Forming method of multi-layer composite pipe

Abstract

The invention provides a forming method of a multi-layer composite pipe, which comprises the following steps: forming a composite blank which comprises a molten auxiliary forming layer and low-friction layer powder attached to at least one side of the molten auxiliary forming layer; the low-friction-resistance layer powder is heated, so that a molten-state low-friction-resistance layer is formed on at least one side of the molten-state auxiliary forming layer; the molten-state auxiliary forming layer and the molten-state low-friction-resistance layer are formed into a composite pipe; wherein the friction resistance coefficient M of the low-friction-resistance layer is smaller than that of the outer surface layer of the pipe wall, and the low-friction-resistance layer is made of an ultra-high molecular weight polymer and an antioxidant. The forming efficiency of the pipe can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer pipe forming, and in particular to a forming method of a multi-layer composite pipe. BACKGROUND

[0002] With the acceleration of urbanization, the demand for water and the amount of sewage are increasing, and the requirements for environmental protection and public health are also increasing, which promotes the continuous improvement and expansion of water supply and sewage pipeline systems, forming a complex and huge pipeline network system, including service pipes, branch pipes, trunk pipes, main pipes, inspection wells, pump stations and other auxiliary structures.

[0003] Taking the sewage pipeline system as an example, the sewage may contain various solid impurities, oils, chemical reactants, etc., which are easy to precipitate and accumulate in the pipeline, causing pipeline blockage. In order to solve this problem, the existing technology needs to clean and dredge the sewage pipeline regularly, increasing the maintenance cost and workload. Therefore, there is a lack of a pipe material that can reduce friction and reduce the accumulation of attachments in the existing technology, which is difficult to meet the needs of efficient operation and low-cost maintenance of the pipeline system in the process of urbanization. SUMMARY

[0004] The purpose of the present application is to provide a forming method of a multi-layer composite pipe, which can efficiently prepare a multi-layer composite pipe with a low-friction layer, thereby improving the problem of high cost.

[0005] In one aspect, the present application provides a forming method of a multi-layer composite pipe, forming a composite blank, the composite blank including a molten auxiliary forming layer and a low-friction layer powder attached to at least one side of the molten auxiliary forming layer; heating the low-friction layer powder to form a molten low-friction layer on at least one side of the molten auxiliary forming layer; forming the molten auxiliary forming layer and the molten low-friction layer into a composite pipe; wherein the friction coefficient M of the low-friction layer is less than the friction coefficient of the outer layer of the composite pipe, and the material of the low-friction layer includes: an ultra-high molecular weight polymer and an antioxidant. In addition, the material of the low-friction layer can also include: low-density linear polyethylene and other additives.

[0006] In some embodiments, the above method further includes: after heating the low-friction layer powder, forming a molten wide-specification polymer layer on the side of the composite blank away from the low-friction layer.

[0007] In some embodiments, the above method further includes: after forming the wide-specification polymer layer, forming a molten outer layer of the composite pipe on the side of the molten wide-specification polymer layer away from the low-friction layer.

[0008] In some embodiments, the wide-gauge polymer layer has a foaming agent, and the method further comprises: after forming the molten wide-gauge polymer layer on the side of the low-friction layer opposite to the composite pipe outer layer, extruding the composite pipe outer layer and the auxiliary forming layer in a foaming process.

[0009] In some embodiments, forming the composite green material comprises: delivering the modified low-friction layer powder into the first composite forming die; covering the molten auxiliary forming layer on the modified low-friction layer powder in the first composite forming die to form the composite green material; and heating the low-friction layer powder comprises heating the modified low-friction layer powder by the core die in the first composite forming die and the molten auxiliary forming layer.

[0010] In some embodiments, forming the composite green material comprises: extruding the auxiliary forming layer; adding the modified low-friction layer powder on the un-cooled and solidified auxiliary forming layer to obtain an initial composite green material; pressing the initial composite green material to form the composite green material; and heating the low-friction layer powder comprises: contact heating the side of the auxiliary forming layer opposite to the low-friction layer powder, and contact and / or non-contact heating the side of the auxiliary forming layer opposite to the low-friction layer powder.

[0011] In some embodiments, forming the composite green material further comprises: after heating the low-friction layer powder, repeating at least once: adding the modified low-friction layer powder on the side of the low-friction layer powder of the composite green material; pressing the composite green material; and heating the low-friction layer powder.

[0012] In some embodiments, forming the composite pipe by the molten auxiliary forming layer and the molten low-friction layer comprises: extruding the molten auxiliary forming layer and the molten low-friction layer by a pipe forming die to obtain the composite pipe; and wherein the pipe forming die has a circular cross-section; or the cross-section of the pipe forming die has a first cross-sectional area larger than a second cross-sectional area, the first cross-sectional area being an area of a half cross-section of the composite pipe in a post-laying state away from the earth center, and the second cross-sectional area being an area of a half cross-section of the composite pipe in the post-laying state close to the earth center.

[0013] In some embodiments, forming the composite pipe by the molten auxiliary forming layer and the molten low-friction layer comprises: extruding the molten auxiliary forming layer and the molten low-friction layer by a pipe forming die to obtain the composite pipe; and wherein the pipe forming die has a circular cross-section; or the cross-section of the pipe forming die has a first cross-sectional area larger than a second cross-sectional area, the first cross-sectional area being an area of a half cross-section of the composite pipe in a post-laying state away from the earth center, and the second cross-sectional area being an area of a half cross-section of the composite pipe in the post-laying state close to the earth center.

[0014] In some embodiments, the winding the composite pipe material to form a spiral structure of the composite pipe material comprises: winding the composite pipe material on a column with a specific cross-sectional shape; and wherein the specific cross-sectional shape is a circular shape; or the first cross-sectional area of the specific cross-sectional shape is greater than the second cross-sectional area, the first cross-sectional area being the area of the half cross-section of the composite pipe material away from the side of the earth in the post-laying state, and the second cross-sectional area being the area of the half cross-section of the composite pipe material close to the side of the earth in the post-laying state.

[0015] The forming method of the multi-layer composite pipe material provided by the embodiment of the present application can improve the manufacturing efficiency of the low-friction layer by sintering the low-friction material powder attached to the side of the auxiliary forming layer close to the axis of the pipe material, so as to improve the manufacturing efficiency of the low-friction layer by means of the auxiliary forming layer. Taking ultra-high molecular weight polyethylene (UHMWPE) as an example, because the UHMWPE molecular chain is extremely long and there are many random entanglements between the chains, the melt viscosity is extremely high, and the forming efficiency is only about 1% of that of ordinary plastic pipe products. The embodiment can improve the forming efficiency of the material with extremely high viscosity such as UHMWPE by several times to several tens of times by dragging the low-friction layer powder through the auxiliary forming layer and then heating to form the multi-layer composite pipe material, thereby greatly reducing the time cost of production and manufacturing.

[0016] According to the embodiment of the present application, the special-shaped pipe material structure is designed to accelerate the flow speed of the liquid at the bottom of the pipe material, improve the scouring intensity of the liquid flow on the area prone to deposition, and further reduce the risk of pipeline blockage.

[0017] According to the embodiment of the present application, the special-shaped pipe material is prone to deformation under the action of its own gravity and the gravity of the soil sealing, which reduces the expected effect, such as reducing the scouring intensity of the liquid flow on the area prone to deposition. By increasing the wide-specification material in the composite pipe material of the pipe material, the strength of the composite pipe material of the pipe material can be effectively increased without significantly increasing the self-weight of the pipe material, thereby improving the problem of pipe material deformation. In addition, by using the wide-specification material, the raw material cost can be effectively reduced. If the wide-specification material is a foamed material, it can play a role such as heat insulation, stress dispersion, vibration absorption, noise reduction, etc. For example, the foamed layer is a microcellular foamed layer, which will not significantly reduce the mechanical strength of the layer due to foaming. The microcellular foamed layer builds hoop stress during the forming process, which can control the sagging during the production of polyolefin material and the self-weight creep rate during the use of the product after forming.

[0018] According to the embodiment of the present application, the composite pipe material system has a self-cleaning effect, which can effectively improve the pipe material blockage problem and reduce the cost of actively maintaining the pipe material system.

[0019] According to the embodiment of the present application, the forming equipment of the multi-layer composite pipe can improve pipe forming efficiency by several to several dozen times under the premise of ensuring the self-cleaning function of the pipe by co-extruding the auxiliary forming layer and the low friction layer powder, and the molecular orientation of the low friction layer of the pipe is consistent, which can effectively improve the mechanical properties of the low friction layer.

[0020] According to the embodiment of the present application, the forming equipment of the multi-layer composite pipe can improve pipe forming efficiency by several to several dozen times under the premise of ensuring the self-cleaning function of the pipe by co-extruding the auxiliary forming layer and the low friction layer powder, and the molecular orientation of the low friction layer of the pipe is consistent, which can effectively improve the mechanical properties of the low friction layer.

[0021] According to the embodiment of the present application, compared with the existing high-density polyethylene solid-wall pipe end face welding, the self-cleaning multi-layer composite pipe with an ultra-high molecular weight polyethylene inner layer has no molten material flange on the inner surface of the pipe during the welding of the two end faces of the pipe, while the existing high-density polyethylene solid-wall pipe has molten material flange on the inner surface of the pipe after the end face welding. When the pipe with an ultra-high molecular weight polyethylene inner layer is welded at the end face, the difficult-to-flow ultra-high molecular weight polyethylene inner layer will prevent the molten material from flowing to the inner surface of the pipe, thereby connecting the pipeline without molten material flange on the inner surface, and preventing the accumulation of fouling on the inner surface of the pipe at the connection position.

[0022] The ultra-high molecular weight polyethylene powder is driven forward by the auxiliary forming layer, and the powder is directly melted in situ by the auxiliary heater and the auxiliary forming layer, without strong shearing of the ultra-high molecular polyethylene molecular chain, which avoids the performance reduction caused by the chain scission of the ultra-high molecular weight polyethylene molecular chain in the plasticizing process of the existing conventional screw extrusion technology, and at the same time, the in-situ direct melting and auxiliary driving of the ultra-high molecular weight polyethylene can greatly improve the production efficiency.

[0023] Further, in order to realize the extrusion of the ultra-high molecular weight polyethylene, the existing technology adds a processing modifier to the ultra-high molecular weight polyethylene to realize the extrusion process, which will cause performance reduction; the technology of the present application can realize the rapid melting and extrusion of the ultra-high molecular weight polyethylene without adding a processing modifier to the ultra-high molecular weight polyethylene; the use of ultra-high molecular weight powder without adding a processing modifier for direct in-situ forming can more easily prepare a pipe inner wall layer with a low friction coefficient, such as a friction coefficient less than 0.15.

[0024] By this technology, the non-helix discontinuous rotation movement of the helical conveyor of the forming equipment can make the ultra-high molecular weight polyethylene oriented in the radial direction (or ring direction) of the pipe, which can improve the mechanical properties of the pipe. Meanwhile, through the axial pushing and pulling action of the internal sizing device, the molecular chains of the ultra-high molecular weight polyethylene layer on the inner wall of the pipe are oriented in the axial direction of the pipe, which further improves the mechanical properties of the pipe and obtains a pipe inner surface with low friction coefficient. Through the above radial (ring) and axial orientation methods, a pipe inner layer with ultra-high molecular weight polyethylene molecular chains oriented in the radial direction and the axial direction can be obtained, wherein the axial orientation layer is located on the side of the axial center line of the pipe, and the radial orientation layer is located on the outer surface of the axial orientation layer. During the forming process, the radial orientation layer is obtained first, and then the axial orientation layer is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 shows a partial schematic view of a cross section of a multi-layer composite pipe;

[0026] Figure 2 shows a schematic view of the deformation of an egg-shaped pipe under the action of gravity;

[0027] Figure 3 shows a partial schematic view of a cross section of another multi-layer composite pipe;

[0028] Figure 4 shows a schematic view of a cross section of a multi-layer composite pipe;

[0029] Figures 5 to 20 shows a schematic view of a cross section of a multi-layer composite pipe;

[0030] Figures 21 to 29 shows a schematic view of a cross section of a multi-layer composite pipe;

[0031] Figures 30 to 32 shows a schematic view of a cross section of a multi-layer composite pipe with a support structure;

[0032] Figure 33 shows a flow chart of a method for forming a multi-layer composite pipe.

[0033] Figure 34 shows a flow chart of another method for forming a multi-layer composite pipe.

[0034] Figure 35 shows a composite pipe forming device;

[0035] Figure 36 shows a composite blank forming system;

[0036] Figure 37 shows a cross-sectional schematic view of a composite blank forming system;

[0037] Figure 38A cross-sectional view of a co-extrusion port of a composite blank forming system is shown;

[0038] Figure 39 A schematic view of a screw conveyor is shown;

[0039] Figure 40 A schematic view of a composite pipe forming system is shown;

[0040] Figure 41 A cross-sectional view of a composite pipe forming system is shown;

[0041] Figure 42 A schematic view of another composite pipe forming apparatus is shown;

[0042] Figure 43 A schematic view of an extrusion press system for a composite tape is shown;

[0043] Figure 44 A schematic view of an extrusion forming system for a first composite structure is shown;

[0044] Figure 45 A schematic view of a powder feeder is shown;

[0045] Figure 46 A schematic view of a press apparatus is shown;

[0046] Figure 47 A schematic view of a heating apparatus is shown;

[0047] Figure 48 A schematic view of a tape sizing die is shown;

[0048] Figure 49 A cross-sectional view of a tape sizing die is shown;

[0049] Figure 50 A schematic view of a screw feeder is shown;

[0050] Figure 51 A schematic view of a rotating portion of a screw feeder is shown;

[0051] Figure 52 A cross-sectional view of a screw feeder is shown;

[0052] Figure 53 A schematic view of a composite pipe forming system is shown;

[0053] Figure 54 A schematic view of an extrusion forming system for a second composite structure is shown;

[0054] Figure 55 A schematic view of an outer die body is shown;

[0055] Figure 56 A schematic view of an inner die body is shown;

[0056] Figure 57 schematic view of an external sizing device;

[0057] Figure 58 schematic view of an external sizing device and a pipe cooling sizing device;

[0058] Figure 59 schematic view of an internal sizing device;

[0059] Figure 60 schematic view of an internal sizing device;

[0060] Figure 61 flow chart showing a method of improving clogging using composite pipe;

[0061] Figure 62 schematic view of pipe loading force;

[0062] Figure 63 schematic view of finite element analysis stress results for a round pipe;

[0063] Figure 64 schematic view of finite element analysis stress results for an egg-shaped pipe;

[0064] Figure 65 schematic view of finite element analysis stress results for a Figure 5 schematic view of finite element analysis stress results for a

[0065] Figure 66 schematic view of finite element analysis stress results for a Figure 8 schematic view of finite element analysis stress results for a

[0066] Figure 67 schematic view of finite element analysis stress results for a Figure 17 schematic view of finite element analysis stress results for a

[0067] Figure 68 schematic view of finite element analysis stress results for a Figure 11 schematic view of finite element analysis stress results for a DETAILED DESCRIPTION

[0068] Embodiments of the present application will be described in greater detail below with reference to the accompanying drawings. While only preferred embodiments of the application are described in detail, it should be understood that the application is not limited to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The application is capable of other embodiments and of being practiced or being carried out in various ways.

[0069] The terminology used by the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the terms "comprises", "comprising", "includes", "including" and the like are specifically intended to be open-ended. These terms mean that a feature, step, operation, and / or component can be present or added, but not excluded, without further altering the base description.

[0070] It should be understood that although the present application can employ the terms "first", "second", "third", etc. to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information without departing from the scope of the present application. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0071] All terms used herein, including technical and scientific terms, have the meanings commonly understood by one of ordinary skill in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted to have meanings consistent with the context of the present specification, and should not be interpreted in an idealized or overly formal manner.

[0072] For example, the term "co-extrusion" used by the present application is used according to its generally accepted definition, i.e. it relates to a single-step process starting from two or more polymeric materials, which are simultaneously extruded and shaped in a single die to form a multilayer pipe or sheet.

[0073] Melt state polymer material refers to the state of a polymer material when it is heated above its melting point or softening point, and changes from a solid state to a liquid state with flowability. During this process, the interaction between polymer chains is partially overcome, and the molecular chains can move relatively freely.

[0074] In order to facilitate the understanding of the technical solutions of the present application, first, the development status of the pipe material technical field is introduced and explained. The present application is based on the following facts to explain the technical solutions.

[0075] Pipeline clogging, especially sewage pipeline clogging, is a common and complex problem in the pipeline network system, which can be caused by at least one of the following factors: sediment deposition, debris accumulation, grease attachment and condensation, chemical reaction and precipitation, etc. The causes of debris accumulation may include: mixing of household garbage, construction waste, tree roots penetrating from the pipe material connection, etc.

[0076] For example, in daily life, some large or non-biodegradable items such as plastic bottles, sanitary napkins, and wet wipes are mistakenly discharged into sewage pipes. These items cannot degrade naturally in the pipes and gradually accumulate as water flows through bends, changes in pipe diameter, or areas where the flow rate slows, eventually causing blockages. Residents of some older communities have a weak sense of environmental protection and carelessly discard trash, which easily leads to pipe blockages over time. Furthermore, during construction, if the construction company is not well-managed, construction waste such as concrete blocks, bricks, and gravel may enter the sewage pipes. Because of their large size and weight, this waste easily settles at the bottom of the pipes, obstructing the normal flow of sewage. When construction is carried out around newly built residential areas, if the construction company fails to properly treat wastewater discharge, construction waste may flow into the community's sewage pipes, causing blockages.

[0077] For example, there's the issue of wastewater discharge from the catering industry: large amounts of oily wastewater from restaurants, canteens, and other food service establishments are discharged directly into sewage pipes without effective treatment. As the water temperature decreases inside the pipes, the grease gradually solidifies, adhering to the inner walls and forming a thick layer of grease. This not only reduces the pipe's cross-sectional area but also absorbs other impurities from the wastewater, further exacerbating pipe blockage. In many older urban areas, where restaurants are concentrated and effective grease traps are not installed, sewage pipes are frequently blocked by grease buildup.

[0078] In addition, pipe damage and deformation: Sewage pipes are subject to long-term external pressure, foundation settlement, corrosion, and other factors, which may lead to damage and deformation. Inadequate sealing at pipe joints allows surrounding soil and tree roots to enter the pipes; localized depressions or bulges in the pipes alter the sewage flow velocity, easily causing debris accumulation. Some sewage pipes that have been laid for a long time have experienced ruptures and deformations due to changes in groundwater levels and the impact of construction on surrounding buildings, leading to blockages.

[0079] In addition, chemical reactions and precipitation are also a contributing factor to pipe blockages. Industrial wastewater contains a large number of chemical substances, such as heavy metal ions, acids, and alkalis. When different types of industrial wastewater are mixed, or when mixed with domestic sewage, chemical reactions may occur, producing precipitates. These precipitates accumulate in the pipes, causing blockages. Sewage pipes around chemical industrial parks frequently experience blockages due to chemical precipitation because they receive various types of industrial wastewater.

[0080] Current technologies for addressing pipe clogging issues primarily employ proactive maintenance in municipal pipeline maintenance. This includes regular maintenance of main pipelines, manual repairs after clogging occurs, and the installation of proactive cleaning equipment for daily inspections. For high-value-added product pipelines, specialized materials can be used to reduce the risk of clogging. For example, oil pipelines can utilize chemically stable materials with low friction coefficients. However, taking UHMWPE as an example, its material cost is significantly higher than ordinary polymer pipes. In particular, molten UHMWPE has extremely high viscosity, resulting in a molding efficiency only about 1% of that of ordinary plastic pipes, making its widespread adoption and large-scale application difficult.

[0081] Specifically, UHMWPE has been widely used in practical engineering and daily life, especially in pipe manufacturing, where it can replace some steel pipes and play a very important role in oil and gas storage and transportation. UHMWPE is a thermoplastic engineering plastic with excellent comprehensive performance. Current molding and processing technologies are carried out in the molten state; therefore, its flowability at the viscous flow temperature is the main factor affecting its molding and processing performance. Due to the extremely long molecular chains of UHMWPE and the numerous random entanglements between chains, its aggregated structure generates many amorphous microregions, resulting in extremely high melt viscosity and making relative displacement of molecular chains relatively difficult. Existing research indicates that the main factors affecting the flowability of UHMWPE include additives, flow field parameters, and macromolecular structure.

[0082] The performance indicators for measuring polymer flowability include melt flow rate (MFR) and viscosity. Due to the extremely high melt viscosity of UHMWPE, additives can be added to improve its melt flowability, making it easier to mold and process. The additives used mainly include fillers, plasticizers, and lubricants. These additives have the most significant effect on improving the molding and processing performance of UHMWPE. UHMWPE generally cannot be molded on ordinary extruders and injection molding machines, but with the addition of appropriate additives, its molding and processing performance is significantly improved, allowing it to be molded using ordinary extruders and injection molding machines. However, excessive additives may degrade some of the excellent properties of UHMWPE. Table 1 shows some examples of single-walled pipes.

[0083] Table 1

[0084]

[0085]

[0086] For example, for single-layer solid-wall pipes, as shown in Table 1, the material with a wall thickness of E1 is composed of polymer materials and their modified materials, such as one or a combination of high-density polyethylene (HDPE), polypropylene (PP), and polyvinyl chloride (PVC).

[0087] Flow field parameters such as temperature, shear rate, static pressure, and flow channel shape have varying degrees of influence on the melt flowability during the UHMWPE molding process.

[0088] Specifically, the viscosity of UHMWPE decreases as temperature decreases, and the decrease becomes more pronounced with increasing temperature. However, due to the relatively low activation energy of UHMWPE, the effect of improving its flowability by increasing temperature is limited. Furthermore, the maximum service temperature of UHMWPE materials is typically limited to approximately 80°C to 100°C, as UHMWPE is prone to aging and degradation at high temperatures, losing its original properties. The molding temperature of UHMWPE is generally not higher than 380°C, for example, 350°C or 300°C.

[0089] Furthermore, the two-dimensional flow of molten UHMWPE is related to both the width and height of the cross-section. Different cross-sectional channel shapes result in different melt velocity magnitudes and directions, leading to varying flow properties of UHMWPE during molding. This adds new challenges to the co-extrusion molding of UHMWPE for manufacturing shaped tubes.

[0090] UHMWPE materials are sensitive to ultraviolet light; prolonged exposure to sunlight can lead to degradation and brittleness, limiting their application in outdoor environments. Furthermore, due to the chemical inertness of the UHMWPE surface, it does not readily form chemical bonds with other materials, resulting in poor adhesion. This can lead to weak bonding between UHMWPE and other materials during composite material manufacturing, affecting the composite's performance.

[0091] Although UHMWPE materials possess excellent abrasion resistance and impact resistance, their hardness and strength are relatively low. This limits their application in situations requiring heavy loads or high hardness.

[0092] For the reasons mentioned above, developing pipes with low maintenance and repair costs (reducing the occurrence of blockages), as well as low raw material and manufacturing costs, has become an urgent technical problem to be solved.

[0093] In embodiments of the present invention, a material with a low coefficient of friction is incorporated into the inner surface of the composite pipe to reduce the friction coefficient of the inner surface of the pipe, thereby reducing the possibility of blockage caused by sedimentation and accumulation within the pipe. Since some low-friction coefficient materials are significantly more expensive than ordinary pipe materials, the multi-layer composite pipe structure effectively reduces the consumption of expensive low-friction coefficient layer materials, thus effectively lowering the raw material cost of the pipe.

[0094] To improve the molding efficiency of the low-friction layer and further reduce molding costs, some embodiments of the present invention are formed by sintering low-friction material powder attached to an auxiliary molding layer. Taking UHMWPE as an example, by using the auxiliary molding layer to carry the low-friction layer powder, and then heating to form a multi-layer composite pipe, the molding efficiency of materials with extremely high viscosity such as ultra-high molecular weight polyethylene is significantly improved by several to tens of times, and the manufacturing time cost is greatly reduced.

[0095] In addition, by designing irregular pipe structures, the flow rate of liquid at the bottom of the pipe is accelerated, and the flushing force of the liquid flow on areas prone to sedimentation is increased, further reducing the risk of pipe blockage.

[0096] To increase the stability of irregularly shaped pipes, adding wider-gauge material to the pipe wall can effectively increase the pipe wall strength without significantly increasing the pipe's weight, thus mitigating pipe deformation and further reducing maintenance costs. Furthermore, adding wider-gauge material to the pipe wall can also reduce sag during the production process.

[0097] Correspondingly, the present invention also provides molding equipment for manufacturing the aforementioned multilayer composite pipe, which can significantly improve pipe molding efficiency while ensuring the reduction of pipe maintenance costs. Furthermore, the consistent molecular chain orientation of the low-friction layer in this pipe effectively enhances its mechanical properties.

[0098] See Figure 1 The diagram shows a partial schematic of the cross-section of a multi-layer composite pipe.

[0099] The composite pipe includes at least one pipe wall layer. This at least one pipe wall layer includes an outer wall layer and a low-friction layer. The low-friction layer is located on the outer wall layer near the pipe axis.

[0100] Composite pipes can be single-walled pipes, double-walled pipes, corrugated pipes, spiral wound pipes, or irregularly shaped pipes. For example, a composite pipe can be a double-walled corrugated pipe, where the corrugation includes a first pipe wall and a second pipe wall, with the first pipe wall located on the side of the second pipe wall closer to the pipe's axis. For example, a composite pipe can be a single-walled corrugated pipe. For example, a composite pipe can be a spiral wound pipe. For example, a composite pipe can be an irregularly shaped pipe. For example, a composite pipe can be a circular pipe. The friction coefficient of the low-friction layer is lower than that of the outer surface layer of the pipe wall. The material of the low-friction layer includes ultra-high molecular weight polymers and antioxidants.

[0101] In this embodiment, the ultra-high molecular weight polymer is ultra-high molecular weight polyethylene, and the friction coefficient of the low-friction layer is less than 0.15, such as 0.14, 0.13, or 0.12. The material composition of the low-friction layer includes ultra-high molecular weight polyethylene with a molecular weight greater than 1 million, such as 2 million, 3 million, or 4 million.

[0102] For example, ultra-high molecular weight polymers can be categorized into three main types: linear, branched, and cross-linked. Among these, linear supramolecular polymers represent the most common topological structure. Branched supramolecular polymers can be further subdivided into star-shaped, side-chain, and hyperbranched structures. Cross-linked supramolecular polymers can be classified according to their degree of regularity into random cross-linking and supramolecular organic frameworks.

[0103] Ultra-high molecular weight polyethylene (UHMWPE) is the most commonly used ultra-high molecular weight polymer. UHMWPE pipes are widely used in many fields due to their excellent properties such as wear resistance and chemical corrosion resistance. There are various manufacturing methods, each with its own characteristics in terms of production efficiency. The following provides illustrative examples of several manufacturing methods and their production efficiency characteristics.

[0104] Extrusion Molding: First, UHMWPE raw material is fed into the extruder hopper. Driven by the screw, the material enters the barrel. An external heating device heats the material, gradually melting and plasticizing it. The plasticized material is then extruded through a die of a specific shape under the screw's pressure, forming a preliminary pipe shape. Subsequently, a cooling device cools and solidifies the extruded pipe into the desired pipe product.

[0105] Extrusion molding is suitable for continuous production, and mass production can be achieved with automated feeding, cooling, and traction devices. However, UHMWPE melt has high viscosity and poor flowability, requiring higher extrusion pressure, which may limit the extrusion speed. Furthermore, changing to different pipe specifications requires replacing components such as dies, which consumes time and affects production efficiency. For example, some large-scale pipe manufacturers using advanced extrusion production lines can produce several meters to tens of meters of pipe per hour. This capacity, compared to the production efficiency of ordinary polyethylene pipes, cannot meet the large market demand for standard-sized pipes.

[0106] Alternatively, compression molding can be used: a certain amount of UHMWPE powder or preformed blank is placed into the mold cavity. After the mold is closed, it is held at a certain temperature and pressure for a period of time, allowing the material to melt and flow within the mold and fill the cavity, forming a pipe shape. Afterward, the mold cools, the pipe solidifies, and the mold is opened to remove the formed pipe. However, this compression molding method has relatively low production efficiency and is usually intermittent. Each molding process requires multiple steps, including loading, mold closing, heating and pressurizing, cooling and demolding, making the entire process time-consuming.

[0107] Alternatively, a winding process can be used. For example, UHMWPE fibers or strips can be impregnated with resin and then wound onto a mandrel according to a specific pattern. During the winding process, parameters such as the winding angle and the number of layers are controlled to meet the performance requirements of the pipe. After winding, the resin is cured by heating or other methods to form the pipe. Finally, the mandrel is removed to obtain the UHMWPE wound pipe. However, winding requires the preparation of fibers or strips and impregnation treatment, which is costly and increases production steps and time costs.

[0108] In some embodiments, the present invention combines the advantages and disadvantages of the above molding methods, and develops an original, efficient, high-quality, and low-cost molding method by introducing an auxiliary molding layer. Specifically, the pipe wall further includes an auxiliary molding layer located between the outer surface layer of the pipe wall and the low-friction layer. The material of the auxiliary molding layer includes a high molecular weight polymer and additives. For example, the auxiliary molding layer material composition is food-grade HDPE, or 100 parts HDPE and 2.1 parts carbon black.

[0109] The primary function of the auxiliary forming layer is to assist in the forming of the low-friction layer. Specifically, the low-friction layer powder is attached to the inner surface of the tubular auxiliary forming layer. The tubular auxiliary forming layer applies traction (dragging force) or provides support to the low-friction layer powder, rather than applying extrusion force to the molten low-friction layer, effectively reducing the forming difficulties caused by the ultra-high viscosity of the molten low-friction layer material. Specifically, the low-friction layer powder layer can be formed on the auxiliary forming layer through co-extrusion, and then the composite material can be formed by heating. Alternatively, the low-friction layer powder can be first formed on a strip-shaped auxiliary forming layer, then heated to form a composite pipe strip, and finally formed into a multi-layer composite pipe through a winding process. These methods effectively overcome the shortcomings of existing extrusion molding, compression molding, and winding methods, and comprehensively utilize the advantages of various forming methods to meet the market demand for high-performance and low-cost pipes.

[0110] Molten polymers are easily mixed with other additives, such as pigments, fillers, and flame retardants. These additives can improve the properties of the material, such as enhancing mechanical properties, improving flame retardancy, or imparting specific colors. Furthermore, molten polymers facilitate composite processing, such as blending different polymers together to form composite materials with novel properties.

[0111] For example, additives may include polyethylene, linear low-density polyethylene, antioxidants, etc. Linear low-density polyethylene (LLDPE) has advantages such as good toughness and resistance to environmental stress cracking, and is widely used in pipe manufacturing. Its molding methods are diverse, and the manufacturing efficiency varies depending on the equipment, process parameters, and product specifications.

[0112] Fillers can be inorganic or non-metallic minerals, processed into powder materials with specific chemical composition, geometric shape, and surface properties. Fillers (extenders) are the additives used in the largest quantities. For example, fillers such as wood flour, phosphogypsum, clay, or calcium carbonate added during pipe molding not only improve the mechanical properties and increase hardness of the product but also reduce costs. For instance, using graphite, magnetic powder, or mica as fillers can improve the magnetic conductivity and heat resistance of plastics; adding carbon black or silica to plastics can significantly improve the physical properties of the product; adding titanium dioxide to plastics can provide light-blocking and coloring properties. White or colored fillers (such as titanium dioxide, talc, calcium carbonate, barium sulfate, etc.) can be added to composite pipes to improve their optical, physical, and chemical properties.

[0113] It should be noted that the pipe can be round or a special-shaped pipe with special functions. For example, when the pipe is a special-shaped pipe with self-cleaning function, the internal flow channel shape of the pipe in the installed state consists of three parts: a first opening, a second opening, and a connecting structure. Each structure and its connection points are rounded. See [reference needed]. Figures 2 to 32 The shapes of the first and second openings correspond to their projected areas in cross-section, with the area of ​​the first opening being larger than that of the second opening. Pipes with the aforementioned internal flow channel characteristics include: two-layer pipe walls, three-layer pipe walls, and four-layer pipe walls, etc.

[0114] For two-layer pipes, as shown in Table 2, the auxiliary molding layer with a wall thickness of E3 is composed of polymer materials and their modified materials, such as one or a combination of high-density polyethylene (HDPE), polypropylene (PP), and polyvinyl chloride (PVC); the low-friction layer with a wall thickness of E4 is composed of ultra-high molecular weight polyethylene and its modified materials, such as direct molding of ultra-high molecular weight polyethylene powder; the molding process is assisted by the auxiliary molding layer; the friction coefficient of the low-friction layer of the ultra-high molecular weight polyethylene layer after molding is controlled to be 0.13.

[0115] For example, the auxiliary molding layer with a wall thickness of E3 is composed of polymer materials and their modified materials, such as one or a combination of high-density polyethylene (HDPE), polypropylene (PP), and polyvinyl chloride (PVC); for example, the auxiliary molding layer material is polypropylene (PP), which is plasticized by an extruder during molding, and the extrudate melt temperature is 290°C, used to melt and adhere ultra-high molecular weight polyethylene powder in order to form a low-friction layer.

[0116] The material with a low-friction layer wall thickness of E4 is composed of ultra-high molecular weight polyethylene (UHMWPE) and its modified materials. For example, UHMWPE powder can be directly formed through an auxiliary forming layer, or it can be spirally wound after being assisted by an auxiliary forming layer and pressed. When microwave heating is used during the pressing process, the material composition is: 100 parts UHMWPE powder, 5 parts carbon black, 1 part water, and 1 part silicone oil. Through the matrix properties of UHMWPE, the reinforcement and functionalization of carbon black, the lubrication of silicone oil, and the processing assistance of water, multiple optimizations in mechanical properties, processing performance, and functional characteristics are achieved, making it suitable for the field of high-performance engineering plastics.

[0117] Table 2

[0118]

[0119] See Figure 2 The diagram shown illustrates the deformation of an egg-shaped pipe under gravity. The force acting on the pipe is represented by F, which includes the force exerted by the sealing soil and its own weight. Figure 2 The pipe shown is an irregularly shaped pipe. Under the action of force F, the irregularly shaped pipe deforms, such as the arc on the side of the pipe closer to the Earth's center becoming larger. This may weaken or eliminate the special properties of the irregularly shaped pipe.

[0120] See Figure 3 The diagram shows a partial schematic of a cross-section of another type of multilayer composite pipe. In this embodiment, in addition to the outer wall layer and the low-friction layer, the multilayer composite pipe may also include a wide-gauge polymer layer located between the outer wall layer and the low-friction layer. This wide-gauge polymer layer includes a polymer, a foaming agent, and a filler. This wide-gauge polymer layer can control the self-weight creep deformation rate during use and improve the sag problem during molding. For example, the polymer includes, but is not limited to, one or a mixture of polyolefins, polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyethylene terephthalate (PET), etc.

[0121] In some embodiments, an auxiliary molding layer is located between the wide-gauge polymer layer and the low-friction layer. The material composition of the auxiliary molding layer includes polyethylene, linear low-density polyethylene, antioxidants, and BN500. Table 3 shows some structural examples of three-layer pipes.

[0122] Wide-gauge polymer layers are extruded during the foaming process to form an auxiliary molding layer and a low-friction layer, thereby forming a composite pipe in a mold.

[0123] In one embodiment, for a three-layer pipe, as shown in Table 3, the outermost layer with a wall thickness of E1 is composed of a polymer material and its modified materials, such as one or a combination of high-density polyethylene (HDPE), polypropylene (PP), and polyvinyl chloride (PVC); the auxiliary molding layer with a wall thickness of E3 is composed of a polymer material and its modified materials, such as one or a combination of high-density polyethylene (HDPE), polypropylene (PP), and polyvinyl chloride (PVC); the low-friction layer with a wall thickness of E4 is composed of ultra-high molecular weight polyethylene and its modified materials, such as direct molding of ultra-high molecular weight polyethylene powder, with the auxiliary molding layer assisting in the molding process; the friction coefficient of the molded ultra-high molecular weight polyethylene layer is controlled to be 0.12.

[0124] Table 3

[0125]

[0126]

[0127] The raw materials for the wide-gauge polymer layer can be virgin or recycled materials, such as polymers recycled after industrial or post-consumer use. Furthermore, the use of lower-cost polymers than the aforementioned outer layer, auxiliary molding layer, and low-friction layer is also considered. More additives, including foaming agents and fillers, can be added during the molding process. The raw materials for the wide-gauge polymer layer are high molecular weight homopolymers or copolymers such as polypropylene, low-density polyethylene, linear low-density polyethylene, and / or high-density high-molecular-weight polyethylene. By adding various additives to these polymers, such as UV inhibitors, carbon black, and processing aids, desired effects on finished product quality and / or manufacturing efficiency can be achieved.

[0128] The advantages of foaming solutions include not only reduced raw material costs and pipe weight, but also the desired physical and chemical properties of the foam layer itself, such as vibration absorption, noise reduction, and thermal insulation. Using the aforementioned foam layer can also produce pipes with thicker profiles, alleviating users' concerns about strength.

[0129] For example, the material composition of the wide-gauge polymer layer includes: polyethylene or polypropylene, as well as a foaming agent and / or filler, wherein the polymer includes at least one of virgin polyethylene, recycled polyethylene, virgin polypropylene or recycled polypropylene; and / or, the ratio of the thickness of the wide-gauge polymer layer to the wall thickness of the composite pipe is greater than 50%, such as 50%, 60%, 70%, 80%, 90%, etc.

[0130] In one specific embodiment, see Figure 3The composite structure wall has a four-layer composite structure with cross-sections of A1-B-A2-C. Among them, layers A1 and A2 are polymer and modified polymer material layers, layer B is a polymer and modified foaming material layer, and layer C is a modified ultra-high molecular weight polyethylene material layer.

[0131] The C-layer is a modified ultra-high molecular weight polyethylene layer. The friction coefficient of the modified C-layer is between 0.01 and 0.2, preferably between 0.03 and 0.15. The modified powder composition includes ultra-high molecular weight powders with a molecular weight of 1 million, 2 million, 3 million, or 4 million or more, antioxidants, etc. Table 4 shows some structural examples of four-layer pipe materials.

[0132] Table 4

[0133]

[0134]

[0135] In one embodiment, for a four-layer pipe, as shown in Table 4, the outermost layer with a wall thickness of E1 is composed of a polymer material and its modified forms, such as one or a combination of high-density polyethylene (HDPE), polypropylene (PP), and polyvinyl chloride (PVC); the wide-gauge polymer layer with a wall thickness of E2 is composed of a polymer and its modified foaming material, such as one or a combination of high-density polyethylene (HDPE), polypropylene (PP), and polyvinyl chloride (PVC), for example, using 100 parts HDPE, 10 parts calcium powder, and 5 parts foaming agent, extruded and foamed, with a material density of 0.95 g / cm³ after foaming. 3 The average pore diameter is 90 micrometers, and the pore density is 1.9 × 10⁻⁶. 7 pcs / cm 3 The auxiliary molding layer with a wall thickness of E3 is composed of polymer materials and their modified materials, such as high-density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC) or a combination thereof; the low friction layer with a wall thickness of E4 is composed of ultra-high molecular weight polyethylene and its modified materials, such as direct molding of ultra-high molecular weight polyethylene powder, with the auxiliary molding layer assisting in the molding process; the friction coefficient of the ultra-high molecular weight polyethylene layer after molding is controlled to be 0.14.

[0136] In some embodiments, test results of resistance to gravity deformation of single-walled and four-walled pipes are shown as examples.

[0137] The wide-specification polymer layer uses micro-foamed material, which effectively improves the pipe's resistance to gravity deformation. The resistance to gravity deformation of single-layer solid-wall pipes and four-layer composite-wall pipes were compared. As shown in Table 5, the wall thickness E1 of the single-layer pipe is made of high-density polyethylene (HDPE); the four-layer pipe with a wide-specification polymer layer has an outer layer wall thickness of E1 made of high-density polyethylene (HDPE); the wide-specification polymer layer wall thickness E2 is made of high-density polyethylene (HDPE) foam material, such as 100 parts HDPE, 10 parts calcium powder, and 5 parts foaming agent, extruded and foamed, with a post-foaming material density of 0.95 g / cm³. 3 The average pore diameter is 90 micrometers, and the pore density is 1.9 × 10⁻⁶. 7 pcs / cm 3 The auxiliary molding layer with a wall thickness of E3 is made of high-density polyethylene (HDPE); the low-friction layer with a wall thickness of E4 is made of ultra-high molecular weight polyethylene. Table 5 shows the results of gravity deformation resistance of the pipes using the above structure and materials.

[0138] Table 5

[0139]

[0140] The above comparison shows that when single-layer pipes and four-layer composite pipes have the same wall thickness, the four-layer composite pipes have stronger resistance to gravity deformation.

[0141] Figure 4 A schematic cross-sectional view of a multi-layer composite pipe is shown. The pipe is an irregularly shaped composite pipe, with a greater curvature on the side closer to the Earth's center than on the side farther from the Earth's center. This results in a first cross-sectional area larger than a second cross-sectional area. The first cross-sectional area represents the area of ​​the half-section of the composite pipe on the side farther from the Earth's center after installation, and the second cross-sectional area represents the area of ​​the half-section of the composite pipe on the side closer to the Earth's center after installation. The liquid flow velocity within the first cross-sectional area is lower than the liquid flow velocity within the second cross-sectional area; that is, the liquid flow velocity at the bottom of the composite pipe is higher than the liquid flow velocity in the middle of the pipe. This design, through a special mechanical structure, accelerates the liquid flow at the bottom of the pipe, helping to flush away contaminants deposited and attached to the bottom of the pipe.

[0142] In one specific embodiment, the pipe includes at least one layer of pipe wall, and the cross-section of the layer of pipe wall of the composite pipe includes: a first opening structure, which is located on the side of the composite pipe away from the Earth's center when the composite pipe is laid; a second opening structure, which is located on the side of the composite pipe closer to the Earth's center when the composite pipe is laid; and a connecting structure, which connects the first opening structure to the second opening structure and forms a closed shape; wherein, the first projected area is larger than the second projected area, the first projected area is the projected area of ​​the closed region of the first opening structure on the cross-section, and the second projected area is the projected area of ​​the closed region of the second opening on the cross-section.

[0143] In some embodiments, the first opening structure is a horizontally symmetrical structure; the second opening structure is a horizontally symmetrical structure; the connecting structure includes two horizontally symmetrical and separately arranged sub-connecting structures, the two ends of each sub-connecting structure being connected to one end of the first opening structure and one end of the second opening structure, respectively.

[0144] The first opening structure can be any one or a combination of a circular arc structure, an elliptical arc structure, and a polygonal opening structure; the second opening structure can be any one or a combination of a circular arc structure, an elliptical arc structure, and a polygonal opening structure. The opening size of the second opening structure is smaller than the opening size of the first opening structure. For example, the edges of the polygonal opening structure are connected with rounded corners.

[0145] According to fluid mechanics, the liquid velocity near the bottom of a pipe is greater than that in other parts of the pipe, creating a flushing effect on the bottom of the pipe and achieving a self-cleaning effect. This effectively reduces the risk of pipe blockage.

[0146] However, see Figure 2 The applicant already has egg-shaped pipes with outer arc transitions on both sides. This will cause the pipes to deform outwards and gradually become rounded under external pressure (covered soil) or their own weight. See [link / reference]. Figure 2 As shown, the radius of the small arc flow channel at the bottom of the inner flow channel will increase, gradually losing its self-cleaning function (inner flow channel structure). Simultaneously, the pipe's self-cleaning ability is low at low flow rates, resulting in slow flow velocity in the middle section. Large-diameter pipes are prone to deformation under their own weight during use, causing leaks at pipe connections. The weight-induced out-of-roundness of PE solid-wall pipes leads to connection difficulties and leaks.

[0147] In summary, existing solid-wall PE pipes have the following problems: PE solid-wall pipes lose roundness due to their own weight, leading to connection failures and leaks, especially large-diameter pipes which are prone to deformation under their own weight during use, causing leaks at pipe connections. Simultaneously, existing water supply and drainage pipes have low wear resistance, are prone to scale buildup and microbial adhesion, and lack self-cleaning capabilities. New ultra-high molecular weight polyethylene (UHMWPE) materials can solve the problems of wear resistance, scale buildup, and microbial adhesion; however, this material is difficult to mold, has low extrusion efficiency, and is difficult to form into large-diameter pipes. Furthermore, many techniques use blending modification to adjust the processability of UHMWPE and achieve faster extrusion; however, blending modification significantly alters the material's properties, reducing its wear resistance and scale resistance.

[0148] To address the above issues, the structure of this irregularly shaped pipe was innovated. See [link / reference] Figures 5 to 20 The diagram shows cross-sectional schematics of various multi-layer composite pipes.

[0149] In one embodiment, the connection structure includes a first sub-connection structure and a second sub-connection structure. The first and second sub-connection structures are either straight lines or curved lines that bend towards each other. This ensures that, after installation, at least one side of the composite pipe retains its shape or deforms towards the axis of the composite pipe.

[0150] To further accelerate the liquid flow rate in areas of the pipe where sedimentation is likely to occur, acceleration structures can be installed in the corresponding areas of the pipe.

[0151] Specifically, the second opening structure includes at least one concave shape facing the first opening, with liquid acceleration flow structures formed on both sides of the concave shape; and / or, the second opening structure includes at least one convex shape in a direction away from the first opening, the convex shape forming a liquid flow acceleration structure.

[0152] In some embodiments, the multi-channel design of the bottom arc of the pipe solves the self-cleaning function at low flow rates and prevents long branches from sinking to the bottom. The multi-channel design at the bottom can suspend long branches on the arc protrusions, preventing them from sinking. The multi-channel design at the bottom arc can form a flat pipe bottom, eliminating the need for an additional anti-tipping support base. It also increases the flow velocity in the middle, facilitating the self-cleaning of floating objects such as large branches.

[0153] In some embodiments, the top hexagonal design addresses the issue of load-bearing capacity at the top of the pipe and improves the pipe's resistance to soil cover.

[0154] In some embodiments, controllable circumferential stress can be constructed in a wide-specification polymer layer through microporous foaming, making the pipe resistant to internal and external pressure (with the inner and outer layers under pre-compression), improving strength, applying circumferential stress to the entire pipe, solving the problem of deformation due to the self-weight of ultra-large diameter pipes, and solving the connection difficulties and leakage problems caused by the self-weight out-of-roundness of existing PE solid-wall pipes.

[0155] In some embodiments, smooth inner and outer surfaces are achieved by performing microporous foaming and internal and external sizing in a wide-gauge polymer layer during the molding process. At the same time, a modified ultra-high molecular weight polyethylene layer is used as a low friction coefficient layer to reduce the friction coefficient of the inner wall of the pipe, thereby achieving wear resistance and improving the hydraulic capacity of the pipe.

[0156] See Figures 5 to 20 The image shown is a schematic diagram of the cross-section of various multi-layer composite pipes. Figures 21 to 29 The diagram shows a three-dimensional cross-sectional view of various multi-layer composite pipes.

[0157] For example, Figure 5 The sidewalls of the pipe cross-section are straight, rather than curved outwards.

[0158] Figure 6 The bottom of the pipe cross-section has a raised shape, and the two grooves on the side of the raised shape form a liquid flow acceleration structure.

[0159] Figure 7 The bottom of the pipe cross-section has two raised shapes, and the three grooves on the side of the raised shapes form a liquid flow acceleration structure.

[0160] Figure 8 The sidewalls of the pipe cross-section are curved towards the pipe axis. When the pipe is deformed under pressure, the arc at the bottom of the pipe will not increase, and the liquid flow rate will not decrease.

[0161] Figure 9 The sidewall of the pipe cross-section is a curve that bends toward the pipe axis, and the bottom has a raised shape. Two grooves on the side of the raised shape form a liquid flow acceleration structure.

[0162] Figure 10 The sidewall of the pipe cross-section is a curve that bends toward the pipe axis, and the bottom has two protruding shapes. The three grooves on the side of the protruding shapes form a liquid flow acceleration structure.

[0163] Figure 11 The top of the pipe cross-section is a polygonal opening, with adjacent sides connected by arcs, which effectively improves the top load-bearing capacity, and the side walls are straight.

[0164] Figure 12The top of the pipe cross-section is a polygonal opening with circular arcs connecting adjacent sides. The sidewalls are straight, and the bottom has a raised shape. Two grooves on the side of the raised shape form a liquid flow acceleration structure.

[0165] Figure 13 The top of the pipe cross-section is a polygonal opening with circular arcs connecting adjacent sides. The sidewalls are straight, and the bottom has a raised shape. Two grooves on the side of the raised shape form a liquid flow acceleration structure.

[0166] Figure 14 The top of the pipe cross-section is a polygonal opening, with adjacent sides connected by arcs. The sidewalls are curves that bend towards the pipe axis. When the pipe deforms under pressure, the arc at the bottom of the pipe will not increase, and the liquid flow rate will not decrease.

[0167] Figure 15 The top of the pipe cross-section is a polygonal opening with circular arcs connecting adjacent sides. The sidewalls are curved towards the pipe axis, and the bottom has a raised shape with two grooves on the side of the raised shape forming a liquid flow acceleration structure.

[0168] Figure 16 The top of the pipe cross-section is a polygonal opening with circular arcs connecting adjacent sides. The sidewalls are curved towards the pipe axis, and the bottom has two protruding shapes. The three grooves on the sides of the two protruding shapes form a liquid flow acceleration structure.

[0169] Figure 17 The top of the pipe cross-section includes an irregular shape formed by the sequential connection of a first straight edge, a circular arc, and a second straight edge, with the connection point being a circular arc. The sidewalls are straight edges, and the cross-sectional area at the bottom is smaller than that at the top, creating an effect that accelerates liquid flow at the bottom.

[0170] Figure 18 The top of the pipe cross-section includes an irregular shape formed by the sequential connection of a first straight edge, a circular arc, and a second straight edge, with the connection point being a circular arc. The sidewalls are straight edges, and the bottom has a raised shape. Two grooves on the side of the raised shape form a liquid flow acceleration structure.

[0171] Figure 19 The top of the pipe cross-section includes an irregular shape formed by the sequential connection of a first straight edge, a circular arc, and a second straight edge, with the connection point being a circular arc. The sidewalls are curves that bend towards the pipe axis. The cross-sectional area at the bottom is smaller than that at the top, creating an effect that accelerates liquid flow at the bottom.

[0172] Figure 20The top of the pipe cross-section includes an irregular shape formed by the sequential connection of a first straight edge, an arc, and a second straight edge, with the connection point being an arc. The sidewall is a curve that bends toward the pipe axis, and the bottom has a raised shape. Two grooves on the side of the raised shape form a liquid flow acceleration structure.

[0173] It should be noted that the inner and outer walls of the pipe can be conformal or non-conformal, such as... Figures 5 to 20 The inner and outer walls of the pipe shown are conformal. In other embodiments, the inner and outer walls of the pipe may not be conformal, such as the outer wall being flatter than the inner wall, to facilitate the pipe standing upright on the mounting surface. Furthermore, increasing the thickness of the pipe wall at a certain point can effectively improve the mechanical strength of the pipe wall.

[0174] In other embodiments, to improve the ease of pipe installation and installation stability, a support structure can be provided on the side of the pipe closest to the Earth's center. Figures 30 to 32 This diagram shows a three-dimensional cross-sectional view of a multi-layer composite pipe with a supporting structure. The support leg structure can be integrally formed, welded on, or a separate component; no limitation is made here.

[0175] For example, in a composite structure wall pipe with an integrated base, the integrated base forming process may include: after the preform pipe is extruded and shaped, it is inserted into a base forming die, and the integrated base is laminated at the bottom. By adjusting the extrusion process, the integrated base can be laminated onto the bottom of the preform pipe as a continuous flat structure or intermittently extruded and laminated into a discontinuously distributed integrated base. The discontinuously distributed integrated base facilitates the subsequent connection of the pipe.

[0176] In one specific embodiment, the cross-section of the flow channel structure in the radial section of the pipe is a large arc in the upper part and a small arc in the lower part. The transition area between the upper and lower arcs is a diagonal line or an inner arc. The position where the diagonal line or inner arc intersects with the large arc in the upper part and the small arc in the lower part is set as a rounded transition, and the rounded corner is greater than or equal to R 0.01mm. At the same time, there is at least one small arc in the lower part of the pipe, forming different lower flow channel structures.

[0177] The upper part of the flow channel structure in the radial cross section of the pipe has a polygonal opening structure, and the lower part has a small arc. The transition area between the upper and lower structures is a diagonal line or an inner arc. The intersection of the diagonal line or inner arc with the upper polygonal opening structure and the lower small arc is set as a rounded transition, with a rounded corner greater than or equal to R0.01mm. The upper polygonal opening structure consists of three sides, with two sides symmetrically distributed on both sides of a horizontal side in the middle. The intersection of the three sides is set as a rounded transition, with a rounded corner greater than or equal to R0.01mm. At the same time, the lower part of the pipe has at least one small arc, forming different lower flow channel structures.

[0178] The cross-section of the inner flow channel structure in the radial section of the pipe consists of two sides symmetrically distributed on both sides of a large central arc in the upper part, and a small arc in the lower part. The transition area between the upper and lower structures is a diagonal line or an inner arc. The intersection of the diagonal line or inner arc with the two sides of the upper part and the small arc of the lower part is set as a rounded transition, with a rounded corner greater than or equal to R0.01mm. At the same time, there is at least one small arc in the lower part of the pipe, forming different lower flow channel structures.

[0179] When subjected to the force of backfill soil, the inner arc surfaces or slopes on both sides of the pipe's radial cross-section deform inward, reducing the radius of the lower section's fillet and gradually enhancing its self-cleaning properties. Simultaneously, the upper section's multi-sided opening structure provides the pipe with high strength, enabling it to withstand greater backfill soil forces. The middle section of the pipe features an inner arc transition, increasing the flow velocity and accelerating the removal of floating debris such as large branches. The multi-arc protrusions at the bottom of the pipe can suspend long, sunken branches, preventing them from sinking. Furthermore, the smaller distribution of the multi-arc protrusions at the bottom allows the pipe to achieve self-cleaning performance at lower flow rates.

[0180] When the pipe is subjected to the force of the backfill soil, the inner arc surfaces or slopes on both sides of the flow channel deform inward, the radius of the lower part decreases, and the self-cleaning ability gradually increases. Simultaneously, the upper part has a multi-sided opening structure, giving the pipe high strength and enabling it to withstand greater backfill force. The flow channel in the middle of the pipe has an inner arc transition, which increases the flow velocity in the middle, accelerating the removal of floating debris such as large branches. The multi-arc protrusion design in the lower part of the pipe can suspend long branches on the arc protrusions, preventing them from sinking to the bottom.

[0181] Another aspect of the present invention provides a method for forming multilayer composite pipes.

[0182] See Figure 1 The forming method of multi-layer composite pipes is illustrated by taking a two-layer composite pipe as an example. See [link to documentation]. Figure 33 The forming method of the multi-layer composite pipe includes operations S110 to S130.

[0183] In operation S110, a composite preform is formed, the composite preform comprising a molten auxiliary forming layer and a low-friction layer powder adhered to at least one side of the molten auxiliary forming layer.

[0184] Among them, the molding methods of composite preforms include co-extrusion and hot melt molding.

[0185] In operation S120, the low-friction layer powder is heated to form a molten low-friction layer on at least one side of the molten auxiliary forming layer.

[0186] In operation S130, the molten auxiliary forming layer and the molten low-friction layer are formed into the composite pipe.

[0187] The friction coefficient M of the low-friction layer is less than that of the outer surface layer of the pipe wall. The material of the low-friction layer includes an ultra-high molecular weight polymer and an antioxidant. The low-friction layer can be an ultra-high molecular weight polymer layer, such as an ultra-high molecular weight polyethylene layer. For details regarding the low-friction layer and the auxiliary molding layer, please refer to the relevant content in this application.

[0188] The following example uses co-extrusion molding as an illustration.

[0189] For example, forming a composite preform may include: conveying modified low-friction layer powder into a first composite molding die, wherein the material of the low-friction layer powder includes: ultra-high molecular weight polyethylene and an antioxidant; and covering the molten auxiliary molding layer on the modified low-friction layer powder in the first composite molding die to form the composite preform.

[0190] Heating the low-friction layer powder may include heating the modified low-friction layer powder through the core mold in the first composite molding die and the molten auxiliary molding layer.

[0191] The above methods enable the co-extrusion molding of composite preforms.

[0192] The following example illustrates the hot-melt pressing method.

[0193] Forming a composite preform may include the following operations: extruding the auxiliary molding layer; adding modified low-friction layer powder to the uncooled and uncured auxiliary molding layer to obtain an initial composite preform; and pressing the initial composite preform to form the composite preform.

[0194] Accordingly, heating the low-friction layer powder may include: contact heating the side of the auxiliary forming layer away from the low-friction layer powder, and contact and / or non-contact heating the side of the low-friction layer powder of the auxiliary forming layer.

[0195] The above methods enable the formation of composite blanks through pressing and hot melting.

[0196] In addition, the pressing hot-melt method helps to precisely control the thickness of the low-friction layer and can produce a thicker low-friction layer.

[0197] Specifically, forming the composite preform may further include: after heating the low-friction layer powder, repeating the following operations at least once: adding modified low-friction layer powder to one side of the low-friction layer powder in the composite preform; pressing the composite preform; and heating the low-friction layer powder.

[0198] The above method allows for the preparation of thicker low-friction layers by repeatedly stacking low-friction powder.

[0199] Furthermore, the molding method of the present invention can also be used to mold composite pipes with more layers. (Reference) Figure 3 As shown, taking a composite structure with a wall cross section of A1-B-A2-C as an example, the forming method of a four-layer composite pipe is given.

[0200] In some embodiments, see Figure 34 The above molding method may further include operation S240, in which, after heating the low-friction layer powder, a molten, wide-gauge polymer layer is formed on the side of the composite preform away from the low-friction layer. The wide-gauge polymer layer can effectively reduce raw material costs and enhance the mechanical strength of the pipe, achieving functions such as heat insulation, vibration absorption, aging resistance, and prestressing.

[0201] For example, the wide-gauge polymer layer has a foamed structure. Accordingly, the molding method further includes: after forming a molten outer wall layer on the side of the molten wide-gauge polymer layer away from the low-friction layer, the wide-gauge polymer layer is extruded during the foaming process to form the outer wall layer and the auxiliary molding layer.

[0202] In some embodiments, see Figure 34 The above molding method may further include operation S250, after forming the wide-gauge polymer layer, forming a molten tube wall outer surface layer on the side of the molten wide-gauge polymer layer away from the low-friction layer.

[0203] In some embodiments, the composite pipe can be formed into various shapes. For example, the cross-section of the pipe can be circular, elliptical, seed-shaped, fan-shaped, and many other shapes, see [link to documentation]. Figures 5 to 20 .

[0204] In some embodiments, by designing the cross-sectional shape of the pipe, it is possible to achieve an accelerated liquid flow effect in a specific area, and by combining it with a low-friction layer with a low coefficient of friction, a self-cleaning effect of the pipe can be achieved.

[0205] For example, composite pipes can be formed by co-extrusion. Forming the molten auxiliary forming layer and the molten low-friction layer into the composite pipe can include: extruding the molten auxiliary forming layer and the molten low-friction layer through a pipe forming die to obtain the composite pipe; wherein the cross-section of the pipe forming die is circular; or the first cross-sectional area of ​​the pipe forming die is greater than the second cross-sectional area, the first cross-sectional area being the area of ​​the half-section of the composite pipe on the side furthest from the Earth's center after laying, and the second cross-sectional area being the area of ​​the half-section of the composite pipe on the side closest to the Earth's center after laying.

[0206] For example, composite pipes can be formed by winding. Forming the molten auxiliary forming layer and the molten low-friction layer into the composite pipe may include: extruding the molten auxiliary forming layer and the molten low-friction layer through a strip forming die to obtain a composite strip; winding the composite strip to obtain a composite strip spiral structure; spinning (heating) the composite strip spiral structure to fuse the stacked portions of the composite strip spiral structure to obtain a composite columnar material; and extruding the composite columnar material to obtain the composite pipe.

[0207] Specifically, the composite tape spiral structure obtained by winding the composite tape may include: winding the composite tape onto a column with a specific cross-sectional shape; wherein the specific cross-sectional shape is circular; or the first cross-sectional area of ​​the specific cross-sectional shape is greater than the second cross-sectional area, the first cross-sectional area being the area of ​​the half-section of the composite pipe away from the Earth's center in the laid state, and the second cross-sectional area being the area of ​​the half-section of the composite pipe closer to the Earth's center in the laid state.

[0208] In one embodiment, the A2-C composite structure is formed by co-extrusion. In the co-extrusion equipment, one outlet is a molten auxiliary forming layer, and the other outlet is a low-friction layer powder. The viscosity of the molten auxiliary forming layer is much lower than that of the molten low-friction layer, allowing for faster extrusion. The extruded auxiliary forming layer and / or the powder conveyor simultaneously transport the low-friction layer powder from the outlet to the heating zone. By heating the low-friction layer powder, it is brought to a molten state, forming the composite structure. Subsequently, composite structures with more layers can be formed through co-extrusion, and the composite structure can be formed into a pipe of a specific shape using a forming device.

[0209] In one embodiment, the low-friction layer is formed by sintering low-friction material powder attached to the side of the auxiliary forming layer near the pipe axis. The low-friction material powder and the auxiliary forming layer in a molten state are co-extruded. The molecular weight of the polymer is greater than or equal to 1 million, such as 1.1 million, 3 million, or 4 million. The thickness of the low-friction layer is less than 30 mm, and 0.03 ≤ M ≤ 0.15, where M is the friction coefficient of the low-friction layer. In this embodiment, a composite pipe with an auxiliary forming layer and a low-friction coefficient layer can be formed by co-extrusion. By increasing the number of co-extrusion cycles, a composite pipe with more layers can also be formed. This embodiment can form the pipe without processes such as winding.

[0210] In another embodiment, the low-friction layer is formed by sintering low-friction material powder attached to the side of the auxiliary forming layer near the pipe axis. The low-friction material powder and the auxiliary forming layer are formed by pressing and sintering. The molecular weight of the polymer is greater than or equal to 1 million, such as 1.1 million, 3 million, or 4 million. The thickness of the low-friction layer is less than 30 mm, and 0.03 ≤ M ≤ 0.15. In this embodiment, a strip-shaped composite material is first manufactured. Since the low-friction layer material can be laid multiple times on the auxiliary forming layer, the thickness of the low-friction layer can be easily and precisely controlled, and a thicker low-friction layer can be easily manufactured. Then, the pipe is manufactured using a winding pipe forming process. This method is more suitable for mass production and assembly line operations.

[0211] The present invention can manufacture composite pipes using the two different molding methods described above.

[0212] Figure 35 A composite pipe forming apparatus is shown. See also Figure 35 The composite pipe forming apparatus may include: a composite blank forming system 1 and a composite pipe forming system 2.

[0213] The composite preform forming system 1 (e.g., a first composite die) is used to form a molten low-friction layer on at least one side of the molten auxiliary forming layer. The composite pipe forming system 2 (e.g., a second composite die) is used to form the molten auxiliary forming layer and the molten low-friction layer into a composite pipe. Specifically, the composite preform forming system 1 realizes the composite of the C layer powder and the auxiliary forming layer (A2 layer) material, and the composite pipe forming system 2 realizes the composite of the outer surface layer (A1 layer), the wide-gauge polymer layer (B layer), and the A2-C layer output by the composite preform forming system 1.

[0214] The composite blank forming system 1 includes a heating device for heating low-friction layer powder attached to at least one side of the molten auxiliary forming layer to form a molten low-friction layer. The friction coefficient of the low-friction layer is less than that of the outer surface layer of the composite pipe.

[0215] In some embodiments, the composite preform forming system 1 may include: a preform forming apparatus and at least one set of preform forming apparatuses.

[0216] The blank forming device is used to form a molten auxiliary molding layer. Each of the at least one set of blank forming devices includes: a low-friction layer powder feeding device for forming ultra-high molecular weight polyethylene powder, such as C-layer powder, on at least one side of the molten auxiliary molding layer. Correspondingly, a heating device is used to heat the low-friction layer powder adhering to at least one side of the molten auxiliary molding layer to form a molten low-friction layer.

[0217] See Figures 36 to 39 The composite pipe forming device may include the following components: a screw conveyor 1-01, a spiral protrusion 1-02, a straight section without a spiral protrusion 1-03, a die core rod 1-04, a first die support 1-05, a transmission wheel 1-06, a drive device 1-07, a first outer mold body 1-08, a first inner mold body 1-09, a frame base 1-10, an A2 layer material channel 1-11, a C layer powder channel 1-12, an A2-C layer material channel 1-13, a first extruder 1-14, and a C layer powder feeder 1-15. Furthermore, the figure also shows an A2 layer preform 1-16, a C layer powder 1-17, and an A2-C layer composite preform 1-18 to facilitate understanding of the technical solution of the present invention.

[0218] The composite preform forming system 1 adds low-friction layer powder to the cavity through the C-layer powder feeder 1-15, forming a cavity between the first outer mold body 1-08 and the first inner mold body 1-09. This cavity serves as the A2 layer material channel 1-11. Figure 37 and Figure 38 As shown. A chamber is formed between the first inner mold body 1-09 and the screw conveyor 1-01. This chamber serves as the C-layer powder channel 1-12. The C-layer powder 1-17 connects with the molten auxiliary forming layer at the channel intersection to form an A2-C layer composite material blank. This channel intersection is the junction of the C-layer powder channel 1-12 and the A2 layer material channel 1-11. The A2-C layer composite material blank moves towards the output port of the composite material forming system 1 via the A2-C layer material channel 1-13.

[0219] See Figure 39 The screw conveyor includes a drive unit and a screw component, the outer surface of which includes a non-smooth section. The surface of the screw conveyor has helical ridges. When the screw conveyor rotates, the helical ridges apply an axial pushing force to the low-friction layer powder laid on its surface, causing the low-friction layer powder to move towards the outlet synchronously or nearly synchronously with the molten auxiliary forming layer.

[0220] In one embodiment, the composite preform forming system 1 mainly consists of a modified ultra-high molecular weight polyethylene powder conveying device and an extrusion device for the A2 layer preform. The powder conveying device comprises a screw conveyor and its drive device installed within the composite preform forming system 1. The screw conveyor is looped around the die core rod, and the C layer powder is evenly spread on the inner wall of the A2 layer preform through the screw conveyor, while the A2 layer preform carries away the C layer powder. The screw conveyor is a temperature-controllable annular cylinder with spiral ridges distributed along a certain distance from the tail to the head on the outer cylindrical surface. The entire annular cylinder is looped around the die core rod and rotatably connected to the machine frame base through the core rod and the first die support. That is, the screw conveyor is axially limited and rotates around the core rod, feeding the C layer powder into the interior of the composite preform forming system 1. A drive wheel is fixed to the tail of the screw conveyor (also called a screw feeder) between the tail of the screw conveyor and the die support. The drive wheel is matched with an independent drive device to achieve rotational transmission. When the straight section without spiral protrusions at the head of the screw conveyor rotates, it spins and compresses the A2-C layer composite strip, simultaneously melting the C layer powder. This melts the A2-C layer composite preform into an A2-C layer composite annular cylindrical preform, with the inner layer being the C layer material and the outer layer being the A2 layer material. Simultaneously, the C layer material molecules are circumferentially oriented, further enhancing the inner layer strength. The A2 layer preform extrusion device consists of a first outer mold body and a first inner mold body. The gap between the first outer mold body and the first inner mold body serves as a channel for the molten A2 layer material, and the gap between the first inner mold body and the screw conveyor serves as a conveying channel for the C layer powder.

[0221] See Figure 40 This is a schematic diagram of a composite pipe forming system.

[0222] The composite pipe forming system is used to form an A1-B-A2-C composite structure based on an A2-C layer composite preform. Specifically, an A1-B composite layer is formed on the outer layer of the composite preform through a co-extrusion process. Therefore, the composite pipe forming system 2 can be coaxially arranged with the composite preform forming system 1, such as using the same mandrel.

[0223] See Figure 40 and Figure 41 The composite pipe forming system 2 may include the following components: a second inner mold body 2-01, a third inner mold body 2-02, a second outer mold body 2-03, a third die support 2-04, a die base 2-05, a B2 layer material flow channel 2-06, a second extruder 2-07, an A1 layer material flow channel 2-08, a third extruder 2-09, an A2-C layer material channel 2-10, an A1-B-A2-C layer material flow channel 2-11, a pipe inner flow channel shape 2-12, an inner shaping device 2-13, an outer shaping device 2-14, a screw conveyor 1-01, a die core rod 1-04, and a frame base 1-10.

[0224] The second inner mold body 2-02 and the third inner mold body 2-03 are fitted onto the non-spiral convex section of the screw conveyor 1-01 and are fixed by the third die bracket 2-04.

[0225] Specifically, the composite pipe forming system 2 can be formed by axially connecting a second inner mold body, a third inner mold body, a second outer mold body, a screw conveyor, and a die core rod. The integral composite die is fixed to the frame base through a third die support and a die base. The annular gap between the second and third inner mold bodies forms the B2 layer material flow channel, and the second extruder is connected to the second inner mold body. The annular gap between the third inner mold body and the second outer mold body forms the A1 layer material flow channel, and the third extruder is connected to the second outer mold body. The gap between the second inner mold body and the screw conveyor forms the channel for the A2-C layer material. The annular gap between the non-spiral convex section of the screw conveyor head and the second outer mold body forms the flow channel for the A1-B-A2-C layer material. The annular gap between the die core rod and the second outer mold body gradually transitions to the desired pipe inner flow channel shape, transforming the extruded annular A1-B-A2-C layer material preform into the desired pipe inner flow channel shape preform. The composite structure wall pipe adopts simultaneous internal and external sizing, that is, the internal sizing device is connected to the mandrel and the external sizing device is connected to the frame base respectively.

[0226] In addition, foaming agents can be added to the raw materials of the B layer (i.e., the wide-gauge polymer layer) to foam during the co-extrusion process. This allows the B layer to apply extrusion pressure to the adjacent layers, improving the adhesion between the layers and applying circumferential stress, thereby further improving the mechanical properties of the pipe.

[0227] The following exemplifies the pipe forming process: Modified ultra-high molecular weight polyethylene powder (C-layer powder) is conveyed to the composite preform forming system 1 via a conveying device. Molten A2 layer preform is clad onto the C-layer and carries away the modified ultra-high molecular weight polyethylene powder. Under the high temperature of the mandrel and A2 layer material, the C-layer powder melts and combines with the A2 layer molten material to form a C-A2 layer composite preform. Subsequently, the composite preform enters the composite pipe forming system 2, where molten foaming material (B-layer) is clad onto the A2 layer of the composite preform, forming a three-layer composite preform consisting of C-layer, A2-layer, and B-layer from the inside out, and is pushed forward. Finally... The molten A1 layer is clad onto the blank B layer in the composite pipe forming system 2, ultimately forming a multi-layer composite blank in the composite pipe forming system 2. That is, from the inside out, there are four composite materials: C layer, A2 layer, B layer, and A1 layer. They are extruded together in the direction of die discharge. During the process, the B layer gradually foams and expands, compressing the other three layers. The composite material layers gradually cool and solidify during the circumferential extrusion process, forming circumferential stress. Under the action of the core mold and inner shaping fixture, and the A1 layer under the action of the outer shaping die, a smooth surface is formed. Finally, a smooth straight-walled composite pipe with long-lasting self-cleaning and self-reinforcing properties is formed.

[0228] The above methods effectively improve pipe forming efficiency while reducing the cost of special pipes, and ensure high bonding strength between layers. Furthermore, different layers of composite pipes can possess specific physical and / or chemical properties, such as UV resistance, aging resistance, heat insulation, and vibration absorption, meeting the specific needs of different scenarios. Additionally, the low-friction layer on the inner surface of the pipe effectively reduces the bonding strength between deposits and / or deposits and the pipe wall. Because the pipe can be formed into irregular shapes, it effectively increases the liquid flow velocity in areas prone to deposit and / or deposit formation, significantly improving the flushing effect of liquid on deposits and / or deposits in low-flow-rate scenarios, reducing the risk of pipe blockage, and thus reducing active maintenance and / or repair costs.

[0229] Another aspect of the present invention provides a different composite pipe forming apparatus. See also Figure 42 This is a schematic diagram of another composite pipe forming device.

[0230] In this embodiment, the composite pipe forming apparatus includes a composite blank forming system 41-1 and a composite pipe forming system 41-2.

[0231] The composite preform forming system 41-1 is used to form a molten low-friction layer on at least one side of the molten auxiliary forming layer.

[0232] The composite pipe forming system 41-2 is used to form a composite pipe from a molten auxiliary forming layer and a molten low-friction layer.

[0233] The composite blank forming system 41-1 includes a heating device for heating low-friction layer powder attached to at least one side of the molten auxiliary forming layer to form a molten low-friction layer. The friction coefficient of the low-friction layer is less than that of the outer surface layer of the composite pipe.

[0234] Specifically, the composite pipe forming device mainly includes: an extrusion pressing system for forming A2-C layer composite strip and an extrusion forming system for forming A1-B-A2-C composite structure.

[0235] Figure 43 This diagram illustrates an extrusion pressing system for composite strips. The extrusion pressing system for composite strips is also called a composite preform forming system. This composite preform forming system includes at least one set of preform forming devices for forming a molten auxiliary forming layer.

[0236] Please refer to this as well. Figure 3The extrusion pressing system for forming A2-C layer composite strip mainly includes: an extruder 41 and a die 42 for extruding A2 layer strip; a conveying device 44 for conveying the A2 layer strip 43 extruded from the die; a first set of ultra-high molecular weight polyethylene powder feeders 45; a first set of pressing devices 46; a first heating device 47 for the first compacted strip; a second set of ultra-high molecular weight polyethylene powder feeders 48 for the molten ultra-high molecular weight polyethylene powder; a second set of pressing devices 49; a second heating device 410 for the second compacted strip; and a third pressing device 411 for the third set of pressing devices. The composite material is compacted and gradually cooled. The A2-C layer composite strip 413 is conveyed to a shaping die 412, which is connected to the frame base 414 of the above structure.

[0237] Figure 44 A schematic diagram of an extrusion molding system for a first composite structure is shown. This extrusion molding system includes a co-extrusion section and a cooling and shaping section. The co-extrusion section is used to co-extrude other composite layers, such as the outer wall of a pipe and a wide-gauge polymer layer, onto the outside of the composite preform.

[0238] Each batch of blank forming equipment includes: a low-friction layer powder feeding device and a heating device. Figure 45 A schematic diagram of a powder feeder is shown. The low-friction layer powder feeding device is used to form ultra-high molecular weight polyethylene powder on at least one side of a molten auxiliary forming layer. A heating device is used to heat the low-friction layer powder adhering to at least one side of the molten auxiliary forming layer to form a molten low-friction layer. Specifically, the powder feeder may include the following components: a discharge port 45-01 and a scraper 45-02.

[0239] Specifically, the composite extrusion molding system may include the following components: a screw feeder 415, a third composite die 416, a second extruder 417, a third extruder 418, a first external shaping device 419, a first internal shaping device 420, a second internal shaping device 421, a tube cooling and shaping device 422, and a second frame base 423.

[0240] See Figure 45 The ultra-high molecular weight polyethylene powder feeder is used to achieve quantitative and uniform powder distribution. The feeder outlet is a flat slit type and has a scraper to achieve powder flatness and thickness control.

[0241] In this embodiment, the extrusion molding system for forming the A1-B-A2-C composite structure mainly includes: a screw feeder for conveying the A2-C layer composite strip, a third composite die for the composite A1-B-A2-C layer structure, a second extruder for extruding the B2 layer, a third extruder for extruding the A1 layer, a first outer shaping device, a first inner shaping device and a second inner shaping device, a pipe cooling and shaping device, and a second frame base connecting the above structures.

[0242] Figure 46 A schematic diagram of the pressing device is shown.

[0243] In this embodiment, the composite preform forming system further includes at least one first pressing device and / or at least one second pressing device.

[0244] The first pressing device can be located between the low friction layer powder feeding device and the heating device. The first pressing device is used to apply pressure to the low friction layer powder toward the auxiliary forming layer.

[0245] The second pressing device can be located at the outlet end of the blank forming device. The second pressing device is used to apply pressure to the molten low-friction layer toward the molten auxiliary forming layer.

[0246] Specifically, the first pressing device includes at least one pair of parallel first extrusion rollers, the extrusion contact surface of the extrusion rollers near the low-friction powder layer being non-smooth. And / or, the second pressing device includes at least one pair of parallel second extrusion rollers, the extrusion contact surface of the second extrusion rollers being smooth.

[0247] For example, the powder pressing device is the first pressing device, consisting of a temperature-controlled upper mold 46-01 and a lower mold 46-02. The upper mold 46-01 has multiple small protrusions to facilitate the pressing of powder onto the molten strip. The upper mold 46-01 and the lower mold 46-02 are structured as rotating roller sets, with at least one roller set or a pressing unit capable of vertical movement, with at least one pressing unit. The gap between the upper mold 46-01 and the lower mold 46-02 is adjustable. The entire pressing device is connected to the frame base.

[0248] For example, the powder pressing device is a second pressing device, consisting of a temperature-controlled upper mold 411-01 and a lower mold 411-02. The smooth surfaces of the upper mold 411-01 and lower mold 411-02 facilitate the flattening of the composite strip. The structure formed by the upper mold 411-01 and lower mold 411-02 is a rotating roller assembly, with at least one roller assembly or a pressing unit capable of vertical movement, with at least one pressing unit. The gap between the upper mold 411-01 and lower mold 411-02 is adjustable. The entire pressing device is connected to the frame base.

[0249] In some embodiments, the blank forming apparatus may include an extrusion device and a first sheet forming die. The extrusion device is used to extrude a molten auxiliary forming layer; the first sheet forming die is disposed at the outlet end of the extrusion device and is used to form the molten auxiliary forming layer into a sheet of a first preset size.

[0250] Accordingly, the low-friction layer powder feeding device includes: a powder feeder, a discharge structure, a powder laying structure, and a first heating module.

[0251] The components include a powder feeder for accommodating the low-friction layer powder, a discharge structure connected to the powder feeder for discharging the low-friction layer powder onto at least one surface of the molten auxiliary forming layer, and a powder spreading structure for forming a uniformly spread low-friction layer powder on at least one surface of the molten auxiliary forming layer.

[0252] In some embodiments, the heating device includes a first heating module for non-contact heating of the low-friction layer powder; and / or a second heating module for non-contact or contact heating of the low-friction layer powder that is at least partially molten.

[0253] Figure 47 A schematic diagram of the heating device is shown. The heating device may include an upper heater 47-01 and a lower platform 47-02. For example, the upper heater 47-01 is suspended a certain distance above the conveyor belt, and this distance is adjustable to prevent unmelted powder from adhering to the heater; the lower platform 47-02 is a temperature-controlled platform, and the heat source for the heater is preferably infrared heating or microwave heating. The entire heating device is connected to the frame base 1.

[0254] In some embodiments, the composite extrusion molding system is also referred to as a composite preform forming system. The composite preform forming system further includes a second sheet forming die and / or a conveying device.

[0255] The second sheet forming mold is located at the outlet end of the second pressing device and is used to form the molten auxiliary forming layer and the molten low friction layer into a sheet of the second preset specification.

[0256] The conveying device is used to convey the molten auxiliary forming layer, and the low friction layer powder feeding device is specifically used to form low friction layer powder on at least one side of the molten auxiliary forming layer during the conveying process of the molten auxiliary forming layer.

[0257] In some embodiments, the second sheet forming die is also called a material-carrying shaping die, which includes a sheet channel through which heating modules, heat insulation plates, and cooling modules are arranged in sequence.

[0258] The heating module is used to raise the temperature of the auxiliary forming layer and low-friction layer in the sheet material channel. The heat insulation plate is used to block heat exchange between the heating module and the cooling module. The cooling module is used to cool the auxiliary forming layer and low-friction layer in the sheet material channel.

[0259] See Figure 48 and Figure 49As shown, the shaping die with material can include a cold mold body 412-01, a hot mold body 412-02, a heat insulation plate 412-03, a small support 412-04, and a second shaping die 412. Specifically, the shaping die is composed of mold bodies with independent cold and hot functions, with a heat insulation plate placed between the cold and hot mold bodies. The second shaping die is mounted on the small support. The entire shaping die is connected to the machine frame base through the small support.

[0260] The sheet obtained through the shaping die with the material is a laminated sheet consisting of a molten auxiliary forming layer and a molten low-friction layer. This laminated sheet can be used to form wound tubes.

[0261] Specifically, the composite pipe forming system may include: a screw feeder and a composite forming mold.

[0262] The spiral feeder is used to spirally wind the laminated sheets with overlapping edges to form a spirally wound tube blank. The composite molding die includes a blank leveling chamber for leveling the surface of the spirally wound tube blank during the conveying of the tube blank toward the tube outlet of the composite molding die.

[0263] For example, a spiral feeder includes a drive unit and a spiral component, the outer surface of which includes a non-smooth section, and when the spiral component is driven by the drive unit, the edges of the laminated sheets spirally wound around the outer surface of the non-smooth section.

[0264] The composite molding die includes a core mold and a first inner mold body. The spiral component has a cavity and is nested on at least a portion of the outer surface of the core mold. The first inner mold body is nested on at least a portion of the outer surface of the spiral component, and a blank flattening chamber is formed between the first inner mold body and the spiral component.

[0265] Please see also Figures 50 to 52 Spiral ridge 415-01, second die bracket 415-02, transmission wheel 415-03, drive device 415-04, straight section without spiral ridge 415-05, core mold 416-05, second frame base 423.

[0266] For example, the screw feeder is a temperature-controlled annular cylinder with spiral ridges distributed along its outer cylindrical surface from tail to head within a certain distance. The entire annular cylinder fits onto the mandrel on the third composite die, and is rotatably connected to the second frame base via the mandrel and the second die support. That is, the screw feeder is axially limited and rotates around the mandrel, allowing the A2-C layer composite strip to be fed into the third composite die. A drive wheel, fixed to the tail of the screw feeder, is installed between the tail of the screw feeder and the die support. This drive wheel is matched with an independent drive device to achieve rotational transmission. When the straight section without spiral ridges at the head of the screw feeder rotates, it spins the A2-C layer composite strip, causing the spiral joints of the A2-C layer composite strip to fuse into an A2-C layer composite annular cylinder material. The inner layer is C layer material, and the outer layer is A2 layer material. Simultaneously, the circumferential orientation of the C layer material chains further improves the inner layer strength.

[0267] In some embodiments, the composite molding die further includes an outer mold body nested on the outer surface of a first inner mold body. A tube wall outer surface layer forming chamber formed between the outer mold body and the first inner mold body is provided for the molten tube wall outer surface layer to be located on the side of the leveled spiral wound tube blank away from the tube axis, so as to co-extrude the leveled spiral wound tube blank and the tube wall outer surface layer.

[0268] The composite pipe forming system may also include a pipe wall surface material feeding device, which includes a pipe wall surface material container and a pipe wall surface material extruder. The pipe wall surface material container is used to hold the raw material for the pipe wall surface, and the pipe wall surface material extruder is used to extrude the raw material into the pipe wall surface layer forming chamber.

[0269] Furthermore, the composite molding die may also include a second inner mold body and an outer mold body. The second inner mold body is nested on at least a portion of the outer surface of the first inner mold body. A wide-gauge polymer layer forming chamber is formed between the first and second inner mold bodies, where the molten wide-gauge polymer layer is located on the side of the planed spirally wound tube preform away from the tube axis. The outer mold body is nested on the outer surface of the second inner mold body. A tube wall outer surface layer forming chamber is formed between the outer mold body and the second inner mold body, where the molten tube wall outer surface layer is located on the side of the wide-gauge polymer layer away from the tube axis, to co-extrude the planed spirally wound tube preform, the wide-gauge polymer layer, and the tube wall outer surface layer.

[0270] In some embodiments, the composite pipe forming system further includes a wide-gauge polymer material feeding device and a pipe wall surface material feeding device.

[0271] The wide-specification polymer material feeding device includes a wide-specification polymer material container and a wide-specification polymer material extruder. The wide-specification polymer material container is used to hold wide-specification polymer raw materials; the details of the wide-specification polymer raw materials are as described above and will not be repeated here. The wide-specification polymer material extruder is used to extrude the wide-specification polymer raw materials into the wide-specification polymer layer forming chamber.

[0272] Accordingly, the pipe wall surface material feeding device may include: a pipe wall surface material container and a pipe wall surface material extruder. The pipe wall surface material container is used to hold the raw material for the pipe wall surface. The pipe wall surface material extruder is used to extrude the raw material into the pipe wall surface layer forming chamber.

[0273] Please refer to the following: Figures 53 to 56 The diagram shows a composite pipe forming system. The composite pipe forming system may include the following components: a first inner mold body 416-01, a second inner mold body 416-02, an outer mold body 416-03, a third die support 416-04, a core mold 416-05, channels for A2-C layers 416-06, flow channels for B2 layers 416-07, flow channels for A1 layers 416-08, pipe internal flow channel shape 416-09, a screw feeder 415, a second extruder 417, a third extruder 418, a first external shaping device 419, a first internal shaping device 420, a second internal shaping device 421, and a second frame base 423.

[0274] Specifically, the composite pipe forming system (also known as the third composite die) consists of a first inner die, a second inner die, an outer die, a screw feeder, and a mandrel axially connected together. The entire composite die is fixed to the machine frame base via a die bracket and a die base. The annular gap between the first and second inner die forms the B2 layer material flow channel, and the second extruder is connected to the second inner die. The annular gap between the second inner die and the outer die forms the A1 layer material flow channel, and the third extruder is connected to the outer die. The gap between the first inner die and the screw feeder forms the A2-C layer material channel; the annular gap between the non-screw section of the screw feeder head and the outer die forms the A1-B-A2-C layer material flow channel; the annular gap between the mandrel and the outer die gradually transitions to the desired pipe inner flow channel shape, transforming the extruded annular A1-B-A2-C layer material preform into the desired pipe inner flow channel shape preform. The composite structure wall pipe adopts simultaneous internal and external sizing, that is, the first and second internal sizing devices are respectively connected to the composite die, and the external sizing device is connected to the frame base.

[0275] In some embodiments, to increase the accuracy of pipe forming, the composite pipe forming system further includes a composite pipe shaping system, which is disposed adjacent to the pipe outlet end of the composite forming mold, and is used to shape the inner wall and / or outer wall of the composite pipe output by the composite pipe forming system.

[0276] In this embodiment, the composite pipe shaping system includes an external shaping device and / or an internal shaping device. The external shaping device includes a drive mechanism and a clamping assembly capable of engaging, the drive mechanism driving the clamping assembly to move radially along the composite pipe. The internal shaping device includes at least one set of internal shaping modules, coaxially arranged with the composite pipe; the at least one set of internal shaping modules includes a heating module, a heat insulation plate, and a cooling module arranged sequentially. The heating module is used to increase the temperature of the composite pipe, the heat insulation plate is used to block heat exchange between the heating module and the cooling module, and the cooling module is used to cool the composite pipe.

[0277] Figure 57 and Figure 58 A schematic diagram of the external shaping device is shown. The external shaping device may include the following components: a first flap clamp 419-01, a second flap clamp 419-02, a slider 419-03, a guide rod 419-04, a guide groove 419-05, and a hydraulic cylinder 419-06.

[0278] Specifically, the main body of the external shaping device consists of two flap clamps, which can open and close in the radial direction of the tube. After closing, the tube shape is shaped. The closing motion of the flap clamps is driven by a hydraulic cylinder or a motor. At the same time, the flap clamps can reciprocate in the axial direction of the tube. While shaping, the outer surface of the tube is pushed and pulled. The pushing and pulling motion is driven by a hydraulic cylinder or a motor, which can improve the shaping accuracy of the tube and the smoothness of the tube surface.

[0279] The following is an exemplary description of the internal shaping device. See [link to documentation]. Figure 59 and Figure 60 The internal shaping device may include: a first internal shaping device hot mold body 420-01, a first internal shaping device cold mold body 420-02, a first internal shaping device heat insulation plate 420-03, a long rod 420-04, a third die bracket 420-05, an oil cylinder 420-06, a second internal shaping device mold body 421-01, a second internal shaping device guide rod 421-02, a core mold 416-05, and a second frame base 423.

[0280] Specifically, the internal shaping device consists of two shaping devices. The first internal shaping device comprises a mold with independent cooling and heating functions, with a heat insulation plate placed between the cooling and heating molds. The first internal shaping device is connected to the third die support via a long rod inside the core mold and then fixed to the second frame base. A hydraulic cylinder or motor is connected to the end of the long rod to realize the axial push-pull movement of the first internal shaping device on the pipe, improving the shaping accuracy of the internal flow channel and the smoothness of the inner surface of the pipe. At the same time, it orients the C-layer molecular chains on the inner wall of the pipe, improving its strength. The second internal shaping device comprises a temperature-controllable mold, connected to the mold of the first internal shaping device via a guide rod. It is also axially connected to a hydraulic cylinder or motor to realize the axial push-pull movement of the second internal shaping device on the pipe. Compared with the push-pull movement of the first internal shaping device, differential speed movement can be achieved, further improving the shaping accuracy of the internal flow channel and the smoothness of the inner surface of the pipe.

[0281] It should be noted that there are different pipe forming processes and equipment for pipes with different internal flow channel types. There are various types of equipment dies, such as dies for round pipes, polygonal pipes, and irregular pipes.

[0282] The following provides an exemplary description of each component.

[0283] The die is a key component located at the end of the extruder screw in an extrusion molding machine. Its main function is to impart a specific shape to the molten polymer material pushed from the extruder barrel, allowing the material to form the desired product profile, such as pipes, profiles, films, and other shapes, after exiting the die. For example, in pipe extrusion, the die's structural design allows the molten plastic to be extruded around the mandrel, forming a hollow pipe shape.

[0284] The structural features of a pipe die are that it typically includes a die body, a mandrel, and an adjusting device. The internal channel of the die body is annular, designed to allow the molten plastic to flow uniformly around the mandrel. The mandrel, located at the center of the die, determines the inner diameter of the pipe. The adjusting device allows for fine-tuning of the mandrel's position to precisely control the pipe's wall thickness. For example, in some precision pipe extrusion processes, the adjusting device can control the pipe wall thickness error within a very small range, ensuring pipe quality.

[0285] Its main application is in the production of various plastic pipes, such as water supply and drainage pipes (PVC pipes, PE pipes, etc.) and gas transmission pipes in the construction industry. These pipes have high requirements for dimensional accuracy, wall thickness uniformity, and mechanical properties, and pipe dies can meet these requirements.

[0286] In extrusion molding equipment, the heating module is a device used to heat the extruder barrel, die, and other related components. Its main function is to heat the polymer material from a solid state to a molten state, allowing the material to flow smoothly through the extruder and be extruded through the die. Simultaneously, proper heating ensures uniform material flowability, which has a crucial impact on product quality, such as dimensional accuracy and surface smoothness. For example, in the extrusion of polyvinyl chloride (PVC), PVC granules need to be heated to approximately 160-190°C to achieve good flowability for extrusion into pipes or profiles.

[0287] Heating modules are typically equipped with temperature sensors and temperature controllers. Temperature sensors (such as thermocouples or resistance temperature detectors) monitor the temperature of the barrel or die in real time and feed the temperature signal back to the temperature controller. The temperature controller, based on the set temperature value and the actual temperature signal, controls the temperature by adjusting the power of the heating module (e.g., changing the current of the resistance heating module, the frequency and power of the induction heating module, and the radiation intensity of the infrared heating module). Advanced temperature controllers can achieve high-precision temperature control with an error range within ±1-2℃, ensuring that polymer materials are extruded and molded at the appropriate temperature.

[0288] For example, heating module types include: resistance heating modules, induction heating modules, infrared heating modules, and temperature control and regulation.

[0289] For example, the principle and structure of resistance heating modules: Resistance heating is one of the most common heating methods. It utilizes the flow of electric current through a heating element with a certain resistance (such as a resistance wire) to generate heat. In extruders, resistance heating modules typically consist of a resistance wire wound around the outer layer of the barrel or die, and then wrapped with a layer of insulating material. When current passes through the resistance wire, heat is generated according to Joule's law (Q = I²Rt, where Q is heat, I is current intensity, R is resistance, and t is time). This heat is then transferred to the polymer material inside the barrel or die through thermal conduction.

[0290] Its advantages include: simple structure, low cost, and easy installation and maintenance. Its heating power can be controlled by adjusting the current, enabling relatively precise temperature control. Furthermore, the resistance heating module has a wide heating range, meeting the heating needs of various polymer materials.

[0291] However, it also has corresponding drawbacks: its heating efficiency is relatively low, especially when rapid heating is required, which may consume more electrical energy. Furthermore, because heat is transferred through thermal conduction, a temperature gradient may occur inside the barrel or die, meaning the temperature is higher near the heating element and lower further away, affecting the uniform heating of the material.

[0292] The principle and structure of induction heating modules are based on the principle of electromagnetic induction. When an alternating current passes through the induction coil, an alternating magnetic field is generated around it. If the barrel or die is made of a conductive material (such as metal), an induced current (eddy current) will be generated inside the barrel or die under the influence of the alternating magnetic field. According to Joule's law, the induced current will cause the barrel or die to heat up on its own. This heating method relies on the barrel or die itself generating heat, rather than conducting heat through external heating elements.

[0293] The advantages of induction heating modules include rapid heating, enabling the barrel or die to reach the required temperature in a short time. They also offer high heating efficiency because heat is generated within the barrel or die itself, reducing heat loss during transfer. Furthermore, since the heat is generated within the barrel or die itself, the internal temperature distribution is relatively uniform, which is beneficial for the uniform heating of polymer materials and improves product quality.

[0294] However, induction heating modules have higher equipment costs, including the induction coil and power supply, which are more expensive than resistance heating modules. Furthermore, the control system of induction heating modules is relatively complex, requiring precise control of parameters such as frequency and power, which demands a higher level of technical skill from operators.

[0295] The principle and structure of an infrared heating module include: Infrared heating utilizes the thermal radiation of infrared rays. An infrared heating module typically consists of an infrared radiation source (such as an infrared lamp or ceramic infrared emitter) and a reflector. The infrared radiation source emits infrared rays, which can directly penetrate the air and be absorbed by the surface of the barrel or die, converting them into heat energy. The reflector's function is to concentrate and reflect the infrared rays onto the area requiring heating, improving heating efficiency.

[0296] Infrared heating modules are characterized by rapid heating and high energy conversion efficiency. They can achieve rapid temperature rise, and because they use thermal radiation heating, they do not suffer from problems such as poor contact that can occur with resistance heating. Infrared heating modules can also selectively heat specific areas; for example, if certain localized areas of the die require higher temperatures, this can be achieved by adjusting the position and angle of the infrared radiation source.

[0297] However, the heat distribution of infrared heating depends primarily on the position and angle of the radiation source. Therefore, uneven heating may occur for complex-shaped barrels or dies. Furthermore, the penetration depth of infrared radiation is limited, which may prevent the internal material from being fully heated for thicker barrels or dies.

[0298] The cooling module is a crucial component of extrusion molding equipment, primarily responsible for cooling and solidifying the extruded, high-temperature plastic product. When molten polymer material is extruded through a die, its temperature is high, and it is in a soft, malleable state. The cooling module removes heat, rapidly cooling and solidifying the material to achieve the desired shape and dimensional accuracy. It also helps improve the product's physical properties, such as increasing hardness and strength.

[0299] Key factors in the cooling process include cooling rate control and cooling uniformity. Regarding cooling rate control: the cooling rate has a significant impact on product quality. If the cooling rate is too fast, it may lead to uneven shrinkage of the product's surface and interior, generating internal stress and causing defects such as warping and cracking. Conversely, if the cooling rate is too slow, it will prolong the production cycle and may affect the dimensional accuracy of the product. Therefore, it is necessary to rationally control the cooling rate based on the characteristics of the polymer material and the shape and size of the product. For example, for crystalline polymer materials, the cooling rate affects their crystallinity, thereby altering the product's physical properties.

[0300] Regarding cooling uniformity: Ensuring uniform cooling is crucial to preventing product deformation. Whether using air-cooled, water-cooled, or oil-cooled modules, measures must be taken to ensure even heat dissipation across all parts of the product. For example, in air-cooled systems, the location and direction of the fan must be carefully designed; in water-cooled systems, the cooling water must flow evenly around the product; and in oil-cooled systems, the oil must be evenly distributed within the cooling components.

[0301] For example, the cooling module can be an air-cooled module. Air-cooled modules use air as the cooling medium. They typically include a cooling fan and ventilation ducts. The fan blows cool air towards the extruded plastic product, carrying away heat through convection. The ventilation duct design allows control over the direction and speed of the cool airflow, resulting in more uniform cooling. Some air-cooled modules are also equipped with air filters to ensure the air blown onto the product is clean and prevents impurities from contaminating it.

[0302] Air-cooled modules are simple in structure, low in cost, and easy to operate. Unlike water-cooled modules, they do not pose a risk of leakage, making them a safer cooling method for some humidity-sensitive polymer materials. Furthermore, air-cooled modules allow for flexible adjustment of cooling direction and intensity, making them suitable for cooling products of various shapes. However, air cooling efficiency is relatively low, especially for thick-walled or large plastic products, where it may not be able to quickly and effectively reduce product temperature. Additionally, airflow can lead to uneven cooling of the product surface, potentially causing deformation or internal stress.

[0303] For example, the cooling module can be a water-cooled module, which uses water as the cooling medium. It typically consists of a cooling water tank, a circulating water pump, and cooling water pipes. Extruded plastic products are directly immersed in the cooling water tank or cooled by cooling water pipes wrapped around the product surface. The circulating water pump keeps the cooling water flowing through the system, continuously carrying away heat. To improve cooling efficiency, some water-cooled modules also add coolant to the water or use refrigeration equipment to lower the water temperature.

[0304] Water-cooled modules offer high cooling efficiency, rapidly reducing product temperature and making them suitable for rapid, continuous extrusion production. For thick-walled or large plastic products, water cooling effectively prevents internal heat buildup, reducing cooling time and the likelihood of deformation. However, water-cooled modules pose a risk of leakage. If cooling water leaks onto the product, it can affect product quality, especially for water-sensitive polymers, potentially leading to performance degradation. Furthermore, water-cooled modules are more complex and require regular maintenance of components such as the cooling water tank, pump, and pipes to prevent scale buildup and equipment damage.

[0305] For example, a cooling module can be an oil-cooled module, which uses oil as the cooling medium. The oil flows through a circulation system across cooling plates or pipes that come into contact with the product, carrying away heat. An oil-cooling system typically includes an oil tank, oil pump, oil cooler, and oil pipes. The oil pump draws oil from the tank, cools it in the oil cooler, and then delivers it to the cooling components that come into contact with the product, before returning it to the tank for reuse. Oil has a high specific heat capacity and strong cooling capacity, and oil-cooled modules can provide relatively uniform cooling. Oil has good thermal conductivity and stability, and unlike water, it does not evaporate or freeze easily, making it suitable for some temperature-sensitive extrusion processes. However, oil-cooled modules are more expensive, including both the cost of the oil and the equipment. Oil itself is a contaminant; if it leaks into the product or environment, it can cause pollution and is difficult to clean up. Furthermore, oil may oxidize and deteriorate at high temperatures, requiring regular replacement and increasing maintenance costs.

[0306] Regarding heat insulation panels, they are devices used to reduce heat transfer and to block heat exchange between heating and cooling modules.

[0307] The materials used in thermal insulation panels typically have a very low thermal conductivity, which is their most important characteristic. Common insulation materials, such as ceramic fibers, have a thermal conductivity between 0.03 and 0.15 W / (m·K), effectively preventing heat conduction. Thermal insulation panels need to be able to withstand high-temperature environments.

[0308] For example, insulation boards can be made of ceramic fiber, which has advantages such as light weight, good thermal insulation performance, high temperature resistance, and strong chemical stability. Its fiber structure gives it a certain degree of flexibility, allowing it to be bent or cut appropriately according to the shape of the equipment. Its low thermal conductivity effectively reduces heat loss, and it can withstand high temperatures of 1000-1300℃, making it suitable for insulation of high-temperature extrusion molding equipment.

[0309] For example, insulation boards can be made of rock wool, a fibrous insulation material made from natural rock. It has excellent thermal insulation, sound absorption, and fire resistance. Rock wool has a low thermal conductivity, typically around 0.03-0.04 W / (m·K), effectively preventing heat transfer. Furthermore, it is a non-combustible material, offering significant advantages in environments with high fire safety requirements. In addition, foam insulation boards (such as polystyrene foam and polyurethane foam) can be used in scenarios where high-temperature resistance requirements are not stringent.

[0310] A screw feeder is a device used to uniformly and quantitatively convey powder into equipment such as extruders. It mainly consists of a hopper, a screw shaft, screw blades, and a drive unit. Its basic principle is that the rotation of the screw blades propels the powder forward along the screw shaft. When the screw shaft rotates, the screw blades generate an axial thrust on the powder, causing it to gradually move from the bottom of the hopper to the discharge port, thus achieving powder conveying. Just like a rotating screw pushing a surrounding object, the screw blades propel the powder forward.

[0311] For example, the outer material container of the pipe wall can be a hopper, used to store the powder to be conveyed. Its shape and size are designed according to the characteristics of the powder and the required feeding rate. Generally, the upper opening of the hopper is larger to facilitate the addition of powder, while the bottom gradually narrows to allow the powder to smoothly enter the working area of ​​the spiral blades. For example, for plastic granules with good flowability, the inclination angle of the hopper can be appropriately reduced.

[0312] The auger shaft is one of the core components of the auger feeder, providing rotational support for the auger blades. The auger blades are in direct contact with the powder, propelling it forward through rotation. The pitch and blade shape of the auger blades have a significant impact on feeding performance. The pitch determines the distance the powder travels with each rotation, while the blade shape (such as equidistant blades, variable pitch blades, etc.) affects the way the powder is pushed and its uniformity.

[0313] The helical shaft generally needs sufficient strength and rigidity to withstand the torque generated by the rotation of the helical blades and the axial force of the powder. The thickness and material of the helical blades must be selected based on the abrasive properties of the powder. For powders with high abrasiveness, such as plastic composites containing glass fibers, thicker, more wear-resistant helical blades are required to prevent premature wear.

[0314] The drive unit provides rotational power to the screw shaft. Common drive units include motors and speed reducers. The motor serves as the power source, while the speed reducer adjusts the screw shaft's rotational speed, allowing for precise control of the feeding speed according to actual production needs. For example, at different extrusion speeds, adjusting the speed ratio of the speed reducer can adjust the feeding speed of the screw feeder to match the extruder's feed speed.

[0315] Regarding the chamber, in extrusion molding equipment, the chamber is mainly the space inside the molding equipment that contains the polymer material. It is the place where the powder changes from a solid particle state to a molten state and is conveyed forward by the screw. The front end of the barrel chamber is connected to the die, and the rear end is connected to the feeding device (such as a screw feeder), forming a complete channel for the powder in the extruder.

[0316] For example, the chamber may include a feeding zone, a compression zone, and a melting zone. The feeding zone is located at the rear of the chamber, near the powder inlet. This area typically has a relatively large diameter to facilitate smooth powder entry. The inner wall of the feeding zone is generally smooth to reduce friction between the powder and the wall. Some extruders also have cooling devices in the feeding zone to prevent the powder from softening or agglomerating prematurely due to frictional heat during feeding.

[0317] The compression zone is located in front of the feeding zone, and its chamber diameter gradually decreases. The screw pitch and thread depth also change in this area, typically decreasing in pitch and decreasing in thread depth. This structural design allows the powder to be gradually compressed during forward transport. The main function of the compression zone is to compact the powder and expel air from it. When the powder is compressed, air is forced out, which helps increase the powder density, making subsequent heating and melting processes more uniform and efficient. Simultaneously, compression also enhances the friction between powder particles, helping the screw to propel the powder forward more effectively.

[0318] The melting zone, located after the compression zone, is typically equipped with a heating device. This device heats the polymer material within the zone to above its melting or softening point, gradually transforming the polymer powder into a molten state. The screw design in the melting zone also facilitates powder mixing and melting, such as using a special screw shape or incorporating mixing elements on the screw. The powder in the melting zone transforms into a molten state, preparing it for extrusion molding. During this process, the powder's physical properties, such as temperature and viscosity, undergo significant changes. Effective heating and the screw's stirring and mixing action ensure complete powder melting and uniform properties throughout, preventing unmelted solid particles from being trapped in the molten powder and affecting product quality.

[0319] In some embodiments, the chamber may also include a metering zone. For example, the metering zone is located in front of the molten zone, close to the die. The screw diameter and pitch in this zone are relatively stable, allowing for precise control of the molten powder delivery rate. The inner diameter of the chamber and the screw dimensions are precisely matched to ensure that the powder is delivered to the die at a constant flow rate. The main function of the metering zone is to precisely control the powder flow rate, enabling the extrusion process to proceed stably and continuously. By adjusting parameters such as the screw rotation speed, the speed at which the powder is delivered in the metering zone can be changed, thereby adapting to different extrusion speed requirements and product size specifications.

[0320] The composite pipe shaping system is a series of devices used to cool and shape the composite pipe after extrusion molding. Its importance lies in ensuring the dimensional accuracy, shape stability, and good adhesion between the layers of material in the composite pipe. During the composite pipe extrusion process, because multiple layers of different materials are extruded and bonded together simultaneously, the process of the pipe changing from a molten state to a solid state requires precise control. The shaping system is the key link in achieving this control and directly affects the quality and performance of the composite pipe.

[0321] In some embodiments, the clamping assembly capable of engaging can also be referred to as an engaging sizing sleeve. The sizing sleeve is a component that directly contacts the pipe and is used to determine the outer diameter of the pipe. It can be installed at the front end of a vacuum forming device or cooling device. The sizing sleeve has a precise inner diameter and a smooth surface. When the pipe passes through the sizing sleeve, its outer diameter is restricted by the sizing sleeve, thereby achieving the purpose of shaping. The material of the sizing sleeve generally needs to have good wear resistance and thermal conductivity to accommodate the friction and heat transfer of the pipe. The sizing sleeve can provide precise control over the outer diameter of the pipe, and when used in conjunction with a vacuum forming device, it can better ensure the dimensional stability of the pipe. For composite pipes, the sizing sleeve can also help adjust the relative positions between the layers of material, ensuring the uniformity of the composite structure.

[0322] In some embodiments, the spiral wound pipe forming apparatus is a device for manufacturing spiral wound pipes. Its basic principle is to wind continuous reinforcing materials such as fibers, strips, or films onto a mandrel or inner layer pipe at specific angles and in a specific manner, while simultaneously combining them with a matrix material (such as resin). Through curing or bonding, a multi-layered pipe structure is formed. This forming method can fully utilize the high strength characteristics of the reinforcing materials, improving the mechanical properties of the pipe.

[0323] In some embodiments, the mandrel is the basic support structure for the wound tube, and its shape matches the inner diameter of the tube. The mandrel is typically cylindrical, possessing sufficient strength and rigidity to withstand the tension and pressure during the winding process. The mandrel surface is required to be smooth to ensure that the polymer composite tape adheres smoothly to its surface, and may require surface treatment, such as applying a release agent, to facilitate demolding after tube formation. The mandrel provides support for tube formation and determines the inner diameter of the tube. During the winding process, the mandrel acts as a rotating component, driving the polymer composite tape to wind around its surface at a specific helical angle, forming the key foundation of the entire forming process.

[0324] For example, a winding mechanism may include a guiding device and a winding head. The guiding device is used to guide the polymer composite tape to be wound on the mandrel at a predetermined angle and path, while the winding head is the key component for realizing the winding action. It can rotate and move according to the set winding pattern (such as helical winding, circumferential winding, etc.).

[0325] In addition, the winding mechanism may also include an unwinding device and a tension control system. The unwinding device is used to hold the roll of reinforcing material, and the tension control system can precisely control the tension of the polymer composite tape to ensure that it maintains proper tension during the winding process.

[0326] The tension control system ensures that the polymer composite tape is evenly wound onto the mandrel, avoiding pipe quality problems caused by excessively loose or tight material, such as uneven winding and wrinkles. The guiding device and winding head work together to precisely control the winding angle, number of layers, and speed of the polymer composite tape, thereby forming a pipe with specific structure and properties.

[0327] Regarding the winding head, it uses a rotating mechanism to drive the guiding device and tension control system to rotate together. Guided by the guiding device, the winding material is evenly wound onto the mandrel according to the set winding angle and number of layers. Simultaneously, the tension control system adjusts the tension of the winding material in real time to ensure stable tension during the winding process, thereby guaranteeing the winding quality of the pipe.

[0328] Spiral winding head: It can wind the material onto the mandrel at a certain spiral angle. This winding method can improve both the circumferential strength and the axial strength of the pipe, and is suitable for pipe forming with various requirements.

[0329] For example, the winding head may include a rotating mechanism and a rotating shaft.

[0330] The motor provides power for the rotation of the winding head, which is then transmitted to the rotating shaft via a speed reducer or other transmission device, enabling the winding head to rotate at a set speed and direction. For example, some large pipe winding machines use high-power servo motors to precisely control the rotation speed and position.

[0331] The rotating shaft is the core supporting component of the winding head. Other related components, such as guide devices and tension control systems, are installed on it to ensure that these components can rotate smoothly together with the rotating shaft.

[0332] The heating device can cause the polymer composite tape to adhere and cure at overlapping areas under specific temperature and time conditions. Alternatively, resin can be used to enhance adhesion; for example, resin can be present at least in the overlapping areas, and ultraviolet light can be used to initiate the curing reaction.

[0333] The following is an illustrative description of the working process of a multi-layer composite pipe forming equipment.

[0334] PE sheet (A2 layer) is extruded through a first extruder and a first die. Then, a layer of ultra-high molecular weight polyethylene (UHMWPE) powder is added to the uncured A2 layer by a first feeder, forming a composite. The composite is then pressed by a first set of pressing devices to compact the UHMWPE powder onto the A2 layer. The compacted composite passes through a first heating device, where the compacted UHMWPE powder melts. Another layer of UHMWPE powder is then added by a second feeder, forming a two-layer UHMWPE composite. This composite is further pressed by a second set of pressing devices to compact the UHMWPE powder onto the molten UHMWPE layer. The compacted composite passes through a second heating device, where the compacted UHMWPE powder melts. Finally, it passes through a third set of pressing devices, where the composite is compacted and gradually cooled, forming a strip of UHMWPE (C layer) and PE (A2 layer) of a certain thickness. The thickness of the C layer can be adjusted by adding the powder and pressing... The process involves multiple cycles of compaction, heating and melting, and pressing to control the density. The resulting A2-C layer composite strip passes through the second shaping die and is then fed into the third composite die via a screw feeder, forming a spirally wound, dense ring. Layer C is located on the inner wall of the ring, and layer A2 is located on the outer wall. Subsequently, a second extruder extrudes molten foamed PE material (layer B) to clad onto layer A2, forming a three-layer composite material (C, A2, and B) from the inside out. This composite material is then pushed forward, and finally, the third extruder extrudes molten PE... Material E (layer A1) is clad onto layer B, ultimately forming a multi-layered composite within the composite die. This consists of four composite layers from the inside out: layer C, layer A2, layer B, and layer A1. These layers are extruded together in the die's discharge direction. During this process, layer B gradually foams and expands, compressing the other three layers. The composite layers gradually cool and solidify under circumferential compression, creating circumferential stress. Layer C is shaped by the core mold, and layer A1 is shaped by the outer die, resulting in a smooth surface. Finally, a smooth-walled tube with a composite structure is formed.

[0335] Another aspect of the present invention provides a composite pipe system for improving clogging.

[0336] The composite pipe system includes a backfill environment and composite pipes. The composite pipes are installed in the backfill environment.

[0337] Specifically, the composite pipe wall comprises an outer wall layer and a low-friction layer. This low-friction layer is located on the outer wall layer near the pipe's axis. The low-friction layer has a lower friction coefficient than the outer wall layer, and its material includes an ultra-high molecular weight polymer and an antioxidant.

[0338] The materials, structure, forming methods, and forming equipment of composite pipes can be found in the above-mentioned content and will not be elaborated here.

[0339] The composite pipe system for improving clogging provided by this invention can effectively reduce the risk of clogging and reduce maintenance and / or repair costs compared to existing pipe systems.

[0340] Another aspect of the present invention provides a method for improving blockage using composite pipes.

[0341] See Figure 61 The method includes steps S310 to S330.

[0342] In step S310, the composite pipe is laid into the drainage environment.

[0343] In step S320, the flowing liquid carries away at least the deposits adhering to the inner surface of the composite pipe on the side closest to the Earth's core.

[0344] In step S330, the lifespan of the liquid piping system is increased by using composite pipes.

[0345] The composite pipe wall includes: an outer wall layer; and a low-friction layer located on the side of the outer wall layer closer to the pipe axis; the friction coefficient of the low-friction layer is less than that of the outer wall layer, and the material components of the low-friction layer include: ultra-high molecular weight polymer and antioxidant.

[0346] The materials, structure, forming methods, and forming equipment of composite pipes can be found in the above-mentioned content and will not be elaborated here.

[0347] In some embodiments, the stress analysis of various pipe materials in this invention is performed using the finite element method. The stress on the pipe materials is as follows: Figure 62 As shown.

[0348] Finite element analysis description: All analyzed products are single-layer solid-wall pipes with a wall thickness of 29.7mm and a pipe length of 700mm. The pipe material is HDPE. Comparative analyses were conducted on circular solid-wall pipes, published egg-shaped pipes, and the self-cleaning pipe examples provided in this patent. For example, in Table 1, the pipe with a height H of 600mm is shown. The external force applied to the pipe is F = 15 tons. A loading diagram is shown below. Figure 62 As shown.

[0349] See Figure 63 The pipe is a conventional circular tube. Stress-deformation analysis results show that the tube gradually transforms into an elliptical shape, with the internal flow channel deforming outwards from the center of the tube.

[0350] See Figure 64 For egg-shaped pipes, stress-deformation analysis results show that as the pipe gradually shortens, the convex arc of the inner flow channel in the middle of the pipe deforms outward from the center of the pipe, the radius of the bottom arc gradually increases, and the self-cleaning effect gradually fails.

[0351] See Figure 65 Taking the pipe in Table 1 with a height H of 600, a first opening that is an arc, and a connecting structure with a slanted straight edge as an example, the stress-deformation analysis results show that as the pipe gradually decreases in height, part of the inner flow channel connecting structure in the middle of the pipe deforms inward toward the center of the pipe, and the self-cleaning effect does not fail.

[0352] See Figure 66 For the pipe in Table 1 with a height H of 600, a first opening that is an arc, and a connecting structure that is an inwardly concave arc, the stress-deformation analysis results show that as the pipe gradually decreases in height, a large portion of the inner flow channel connecting structure in the middle of the pipe deforms inward toward the center of the pipe, and the self-cleaning effect does not fail.

[0353] See Figure 67 Taking the pipe with a height H of 600mm in Table 1, whose first opening consists of two straight edges and an arc, and whose connecting structure is a beveled straight edge, as an example, the stress-deformation analysis results show that as the pipe gradually decreases in height, part of the inner flow channel connecting structure in the middle of the pipe deforms inward towards the center of the pipe, and the self-cleaning effect does not fail. At the same time, the first opening consisting of two straight edges and an arc provides support, compared to the pipe with a first opening consisting of one arc and a connecting structure with a beveled straight edge (see Table 1). Figure 65 The corresponding pipe structure has higher pipe strength.

[0354] See Figure 68 Taking the pipe with a height H of 600mm in Table 1, a first opening with three straight edges, and a connecting structure with beveled straight edges as an example, the stress-deformation analysis results show that as the pipe gradually decreases in height, part of the inner flow channel connecting structure in the middle of the pipe deforms inward towards the center of the pipe, and the self-cleaning effect does not fail. At the same time, the first opening with three straight edges provides support, compared to the pipe with a first opening that is an arc and a connecting structure with beveled straight edges (see...). Figure 65The corresponding pipe structure has higher pipe strength.

[0355] The following provides an illustrative example of the actual effect of the self-cleaning function of the aforementioned pipes.

[0356] This patent relates to experiments conducted on pipes with self-cleaning internal flow channels. Pipe specifications are shown in Tables 6 and 7 below, with the corresponding pipes categorized into single-layer solid-wall pipes and multi-layer composite pipes. Each type of pipe has four different internal flow channels. The corresponding internal flow channel height H is 600mm. The first opening of the pipe uses a single circular arc design, the second opening uses a single circular arc and three circular arcs, and the connection structure uses a slanted straight edge or an inwardly concave circular arc. Combinations of these three structures result in four different self-cleaning capabilities. Furthermore, for the multi-layer composite pipes, the innermost layer is a low-friction layer E4 of ultra-high molecular weight polyethylene, corresponding to different friction coefficients. Table 6 shows the single-layer solid-wall pipe material as HDPE. Table 7 shows the multi-layer composite pipe material, with the outermost layer E1 being HDPE, the wide-gauge polymer layer E2 being HDPE microporous foam material, the auxiliary molding layer E3 being HDPE, and the low-friction layer E4 being ultra-high molecular weight polyethylene.

[0357] During the experiment, the self-cleaning pipes were spliced ​​together to a length of 30 meters. Bases were installed at the bottom of the pipes to ensure they did not tilt laterally. The pipes were installed at a 2° tilt angle, and the highest point of the laid pipes was connected to a large water tank. Silt, leaves, branches, and water were mixed in the large water tank. Two water levels were used during the experiment: 120 mm (0.2H) and 420 mm (0.7H). Water flowed naturally from the large water tank into the corresponding pipes. After 10 minutes of drainage, the deposition of solid foreign matter inside the pipes was observed. The results showed that from the drainage inlet to the drainage outlet (within 30 meters), silt was deposited to varying degrees at the bottom of the pipes, and branches and leaves were suspended inside the pipes to varying degrees. The specific conditions for each pipe type are shown in Tables 6 and 7.

[0358] Table 6

[0359]

[0360]

[0361] Table 7

[0362]

[0363]

[0364] In another embodiment, a flushing experiment was conducted on the sediment inside the pipes from the above embodiment. During the experiment, the large water tank contained only water, free of visible silt, leaves, branches, or other foreign objects. Two water depths were used during the experiment: 120 mm (0.2H) and 420 mm (0.7H). Water flowed naturally from the large water tank into the corresponding pipes. After 5 minutes of drainage, the cleanliness of the original solid sediment was observed. The results showed that from the drainage inlet to the drainage outlet (within 30 meters), the silt at the bottom of the pipes was cleaned to varying degrees, especially in multi-layer composite wall pipes with an ultra-high molecular weight polyethylene inner layer, where the original solid sediment was almost completely cleaned. Examples of single-layer solid wall pipe specifications are shown in Table 8, and examples of multi-layer composite pipe specifications are shown in Table 9.

[0365] Table 8

[0366]

[0367]

[0368] Table 9

[0369]

[0370]

[0371] The composite pipe system for improving clogging provided by this invention can effectively reduce the risk of clogging and reduce maintenance and / or repair costs compared to existing pipe systems.

[0372] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for forming a multi-layer composite pipe, characterized in that: A composite preform is formed, the composite preform comprising a molten auxiliary molding layer and a low-friction layer powder adhered to at least one side of the molten auxiliary molding layer; The low-friction layer powder is heated to form a molten low-friction layer on at least one side of the molten auxiliary forming layer; The molten auxiliary forming layer and the molten low-friction layer are formed into the composite pipe. The friction coefficient M of the low-friction layer is less than the friction coefficient of the outer surface layer of the composite pipe, and the material of the low-friction layer includes: ultra-high molecular weight polymer and antioxidant.

2. The molding method according to claim 1, characterized in that, Also includes: After heating the low-friction layer powder, a molten, wide-gauge polymer layer is formed on the side of the composite preform away from the low-friction layer.

3. The molding method according to claim 2, characterized in that, Also includes: After the wide-gauge polymer layer is formed, a molten composite pipe outer layer is formed on the side of the molten wide-gauge polymer layer away from the low-friction layer.

4. The molding method according to claim 3, characterized in that, The wide-gauge polymer layer includes a foamed structure. The molding method further includes: after forming a molten composite pipe outer surface layer on the side of the molten wide-gauge polymer layer away from the low-friction layer, the wide-gauge polymer layer is extruded during the foaming process to form the composite pipe outer surface layer and the auxiliary molding layer.

5. The molding method according to claim 1, characterized in that: The process of forming the composite preform includes: The modified low-friction layer powder is conveyed into the first composite molding die, wherein the material of the low-friction layer powder includes: ultra-high molecular weight polyethylene and antioxidant; The molten auxiliary molding layer is applied to the modified low-friction layer powder in the first composite molding mold to form the composite preform; The heating of the low-friction layer powder includes: The modified low-friction layer powder is heated by the core mold in the first composite molding die and the molten auxiliary molding layer.

6. The molding method according to claim 1, characterized in that: The process of forming the composite preform includes: Extrusion of the auxiliary forming layer; Modified low-friction layer powder is added to the uncooled and uncured auxiliary molding layer to obtain an initial composite preform; The initial composite preform is pressed to form the composite preform; The heating of the low-friction layer powder includes: The side of the auxiliary forming layer away from the low-friction layer powder is subjected to contact heating, and the side of the auxiliary forming layer containing the low-friction layer powder is subjected to contact and / or non-contact heating.

7. The molding method according to claim 6, characterized in that, The formation of the composite preform also includes: After heating the low-friction layer powder, repeat the following operation at least once: A modified low-friction layer powder is added to one side of the low-friction layer powder in the composite preform; Press the composite preform; The low-friction layer powder is heated.

8. The molding method according to claim 1, characterized in that, The process of forming the composite pipe from the molten auxiliary forming layer and the molten low-friction layer includes: The composite pipe is obtained by extruding the molten auxiliary forming layer and the molten low-friction layer through a pipe forming die. Wherein, the cross-section of the pipe forming mold is circular; or the first cross-sectional area of ​​the pipe forming mold is greater than the second cross-sectional area, the first cross-sectional area is the area of ​​the half-section of the composite pipe away from the earth's center after it is laid, and the second cross-sectional area is the area of ​​the half-section of the composite pipe close to the earth's center after it is laid.

9. The molding method according to claim 1, characterized in that, The process of forming the composite pipe from the molten auxiliary forming layer and the molten low-friction layer includes: The composite strip is obtained by extruding the molten auxiliary forming layer and the molten low-friction layer through a strip forming die. The composite strip is wound to obtain a composite strip spiral structure; The composite strip spiral structure is spun and heated to fuse the stacked portions of the composite strip spiral structure to obtain a composite columnar material; The composite cylindrical material is extruded to obtain the composite pipe.

10. The molding method according to claim 9, characterized in that, The composite tape spiral structure obtained by winding the composite tape includes: The composite tape is wound around a column with a specific cross-sectional shape; Wherein, the specific cross-sectional shape is circular; or the first cross-sectional area of ​​the specific cross-sectional shape is greater than the second cross-sectional area, the first cross-sectional area is the area of ​​the half-section of the composite pipe away from the Earth's center in the laid state, and the second cross-sectional area is the area of ​​the half-section of the composite pipe close to the Earth's center in the laid state.

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