Multi-layer co-extrusion preparation method of high-barrier polymeric membrane

Abstract

The invention belongs to the technical field of polymeric membrane preparation, and discloses a multi-layer co-extrusion preparation method of a high-barrier polymeric membrane, and the high-barrier polymeric membrane comprises a heat sealing layer, a bonding layer, a barrier layer, a bonding layer and an outer layer which are sequentially distributed from inside to outside; the multi-layer structure of the film is reasonably designed, the ethylene-acrylic acid copolymer is selected as the raw material of the bonding layer, the ethylene-acrylic acid copolymer has good compatibility with the polyethylene material of the heat sealing layer, the ethylene-vinyl alcohol copolymer of the blocking layer and the high-density polyethylene of the outer layer, the bonding force between the film layers can be effectively improved, and the bonding force between the film layers is improved. The layering and stripping phenomena of the finished film are avoided, and the stability of the barrier property is guaranteed.

Description

Technical Field

[0001] This application relates to the field of polymer membrane preparation technology, and more specifically, to a method for preparing a high-barrier polymer membrane by multilayer co-extrusion. Background Technology

[0002] Due to their excellent properties such as being lightweight, flexible, and easy to process, polymer membrane materials are widely used in various fields such as food packaging, pharmaceutical packaging, and electronic component encapsulation. In these application scenarios, especially in the food and pharmaceutical packaging fields, stringent requirements are placed on the barrier performance of polymer membranes. They need to effectively block gases such as oxygen, water vapor, and carbon dioxide, as well as organic solvent vapors, to prevent the contents of the packaged items from oxidizing and deteriorating, becoming damp and moldy, or losing components, thereby extending the product's shelf life and ensuring product quality.

[0003] Multilayer co-extrusion technology is one of the mainstream technologies for preparing high-barrier polymer films. By simultaneously extruding and compounding multiple polymer materials with different properties, it can fully utilize the advantages of each layer to achieve high barrier performance that cannot be achieved by a single material. However, existing multilayer co-extrusion preparation methods still have many shortcomings in practical applications: On the one hand, the compatibility of different polymer materials varies greatly, resulting in weak interlayer bonding and problems such as delamination and peeling of the film products, which seriously affect the barrier performance and service life; on the other hand, improper control of process parameters during the preparation process can easily lead to poor film thickness uniformity, internal bubbles or crystalline defects, further reducing the barrier effect; in addition, some preparation methods excessively increase the film thickness or use expensive special materials in pursuit of barrier performance, resulting in a significant increase in production costs, which is not conducive to large-scale production.

[0004] Therefore, developing a multilayer co-extrusion method for preparing high-barrier polymer films with tight interlayer bonding, excellent barrier properties, good thickness uniformity, and controllable production costs has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This application provides a method for preparing a high-barrier polymer film through multilayer co-extrusion, comprising a heat-sealing layer, an adhesive layer, a barrier layer, and an outer layer distributed sequentially from the inside to the outside. The preparation method includes the following steps: S1 Raw Material Pretreatment: Select heat-sealing layer raw material, adhesive layer raw material, barrier layer raw material and outer layer raw material respectively, and dry each raw material. Among them, the heat-sealing layer raw material is a mixture of linear low-density polyethylene and metallocene polyethylene, the adhesive layer raw material is ethylene-acrylic acid copolymer, the barrier layer raw material is a composite modified material of ethylene-vinyl alcohol copolymer and montmorillonite, and the outer layer raw material is high-density polyethylene. S2 Raw Material Melting and Plasticizing: The pretreated raw materials of each layer are added to the corresponding extruders for melting and plasticizing. The barrel temperature and screw speed of each extruder are controlled to obtain the molten material of each layer. S3 Multilayer Co-extrusion Composite: The molten material of each layer is conveyed to the co-extrusion die head, and the layers are composited through the flow channels in the co-extrusion die head to form a multilayer composite melt; S4 Cooling and Shaping: After the multi-layer composite melt is extruded from the co-extrusion die, it is cooled and shaped using cooling rollers to obtain a preliminary multi-layer film preform; S5 stretching orientation: The cooled and shaped film preform is subjected to bidirectional stretching, and longitudinal stretching and transverse stretching are performed in sequence. S6 Heat Setting and Winding: The stretched and oriented preform is heat-set, then trimmed, drawn, and wound to obtain a high-barrier polymer film product.

[0006] Furthermore, in S1, the mass ratio of linear low-density polyethylene to metallocene polyethylene in the heat-sealing layer raw material is 7:3 to 8:2, and the montmorillonite in the barrier layer raw material is organomontmorillonite modified with a silane coupling agent, and the amount of montmorillonite added is 5% to 10% of the mass of the ethylene-vinyl alcohol copolymer.

[0007] Furthermore, in S1, the drying conditions for each raw material are as follows: the heat-sealing layer material and the outer layer material are dried at 80~90℃ for 2~3 hours, the adhesive layer material is dried at 70~80℃ for 1.5~2.5 hours, and the barrier layer material is dried at 100~110℃ for 3~4 hours.

[0008] Furthermore, in S2, the extruder includes a first extruder, a second extruder, a third extruder, and a fourth extruder, which respectively convey the heat-sealing layer, the adhesive layer, the barrier layer, and the outer layer molten material. The barrel temperature of each extruder is controlled as follows: 160~180℃ for the first extruder, 170~190℃ for the second extruder, 180~200℃ for the third extruder, and 165~185℃ for the fourth extruder. The screw speed of each extruder is 40~60 r / min.

[0009] Furthermore, in S3, the temperature of the co-extrusion die is controlled at 190~210℃, the flow rate ratio of each layer of molten material in the co-extrusion die is consistent with the thickness ratio of each layer of the finished film, and the thickness ratio of the heat-sealing layer, adhesive layer, barrier layer, adhesive layer and outer layer in the finished film is 3:1:2:1:3.

[0010] Furthermore, in S4, the temperature of the cooling roller is 20~30℃, the bonding pressure between the film blank and the cooling roller is 0.3~0.5MPa, and the cooling time is 5~10s.

[0011] Furthermore, in S5, the longitudinal stretching temperature is 80~90℃, the stretching ratio is 2.5~3.5 times, and the stretching speed is 5~8m / min; the transverse stretching temperature is 90~100℃, the stretching ratio is 3~4 times, and the stretching speed is 4~7m / min.

[0012] Furthermore, in S6, the temperature of the heat setting treatment is 110~130℃, the treatment time is 10~15s, the winding speed is 3~6m / min, and the winding tension is 50~80N.

[0013] In summary, this application includes the following beneficial technical effects: 1. This invention, through the rational design of the multi-layer structure of the membrane, selects ethylene-acrylic acid copolymer as the adhesive layer material, which has good compatibility with the polyethylene material of the heat-sealing layer, the ethylene-vinyl alcohol copolymer of the barrier layer and the high-density polyethylene of the outer layer, which can effectively improve the bonding force between the membrane layers, avoid delamination and peeling of the finished membrane, and ensure the stability of the barrier performance.

[0014] 2. This invention performs targeted pretreatment on the raw materials of each layer, especially the barrier layer material, which is composited with modified montmorillonite and ethylene-vinyl alcohol copolymer. It also precisely controls the temperature, speed and process parameters of each extruder and the co-extrusion die, which can ensure that the plasticizing effect of each layer of melt is uniform and consistent, improve the molding stability of the multilayer composite melt, ensure the thickness uniformity of the finished film and reduce internal defects.

[0015] 3. This invention uses biaxial stretching and orientation treatment to arrange the polymer chains in the membrane in an orderly manner, which further improves the mechanical and barrier properties of the membrane. At the same time, a reasonable heat setting process is used to eliminate the internal stress generated during stretching, which improves the dimensional stability of the membrane. The various process parameters work together to ensure high barrier performance without excessively increasing the membrane thickness, thereby reducing raw material costs and making it suitable for large-scale production. Attached Figure Description

[0016] Figure 1 This is a flowchart of the polymer membrane preparation method of this application; Figure 2 This is a schematic diagram of the polymer membrane structure composition of this application. Detailed Implementation

[0017] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0018] In the description of this application, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0019] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. Example 1

[0020] This application discloses a method for preparing a high-barrier polymer film through multilayer co-extrusion. Please refer to [link to relevant documentation]. Figure 1 and Figure 2 It includes, from the inside out, a heat-sealing layer, an adhesive layer, a barrier layer, and an outer layer, and the preparation method includes the following steps: S1 Raw Material Pretreatment: Linear low-density polyethylene and metallocene polyethylene were mixed at a mass ratio of 7:3 as the heat-sealing layer material, ethylene-acrylic acid copolymer was selected as the adhesive layer material, ethylene-vinyl alcohol copolymer and organomontmorillonite modified with silane coupling agent (added at 5% of the mass of ethylene-vinyl alcohol copolymer) were selected as the barrier layer material, and high-density polyethylene was selected as the outer layer material. The heat-sealing layer material and the outer layer material were dried at 80℃ for 3 hours, the adhesive layer material was dried at 70℃ for 2.5 hours, and the barrier layer material was dried at 100℃ for 4 hours.

[0021] S2 Raw Material Melting and Plasticizing: The pretreated raw materials for each layer are added to the corresponding extruders. The barrel temperature of the first extruder (heat-sealing layer) is controlled at 160℃, the barrel temperature of the second extruder (adhesive layer) is controlled at 170℃, the barrel temperature of the third extruder (barrier layer) is controlled at 180℃, and the barrel temperature of the fourth extruder (outer layer) is controlled at 165℃. The screw speed of each extruder is 40r / min. Melting and plasticizing are carried out to obtain the molten material of each layer.

[0022] S3 Multilayer Co-extrusion Composite: The molten material of each layer is conveyed to a co-extrusion die at a temperature of 190℃, and the flow rate ratio of each layer of molten material is controlled at 3:1:2:1:3 (corresponding to heat-sealing layer, adhesive layer, barrier layer, adhesive layer, and outer layer). The layers are composited through the flow channels in the co-extrusion die to form a multilayer composite melt.

[0023] S4 Cooling and Shaping: After the multilayer composite melt is extruded from the co-extrusion die, it is cooled and shaped using a cooling roller at a temperature of 20℃. The bonding pressure between the film blank and the cooling roller is controlled at 0.3MPa, and the cooling time is 10s, to obtain a preliminary multilayer film blank.

[0024] S5 stretching orientation: The cooled and shaped film blank is subjected to biaxial stretching treatment. First, it is stretched longitudinally at 80℃ with a stretching ratio of 2.5 times and a stretching speed of 5m / min; then it is stretched transversely at 90℃ with a stretching ratio of 3 times and a stretching speed of 4m / min.

[0025] S6 Heat setting and winding: The stretched and oriented film preform is heat set at 110℃ for 15s. After edge trimming and traction, it is wound up at a speed of 3m / min and a tension of 50N to obtain the high-barrier polymer film product. Example 2

[0026] This application discloses a method for preparing a high-barrier polymer film through multilayer co-extrusion. Please refer to [link to relevant documentation]. Figure 1 and Figure 2 It includes, from the inside out, a heat-sealing layer, an adhesive layer, a barrier layer, and an outer layer, and the preparation method includes the following steps: S1 Raw Material Pretreatment: Linear low-density polyethylene and metallocene polyethylene were mixed at a mass ratio of 7.5:2.5 as the heat-sealing layer raw material. Ethylene-acrylic acid copolymer was selected as the adhesive layer raw material. Ethylene-vinyl alcohol copolymer and organomontmorillonite modified with silane coupling agent (added at 7% of the mass of ethylene-vinyl alcohol copolymer) were selected as the barrier layer raw material. High-density polyethylene was selected as the outer layer raw material. The heat-sealing layer raw material and the outer layer raw material were dried at 85℃ for 2.5h, the adhesive layer raw material was dried at 75℃ for 2h, and the barrier layer raw material was dried at 105℃ for 3.5h.

[0027] S2 Raw Material Melting and Plasticizing: The pretreated raw materials for each layer are added to the corresponding extruders. The barrel temperature of the first extruder (heat sealing layer) is controlled at 170℃, the barrel temperature of the second extruder (adhesive layer) is controlled at 180℃, the barrel temperature of the third extruder (barrier layer) is controlled at 190℃, and the barrel temperature of the fourth extruder (outer layer) is controlled at 175℃. The screw speed of each extruder is 50r / min. Melting and plasticizing are carried out to obtain the molten material of each layer.

[0028] S3 Multilayer Co-extrusion Composite: The molten material of each layer is conveyed to a co-extrusion die at a temperature of 200℃, and the flow rate ratio of each layer of molten material is controlled at 3:1:2:1:3 (corresponding to heat-sealing layer, adhesive layer, barrier layer, adhesive layer, and outer layer). The layers are composited through the flow channels in the co-extrusion die to form a multilayer composite melt.

[0029] S4 Cooling and Shaping: After the multilayer composite melt is extruded from the co-extrusion die, it is cooled and shaped using a cooling roller at a temperature of 25℃. The bonding pressure between the film blank and the cooling roller is controlled at 0.4MPa, and the cooling time is 7s, to obtain a preliminary multilayer film blank.

[0030] S5 stretching orientation: The cooled and shaped film blank is subjected to biaxial stretching treatment. First, it is stretched longitudinally at 85°C with a stretching ratio of 3 times and a stretching speed of 6.5 m / min; then it is stretched transversely at 95°C with a stretching ratio of 3.5 times and a stretching speed of 5.5 m / min.

[0031] S6 Heat setting and winding: The stretched and oriented preform is heat-set at 120°C for 12 seconds. After edge trimming and traction, it is wound up at a speed of 4.5 m / min and a tension of 65 N to obtain the high-barrier polymer film product. Example 3

[0032] This application discloses a method for preparing a high-barrier polymer film through multilayer co-extrusion. Please refer to [link to relevant documentation]. Figure 1 and Figure 2 It includes, from the inside out, a heat-sealing layer, an adhesive layer, a barrier layer, and an outer layer, and the preparation method includes the following steps: S1 Raw Material Pretreatment: Linear low-density polyethylene and metallocene polyethylene were mixed at a mass ratio of 8:2 as the heat-sealing layer raw material. Ethylene-acrylic acid copolymer was selected as the adhesive layer raw material. Ethylene-vinyl alcohol copolymer and organomontmorillonite modified with silane coupling agent (added at 10% of the mass of ethylene-vinyl alcohol copolymer) were selected as the barrier layer raw material. High-density polyethylene was selected as the outer layer raw material. The heat-sealing layer raw material and the outer layer raw material were dried at 90℃ for 2 hours. The adhesive layer raw material was dried at 80℃ for 1.5 hours. The barrier layer raw material was dried at 110℃ for 3 hours.

[0033] S2 Raw Material Melting and Plasticizing: The pretreated raw materials for each layer are added to the corresponding extruders. The barrel temperature of the first extruder (heat sealing layer) is controlled at 180℃, the barrel temperature of the second extruder (adhesive layer) is controlled at 190℃, the barrel temperature of the third extruder (barrier layer) is controlled at 200℃, and the barrel temperature of the fourth extruder (outer layer) is controlled at 185℃. The screw speed of each extruder is 60r / min. Melting and plasticizing are carried out to obtain the molten material of each layer.

[0034] S3 Multilayer Co-extrusion Composite: The molten material of each layer is conveyed to a co-extrusion die at a temperature of 210℃, and the flow rate ratio of each layer of molten material is controlled at 3:1:2:1:3 (corresponding to heat-sealing layer, adhesive layer, barrier layer, adhesive layer, and outer layer). The layers are composited through the flow channels in the co-extrusion die to form a multilayer composite melt.

[0035] S4 Cooling and Shaping: After the multilayer composite melt is extruded from the co-extrusion die, it is cooled and shaped using a cooling roller at a temperature of 30℃. The bonding pressure between the film preform and the cooling roller is controlled at 0.5MPa, and the cooling time is 5s, to obtain a preliminary multilayer film preform.

[0036] S5 stretching orientation: The cooled and shaped film blank is subjected to biaxial stretching treatment. First, it is stretched longitudinally at 90℃ with a stretching ratio of 3.5 times and a stretching speed of 8m / min; then it is stretched transversely at 100℃ with a stretching ratio of 4 times and a stretching speed of 7m / min.

[0037] S6 Heat setting and winding: The stretched and oriented film preform is heat set at 130℃ for 10 seconds. After edge trimming and traction, it is wound up at a speed of 6m / min and a tension of 80N to obtain the high-barrier polymer film product.

[0038] The high-barrier polymer membranes prepared in Examples 1-3 were subjected to performance tests, and the test results are shown in the table below: Test Project Example 1 Example 2 Example 3 Oxygen permeability (cm³ / (m²·24h·0.1MPa)) 2.1 1.8 1.5 Water vapor transmission rate (g / (m²·24h)) 1.3 1.1 0.9 Interlayer peel strength (N / 15mm) 5.2 5.8 6.3 Thickness uniformity (deviation rate) ±3.2% ±2.8% ±2.5% As can be seen from the above test results, the high-barrier polymer membrane prepared by the present invention has excellent oxygen and water vapor barrier properties, strong interlayer bonding, good thickness uniformity, and excellent comprehensive performance.

[0039] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for multilayer co-extrusion of high barrier polymer films, characterized in that: The preparation method comprises the following steps: S1: raw material pretreatment: select the raw material of the heat sealing layer, the raw material of the adhesive layer, the raw material of the barrier layer and the raw material of the outer layer, and dry each raw material, wherein the raw material of the heat sealing layer is a mixture of linear low-density polyethylene and metallocene polyethylene, the raw material of the adhesive layer is ethylene-acrylic acid copolymer, the raw material of the barrier layer is a composite modified material of ethylene-vinyl alcohol copolymer and montmorillonite, and the raw material of the outer layer is high-density polyethylene; S2: melt plasticization of raw materials: add the pretreated raw materials of each layer into the corresponding extruders respectively for melt plasticization, control the barrel temperature and screw rotation speed of each extruder, and obtain the melt of each layer; S3: multi-layer co-extrusion: deliver the melt of each layer to the co-extrusion die, perform layering and compounding through the flow channel in the co-extrusion die, and form a multi-layer composite melt; S4: cooling and shaping: after the multi-layer composite melt is extruded from the co-extrusion die, perform cooling and shaping by using a cooling roller, and obtain a preliminarily shaped multi-layer film blank; S5: stretching and orientation: perform bidirectional stretching on the film blank after cooling and shaping, and perform longitudinal stretching and transverse stretching in sequence; S6: heat setting and winding: perform heat setting on the film blank after the stretching and orientation is completed, and then perform edge cutting and traction, and wind to obtain a high-barrier high polymer film product.

2. The multilayer co-extrusion method for preparing a high-barrier polymer film according to claim 1, characterized in that: In S1, the mass ratio of linear low-density polyethylene to metallocene polyethylene in the raw material of the heat sealing layer is 7:3-8:2, and the montmorillonite in the raw material of the barrier layer is an organic montmorillonite modified by a silane coupling agent, and the addition amount of the montmorillonite is 5%-10% of the mass of the ethylene-vinyl alcohol copolymer.

3. The multilayer co-extrusion method for preparing a high-barrier polymer film according to claim 1, characterized in that: In S1, the drying treatment conditions of each raw material are as follows: the raw material of the heat sealing layer and the raw material of the outer layer are dried at 80-90 DEG C for 2-3 hours, the raw material of the adhesive layer is dried at 70-80 DEG C for 1.5-2.5 hours, and the raw material of the barrier layer is dried at 100-110 DEG C for 3-4 hours.

4. The multilayer co-extrusion method for preparing a high-barrier polymer film according to claim 1, characterized in that: In S2, the extruders include a first extruder, a second extruder, a third extruder and a fourth extruder, which correspond to the delivery of the melt of the heat sealing layer, the adhesive layer, the barrier layer and the outer layer respectively, and the barrel temperature of each extruder is controlled as follows: the first extruder is 160-180 DEG C, the second extruder is 170-190 DEG C, the third extruder is 180-200 DEG C, and the fourth extruder is 165-185 DEG C, and the screw rotation speed of each extruder is 40-60 r / min.

5. The multilayer co-extrusion method for preparing a high-barrier polymer film according to claim 1, characterized in that: In S3, the temperature of the co-extrusion die is controlled at 190-210 DEG C, the flow rate ratio of each layer melt in the co-extrusion die is consistent with the thickness ratio of each layer of the finished product film, and the thickness ratio of the heat sealing layer, the adhesive layer, the barrier layer, the adhesive layer and the outer layer in the finished product film is 3:1:2:1:

3.

6. The multilayer co-extrusion method for preparing a high-barrier polymer film according to claim 1, characterized in that: In S4, the temperature of the cooling roller is 20-30 DEG C, the bonding pressure of the film blank and the cooling roller is 0.3-0.5 MPa, and the cooling time is 5-10 s.

7. The multilayer co-extrusion method for producing a high-barrier polymer film according to claim 1, characterized in that: In S5, the temperature of the longitudinal stretching is 80-90 DEG C, the stretching ratio is 2.5-3.5 times, and the stretching speed is 5-8 m / min, and the temperature of the transverse stretching is 90-100 DEG C, the stretching ratio is 3-4 times, and the stretching speed is 4-7 m / min.

8. The multilayer co-extrusion method for preparing a high-barrier polymer film according to claim 1, characterized in that: In S6, the temperature of the heat setting treatment is 110-130 DEG C, the treatment time is 10-15 s, the winding speed is 3-6 m / min, and the winding tension is 50-80 N.

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