then the film blank enters an infrared heating cylinder for shaping treatment, and a film is obtained through air ring cooling; the film is subjected to corona treatment and ultraviolet irradiation treatment through a corona machine, the film is rolled, and the high-barrier heat shrinkage cover film is obtained.The prepared high-barrier heat shrinkage film is high in barrier property to air and water vapor and good in mechanical property, and the modified lignin, the modified polyethylene glycol and the modified aerogel are added into the bonding layer and cooperate with one another, so that the high-barrier heat shrinkage cover film is obtained. The barrier property and the mechanical property of the thermal shrinkage film are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of cover films, and in particular relates to a three-bubble method nine-layer co-extrusion production process of a high-barrier heat shrink cover film. Background Art

[0002] With the improvement of economic conditions and the improvement of people's quality of life, consumers are paying more and more attention to the safety and nutrition of food. However, most foods are easily polluted by moisture, oxygen, microorganisms, etc. in the environment, resulting in quality degradation and deterioration. Therefore, high-barrier food packaging that can block water vapor, oxygen, etc. has been rapidly developed and widely used in recent years. High-barrier plastic packaging has greater advantages in the food industry than traditional barrier packaging materials. It has the advantages of excellent barrier properties, relatively low cost, easy use, good transparency, strong printing adaptability, good mechanical properties, etc., and can play a good role in preserving quality, preserving freshness, and extending shelf life.

[0003] Functional films are one of the most promising application areas in the development of new packaging technologies. Especially in terms of barrier properties, high-barrier films have excellent barrier properties and play a role in preserving food quality, keeping it fresh and extending the life of goods, so they have become the focus of enterprise research and development. Summary of the invention

[0004] The present invention provides a three-bubble method nine-layer co-extrusion production process for a high-barrier heat shrinkable cover film, aiming to solve the above-mentioned problem.

[0005] The present invention is achieved by a three-bubble method nine-layer co-extrusion production process of a high-barrier heat shrinkable cover film, comprising the following steps: Weigh the raw materials of each layer; The raw materials of each layer are melted by the screw and then extruded into a nine-layer circular extruder, and multiple layers are stacked to form a film blank; The film blank is rapidly cooled and formed with 5-20℃ cooling water, and then enters the infrared heating system to be heated to the blowing temperature of 80-90℃; The film blank is stretched longitudinally, then filled with compressed air for transverse expansion, and then enters the infrared heating cylinder for shaping treatment, and the air ring is cooled to obtain a film; The film is subjected to corona treatment and ultraviolet light irradiation treatment by a corona machine, and is rolled up to obtain a high-barrier heat-shrinkable cover film.

[0006] Preferably, the high-barrier heat shrinkable covering film is a nine-layer structure produced using a triple-bubble process, including a surface layer, a structural layer, a barrier layer, a heat-sealing layer, and an adhesive layer arranged between the surface layer, the structural layer, the barrier layer, and the heat-sealing layer. The barrier layer includes an intermediate layer and protective layers arranged on both sides of the intermediate layer.

[0007] Preferably, the longitudinal stretching ratio is 2-4 times, and the transverse blowing ratio is 3-4 times.

[0008] Preferably, the surface layer comprises metallocene linear low-density polyethylene and / or polyamide, the structural layer comprises polyethylene, the heat-sealing layer comprises low-density polyethylene and / or linear low-density polyethylene, the intermediate layer of the barrier layer comprises ethylene vinyl alcohol copolymer and UV-curable oligomer in a mass ratio of 5-10:1, and the protective layer of the barrier layer is polyamide 6. By adding UV-curable oligomer, a dense barrier layer can be formed after curing, which has water vapor and oxygen barrier effects and improves mechanical properties.

[0009] Preferably, the adhesive layer comprises the following raw materials in parts by weight: 50-60 parts of maleic anhydride modified polyethylene, 20-30 parts of vinyl acetate-ethylene copolymer, 1-2 parts of nano titanium dioxide, 1-3 parts of modified polyethylene glycol, 1-2 parts of modified lignin and 2-4 parts of modified aerogel.

[0010] Preferably, the preparation method of the modified polyethylene glycol is as follows: the preparation method of the modified polyethylene glycol is as follows: by weight, 10-12 parts of polyethylene glycol are added to 50-60 parts of N, N-dimethylformamide, 1.5-3.5 parts of 3-amino-1,2-propylene glycol and 2-4 parts of diethylamine are added, the temperature is raised to 80-100°C and stirred for 30-40 minutes, then 10-20 parts of succinic anhydride are added and stirred for 30-40 minutes, and then extracted with cyclohexane, the obtained product is mixed with dichloride in a mass ratio of 5-8:1, stirred for 20-40 minutes, and then distilled under reduced pressure to obtain modified polyethylene glycol, and the reaction activity of polyethylene glycol is enhanced by grafting amino groups on the ends of polyethylene glycol, and then succinic anhydride is added for cross-linking modification, so that the modified polyethylene glycol can react with other components to form a macromolecular network structure, improve the interface performance of the adhesive layer, and tightly combine with other layers to improve the mechanical properties of the heat shrinkable film.

[0011] Preferably, the preparation method of the modified lignin is as follows: take 6-10 parts of lignin by weight, add 10-15 times the weight of pure water, then disperse for 20-30 minutes, heat to 50-80°C, add 0.3-0.5 parts of hydrogen peroxide and react for 1-3 hours, finally add 50-60 parts of gluconic acid solution and mix, heat to 100-120°C, react for 2-4 hours to obtain modified lignin; first oxidize the lignin with hydrogen peroxide to increase its reaction activity, then add gluconic acid solution for esterification reaction to improve the mechanical properties of lignin, avoid deformation, breakage or delamination of the adhesive layer under the action of external force, and improve the barrier properties and mechanical formation of the heat shrinkable film.

[0012] Preferably, the preparation method of the modified aerogel is as follows: by weight, 4-6 parts of nano-silica aerogel powder are added to 30-40 parts of silane coupling agent solution, stirred for 30-50 minutes, aged for 2 days, and then placed in an oven at 70-80°C for drying for 2-4 hours to obtain the modified aerogel. The surface energy of the silica aerogel powder is reduced by modification, the agglomeration phenomenon in the organism is reduced, the aerogel is fully dispersed, the bonding ability with the system is improved, a network structure is formed, and the stability, mechanical properties and barrier properties of the heat shrinkable film are improved.

[0013] Preferably, the silane coupling agent solution is prepared by mixing the silane coupling agent with ethanol in a volume ratio of 1:40-50.

[0014] Compared with the prior art, the embodiments of the present application have the following beneficial effects: The high-barrier heat shrinkable film prepared by the three-bubble nine-layer co-extrusion production process of the high-barrier heat shrinkable cover film provided by the present invention has high barrier properties to air and water vapor and good mechanical properties. By adding modified lignin, modified polyethylene glycol and modified aerogel to the adhesive layer, the three work synergistically to improve the barrier properties and mechanical properties of the heat shrinkable film. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of a three-bubble method nine-layer co-extrusion production process of a high-barrier heat shrinkable cover film provided by the present invention. DETAILED DESCRIPTION

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of this application; the terms used in the specification of the application herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0017] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0018] Example 1 The embodiment of the present invention provides a three-bubble method nine-layer co-extrusion production process of a high-barrier heat shrinkable cover film, such as Figure 1 As shown, the following steps are included: Weigh the raw materials of each layer; The raw materials of each layer are melted by the screw and then extruded into a nine-layer circular extruder, and multiple layers are stacked to form a film blank; The film blank is rapidly cooled and formed with 5℃ cooling water, and then enters the infrared heating system to be heated to the blowing temperature of 80℃; The film blank is stretched longitudinally, then filled with compressed air for transverse expansion, and then enters the infrared heating cylinder for shaping treatment, and the air ring is cooled to obtain a film; The film is subjected to corona treatment and ultraviolet light irradiation treatment by a corona machine, and is rolled up to obtain a high-barrier heat-shrinkable cover film.

[0019] Specifically, the high-barrier heat shrinkable covering film is a nine-layer structure produced using a triple-bubble process, including a surface layer, a structural layer, a barrier layer, a heat-sealing layer, and an adhesive layer arranged between the surface layer, the structural layer, the barrier layer, and the heat-sealing layer. The barrier layer includes an intermediate layer and protective layers arranged on both sides of the intermediate layer.

[0020] Wherein, the longitudinal stretching ratio is 2 times, and the transverse blowing ratio is 3 times.

[0021] In this embodiment, the surface layer includes metallocene linear low-density polyethylene and / or polyamide, the structural layer includes polyethylene, the heat-sealing layer includes low-density polyethylene and / or linear low-density polyethylene, the intermediate layer of the barrier layer includes ethylene vinyl alcohol copolymer and UV-curable oligomer in a mass ratio of 5:1, and the protective layer of the barrier layer is polyamide 6.

[0022] Specifically, the adhesive layer includes the following raw materials in parts by weight: 50 parts of maleic anhydride modified polyethylene, 20 parts of vinyl acetate ethylene copolymer, 1 part of nano titanium dioxide, 1 part of modified polyethylene glycol, 1 part of modified lignin and 2 parts of modified aerogel.

[0023] Furthermore, the preparation method of the modified polyethylene glycol is as follows: the preparation method of the modified polyethylene glycol is as follows: by weight, 10 parts of polyethylene glycol are added to 50 parts of N,N-dimethylformamide, 1.5 parts of 3-amino-1,2-propylene glycol and 2 parts of diethylamine are added, the temperature is raised to 80°C and stirred for 30 minutes, then 10 parts of succinic anhydride are added and stirring is continued for 30 minutes, and then extracted with cyclohexane, and the obtained product is mixed with dichlorothionyl in a mass ratio of 5:1, stirred for 20 minutes, and then distilled under reduced pressure to obtain modified polyethylene glycol.

[0024] In a specific implementation, the preparation method of the modified lignin is as follows: take 6 parts of lignin by weight, add 10 times the weight of pure water, then disperse for 20 minutes, heat to 50°C, add 0.3 parts of hydrogen peroxide and react for 1 hour, finally add 50 parts of gluconic acid solution and mix, heat to 100°C, react for 2 hours, and obtain modified lignin.

[0025] In this embodiment, the preparation method of the modified aerogel is as follows: by weight, 4 parts of nano-silica aerogel powder are added to 30 parts of silane coupling agent solution, stirred for 30 minutes, aged for 2 days, and then placed in an oven at 70° C. and dried for 2 hours to obtain the modified aerogel, wherein the silane coupling agent solution is prepared by mixing silane coupling agent and ethanol in a volume ratio of 1:40.

[0026] Example 2 The embodiment of the present invention provides a three-bubble method nine-layer co-extrusion production process of a high-barrier heat shrinkable cover film, such as Figure 1 As shown, the following steps are included: Weigh the raw materials of each layer; The raw materials of each layer are melted by the screw and then extruded into a nine-layer circular extruder, and multiple layers are stacked to form a film blank; The film blank is rapidly cooled and formed with 5℃ cooling water, and then enters the infrared heating system to be heated to the blowing temperature of 80℃; The film blank is stretched longitudinally, then filled with compressed air for transverse expansion, and then enters the infrared heating cylinder for shaping treatment, and the air ring is cooled to obtain a film; The film is subjected to corona treatment and ultraviolet light irradiation treatment by a corona machine, and is rolled up to obtain a high-barrier heat-shrinkable cover film.

[0027] Specifically, the high-barrier heat shrinkable covering film is a nine-layer structure produced using a triple-bubble process, including a surface layer, a structural layer, a barrier layer, a heat-sealing layer, and an adhesive layer arranged between the surface layer, the structural layer, the barrier layer, and the heat-sealing layer. The barrier layer includes an intermediate layer and protective layers arranged on both sides of the intermediate layer.

[0028] Wherein, the longitudinal stretching ratio is 2 times, and the transverse blowing ratio is 3 times.

[0029] In this embodiment, the surface layer includes metallocene linear low-density polyethylene and / or polyamide, the structural layer includes polyethylene, the heat-sealing layer includes low-density polyethylene and / or linear low-density polyethylene, the intermediate layer of the barrier layer includes ethylene vinyl alcohol copolymer and UV-curable oligomer in a mass ratio of 5:1, and the protective layer of the barrier layer is polyamide 6.

[0030] Specifically, the adhesive layer includes the following raw materials in parts by weight: 52 parts of maleic anhydride modified polyethylene, 23 parts of vinyl acetate ethylene copolymer, 1.2 parts of nano titanium dioxide, 1.5 parts of modified polyethylene glycol, 1.3 parts of modified lignin and 2.5 parts of modified aerogel.

[0031] Furthermore, the preparation method of the modified polyethylene glycol is as follows: the preparation method of the modified polyethylene glycol is as follows: by weight, 10 parts of polyethylene glycol are added to 50 parts of N,N-dimethylformamide, 1.5 parts of 3-amino-1,2-propylene glycol and 2 parts of diethylamine are added, the temperature is raised to 80°C and stirred for 30 minutes, then 10 parts of succinic anhydride are added and stirred for 30 minutes, extracted with cyclohexane, the obtained product is mixed with dichlorothionyl at a mass ratio of 5:1, stirred for 20 minutes, and then distilled under reduced pressure to obtain the modified polyethylene glycol.

[0032] In a specific implementation, the preparation method of the modified lignin is as follows: take 6 parts of lignin by weight, add 10 times the weight of pure water, then disperse for 20 minutes, heat to 50°C, add 0.3 parts of hydrogen peroxide and react for 1 hour, finally add 50 parts of gluconic acid solution and mix, heat to 100°C, react for 2 hours, and obtain modified lignin.

[0033] In this embodiment, the preparation method of the modified aerogel is as follows: by weight, 4 parts of nano-silica aerogel powder are added to 30 parts of silane coupling agent solution, stirred for 30 minutes, aged for 2 days, and then placed in an oven at 70° C. and dried for 2 hours to obtain the modified aerogel, wherein the silane coupling agent solution is prepared by mixing silane coupling agent and ethanol in a volume ratio of 1:40.

[0034] Example 3 The embodiment of the present invention provides a three-bubble method nine-layer co-extrusion production process of a high-barrier heat shrinkable cover film, such as Figure 1 As shown, the following steps are included: Weigh the raw materials of each layer; The raw materials of each layer are melted by the screw and then extruded into a nine-layer circular extruder, and multiple layers are stacked to form a film blank; The film blank is rapidly cooled and formed with 15℃ cooling water, and then enters the infrared heating system to be heated to the blowing temperature of 85℃; The film blank is stretched longitudinally, then filled with compressed air for transverse expansion, and then enters the infrared heating cylinder for shaping treatment, and the air ring is cooled to obtain a film; The film is subjected to corona treatment and ultraviolet light irradiation treatment by a corona machine, and is rolled up to obtain a high-barrier heat-shrinkable cover film.

[0035] Specifically, the high-barrier heat shrinkable covering film is a nine-layer structure produced using a triple-bubble process, including a surface layer, a structural layer, a barrier layer, a heat-sealing layer, and an adhesive layer arranged between the surface layer, the structural layer, the barrier layer, and the heat-sealing layer. The barrier layer includes an intermediate layer and protective layers arranged on both sides of the intermediate layer.

[0036] Among them, the longitudinal stretching ratio is 3 times, and the transverse blowing ratio is 3.5 times.

[0037] In this embodiment, the surface layer includes metallocene linear low-density polyethylene and / or polyamide, the structural layer includes polyethylene, the heat-sealing layer includes low-density polyethylene and / or linear low-density polyethylene, the intermediate layer of the barrier layer includes ethylene vinyl alcohol copolymer and UV-curable oligomer in a mass ratio of 7:1, and the protective layer of the barrier layer is polyamide 6.

[0038] Specifically, the adhesive layer includes the following raw materials in parts by weight: 55 parts of maleic anhydride modified polyethylene, 25 parts of vinyl acetate-ethylene copolymer, 1.5 parts of nano titanium dioxide, 2 parts of modified polyethylene glycol, 1.5 parts of modified lignin and 3 parts of modified aerogel.

[0039] Furthermore, the preparation method of the modified polyethylene glycol is as follows: the preparation method of the modified polyethylene glycol is as follows: by weight, 11 parts of polyethylene glycol are added to 55 parts of N,N-dimethylformamide, 2.5 parts of 3-amino-1,2-propylene glycol and 3 parts of diethylamine are added, the temperature is raised to 90°C and stirred for 35 minutes, then 15 parts of succinic anhydride are added and stirring is continued for 35 minutes, and then extracted with cyclohexane, and the obtained product is mixed with dichlorothionyl at a mass ratio of 6.5:1, stirred for 30 minutes, and then distilled under reduced pressure to obtain the modified polyethylene glycol.

[0040] In a specific implementation, the preparation method of the modified lignin is as follows: take 8 parts of lignin by weight, add 12 times the weight of pure water, then disperse for 25 minutes, heat to 65°C, add 0.4 parts of hydrogen peroxide and react for 2 hours, finally add 55 parts of gluconic acid solution and mix, heat to 120°C, react for 3 hours, and obtain modified lignin.

[0041] In this embodiment, the preparation method of the modified aerogel is as follows: by weight, 5 parts of nano-silica aerogel powder are added to 35 parts of silane coupling agent solution, stirred for 40 minutes, aged for 2 days, and then placed in an oven at 75° C. and dried for 3 hours to obtain the modified aerogel, wherein the silane coupling agent solution is prepared by mixing silane coupling agent and ethanol in a volume ratio of 1:45.

[0042] Example 4 The embodiment of the present invention provides a three-bubble method nine-layer co-extrusion production process of a high-barrier heat shrinkable cover film, such as Figure 1 As shown, the following steps are included: Weigh the raw materials of each layer; The raw materials of each layer are melted by the screw and then extruded into a nine-layer circular extruder, and multiple layers are stacked to form a film blank; The film blank is rapidly cooled and formed with 20℃ cooling water, and then enters the infrared heating system to be heated to the blowing temperature of 90℃; The film blank is stretched longitudinally, then filled with compressed air for transverse expansion, and then enters the infrared heating cylinder for shaping treatment, and the air ring is cooled to obtain a film; The film is subjected to corona treatment and ultraviolet light irradiation treatment by a corona machine, and is rolled up to obtain a high-barrier heat-shrinkable cover film.

[0043] Specifically, the high-barrier heat shrinkable covering film is a nine-layer structure produced using a triple-bubble process, including a surface layer, a structural layer, a barrier layer, a heat-sealing layer, and an adhesive layer arranged between the surface layer, the structural layer, the barrier layer, and the heat-sealing layer. The barrier layer includes an intermediate layer and protective layers arranged on both sides of the intermediate layer.

[0044] Among them, the longitudinal stretching ratio is 4 times, and the transverse blowing ratio is 4 times.

[0045] In this embodiment, the surface layer includes metallocene linear low-density polyethylene and / or polyamide, the structural layer includes polyethylene, the heat-sealing layer includes low-density polyethylene and / or linear low-density polyethylene, the intermediate layer of the barrier layer includes ethylene vinyl alcohol copolymer and UV-curable oligomer in a mass ratio of 10:1, and the protective layer of the barrier layer is polyamide 6.

[0046] Specifically, the adhesive layer includes the following raw materials in parts by weight: 58 parts of maleic anhydride modified polyethylene, 27 parts of vinyl acetate ethylene copolymer, 1.8 parts of nano titanium dioxide, 2.5 parts of modified polyethylene glycol, 1.7 parts of modified lignin and 3.5 parts of modified aerogel.

[0047] Furthermore, the preparation method of the modified polyethylene glycol is as follows: the preparation method of the modified polyethylene glycol is as follows: by weight, 12 parts of polyethylene glycol are added to 60 parts of N,N-dimethylformamide, 3.5 parts of 3-amino-1,2-propylene glycol and 4 parts of diethylamine are added, the temperature is raised to 100°C and stirred for 40 minutes, and then 20 parts of succinic anhydride are added and stirred for 40 minutes, and then extracted with cyclohexane, and the obtained product is mixed with dichlorothionyl in a mass ratio of 8:1, stirred for 40 minutes, and then distilled under reduced pressure to obtain modified polyethylene glycol.

[0048] In a specific implementation, the preparation method of the modified lignin is as follows: take 10 parts of lignin by weight, add 15 times the weight of pure water, then disperse for 30 minutes, heat to 80°C, add 0.5 parts of hydrogen peroxide and react for 3 hours, finally add 60 parts of gluconic acid solution and mix, heat to 120°C, react for 4 hours, and obtain modified lignin.

[0049] In this embodiment, the preparation method of the modified aerogel is as follows: by weight, 6 parts of nano-silica aerogel powder are added to 40 parts of silane coupling agent solution, stirred for 50 minutes, aged for 2 days, and then placed in an oven at 80° C. and dried for 4 hours to obtain the modified aerogel, wherein the silane coupling agent solution is prepared by mixing silane coupling agent and ethanol in a volume ratio of 1:50.

[0050] Example 5 The embodiment of the present invention provides a three-bubble method nine-layer co-extrusion production process of a high-barrier heat shrinkable cover film, such as Figure 1 As shown, the following steps are included: Weigh the raw materials of each layer; The raw materials of each layer are melted by the screw and then extruded into a nine-layer circular extruder, and multiple layers are stacked to form a film blank; The film blank is rapidly cooled and formed with 20℃ cooling water, and then enters the infrared heating system to be heated to the blowing temperature of 90℃; The film blank is stretched longitudinally, then filled with compressed air for transverse expansion, and then enters the infrared heating cylinder for shaping treatment, and the air ring is cooled to obtain a film; The film is subjected to corona treatment and ultraviolet light irradiation treatment by a corona machine, and is rolled up to obtain a high-barrier heat-shrinkable cover film.

[0051] Specifically, the high-barrier heat shrinkable covering film is a nine-layer structure produced using a triple-bubble process, including a surface layer, a structural layer, a barrier layer, a heat-sealing layer, and an adhesive layer arranged between the surface layer, the structural layer, the barrier layer, and the heat-sealing layer. The barrier layer includes an intermediate layer and protective layers arranged on both sides of the intermediate layer.

[0052] Among them, the longitudinal stretching ratio is 4 times, and the transverse blowing ratio is 4 times.

[0053] In this embodiment, the surface layer includes metallocene linear low-density polyethylene and / or polyamide, the structural layer includes polyethylene, the heat-sealing layer includes low-density polyethylene and / or linear low-density polyethylene, the intermediate layer of the barrier layer includes ethylene vinyl alcohol copolymer and UV-curable oligomer in a mass ratio of 10:1, and the protective layer of the barrier layer is polyamide 6.

[0054] Specifically, the adhesive layer includes the following raw materials in parts by weight: 60 parts of maleic anhydride modified polyethylene, 30 parts of vinyl acetate ethylene copolymer, 2 parts of nano titanium dioxide, 3 parts of modified polyethylene glycol, 2 parts of modified lignin and 4 parts of modified aerogel.

[0055] Furthermore, the preparation method of the modified polyethylene glycol is as follows: the preparation method of the modified polyethylene glycol is as follows: by weight, 12 parts of polyethylene glycol are added to 60 parts of N,N-dimethylformamide, 3.5 parts of 3-amino-1,2-propylene glycol and 4 parts of diethylamine are added, the temperature is raised to 100°C and stirred for 40 minutes, and then 20 parts of succinic anhydride are added and stirred for 40 minutes, and then extracted with cyclohexane, and the obtained product is mixed with dichlorothionyl in a mass ratio of 8:1, stirred for 40 minutes, and then distilled under reduced pressure to obtain modified polyethylene glycol.

[0056] In a specific implementation, the preparation method of the modified lignin is as follows: take 10 parts of lignin by weight, add 15 times the weight of pure water, then disperse for 30 minutes, heat to 80°C, add 0.5 parts of hydrogen peroxide and react for 3 hours, finally add 60 parts of gluconic acid solution and mix, heat to 120°C, react for 4 hours, and obtain modified lignin.

[0057] In this embodiment, the preparation method of the modified aerogel is as follows: by weight, 6 parts of nano-silica aerogel powder are added to 40 parts of silane coupling agent solution, stirred for 50 minutes, aged for 2 days, and then placed in an oven at 80° C. and dried for 4 hours to obtain the modified aerogel, wherein the silane coupling agent solution is prepared by mixing silane coupling agent and ethanol in a volume ratio of 1:50.

[0058] Comparative Example 1 Compared with Example 3, the modified polyethylene glycol in the adhesive is replaced by ordinary polyethylene glycol.

[0059] Comparative Example 2 Compared with Example 3, the modified lignin in the adhesive is replaced by ordinary lignin.

[0060] Comparative Example 3 Compared with Example 3, the modified aerogel in the adhesive is replaced by ordinary aerogel.

[0061] Comparative Example 4 Compared with Example 3, the modified polyethylene glycol in the adhesive is replaced by ordinary polyethylene glycol, the modified lignin is replaced by ordinary lignin, and the modified aerogel is replaced by ordinary aerogel.

[0062] Comparative Example 5 A commercially available heat shrinkable cover film.

[0063] test The tensile strength, oxygen permeability and moisture permeability of the heat shrinkable cover films of Examples 1-5 and Comparative Examples 1-5 were tested. The results are shown in Table 1: Table 1 Test results of tensile strength, oxygen permeability and moisture permeability of heat shrinkable cover film Group Longitudinal tensile strength (MPa) Transverse tensile strength (MPa) Oxygen permeability (cc / m2·day) Moisture permeability (gg / m2·day) Example 1 57 52 1.214 1.018 Example 2 58 54 1.186 0.995 Example 3 60 55 1.115 0.972 Example 4 59 54 1.165 0.998 Example 5 58 53 1.198 1.012 Comparative Example 1 36 31 2.712 2.324 Comparative Example 2 34 32 2.786 2.342 Comparative Example 3 33 29 2.815 2.386 Comparative Example 4 25 21 3.516 2.845 Comparative Example 5 23 20 3.564 2.861 From the above results, it can be seen that the heat shrinkable cover film prepared by the present invention has high barrier properties and good mechanical properties, especially by adding modified lignin, modified polyethylene glycol and modified aerogel to the adhesive layer, the three work together to improve the barrier properties and mechanical properties of the heat shrinkable film.

[0064] It should be noted that, for the above-mentioned embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the described order of actions, because according to the present invention, some steps may be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present invention.

[0065] In the several embodiments provided in the present application, it should be understood that the disclosed device can be implemented in other ways. For example, the device embodiments described above are only schematic, such as the division of the above-mentioned units, which is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or communication connection shown or discussed can be through some interfaces, and the indirect coupling or communication connection between devices or units can be in the form of telecommunication or other forms.

[0066] The units described above as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on these embodiments, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field can still combine, add, delete or make other adjustments to the features in the various embodiments of the present invention according to the circumstances without conflict, without making creative work, so as to obtain different other technical solutions that do not deviate from the concept of the present invention in essence, and these technical solutions also belong to the scope of protection of the present invention.

Claims

1. A three-bubble nine-layer co-extrusion production process for a high-barrier heat-shrinkable cover film, characterized in that: The steps include: Weigh the raw materials of each layer; The raw materials of each layer are melted by the screw and then extruded into a nine-layer circular extruder, and multiple layers are stacked to form a film blank; The film blank is rapidly cooled and formed with 5-20℃ cooling water, and then enters the infrared heating system to be heated to the blowing temperature of 80-90℃; The film blank is stretched longitudinally, then filled with compressed air for transverse expansion, and then enters the infrared heating cylinder for shaping treatment, and the air ring is cooled to obtain a film; The film is subjected to corona treatment and ultraviolet light irradiation treatment by a corona machine, and is rolled up to obtain a high-barrier heat-shrinkable cover film.

2. The three-bubble nine-layer co-extrusion production process of the high-barrier heat-shrinkable cover film according to claim 1, characterized in that: The high-barrier heat shrinkable cover film is a nine-layer structure produced using a triple-bubble process, including a surface layer, a structural layer, a barrier layer, a heat-sealing layer, and an adhesive layer disposed between the surface layer, the structural layer, the barrier layer, and the heat-sealing layer. The barrier layer includes an intermediate layer and protective layers disposed on both sides of the intermediate layer.

3. The three-bubble nine-layer co-extrusion production process of the high-barrier heat shrinkable cover film according to claim 1, characterized in that: The longitudinal stretching ratio is 2-4 times, and the transverse blowing ratio is 3-4 times.

4. The three-bubble nine-layer co-extrusion production process of the high-barrier heat shrinkable cover film according to claim 1, characterized in that: The surface layer includes metallocene linear low-density polyethylene and / or polyamide, the structural layer includes polyethylene, the heat-sealing layer includes low-density polyethylene and / or linear low-density polyethylene, the middle layer of the barrier layer includes ethylene vinyl alcohol copolymer and ultraviolet light-cured oligomer in a mass ratio of 5-10:1, and the protective layer of the barrier layer is polyamide 6.

5. The three-bubble nine-layer co-extrusion production process of the high-barrier heat shrinkable cover film according to claim 2, characterized in that: The adhesive layer comprises the following raw materials in parts by weight: 50-60 parts of maleic anhydride modified polyethylene, 20-30 parts of vinyl acetate-ethylene copolymer, 1-2 parts of nano titanium dioxide, 1-3 parts of modified polyethylene glycol, 1-2 parts of modified lignin and 2-4 parts of modified aerogel.

6. The three-bubble nine-layer co-extrusion production process of the high-barrier heat shrinkable cover film according to claim 5, characterized in that: The preparation method of the modified polyethylene glycol is as follows: the preparation method of the modified polyethylene glycol is as follows: by weight, 10-12 parts of polyethylene glycol are added to 50-60 parts of N, N-dimethylformamide, 1.5-3.5 parts of 3-amino-1,2-propylene glycol and 2-4 parts of diethylamine are added, the temperature is raised to 80-100°C and stirred for 30-40 minutes, then 10-20 parts of succinic anhydride are added and stirred for 30-40 minutes, and then extracted with cyclohexane, the obtained product is mixed with dichlorothionyl at a mass ratio of 5-8:1, stirred for 20-40 minutes, and then distilled under reduced pressure to obtain the modified polyethylene glycol.

7. The three-bubble nine-layer co-extrusion production process of the high-barrier heat-shrinkable cover film according to claim 5, characterized in that: The preparation method of the modified lignin is as follows: 6-10 parts of lignin are taken by weight, 10-15 times the weight of pure water is added, and then dispersed for 20-30 minutes, heated to 50-80° C., 0.3-0.5 parts of hydrogen peroxide are added to react for 1-3 hours, and finally 50-60 parts of gluconic acid solution are added to mix, heated to 100-120° C., and reacted for 2-4 hours to obtain modified lignin.

8. The three-bubble nine-layer co-extrusion production process of the high-barrier heat-shrinkable cover film according to claim 5, characterized in that: The preparation method of the modified aerogel is as follows: by weight, 4-6 parts of nano-silicon dioxide aerogel powder are added to 30-40 parts of silane coupling agent solution, stirred for 30-50 minutes, aged for 2 days, and then placed in an oven at 70-80° C. for drying for 2-4 hours to obtain the modified aerogel.

9. The three-bubble nine-layer co-extrusion production process of the high-barrier heat-shrinkable cover film according to claim 8, characterized in that: The silane coupling agent solution is prepared by mixing the silane coupling agent with ethanol in a volume ratio of 1:40-50.

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