A machine die for extruding a three-layer structure plastic pipe with an oxygen barrier layer

Abstract

The present application relates to the field of plastic pipe extrusion, and particularly relates to a die for extruding a three-layer structure plastic pipe with an oxygen barrier layer, comprising an inner layer machine body, a middle layer machine body, an outer layer machine body, a machine body front end cover, a discharging machine body and a discharging part, the inner layer machine body comprises an inner layer feeding port, an inner layer spiral mandrel and an inner layer cavity in sequence, the inner layer feeding port is arranged at the rear end of the inner layer spiral mandrel, the inner layer spiral mandrel is arranged inside the cavity of the inner layer cavity, the front end of the inner layer cavity is sequentially provided with the middle layer machine body, the outer layer machine body and the machine body front end cover, the rear end of the discharging machine body is connected with the machine body front end cover, and the front end of the discharging machine body is further provided with the discharging part; the flow channel structure design of the present application can prevent the oxygen barrier layer material from being easily pyrolyzed and deteriorated, the oxygen barrier effect of the produced pipe is better, and the overall design of the die and the design of the discharging part can greatly improve the production and manufacturing efficiency of the pipe.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of plastic pipe extrusion, in particular to a die for extruding a three-layer structure plastic pipe with an oxygen barrier layer. BACKGROUND

[0002] With the continuous development of pipeline technology, the single single-layer structure plastic pipeline has single function, and it is difficult to meet the use demand. Through the compounding of multi-layer structure and multi-layer material, the plastic pipeline can be given more functions. In order to protect the components in the pipeline system from being eroded by the outside world, a plastic pipeline with an oxygen barrier layer emerges as the times require. The pipeline with this structure needs a three-layer extruder to extrude different raw materials into a three-layer structure die, and finally three different materials are extruded into a three-layer structure plastic pipeline through the die. The outer layer is an oxygen barrier layer, the middle layer is a hot melt adhesive layer, and the inner layer is a polyolefin material layer.

[0003] The best material for oxygen barrier is ethylene vinyl alcohol (EVOH) material which is prone to thermal cracking. The die structure of the double-layer co-extrusion pipe die head disclosed in the publication No. CN205238507U adopts a spiral structure, which results in a too large volume of the die flow channel. A large amount of EVOH raw material is stored in the die flow channel, and the EVOH raw material stays in the die for a long time, which causes the raw material to deteriorate due to thermal cracking. The appearance of the finished pipe is not good, the EVOH layer material deteriorates, and the oxygen barrier function decreases. In addition, the overall outer diameter of the die is large, and the heating time of the die is long, which results in a slow temperature rising time when starting, low production starting efficiency, and dead angles in the die flow channel, which causes the raw material to stay in the dead angles for a long time, decompose and carbonize, and finally bring out black carbonized impurity points. SUMMARY

[0004] The purpose of the present application is to solve the problems in the background art, and to provide a die for extruding a three-layer structure plastic pipe with an oxygen barrier layer. The die shortens the flow channel length and has a smaller total flow channel volume, thereby reducing the time of the material staying in the die, ensuring the quality of the material in the flow channel, and making the die heating time faster, thereby improving the starting efficiency.

[0005] The above technical purpose of the present application is achieved by the following technical scheme:

[0006] A machine die for extruding a three-layer structure plastic pipe with an oxygen barrier layer, comprising an inner layer machine body, a middle layer machine body, an outer layer machine body, a machine body front end cover, a discharge machine body and a discharge part; the inner layer machine body comprises an inner layer feed inlet, an inner layer spiral mandrel and an inner layer cavity in sequence, the inner layer feed inlet is arranged at the rear end of the inner layer spiral mandrel, and the inner layer spiral mandrel is arranged inside the cavity of the inner layer cavity; the front end of the inner layer cavity is sequentially provided with the middle layer machine body, the outer layer machine body and the machine body front end cover, the rear end of the discharge machine body is connected with the machine body front end cover, and the front end of the discharge machine body is further provided with the discharge part.

[0007] Preferably, the tail of the inner layer spiral mandrel is provided with a plurality of spiral mandrel feed inlets and is in communication with the inner layer feed inlet, and a plurality of spiral inner layer flow channels are further arranged on the inner layer spiral mandrel and are in communication with the spiral mandrel feed inlets; the front part of the inner layer spiral mandrel is a main flow channel mandrel, and a die threaded connection part is further arranged at the front end of the main flow channel mandrel.

[0008] The spiral mandrel feed inlet is in communication with the inner layer feed inlet, and the raw material of the inner layer extruder can directly enter the spiral flow channel through the inner layer feed inlet; the depth of the spiral inner layer flow channel gradually decreases as it approaches the outflow section, and at the same time, the gap between the mandrel and the inner layer cavity gradually increases, and in this interval, the overlap of the axial and radial movement of the fluid raw material inside appears, the proportion of radial movement along the outflow direction decreases and the proportion of axial movement increases, and finally all the fluid will move axially; by adopting this structure, the fluid raw material moves uniformly around the flow channel, so that the extruded pipe does not have local strength loss, and the quality and service life of the pipe are greatly improved.

[0009] Preferably, the outer layer machine body is provided with a middle layer connector and a middle layer feed inlet, the machine body front end cover is provided with an outer layer connector and an outer layer feed inlet, and the middle layer connector and the outer layer connector are both provided with external threads at both ends.

[0010] Preferably, the inner layer extruder is connected with the inner layer extruder through the inner layer extruder clamp on the inner layer feed inlet, the outer layer machine body is connected with the middle layer extruder through the middle layer extruder connector, and the machine body front end cover is connected with the outer layer extruder through the outer layer extruder connector.

[0011] The three-layer co-extrusion machine die can simultaneously connect three extruders, which respectively provide the molten raw materials of the inner layer, the middle layer and the outer layer and inject them into the three-layer co-extrusion machine die, making pipe production more convenient, and the three-layer pipe can be completed by one-time co-extrusion, greatly improving the pipe production efficiency.

[0012] As preferred, the middle layer machine body is provided with a buffer type middle layer flow channel, which is a structure of multiple buffer grooves, and a plurality of middle layer flow channel notches are further opened on the groove body.

[0013] As preferred, the buffer type outer layer flow channel is a structure of multiple buffer grooves, and a plurality of outer layer flow channel notches are further opened on the groove body, and the length of the buffer type outer layer flow channel is less than the depth of the rear end groove of the machine body front end cover.

[0014] The middle layer and outer layer flow channels abandon the traditional spiral flow channel structure and adopt a three-buffer-groove structure. Compared with the spiral flow channel structure, the length and depth of the flow channel are reduced, so that the outer diameter size of the co-extrusion mold can be made smaller, the overall volume of the mold is reduced, the mold heating time is faster after the extruder is started, the production starting efficiency is improved, and the residence time of the hot melt adhesive and EVOH raw materials in the flow channel is also shortened. The EVOH raw material will not be pyrolyzed and deteriorated, and the oxygen barrier function of the co-extruded pipe material is greatly improved. In addition, the three-buffer-groove structure design makes the pressure of the molten raw material uniform in the circumferential direction, and a plurality of appropriate notches are opened on the buffer groove to make it flow in the circumferential direction. The extruded pipe material has uniform strength and is not easy to bend and break, and the oxygen barrier effect is better, so that the pipe material quality is greatly improved.

[0015] As preferred, the middle layer machine body and the outer layer machine body are a nested doll structure, and the front end of the outer layer machine body can be nested with multiple outer layer machine bodies to realize a multi-layer co-extrusion structure.

[0016] The nested doll structure can nest one or more layers of co-extrusion structure, and can realize the completion of multi-layer co-extruded pipe material at the same machine mold at one time, avoiding multiple processes of multi-layer co-extruded pipe material, greatly improving the production efficiency of multi-layer pipe material. The multi-layer pipe material made by using the nested co-extrusion structure has clear layers and uniform thickness, and the quality of the multi-layer pipe material is improved. In addition, the nested doll structure design is relatively simple and has a small volume, which facilitates the installation and disassembly work in the use process, effectively improves the production efficiency of the multi-layer pipe material, and at the same time integrates multiple processes into one process, reduces the production cost, and improves the market competitiveness.

[0017] As preferred, the gap between the spiral type inner layer flow channel and the inner layer cavity is a spiral flow channel, the gap between the main flow channel mandrel and the machine body front end is a main flow channel, the gap between the buffer type middle layer flow channel and the outer layer machine body groove is a middle layer merging flow channel, the gap between the buffer type outer layer flow channel and the machine body front end cover groove is an outer layer merging flow channel, and the connection between the spiral flow channel and the main flow channel is a buffer flow channel.

[0018] The polyolefin material extruded by the inner layer extruder enters the spiral mandrel feed port and reaches the spiral flow channel after passing through the inner layer feed port, and reaches the main flow channel after passing through the buffer flow channel under the extrusion of the inner layer extruder; the hot melt adhesive extruded by the middle layer extruder enters the buffer type middle layer flow channel after passing through the middle layer extruder connecting body, and enters the main flow channel after passing through the middle layer merging flow channel under the extrusion of the middle layer extruder; the raw materials of the inner layer, the middle layer and the outer layer are co-extruded in the main flow channel and finally reach the die part and are extruded into a pipe with a corresponding size according to the size of the die and the core die.

[0019] Preferably, the discharging machine body is sequentially provided with a wall thickness adjusting connecting body, a die connecting body and a pressure plate.

[0020] Preferably, the discharging part comprises a die and a core die, the rear end of the die and the core die are provided with external threads, the die is threadedly connected with the die connecting body, and the core die is threadedly connected with the core die threadedly connected part.

[0021] The die and the core die are connected with the die by threadedly connecting the external threads at the rear end, and the cooperation gap between the die and the core die determines the size of the inner and outer diameters of the extruded pipe, and the die and the core die can be adjusted or replaced according to actual needs during production; since the die and the core die are both provided with threads, the frequency of adjusting the concentricity of the die and the core die is saved during die replacement, time cost is greatly saved, and the production efficiency of the co-extruded pipe is improved.

[0022] In summary, the beneficial effects of the present application are:

[0023] 1. The die for extruding a three-layer structure plastic pipe with an oxygen barrier layer has a smaller outer diameter size than a traditional die, a smaller overall volume, faster heating time of the die, and improved production start-up efficiency.

[0024] 2. The middle layer and the outer layer flow channel of the die abandon the traditional spiral flow channel structure and adopt a three-buffer-groove structure, so that the length and depth of the flow channel are reduced, the residence time of EVOH raw materials and the like in the flow channel is less, and the raw materials are less likely to crack and deteriorate, the oxygen barrier effect of the co-extruded pipe is better, the strength is uniform, the pipe is less likely to bend and break, and the quality is greatly improved.

[0025] 3. The machine mold for extruding a three-layer structure plastic pipe with an oxygen barrier layer, the doll structure machine body can be nested with one or more layers of co-extrusion structure, which can realize the completion of the multi-layer co-extrusion pipe in one time on the same machine mold, avoids the production of multiple process combination, greatly improves the production efficiency, at the same time, the doll structure design is simple and convenient to disassemble, integrates multiple processes into one, reduces the production cost and improves the market competitiveness;

[0026] 4. The machine mold for extruding a three-layer structure plastic pipe with an oxygen barrier layer, the die head and the core mold of the discharging part are connected by threads, when the die head and the core mold size are replaced, the step of adjusting the concentricity of the die head and the core mold is omitted, which greatly saves the time cost and improves the production efficiency of the co-extrusion pipe. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is the overall structure schematic diagram of the present application;

[0028] Figure 2 is the core rod structure schematic diagram of the present application;

[0029] Figure 3 is the middle layer machine body sectional view schematic diagram of the present application;

[0030] Figure 4 is the overall structure schematic diagram of the middle layer machine body of the present application;

[0031] Figure 5 is the outer layer machine body structure schematic diagram of the present application;

[0032] Figure 6 is the machine body front end cover structure schematic diagram of the present application;

[0033] Figure 7 is the discharging part structure schematic diagram of the present application;

[0034] Figure 8 is the flow channel structure schematic diagram of the present application;

[0035] Figure 9 is the machine body doll structure schematic diagram of the present application.

[0036] Marked in the figure: 1-inner layer machine body, 11-inner layer feeding port, 12-inner layer spiral mandrel, 121-spiral mandrel feeding port, 122-spiral inner layer runner, 123-main runner mandrel, 124-core mold threaded connection part, 13-inner layer cavity, 14-inner layer extruder clamp, 2-middle layer machine body, 21-buffered middle layer runner, 22-middle layer runner notch, 3-outer layer machine body, 31-middle layer extruder connecting body, 32-middle layer feeding port, 33-buffered outer layer runner, 34-outer layer runner notch, 4-machine body front end cover, 41-outer layer extruder connecting body, 42-outer layer feeding port, 5-discharge machine body, 51-wall thickness adjusting connecting body, 52-die connecting body, 53-pressing disc, 6-discharge part, 61-die, 62-core mold, 7-spiral runner, 8-main runner, 81-middle layer converging runner, 82-outer layer converging runner, 9-buffered runner. DETAILED DESCRIPTION

[0037] The following specific examples are merely explanatory of the present application, and are not intended to limit the present application. Those skilled in the art can make modifications to the present examples without creative contribution after reading the present specification, and the present application is protected by the patent law as long as it is within the scope of the claims.

[0038] The present application will be described in detail below with examples in combination with the accompanying drawings. Example 1

[0039] According to Figures 1-8 As shown in the figure, a machine mold for extruding a three-layer structure plastic pipe with an oxygen barrier layer includes an inner layer machine body 1, a middle layer machine body 2, an outer layer machine body 3, a machine body front end cover 4, a discharge machine body 5, and a discharge part 6; the inner layer machine body 1 includes an inner layer feeding port 11, an inner layer spiral mandrel 12, and an inner layer cavity 13 in sequence, the inner layer feeding port 11 is arranged at the rear end of the inner layer spiral mandrel 12, and the inner layer spiral mandrel is arranged inside the cavity of the inner layer cavity 13; the front end of the inner layer cavity 13 is sequentially provided with the middle layer machine body 2, the outer layer machine body 3, and the machine body front end cover 4, the rear end of the discharge machine body 5 is connected with the machine body front end cover 4, and the front end of the discharge machine body 5 is further provided with the discharge part 6;

[0040] According to Figure 2As shown, the tail of the inner layer spiral mandrel 12 is provided with a plurality of spiral mandrel feed ports 121 and is in communication with the inner layer feed port 11, and the inner layer spiral mandrel is further provided with a plurality of spiral inner layer flow channels 122 in communication with the spiral mandrel feed ports 121, and the front part of the inner layer spiral mandrel is a main flow channel mandrel 123, and the front end of the main flow channel mandrel 123 is further provided with a core mold threaded connection part 124; the inner layer material of the three-layer pipe with an oxygen barrier layer is polyolefin, the spiral mandrel feed port is in communication with the inner layer feed port, and the polyolefin directly enters the spiral flow channel through the inner layer feed port after passing through the inner layer extruder; the depth of the spiral inner layer flow channel 122 gradually decreases as it approaches the outflow section, and at the same time, the gap between the inner layer spiral mandrel 12 and the inner layer cavity 13 gradually increases, and the polyolefin raw material inside this interval appears axial and radial movement overlap, the proportion of radial movement decreases and the proportion of axial movement increases along the outflow direction, and finally all move axially; this structure makes the polyolefin move uniformly around the flow channel, so that the extruded pipe does not have local strength loss, and the quality and service life of the co-extruded pipe are greatly improved;

[0041] According to Figure 1 、 4 , as shown in figure 6, the outer layer body 3 is provided with a middle layer connecting body 31 and a middle layer feed port 32, and the front end cover 4 of the body is provided with an outer layer connecting body 41 and an outer layer feed port 42, and the middle layer connecting body 31 and the outer layer connecting body 41 are provided with external threads at both ends; the inner layer body 1 is connected with the inner layer extruder through the inner layer extruder clamp 14 on the inner layer feed port 11, the outer layer body 3 is connected with the middle layer extruder through the middle layer extruder connecting body 31, and the front end cover 4 of the body is connected with the outer layer extruder through the outer layer extruder connecting body 41; the three-layer co-extrusion machine die can simultaneously connect three extruders to work, the inner layer feed port 11 connects the polyolefin inner layer extruder, the middle layer extruder connecting body 31 connects the hot melt adhesive middle layer extruder, and the outer layer extruder connecting body 41 connects the EVOH outer layer extruder; three extruders inject different raw materials into the co-extrusion machine die, and three-layer pipe can be completed by co-extrusion in turn, which makes pipe production more convenient and greatly improves the pipe production efficiency;

[0042] According to Figures 3-5As shown, the middle layer machine body 2 is provided with a buffer type middle layer flow channel 21, the buffer type middle layer flow channel 21 is a structure of multiple buffer grooves, a plurality of middle layer flow channel notches 22 are opened on the groove body of the buffer groove, and the length of the buffer type middle layer flow channel 21 is less than the depth of the rear end groove of the outer layer machine body 3; the outer layer machine body 3 is also provided with a buffer type outer layer flow channel 33, the buffer type outer layer flow channel 33 is a structure of multiple buffer grooves, a plurality of outer layer flow channel notches 34 are also opened on the groove body of the buffer groove, and the length of the buffer type outer layer flow channel 33 is less than the depth of the rear end groove of the machine front end cover 4; the middle layer and outer layer flow channels abandon the structure of the traditional spiral flow channel, adopt the structure of three buffer grooves, the traditional spiral flow channel has a large volume, the EVOH raw material stays in the flow channel for a long time and is prone to thermal cracking and deterioration, resulting in poor appearance of the pipe and reduced oxygen barrier function; compared with the spiral flow channel structure, the length and depth of the buffer groove flow channel are reduced, so that the outer diameter size of the co-extrusion die can be made smaller, the overall volume of the die is reduced, the die heating time is faster after the extruder is started, the production start-up efficiency is improved, the residence time of the EVOH raw material in the flow channel is also shortened, and the oxygen barrier ability of the co-extrusion pipe is also improved; and the three-buffer-groove structure design makes the pressure of the molten raw material uniform in the circumferential direction, a plurality of appropriate notches are opened on the buffer groove, so that the molten raw material can be divided in the circumferential direction, the extruded pipe has more uniform strength and is not easy to bend and break, and the pipe quality is greatly improved;

[0043] According to Figure 1 and Figure 7 As shown, the discharge body 5 is sequentially provided with a wall thickness adjusting connecting body 51, a die connecting body 52 and a pressure plate 53, the discharge part 6 includes a die 61 and a core die 62, the rear end of the die 61 and the core die 62 is provided with an external thread, the die 61 is threadedly connected with the die connecting body 52, and the core die 62 is threadedly connected with a core die threaded connecting part 124; the cooperation gap between the die 61 and the core die 62 determines the inner and outer diameters of the extruded pipe, and the die 61 and the core die 62 can be adjusted or replaced according to the time requirement in the production process, and since the die 61 and the core die 62 are provided with external threads, the frequency of adjusting the concentricity of the die 61 and the core die 62 is saved in the die replacement process, the time cost is greatly saved, and the production efficiency of the co-extrusion pipe is improved;

[0044] According to Figure 8As shown, the gap between the helical inner layer flow channel 122 and the inner layer cavity 13 is the helical flow channel 7, the gap between the main flow channel mandrel 123 and the front end of the body is the main flow channel 8, the gap between the buffer type middle layer flow channel 21 and the groove of the outer layer body 3 is the middle layer merging flow channel 81, the gap between the buffer type outer layer flow channel 33 and the groove of the front end cover 4 of the body is the outer layer merging flow channel 82, and the connection between the helical flow channel 7 and the main flow channel 8 is the buffer flow channel 9; the polyolefin raw material extruded by the inner layer extruder enters the helical mandrel feed port 121 after passing through the inner layer feed port 11 and reaches the helical flow channel 7, and then reaches the main flow channel 8 after passing through the buffer flow channel 9 under the extrusion of the inner layer extruder; the hot melt adhesive raw material extruded by the middle layer extruder enters the buffer type middle layer flow channel 21 after passing through the middle layer extruder connecting body 31, and then enters the main flow channel 8 after passing through the middle layer merging flow channel 81 under the extrusion of the middle layer extruder; the EVOH raw material extruded by the outer layer extruder enters the buffer type outer layer flow channel 33 after passing through the outer layer extruder connecting body 41, and then enters the main flow channel 8 after passing through the outer layer merging flow channel 82 under the extrusion of the outer layer extruder; the raw materials of the inner layer, the middle layer and the outer layer are co-extruded in the main flow channel 8 and then extruded forward to the discharge part 6, and finally a three-layer structure plastic pipe material with an oxygen barrier layer is extruded according to the size of the die and the core die. Example 2

[0045] According to Figure 9 As shown, different from the above-mentioned embodiment 1, a die for extruding a three-layer structure plastic pipe material with an oxygen barrier layer, the middle layer body 2 and the outer layer body 3 are in a nested doll structure, and the front end of the outer layer body 3 can further nest multiple outer layer bodies 3 to realize a multi-layer co-extrusion structure; the nested doll structure of the present application can realize a one-layer or multi-layer co-extrusion structure, and can realize the completion of a multi-layer co-extruded pipe material at one time in the same die, avoiding the need for multiple processes to complete the production of a multi-layer co-extruded pipe material, greatly improving the production efficiency of the multi-layer pipe material, and the multi-layer pipe material made by using the nested doll co-extrusion structure has clear layers and uniform thickness, and the quality of the multi-layer pipe material is greatly improved; and the nested doll structure design is relatively simple and has a small volume, facilitating the installation and disassembly work in the use process, effectively improving the use efficiency of the multi-layer pipe material co-extrusion die, and at the same time, the multiple processes are integrated into one process, reducing the production cost and improving the market competitiveness.

Claims

1. A die for extruding a three-layer structure plastic pipe with an oxygen barrier layer, characterized in that, The application relates to a multi-layered extruder, which comprises an inner-layer body (1), a middle-layer body (2), an outer-layer body (3), a body front end cover (4), a discharging body (5) and a discharging part (6); the inner-layer body (1) comprises an inner-layer feeding port (11), an inner-layer spiral mandrel (12) and an inner-layer cavity (13) in sequence, the inner-layer feeding port (11) is arranged at the rear end of the inner-layer spiral mandrel (12), and the inner-layer spiral mandrel (12) is arranged inside the cavity of the inner-layer cavity (13); the front end of the inner-layer cavity (13) is sequentially provided with the middle-layer body (2), the outer-layer body (3) and the body front end cover (4), the rear end of the discharging body (5) is connected with the body front end cover (4), and the front end of the discharging body (5) is further provided with the discharging part (6). A plurality of spiral mandrel feeding ports (121) are arranged at the tail of the inner-layer spiral mandrel (12) and are communicated with the inner-layer feeding port (11), a plurality of spiral inner-layer flow channels (122) are further arranged on the inner-layer spiral mandrel (12) and are communicated with the spiral mandrel feeding ports (121); the front part of the inner-layer spiral mandrel (12) is a main flow channel mandrel (123), and a core mold threaded connection part (124) is further arranged at the front end of the main flow channel mandrel (123). The outer-layer body (3) is provided with a middle-layer extruder connecting body (31) and a middle-layer feeding port (32), the body front end cover (4) is provided with an outer-layer extruder connecting body (41) and an outer-layer feeding port (42), the middle-layer extruder connecting body (31) and the outer-layer extruder connecting body (41) are provided with external threads at both ends. The outer-layer body (3) is further provided with a buffer type outer-layer flow channel (33), the buffer type outer-layer flow channel (33) is a structure of multiple buffer grooves, a plurality of outer-layer flow channel notches (34) are further formed on the groove bodies of the buffer grooves, and the length of the buffer type outer-layer flow channel (33) is less than the depth of the rear end groove of the body front end cover (4). The gap between the spiral inner-layer flow channel (122) and the inner-layer cavity (13) is a spiral flow channel (7), the gap between the main flow channel mandrel (123) and the front end of the body is a main flow channel (8), the middle-layer body (2) is provided with a buffer type middle-layer flow channel (21), the gap between the buffer type middle-layer flow channel (21) and the groove of the outer-layer body (3) is a middle-layer converging flow channel (81), the gap between the buffer type outer-layer flow channel (33) and the groove of the body front end cover (4) is an outer-layer converging flow channel (82), and the connection part of the spiral flow channel (7) and the main flow channel (8) is a buffer flow channel (9).

2. A die for extruding a three-layer structure plastic pipe with an oxygen barrier layer according to claim 1, characterized in that, The inner-layer body (1) is connected with an inner-layer extruder through an inner-layer extruder clamp (14) on the inner-layer feeding port (11), the outer-layer body (3) is connected with a middle-layer extruder through the middle-layer extruder connecting body (31), and the body front end cover (4) is connected with an outer-layer extruder through the outer-layer extruder connecting body (41).

3. A die for extruding a three-layer structure plastic pipe with an oxygen barrier layer according to claim 2, characterized in that, The buffer type middle layer flow channel (21) is a structure of multiple buffer grooves, and a plurality of middle layer flow channel notches (22) are further formed on the groove body of the buffer groove.

4. A die for extruding a three-layer structure plastic pipe with an oxygen barrier layer according to claim 3, characterized in that, The middle layer body (2) and the outer layer body (3) are a structure of nested dolls, the front end of the outer layer body (3) is nested with a plurality of the outer layer body (3), so that a multi-layer co-extrusion structure is realized.

5. A die for extruding a three-layer structure plastic pipe with an oxygen barrier layer according to claim 4, characterized in that, The discharge body (5) is sequentially provided with a wall thickness adjusting connecting body (51), a die connecting body (52) and a pressure plate (53).

6. A die for extruding a three-layer structure plastic pipe with an oxygen barrier layer according to claim 5, characterized in that, The discharge part (6) comprises a die (61) and a core die (62), the rear end of the die (61) and the core die (62) are provided with external threads; the die (61) is threadedly connected with the die connecting body (52), and the core die (62) is threadedly connected with the core die threaded connecting part (124).

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