A multi-layer co-extruded high barrier ultra-thick film

Abstract

The present invention discloses a multi-layer co-extruded high-barrier ultra-thick film, which has multiple layers, including an outer shell layer, an adhesive, a barrier layer and a reverse osmosis layer, wherein the polyethylene is low-density polyethylene. The multi-layer co-extruded high-barrier ultra-thick film provided by the present invention changes the traditional direct blow molding process into a gradual pressurization and gradual thickening process. In this process, the pressure of the nip roller and the air volume of the wind ring are gradually increased to blow the film to a specified width, and then the process parameters are kept unchanged. After confirming that it is stable, the pressure of the nip roller is continued to be increased to thicken the film thickness to achieve the production of ultra-thick film. In addition, a nylon layer is added to the film material to maintain the stability of the film during high-temperature crystallization, and the traditional ultra-low-density polyethylene material is changed to low-density polyethylene to ensure the stability of the film thickening.

Description

Technical Field

[0001] The invention relates to a multi-layer co-extruded high-barrier ultra-thick film, in particular to an ultra-thick preparation method of a high-barrier biological film by using an upward blowing process. Background Art

[0002] Composite film is used as a packaging material in many fields. However, since the material of the film itself is made of co-extrusion blow molding of multiple layers of composite materials, with multiple materials stacked on each other, it is necessary to first determine the width of the film during the production process, and then increase the air volume while increasing the film drawing capacity to increase the film bubble, thereby increasing the thickness of the film.

[0003] In this process, the film material is first heated up and then cooled down, so the film thickness depends entirely on the film material. For today's commonly used pharmaceutical films, the standard requirement is 325um-400um, which is difficult to achieve with today's blowing process because the film bubble is prone to collapse during the blowing process, making it impossible to increase the thickness.

[0004] The main reason in the process is that the material is continuously blown after being heated, and the film cannot be cooled quickly during the thickening process, causing the film bubble to overheat and collapse. In this process, if cooling equipment is added or the cooling temperature is lowered, the film is continuously cooled, which will produce condensed water. This will be blown onto the film and form spots on the film, affecting product quality.

[0005] The traditional process is just to hot-melt extrude the material, and then use the upper blowing equipment to press the rollers to make the material evenly distributed to form a film, and then blow mold it. This can only rely on the characteristics of the material itself. The size that can be blown and thickened can only rely on the material itself. It cannot improve the ability to increase the thickness, and ultimately it is impossible to produce ultra-thick films. Summary of the invention

[0006] The present invention aims to provide a multi-layer co-extruded high-barrier ultra-thick film. By utilizing process design, the traditional direct blow molding process is changed to gradual pressurization and gradual thickening. In this process, the cooling time of the film is increased. At the same time, a nylon layer is added to the film material to maintain the stability of the film during high-temperature crystallization. The traditional ultra-low-density polyethylene material is changed to low-density polyethylene to ensure the stability of the film thickening.

[0007] In order to solve the above problems, the present invention provides a multi-layer co-extruded high barrier ultra-thick film adopts the following technical solutions:

[0008] A multi-layer co-extruded high-barrier ultra-thick film, which is provided with multiple layers, including an outer shell layer, an adhesive, a barrier layer and a reverse osmosis layer, wherein the outer shell layer is made of polyethylene. According to the use requirements of the film, the barrier layer and the reverse osmosis layer are located in the middle of the film, the adhesive is arranged on the upper and lower sides of the barrier layer respectively, and the outer shell layer is arranged on the outer side of the adhesive. The outer shell layer on one side of the adhesive can be provided with multiple layers, and the number of outer shell layers on both sides of the film is the same; wherein the polyethylene is low-density polyethylene;

[0009] The production process is as follows:

[0010] In the first step, the material particles of the shell layer, adhesive layer, nylon layer, barrier layer and reverse osmosis layer are respectively put into different extruders, and the extrusion temperature is set for different materials. After the material particles are extruded, they are formed layer by layer and then sent to the film outlet of the equipment for blow molding;

[0011] In the second step, the air ring of the equipment blows air to cool the film, forming a film bubble, which moves in the nip roller to realize the film drawing operation;

[0012] The third step is to gradually increase the pressure of the nip roller while pulling the film until it reaches the maximum pressure set by the equipment, thereby increasing the film thickness until the film thickness reaches the standard;

[0013] The fourth step is to keep the pressure of the nip roller unchanged, increase the air volume inside the air ring of the equipment while keeping the film thickness unchanged, and reduce the air volume outside the air ring, so as to increase the width of the film;

[0014] The fifth step is to detect the film width and stop adjusting the air volume after reaching the standard; the film production is completed.

[0015] Furthermore, in the first step, the nip roller pressure is 10%-15% of the final pressure.

[0016] Furthermore, in the third step, when the film thickness reaches the preset value, the device is maintained at a stable output for not less than 10 minutes before proceeding to the fourth step.

[0017] Furthermore, the diameter of the membrane opening of the equipment used is not less than 2.3CM, and the blowing ratio is 1.2-2.0.

[0018] Furthermore, the number of mixed film layers of the equipment used is not less than seven.

[0019] Furthermore, the barrier layer has an oxygen barrier capacity of 25 mol over an operating temperature range (OTR) of less than 0.1 in the formulation.

[0020] Furthermore, the low-density polyethylene used in the outer shell layer has a melt flow index (MFI) less than 1.

[0021] Furthermore, a nylon layer is arranged between the adhesive and the outer shell layer, and the nylon layer is made of copolymer nylon.

[0022] The beneficial effects of the present invention are as follows: a multi-layer co-extruded high-barrier ultra-thick film provided by the present invention changes the traditional direct blow molding process into a gradual pressurization and gradual thickening process. In this process, the pressure of the nip roller and the air volume of the air ring are gradually increased to blow the film to a specified width, and then the process parameters are kept unchanged. After confirmation of stability, the pressure of the nip roller is continued to be increased to thicken the film thickness and realize the production of ultra-thick film. In addition, a nylon layer is added to the film material to maintain the stability of the film during high-temperature crystallization, and the traditional ultra-low-density polyethylene material is changed to low-density polyethylene to ensure the stability of the film thickening. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Attached Figure 1 Schematic diagram of a common film structure of the present invention.

[0024] Attached Figure 2 Schematic diagram of the film structure of the first preferred embodiment of the present invention.

[0025] Attached Figure 3 It is a schematic diagram of the film structure of the second preferred embodiment of the present invention.

[0026] Attached Figure 4 This is a schematic diagram of the film structure of the third preferred embodiment of the present invention.

[0027] Attached Figure 5 The process flow chart of the preferred embodiment of the present invention.

[0028] Among them: 1. outer shell layer, 2. adhesive, 3. barrier layer, 4. reverse osmosis layer, 5. nylon layer. DETAILED DESCRIPTION

[0029] In order to more clearly understand the technical solution provided by the present invention, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0030] During the experiment, taking a product whose structure is polyethylene, adhesive, barrier film, adhesive, and polyethylene as an example, the film thickness is required to reach 325um and the width is not less than 1400mm.

[0031] As attached Figure 2As shown, in Example 1, a multi-layer co-extruded high-barrier ultra-thick film has a structure of polyethylene, polyethylene, adhesive, barrier film (EVOH), adhesive, polyethylene, and polyethylene in sequence; wherein the polyethylene adopts ULDPE, i.e., ultra-low density polyethylene; the barrier film (EVOH) adopts Mitsubishi Chemical's DC2504VB model, and its 25 mol oxygen barrier capacity in the formula OTR is less than 0.1, which can meet the requirements of biological agents; the adhesive adopts DuPont's 41E687 model.

[0032] The extruder and film head are heated to the required temperature. The polyethylene extruder is set at 210 degrees, the adhesive extruder is set at 215 degrees, and the barrier film (EVOH) extruder is set at 225 degrees. The film head of the equipment is set at 225 degrees.

[0033] For the initial feeding, polyethylene (ULDPE) is distributed in the weighing hoppers of the four extruders A, B, F, and G, adhesive (41E687) is distributed in the weighing hoppers of the extruders C and E, and barrier film (EVOH) is distributed in the weighing hopper of the D extruder.

[0034] Equipment setting: production capacity, i.e. nip roller pressure, is set at 580kg / h;

[0035] The experimental process is as follows: the material particles are extruded layer by layer and then the film is drawn. At this time, the production capacity is set at 140kg / h. First, the thickness of the layers is evenly distributed. After gradually increasing the production capacity to 280kg / h, the air volume of the wind ring is increased to make the film bubble larger. When the display width is 1600MM, keep the parameters unchanged. After 10 minutes of normal stability, the production capacity is gradually increased to 580kg / h. Without changing the width, the film thickness is gradually increased. After the final thickness increases to 252um, the film bubble collapses directly and cannot be thickened any further.

[0036] Failure analysis: From the experimental analysis, physical cooling cannot instantly cool the polyethylene (ULDPE) to the crystallization temperature when the material rushes out of the membrane head and the membrane mouth. Therefore, the external air cooling cannot hold the film and stabilize the film bubble without sufficient cooling. Solution: Let the cooling temperature continue to drop to shorten the film cooling time, but the air ring will inevitably produce condensed water as the temperature drops. The condensed water will often be blown to the film by the wind of the wind ring, and the film will have stripes, so this method does not work.

[0037] The second solution is to replace the polyethylene (ULDPE) material of the second layer with nylon PA6 / 66, and match the production temperature to 225 degrees. The crystallization temperature of nylon is 180 degrees, which helps to stabilize the film during production.

[0038] As attached Figure 3As shown, in Example 2: a multi-layer co-extruded high barrier ultra-thick film, whose structure is polyethylene, nylon, adhesive, barrier film (EVOH), adhesive, nylon, polyethylene in sequence; wherein the polyethylene adopts ULDPE, i.e., ultra-low density polyethylene; the barrier film (EVOH) adopts Mitsubishi Chemical's DC2504VB model, and its 25 mol oxygen barrier capacity OTR in the formula is less than 0.1, which can meet the requirements of biological agents; the adhesive adopts DuPont's 41E687 model, and the nylon adopts BASF's copolymer nylon C40L model.

[0039] The extruder and the film head are heated to the required temperature. The polyethylene extruder is set at 210 degrees; the adhesive extruder is set at 215 degrees; the nylon base machine is set at 225 degrees; the barrier film (EVOH) extruder is set at 225 degrees. The film head is set at 225 degrees.

[0040] For the initial feeding, polyethylene (ULDPE) is distributed in the weighing hoppers of extruders A and G; adhesive (41E687) is distributed in the weighing hoppers of extruders B and F; nylon is distributed in the weighing hoppers of extruders C and E, and barrier film (EVOH) is distributed in the weighing hopper of extruder D.

[0041] Equipment setting: production capacity, i.e. nip roller pressure, is set to 580kg / h;

[0042] The experimental process is as follows: the material particles are extruded layer by layer and then the film is drawn. The capacity is set at 140kg / h, and the thickness ratio between layers is evenly distributed. After gradually increasing the capacity to 280kg / h, the air volume of the wind ring is increased to make the film bubble larger. When the display width is 1600MM, the parameters remain unchanged. After 10 minutes of normal stability, the capacity is gradually increased to 580kg / h. Without changing the width, the film thickness is gradually increased. After the final thickness increases to 280um, the film bubble collapses directly and cannot be thickened any further.

[0043] Failure analysis: The same problem occurred in this production as in the first experiment, and the film could not be cooled sufficiently as the thickness increased.

[0044] As attached Figure 3 As shown, in Example 3: a multi-layer co-extruded high barrier ultra-thick film, whose structure is polyethylene, polyethylene, polyethylene, adhesive, barrier film (EVOH), adhesive, polyethylene, polyethylene, polyethylene; wherein the barrier film (EVOH) adopts Mitsubishi Chemical's DC2504VB model, and its 25 mol oxygen barrier capacity OTR in the formula is less than 0.1, which can meet the requirements of biological agents; the adhesive adopts 41E687 model; the polyethylene selects low-density polyethylene (non-ULDPE) with MFI less than 1.

[0045] The extruder and the film head are heated to the required temperature. The polyethylene extruder is set at 210 degrees; the adhesive extruder is set at 215 degrees; the barrier film (EVOH) extruder is set at 225 degrees. The film head is set at 225 degrees.

[0046] For the initial feeding, low-density polyethylene is distributed in the weighing hoppers of the four extruders A, B, C, G, H, and I; the adhesive (41E687) is distributed in the weighing hoppers of the D and F extruders, and the barrier film (EVOH) is distributed in the weighing hopper of the D extruder.

[0047] Equipment setting: The production capacity, i.e. the nip roller pressure, is set to 580kg / h.

[0048] The experimental process is as follows: the material particles are extruded layer by layer and then the film is drawn. The production capacity is set at 140kg / h, and the thickness ratio between layers is evenly distributed. After gradually increasing its production capacity to 580kg / h, it is shown that when the film thickness reaches 325um, the film width is maintained at 980mm. After 10 minutes of normal stability, the cooling air volume in the air ring is gradually increased, and the air volume of the outer air ring is reduced. Without changing the thickness, the film width is gradually increased to 1200mm and 1400mm. Finally, at a width of 1400mm, we successfully completed the production experiment of biological agent films with a width of 1400mm and a thickness of 325um and a width of 1400mm and a thickness of 410um.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than a limiting technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A multi-layer co-extruded high barrier ultra-thick film, characterized in that: A total of multiple layers are provided, including an outer shell layer, an adhesive, a barrier layer and a reverse osmosis layer, wherein the outer shell layer is made of polyethylene. According to the use requirements of the film, the barrier layer and the reverse osmosis layer are located in the middle of the film, the adhesive is arranged on the upper and lower sides of the barrier layer respectively, and the outer shell layer is arranged on the outside of the adhesive. The outer shell layer on one side of the adhesive can be provided with multiple layers, and the number of outer shell layers on both sides of the film is the same; The production process is as follows: In the first step, the material particles of the shell layer, adhesive layer, nylon layer, barrier layer and reverse osmosis layer are respectively put into different extruders, and the extrusion temperature is set for different materials. After the material particles are extruded, they are formed layer by layer and then sent to the film outlet of the equipment for blow molding. The nip roller pressure is 10%-15% of the final pressure. In the second step, the air ring of the equipment blows air to cool the film, forming a film bubble, which moves in the nip roller to realize the film drawing operation; The third step is to gradually increase the pressure of the nip roller while pulling the film until it reaches the maximum pressure set by the equipment, thereby increasing the film thickness until the film thickness reaches the standard; when the film thickness reaches the preset value, maintain stable output of the equipment for no less than 10 minutes; The fourth step is to keep the pressure of the nip roller unchanged, increase the air volume inside the air ring of the equipment while keeping the film thickness unchanged, and reduce the air volume outside the air ring, so as to increase the width of the film; The fifth step is to detect the film width and stop adjusting the air volume after reaching the standard; the film production is completed; The 25 molar oxygen barrier capacity of the barrier layer described in its structure is less than 0.1 in the working temperature range of the formulation; The low-density polyethylene used in the outer shell layer in the structure has a melt flow index of less than 1; The diameter of the membrane mouth of the equipment used is not less than 2.3CM, and the blowing ratio is 1.2-2.

0.

2. The multi-layer co-extruded high barrier ultra-thick film according to claim 1, characterized in that: The number of mixed film layers of the equipment used in its production process is not less than seven layers.

Images