Weather-resistant PVC (polyvinyl chloride) pipe and forming method thereof

Abstract

The invention discloses a weather-resistant PVC (polyvinyl chloride) pipe and a forming method thereof, and the forming method is characterized by comprising the following steps: S1, providing additives: a waterproof polymer, an ultraviolet light absorber, a low-temperature toughness modifier, a composite cross-linking agent and a self-healing nanocapsule; s2, performing three-stage mixing to sequentially form a third mixing layer; a layered mixture with upper and lower three layers is formed in the raw material pool; s3, extrusion molding is conducted, specifically, extrusion is conducted through a multi-layer co-extrusion mold, and a PVC pipe of a three-layer structure is formed; s4, rapid cooling and curing are conducted, specifically, cooling is conducted to fix the physical form, and a formed PVC pipe is prepared; through layered mixing, the pipe has an optimized three-layer structure, ultraviolet resistance, water resistance and high mechanical strength are respectively provided, meanwhile, the maximum utilization rate of materials is realized, good combination of the layers and the overall stability of the materials are ensured, the service life of the weather-resistant PVC pipe is prolonged, and the capacity of adapting to specific environments is improved.

Description

Technical Field

[0001] The invention relates to the field of PVC pipes, and in particular to a weather-resistant PVC pipe and a molding method thereof. Background Art

[0002] With the continuous development of infrastructure construction, PVC pipes have been widely used in various application scenarios, especially in environments that need to be exposed to harsh weather conditions for a long time, such as marine coastal infrastructure, underground drainage systems, and outdoor power cable protection. These application scenarios require PVC pipes to have not only excellent mechanical strength and corrosion resistance, but also excellent UV resistance and waterproof performance to ensure its long-term stability and reliability in complex environments. Therefore, the development of a versatile and efficient weather-resistant PVC pipe molding method has become a key technical requirement to improve pipe performance and extend service life.

[0003] In the prior art, in order to achieve the multifunctional weather resistance of PVC pipes, a variety of functional additives (such as waterproof, UV protection, and temperature resistance) are usually evenly dispersed throughout the cross section of the pipe during the preparation process. However, this uniform mixing method has significant disadvantages. First, due to the uniform distribution of each functional additive throughout the material, the content of each additive is limited, making it difficult to achieve the optimal functional enhancement effect. Secondly, too many additives mixed into the base material will significantly reduce the mechanical properties of the PVC pipe, such as toughness and strength, and affect its overall structural stability. Ultimately, these problems lead to limited material utilization, and the comprehensive weather resistance performance fails to achieve the expected effect.

[0004] Therefore, in the existing technology of the molding process of multifunctional weather-resistant PVC pipes, it is difficult to simultaneously take into account the high performance and high utilization rate of the material. 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 object of the present invention is to provide a weather-resistant PVC pipe and a molding method thereof to solve the above technical problems.

[0006] To achieve this object, the present invention adopts the following technical solutions: A method for forming a weather-resistant PVC pipe, comprising: Step S1, providing additives: waterproof polymer, ultraviolet absorber, low temperature toughness modifier, composite cross-linking agent and self-healing nanocapsule, and weighing each component; Step S2, three-stage mixing: firstly, a waterproof polymer, a low temperature toughness modifier, a composite cross-linking agent and a base PVC resin are mixed under low shear force in a raw material pool to form a first mixed layer; the composite cross-linking agent and the base PVC resin are continuously added to the first mixed layer to form a second mixed layer; an ultraviolet absorber, a composite cross-linking agent and a base PVC resin are added to the middle layer mixture under high shear force to form a third mixed layer; so as to form a layered mixture having three layers in the raw material pool; Step S3, extrusion molding: conveying the layered mixture to a multi-layer co-extrusion die through a conveying channel with a vertical cross section, and extruding through the multi-layer co-extrusion die to form a three-layer PVC pipe; Step S4, rapid cooling and solidification: the extruded PVC pipe is rapidly cooled to room temperature by a multifunctional cooling die to fix the physical shape and obtain a formed PVC pipe.

[0007] Optionally, the waterproof polymer component is any one or a combination 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 phenylbenzotriazole compounds, phenylketone 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 a vulcanizing agent, a peroxide crosslinking agent, a photoinitiator crosslinking agent and an electron beam crosslinking agent, and its content in the layered mixture is 1-5%.

[0008] Optionally, the step S2 specifically includes: Step S21, adding a waterproof polymer, a low temperature toughness modifier, a composite cross-linking agent and a base PVC resin in a predetermined ratio into a raw material pool, mixing them using a twin-screw mixer, and adjusting the twin-screw mixer to a low shear force mode; Step S22, setting the mixing temperature at 160-180° C. and continuously mixing for 10-15 minutes under low shear force, so that the waterproof polymer and the low temperature toughness modifier are fully and evenly dispersed with the base PVC resin to form a first mixed layer; Step S23, add the composite cross-linking agent and the base PVC resin to the raw material pool again according to a 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°C, and further mix for 5-10 minutes under low shear force to make the composite cross-linking agent evenly distributed in the base PVC resin to form a second mixed layer.

[0009] Optionally, after step S23, the following steps are further included: Step S24, continue to add the base PVC resin to the raw material pool, and then gradually add the ultraviolet absorber and the composite cross-linking agent according to a predetermined ratio, increase the stirring height of the twin-screw mixer, switch the twin-screw mixer to a high shear force mode, adjust the mixing temperature to 170-190° C., and continue mixing for 7-12 minutes under high shear force to ensure that the ultraviolet absorber and the composite cross-linking agent are evenly dispersed in the base PVC resin to form a third mixture; Step S25, using a layered stacking technique, stacking the first mixed layer, the second mixed layer and the third mixed layer in sequence to form a layered mixture with a three-layer structure; Step S26, adjusting the rheological properties of the layered mixture, using an interlayer temperature regulating device to stabilize the overall temperature at 175-185°C; and monitoring the viscosity of the layered mixture in real time through a viscosity monitoring device. If abnormal viscosity is detected, a corresponding thermal balance adjustment strategy is set, and the thermal balance adjustment strategy is executed by starting the adjustment mechanism of the interlayer temperature regulating device.

[0010] Optionally, the step S3 specifically includes: Step S31, transporting the obtained layered mixture from the raw material pool to the inlet of the extrusion molding device through the preheated conveying pipeline, wherein the conveying channel adopts a vertical cross-section design so that each layer of the layered mixture can be clearly layered during the conveying process; Step S32, selecting a multi-layer co-extrusion die suitable for a three-layer structure, adjusting the temperature control component of the multi-layer co-extrusion die for preheating, and setting the die temperature in the range of 200-220°C; Step S33, introducing the layered mixture into the cavity of the multi-layer co-extrusion mold, starting the extrusion molding equipment, controlling the speed and pressure of the extruder, and extruding to form a three-layer PVC pipe.

[0011] Optionally, the step S4 specifically includes: Step S41, conveying the formed three-layer PVC pipe to the inlet of the multifunctional cooling mold through a conveying assembly; Step S42, using a zoned cooling system to perform layered cooling on the PVC pipe, wherein independent cooling channels are respectively provided in the outer cooling zone, the middle cooling zone, and the inner cooling zone; Step S43, quickly cooling the outer layer of the PVC pipe by means of the high-efficiency circulating coolant flowing in the outer layer cooling channel.

[0012] Optionally, after step S43, the following steps are further included: Step S44, after the outer layer is cooled, the PVC pipe passes through the middle layer cooling channel and the inner layer cooling channel, and the middle layer and the inner layer are slowly cooled using a preset coolant temperature and flow rate; Step S45, during the cooling process, the temperature distribution of the outer layer, the middle layer and the inner layer is monitored in real time by temperature sensors installed in each cooling zone of the multifunctional cooling mold, and the flow rate and temperature of the coolant are adjusted according to the real-time temperature data using an automatic control system.

[0013] Optionally, after step S4, the following steps may be further performed: Step S5, quality control and surface treatment: the size and weather resistance of the formed PVC pipes are tested, unqualified products are removed, and the surfaces of qualified pipes are treated with self-healing surface treatment and coated with a film containing self-healing nanocapsules to complete the preparation.

[0014] Optionally, the step S5 specifically includes: Step S51, using an environmental simulation device and a measuring device to test the size and weather resistance of the formed PVC pipe, and rejecting unqualified products; Step S52, preparing self-healing nanocapsules and a polymer substrate, using the polymer substrate as a film substrate, and uniformly dispersing the self-healing nanocapsules in the polymer substrate by a solution casting method to prepare a film containing self-healing nanocapsules; wherein the self-healing nanocapsule component is any one of a polymer-based capsule, an inorganic-based capsule, a composite-based capsule, and a multifunctional nanocapsule; Step S53, uniformly coating the qualified PVC pipe with a film containing self-healing nanocapsules through an automatic coating device, and controlling the coating thickness to be within the range of 10-50 μm; Step S54, drying the coated PVC pipe by using a heating drying device at 80-120° C. for 30 minutes; Step S55, performing a surface quality inspection on the PVC pipe, and performing an appearance inspection on the coated self-healing nanocapsule film using a visual scanning device; Step S56, winding or cutting the PVC pipes that have passed the quality inspection, and classifying and storing them according to different specifications and lengths to complete the preparation.

[0015] The present invention also provides a weather-resistant PVC pipe, which is made by the above-mentioned forming method of the weather-resistant PVC pipe, and the weather-resistant PVC pipe comprises: an outer layer containing UV absorbers and water-repellent polymers to provide UV resistance and water resistance; The middle layer is the main structural layer, used to provide high mechanical strength and toughness; The inner layer contains a water-repellent polymer and a low-temperature toughness modifier to enhance water-repellent and temperature-resistant properties; The surface layer is coated with a film containing self-healing nanocapsules to provide the self-healing function of the pipe.

[0016] Compared with the prior art, the present invention has the following beneficial effects: first, by weighing the additives of waterproof polymer, ultraviolet absorber, low temperature toughness modifier, composite crosslinking agent and self-healing nanocapsule, a three-stage mixing process is then adopted: first, the waterproof polymer and the low temperature toughness modifier are mixed with the base PVC resin at a low shear force in the raw material pool 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, the composite crosslinking agent and the base PVC resin are added to the middle layer mixture at a high shear force to form a third mixed layer, and finally three upper and lower mixed layers are formed in the raw material pool. The method comprises the following steps: preparing a layered mixture, conveying the layered mixture to a multi-layer co-extrusion die through a conveying channel of a vertical section, performing extrusion molding, and forming a PVC pipe with a three-layer structure. The extruded pipe is quickly cooled to room temperature by a multifunctional cooling die to fix its physical form, thereby completing the molding process. The method provides an optimized three-layer structure through layered mixing, which respectively provides the properties of UV resistance, waterproofness and high mechanical strength, while achieving maximum utilization of materials, ensuring good bonding between layers and overall stability of the material, and improving the service life of the weather-resistant PVC pipe and its ability to adapt to specific environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical contents disclosed by the present invention.

[0019] Figure 1 This is one of the flow diagrams of the method for forming a weather-resistant PVC pipe according to the first embodiment of the present invention; Figure 2 This is a second flow chart of the method for forming a weather-resistant PVC pipe according to the first embodiment of the present invention; Figure 3 This is the third flow chart of the method for forming the weather-resistant PVC pipe of the first embodiment. DETAILED DESCRIPTION

[0020] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be understood that the terms "upper", "lower", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally arranged component at the same time.

[0022] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0023] Embodiment 1: Combination Figures 1 to 3 As shown, an embodiment of the present invention provides a method for forming a weather-resistant PVC pipe, comprising: Step S1, providing additives: waterproof polymer, ultraviolet absorber, low temperature toughness modifier, composite cross-linking agent and self-healing nanocapsule, and weighing each component; It should be noted that first, various additives required for the preparation of weather-resistant PVC pipes are prepared, including waterproof polymers, UV absorbers, low-temperature toughness modifiers, composite cross-linking agents, and self-healing nanocapsules. These additives have different functions and are intended to improve the comprehensive weather resistance of PVC pipes.

[0024] Step S2, three-stage mixing: firstly, a waterproof polymer, a low temperature toughness modifier, a composite cross-linking agent and a base PVC resin are mixed under low shear force in a raw material pool to form a first mixed layer; the composite cross-linking agent and the base PVC resin are continuously added to the first mixed layer to form a second mixed layer; an ultraviolet absorber, a composite cross-linking agent and a base PVC resin are added to the middle layer mixture under high shear force to form a third mixed layer; so as to form a layered mixture having three layers in the raw material pool; It should be noted that the three-stage mixing process is aimed at achieving the optimal distribution and maximum function of each additive. In the preparation of the first mixed layer, low shear force helps prevent component decomposition or performance degradation that may be caused by high shear force; in the preparation of the third mixed layer, high shear force helps to evenly disperse the UV absorber and improve its anti-UV effect. Finally, a layered mixture with a three-layer structure is formed in the entire raw material pool, and the functional components of each layer are concentratedly distributed, ensuring that the PVC pipe has excellent weather resistance.

[0025] Step S3, extrusion molding: conveying the layered mixture to a multi-layer co-extrusion die through a conveying channel with a vertical cross section, and extruding through the multi-layer co-extrusion die to form a three-layer PVC pipe; During the specific operation, the speed and pressure of the twin-screw extruder are precisely controlled to ensure uniform extrusion and clear layers of each layer of material. In addition, by optimizing the flow channel design and temperature control of the mold, the interlayer bonding strength and overall structural stability of the pipe are further improved. The real-time monitoring system during the extrusion process monitors the extrusion pressure, temperature and flow rate to ensure the quality consistency of the molded PVC pipe and the stability of the process.

[0026] Step S4, rapid cooling and solidification: the extruded PVC pipe is rapidly cooled to room temperature by a multifunctional cooling die to fix the physical shape and obtain a formed PVC pipe.

[0027] The multifunctional cooling mold is equipped with a zoned cooling system, which independently cools the outer layer, middle layer and inner layer of the pipe to ensure that each layer of material maintains a stable structure and performance during the cooling process.

[0028] Specific description: The outer layer is cooled quickly with a high-efficiency circulating coolant (such as cooling water or ethylene glycol solution), and the cooling rate is controlled at 10-20℃ / minute to quickly fix the UV absorber and waterproof polymer. The middle layer uses a moderate cooling rate (5-10℃ / minute) to ensure that the mechanical strength and toughness of the main structural layer are not affected by rapid cooling. The inner layer uses a low-temperature coolant (such as cooling oil) for slow and uniform cooling, and the cooling rate is controlled at 3-7℃ / minute to ensure the stability of the anti-corrosion sea defense polymer. Through precise temperature and pressure control, the cooling mold effectively prevents the pipe from warping, shrinking or deforming during the cooling process, and finally produces a molded PVC pipe with excellent physical properties.

[0029] Step S5, quality control and surface treatment: the size and weather resistance of the formed PVC pipes are tested, unqualified products are removed, and the surfaces of qualified pipes are treated with self-healing surface treatment and coated with a film containing self-healing nanocapsules to complete the preparation.

[0030] The finished PVC pipes are subjected to comprehensive quality control and surface treatment. First, the dimensions and weather resistance of the pipes are tested using precision measuring equipment and environmental simulation devices, and unqualified products are eliminated to ensure that only qualified products enter the next process.

[0031] The working principle of the present invention is as follows: first, by weighing the additives of waterproof polymer, ultraviolet absorber, low temperature toughness modifier, composite crosslinking agent and self-healing nanocapsule, a three-stage mixing process is then adopted: first, the waterproof polymer and the low temperature toughness modifier are mixed with the base PVC resin at low shear force in the raw material pool 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, the composite crosslinking agent and the base PVC resin are added to the middle layer mixture at high shear force to form a third mixed layer, and finally the upper and lower three layers of stratified mixing are formed in the raw material pool. The material is conveyed to a multi-layer co-extrusion die through a conveying channel with a vertical section for extrusion molding to form a PVC pipe with a three-layer structure. The extruded pipe is quickly cooled to room temperature by a multifunctional cooling die to fix its physical form to complete the molding process. The method provides an optimized three-layer structure through layered mixing, which respectively provides the performance of UV resistance, waterproofness and high mechanical strength, while achieving maximum utilization of materials, ensuring good bonding between layers and overall stability of the material, and improving the service life of the weather-resistant PVC pipe and its ability to adapt to specific environments.

[0032] In this embodiment, it is specifically described that the waterproof polymer component is 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 takes into account the ability to resist salt spray corrosion.

[0033] The ultraviolet absorber component is any one or a combination 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 nano-scale dispersion improves the ultraviolet blocking effect.

[0034] 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%; it is used to improve the toughness of PVC pipes in low-temperature environments and prevent brittle cracking.

[0035] The composite crosslinking agent component is any one of a vulcanizing agent, a peroxide crosslinking agent, a photoinitiator crosslinking agent and an electron beam crosslinking agent, and its content in the layered mixture is 1-5%, which is used to enhance the crosslinking between PVC chains and improve the stability and durability of the overall material.

[0036] In this embodiment, it is specifically described that step S2 specifically includes: Step S21, in the raw material pool, adding waterproof polymer, low temperature toughness modifier, composite cross-linking agent and base PVC resin according to a predetermined ratio, mixing by a twin-screw mixer, and adjusting the twin-screw mixer to a low shear force mode; (the shear rate is controlled at 50-100 s⁻¹).

[0037] Step S22, setting the mixing temperature at 160-180° C. and continuously mixing for 10-15 minutes under low shear force, so that the waterproof polymer and the low temperature toughness modifier are fully and evenly dispersed with the base PVC resin to form a first mixed layer; Temperature control and continuous mixing time ensure uniform distribution of the components, avoiding local overheating or inadequate mixing of the materials, thus improving the quality and stability of the first mixed layer.

[0038] Step S23, add the composite cross-linking agent and the base PVC resin to the raw material pool again according to a 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°C, and further mix for 5-10 minutes under low shear force to make the composite cross-linking agent evenly distributed in the base PVC resin to form a second mixed layer.

[0039] The composite cross-linking agent and the base PVC resin are added to the raw material pool again in a predetermined ratio. Subsequently, the stirring height of the twin-screw compounder is increased and the low shear force mode is maintained. At the same time, the mixing temperature is maintained at 160-180°C, and further mixed for 5-10 minutes under low shear force. This process ensures that the composite cross-linking agent is evenly distributed in the base PVC resin to form a second mixed layer. The uniform distribution of the composite cross-linking agent strengthens the cross-linking structure between PVC chains and improves the overall mechanical strength and durability of the material.

[0040] Step S24, continue to add the base PVC resin to the raw material pool, and then gradually add the ultraviolet absorber and the composite cross-linking agent according to a predetermined ratio, increase the stirring height of the twin-screw mixer, switch the twin-screw mixer to a high shear force mode, adjust the mixing temperature to 170-190° C., and continue mixing for 7-12 minutes under high shear force to ensure that the ultraviolet absorber and the composite cross-linking agent are evenly dispersed in the base PVC resin to form a third mixture; Continue to add the base PVC resin to the raw material pool, and gradually add the UV absorber and the composite cross-linking agent in a predetermined ratio. Then, increase the stirring height of the twin-screw mixer and switch to the high shear mode (shear rate is 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 the composite cross-linking agent can be evenly dispersed in the base PVC resin to form a third mixed layer. High shear helps to finely disperse the UV absorber, improve its UV resistance, and enhance the weather resistance of the pipe.

[0041] Step S25, using a layered stacking technique, stacking the first mixed layer, the second mixed layer and the third mixed layer in sequence to form a layered mixture with a three-layer structure; The layered stacking technology is used to stack the first mixed layer, the second mixed layer and the third mixed layer in order to form a layered mixture with a three-layer structure. By controlling the thickness and component ratio of each layer, it is ensured that each functional component is concentrated in the corresponding layer to avoid mutual interference between components in different layers. This layered stacking technology allows the ultraviolet absorber, waterproof polymer and composite cross-linking agent to fully play their role in their respective layers, thereby improving the comprehensive weather resistance of PVC pipes.

[0042] Step S26, rheological adjustment is performed on the layered mixture, and the overall temperature is stabilized at 175-185°C by using an interlayer temperature adjustment device; and the viscosity of the layered mixture is monitored in real time by a viscosity monitoring device. If abnormal viscosity is detected, a corresponding thermal balance adjustment strategy is set, and the thermal balance adjustment strategy is executed by starting the adjustment mechanism of the interlayer temperature adjustment device.

[0043] The rheological properties of the layered mixture are adjusted, and the overall temperature is stabilized at 175-185°C using an interlayer temperature regulating device. At the same time, the viscosity of the layered mixture is monitored in real time by a viscosity monitoring device to ensure that it is suitable for the subsequent extrusion molding process. When an abnormal viscosity is detected, the corresponding thermal balance adjustment strategy is activated, and the thermal balance adjustment strategy is executed by activating the adjustment mechanism of the interlayer temperature regulating device. This process ensures that the layered mixture has stable fluidity and suitable viscosity when entering the extrusion molding stage, ensuring that each layer of material can pass through the multi-layer co-extrusion die smoothly and evenly to form a high-quality three-layer structure PVC pipe.

[0044] In this embodiment, it is specifically described that step S3 specifically includes: Step S31, transporting the obtained layered mixture from the raw material pool to the inlet of the extrusion molding device through the preheated conveying pipeline, wherein the conveying channel adopts a vertical cross-section design so that each layer of the layered mixture can be clearly layered during the conveying process; It should be noted that the conveying channel adopts a vertical cross-section design to ensure that the layers of the layered mixture remain clearly layered during the conveying process, avoiding interlayer mixing, thereby maintaining the independence and stability of each functional component. This design helps to maintain the integrity of the three-layer structure during the extrusion process and ensure that the final PVC pipe has the expected multi-layer performance.

[0045] Step S32, selecting a multi-layer co-extrusion die suitable for a three-layer structure, adjusting the temperature control component of the multi-layer co-extrusion die for preheating, and setting the die temperature in the range of 200-220°C; The preheated die can quickly heat the layered mixture to a suitable extrusion temperature, promote the uniform distribution and good bonding of each layer of material, and ensure the stable formation of the three-layer structure during the extrusion molding process.

[0046] Step S33, introducing the layered mixture into the cavity of the multi-layer co-extrusion mold, starting the extrusion molding equipment, controlling the speed and pressure of the extruder, and extruding to form a three-layer PVC pipe.

[0047] The preheated multi-layer co-extrusion die is introduced into the layered mixture and the extrusion molding equipment is started. By controlling the speed and pressure of the extruder, the layered mixture is evenly distributed in the channels of each layer of the die during the extrusion process to form a PVC pipe with a three-layer structure. During the extrusion process, the control of the twin-screw extruder can ensure that the thickness and distribution of each layer of material meet the design requirements, thereby producing high-quality, structurally stable weather-resistant PVC pipes.

[0048] In this embodiment, it is specifically described that step S4 specifically includes: Step S41, conveying the formed three-layer PVC pipe to the entrance of the multifunctional cooling mold through the conveying assembly; by adjusting the speed and tension of the conveyor belt, ensuring that the pipe maintains stable and continuous movement when entering the cooling mold.

[0049] Step S42, using a zoned cooling system to perform layered cooling on the PVC pipe, wherein independent cooling channels are provided in the outer cooling zone, the middle cooling zone and the inner cooling zone respectively; to ensure that each layer of material can be properly cooled according to its characteristics.

[0050] Step S43, quickly cool the outer layer of the PVC pipe by flowing a high-efficiency circulating coolant (such as cooling water or ethylene glycol solution) in the outer cooling channel; control the outer layer cooling rate at 10-20°C / minute, and use a spray cooling system to ensure that the coolant evenly covers the outer surface of the pipe.

[0051] Step S44, after the outer layer is cooled, the PVC pipe passes through the middle layer cooling channel and the inner layer cooling channel, and the middle layer and the inner layer are slowly cooled using the preset coolant temperature and flow rate; the middle layer cooling rate is controlled at 5-10°C / minute, and the coolant flow is dynamically adjusted through the flow regulating valve.

[0052] Step S45, during the cooling process, the temperature distribution of the outer layer, the middle layer and the inner layer is monitored in real time by temperature sensors installed in each cooling zone of the multifunctional cooling mold, and the flow rate and temperature of the coolant are adjusted according to the real-time temperature data using an automatic control system.

[0053] In this embodiment, it is specifically described that step S5 specifically includes: Step S51, using an environmental simulation device and a measuring device to test the size and weather resistance of the formed PVC pipe, and rejecting unqualified products; It should be noted that environmental simulation devices and precision measuring equipment are used to test the size and weather resistance of the formed PVC pipes to eliminate unqualified products. Specifically, the size test uses laser measuring instruments to ensure that the diameter and wall thickness of the pipe meet the design specifications; the weather resistance test uses an accelerated aging test chamber to simulate harsh environmental conditions and evaluate the pipe's UV resistance, salt spray corrosion resistance and waterproof performance. Through a strict testing process, it is ensured that only PVC pipes that meet quality standards enter the subsequent surface treatment process, improving product consistency and reliability.

[0054] Step S52, preparing self-healing nanocapsules and a polymer substrate, using the polymer substrate as a film substrate, and uniformly dispersing the self-healing nanocapsules in the polymer substrate by a solution casting method to prepare a film containing self-healing nanocapsules; wherein the self-healing nanocapsule component is any one of a polymer-based capsule, an inorganic-based capsule, a composite-based capsule, and a multifunctional nanocapsule; It should be noted that self-healing nanocapsules and polymer substrates are prepared, and the polymer substrate is used as a film substrate. The self-healing nanocapsules are evenly dispersed in the polymer substrate by a solution casting method to prepare a film containing self-healing nanocapsules. Among them, the self-healing nanocapsule components can be selected from any one or more of polymer-based capsules, inorganic-based capsules, composite-based capsules or multifunctional nanocapsules to adapt to different self-healing requirements and environmental conditions. The solution casting method ensures the uniform distribution and stable fixation of the nanocapsules in the film by controlling the solution concentration, casting speed and drying conditions, thereby giving the PVC pipe excellent self-healing function.

[0055] Step S53, uniformly coating the qualified PVC pipe with a film containing self-healing nanocapsules through an automatic coating device, and controlling the coating thickness to be within the range of 10-50 μm; The qualified PVC pipe is evenly coated with a film containing self-healing nanocapsules through an automatic coating device, and the coating thickness is controlled within the range of 10-50μm. The automatic coating device ensures uniform coverage and consistent thickness of the film through precise coating head design and intelligent control system. During the coating process, the coating speed and the viscosity of the film solution are adjusted to ensure the flatness and continuity of the film on the surface of the PVC pipe, prevent the occurrence of bubbles, wrinkles or uneven film defects, thereby improving the appearance quality and self-healing performance of the pipe.

[0056] Step S54, drying the coated PVC pipe 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.

[0057] Step S55, performing a surface quality inspection on the PVC pipe, and performing an appearance inspection on the coated self-healing nanocapsule film using a visual scanning device; The surface quality of PVC pipes is checked, and the appearance of the coated self-healing nanocapsule film is inspected using visual scanning equipment. Specifically, the visual scanning equipment detects the uniformity, integrity and defects (such as bubbles, cracks, film shedding, etc.) of the film surface through a camera and image processing software. The automated surface inspection system can quickly and accurately identify unqualified pipes.

[0058] Step S56, winding or cutting the PVC pipes that have passed the quality inspection, and classifying and storing them according to different specifications and lengths to complete the preparation.

[0059] The specific operation includes adjusting the qualified pipes to the appropriate length according to customer needs or standard specifications through automatic winding equipment or cutting machines to ensure that each batch of products meets the design and use requirements. Subsequently, the intelligent classification system is used to classify the pipes according to different specifications and lengths to facilitate subsequent packaging, transportation and storage. The classified pipes are transported to the storage area through an automatic conveying system.

[0060] Embodiment 2: The present invention further provides a weather-resistant PVC pipe, which is made by the molding method of the weather-resistant PVC pipe in the first embodiment. The weather-resistant PVC pipe comprises: The outer layer contains UV absorbers and water-repellent polymers to provide UV and water resistance.

[0061] The middle layer is the main structural layer and is used to provide high mechanical strength and toughness.

[0062] The inner layer contains a water-repellent polymer and a low-temperature toughness modifier to enhance waterproof and temperature resistance.

[0063] The surface layer is coated with a film containing self-healing nanocapsules to provide the pipe with self-healing function to extend the service life and improve weather resistance.

[0064] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for forming a weather-resistant PVC pipe, characterized in that: include: Step S1, providing additives: waterproof polymer, ultraviolet absorber, low temperature toughness modifier, composite cross-linking agent and self-healing nanocapsule, and weighing each component; Step S2, three-stage mixing: firstly, a waterproof polymer, a low temperature toughness modifier, a composite cross-linking agent and a base PVC resin are mixed under low shear force in a raw material pool to form a first mixed layer; the composite cross-linking agent and the base PVC resin are continuously added to the first mixed layer to form a second mixed layer; an ultraviolet absorber, a composite cross-linking agent and a base PVC resin are added to the middle layer mixture under high shear force to form a third mixed layer; so as to form a layered mixture having three layers in the raw material pool; Step S3, extrusion molding: conveying the layered mixture to a multi-layer co-extrusion die through a conveying channel with a vertical cross section, and extruding through the multi-layer co-extrusion die to form a three-layer PVC pipe; Step S4, rapid cooling and solidification: the extruded PVC pipe is rapidly cooled to room temperature by a multifunctional cooling die to fix the physical shape and obtain a formed PVC pipe.

2. The method for forming a weather-resistant PVC pipe according to claim 1, characterized in that: The waterproof polymer component is any one or a combination 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 phenylbenzotriazole compounds, phenylketone 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 a vulcanizing agent, a peroxide crosslinking agent, a photoinitiator crosslinking agent and an electron beam crosslinking agent, and its content in the layered mixture is 1-5%.

3. The method for forming a weather-resistant PVC pipe according to claim 1, characterized in that: The step S2 specifically includes: Step S21, adding a waterproof polymer, a low temperature toughness modifier, a composite cross-linking agent and a base PVC resin in a predetermined ratio into a raw material pool, mixing them using a twin-screw mixer, and adjusting the twin-screw mixer to a low shear force mode; Step S22, setting the mixing temperature at 160-180° C. and continuously mixing for 10-15 minutes under low shear force, so that the waterproof polymer and the low temperature toughness modifier are fully and evenly dispersed with the base PVC resin to form a first mixed layer; Step S23, add the composite cross-linking agent and the base PVC resin to the raw material pool again according to a 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°C, and further mix for 5-10 minutes under low shear force to make the composite cross-linking agent evenly distributed in the base PVC resin to form a second mixed layer.

4. The method for forming a weather-resistant PVC pipe according to claim 3, characterized in that: After step S23, the following steps are also included: Step S24, continue to add the base PVC resin to the raw material pool, and then gradually add the ultraviolet absorber and the composite cross-linking agent according to a predetermined ratio, increase the stirring height of the twin-screw mixer, switch the twin-screw mixer to the high shear force mode, adjust the mixing temperature to 170-190° C., and continue mixing for 7-12 minutes under high shear force to ensure that the ultraviolet absorber and the composite cross-linking agent are evenly dispersed in the base PVC resin to form a third mixture; Step S25, using a layered stacking technique, stacking the first mixed layer, the second mixed layer and the third mixed layer in sequence to form a layered mixture with a three-layer structure; Step S26, adjusting the rheological properties of the layered mixture, using an interlayer temperature regulating device to stabilize the overall temperature at 175-185°C; and monitoring the viscosity of the layered mixture in real time through a viscosity monitoring device. If abnormal viscosity is detected, a corresponding thermal balance adjustment strategy is set, and the thermal balance adjustment strategy is executed by starting the adjustment mechanism of the interlayer temperature regulating device.

5. The method for forming a weather-resistant PVC pipe according to claim 1, characterized in that: The step S3 specifically includes: Step S31, transporting the obtained layered mixture from the raw material pool to the inlet of the extrusion molding device through the preheated conveying pipeline, wherein the conveying channel adopts a vertical cross-section design so that each layer of the layered mixture can be clearly layered during the conveying process; Step S32, selecting a multi-layer co-extrusion die suitable for a three-layer structure, adjusting the temperature control component of the multi-layer co-extrusion die for preheating, and setting the die temperature in the range of 200-220°C; Step S33, introducing the layered mixture into the cavity of the multi-layer co-extrusion mold, starting the extrusion molding equipment, controlling the speed and pressure of the extruder, and extruding to form a three-layer PVC pipe.

6. The method for forming a weather-resistant PVC pipe according to claim 1, characterized in that: The step S4 specifically includes: Step S41, conveying the formed three-layer PVC pipe to the inlet of the multifunctional cooling mold through a conveying assembly; Step S42, using a zoned cooling system to perform layered cooling on the PVC pipe, wherein independent cooling channels are respectively provided in the outer cooling zone, the middle cooling zone, and the inner cooling zone; Step S43, quickly cooling the outer layer of the PVC pipe by means of the high-efficiency circulating coolant flowing in the outer layer cooling channel.

7. The method for forming a weather-resistant PVC pipe according to claim 6, characterized in that: After step S43, the following steps are further included: Step S44, after the outer layer is cooled, the PVC pipe passes through the middle layer cooling channel and the inner layer cooling channel, and the middle layer and the inner layer are slowly cooled using a preset coolant temperature and flow rate; Step S45, during the cooling process, the temperature distribution of the outer layer, the middle layer and the inner layer is monitored in real time by temperature sensors installed in each cooling zone of the multifunctional cooling mold, and the flow rate and temperature of the coolant are adjusted according to the real-time temperature data using an automatic control system.

8. The method for forming a weather-resistant PVC pipe according to claim 1, characterized in that: After step S4, the following steps are also included: Step S5, quality control and surface treatment: the size and weather resistance of the formed PVC pipes are tested, unqualified products are removed, and the surfaces of qualified pipes are treated with self-healing surface treatment and coated with a film containing self-healing nanocapsules to complete the preparation.

9. The method for forming a weather-resistant PVC pipe according to claim 1, characterized in that: The step S5 specifically includes: Step S51, using an environmental simulation device and a measuring device to test the size and weather resistance of the formed PVC pipe, and rejecting unqualified products; Step S52, preparing self-healing nanocapsules and a polymer substrate, using the polymer substrate as a film substrate, and uniformly dispersing the self-healing nanocapsules in the polymer substrate by a solution casting method to prepare a film containing self-healing nanocapsules; wherein the self-healing nanocapsule component is any one of a polymer-based capsule, an inorganic-based capsule, a composite-based capsule, and a multifunctional nanocapsule; Step S53, uniformly coating the qualified PVC pipe with a film containing self-healing nanocapsules through an automatic coating device, and controlling the coating thickness to be within the range of 10-50 μm; Step S54, drying the coated PVC pipe by using a heating drying device at 80-120° C. for 30 minutes; Step S55, performing a surface quality inspection on the PVC pipe, and performing an appearance inspection on the coated self-healing nanocapsule film using a visual scanning device; Step S56, winding or cutting the PVC pipes that have passed the quality inspection, and classifying and storing them according to different specifications and lengths to complete the preparation.

10. A weather-resistant PVC pipe, characterized in that: The weather-resistant PVC pipe is manufactured by the molding method of any one of claims 1 to 9, wherein the weather-resistant PVC pipe comprises: an outer layer containing UV absorbers and water-repellent polymers to provide UV resistance and water resistance; The middle layer is the main structural layer, used to provide high mechanical strength and toughness; The inner layer contains a water-repellent polymer and a low-temperature toughness modifier to enhance water-repellent and temperature-resistant properties; The surface layer is coated with a film containing self-healing nanocapsules to provide the self-healing function of the pipe.

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