Multi-layer composite pipe as well as preparation method and preparation device thereof

Abstract

The invention relates to the technical field of composite pipes, and discloses a multi-layer composite pipe and a preparation method and device thereof.The multi-layer composite pipe comprises an inner layer, a bonding layer, an outer layer and at least two marking layers, the bonding layer is located between the inner layer and the outer layer, and the marking layers are located on the peripheral side of the outer layer; the outer layer is made of HDPE (high-density polyethylene), pigment, UV (ultraviolet) stabilizer and calcium carbonate filler, durability and attractiveness of the pipe can be enhanced by the aid of the outer layer, and antibacterial, flame-retardant and other functions are added; the adhesive layer ensures firm combination of all the layers, the oxidation resistance of the adhesive is improved, the adhesive performance is prevented from being reduced due to oxidation, and layering is prevented; and the characteristic inner layer adjusts the proportion and increase and decrease of the characteristic material according to the condition of the conveying medium so as to meet the specific requirements of the industry.

Description

Technical Field

[0001] The present invention relates to the technical field of composite pipes, and particularly to a multi-layer composite pipe, a preparation method thereof, and a preparation device thereof. Background Art

[0002] In traditional application fields, such as industrial pipelines, building drainage systems, and the medical industry, ordinary single-layer or simple-structured pipes often fail to meet complex application requirements. For example, in an industrial environment, pipes need to have properties such as corrosion resistance and high temperature resistance; in the building field, in addition to basic physical properties, factors such as flame retardancy, aesthetics, and ease of installation also need to be considered; while in medical applications, hygiene standards require pipes to have special functions such as antibacterial properties. However, traditional pipes made of a single material usually cannot meet these diverse requirements simultaneously.

[0003] To solve these problems, it is necessary to use multiple layers of pipes working together to meet the requirements. The production of multi-layer pipes usually requires extrusion molding by means of multi-layer co-extrusion, so that the pipes can form a multi-layer composite structure. Nowadays, co-extrusion heads are of different types according to different numbers of layers. When it needs to be replaced, the original head needs to be disassembled and then the corresponding head needs to be installed. Such a replacement process is rather cumbersome. Moreover, the internal structure of today's multi-layer heads is relatively complex, thus increasing the purchase cost of the heads. Summary of the Invention

[0004] To solve the above problems existing in the prior art, the present invention provides a multi-layer composite pipe, a preparation method thereof, and a preparation device thereof, which have the advantages of multi-layer pipes meeting different use environments and a modular head for pipe extrusion that is convenient to replace.

[0005] To achieve the above object, the present invention provides the following technical solutions: It includes an inner layer, a bonding layer, an outer layer, and a marking layer. The bonding layer is located between the inner layer and the outer layer, and the marking layer is located on the outer peripheral side of the outer layer. There are at least two marking layers, and they are evenly distributed circumferentially on the outer layer.

[0006] Preferably, the raw materials of the outer layer are HDPE, pigments, UV stabilizers, and calcium carbonate fillers. The materials of the bonding layer include epoxy resin, calcium carbonate, and antioxidants. The materials of the inner layer are HDPE, nitrile rubber, and modified ester plasticizers; Among them, the thickness of the inner layer is 0.15 - 0.2 mm, the thickness of the bonding layer is 0.04 - 0.1 mm, and the thickness of the outer layer is 0.16 - 2.2 mm.

[0007] A preparation method of a multi-layer composite pipe includes the following steps: S1: Select the corresponding amounts of raw materials required for the inner layer, the bonding layer, and the outer layer respectively, and perform preliminary drying; S2: Put the prepared raw materials into the corresponding mixer, that is, mix and dry the raw materials for the inner layer and the outer layer respectively. Raise the mixing and drying temperature to 120°C, and then cool it to 40 - 50°C. S3: After mixing and stirring, the raw materials of the inner layer are transported to the inner layer extruder through a conveyor, the raw materials of the bonding layer are directly transported to the adhesive extruder through a conveyor, and the raw materials of the outer layer are transported to the outer layer extruder through a conveyor. Control the extrusion temperature of the outer layer at 180 - 200°C, the extrusion temperature of the inner layer at 190 - 210°C, and the extrusion temperature of the bonding layer at 200 - 220°C. S3: The extruded raw materials are input into the die head of the multi-layer extruder in layers, and then the blank of the multi-layer pipe can be extruded. While the blank is being extruded, the marking layer is adhered to the blank through the marking strip extruder. S4: The extruded blank first enters the shaping and cooling equipment for preliminary shaping. The cooling temperature of the shaping and cooling equipment is 25 - 40°C, and then it enters the cooling equipment, and the cooling temperature is 15 - 20°C. S5: The pipe after shaping is input into the traction power equipment. Its traction rate corresponds to the extrusion rate, and the traction ratio is greater than 1, that is, the ratio of the traction rate to the extrusion rate is 1.1 - 1.5. S6: The formed pipe products are cut according to the required length, and then collected together for storage.

[0008] A die head device for a method of preparing a multi-layer composite pipe, comprising an extrusion die head and a mandrel, and the extrusion die head is sleeved on the mandrel. The extrusion die head includes a main die head and several detachable sub-die heads, and the main die head is installed on the extruder. The mandrel includes a main mandrel tube and several sub-mandrel tubes. The main mandrel tube is installed on the extruder through mounting bolts, and the sub-mandrel tubes are installed on the main mandrel tube.

[0009] Preferably, the sub-die head includes a first sub-die head and a second sub-die head. The first sub-die head is movably connected to the main die head, the second sub-die head is installed on the first sub-die head, and both the first sub-die head and the second sub-die head are hollow and sleeved on the mandrel.

[0010] Preferably, a first extrusion cavity and a first forming groove are formed in the first sub-die head in an annular shape, and the first forming groove communicates with its hollow part. A second extrusion cavity and a second forming groove are formed in the second sub-die head, and the second forming groove communicates with its hollow part.

[0011] Preferably, the radius length of the end of the first forming groove away from the first extrusion cavity is less than the radius length of the end of the second forming groove away from the second extrusion cavity. The thicknesses of the first extrusion cavity and the second extrusion cavity are both greater than those of the first forming groove and the second forming groove, and both the first extrusion cavity and the second extrusion cavity are inclined.

[0012] Preferably, a first mounting opening is provided on one end face of the first sub-head, and a first connecting block is fixed on the other end face. The first connecting block is mounted on the main head, and a first external interface is further provided on the outer peripheral side of the first sub-head. The first external interface communicates with the first extrusion cavity; A second mounting opening is provided on one end face of the second sub-head, and a second connecting block is fixed on the other end face. The second connecting block is mounted in the first mounting opening, and a second external interface is further provided on the outer peripheral side of the second sub-head. The second external interface communicates with the second extrusion cavity.

[0013] Preferably, a main connecting groove is provided at the center of the main core pipe, and the mounting bolt is also rotatably provided at the center of the main core pipe. One side of the mounting bolt is located in the main connecting groove; A connecting convex block is fixed on one end face of the sub-core pipe and is detachably mounted in the main connecting groove through the connecting convex block. A connecting groove is provided on the other end face, and the part of the main core pipe close to the sub-core pipe has the same radius as the sub-core pipe.

[0014] Preferably, a blank inlet is provided at the middle of the main head. A forming cavity is formed between the blank inlet and the main core pipe for extruding the blank. A main mounting opening is provided on one end face of the main head to cooperate with the sub-head, and a mounting flange is fixed on the outer peripheral side of the main head for mounting on an extruder.

[0015] Compared with the prior art, the present invention provides a multi-layer composite pipe and its preparation method and preparation device, having the following beneficial effects: 1. For the multi-layer composite pipe and its preparation method and preparation device, the outer layer can enhance the durability and aesthetics of the pipe, and even add functions such as antibacterial and flame retardant; the adhesive layer ensures the firm bonding between layers, increases the antioxidant performance of the adhesive, avoids the reduction of the bonding performance due to oxidation, and prevents delamination; while the special inner layer adjusts the proportion and addition or subtraction of the special material according to the situation of the conveyed medium, so as to meet the specific requirements of the industry.

[0016] 2. The multi-layer composite pipe, its preparation method and preparation device. Through the setting of the marking layer, the marking layer is slightly higher than the outer layer. When it is buried underground or installed, it increases a certain amount of friction to prevent the pipe from rotating and twisting. Moreover, the additional marking layer also increases the strength of the pipe. The marking layer can also make the pipe easier to manage and identify through different arrangements of its colors.

[0017] 3. The multi-layer composite pipe, its preparation method and preparation device. By modularizing the extrusion head, each additional installation of a sub-head can increase the number of layers of the pipe by one layer, enabling subsequent expansion of the sub-head. When the user needs a pipe with more layers, they only need to install the corresponding model sub-head again behind the second sub-head to complete the expansion, enabling the user to greatly conveniently select and produce pipes with different numbers of layers without having to purchase a new multi-layer head, thus increasing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic radial cross-sectional structure diagram of the product of the present invention; Figure 2 is a schematic axial cross-sectional structure diagram of the product of the present invention; Figure 3 is a layout diagram of the production line equipment of the present invention; Figure 4 is a process flow diagram of the production of the present invention; Figure 5 is a three-dimensional structure diagram of the extrusion head of the present invention; Figure 6 is a cross-sectional structure diagram of the extrusion head of the present invention; Figure 7 For the present invention Figure 6 is an enlarged structure diagram of part A in; Figure 8 For the present invention Figure 6 is an enlarged structure diagram of part B in; Figure 9 is a cross-sectional structure diagram of the sub-head of the present invention.

[0019] In the figure: 10, main head; 101, blank inlet; 102, main installation port; 103, installation flange; 11, forming cavity; 20, main core pipe; 201, main connection groove; 21, installation bolt; 30, first sub-head; 301, first extrusion cavity; 302, first forming groove; 303, first installation port; 304, first connection block; 31, first external interface; 40, second sub-head; 401, second extrusion cavity; 402, second forming groove; 403, second installation port; 404, second connection block; 41, second external interface; 50, sub-core pipe; 501, connecting convex block; 502, connecting groove; 60, inner layer; 61, bonding layer; 62, outer layer; 63, marking layer. Detailed Implementation Modes

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Embodiment 1

[0021] As Figure 1-2 shown, a multi-layer composite pipe includes an inner layer 60, an adhesive layer 61, an outer layer 62, and a marking layer 63. The adhesive layer 61 is located between the inner layer 60 and the outer layer 62, and the marking layer 63 is located on the outer peripheral side of the outer layer 62. There are at least two marking layers 63, and they are evenly distributed circumferentially on the outer layer 62.

[0022] The raw materials of the outer layer 62 are composed of 90 parts of HDPE, 3 parts of pigment, 2 parts of UV stabilizer, and 5 parts of calcium carbonate filler. The material of the adhesive layer 61 is composed of 75 parts of epoxy resin, 15 parts of calcium carbonate, and 10 parts of antioxidant. The material of the inner layer 60 is 85 parts of HDPE, 7 parts of nitrile rubber, and 8 parts of modified ester plasticizer; Among them, the thickness of the inner layer 60 is 0.16 mm, the thickness of the adhesive layer 61 is 0.08 mm, and the thickness of the outer layer 62 is 0.16 mm.

[0023] As the outermost structure of the pipe, the outer layer not only provides necessary protection for the internal components, enhances the durability and aesthetics of the pipe, but also can integrate various functional characteristics according to specific application scenarios. Therefore, by increasing the proportion of HDPE, the pressure resistance, antibacterial, flame retardant, and corrosion resistance of the pipe can be effectively improved. Then, different colored pigments can be added to make the pipe more beautiful and recognizable, and it is also convenient for management.

[0024] As the key of the whole structure, the adhesive layer ensures the tight combination between layers to form a solid whole. It requires the high-strength bonding force of epoxy resin to ensure no separation risk between layers. Then, antioxidants are added to increase the antioxidant performance of the adhesive and avoid the reduction of bonding performance due to oxidation.

[0025] The inner layer is in direct contact with the conveying medium, and the functional properties of the pipe are further enhanced through the synergistic effect of special HDPE and additives. According to different industry requirements, the proportion and addition or subtraction of special properties can be adjusted to meet the specific requirements of the industry.

[0026] By setting the marking layer slightly higher than the outer layer, when it is buried deep underground or installed, it increases a certain amount of friction to prevent the pipeline from rotating and twisting. Moreover, the additional marking layer also increases the strength of the pipeline. The marking layer can also make the pipe material easier to manage and identify through different arrangements of its colors. Example 2

[0027] As Figure 3 and 4 shown, a method for preparing a multi-layer composite pipe includes the following steps: S1: Select the raw materials required for the inner layer 60, adhesive layer 61, and outer layer 62 in corresponding amounts respectively, and perform preliminary drying. S2: Put the prepared raw materials into the corresponding mixer, that is, mix and dry the raw materials of the inner layer 60 and the outer layer 62 respectively. Raise the mixing and drying temperature to 120 °C, and then cool it to 40 - 50 °C. S3: After mixing and stirring, the raw materials of the inner layer 60 are transported to the inner layer extruder through a conveyor, the raw materials of the adhesive layer 61 are directly transported to the adhesive extruder through a conveyor, and the raw materials of the outer layer 62 are transported to the outer layer extruder through a conveyor. Control the extrusion temperature of the outer layer to be 180 - 200 °C, the extrusion temperature of the inner layer to be 190 - 210 °C, and the extrusion temperature of the adhesive layer to be 200 - 220 °C. S3: The extruded raw materials are input into the die head of the multi-layer extruder layer by layer, and then the blank of the multi-layer pipe can be extruded. While the blank is being extruded, the marking layer 63 is adhered to the blank through the marking strip extruder. S4: The extruded blank first enters the shaping and cooling equipment for preliminary shaping. The cooling temperature of the shaping and cooling equipment is 25 - 40 °C, and then it enters the cooling equipment, and the cooling temperature is 15 - 20 °C. S5: The shaped pipe is input into the traction power equipment. Its traction rate corresponds to the extrusion rate, and the traction ratio is greater than 1, that is, the ratio of the traction rate to the extrusion rate is 1.1 - 1.5. S6: The formed pipe products are cut according to the required length, and then collected together for storage.

[0028] The selection of raw materials for the outer layer and the inner layer can be determined according to specific functional designs. The selection of the types and quantities of components can be decided according to product characteristics. For multi-component materials, they can be mixed in a specific proportion and then dried; for single-component materials, it can be chosen whether to pre-dry them as needed, or directly skip the drying step. After the above-mentioned treatment, whether it is multi-component or single-component materials, they will be evenly mixed by a mixer and then transported to an extruder for the next processing step. Example 3

[0029] As Figures 5-9As shown in the figure, it includes an extrusion head and a mandrel. The extrusion head is sleeved on the mandrel. The extrusion head includes a main head 10 and several detachable sub - heads. The extrusion head is modularized. Each additional sub - head installed can increase the number of layers of the pipe by one layer. Seals are used to seal between the heads. The main head 10 is installed on the extruder. The sub - heads include a first sub - head 30 and a second sub - head 40. Among them, the first sub - head 30 is movably connected to the main head 10, and the second sub - head 40 is installed on the first sub - head 30. Both the first sub - head 30 and the second sub - head 40 are hollow and sleeved on the mandrel. An annular first extrusion cavity 301 and a first forming groove 302 are provided in the first sub - head 30. The first forming groove 302 communicates with its hollow part. A first installation port 303 is provided on one end face of the first sub - head 30, and a first connection block 304 is fixed on the other end face. The first connection block 304 is installed together with the main head 10. The installation method can be threaded connection, and the connection part is sealed. A first external interface 31 is also provided on the outer peripheral side of the first sub - head 30. Among them, the first external interface 31 can be installed on another extruder through a connecting pipe to extrude different materials, such as adhesives, etc. The first external interface 31 communicates with the first extrusion cavity 301; A second extrusion cavity 401 and a second forming groove 402 are provided in the second sub - head 40. The second forming groove 402 communicates with its hollow part. A second installation port 403 is provided on one end face of the second sub - head 40, and a second connection block 404 is fixed on the other end face. The second connection block 404 is installed together with the first installation port 303 and is also connected by a threaded connection. The connection part is sealed. A second external interface 41 is also provided on the outer peripheral side of the second sub - head 40. The second external interface 41 communicates with the second extrusion cavity 401. Other extruders are connected through pipes on the second external interface 41 to add an additional protective layer for the external protection of the pipe. Through the settings of the first sub - head 30 and the second sub - head 40, two additional protective layers can be added to the pipe to improve the performance of the pipe. Through the setting of the second installation port 403, the sub - head can be further expanded. When the user needs pipes with more layers, only a corresponding - type sub - head needs to be installed again behind the second sub - head 40 to complete the expansion, enabling the user to conveniently select and produce pipes with different numbers of layers without purchasing a new multi - layer head, thus increasing costs.

[0030] Since the structure of the sub - head is simple and similar, not much technical support is required for producing this head, so the raw material cost of the head will be greatly reduced. Therefore, when the user produces pipes, this head will greatly reduce costs.

[0031] The radius length at the end of the first forming groove 302 away from the first extrusion cavity 301 is smaller than the radius length at the end of the second forming groove 402 away from the second extrusion cavity 401. The thicknesses of the first extrusion cavity 301 and the second extrusion cavity 401 are both greater than those of the first forming groove 302 and the second forming groove 402, and both the first extrusion cavity 301 and the second extrusion cavity 401 are inclined. The inclined setting causes the raw materials to gradually gather during extrusion. Then, when passing through the parallel part of the first forming groove 302, they will be gradually shaped and then adhered to the outer wall of the underlying pipe. At the ends of the first forming groove 302 and the second forming groove 402, there are raised inclined rings. When the raw materials are extruded onto the pipe, they will be further slightly compressed to ensure that the extruded raw materials can completely adhere to the pipe, avoiding the separation of adjacent two layers of pipes and reducing the performance of the pipe.

[0032] Near the inlet of each sub-pipe, a cooling mechanism is provided to initially shape and harden the extruded pipe, avoiding mixing when the next layer of extruded raw materials adheres to the pipe because both have relatively soft textures.

[0033] The mandrel includes a main core tube 20 and several sub-core tubes 50. The main core tube 20 is installed on the extruder through mounting bolts 21. The sub-core tubes 50 are installed on the main core tube 20. A main connection groove 201 is opened at the center of the main core tube 20. The mounting bolts 21 are also rotatably arranged at the center of the main core tube 20, and one side of the mounting bolts 21 is located within the main connection groove 201. On one side end face of the sub-core tube 50, a connecting lug 501 is fixed and detachably installed within the main connection groove 201 through the connecting lug 501. On the other side end face, a connecting groove 502 is opened. The part of the main core tube 20 close to the sub-core tube 50 has the same radius as the sub-core tube 50. Installing the sub-core tubes 50 on the main core tube 20 can increase the overall length of the mandrel, avoiding the deformation of the pipe caused by the lack of mandrel support for an overly long sub-head. And through the connecting groove 502, another sub-core tube 50 can be installed. The connecting lug 501 of this sub-core tube 50 cooperates with the connecting groove 502 of the previous sub-core tube 50 to complete the extension of the mandrel.

[0034] At the middle of the main head 10, a blank inlet 101 is opened. A forming cavity 11 is formed between the blank inlet 101 and the main core tube 20 for blank extrusion. On one side end face of the main head 10, a main mounting port 102 is opened to cooperate with the sub-head. On the outer peripheral side of the main head 10, a mounting flange 103 is fixed for installation on the extruder. The set length of the mounting bolts 21 should be greater than the length of the main core tube 20 to ensure that the main core tube 20 has sufficient support force and avoid bending it when installing the sub-core tubes 50 later, resulting in uneven thickness of the pipe.

[0035] Working principle: During use, install the main machine head 10 and the main core pipe 20 at the corresponding positions at the outlet of the extruder. When two-layer pipes are required, screw the first auxiliary head 30 onto the main machine head 10. At this time, the length of the main core pipe 20 is the same as the lengths of the main machine head 10 and the first auxiliary head 30. Then, the raw materials required for the outer layer are connected to the first outer interface 31 through another extruder. Then, the main extruder extrudes the raw materials into the forming cavity 11 to form a layer of pipe. When the pipe passes through the first auxiliary head 30, the raw materials extruded by the first auxiliary head 30 will adhere to the first-layer pipe to form a double-layer pipe.

[0036] When three-layer pipes are required, first install the auxiliary core pipe 50 on the main core pipe 20, and then install the second auxiliary head 40 on the first auxiliary head 30. At this time, when the double-layer pipe formed after extrusion by the first auxiliary head 30 passes through the second auxiliary head 40, the pipe extruded inside the second auxiliary head 40 adheres to the outermost side, and then a three-layer pipe is formed. When more layers of pipes are required subsequently, the corresponding auxiliary heads can be directly installed, and the operation is more convenient and fast.

[0037] In summary, for this multi-layer composite pipe and its preparation method and preparation device, through the setting of the adhesive layer, it ensures the tight combination between layers and forms a solid whole. It requires the high-strength bonding force of epoxy resin to ensure no separation risk between layers. Then, antioxidant is added to improve the antioxidant performance of the adhesive and prevent its oxidation from reducing the bonding performance. By modularizing the extrusion head, each additional installation of an auxiliary head can increase the number of pipe layers by one, enabling subsequent expansion of the auxiliary head. When the user needs pipes with more layers, they only need to install the corresponding auxiliary head of the corresponding model behind the second auxiliary head 40 to complete the expansion, enabling the user to conveniently select and produce pipes with different numbers of layers without purchasing a new multi-layer head, thus increasing the cost.

[0038] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising a..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the element.

[0039] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multi-layer composite pipe, characterized in that: It includes an inner layer (60), an adhesive layer (61), an outer layer (62) and a marking layer (63). The adhesive layer (61) is located between the inner layer (60) and the outer layer (62), and the marking layer (63) is located on the outer peripheral side of the outer layer (62). There are at least two marking layers (63), which are evenly distributed circumferentially on the outer layer (62).

2. The multi-layer composite pipe according to claim 1, wherein: The raw materials of the outer layer (62) are HDPE, UV stabilizer, calcium carbonate filler and pigment. The materials of the adhesive layer (61) include epoxy resin, calcium carbonate and antioxidant. The materials of the inner layer (60) are HDPE, nitrile rubber and modified ester plasticizer; Among them, the thickness of the inner layer 60 is 0.15 - 0.2 mm, the thickness of the adhesive layer 61 is 0.04 - 0.1 mm, and the thickness of the outer layer 62 is 0.16 - 2.2 mm.

3. A method for preparing a multi-layer composite pipe applicable to claim 1 or 2, characterized in that: It includes the following steps: S1: Select the raw materials required for the inner layer 60, the adhesive layer 61 and the outer layer 62 in corresponding amounts respectively, and conduct preliminary drying. S2: Put the prepared raw materials into the corresponding mixer, that is, mix and dry the raw materials of the inner layer 60 and the outer layer 62 respectively. Raise the mixing and drying temperature to 120 °C, and then cool it to 40 - 50 °C. S3: After mixing and stirring, the raw materials of the inner layer 60 are conveyed into the inner layer extruder through a conveyor, the raw materials of the adhesive layer 61 are directly conveyed into the adhesive extruder through a conveyor, and the raw materials of the outer layer 62 are conveyed into the outer layer extruder through a conveyor. Control the extrusion temperature of the outer layer to be 180 - 200 °C, the extrusion temperature of the inner side to be 190 - 210 °C, and the extrusion temperature of the adhesive layer to be 200 - 220 °C. S4: The extruded raw materials are input into the die head of the multi-layer extruder layer by layer, and then the blank of the multi-layer pipe can be extruded. While the blank is being extruded, the marking layer 63 is adhered to the blank through the marking strip extruder. S5: The extruded blank first enters the shaping and cooling equipment for preliminary shaping. The cooling temperature of the shaping and cooling equipment is 25 - 40 °C, and then it enters the cooling equipment, and the cooling temperature is 15 - 20 °C. S6: The pipe after shaping is input into the traction power equipment. Its traction rate corresponds to the extrusion rate, and the traction ratio is greater than 1, that is, the ratio of the traction rate to the extrusion rate is 1.1 - 1.

5. S7: The formed pipe products are cut according to the required length, and then collected together for storage.

4. A head device for the preparation method of the multi-layer composite pipe applicable to claim 3, characterized in that: It includes an extrusion die head and a mandrel, and the extrusion die head is sleeved on the mandrel; The extrusion die head includes a main die head (10) and several detachable sub-die heads. The main die head (10) is installed on the extruder; The mandrel includes a main mandrel tube (20) and several sub-mandrel tubes (50). The main mandrel tube (20) is installed on the extruder through installation bolts (21), and the sub-mandrel tubes (50) are installed on the main mandrel tube (20).

5. The head device for the method of manufacturing a multi-layer composite pipe according to claim 4, characterized in that: The auxiliary head includes a first auxiliary head (30) and a second auxiliary head (40), wherein the first auxiliary head (30) is movably connected to the main head (10), the second auxiliary head (40) is installed on the first auxiliary head (30), and both the first auxiliary head (30) and the second auxiliary head (40) are hollow and sleeved on the mandrel.

6. The head device for the preparation method of a multi-layer composite pipe according to claim 5, characterized in that: An annular first extrusion cavity (301) and a first forming groove (302) are formed in the first auxiliary head (30), and the first forming groove (302) communicates with its hollow part; A second extrusion cavity (401) and a second forming groove (402) are formed in the second auxiliary head (40), and the second forming groove (402) communicates with its hollow part.

7. The head device for the method of manufacturing a multi-layer composite pipe according to claim 6, characterized in that: The radius length of the end of the first forming groove (302) far from the first extrusion cavity (301) is less than the radius length of the end of the second forming groove (402) far from the second extrusion cavity (401). The thicknesses of both the first extrusion cavity (301) and the second extrusion cavity (401) are greater than those of the first forming groove (302) and the second forming groove (402), and both the first extrusion cavity (301) and the second extrusion cavity (401) are inclined.

8. The head device for the method of manufacturing a multi-layer composite pipe according to claim 6, characterized in that: A first installation port (303) is formed on one end face of the first auxiliary head (30), and a first connection block (304) is fixed on the other end face. The first connection block (304) is installed together with the main head (10). A first external interface (31) is further provided on the outer peripheral side of the first auxiliary head (30), and the first external interface (31) communicates with the first extrusion cavity (301); A second installation port (403) is formed on one end face of the second auxiliary head (40), and a second connection block (404) is fixed on the other end face. The second connection block (404) is installed together with the first installation port (303). A second external interface (41) is further provided on the outer peripheral side of the second auxiliary head (40), and the second external interface (41) communicates with the second extrusion cavity (401).

9. The head device for the preparation method of a multi-layer composite pipe according to claim 4, characterized in that: A main connection groove (201) is formed at the center of the main core pipe (20), and the mounting bolt (21) is also rotatably arranged at the center of the main core pipe (20). One side of the mounting bolt (21) is located in the main connection groove (201); A connection convex block (501) is fixed on one end face of the auxiliary core pipe (50), and it is detachably installed in the main connection groove (201) through the connection convex block (501). A connection groove (502) is formed on the other end face. The part of the main core pipe (20) close to the auxiliary core pipe (50) has the same radius as the auxiliary core pipe (50).

10. The head device for the preparation method of a multi-layer composite pipe according to claim 4, characterized in that: A blank inlet (101) is formed in the middle of the main head (10). A forming cavity (11) is formed between the blank inlet (101) and the main core pipe (20) for blank extrusion. A main installation port (102) is formed on one end face of the main head (10) to cooperate with the auxiliary head. An installation flange (103) is fixed on the outer peripheral side of the main head (10) for installation on an extruder.

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