Weather-resistant PVC pipe and forming method thereof

Abstract

The application discloses a kind of weather-resistant PVC pipe and its forming method, it is characterized in that, including: step S1, provide additive: waterproof polymer, ultraviolet absorber, low-temperature toughness modifier, composite crosslinking agent and self-healing nanocapsule;Step S2, three-stage mixing is sequentially formed third mixed layer;With in raw material pool Forming layered mixture with upper and lower three layers;Step S3, extrusion forming is carried out extrusion by multilayer co-extrusion die and forms the PVC pipe material of three-layer structure;Step S4, rapid cooling and solidification: carry out cooling fixed physical form, and the prepared PVC pipe material is formed;By layered mixing, so that pipe material has optimized three-layer structure, respectively provides the performance of ultraviolet resistance, waterproof and high mechanical strength, simultaneously realizes the maximum utilization rate of material, and ensures the good combination between each layer and the overall stability of material, improves the service life of weather-resistant PVC pipe material and the ability of adapting to specific environment.

Description

Technical Field

[0001] This invention relates to the field of PVC pipes, and more particularly to a weather-resistant PVC pipe and its forming method. Background Technology

[0002] With the continuous development of infrastructure construction, PVC pipes have been widely used in various application scenarios, especially in environments requiring long-term exposure to harsh weather conditions, such as marine coastal infrastructure, underground drainage systems, and outdoor power cable protection. These applications require PVC pipes to possess not only excellent mechanical strength and corrosion resistance, but also outstanding UV resistance and waterproofing properties to ensure their long-term stability and reliability in complex environments. Therefore, developing a multifunctional and efficient weather-resistant PVC pipe molding method has become a key technological requirement for improving pipe performance and extending service life.

[0003] In existing technologies, to achieve multifunctional weather resistance in PVC pipes, various functional additives (such as waterproofing, UV protection, and temperature resistance) are typically uniformly dispersed throughout the cross-section of the pipe during the manufacturing process. However, this uniform mixing method has significant drawbacks. First, the uniform distribution of each functional additive throughout the material limits the content of each additive, making it difficult to achieve optimal functional enhancement. Second, excessive additives mixed into the matrix significantly reduce the mechanical properties of the PVC pipe, such as toughness and strength, affecting its overall structural stability. Ultimately, these problems result in limited material utilization, and the overall weather resistance fails to meet expectations.

[0004] Therefore, existing technologies for molding multifunctional weather-resistant PVC pipes cannot simultaneously achieve both high material performance and high utilization rate. There is an urgent need for a molding method that can optimize the material structure and improve the conversion rate of each functional component. Summary of the Invention

[0005] The purpose of this invention is to provide a weather-resistant PVC pipe and its molding method, thereby solving the above-mentioned technical problems.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A method for molding a weather-resistant PVC pipe, comprising:

[0008] Step S1: Provide the additives: waterproof polymer, ultraviolet absorber, low-temperature toughness modifier, composite crosslinking agent and self-healing nanocapsules, and weigh each component.

[0009] Step S2, three-stage mixing: First, the waterproof polymer, low-temperature toughness modifier, composite crosslinking agent, and base PVC resin are mixed in the raw material pool under low shear force to form a first mixed layer; then, the composite crosslinking agent and base PVC resin are added to the first mixed layer to form a second mixed layer; finally, the ultraviolet absorber, composite crosslinking agent, and base PVC resin are added to the middle mixed layer under high shear force to form a third mixed layer; thus forming a layered mixture with three layers in the raw material pool.

[0010] Step S3, Extrusion molding: The layered mixture is conveyed to a multi-layer co-extrusion die through a vertical cross-section conveying channel, and extruded through the multi-layer co-extrusion die to form a three-layer PVC pipe;

[0011] Step S4, rapid cooling and curing: The extruded PVC pipe is rapidly cooled to room temperature using a multi-functional cooling mold to fix its physical form and obtain the molded PVC pipe.

[0012] Optionally, the waterproof polymer component is any one or a combination of several of polyvinyl alcohol, polyacrylate, polyurethane and polysiloxane, and its content in the first mixed layer is 5-15%;

[0013] The ultraviolet absorber component is any one or a combination of several of phenylbenzotriazole compounds, phenyl ketone compounds, and organic ultraviolet absorbers, and its content in the third mixed layer is 2-8%;

[0014] The low-temperature toughness modifier component is any one or a combination of butadiene rubber, ethylene-vinyl acetate copolymer, polyacrylonitrile and polybutadiene, and its content in the first mixed layer is 3-10%;

[0015] The composite crosslinking agent component is any one of vulcanizing agent, peroxide crosslinking agent, photoinitiating crosslinking agent and electron beam crosslinking agent, and its content in the layered mixture is 1-5%.

[0016] Optionally, step S2 specifically includes:

[0017] Step S21: In the raw material pool, add waterproof polymer, low temperature toughness modifier, composite crosslinking agent and base PVC resin in a predetermined ratio, mix using a twin-screw mixer, and adjust the twin-screw mixer to low shear mode.

[0018] Step S22: Set the mixing temperature to 160-180℃ and continue mixing for 10-15 minutes under low shear force to ensure that the waterproof polymer and low-temperature toughness modifier are fully and evenly dispersed with the base PVC resin to form the first mixed layer.

[0019] Step S23: Add the composite crosslinking agent and base PVC resin to the raw material pool again according to the predetermined ratio, increase the stirring height of the twin-screw mixer and maintain the low shear force mode, adjust the mixing temperature to maintain at 160-180℃, and mix for another 5-10 minutes under low shear force to make the composite crosslinking agent evenly distributed in the base PVC resin to form a second mixed layer.

[0020] Optionally, after step S23, the method further includes:

[0021] Step S24: Continue to add base PVC resin to the raw material tank, and then gradually add UV absorber and composite crosslinking agent according to the predetermined ratio. Increase the stirring height of the twin-screw mixer and switch the twin-screw mixer to high shear force mode. Adjust the mixing temperature to 170-190℃ and continue mixing under high shear force for 7-12 minutes to ensure that the UV absorber and composite crosslinking agent are evenly dispersed in the base PVC resin to form the third mixture.

[0022] Step S25: Using a layered stacking technique, the first mixing layer, the second mixing layer, and the third mixing layer are stacked sequentially to form a layered mixture with a three-layer structure.

[0023] Step S26: Rheological properties of the layered mixture are adjusted, and the overall temperature is stabilized at 175-185℃ using an interlayer temperature regulating device. The viscosity of the layered mixture is monitored in real time using a viscosity monitoring device. If an abnormal viscosity is detected, a corresponding thermal balance adjustment strategy is set and executed by activating the regulation mechanism of the interlayer temperature regulating device.

[0024] Optionally, step S3 specifically includes:

[0025] Step S31: The obtained layered mixture is transported from the raw material pool to the inlet of the extrusion molding equipment through a preheated conveying pipe. The conveying channel adopts a vertical cross-section design to ensure that the layers of the layered mixture remain clearly separated during the conveying process.

[0026] Step S32: Select a multi-layer co-extrusion die suitable for the three-layer structure, adjust the temperature control component of the multi-layer co-extrusion die for preheating, and set the die temperature in the range of 200-220℃.

[0027] Step S33: The layered mixture is introduced into the cavity of the multi-layer co-extrusion mold, the extrusion molding equipment is started, the speed and pressure of the extruder are controlled, and a three-layer PVC pipe is extruded.

[0028] Optionally, step S4 specifically includes:

[0029] Step S41: The formed three-layer PVC pipe is conveyed to the inlet of the multi-functional cooling mold through the conveying assembly;

[0030] Step S42: A zoned cooling system is used to cool the PVC pipes in layers, with independent cooling channels set up for the outer cooling zone, the middle cooling zone, and the inner cooling zone.

[0031] Step S43: The outer layer of the PVC pipe is rapidly cooled by the high-efficiency circulating coolant flowing in the outer cooling channel.

[0032] Optionally, step S43 may be followed by:

[0033] Step S44: After the outer layer is cooled, the PVC pipe is slowly cooled through the intermediate layer cooling channel and the inner layer cooling channel using a preset coolant temperature and flow rate.

[0034] Step S45: During the cooling process, the temperature distribution of the outer layer, middle layer and inner layer is monitored in real time by temperature sensors installed in each cooling zone of the multi-functional cooling mold, and the flow rate and temperature of the coolant are adjusted by an automatic control system based on the real-time temperature data.

[0035] Optionally, step S4 may be followed by:

[0036] Step S5, Quality Control and Surface Treatment: The dimensions and weather resistance of the molded PVC pipes are tested, defective products are removed, and the surface of the qualified pipes is treated with a self-healing surface treatment and coated with a film containing self-healing nanocapsules to complete the preparation.

[0037] Optionally, step S5 specifically includes:

[0038] Step S51: Use an environmental simulation device and measuring equipment to test the dimensions and weather resistance of the molded PVC pipes, and reject unqualified products.

[0039] Step S52: Prepare self-healing nanocapsules and a polymer substrate. Using the polymer substrate as the film substrate, uniformly disperse the self-healing nanocapsules in the polymer substrate by solution casting to prepare a film containing self-healing nanocapsules. The self-healing nanocapsule components are any one of polymer-based capsules, inorganic-based capsules, composite-based capsules, and multifunctional nanocapsules.

[0040] Step S53: The qualified PVC pipe is uniformly coated with a film containing self-healing nanocapsules using an automatic coating device, and the coating thickness is controlled within the range of 10-50μm.

[0041] Step S54: Dry the coated PVC pipe by using a heating drying device at 80-120°C for 30 minutes.

[0042] Step S55: Perform surface quality inspection on the PVC pipe and use a visual scanning device to inspect the appearance of the coated self-healing nanocapsule film.

[0043] Step S56 involves winding or cutting the PVC pipes that have passed quality inspection, classifying and storing them according to different specifications and lengths to complete the preparation.

[0044] The present invention also provides a weather-resistant PVC pipe, which is manufactured using the weather-resistant PVC pipe molding method described above, wherein the weather-resistant PVC pipe comprises:

[0045] The outer layer contains UV absorbers and waterproof polymers to provide UV protection and water resistance.

[0046] The intermediate layer, which is the main structural layer, is used to provide high mechanical strength and toughness;

[0047] The inner layer contains a waterproof polymer and a low-temperature toughness modifier to enhance waterproof and temperature resistance.

[0048] The surface layer is coated with a thin film containing self-healing nanocapsules to provide the tube with self-healing properties.

[0049] Compared with the prior art, the present invention has the following beneficial effects: First, by weighing the waterproof polymer, ultraviolet absorber, low-temperature toughness modifier, composite crosslinking agent, and self-healing nanocapsule additives, a three-stage mixing process is adopted: First, the waterproof polymer and low-temperature toughness modifier are mixed with the base PVC resin in the raw material pool under low shear force to form a first mixed layer; then, the composite crosslinking agent and the base PVC resin are added to the first mixed layer to form a second mixed layer; finally, the ultraviolet absorber, composite crosslinking agent, and base PVC resin are added to the middle layer mixture under high shear force to form a third mixed layer, ultimately forming an upper and lower three-layer mixture in the raw material pool. The layered mixture is conveyed through a vertical cross-section conveying channel to a multi-layer co-extrusion die for extrusion molding, forming a PVC pipe with a three-layer structure. A multi-functional cooling die is used to rapidly cool the extruded pipe to room temperature, fixing its physical form and completing the molding process. This method, through layered mixing, gives the pipe an optimized three-layer structure, providing UV resistance, waterproofing, and high mechanical strength, while maximizing material utilization and ensuring good bonding between layers and overall material stability. This improves the service life of weather-resistant PVC pipes and their ability to adapt to specific environments. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0051] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0052] Figure 1 This is one of the flowcharts illustrating the molding method of the weather-resistant PVC pipe in this embodiment.

[0053] Figure 2 This is the second schematic diagram of the molding method for weather-resistant PVC pipe in this embodiment one;

[0054] Figure 3 This is the third flowchart illustrating the molding method of the weather-resistant PVC pipe in this embodiment. Detailed Implementation

[0055] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0056] In the description of this invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component positioned centrally in the connection.

[0057] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0058] Example 1:

[0059] Combination Figures 1 to 3 As shown, this embodiment of the invention provides a method for molding weather-resistant PVC pipes, including:

[0060] Step S1: Provide the additives: waterproof polymer, ultraviolet absorber, low-temperature toughness modifier, composite crosslinking agent and self-healing nanocapsules, and weigh each component.

[0061] It should be noted that the first step is to prepare various additives required for the preparation of weather-resistant PVC pipes, including waterproof polymers, ultraviolet absorbers, low-temperature toughness modifiers, composite crosslinking agents, and self-healing nanocapsules. These additives each have different functions, aiming to improve the overall weather resistance of PVC pipes.

[0062] Step S2, three-stage mixing: First, the waterproof polymer, low-temperature toughness modifier, composite crosslinking agent, and base PVC resin are mixed in the raw material pool under low shear force to form a first mixed layer; then, the composite crosslinking agent and base PVC resin are added to the first mixed layer to form a second mixed layer; finally, the ultraviolet absorber, composite crosslinking agent, and base PVC resin are added to the middle mixed layer under high shear force to form a third mixed layer; thus forming a layered mixture with three layers in the raw material pool.

[0063] It should be noted that the mixing process involves three stages, aiming to optimize the distribution and maximize the functionality of each additive. In the preparation of the first mixing layer, low shear force helps prevent component decomposition or performance degradation that may occur under high shear force. In the preparation of the third mixing layer, high shear force helps to uniformly disperse the UV absorber, improving its UV resistance. Ultimately, a layered mixture with a three-layer structure is formed in the entire raw material pool, where the functional components of each layer are concentrated and distributed, ensuring that the PVC pipes possess excellent weather resistance.

[0064] Step S3, Extrusion molding: The layered mixture is conveyed to a multi-layer co-extrusion die through a vertical cross-section conveying channel, and extruded through the multi-layer co-extrusion die to form a three-layer PVC pipe;

[0065] During operation, the speed and pressure of the twin-screw extruder are precisely controlled to ensure uniform extrusion and distinct layers of material. Furthermore, optimized die flow channel design and temperature control further enhance the interlayer bonding and overall structural stability of the pipe. A real-time monitoring system tracks extrusion pressure, temperature, and flow rate to ensure consistent quality and process stability of the molded PVC pipes.

[0066] Step S4, rapid cooling and curing: The extruded PVC pipe is rapidly cooled to room temperature using a multi-functional cooling mold to fix its physical form and obtain the molded PVC pipe.

[0067] The multi-functional cooling mold is equipped with a zoned cooling system, which independently cools the outer, middle and inner layers of the pipe to ensure that each layer of material maintains a stable structure and performance during the cooling process.

[0068] Specific details: The outer layer is rapidly cooled using a high-efficiency circulating coolant (such as cooling water or ethylene glycol solution), with the cooling rate controlled at 10-20℃ / min, to quickly fix the UV absorber and waterproof polymer. The middle layer uses a moderate cooling rate (5-10℃ / min) to ensure that the mechanical strength and toughness of the main structural layers are not affected by rapid cooling. The inner layer uses a low-temperature coolant (such as cooling oil) for slow and uniform cooling, with the cooling rate controlled at 3-7℃ / min, to ensure the stability of the corrosion-resistant marine polymer. Through precise temperature and pressure control, the cooling mold effectively prevents the pipe from warping, shrinking, or deforming during the cooling process, ultimately producing molded PVC pipes with excellent physical properties.

[0069] Step S5, Quality Control and Surface Treatment: The dimensions and weather resistance of the molded PVC pipes are tested, defective products are removed, and the surface of the qualified pipes is treated with a self-healing surface treatment and coated with a film containing self-healing nanocapsules to complete the preparation.

[0070] Comprehensive quality control and surface treatment are carried out on the molded PVC pipes. First, the dimensions and weather resistance of the pipes are tested using precision measuring equipment and environmental simulation devices. Defective products are rejected to ensure that only qualified products proceed to the next process.

[0071] The working principle of this invention is as follows: First, the waterproof polymer, ultraviolet absorber, low-temperature toughness modifier, composite crosslinking agent, and self-healing nanocapsule additives are weighed. Then, a three-stage mixing process is adopted: First, the waterproof polymer and low-temperature toughness modifier are mixed with the base PVC resin in the raw material pool under low shear force to form a first mixed layer; then, the composite crosslinking agent and base PVC resin are added to the first mixed layer to form a second mixed layer; finally, the ultraviolet absorber, composite crosslinking agent, and base PVC resin are added to the middle mixed layer under high shear force to form a third mixed layer, ultimately forming a three-layer mixture in the raw material pool. The material is conveyed through a vertical cross-section conveying channel to a multi-layer co-extrusion die for extrusion molding, forming a PVC pipe with a three-layer structure. The extruded pipe is then rapidly cooled to room temperature using a multi-functional cooling die to fix its physical form and complete the molding process. This method, through layered mixing, gives the pipe an optimized three-layer structure, providing UV resistance, waterproofing, and high mechanical strength, while maximizing material utilization and ensuring good bonding between layers and overall material stability. This improves the service life of weather-resistant PVC pipes and their ability to adapt to specific environments.

[0072] In this embodiment, the waterproof polymer component is specifically described as any one or a combination of polyvinyl alcohol, polyacrylate, polyurethane and polysiloxane, and its content in the first mixed layer is 5-15%; it replaces the traditional plasticizer, has stronger waterproof performance and also has the ability to resist salt spray corrosion.

[0073] The ultraviolet absorber component is any one or a combination of several of phenylbenzotriazole compounds, phenyl ketone compounds, and organic ultraviolet absorbers, and its content in the third mixed layer is 2-8%; it is used to enhance the anti-ultraviolet performance, and the nano-level dispersion improves the ultraviolet blocking effect.

[0074] The low-temperature toughness modifier is composed of any one or a combination of butadiene rubber, ethylene-vinyl acetate copolymer, polyacrylonitrile and polybutadiene, and its content in the first mixed layer is 3-10%; it is used to improve the toughness of PVC pipes in low-temperature environments and prevent brittleness.

[0075] The composite crosslinking agent consists of any one of vulcanizing agents, peroxide crosslinking agents, photoinitiating crosslinking agents, and electron beam crosslinking agents, with a content of 1-5% in the layered mixture. It is used to enhance the crosslinking between PVC chains and improve the overall stability and durability of the material.

[0076] In this embodiment, step S2 specifically includes:

[0077] Step S21: In the raw material pool, add waterproof polymer, low temperature toughness modifier, composite crosslinking agent and base PVC resin in a predetermined ratio, and mix using a twin-screw mixer, adjusting the twin-screw mixer to low shear mode (shear rate controlled at 50-100 s⁻¹).

[0078] Step S22: Set the mixing temperature to 160-180℃ and continue mixing for 10-15 minutes under low shear force to ensure that the waterproof polymer and low-temperature toughness modifier are fully and evenly dispersed with the base PVC resin to form the first mixed layer.

[0079] Temperature control and continuous mixing time ensure uniform distribution of each component, avoiding local overheating or insufficient mixing of materials, thereby improving the quality and stability of the first mixing layer.

[0080] Step S23: Add the composite crosslinking agent and base PVC resin to the raw material pool again according to the predetermined ratio, increase the stirring height of the twin-screw mixer and maintain the low shear force mode, adjust the mixing temperature to maintain at 160-180℃, and mix for another 5-10 minutes under low shear force to make the composite crosslinking agent evenly distributed in the base PVC resin to form a second mixed layer.

[0081] The composite crosslinking agent and base PVC resin are added to the raw material tank again according to the predetermined ratio. Then, the stirring height of the twin-screw mixer is increased, maintaining a low shear force mode while keeping the mixing temperature at 160-180℃, and further mixing is carried out for 5-10 minutes under low shear force. This process ensures that the composite crosslinking agent is uniformly distributed in the base PVC resin, forming a second mixed layer. The uniform distribution of the composite crosslinking agent enhances the crosslinking structure between PVC chains, improving the overall mechanical strength and durability of the material.

[0082] Step S24: Continue to add base PVC resin to the raw material tank, and then gradually add UV absorber and composite crosslinking agent according to the predetermined ratio. Increase the stirring height of the twin-screw mixer and switch the twin-screw mixer to high shear force mode. Adjust the mixing temperature to 170-190℃ and continue mixing under high shear force for 7-12 minutes to ensure that the UV absorber and composite crosslinking agent are evenly dispersed in the base PVC resin to form the third mixture.

[0083] Continue adding base PVC resin to the raw material tank, and gradually add UV absorber and composite crosslinking agent according to the predetermined ratio. Then, increase the stirring height of the twin-screw mixer and switch to high-shear mode (shear rate controlled at 200-300 s⁻¹), while adjusting the mixing temperature to 170-190℃. Continue mixing under high shear for 7-12 minutes to ensure that the UV absorber and composite crosslinking agent are uniformly dispersed in the base PVC resin, forming a third mixed layer. High shear helps to finely disperse the UV absorber, improving its UV resistance and enhancing the weather resistance of the pipe.

[0084] Step S25: Using a layered stacking technique, the first mixing layer, the second mixing layer, and the third mixing layer are stacked sequentially to form a layered mixture with a three-layer structure.

[0085] A layered stacking technique is employed, where a first, second, and third mixed layer are sequentially stacked to form a three-layered mixture. By controlling the thickness and component ratio of each layer, the functional components are ensured to be concentrated in their respective layers, avoiding interference between components in different layers. This layered stacking technique allows UV absorbers, waterproof polymers, and composite crosslinking agents to fully function within their respective layers, enhancing the overall weather resistance of PVC pipes.

[0086] Step S26: Rheological adjustment of the layered mixture is performed, and the overall temperature is stabilized at 175-185℃ using an interlayer temperature regulating device; the viscosity of the layered mixture is monitored in real time using a viscosity monitoring device. If an abnormal viscosity is detected, a corresponding thermal balance adjustment strategy is set, and the thermal balance adjustment strategy is executed by activating the regulation mechanism of the interlayer temperature regulating device.

[0087] The rheological properties of the layered mixture are adjusted, and the overall temperature is stabilized at 175-185℃ using an interlayer temperature control device. Simultaneously, the viscosity of the layered mixture is monitored in real time using a viscosity monitoring device to ensure its suitability for subsequent extrusion molding. When an abnormal viscosity is detected, a corresponding thermal balance adjustment strategy is activated, executed through the adjustment mechanism of the interlayer temperature control device. This process ensures that the layered mixture possesses stable flowability and suitable viscosity when entering the extrusion molding stage, ensuring that each layer of material can smoothly and uniformly pass through the multi-layer co-extrusion die to form a high-quality three-layer PVC pipe.

[0088] In this embodiment, step S3 specifically includes:

[0089] Step S31: The obtained layered mixture is transported from the raw material pool to the inlet of the extrusion molding equipment through a preheated conveying pipe. The conveying channel adopts a vertical cross-section design to ensure that the layers of the layered mixture remain clearly separated during the conveying process.

[0090] It should be noted that the conveying channel adopts a vertical cross-section design to ensure that each layer of the stratified mixture remains clearly separated during the conveying process, avoiding interlayer mixing and thus maintaining the independence and stability of each functional component. This design helps maintain the integrity of the three-layer structure during extrusion, ensuring that the final PVC pipe has the expected multilayer performance.

[0091] Step S32: Select a multi-layer co-extrusion die suitable for the three-layer structure, adjust the temperature control component of the multi-layer co-extrusion die for preheating, and set the die temperature in the range of 200-220℃.

[0092] The preheated mold can quickly heat the layered mixture to a suitable extrusion temperature, promoting the uniform distribution and good adhesion of each layer of material, and ensuring the stable formation of the three-layer structure during the extrusion molding process.

[0093] Step S33: The layered mixture is introduced into the cavity of the multi-layer co-extrusion mold, the extrusion molding equipment is started, the speed and pressure of the extruder are controlled, and a three-layer PVC pipe is extruded.

[0094] The preheated multilayer co-extrusion die is fed into the layered mixture, and the extrusion molding equipment is started. By controlling the speed and pressure of the extruder, it is ensured that the layered mixture is evenly distributed in each layer channel of the die during the extrusion process, forming a PVC pipe with a three-layer structure. During the extrusion process, the control of the twin-screw extruder ensures that the thickness and distribution of each layer of material meet the design requirements, thereby producing high-quality, structurally stable, and weather-resistant PVC pipes.

[0095] In this embodiment, step S4 specifically includes:

[0096] Step S41: The formed three-layer PVC pipe is conveyed to the inlet of the multi-functional cooling mold through the conveying assembly; by adjusting the speed and tension of the conveyor belt, the pipe is ensured to maintain stable and continuous movement when entering the cooling mold.

[0097] Step S42: A zoned cooling system is used to cool the PVC pipe in layers, with independent cooling channels set up for the outer cooling zone, the middle cooling zone, and the inner cooling zone, to ensure that each layer of material can be cooled appropriately according to its characteristics.

[0098] Step S43: The outer layer of the PVC pipe is rapidly cooled by a high-efficiency circulating coolant (such as cooling water or ethylene glycol solution) flowing in the outer cooling channel; the outer cooling rate is controlled at 10-20℃ / minute, and a spray cooling system is used to ensure that the coolant evenly covers the outer surface of the pipe.

[0099] Step S44: After the outer layer is cooled, the PVC pipe is slowly cooled through the intermediate layer cooling channel and the inner layer cooling channel using a preset coolant temperature and flow rate; the intermediate layer cooling rate is controlled at 5-10℃ / minute, and the coolant flow rate is dynamically adjusted by the flow regulating valve.

[0100] Step S45: During the cooling process, the temperature distribution of the outer layer, middle layer and inner layer is monitored in real time by temperature sensors installed in each cooling zone of the multi-functional cooling mold, and the flow rate and temperature of the coolant are adjusted by an automatic control system based on the real-time temperature data.

[0101] In this embodiment, step S5 specifically includes:

[0102] Step S51: Use an environmental simulation device and measuring equipment to test the dimensions and weather resistance of the molded PVC pipes, and reject unqualified products.

[0103] It should be noted that environmental simulation devices and precision measuring equipment are used to test the dimensions and weather resistance of the molded PVC pipes, eliminating substandard products. Specifically, dimensional inspection uses laser measuring instruments to ensure that the pipe diameter and wall thickness meet design specifications; weather resistance testing uses accelerated aging test chambers to simulate harsh environmental conditions and evaluate the pipes' resistance to ultraviolet radiation, salt spray corrosion, and water resistance. This rigorous testing process ensures that only PVC pipes meeting quality standards proceed to subsequent surface treatment stages, improving product consistency and reliability.

[0104] Step S52: Prepare self-healing nanocapsules and a polymer substrate. Using the polymer substrate as the film substrate, uniformly disperse the self-healing nanocapsules in the polymer substrate by solution casting to prepare a film containing self-healing nanocapsules. The self-healing nanocapsule components are any one of polymer-based capsules, inorganic-based capsules, composite-based capsules, and multifunctional nanocapsules.

[0105] It should be noted that the process involves preparing self-healing nanocapsules and a polymer substrate. Using the polymer substrate as the film substrate, the self-healing nanocapsules are uniformly dispersed within the polymer substrate via solution casting to prepare a film containing the self-healing nanocapsules. The self-healing nanocapsule components can be any one or more of polymer-based capsules, inorganic-based capsules, composite-based capsules, or multifunctional nanocapsules to suit different self-healing needs and environmental conditions. The solution casting method, by controlling the solution concentration, casting speed, and drying conditions, ensures the uniform distribution and stable fixation of the nanocapsules in the film, thereby endowing the PVC pipe with excellent self-healing properties.

[0106] Step S53: The qualified PVC pipe is uniformly coated with a film containing self-healing nanocapsules using an automatic coating device, and the coating thickness is controlled within the range of 10-50μm.

[0107] Qualified PVC pipes are uniformly coated with a film containing self-healing nanocapsules using an automated coating device, controlling the coating thickness within the range of 10-50 μm. The automated coating device, through precise coating head design and an intelligent control system, ensures uniform coverage and consistent film thickness. During the coating process, the coating speed and the viscosity of the film solution are adjusted to ensure the smoothness and continuity of the film on the PVC pipe surface, preventing defects such as bubbles, wrinkles, or uneven film formation, thereby improving the appearance quality and self-healing properties of the pipes.

[0108] Step S54: Dry the coated PVC pipe by using a heating drying device at 80-120°C for 30 minutes to ensure the fixation of the film and the stability of the nanocapsules.

[0109] Step S55: Perform surface quality inspection on the PVC pipe and use a visual scanning device to inspect the appearance of the coated self-healing nanocapsule film.

[0110] Surface quality inspection of PVC pipes involves using visual scanning equipment to visually inspect the coated self-healing nanocapsule film. Specifically, the visual scanning equipment uses a camera and image processing software to detect the uniformity, integrity, and defects (such as bubbles, cracks, and film peeling) of the film surface. This automated surface inspection system enables the rapid and accurate identification of substandard pipes.

[0111] Step S56 involves winding or cutting the PVC pipes that have passed quality inspection, classifying and storing them according to different specifications and lengths to complete the preparation.

[0112] The specific operation involves adjusting the length of qualified pipes according to customer needs or standard specifications using automated winding equipment or cutting machines to ensure that each batch of products meets design and usage requirements. Subsequently, an intelligent sorting system categorizes the pipes according to different specifications and lengths, facilitating subsequent packaging, transportation, and storage. The sorted pipes are then transported to the storage area via an automated conveyor system.

[0113] Example 2:

[0114] The present invention also provides a weather-resistant PVC pipe, which is manufactured using the molding method for weather-resistant PVC pipe as described in Example 1. The weather-resistant PVC pipe comprises:

[0115] The outer layer contains UV absorbers and waterproof polymers to provide UV protection and water resistance.

[0116] The intermediate layer, the main structural layer, is used to provide high mechanical strength and toughness.

[0117] The inner layer contains a waterproof polymer and a low-temperature toughness modifier to enhance waterproof and temperature resistance.

[0118] The surface layer is coated with a thin film containing self-healing nanocapsules to provide the tubing with self-healing properties, thereby extending its service life and improving its weather resistance.

[0119] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for molding weather-resistant PVC pipe, characterized in that, include: Step S1: Provide the additives: waterproof polymer, ultraviolet absorber, low-temperature toughness modifier, composite crosslinking agent and self-healing nanocapsules, and weigh each component. Step S2, three-stage mixing: First, the waterproof polymer, low-temperature toughness modifier, composite crosslinking agent and base PVC resin are mixed in the raw material pool under low shear force to form the first mixed layer; the composite crosslinking agent and base PVC resin are added to the first mixed layer to form the second mixed layer; the ultraviolet absorber, composite crosslinking agent and base PVC resin are added to the middle mixed layer under high shear force to form the third mixed layer. To form a three-layered mixture in the raw material pool; specifically including: Step S21: In the raw material pool, add waterproof polymer, low temperature toughness modifier, composite crosslinking agent and base PVC resin in a predetermined ratio, mix using a twin-screw mixer, and adjust the twin-screw mixer to low shear mode. Step S22: Set the mixing temperature to 160-180℃ and continue mixing for 10-15 minutes under low shear force to ensure that the waterproof polymer and low-temperature toughness modifier are fully and evenly dispersed with the base PVC resin to form the first mixed layer. Step S23: Add the composite crosslinking agent and base PVC resin to the raw material pool again according to the predetermined ratio, increase the stirring height of the twin-screw mixer and maintain the low shear force mode, adjust the mixing temperature to maintain at 160-180℃, and mix for 5-10 minutes under low shear force to make the composite crosslinking agent evenly distributed in the base PVC resin to form a second mixed layer. Step S24: Continue to add base PVC resin to the raw material tank, and then gradually add UV absorber and composite crosslinking agent according to the predetermined ratio. Increase the stirring height of the twin-screw mixer and switch the twin-screw mixer to high shear force mode. Adjust the mixing temperature to 170-190℃ and continue mixing under high shear force for 7-12 minutes to ensure that the UV absorber and composite crosslinking agent are evenly dispersed in the base PVC resin to form the third mixture. Step S25: Using a layered stacking technique, the first mixing layer, the second mixing layer, and the third mixing layer are stacked sequentially to form a layered mixture with a three-layer structure. Step S26: Rheological properties of the layered mixture are adjusted, and the overall temperature is stabilized at 175-185℃ using an interlayer temperature regulating device; the viscosity of the layered mixture is monitored in real time using a viscosity monitoring device. If an abnormal viscosity is detected, a corresponding thermal balance adjustment strategy is set, and the thermal balance adjustment strategy is executed by activating the regulation mechanism of the interlayer temperature regulating device. Step S3, Extrusion molding: The layered mixture is conveyed to a multi-layer co-extrusion die through a vertical cross-section conveying channel, and extruded through the multi-layer co-extrusion die to form a three-layer PVC pipe; Step S4, rapid cooling and curing: The extruded PVC pipe is rapidly cooled to room temperature using a multi-functional cooling mold to fix its physical form and obtain the molded PVC pipe. Step S5, Quality Control and Surface Treatment: The dimensions and weather resistance of the molded PVC pipes are tested, defective products are removed, and the surface of the qualified pipes is treated with a self-healing surface treatment and coated with a film containing self-healing nanocapsules to complete the preparation.

2. The molding method for weather-resistant PVC pipe according to claim 1, characterized in that, The waterproof polymer component is any one or a combination of several of polyvinyl alcohol, polyacrylate, polyurethane and polysiloxane, and its content in the first mixed layer is 5-15%; The ultraviolet absorber component is any one or a combination of several of phenylbenzotriazole compounds, phenyl ketone compounds, and organic ultraviolet absorbers, and its content in the third mixed layer is 2-8%; The low-temperature toughness modifier component is any one or a combination of butadiene rubber, ethylene-vinyl acetate copolymer, polyacrylonitrile and polybutadiene, and its content in the first mixed layer is 3-10%; The composite crosslinking agent component is any one of vulcanizing agent, peroxide crosslinking agent, photoinitiating crosslinking agent and electron beam crosslinking agent, and its content in the layered mixture is 1-5%.

3. The molding method for weather-resistant PVC pipe according to claim 1, characterized in that, Step S3 specifically includes: Step S31: The obtained layered mixture is transported from the raw material pool to the inlet of the extrusion molding equipment through a preheated conveying pipe. The conveying channel adopts a vertical cross-section design to ensure that the layers of the layered mixture remain clearly separated during the conveying process. Step S32: Select a multi-layer co-extrusion die suitable for the three-layer structure, adjust the temperature control component of the multi-layer co-extrusion die for preheating, and set the die temperature in the range of 200-220℃. Step S33: The layered mixture is introduced into the cavity of the multi-layer co-extrusion mold, the extrusion molding equipment is started, the speed and pressure of the extruder are controlled, and a three-layer PVC pipe is extruded.

4. The molding method for weather-resistant PVC pipe according to claim 1, characterized in that, Step S4 specifically includes: Step S41: The formed three-layer PVC pipe is conveyed to the inlet of the multi-functional cooling mold through the conveying assembly; Step S42: A zoned cooling system is used to cool the PVC pipes in layers, with independent cooling channels set up for the outer cooling zone, the middle cooling zone, and the inner cooling zone. Step S43: The outer layer of the PVC pipe is rapidly cooled by the high-efficiency circulating coolant flowing in the outer cooling channel.

5. The molding method for weather-resistant PVC pipe according to claim 4, characterized in that, Following step S43, the following is also included: Step S44: After the outer layer is cooled, the PVC pipe is slowly cooled through the intermediate layer cooling channel and the inner layer cooling channel using a preset coolant temperature and flow rate. Step S45: During the cooling process, the temperature distribution of the outer layer, middle layer and inner layer is monitored in real time by temperature sensors installed in each cooling zone of the multi-functional cooling mold, and the flow rate and temperature of the coolant are adjusted by an automatic control system based on the real-time temperature data.

6. The molding method for weather-resistant PVC pipe according to claim 1, characterized in that, Step S5 specifically includes: Step S51: Use an environmental simulation device and measuring equipment to test the dimensions and weather resistance of the molded PVC pipes, and reject unqualified products. Step S52: Prepare self-healing nanocapsules and a polymer substrate. Using the polymer substrate as the film substrate, uniformly disperse the self-healing nanocapsules in the polymer substrate by solution casting to prepare a film containing self-healing nanocapsules. The self-healing nanocapsule components are any one of polymer-based capsules, inorganic-based capsules, composite-based capsules, and multifunctional nanocapsules. Step S53: The qualified PVC pipe is uniformly coated with a film containing self-healing nanocapsules using an automatic coating device, and the coating thickness is controlled within the range of 10-50μm. Step S54: Dry the coated PVC pipe by using a heating drying device at 80-120°C for 30 minutes. Step S55: Perform surface quality inspection on the PVC pipe and use a visual scanning device to inspect the appearance of the coated self-healing nanocapsule film. Step S56 involves winding or cutting the PVC pipes that have passed quality inspection, classifying and storing them according to different specifications and lengths to complete the preparation.

7. A weather-resistant PVC pipe, characterized in that, The weather-resistant PVC pipe is manufactured using the molding method according to any one of claims 1 to 6, wherein the weather-resistant PVC pipe comprises: The outer layer contains UV absorbers and waterproof polymers to provide UV protection and water resistance. The intermediate layer, which is the main structural layer, is used to provide high mechanical strength and toughness; The inner layer contains a waterproof polymer and a low-temperature toughness modifier to enhance waterproof and temperature resistance.

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