A co-extrusion production method of nylon-PE composite film

Abstract

The present application relates to the technical field of composite film production of recycling waste, and particularly relates to a co-extrusion production method of nylon and PE composite film, comprising the following steps: obtaining the dust distribution density of the outer wall of a hopper and the air flow rate around an initial film; adjusting the relative horizontal distance between the die head of an extruder and a cooling roller; obtaining the surface image of the initial film on the cooling roller after adjusting the relative horizontal distance; determining the shrinkage area of the initial film according to the surface image of the initial film; adjusting the peeling angle of the initial film and the cooling roller according to the coincidence degree of the abnormal dust distribution area and the shrinkage area of the initial film; continuously extruding the initial film according to the peeling angle of the initial film and the cooling roller; and preheating, stretching, heat setting and cooling and winding the initial film peeled from the cooling roller in sequence to form the nylon and PE composite film. The present application realizes the improvement of the production efficiency of the composite film.

Description

Technical Field

[0001] This invention relates to the field of composite film production technology based on recycled waste materials, and more particularly to a co-extrusion production method for nylon and PE composite films. Background Technology

[0002] Composite films are widely used in the packaging of food, pharmaceuticals, and electronic products due to their excellent barrier properties, mechanical strength, and designability. However, the raw material particles of composite films produced from recycled waste often have more dust or fine fibers adhering to their surface after crushing, washing, and regranulation. During material conveying and feeding, this dust is easily dispersed in the production environment, especially in the area between the die head and the cooling roller. The high-temperature melt casting forms a molten sheet, which heats the surrounding air and creates an upward airflow. This airflow easily carries dust from near the hopper and around the equipment to the surface of the cooling roller, and then it is drawn into the film by electrostatic adsorption, resulting in phenomena such as crystal points, fish eyes, and surface roughness in the final film product. Therefore, there is an urgent need for a nylon / PE composite film and multilayer co-extrusion production method that can overcome the problems of dust, cooling, and static electricity in the production of nylon / PE composite films using recycled waste, as well as the resulting decline in film quality.

[0003] Chinese Patent Publication No. CN107745509A discloses a method for preparing a multilayer co-extruded biaxially oriented composite film. The method combines simultaneous stretching using a tubular film method with a two-step stretching process using a flat film method. For the composite film, the extruded tubular film is first simultaneously melt-stretched in both the longitudinal and transverse directions using a co-extrusion tubular film forming process to obtain a tubular film. Then, the tubular film is folded flat to obtain a double-layer film or a single-layer film. Specifically, in the folded state, when the temperature of the inner layer material of the extruded film reaches or falls below its glass transition temperature, a double-layer film is obtained; when the temperature of the inner layer material of the extruded film exceeds its melting point, a single-layer film is obtained. The double-layer film is then further processed... Alternatively, a single-layer film can be pretreated, and then a second longitudinal non-melting stretching of the double-layer or single-layer film can be performed using a flat film stretching method. Finally, the double-layer or single-layer film can be post-treated to obtain a biaxially oriented composite film. It can be seen that the preparation method of the multilayer co-extruded biaxially oriented composite film has the problem that dust around the outer wall of the hopper is drawn into the surface of the cooling roller by the rising airflow generated by the high-temperature melt casting forming a molten sheet and heating the surrounding air. This dust is then carried onto the surface of the initial film during cooling and shrinkage, resulting in additional static electricity during the initial film peeling off the cooling roller, thus increasing the traction stress of the traction roller during the peeling process. Summary of the Invention

[0004] To address this issue, the present invention provides a co-extrusion production method for nylon and PE composite films, which overcomes the problem in the prior art where dust around the outer wall of the hopper is drawn into the surface of the cooling roller by the rising airflow generated by the high-temperature melt casting to form a molten sheet and heating the surrounding air. This dust is then carried onto the surface of the initial film during cooling and shrinkage, resulting in additional static electricity during the initial film peeling off the cooling roller, which in turn increases the traction stress of the traction roller during the initial film peeling off the cooling roller.

[0005] To achieve the above objectives, the present invention provides a method for co-extruding nylon and PE composite films, comprising:

[0006] Each type of raw material particle obtained after sieving is loaded into the corresponding hopper, and each type of raw material particle is heated and extruded in sequence to obtain an initial film.

[0007] The first dust distribution density on the outer wall of the hopper and the air velocity around the initial film are obtained respectively.

[0008] The relative horizontal distance between the extruder die and the cooling roller is adjusted based on the first dust distribution density and the surrounding air velocity.

[0009] Obtain an initial surface image of the film on the cooling roller after adjusting the relative horizontal distance;

[0010] The initial film shrinkage region is determined based on the surface image of the initial film.

[0011] The dust distribution anomaly region is determined based on the second dust distribution density above the initial film;

[0012] Adjust the peeling angle between the initial film and the cooling roller based on the degree of overlap between the abnormal dust distribution area and the initial film shrinkage area;

[0013] The initial film continues to be extruded according to the peel angle between the initial film and the cooling roller;

[0014] The initial film peeled from the cooling roller is sequentially preheated, stretched, heat-set, and cooled and wound up to form a nylon and PE composite film.

[0015] Further, adjusting the relative horizontal distance between the extruder die and the cooling roller based on the first dust distribution density and the surrounding air velocity includes:

[0016] The first dust distribution density is compared with the second preset density, and the air flow rate is compared with the preset flow rate;

[0017] If the first dust distribution density is greater than the second preset density, and the air velocity is greater than the preset velocity, then the relative horizontal distance between the extruder die and the cooling roller is reduced.

[0018] Furthermore, the relative horizontal distance is negatively correlated with the first dust distribution density.

[0019] Further, determining the initial film shrinkage region based on the surface image of the initial film includes:

[0020] Obtain the temperature reduction of the initial thin film on the surface image;

[0021] The largest region enclosed by all sampling points whose temperature reduction is less than the preset temperature reduction is defined as the initial film shrinkage region.

[0022] Further, determining the dust distribution anomaly region based on the second dust distribution density above the initial film includes:

[0023] Obtain the second dust distribution density located above the initial film;

[0024] The second dust distribution density is compared with the first preset density and the second preset density;

[0025] The largest area enclosed by all sampling points whose second dust distribution density is greater than the first preset density and less than or equal to the second preset density is defined as the dust distribution abnormal area.

[0026] Furthermore, the second preset density is greater than the first preset density.

[0027] Further, adjusting the peel angle between the initial film and the cooling roller based on the overlap between the dust distribution abnormality area and the initial film shrinkage area includes:

[0028] The overlap between the abnormal dust distribution area and the initial film shrinkage area is compared with a preset overlap.

[0029] If the overlap is greater than the preset overlap, then the peeling angle between the initial film and the cooling roller is reduced.

[0030] Furthermore, the overlap is the ratio of the area of ​​the dust distribution abnormal region to the area of ​​the initial film shrinkage region.

[0031] Furthermore, the peeling angle between the initial film and the cooling roller is negatively correlated with the degree of overlap.

[0032] Furthermore, the peel angle between the initial film and the cooling roller is the angle between the tangent of the initial film along the surface of the cooling roller at the separation line between the initial film and the cooling roller and the plane containing the separation line and the central axis of the cooling roller.

[0033] Compared with the prior art, the beneficial effect of the present invention is that, by obtaining the first dust distribution density on the outer wall of the hopper, if the first dust distribution density is greater than the second preset density, it indicates that the dust-containing airflow escapes through the connection of the hopper to the outer wall of the hopper. If the air velocity around the initial film is greater than the preset velocity, it indicates that the high-temperature melt casting forms a molten sheet that heats the surrounding air, thereby forming an upward airflow. If the first dust distribution density is greater than the second preset density, the pressure of the upward airflow is low, which carries the dust near the hopper and around the equipment to the surface of the cooling roller and is drawn into the initial film by electrostatic adsorption. By reducing the relative horizontal distance between the die of the extruder and the cooling roller, the angle of entry of the external ambient air between the cooling roller and the die is reduced, thereby reducing the generated upward airflow, thus weakening the strength and suction force of the upward airflow and reducing the ability of the upward airflow to carry the dust in the area with abnormal first dust distribution density to the surface of the cooling roller.

[0034] Furthermore, this invention adjusts the relative horizontal distance between the extruder die and the cooling roller to be smaller when the first dust distribution density is higher. According to the particle movement law, the dust diffuses a longer distance in the rising airflow formed by the high-temperature melt casting forming a molten sheet that heats the surrounding air. The probability of the dust eventually reaching the surface of the cooling roller is greater. By reducing the dust diffusion distance, the straight-line distance that the dust needs to travel from the outer wall of the hopper to the surface of the cooling roller is substantially shortened. This means that most of the dust falls or is carried away by the bypass airflow before it is effectively transported to the surface of the initial film by the airflow, and thus cannot contact the film, thereby further reducing the amount of dust reaching the surface of the cooling roller.

[0035] Furthermore, this invention defines the largest region enclosed by all sampling points on the surface image whose temperature decrease is less than a preset temperature decrease as the initial film shrinkage region, and obtains the second dust distribution density above the initial film within a unit period. If the second dust distribution density is greater than the first preset density and less than or equal to the second preset density, it indicates that dust is more easily trapped in the initial film that is cooling and shrinking, thereby enhancing the surface roughness of the initial film with trapped dust. This enhances the surface roughness of the initial film, causing it to carry additional electrostatic charge when peeled off the cooling roller, thus increasing the traction stress on the traction roller during the initial film peeling off the cooling roller. By reducing the initial... The angle between the tangent of the initial film along the surface of the cooling roller at the separation line of the film and the extension of the radius of the cooling roller at the separation point reduces the vertical height of the initial film on the cooling roller during the peeling process caused by the increased traction stress on the traction roller. This transforms the traction stress perpendicular to the surface of the cooling roller into a force parallel to the surface of the cooling roller, further reducing the stress concentration phenomenon of the initial film at the peeling point. This makes the peeling process of the initial film smoother, reduces the friction intensity and static electricity generation rate during the peeling process, and thus offsets the negative impact of the increased surface roughness of the initial film due to dust trapping. This ensures that the traction stress is restored to the set level required for stable production and improves the production efficiency of the composite film.

[0036] Furthermore, the present invention adjusts the peel angle between the initial film and the cooling roller to be smaller when the ratio of the area of ​​the abnormal dust distribution region to the area of ​​the initial film shrinkage region is larger. The initial film shrinkage region represents the area where the initial film generates shrinkage stress due to uneven cooling; the abnormal dust distribution region represents the area where dust floats and may settle. When the ratio of the area of ​​the abnormal dust distribution region to the area of ​​the initial film shrinkage region is larger, it means that the probability of dust settling in the area where the initial film generates shrinkage stress due to uneven cooling is greater. By reducing the glass angle between the initial film and the cooling roller as the overlap increases, the traction stress on the traction roller is evenly distributed, thereby avoiding the areas where dust floats and dust may settle. Attached Figure Description

[0037] Figure 1 This is an overall flow chart of the co-extrusion production method of nylon and PE composite film according to an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the extruder, die, cooling roller, and initial film in the co-extrusion production method of nylon and PE composite film according to an embodiment of the present invention.

[0039] Figure 3This is a flowchart illustrating the process of adjusting the relative horizontal distance between the die head and the cooling roller of the extruder in the co-extrusion production method of nylon and PE composite film according to an embodiment of the present invention.

[0040] Figure 4 This is a flowchart illustrating the process of determining abnormal dust distribution areas in the co-extrusion production method of nylon and PE composite films according to an embodiment of the present invention.

[0041] Explanation of reference numerals in the attached drawings: 1-Extruder, 2-Die head, 3-Cooling roller, 4-Initial film, 5-Thermal wind speed sensor, 6-Industrial camera, 7-First hopper, 8-Second hopper, 9-First feed pipe, 10-Second feed pipe, 11-Mel transfer pipe, 12-Temperature control pipe. Detailed Implementation

[0042] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0043] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0044] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0045] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] Please see Figure 1 The diagram shown is an overall flow chart of the co-extrusion production method of nylon and PE composite film according to an embodiment of the present invention. The co-extrusion production method of nylon and PE composite film according to an embodiment of the present invention includes:

[0047] Step S1: Each type of raw material particle obtained by sieving is loaded into the corresponding hopper, and each type of raw material particle is heated and extruded in sequence to obtain the initial film 4.

[0048] Step S2: Obtain the first dust distribution density on the outer wall of the hopper and the air velocity around the initial film 4, respectively.

[0049] Step S3: Adjust the relative horizontal distance between the die head 2 of the extruder 1 and the cooling roller 3 based on the first dust distribution density and the surrounding air velocity;

[0050] Step S4: Obtain a surface image of the initial film 4 on the cooling roller 3 after adjusting the relative horizontal distance;

[0051] Step S5: Determine the shrinkage region of the initial film 4 based on the surface image of the initial film 4;

[0052] Step S6: Determine the dust distribution abnormality area based on the second dust distribution density above the initial film 4;

[0053] Step S7: Adjust the peeling angle between the initial film 4 and the cooling roller 3 according to the degree of overlap between the abnormal dust distribution area and the shrinkage area of ​​the initial film 4.

[0054] Step S8: Continue to extrude the initial film 4 according to the peel angle between the initial film 4 and the cooling roller 3;

[0055] Step S9: The initial film 4 peeled off from the cooling roller 3 is preheated, stretched, heat-set and cooled and wound up in sequence to form a nylon and PE composite film.

[0056] Specifically, the raw material particles consist of approximately 30 to 50 parts by weight of polycaprolactam and approximately 40 to 60 parts by weight of linear low-density polyethylene.

[0057] Specifically, the raw material particles also include a compatibilizer of about 5 to 10 parts by weight, which is maleic anhydride-grafted PE, and an additive of about 1 to 3 parts by weight, which is an antioxidant and a slip agent.

[0058] Specifically, the mass of the melt, without considering process losses, is equal to the total mass of all raw material particles added.

[0059] Specifically, the area of ​​the initial film 4 is based on an extrusion width of 1000 mm for the die 2, a circumference of 2000 mm for the cooling roller 3, an extrusion speed of 1 m / s for the die 2, and an area of ​​1 m / s of the initial film 4 extruded per unit time. .

[0060] Specifically, the extruder 1 is a twin-screw extruder 1, and the material of the extruder 1 is alloy steel.

[0061] Please see Figure 2 As shown, this is a schematic diagram of the extruder 1, die 2, cooling roller 3, and initial film 4 in the co-extrusion production method of nylon and PE composite film according to an embodiment of the present invention. The extruder 1 also includes:

[0062] The die head 2 also includes a lip for defining the shape of the molten sheet, the lip having a width of 1100 mm and a gap of 0.5 to 2 mm;

[0063] The first hopper 7 is used to store polycaprolactam raw material particles with a mass ratio of approximately 30 to 50 parts obtained by sieving.

[0064] The first feed pipe 9 is connected to the first hopper 7 and is used to transport the raw material particles temporarily stored in the first hopper to the extruder 1.

[0065] The second hopper 8 is used to store raw material particles of linear low-density polyethylene with a mass ratio of about 40 to 60 parts after sieving.

[0066] The second feed pipe 10 is connected to the second hopper 8 and is used to transport the raw material particles temporarily stored in the second hopper to the extruder 1.

[0067] Temperature control tube 12 is used to isolate the temperature of the first feed tube 9 and the second feed tube 10. The interior of temperature control tube 12 is also equipped with a thermal resistor and heating coil for achieving zoned temperature control.

[0068] An industrial camera 6 is installed on the side wall of the die 2 of the extruder 1 near the cooling roller 3 to obtain a surface image of the initial film 4. The industrial camera 6 has a focal length of 16mm, an installation height of 300-500mm, and a field of view radius of 40mm.

[0069] The melt delivery pipe 11 is used to transport the plasticized and molten melt inside the extruder 1 to the die head 2;

[0070] A thermal wind speed sensor 5 is disposed above the extruder 1 to obtain the airflow rate between the second hopper 8 and the cooling roller 3.

[0071] Specifically, the first hopper 7 has a volume of 50L and is made of stainless steel, while the second hopper 8 has the same physical parameters as the first hopper 7.

[0072] Specifically, the inner diameter of the first feeding tube 9 is 50 mm and the thickness is 3 mm, and the physical parameters of the second feeding tube 10 are the same as those of the first feeding tube 9.

[0073] Specifically, the cooling roller 3 is located below the die head 2 of the extruder 1. The diameter of the cooling roller 3 is 637 mm and the length is 1200 mm. Cooling water flows through the inside of the cooling roller 3. The inlet water temperature is 20-30℃ and the flow rate of the cooling water is 2-3 m / s. The cooling roller 3 is also equipped with an electrostatic adsorption device to adsorb the molten sheet onto the cooling roller 3 through electrostatic adsorption.

[0074] Specifically, the electrostatic adsorption device also includes several electrodes and a high-voltage power supply with an output voltage of 10 to 30 kV.

[0075] As will be understood by those skilled in the art, the operating principle and process of electrostatic adsorption devices are conventional technical means well known to them, and therefore the operating principle and process of electrostatic adsorption devices will not be described in detail here.

[0076] Specifically, the process of preheating the initial film 4 peeled from the cooling roller 3 uses a preheating roller group of 4 to 8 pieces; the stretching process uses a longitudinal stretching machine and a transverse stretching machine; the heat setting process uses an oven; and the cooling and winding process uses the cooling roller 3 and a dual-station surface center winding machine.

[0077] As will be understood by those skilled in the art, the operating principle and process of the equipment used in the process of preheating, stretching, heat setting and cooling winding of the initial film 4 peeled from the cooling roller 3 are conventional technical means well known to those skilled in the art. Therefore, the operating principle and process of the equipment used in the process of preheating, stretching, heat setting and cooling winding of the initial film 4 peeled from the cooling roller 3 will not be described in detail here.

[0078] In practice, this invention obtains the first dust distribution density on the outer wall of the hopper. If the first dust distribution density is greater than the second preset density, it indicates that the dust-containing airflow escapes through the connection of the hopper to the outer wall of the hopper. If the air velocity around the initial film 4 is greater than the preset velocity, it indicates that the high-temperature melt casting forms a molten sheet that heats the surrounding air, thereby forming an upward airflow. If the first dust distribution density is greater than the second preset density, the dust near the hopper and around the equipment is carried to the surface of the cooling roller 3 due to the low pressure of the upward airflow. The dust is then drawn into the initial film 4 by electrostatic adsorption. By reducing the relative horizontal distance between the die head 2 of the extruder 1 and the cooling roller 3, the angle at which the external ambient air enters between the cooling roller 3 and the die head 2 is reduced, thereby reducing the generated upward airflow. This weakens the strength and suction force of the upward airflow and reduces the ability of the upward airflow to carry dust from the area with abnormal first dust distribution density to the surface of the cooling roller 3.

[0079] Please see Figure 3The diagram shows a flowchart illustrating the adjustment of the relative horizontal distance between the die 2 and the cooling roller 3 of the extruder 1 in the co-extrusion production method of nylon and PE composite film according to an embodiment of the present invention. The adjustment of the relative horizontal distance between the die 2 and the cooling roller 3 of the extruder 1 based on the first dust distribution density and the surrounding air velocity includes:

[0080] The first dust distribution density is compared with the second preset density, and the air flow rate is compared with the preset flow rate;

[0081] If the first dust distribution density is greater than the second preset density, and the air velocity is greater than the preset velocity, then the relative horizontal distance between the die head 2 of the extruder 1 and the cooling roller 3 is reduced.

[0082] Specifically, the relative horizontal distance is adjusted by the linear guide rail, servo motor, and ball screw of the base below the extruder 1.

[0083] As will be understood by those skilled in the art, the operating principles and processes of linear guides, servo motors, and ball screws are conventional techniques well-known to them; therefore, the operating principles and processes of linear guides, servo motors, and ball screws will not be elaborated upon here.

[0084] Specifically, the relative horizontal distance is negatively correlated with the dust distribution density.

[0085] Optionally, the second preset density can be selected within a range of [0.5 mg / L]. 2.0mg / The preset flow rate can be selected within the range of [0.3m / s, 1.0m / s].

[0086] Preferably, the preferred embodiment of the second preset density is 1.0 mg / L. The preferred embodiment of the preset flow rate is 0.6 m / s.

[0087] In implementation, when the air velocity exceeds the preset velocity by less than 0.1 m / s, the relative horizontal distance between the die 2 of the extruder 1 and the cooling roller 3 is adjusted to 90% of the current relative horizontal distance. When the air velocity exceeds the preset velocity by more than 0.1 m / s, the relative horizontal distance is reduced by 0.05% for every 0.01 m / s exceeding the preset velocity. In a specific embodiment, the current air velocity is 0.83 m / s, and the current relative horizontal distance between the die 2 of the extruder 1 and the cooling roller 3 is 300 mm. The reduced relative horizontal distance is 300 mm × 0.9 - (1 - 0.65%) = 268.245 mm. When the calculated relative horizontal distance has more than two decimal places, it is rounded to the second decimal place, i.e., 268.25 mm.

[0088] In practice, this invention adjusts the relative horizontal distance between the die head 2 of the extruder 1 and the cooling roller 3 to be smaller when the first dust distribution density is higher. According to the law of particle movement, the dust diffuses a longer distance in the rising airflow formed by the high-temperature melt casting to heat the surrounding air. The probability of the dust eventually reaching the surface of the cooling roller 3 is greater. By reducing the dust diffusion distance, the straight distance that the dust needs to travel from the outer wall of the hopper to the surface of the cooling roller 3 is substantially shortened. This means that most of the dust falls or is carried away by the bypass airflow before it is effectively transported to the surface of the initial film 4 by the airflow, and cannot contact the film, thereby further reducing the amount of dust reaching the surface of the cooling roller 3.

[0089] Specifically, determining the shrinkage region of the initial film 4 based on the surface image of the initial film 4 includes:

[0090] The temperature reduction of the initial thin film 4 on the surface image is obtained;

[0091] The largest region enclosed by all sampling points whose temperature reduction is less than the preset temperature reduction is defined as the initial film 4 shrinkage region.

[0092] Optionally, the preset temperature reduction range is [5℃, 15℃].

[0093] Preferably, the preferred embodiment of the preset temperature reduction is 8°C.

[0094] Please see Figure 4 The diagram shows a flowchart of the process for determining abnormal dust distribution areas in the co-extrusion production method of nylon and PE composite films according to an embodiment of the present invention. The step of determining abnormal dust distribution areas based on a second dust distribution density above the initial film 4 includes:

[0095] Obtain the second dust distribution density located above the initial film 4;

[0096] The second dust distribution density is compared with the first preset density and the second preset density;

[0097] The largest area enclosed by all sampling points whose second dust distribution density is greater than the first preset density and less than or equal to the second preset density is defined as the dust distribution abnormal area.

[0098] Optionally, the first preset density can be selected within a range of [0.2 mg / L]. 0.4mg / ].

[0099] Preferably, the preferred embodiment of the first preset density is 0.3 mg / L. .

[0100] Specifically, the second preset density is greater than the first preset density.

[0101] Specifically, adjusting the peeling angle between the initial film 4 and the cooling roller 3 based on the overlap between the abnormal dust distribution area and the shrinkage area of ​​the initial film 4 includes:

[0102] The overlap between the abnormal dust distribution area and the shrinkage area of ​​the initial film 4 is compared with a preset overlap.

[0103] If the overlap is greater than the preset overlap, then the peeling angle between the initial film 4 and the cooling roller 3 is reduced.

[0104] In implementation, this invention defines the largest region enclosed by all sampling points on the surface image whose temperature decrease is less than a preset temperature decrease as the initial film 4 shrinkage region, and obtains the second dust distribution density above the initial film 4 within a unit period. If the second dust distribution density is greater than the first preset density and less than or equal to the second preset density, it indicates that dust is more easily trapped in the initial film 4 during cooling and shrinkage, thereby enhancing the surface roughness of the initial film 4 with trapped dust. This enhances the surface roughness of the initial film 4, causing it to carry additional electrostatic charge when peeled off from the cooling roller 3. Consequently, the traction stress on the traction roller increases when the initial film 4 peels off from the cooling roller 3. This reduces the initial film... The angle between the tangent of the initial film 4 along the surface of the cooling roller 3 at the separation line of the cooling roller 3 and the extension of the radius of the cooling roller 3 at the separation point reduces the vertical height of the initial film 4 on the cooling roller 3 during the peeling process caused by the increased traction stress on the traction roller. This transforms the traction stress perpendicular to the surface of the cooling roller 3 into a force parallel to the surface of the cooling roller 3, further reducing the stress concentration phenomenon of the initial film 4 at the peeling point. This makes the peeling process of the initial film 4 smoother, reduces the friction intensity and static electricity generation rate during the peeling process, and thus offsets the negative impact of the increased surface roughness of the initial film 4 due to dust trapping. This ensures that the traction stress is restored to the set level required for stable production and improves the production efficiency of the composite film.

[0105] Specifically, the overlap is the ratio of the area of ​​the abnormal dust distribution region to the area of ​​the shrinkage region of the initial film 4.

[0106] Specifically, the peeling angle between the initial film 4 and the cooling roller 3 is negatively correlated with the degree of overlap.

[0107] Optionally, the preset overlap range is [20%, 50%].

[0108] Preferably, the preferred embodiment with a preset overlap ratio is 30%.

[0109] In practice, when the overlap exceeds the preset overlap value by less than 10%, the peel angle between the initial film 4 and the cooling roller 3 is adjusted to 90% of the current peel angle. When the overlap exceeds the preset overlap value by more than 10%, the peel angle is reduced by 0.05% for every 0.05% exceeding 1%. In a specific embodiment, the current overlap is 48%, the current peel angle between the initial film 4 and the cooling roller 3 is 30°, and the reduced peel angle is 30° × 0.9 - (1 - 8%) = 24.84°. When the calculated peel angle has more than two decimal places, it is rounded to the second decimal place.

[0110] Specifically, the peel angle between the initial film 4 and the cooling roller 3 is changed by adjusting the rollers that guide the initial film 4 away from the cooling roller 3 on a sliding base, thereby changing the horizontal and vertical position of the rollers relative to the cooling roller 3 by adjusting the bolts, screws, or hydraulic cylinders of the rollers.

[0111] As will be understood by those skilled in the art, the operating principles and processes of the roller and the bolts, lead screws and hydraulic cylinders inside the roller are conventional technical means well known to those skilled in the art. Therefore, the operating principles and processes of the roller and the bolts, lead screws and hydraulic cylinders inside the roller will not be described in detail here.

[0112] In implementation, the present invention adjusts the peeling angle between the initial film 4 and the cooling roller 3 to be smaller when the ratio of the area of ​​the abnormal dust distribution region to the area of ​​the shrinkage region of the initial film 4 is larger. The shrinkage region of the initial film 4 represents the region where the initial film 4 generates shrinkage stress due to uneven cooling; the abnormal dust distribution region represents the region where dust floats and dust may settle. When the ratio of the area of ​​the abnormal dust distribution region to the area of ​​the shrinkage region of the initial film 4 is larger, it means that the probability of dust settling in the region where the initial film 4 generates shrinkage stress due to uneven cooling is greater. By reducing the glass angle between the initial film 4 and the cooling roller 3 as the degree of overlap increases, the traction stress on the traction roller is evenly distributed, thereby avoiding the region where dust floats and dust may settle.

[0113] Specifically, the peeling angle between the initial film 4 and the cooling roller 3 is the angle between the tangent of the initial film 4 along the surface of the cooling roller 3 at the separation line between the initial film 4 and the cooling roller 3 and the plane containing the separation line and the central axis of the cooling roller 3.

[0114] Working process: The first hopper 7 and the second hopper 8 temporarily store raw material particles respectively. The first feeding pipe 9 and the second feeding pipe 10 cooperate with the feeding device at the bottom of the hopper to stably transport the raw material particles to the feeding port of the extruder 1, continuously supplying raw materials of different components to the extruder 1. Through the sectional heating of the barrel and the shearing and compression effects of the screw, the extruder 1 gradually plasticizes and mixes the solid raw material particles, and finally melts them into a uniform melt, ensuring the full fusion of raw materials of different components. The melt conveying pipe承接 the melt output by the extruder 1 and maintains the stable state of the melt under the action of the external heating and heat preservation device, and transports it to the die head 2; The die head 2 evenly extrudes the melt through the streamlined flow channel and adjustable lip, forming a continuous molten thick sheet. The cooling roll 3 is arranged below the die head 2, and the temperature of the roll surface of the cooling roll 3 is reduced by passing cooling water inside; At the same time, the electrostatic adsorption device配套 with the cooling roll 3 generates an adsorption force through corona discharge, tightly adsorbing the extruded molten thick sheet on the surface of the cooling roll 3. The thick sheet is cooled and shaped on the roll surface to form the initial film 4. The thermal wind speed sensor 5 continuously detects the air flow velocity around the initial film 4 to determine whether there is an air flow disturbance that may entrain dust; The dust detection component synchronously monitors the second dust distribution density above the initial film 4 to identify whether there is an abnormal area of dust distribution density; The industrial camera 6 continuously captures the surface morphology of the initial film 4 to locate the shrinkage area of the film. If it is detected that the first dust distribution density exceeds the second preset density and the air flow velocity exceeds the preset velocity, the relative horizontal distance between the die head 2 of the extruder 1 and the cooling roll 3 is adjusted to reduce the angle of the external ambient air entering between the cooling roll 3 and the die head 2, thereby reducing the generated upward air flow, weakening the intensity and suction force of the upward air flow, reducing the ability of the upward air flow to carry the dust on the outer wall of the hopper to the surface of the cooling roll 3, and reducing the probability of dust being entrained by the air flow. After a unit cycle, if it is detected that the coincidence degree between the dust abnormal area and the film shrinkage area exceeds the preset coincidence degree, it is determined that the static electricity amount when the initial film 4 is peeled off is abnormal, and the peeling angle between the initial film 4 and the cooling roll 3 is further adjusted to evenly disperse the traction stress received by the traction roll, so as to avoid the areas where dust floats and dust may settle. After cooling and shaping and parameter adjustment, the initial film 4 enters the subsequent processes such as preheating, stretching, and shaping, and is finally processed into a nylon / PE composite film product that meets the performance requirements.

[0115] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims

1. A method for co-extruding a nylon / PE composite film, characterized in that, include: Each type of raw material particle obtained after sieving is loaded into the corresponding hopper, and each type of raw material particle is heated and extruded in sequence to obtain an initial film. The first dust distribution density on the outer wall of the hopper and the air velocity around the initial film are obtained respectively. The relative horizontal distance between the extruder die and the cooling roller is adjusted based on the first dust distribution density and the surrounding air velocity. Obtain an initial surface image of the film on the cooling roller after adjusting the relative horizontal distance; The initial film shrinkage region is determined based on the surface image of the initial film. The dust distribution anomaly region is determined based on the second dust distribution density above the initial film; Adjust the peeling angle between the initial film and the cooling roller based on the degree of overlap between the abnormal dust distribution area and the initial film shrinkage area; The initial film continues to be extruded according to the peel angle between the initial film and the cooling roller; The initial film peeled from the cooling roller is sequentially preheated, stretched, heat-set, and cooled and wound up to form a nylon and PE composite film.

2. The co-extrusion production method of nylon and PE composite film according to claim 1, characterized in that, The adjustment of the relative horizontal distance between the extruder die and the cooling roller based on the first dust distribution density and the surrounding air velocity includes: The first dust distribution density is compared with the second preset density, and the air flow rate is compared with the preset flow rate; If the first dust distribution density is greater than the second preset density, and the air velocity is greater than the preset velocity, then the relative horizontal distance between the extruder die and the cooling roller is reduced.

3. The co-extrusion production method of nylon and PE composite film according to claim 2, characterized in that, The relative horizontal distance is negatively correlated with the first dust distribution density.

4. The co-extrusion production method of nylon and PE composite film according to claim 3, characterized in that, The step of determining the initial film shrinkage region based on the surface image of the initial film includes: Obtain the temperature reduction of the initial thin film on the surface image; The largest region enclosed by all sampling points whose temperature reduction is less than the preset temperature reduction is defined as the initial film shrinkage region.

5. The co-extrusion production method of nylon and PE composite film according to claim 4, characterized in that, The determination of anomalous dust distribution regions based on a second dust distribution density above the initial film includes: Obtain the second dust distribution density located above the initial film; The second dust distribution density is compared with the first preset density and the second preset density; The largest area enclosed by all sampling points whose second dust distribution density is greater than the first preset density and less than or equal to the second preset density is defined as the dust distribution abnormal area.

6. The co-extrusion production method of nylon and PE composite film according to claim 5, characterized in that, The second preset density is greater than the first preset density.

7. The co-extrusion production method of nylon and PE composite film according to claim 6, characterized in that, The step of adjusting the peel angle between the initial film and the cooling roller based on the overlap between the dust distribution abnormality area and the initial film shrinkage area includes: The overlap between the abnormal dust distribution area and the initial film shrinkage area is compared with a preset overlap. If the overlap is greater than the preset overlap, then the peeling angle between the initial film and the cooling roller is reduced.

8. The co-extrusion production method of nylon and PE composite film according to claim 7, characterized in that, The overlap is the ratio of the area of ​​the abnormal dust distribution region to the area of ​​the initial film shrinkage region.

9. The co-extrusion production method of nylon and PE composite film according to claim 8, characterized in that, The peel angle between the initial film and the cooling roller is negatively correlated with the degree of overlap.

10. The co-extrusion production method of nylon and PE composite film according to claim 9, characterized in that, The peel angle between the initial film and the cooling roller is the angle between the tangent of the initial film along the surface of the cooling roller at the separation line between the initial film and the cooling roller and the plane containing the separation line and the central axis of the cooling roller.

Images