Multilayer co-extrusion blown film production apparatus and process

Abstract

A kind of multilayer co-extrusion blown film production equipment, including blown film head, blown film head is equipped with circular ring converging runner and several sets of material spreading runner, the material spreading runner corresponding to outermost layer molten material includes circular ring outermost layer material leakage slit cavity, the near heart section of outermost layer material leakage slit cavity has the taper of upper small lower big, outermost layer material leakage slit cavity is equipped with first filling piece, and first filling piece inclined section is located in the near heart section of outermost layer material leakage slit cavity inside;The material spreading runner corresponding to innermost layer molten material includes circular ring innermost layer material leakage slit cavity, the far heart section of innermost layer material leakage slit cavity has the taper of upper big lower small, innermost layer material leakage slit cavity is equipped with second filling piece, and second filling piece inclined section is located in the far heart section of innermost layer material leakage slit cavity inside.The film bubble produced by the application outermost layer plastic and innermost layer plastic partial loss, to meet the special needs such as welding.The application also provides a kind of multilayer co-extrusion blown film production process.

Description

Technical Field

[0001] This invention belongs to the technical field of plastic film production and processing equipment and processes, specifically relating to a multi-layer co-extrusion blown film production equipment and its production process. Background Technology

[0002] Multi-layer co-extrusion blown film production equipment is used to co-extrude multiple layers of molten plastic to form a plastic film bubble with a multi-layer composite structure. The multi-layer co-extrusion blown film production equipment is equipped with a blown film die head, which includes an annular extrusion port, an annular confluence channel, and several sets of material spreading channels. Each set of material spreading channels is used to guide the flow of the corresponding layer of molten plastic material (hereinafter referred to as molten material) and spread the molten material into an annular shape. The downstream end of each set of material spreading channels is connected to the annular confluence channel, and the annular confluence channel is connected to the annular extrusion port.

[0003] During the production of multi-layer co-extrusion blown film, the extruder melts various plastic raw materials into molten materials and extrudes them into the blown film head. The various molten materials gradually spread out in the corresponding material spreading channels in the blown film head along the circumference of the blown film head to form a ring. Then, the various molten materials converge in the ring converging channel and flow to be extruded together from the ring extrusion port to form a multi-layer composite cylindrical film bubble. Then, the cylindrical film bubble is cut along the longitudinal direction (i.e., parallel to the central axis of the film bubble) to obtain sheet plastic film.

[0004] In order to spread the molten material into a ring shape, there are two main structural forms of the material spreading channel of the blown film die head: the first structural form is a spiral groove channel, and the second structural form is a horizontal vortex channel.

[0005] The internal structure and working principle of the first structural form (spiral groove flow channel form) are as follows: Figure 1 , Figure 2 As shown, it has several layers of inner and outer nested, concentrically arranged sleeves 82. Each layer of sleeve 82 is cylindrical, and an annular gap 80 is formed between the circumferential sides of each pair of adjacent inner and outer sleeves 82. The downstream end of the annular gap 80 connects to an annular confluence channel. Several spiral groove channels 81 are also chiseled into the surface of the annular gap between each pair of adjacent sleeves 82, and each spiral groove channel 81 is evenly distributed along the circumference of the sleeve. During the production process, the high-temperature molten material rotates and rises along each spiral groove channel 81. During the rotation and upward flow along the spiral groove channels 81, the molten material also continuously leaks upward from the annular gap 80 between each pair of sleeves (i.e., leaks out from the spiral groove channels 81 and flows upward into the annular gap 80 between the two sleeves, hence the term leakage), such as... Figure 2As shown by the arrow, the molten material is gradually spread out along the circumference of the blown film head to form a ring, then flows into the ring-shaped confluence channel 16, and finally is extruded from the ring-shaped extrusion port 15.

[0006] The internal structure and working principle of the second structural form (horizontal vortex channel form) are as follows: Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown, it has stacked modules 72, with a vertical gap between the upper and lower modules 72. This vertical gap forms an annular material leakage cavity 70 ("annular" means that the horizontal projection shape is circular, and because the cavity is thin and flat, like a slit, it is called a "cavity"). Several horizontal vortex channels 71 are also formed on the surface of the material leakage cavity 70, and each horizontal vortex channel 71 is evenly distributed along the circumference of the blown film head; one side of the material leakage cavity (e.g.) Figure 3 The inner edge of the blown film head (close to the central axis) connects to the annular confluence channel; the other side of the material leakage cavity (such as...) Figure 3 The outer edge is closed, located away from the central axis of the blown film head. During production, the high-temperature molten material flows along each horizontal vortex channel 71. While flowing along the horizontal vortex channels 71, the molten material also continuously leaks from the horizontal vortex channels 71 into the material leakage cavity 70 (i.e., leaks out from the horizontal vortex channels 71 and flows into the vertical gap between the upper and lower modules 72, hence the term leakage). Figure 5 As indicated by the arrow, the molten material is gradually spread out in a ring along the circumference of the material leakage cavity 70, and then flows into the ring-shaped converging channel 16. The number of horizontal vortex channels 71 on the surface of each material leakage cavity 70 can be four, eight, sixteen, etc. Figure 5 , Figure 4 For the sake of simplicity, only four lines are drawn.

[0007] From a horizontal projection perspective, if the aforementioned "horizontal vortex channel" is placed in a planar polar coordinate system, with the projection point of the central axis of the blown film die head as the center of this polar coordinate system, and the direction of the molten material flowing forward in the channel as the direction of increasing polar angle, then the extreme diameter of the channel continuously decreases or increases with the increase of the polar angle, forming a spiral-like shape, hence the name "vortex channel"; and because the "vortex channel" is located on a horizontal plane, it is called a "horizontal vortex channel." If the extreme diameter of the channel decreases with the increase of the polar angle, such as... Figure 3 , Figure 4 , Figure 5As shown, its starting point 710 is located at the outer edge of the material leakage cavity 70. The molten material continuously moves inwards during its advancement within the horizontal vortex channel 71, hence it is called an "inner vortex horizontal vortex channel." Conversely, if the extreme diameter of the channel increases with the increase of the polar angle, it is called an "outer vortex horizontal vortex channel," as shown. Figure 6 As shown in the figure, the outer spiral horizontal vortex flow channel 11 has its starting point 110 located at the inner edge of the material leakage cavity 10. The molten material moves towards the outside as it advances in the outer spiral horizontal vortex flow channel 11. The outer edge of the material leakage cavity corresponding to the outer spiral horizontal vortex flow channel 11 is connected to the annular confluence flow channel 16, while its inner edge is closed.

[0008] In the prior art, the second structural form (horizontal vortex flow channel form) has multiple layers stacked on top of each other. Each module is either located inside the annular confluence flow channel or outside the annular confluence flow channel. Therefore, in the same multi-layer co-extrusion blown film production equipment, the horizontal vortex flow channels are either all internally swirling or all externally swirling.

[0009] The film produced by blown film production equipment can be used as agricultural film, which is divided into mulch film and greenhouse film. Multi-layer composite agricultural film can have five or seven layers in structure. The plastic layer on the surface of the agricultural film is called the surface layer. Because the surface of the agricultural film has two sides (i.e., the upper surface and the lower surface), it has two surface layers. These two surface layers correspond to the innermost layer and the outermost layer in the uncuttered cylindrical film bubble shape.

[0010] In recent years, agricultural films with PA (polyamide) material on both sides have been developed. These films have superior performance and advantages: First, PA material has good self-cleaning and dust-proof properties, ensuring the film's light transmittance even after long-term use; second, PA film has good mechanical properties, extending its lifespan by about two years (compared to polyethylene film); third, PA material has better gas barrier properties than polyethylene film, resulting in better heat preservation and benefiting crop production inside the greenhouse.

[0011] However, agricultural films with both sides made of PA material (polyamide) also have the following problems: The width required for typical greenhouse films often exceeds ten meters, while the width of a single agricultural film obtained by blown film is only 3.14 times the diameter of the inflated film bubble. However, the diameter of the film bubble (after inflation) containing PA material on both sides is generally limited by various factors and rarely exceeds about 10 meters. Therefore, when using blown film as agricultural greenhouse film, multiple plastic film sheets need to be welded together horizontally. However, PA material (polyamide) has a high melting point, long heat-sealing time, and poor welding performance, making it unsuitable for automatic machine welding. Therefore, despite its many excellent properties, the aforementioned film with PA material on both sides is currently mostly used as mulch film, and promoting its use as greenhouse film remains difficult, becoming a bottleneck problem. Summary of the Invention

[0012] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a multi-layer co-extrusion blown film production equipment and its production process, in which the outermost and innermost plastic layers of the produced film bubble are partially missing to meet special requirements such as welding.

[0013] The objective can be achieved as follows: A multi-layer co-extrusion blown film production equipment is used to co-extrude multiple layers of molten material to form a plastic film bubble with a multi-layer composite structure. The equipment includes a blown film head, which is provided with an annular extrusion port, an annular converging channel, and several sets of material spreading channels. Each set of material spreading channels guides the flow of one layer of molten material and spreads the molten material into an annular shape. The downstream end of each set of material spreading channels is connected to the annular converging channel, and the annular converging channel is connected to the annular extrusion port. The material spreading channel corresponding to the outermost layer of molten material includes an annular outermost material leakage cavity. This outermost material leakage cavity is formed by an annular upper module and an annular lower module sandwiched together. The upper module is located above the lower module, and there is a vertical gap between the inner parts of the upper module and the inner parts of the lower module. This vertical gap forms the outermost material leakage cavity. The outer edge of the outermost material leakage cavity is closed, and the inner edge of the outermost material leakage cavity is connected to the annular converging channel. Several inward-swirling horizontal vortex channels are also formed on the surface of the outermost material leakage cavity. The outermost material leakage cavity is characterized by: the proximal section having a tapered shape with a smaller upper section and a larger lower section; the portion of the outermost material leakage cavity other than the proximal section is called the main body section of the outermost material leakage cavity; the outermost material leakage cavity is provided with a first plugging piece, which includes an inclined section and a horizontal section of the first plugging piece that are connected as one piece; the inclined section of the first plugging piece is located inside the proximal section of the outermost material leakage cavity, and the horizontal section of the first plugging piece is located inside the main body section of the outermost material leakage cavity; The material spreading channel corresponding to the innermost molten material includes an annular innermost material leakage cavity, which is formed by an annular upper inner module and an annular lower inner module sandwiched together. The upper inner module is located above the lower inner module, and the lower outer module is located around the lower inner module. The upper outer module is located around the upper inner module. There is a vertical gap between the outer parts of the upper inner module and the outer parts of the lower inner module, which forms the innermost material leakage cavity. The outer edge of the innermost material leakage cavity is connected to the annular converging channel, and the inner edge of the innermost material leakage cavity is closed. Several outward-swirling horizontal vortex channels are also formed on the surface of the innermost material leakage cavity. The distal section of the innermost material leakage cavity has a tapered shape, wider at the top and narrower at the bottom. The portion of the innermost material leakage cavity excluding the distal section is called the main body section of the innermost material leakage cavity. The innermost material leakage cavity is equipped with a second packing plate, which includes an integrally connected inclined section and a horizontal section. The inclined section is located inside the distal section of the innermost material leakage cavity, and the horizontal section is located inside the main body section of the innermost material leakage cavity. The second packing plate and the first packing plate are in the same orientation relative to the central axis of the blown film head.

[0014] The circumferential dimension of the first packing piece is 8–30 cm, and the circumferential dimension of the second packing piece is 8–30 cm.

[0015] The multi-layer co-extrusion blown film production equipment is a seven-layer co-extrusion blown film production equipment. Between the inner lower annular module and the outer lower annular module, a first sleeve, a second sleeve, a third sleeve, and a fourth sleeve are sequentially installed from the inside to the outside. The inner lower module, the first sleeve, the second sleeve, the third sleeve, the fourth sleeve, and the outer lower module are collectively referred to as sleeves. The vertical central axis of each sleeve is in the same position. The upper end face of the first sleeve and the second sleeve has an inverted taper that is larger at the top and smaller at the bottom, while the upper end face of the third sleeve and the fourth sleeve has a positive taper that is smaller at the top and larger at the bottom. An annular gap is formed between each pair of adjacent inner and outer sleeves. Several spiral groove flow channels are also formed on the surface of the annular gap between each pair of adjacent inner and outer sleeves. The annular gap and the spiral groove flow channels between each pair of adjacent sleeves form a material spreading channel for a layer of molten material. The annular merging channel includes an annular vertical merging channel, an annular conical merging channel, and an annular inverted conical merging channel. These three channels form an inverted Y-shape in the radial cross-section. The annular inverted conical merging channel is formed by the annular gap between the lower part of the inner upper module and the upper end face of the second sleeve. The annular conical merging channel is formed by the annular gap between the lower part of the outer upper module and the upper end face of the third sleeve. There is a radial gap between the upper part of the outer upper module and the upper part of the inner upper module, which forms part of the annular vertical merging channel. The outer edge of the innermost material leakage cavity is directly connected to the lower end of the annular inverted cone confluence channel. The upper end of the annular gap between the inner lower module and the first sleeve is directly connected to the lower end of the annular inverted cone confluence channel. The upper end of the annular gap between the first sleeve and the second sleeve is directly connected to the lower end of the annular inverted cone confluence channel. The upper end of the annular gap between the second sleeve and the third sleeve is connected to the lower end of the annular vertical confluence channel. The upper end of the annular gap between the third sleeve and the fourth sleeve is directly connected to the lower end of the annular positive cone confluence channel. The upper end of the annular gap between the fourth sleeve and the outer lower module is directly connected to the lower end of the annular positive cone confluence channel. The inner edge of the outermost material leakage cavity is directly connected to the lower end of the annular positive cone confluence channel.

[0016] An outer port module is provided above the outer upper module, and an inner port module is provided above the inner upper module. There is a radial gap between the outer port module and the inner port module, which forms the upper section of the annular vertical confluence channel. The radial gap between the upper part of the outer upper module and the upper part of the inner upper module forms the lower section of the annular vertical confluence channel.

[0017] A multi-layer co-extrusion blown film production process, using the aforementioned multi-layer co-extrusion blown film production equipment, includes the following steps: (1) Each layer of molten plastic flows into a corresponding set of material spreading channels and spreads out into a ring; among them, the outermost layer of molten plastic flows from the starting point of each inner swirling horizontal vortex channel along the inner swirling horizontal vortex channel. During this process, the outermost layer of molten plastic also leaks into the outermost material leakage cavity next to the inner swirling horizontal vortex channel, so that the outermost layer of molten plastic is spread out (unfolded) into a ring. However, when the outermost layer of molten plastic approaches the inner edge of the outermost material leakage cavity, the outermost layer of molten plastic is missing in the corresponding position due to the occupation of the first filling piece. The innermost layer of molten plastic flows from the starting point of each outer spiral horizontal vortex channel along the outer spiral horizontal vortex channel. During this process, the innermost layer of molten plastic also leaks into the innermost material leakage cavity next to the outer spiral horizontal vortex channel, causing the innermost layer of molten plastic to be spread out (unfolded) into a ring. However, when the innermost layer of molten plastic approaches the outer edge of the innermost material leakage cavity, the innermost layer of molten plastic is missing in the corresponding position due to the occupation of the second packing piece. (2) The molten plastic layers of each layer flow into the annular confluence channel and are finally extruded from the annular extrusion port to form a membrane bubble. The resulting membrane bubble has a multi-layer plastic composite structure. The outermost plastic layer is missing in the position corresponding to the first filler piece, and the innermost plastic layer is missing in the position corresponding to the second filler piece. The missing parts of the outermost plastic layer and the missing parts of the innermost plastic layer are in the same position (i.e., overlapping).

[0018] The outermost molten plastic is polyamide, and the innermost molten plastic is polyamide. The resulting cylindrical film bubble is longitudinally cut open, with the cutting line located in the middle of the missing parts of the innermost and outermost plastic layers, transforming the cylindrical film bubble into a sheet-like plastic film. The sheet-like plastic film is transversely cut into multiple plastic films, and the edges of the different plastic films are overlapped and welded together. In every two welded plastic films, the welded part of the first plastic film is located at the missing part of the innermost plastic layer, and the welded part of the second plastic film is located at the missing part of the outermost plastic layer.

[0019] The terms "downstream" and "upstream" are defined based on the direction of the molten material's flow, with the molten material flowing from upstream to downstream. In multi-layer co-extrusion blown film production equipment, the film bubble is extruded upwards, and the final stage of the molten material's flow is upwards. Therefore, in components where the molten material flows upwards, the upstream end refers to the lower end, and the downstream end refers to the upper end.

[0020] The direction of inside and outside is defined as the direction closer to the central axis of the blown film extruder head (i.e., the vertical central axis of the annular extrusion port) and the direction farther away from the central axis of the blown film extruder head.

[0021] A regular cone is a cone that is smaller at the top and larger at the bottom; an inverted cone is a cone that is larger at the top and smaller at the bottom.

[0022] A positive taper is a taper that is smaller at the top and larger at the bottom; an inverted taper is a taper that is larger at the top and smaller at the bottom.

[0023] The term "distal section" refers to the section that is far from the central axis of the blown film head; the term "proximal section" refers to the section that is close to the central axis of the blown film head.

[0024] The term "radial" refers to the radial direction of the blown film head.

[0025] The circumferential dimension of the packing sheet refers to the dimension of the packing sheet along the circumference of the blown film head. This value determines the curvature of the space occupied by the packing sheet in the annular material leakage cavity, and thus determines the circumferential length of the missing part of the innermost (outer) layer of molten plastic in the film bubble.

[0026] The longitudinal direction of a vesicle refers to the direction parallel to the central axis of the vesicle.

[0027] The present invention has the following advantages and effects: I. This invention can produce a membrane bubble with a multi-layered plastic composite structure, wherein the outermost plastic layer is missing at the position corresponding to the first filler piece, and the innermost plastic layer is partially missing at the position corresponding to the second filler piece, to meet specific needs. Furthermore, when both the outermost and innermost plastic layers are polyamide, the sheet-like plastic film obtained after cutting the membrane bubble along the missing polyamide material is easy to weld. The resulting multi-layered composite film retains the advantages of polyamide layers—good self-cleaning properties, good mechanical properties, and good heat insulation—while avoiding the disadvantages of polyamide being difficult to weld, making it suitable for widespread application as an agricultural greenhouse film.

[0028] 2. The material spreading channels corresponding to the outermost and innermost molten materials adopt a horizontal vortex flow channel form, which means that the corresponding modules are stacked one on top of the other. The distal section of the innermost material leakage cavity has a tapered shape that is larger at the top and smaller at the bottom, and the proximal section of the outermost material leakage cavity has a tapered shape that is smaller at the top and larger at the bottom. The inclined section of the first (second) packing plate is located inside the tapered section of the material leakage cavity, and the horizontal section of the first (second) packing plate is located inside the main body section of the material leakage cavity. This structure further brings the following advantages: 1. Once the packing plate is installed in place, it can be fixed at the bend without any additional reinforcement measures (e.g., no threaded locking measures are needed, or no locking measures using convex and concave fit to embed into the flow channel surface), and can withstand the extrusion pressure without displacement; 2. No additional fixing measures are required during the installation of the packing plate. Specifically, even when the upper module has not yet been installed in place (meaning that the upper and lower modules have not yet been able to clamp and fix the packing plate), the packing plate can still be stably placed on the upper surface of the lower module without shifting or falling off. Then the upper module is installed on the packing plate. Therefore, the installation and positioning process of the packing plate is simple. 3. When needed, the packing sheet can be removed to produce ordinary film bubbles that do not require localized missing material in the surface layer; and since the packing sheet does not require any additional fixing measures, it means that the flow channel surface remains smooth after the packing sheet is removed (in other words, if the installation of the packing sheet requires threaded locking measures or convex-concave mating clamping measures, then when the packing sheet is removed, the flow channel surface will inevitably be locally rough, which will cause the molten material to flow poorly on the rough local surface, resulting in crystallization, degradation or even scorching). Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the cross-sectional structure of a traditional blown film machine head that uses a spiral groove flow channel.

[0030] Figure 2 This is a schematic diagram illustrating the working principle of the spiral groove flow channel in the blown film machine head.

[0031] Figure 3This is a schematic diagram of the cross-sectional structure of a traditional blown film extruder head that uses an internally rotating horizontal vortex flow channel.

[0032] Figure 4 yes Figure 3 A schematic diagram of the three-dimensional structure of one of the modules.

[0033] Figure 5 yes Figure 4 A schematic diagram of the horizontal projection structure of the module shown.

[0034] Figure 6 This is a schematic diagram of the horizontal projection structure of a module that uses an externally rotating horizontal vortex flow channel.

[0035] Figure 7 This is a cross-sectional structural diagram of a specific embodiment of the present invention.

[0036] Figure 8 yes Figure 7 A magnified view of the upper left corner of the image.

[0037] Figure 9 yes Figure 8 A simplified schematic diagram of the structure shown.

[0038] Figure 10 yes Figure 7 A magnified view of part A in the diagram.

[0039] Figure 11 yes Figure 7 A schematic diagram showing the horizontal projection positions of the first and second packing pieces in the entire blown film head.

[0040] Figure 12 This is a schematic diagram of the three-dimensional shape of the first packing piece.

[0041] Figure 13 This is a schematic diagram of the horizontal projection shape of the first packing piece.

[0042] Figure 14 This is a schematic diagram of the side shape of the second packing piece. Detailed Implementation Example 1

[0043] Figure 7 , Figure 8 , Figure 9The seven-layer co-extrusion blown film production equipment shown is used to co-extrude seven layers of molten material to form a plastic film bubble with a seven-layer composite structure. It includes a blown film head, which is provided with an annular extrusion port 15, an annular converging channel and seven sets of material spreading channels. Each set of material spreading channels guides the flow of one layer of molten material and spreads the molten material into an annular shape. The downstream end of each set of material spreading channels is connected to the annular converging channel, and the annular converging channel is connected to the annular extrusion port 15. Figure 7 , Figure 8 , Figure 9 , Figure 10 As shown, the material spreading channel corresponding to the outermost molten material includes an annular outermost material leakage cavity 70. The outermost material leakage cavity 70 is formed by an annular upper outer module 8 and an annular lower outer module 6 sandwiched together. The upper outer module 8 is located above the lower outer module 6. There is a vertical gap between the inner part of the upper outer module 8 and the inner part of the lower outer module 6. This vertical gap forms the outermost material leakage cavity 70. The outer edge of the outermost material leakage cavity 70 (in Figure 9 The annular edge where point B is located is closed, and the inner edge of the outermost material leakage cavity 70 (in) Figure 9 The annular confluence channel (where point D is located) connects to the outermost material leakage cavity 70; multiple internally swirling horizontal vortex channels 71 are also formed on the surface of the outermost material leakage cavity 70; each internally swirling horizontal vortex channel 71 is evenly distributed along the circumference of the blown film head, and the shape and structure of the internally swirling horizontal vortex channels can be found in [reference needed]. Figure 4 , Figure 5 ; The proximal segment 702 of the outermost material leakage cavity (in) Figure 9 The middle section (CD segment) has a tapered shape, smaller at the top and larger at the bottom. The outermost material leakage cavity, excluding the proximal section, is called the outermost material leakage cavity main body section 701 (in... Figure 9 (The middle section is segment BC). Figure 7 , Figure 10 As shown, the outermost material leakage cavity 70 is provided with a first packing piece 91, the shape of which is as follows: Figure 12 , Figure 13 As shown, the first packing piece 91 has a circumferential dimension of 20 cm. The first packing piece 91 includes an integrally connected inclined section 912 and a horizontal section 911. The inclined section 912 is located inside the proximal section 702 of the outermost material leakage cavity, and the horizontal section 911 is located inside the main body section 701 of the outermost material leakage cavity. Figure 11 , Figure 10 , Figure 7 As shown; Figure 7 , Figure 8 , Figure 9 , Figure 10 As shown, the material spreading channel corresponding to the innermost layer of molten material includes an annular innermost material leakage cavity 10. This innermost material leakage cavity 10 is formed by an annular upper inner module 7 and an annular lower inner module 5 sandwiched together. The upper inner module 7 is located above the lower inner module 5. The annular lower outer module 6 is located around the annular lower inner module 5, and the annular upper outer module 8 is located around the annular upper inner module 7. A vertical gap exists between the outer portion of the upper inner module 7 and the outer portion of the lower inner module 5, forming the innermost material leakage cavity 10. The outer edge of the innermost material leakage cavity 10 (in...) Figure 9 The innermost material leakage cavity 10 has an inner edge (where point E is located on the circular edge of the annular flow channel) connecting to the circular confluence channel. Figure 9 The annular edge where point G is located is closed; multiple externally rotating horizontal vortex channels 11 are formed on the surface of the innermost material leakage cavity. Each externally rotating horizontal vortex channel 11 is evenly distributed along the circumference of the blown film head. The shape and structure of the externally rotating horizontal vortex channels can be found in [reference needed]. Figure 6 ; The distal segment 102 of the innermost material leakage cavity (in) Figure 9 The middle section (EF segment) has a tapered shape, wider at the top and narrower at the bottom. The innermost material leakage cavity, excluding the distal section, is called the main body section 101 of the innermost material leakage cavity. Figure 9 The middle section is FG); the innermost material leakage cavity 10 is provided with a second packing piece 92, the circumferential dimension of the second packing piece 92 is 20 cm, the second packing piece 92 includes a second packing piece inclined section 922 and a second packing piece horizontal section 921 that are connected as one piece, such as Figure 14 As shown, the inclined section 922 of the second packing piece is located inside the distal section 102 of the innermost material leakage cavity, and the horizontal section 921 of the second packing piece is located inside the main body section 101 of the innermost material leakage cavity, as... Figure 14 , Figure 10 , Figure 11 , Figure 7 As shown; Figure 11 , Figure 7 As shown, there is one second packing piece 92 and one first packing piece 91. The second packing piece 92 and the first packing piece 91 are in the same orientation relative to the central axis of the blown film head. The second packing piece 92 and the first packing piece 91 have symmetrical and identical shapes and structures.

[0044] Figure 7 , Figure 8 , Figure 9 , Figure 10As shown, between the inner lower module 5 and the outer lower module 6 of the annulus, a first sleeve 1, a second sleeve 2, a third sleeve 3, and a fourth sleeve 4 are sequentially sleeved from the inside to the outside. The upper end faces of the first sleeve 1 and the second sleeve 2 have an inverted taper that is larger at the top and smaller at the bottom, while the upper end faces of the third sleeve 3 and the fourth sleeve 4 have a positive taper that is smaller at the top and larger at the bottom. The inner lower module 5, the first sleeve 1, the second sleeve 2, the third sleeve 3, the fourth sleeve 4, and the outer lower module 6 are collectively referred to as sleeves. The vertical central axis of each sleeve is at the same position, and an annular gap is formed between each pair of adjacent inner and outer sleeves. Multiple spiral groove channels are also carved into the surface of the annular gap between each pair of adjacent inner and outer sleeves. These spiral groove channels are evenly distributed along the circumference of each pair of adjacent sleeves. The annular gap and spiral groove channels between each pair of adjacent sleeves form a material spreading channel for a corresponding layer of molten material. Specifically, the annular gap 20 and the spiral groove channels between the inner lower module 5 and the first sleeve 1... 21 forms a material spreading channel for the second layer of molten material; the annular gap 30 and the spiral groove channel 31 between the first sleeve 1 and the second sleeve 2 form a material spreading channel for the third layer of molten material; the annular gap 40 and the spiral groove channel 41 between the second sleeve 2 and the third sleeve 3 form a material spreading channel for the fourth layer of molten material; the annular gap 50 and the spiral groove channel 51 between the third sleeve 3 and the fourth sleeve 4 form a material spreading channel for the fifth layer of molten material; the annular gap 60 and the spiral groove channel 61 between the fourth sleeve 4 and the outer lower module 6 form a material spreading channel for the sixth layer of molten material. The annular merging channel includes an annular vertical merging channel, an annular conical merging channel 14, and an annular inverted conical merging channel 13. A radial gap exists between the upper part of the outer upper module 8 and the upper part of the inner upper module 7. This radial gap forms part of the annular vertical merging channel, specifically becoming the lower section 12 of the annular vertical merging channel (equivalent to...). Figure 9 The KH section of the flow channel); an outer port module 90 is provided above the outer upper module 8, and an inner port module 9 is provided above the inner upper module 7. There is a radial gap between the outer port module 90 and the inner port module 9, which forms the upper section 17 of the annular vertical confluence flow channel (equivalent to the upper section 17 of the flow channel). Figure 9 The upper section 17 and the lower section 12 of the annular vertical confluence channel form the annular vertical confluence channel, and the upper end of the annular vertical confluence channel is connected to the annular extrusion port 15.

[0045] The annular inverted conical confluence channel 13 (equivalent to) Figure 9 The HE section flow channel is formed by the annular gap between the lower part of the inner upper module 7 and the upper end face of the second sleeve 2; the annular conical confluence flow channel 14 (equivalent to Figure 9The HD section flow channel is formed by the annular gap between the lower part of the outer upper module 8 and the upper end face of the third sleeve 3; the annular vertical confluence flow channel, the annular conical confluence flow channel 14, and the annular inverted conical confluence flow channel 13 form an inverted Y-shape in the radial section, as shown in the figure. Figure 8 , Figure 9 , Figure 10 As shown, specifically as follows Figure 9 The MH, HD, and HE channels in the middle form an inverted Y shape; Figure 7 , Figure 8 , Figure 9 , Figure 10 As shown, the outer edge of the innermost material leakage cavity 10 is directly connected to the lower end of the annular inverted cone confluence channel 13; the upper end of the annular gap between the inner lower module 5 and the first sleeve 1 is directly connected to the lower end of the annular inverted cone confluence channel 13; the upper end of the annular gap between the first sleeve 1 and the second sleeve 2 is directly connected to the lower end of the annular inverted cone confluence channel 13; the upper end of the annular gap between the second sleeve 2 and the third sleeve 3 is directly connected to the lower end of the annular vertical confluence channel (i.e., the lower end of the lower section 12 of the annular vertical confluence channel); the upper end of the annular gap between the third sleeve 3 and the fourth sleeve 4 is directly connected to the lower end of the annular positive cone confluence channel 14; the upper end of the annular gap between the fourth sleeve 4 and the outer lower module 6 is directly connected to the lower end of the annular positive cone confluence channel 14; and the inner edge of the outermost material leakage cavity 70 is directly connected to the lower end of the annular positive cone confluence channel 14.

[0046] In the above embodiments, the circumferential dimensions of the first packing piece 91 and the second packing piece 92 can be changed to 8 cm or 30 cm. Example 2

[0047] A seven-layer co-extrusion blown film production process, using the seven-layer co-extrusion blown film production equipment of Example 1 above, includes the following steps: (1) Each layer of molten plastic flows into a corresponding set of material spreading channels; The innermost molten plastic is made of PA material. The innermost molten plastic flows from the starting point of each externally rotating horizontal vortex channel 11 along the externally rotating horizontal vortex channel 11. During this process, the innermost molten plastic also leaks into the innermost material leakage cavity 10 next to the externally rotating horizontal vortex channel 11, causing the innermost molten plastic to be spread out into a ring. However, when the innermost molten plastic approaches the outer edge of the innermost material leakage cavity 10, the innermost molten plastic is missing in the corresponding position due to the occupation of the second filling piece 92. The second layer of molten plastic uses PE (polyethylene) + TIE (adhesive resin). The second layer of molten plastic flows upward along the spiral groove channel 21 between the inner lower module 5 and the first sleeve 1, and also continuously leaks upward from the annular gap 20 between the inner lower module 5 and the first sleeve 1, so that the second layer of molten plastic is unfolded into a ring. The third layer of molten plastic is made of PE (polyethylene). The third layer of molten plastic flows upward along the spiral groove channel 31 between the first sleeve 1 and the second sleeve 2, and also continuously leaks upward from the annular gap 30 between the first sleeve 1 and the second sleeve 2, so that the third layer of molten plastic is unfolded into a ring. The fourth layer of molten plastic is made of PE (polyethylene). The fourth layer of molten plastic flows upward along the spiral groove channel 41 between the second sleeve 2 and the third sleeve 3, and also continuously leaks upward from the annular gap 40 between the second sleeve 2 and the third sleeve 3, so that the fourth layer of molten plastic is unfolded into a ring. The fifth layer of molten plastic is made of PE (polyethylene). The fifth layer of molten plastic flows upward along the spiral groove channel 51 between the third sleeve 3 and the fourth sleeve 4, and also continuously leaks upward from the annular gap 50 between the third sleeve 3 and the fourth sleeve 4, so that the fifth layer of molten plastic is unfolded into a ring. The sixth layer of molten plastic is made of PE (polyethylene) + TIE (adhesive resin). The sixth layer of molten plastic flows upward along the spiral groove channel 61 between the fourth sleeve 4 and the outer lower module 6, and also continuously leaks upward from the annular gap 60 between the fourth sleeve 4 and the outer lower module 6, so that the sixth layer of molten plastic is unfolded into a ring. The outermost molten plastic is made of PA material. The outermost molten plastic flows from the starting point 710 of each inner swirling horizontal vortex channel 71 along the inner swirling horizontal vortex channel 71. During this process, the outermost molten plastic also leaks into the outermost material leakage cavity 70 next to the inner swirling horizontal vortex channel 71, causing the outermost molten plastic to be spread out (unfolded) into a ring. However, when the outermost molten plastic approaches the inner edge of the outermost material leakage cavity 70, the outermost molten plastic is missing in the corresponding position due to the occupation of the first filling piece 91. (2) The innermost layer of molten plastic, the second layer of molten plastic, and the third layer of molten plastic converge at the lower end of the annular inverted cone confluence channel 13, and then flow upward along the annular inverted cone confluence channel 13 to form the first confluence flow; the outermost layer of molten plastic, the sixth layer of molten plastic, and the fifth layer of molten plastic converge at the lower end of the annular positive cone confluence channel 14, and then flow upward along the annular positive cone confluence channel 14 to form the second confluence flow; the first confluence flow, the fourth layer of molten plastic, and the second confluence flow further converge at the lower end of the lower section 12 of the annular vertical confluence channel, so that the seven layers of molten plastic converge and flow into the lower section of the annular confluence channel. 12. Then, it flows upward from the upper section 17 of the annular vertical converging channel, and finally is extruded together from the annular extrusion port 15 to form a membrane bubble. The obtained membrane bubble has a seven-layer plastic composite structure, which is arranged from the inside out as the innermost plastic layer, the second plastic layer, the third plastic layer, the fourth plastic layer, the fifth plastic layer, the sixth plastic layer, and the outermost plastic layer. The innermost plastic layer and the outermost plastic layer are made of PA material. The outermost plastic layer is missing in the position corresponding to the first filler piece 91, and the innermost plastic layer is missing in the position corresponding to the second filler piece 92. The missing parts of the outermost plastic layer and the missing parts of the innermost plastic layer are in the same position (i.e., overlapping). (3) The obtained cylindrical film bubble is cut longitudinally, and the cutting line is located in the middle of the missing parts of the innermost plastic layer and the outermost plastic layer, so that the cylindrical film bubble becomes a sheet plastic film; the sheet plastic film is cut transversely to become multiple plastic films; the edges of different plastic films are overlapped and welded together. In each pair of plastic films welded together, the welding part of the first plastic film is located at the missing part of the innermost plastic layer (i.e., the missing part of PA material), and the welding part of the second plastic film is located at the missing part of the outermost plastic layer (i.e., the missing part of PA material). That is to say, the surface layer actually welded is the second layer of the first plastic film and the sixth layer of the second plastic film. Therefore, welding is easy and it is convenient to weld (overlap) transversely to form a wide greenhouse film, which is suitable for promotion and use. The welding point of the first plastic film can be the right edge of the plastic film, and the welding point of the second plastic film can be the left edge of the plastic film; or the welding point of the first plastic film can be the left edge of the plastic film, and the welding point of the second plastic film can be the right edge of the plastic film.

Claims

1. A multi-layer co-extrusion blown film production equipment for co-extruding multiple layers of molten material to form a plastic film bubble with a multi-layer composite structure, including a blown film head, the blown film head is provided with an annular extrusion port, an annular converging channel and several sets of material spreading channels, each set of material spreading channels guides the flow of one layer of molten material and spreads the molten material into an annular shape, the downstream end of each set of material spreading channels is connected to the annular converging channel, and the annular converging channel is connected to the annular extrusion port; The material spreading channel corresponding to the outermost layer of molten material includes an annular outermost material leakage cavity. This outermost material leakage cavity is formed by an annular upper module and an annular lower module sandwiched together. The upper module is located above the lower module, and there is a vertical gap between the inner parts of the upper module and the inner parts of the lower module. This vertical gap forms the outermost material leakage cavity. The outer edge of the outermost material leakage cavity is closed, and the inner edge of the outermost material leakage cavity is connected to the annular converging channel. Several inward-swirling horizontal vortex channels are also formed on the surface of the outermost material leakage cavity. Its features are: The proximal section of the outermost material leakage cavity has a tapered shape, smaller at the top and larger at the bottom. The part of the outermost material leakage cavity other than the proximal section is called the main body section of the outermost material leakage cavity. The outermost material leakage cavity is provided with a first plug, which includes an inclined section and a horizontal section of the first plug that are connected as one piece. The inclined section of the first plug is located inside the proximal section of the outermost material leakage cavity, and the horizontal section of the first plug is located inside the main body section of the outermost material leakage cavity. The material spreading channel corresponding to the innermost molten material includes an annular innermost material leakage cavity, which is formed by an annular upper inner module and an annular lower inner module sandwiched together. The upper inner module is located above the lower inner module, and the lower outer module is located around the lower inner module. The upper outer module is located around the upper inner module. There is a vertical gap between the outer parts of the upper inner module and the outer parts of the lower inner module, which forms the innermost material leakage cavity. The outer edge of the innermost material leakage cavity is connected to the annular converging channel, and the inner edge of the innermost material leakage cavity is closed. Several outward-swirling horizontal vortex channels are also formed on the surface of the innermost material leakage cavity. The distal section of the innermost material leakage cavity has a tapered shape, wider at the top and narrower at the bottom. The portion of the innermost material leakage cavity excluding the distal section is called the main body section of the innermost material leakage cavity. The innermost material leakage cavity is equipped with a second packing plate, which includes an integrally connected inclined section and a horizontal section. The inclined section is located inside the distal section of the innermost material leakage cavity, and the horizontal section is located inside the main body section of the innermost material leakage cavity. The second packing plate and the first packing plate are in the same orientation relative to the central axis of the blown film head. The distal section refers to the section far from the central axis of the blown film head, and the proximal section refers to the section close to the central axis of the blown film head.

2. The multi-layer co-extrusion blown film production equipment according to claim 1, characterized in that: The multi-layer co-extrusion blown film production equipment is a seven-layer co-extrusion blown film production equipment; between the annular inner lower module and the annular outer lower module, a first sleeve, a second sleeve, a third sleeve, and a fourth sleeve are sequentially installed from the inside to the outside. The inner lower module, the first sleeve, the second sleeve, the third sleeve, the fourth sleeve, and the outer lower module are collectively referred to as sleeves. The vertical central axis of each sleeve is in the same position. The upper end face of the first sleeve and the second sleeve has an inverted taper that is larger at the top and smaller at the bottom, while the upper end face of the third sleeve and the fourth sleeve has a positive taper that is smaller at the top and larger at the bottom. An annular gap is formed between each pair of adjacent inner and outer sleeves. Several spiral groove flow channels are also formed on the surface of the annular gap between each pair of adjacent inner and outer sleeves. The annular gap and the spiral groove flow channels between each pair of adjacent sleeves form a material spreading channel for a layer of molten material. The annular merging channel includes an annular vertical merging channel, an annular conical merging channel, and an annular inverted conical merging channel. These three channels form an inverted Y-shape in the radial cross-section. The annular inverted conical merging channel is formed by the annular gap between the lower part of the inner upper module and the upper end face of the second sleeve. The annular conical merging channel is formed by the annular gap between the lower part of the outer upper module and the upper end face of the third sleeve. There is a radial gap between the upper part of the outer upper module and the upper part of the inner upper module, which forms part of the annular vertical merging channel. The outer edge of the innermost material leakage cavity is directly connected to the lower end of the annular inverted cone confluence channel. The upper end of the annular gap between the inner lower module and the first sleeve is directly connected to the lower end of the annular inverted cone confluence channel. The upper end of the annular gap between the first sleeve and the second sleeve is directly connected to the lower end of the annular inverted cone confluence channel. The upper end of the annular gap between the second sleeve and the third sleeve is connected to the lower end of the annular vertical confluence channel. The upper end of the annular gap between the third sleeve and the fourth sleeve is directly connected to the lower end of the annular positive cone confluence channel. The upper end of the annular gap between the fourth sleeve and the outer lower module is directly connected to the lower end of the annular positive cone confluence channel. The inner edge of the outermost material leakage cavity is directly connected to the lower end of the annular positive cone confluence channel.

3. The multi-layer co-extrusion blown film production equipment according to claim 2, characterized in that: An outer port module is provided above the outer upper module, and an inner port module is provided above the inner upper module. There is a radial gap between the outer port module and the inner port module, which forms the upper section of the annular vertical confluence channel. The radial gap between the upper part of the outer upper module and the upper part of the inner upper module forms the lower section of the annular vertical confluence channel.

4. The multilayer co-extrusion blown film production equipment according to claim 1, 2 or 3, characterized in that: The circumferential dimension of the first packing piece is 8–30 cm, and the circumferential dimension of the second packing piece is 8–30 cm.

5. A multi-layer co-extrusion blown film production process, characterized in that... The production equipment for multilayer co-extrusion blown film as described in any one of claims 1 to 4 includes the following steps: (1) Each layer of molten plastic flows into a corresponding set of material spreading channels and spreads out into a ring; among them, the outermost layer of molten plastic flows from the starting point of each inner swirling horizontal vortex channel along the inner swirling horizontal vortex channel. During this process, the outermost layer of molten plastic also leaks into the outermost material leakage cavity next to the inner swirling horizontal vortex channel, so that the outermost layer of molten plastic is spread out into a ring. However, when the outermost layer of molten plastic approaches the inner edge of the outermost material leakage cavity, the outermost layer of molten plastic is missing in the corresponding position due to the occupation of the first filling piece. The innermost layer of molten plastic flows from the starting point of each outer-swirl horizontal vortex channel along the outer-swirl horizontal vortex channel. During this process, the innermost layer of molten plastic also leaks into the innermost material leakage cavity next to the outer-swirl horizontal vortex channel, causing the innermost layer of molten plastic to spread out into a ring. However, when the innermost layer of molten plastic approaches the outer edge of the innermost material leakage cavity, the innermost layer of molten plastic is missing in the corresponding position due to the occupation of the second packing piece. (2) The molten plastic layers of each layer flow into the annular confluence channel and are finally extruded from the annular extrusion port to form a membrane bubble. The resulting membrane bubble has a multi-layer plastic composite structure. The outermost plastic layer is missing in the position corresponding to the first filler piece, and the innermost plastic layer is missing in the position corresponding to the second filler piece. The missing parts of the outermost plastic layer and the missing parts of the innermost plastic layer are in the same position.

6. The multilayer co-extrusion blown film production process according to claim 5, characterized in that: The outermost molten plastic is polyamide, and the innermost molten plastic is polyamide. The resulting cylindrical film bubble is longitudinally cut open, with the cutting line located in the middle of the missing parts of the innermost and outermost plastic layers, transforming the cylindrical film bubble into a sheet-like plastic film. The sheet-like plastic film is transversely cut into multiple plastic films, and the edges of the different plastic films are overlapped and welded together. In every two welded plastic films, the welded part of the first plastic film is located at the missing part of the innermost plastic layer, and the welded part of the second plastic film is located at the missing part of the outermost plastic layer.

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