System for manufacturing peroxide cross-linked polyethylene pipes

Abstract

The present invention relates to the technical field of manufacturing peroxide-cross-linked polyethylene pipes, and discloses a system for manufacturing peroxide-cross-linked polyethylene pipes. The system comprises: an extruder for extruding and forming pipes; a cross-linking furnace, located on one side of the extruder, having a cross-linking chamber with front and rear openings through which the pipes pass and undergo a cross-linking reaction; and a first microwave generator, located between the extruder and the cross-linking furnace, having a first activation chamber through which the pipes pass. The microwaves generated by the first microwave generator act on the pipes via the first activation chamber. This structure of the present invention ensures a more uniform cross-linking reaction and improves the quality of the pipes.

Description

Technical Field

[0001] The invention relates to the technical field of manufacturing peroxide cross-linked polyethylene pipes, in particular to a system for manufacturing peroxide cross-linked polyethylene pipes. Background Art

[0002] During the cross-linking reaction of peroxide-cross-linked polyethylene pipe, the pipe wall structure has a certain thickness, which limits the infrared penetration performance and the cross-linking reaction of the inner layer of the pipe is insufficient. This condition creates a significant difference in the degree of cross-linking between the inner and outer layers of the pipe, which has a significant negative impact on the overall performance of the pipe and the stability of product quality. Summary of the Invention

[0003] The purpose of the present invention is to provide a system for manufacturing peroxide cross-linked polyethylene pipes, which can make the cross-linking reaction more uniform and improve the quality of the pipes.

[0004] To achieve the above object, the present invention provides a system for manufacturing peroxide cross-linked polyethylene pipes, comprising:

[0005] An extruder, which is used for extruding pipes;

[0006] a cross-linking furnace having a cross-linking chamber with front and rear openings, wherein the cross-linking chamber is used for the pipe to pass through and undergo a cross-linking reaction;

[0007] A first microwave generator is arranged between the extruder and the inlet of the cross-linking furnace. The first microwave generator has a first activation cavity for the tube to pass through. The microwaves generated by the first microwave generator act on the tube through the first activation cavity to activate the tube.

[0008] In some embodiments of the present invention, the system for manufacturing peroxide cross-linked polyethylene pipe further comprises:

[0009] A second microwave generator is disposed at the outlet of the cross-linking furnace. The second microwave generator has a second activation cavity for the tube to pass through. The microwaves generated by the second microwave generator act on the tube through the second activation cavity, causing the unreacted groups or cross-linking points inside the tube to continue to react. In some embodiments of the present invention:

[0010] The structure of the first microwave generator is the same as that of the second microwave generator.

[0011] In some embodiments of the present invention:

[0012] The microwaves generated by the first microwave generator have a frequency range of 2.4 GHz to 2.5 GHz and a power range of 0.5 kW to 2 kW.

[0013] In some embodiments of the present invention:

[0014] The first microwave generator includes a cabinet, a resonant mechanism and a magnetron. The resonant mechanism and the magnetron are arranged inside the cabinet. The resonant mechanism has a shell that forms a resonant cavity. The shell also forms the first activation cavity in the shape of a through hole. The magnetron is arranged around the cavity wall of the first activation cavity.

[0015] In some embodiments of the present invention:

[0016] In some embodiments of the present invention:

[0017] A reflective surface is provided on the cavity wall of the first activation cavity, and the reflective surface is at least a portion of the cavity wall of the first activation cavity.

[0018] In some embodiments of the present invention:

[0019] The first microwave generator further includes a cooling tube. A through hole is provided on the resonant mechanism. At least a portion of the cooling tube extends into the through hole and communicates with the first activation cavity. The cooling medium of the cooling tube is protective gas.

[0020] In some embodiments of the present invention:

[0021] The cross-linking furnace has an infrared emitter, and the infrared rays emitted by the infrared emitter are emitted into the cross-linking chamber. The cross-linking chamber includes a first chamber, a second chamber, and a third chamber arranged in sequence along the movement direction of the pipe. The wavelength of the infrared rays emitted by the infrared emitter into the first chamber is within a first frequency band, the wavelength of the infrared rays emitted by the infrared emitter into the second chamber is within a second frequency band, and the wavelength of the infrared rays emitted by the infrared emitter into the third chamber is within a third frequency band. The first frequency band is greater than the second frequency band, the second frequency band is greater than the third frequency band, and the first frequency band, the second frequency band, and the third frequency band do not overlap with each other.

[0022] In some embodiments of the present invention:

[0023] The extruder has a first nozzle for introducing a protective gas into the inner hole of the pipe;

[0024] The cross-linking furnace has a second nozzle for introducing protective gas into the cross-linking chamber, and the gas outlet direction of the second nozzle is arranged along the radial direction of the pipe.

[0025] In some embodiments of the present invention, the system for manufacturing peroxide cross-linked polyethylene pipe further comprises:

[0026] A cooling water tank, an infrared spectrometer and a traction machine are sequentially arranged along the moving direction of the pipe extruded by the extruder, and the cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipes, the cooling water tank, the infrared spectrometer and the traction machine are sequentially arranged.

[0027] The present invention provides a system for manufacturing peroxide cross-linked polyethylene pipes. Compared with the prior art, the system has the following advantages:

[0028] The system for manufacturing peroxide-crosslinked polyethylene pipes of the present invention includes an extruder, a crosslinking furnace, and a first microwave generator. Before entering the crosslinking furnace for the crosslinking reaction, the pipe from the extruder is first activated by microwaves generated by the first microwave generator using a non-thermal effect. This destroys the polyethylene crystalline regions and promotes uniform dispersion of the peroxide within the pipe. Activating the pipe before the crosslinking reaction, followed by the crosslinking reaction, allows for a more complete crosslinking reaction in both the inner and outer layers of the pipe, resulting in a more uniform crosslinking reaction and improved pipe quality. Furthermore, the crosslinking reaction time is shortened, increasing the efficiency of the reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of a system for manufacturing peroxide cross-linked polyethylene pipes according to an embodiment of the present invention.

[0030] Figure 2 Schematic diagram of a first microwave generator according to an embodiment of the present invention.

[0031] Figure 3 It is a schematic diagram of the interior of the first microwave generator according to an embodiment of the present invention.

[0032] Figure 4 It is a structural schematic diagram of the resonance mechanism and cooling tube according to an embodiment of the present invention.

[0033] Figure 5 It is a schematic structural diagram of a cooling pipe according to an embodiment of the present invention.

[0034] Figure 6 Schematic diagram of a cross-linking furnace according to an embodiment of the present invention.

[0035] Figure 7 It is a cross-sectional view of the first furnace body according to an embodiment of the present invention.

[0036] In the figure, 100, cross-linking furnace; 200, extruder; 300, first microwave generator; 400, second microwave generator; 500, cooling water tank; 600, infrared spectrometer; 700, traction machine; 800, pipe cutting machine; 120, first furnace body; 130, second furnace body; 140, third furnace body; 150, second nozzle; 310, first activation chamber; 320, cabinet; 330, resonant mechanism; 340, magnetron; 350, shell; 360, cooling pipe; 311, reflecting surface. DETAILED DESCRIPTION

[0037] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0038] In the description of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0040] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0041] For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] A system for manufacturing a peroxide cross-linked polyethylene pipe according to a preferred embodiment of the present invention includes: an extruder 200 , a cross-linking furnace 100 , and a first microwave generator 300 .

[0043] The extruder 200 is used for extruding a pipe.

[0044] The cross-linking furnace 100 is disposed on one side of the extruder 200 . The cross-linking furnace 100 has a cross-linking cavity with front and rear openings. The cross-linking cavity is used for allowing the pipe to pass through and undergo a cross-linking reaction.

[0045] The first microwave generator 300 is disposed between the extruder 200 and the entrance of the cross-linking furnace 100. The first microwave generator 300 has a first activation cavity 310 for the pipe to pass through. The microwaves generated by the first microwave generator 300 act on the pipe through the first activation cavity 310 to activate the pipe.

[0046] After being extruded through extruder 200, the pipe enters the first activation chamber 310 of the first microwave generator 300. Microwaves act on the pipe, non-thermally activating the peroxide-containing pipe embryo. This disrupts the molecular chain arrangement in the polyethylene crystalline region, loosens the molecular chains, makes them more active, and enhances their mobility. This promotes uniform dispersion of the peroxide within the pipe, activating the pipe before the crosslinking reaction and preparing it for the subsequent crosslinking reaction. The pipe then enters the crosslinking furnace 100 for a crosslinking reaction, ensuring a more complete crosslinking reaction within the pipe and a more uniform crosslinking reaction between the inner and outer layers, improving pipe quality. This also shortens the crosslinking reaction time, improves crosslinking efficiency, reduces the pipe's crystallinity, and mitigates uneven crosslinking caused by blockage in the polyethylene crystalline region.

[0047] In some embodiments, the system for manufacturing peroxide-cross-linked polyethylene pipes further includes a second microwave generator 400. The second microwave generator 400 is disposed on a side of the cross-linking furnace 100 away from the first microwave generator 300 and is also located on the exit side of the cross-linking furnace 100. The second microwave generator 400 has a second activation cavity for the pipe to pass through. The microwaves generated by the second microwave generator 400 act on the pipe through the second activation cavity, causing the unreacted groups or cross-linking points inside the pipe to continue to react.

[0048] After the pipe undergoes the cross-linking reaction in the cross-linking furnace 100, it enters the second activation chamber of the second microwave generator 400. Microwaves act on the pipe. The action of microwaves can cause the unreacted groups or cross-linking points inside the pipe to continue to react, making the cross-linking structure more uniform and complete, thereby improving the performance of the pipe.

[0049] The microwaves generated by the first microwave generator 300 have a frequency range of 2.4 GHz to 2.5 GHz and a power range of 0.5 kW to 2 kW. Within this parameter range, microwaves accelerate the thermal motion of molecules within the tube, promoting the rearrangement and orientation of molecular chains. Furthermore, the resulting localized high-temperature microenvironment helps activate potential chemical reaction sites, significantly increasing the degree of activation of the tube and thus effectively activating the tube.

[0050] If the microwave frequency is lower than 2.4 GHz, the pipe's absorption rate of microwave energy will decrease, resulting in poor activation. If the microwave frequency is higher than 2.5 GHz, the microwave's ability to penetrate the pipe decreases, and the microwave energy is concentrated on the outer layer of the pipe, resulting in a large temperature difference between the inside and outside of the pipe, which will exacerbate uneven cross-linking.

[0051] If the microwave power is less than 0.5kW, the microwave energy is insufficient to destroy the polyethylene crystallization region, resulting in uneven dispersion of the peroxide and uneven crosslinking reaction inside and outside the pipe. If the microwave power is higher than 2kW, the pipe will have a significant localized thermal effect, causing the temperature of the inner layer of the pipe to rise sharply, causing premature decomposition of the peroxide and reducing crosslinking efficiency.

[0052] In this embodiment, the structure of the first microwave generator 300 is the same as that of the second microwave generator 400. The specific structure is described below by taking the first microwave generator 300 as an example.

[0053] The first microwave generator 300 includes a cabinet 320, a resonant mechanism 330 and a magnetron 340. The resonant mechanism 330 and the magnetron 340 are arranged inside the cabinet 320. The resonant mechanism 330 has a shell 350 that forms a resonant cavity. The shell 350 also forms a through-hole-shaped first activation cavity 310. The magnetron 340 is arranged around the cavity wall of the first activation cavity 310.

[0054] The magnetron 340 can generate microwaves. The resonant mechanism 330 selects and maintains microwaves generated by the magnetron 340 at a specific frequency, so that the microwaves of the required frequency act on the pipe in the first activation cavity 310 to activate the pipe.

[0055] The magnetron 340 and the resonance mechanism 330 are prior art and are not described in detail here.

[0056] A reflective surface 311 is provided on the wall of the first activation chamber 310 . The reflective surface 311 surrounds the tube passing through the first activation chamber 310 . The reflective surface 311 is at least a portion of the wall of the first activation chamber 310 .

[0057] In this embodiment, the reflective surface 311 is formed by the inner wall of the first activation cavity 310. At least a portion of the microwaves are reflected by the reflective surface 311 and act on the tube. The reflective surface 311 is a silver-plated layer on stainless steel, which allows the microwaves to penetrate the tube more evenly.

[0058] The first microwave generator 300 further includes a cooling tube 360 ​​. The cooling tube 360 ​​is connected to the first activation cavity 310 . The cooling medium of the cooling tube 360 ​​is a protective gas.

[0059] In this embodiment, the protective gas is carbon dioxide gas. In other embodiments, other gases such as nitrogen can also be used as the protective gas.

[0060] The resonant mechanism 330 is provided with a through hole, and the cooling pipe 360 ​​is inserted into the through hole and extends into the first activation cavity 310 to introduce protective gas into the first activation cavity 310. The protective gas can protect the surface of the pipe and cool the resonant mechanism 330.

[0061] The first microwave generator 300 further includes a heat insulating layer disposed outside the resonance mechanism 330 . The heat insulating layer may be in a plate shape and surround the resonance mechanism 330 therein.

[0062] Cabinet 320 is equipped with a double-layer aluminum-magnesium alloy shielding net to prevent electromagnetic leakage.

[0063] In some embodiments, the cross-linking furnace 100 includes an infrared emitter. Infrared light emitted by the infrared emitter is directed into a cross-linking chamber, which includes a first chamber, a second chamber, and a third chamber sequentially arranged along the direction of movement of the tubing. The infrared light emitted by the infrared emitter into the first chamber has a wavelength within a first frequency band, the infrared light emitted into the second chamber has a wavelength within a second frequency band, and the infrared light emitted into the third chamber has a wavelength within a third frequency band. The first frequency band is greater than the second frequency band, and the second frequency band is greater than the third frequency band. The first, second, and third frequency bands do not overlap. The first frequency band can be set to long wave, the second frequency band can be set to medium wave, and the third frequency band can be set to short wave.

[0064] The wavelength of the infrared ray emitted by the infrared emitter into the first cavity is greater than the wavelength of the infrared ray emitted into the second cavity, and the wavelength of the infrared ray emitted by the infrared emitter into the second cavity is greater than the wavelength of the infrared ray emitted into the third cavity.

[0065] The infrared emitters may be infrared lamps respectively disposed in the first cavity, the second cavity and the third cavity.

[0066] The cross-linking furnace 100 is provided with three furnace bodies. A first cavity is provided in the first furnace body 120 , a second cavity is provided in the second furnace body 130 , and a third cavity is provided in the third furnace body 140 .

[0067] After being extruded through extruder 200, the tubing first enters the first chamber, where it is heated by infrared radiation emitted by the infrared emitter within the first chamber. It then enters the second chamber, where it is heated by infrared radiation emitted by the infrared emitter within the second chamber. Finally, it enters the third chamber, where it is heated by infrared radiation emitted by the emitter within the third chamber. The infrared radiation within the first chamber penetrates the surface of the tubing to heat it, while the infrared radiation within the second chamber enhances heat absorption within the middle layer of the tubing. The infrared radiation within the third chamber intensifies heat absorption within the inner layer of the tubing, further reducing the temperature difference within the tubing and promoting the crosslinking reaction. This allows for simultaneous heating of the inner and outer layers of the tubing with infrared radiation of different wavelengths, resulting in a more uniform crosslinking reaction and improved tubing quality. Because the tubing has been microwave-activated before entering the crosslinking chamber, the microwaves preferentially activate the interior, activating the peroxides and molecular chains within the tubing and preparing it for the crosslinking reaction. The infrared radiation then intensifies crosslinking within the outer layer of the tubing, heating the tubing from the outside and ensuring the crosslinking reaction at the surface proceeds fully. This synergistic effect improves the decomposition efficiency of peroxide, shortens the cross-linking reaction time, and reduces the crystallinity of the pipe, avoiding the problem of uneven cross-linking caused by obstruction of the crystallization area.

[0068] Specifically, the first frequency band range is 3-5μm, which belongs to long wave; the second frequency band range is 1.5-3μm, which belongs to medium wave; the third frequency band range is 0.8-1.2μm, which belongs to short wave.

[0069] By using such a wavelength range, the infrared rays in the first cavity heat the surface layer, the infrared rays in the second cavity heat the middle layer, and the infrared rays in the third cavity heat the inner layer.

[0070] The outer layer refers to the part of the pipe close to the outer wall, the inner layer refers to the part of the pipe close to the inner wall, and the middle layer refers to the part between the outer layer and the inner layer.

[0071] The extruder 200 has a first nozzle for introducing a protective gas into the inner hole of the pipe.

[0072] The cross-linking furnace 100 has a second nozzle 150 for introducing protective gas into the cross-linking chamber. The gas outlet direction of the second nozzle 150 is arranged along the radial direction of the pipe.

[0073] The extruder 200 is used to extrude the pipe. The first nozzle is set along the axial direction of the pipe, so that the gas can flow along the length of the pipe, forming a low-oxygen environment on the inner surface of the pipe, preventing the peroxide from being oxidized by oxygen, and ensuring the smooth progress of the cross-linking reaction.

[0074] The second nozzle 150 introduces protective gas with a gas flow rate of ≥5m / s. The protective gas entering from the second nozzle 150 can form an airflow around the surface of the pipe, which continuously flushes the surface of the pipe and takes away any oxygen that may exist, thereby preventing the peroxide from being insufficiently decomposed or producing other side reactions due to oxygen interference during the cross-linking process; on the other hand, it also helps to uniformize the temperature of the pipe surface, making the cross-linking reaction more uniform.

[0075] In some embodiments, the system for manufacturing peroxide cross-linked polyethylene pipes further includes: a cooling water tank 500, an infrared spectrometer 600, and a tractor 700. The cross-linking furnace 100, the cooling water tank 500, the infrared spectrometer 600, and the tractor 700 of the system for manufacturing peroxide cross-linked polyethylene pipes are sequentially arranged along the movement direction of the pipe extruded by the extruder 200.

[0076] The cooling water tank 500 is used to cool and shape the pipe.

[0077] Infrared spectrometer 600 is used to detect the crosslinking degree of the pipe. The spectral data detected by the spectrometer is transmitted to the controller, which analyzes and processes the data to calculate the current crosslinking degree. The controller then dynamically adjusts process parameters such as infrared power, pulling speed, and CO2 flow rate based on the preset crosslinking degree standard and the actual crosslinking degree data. For example, if the crosslinking degree is below the standard, the infrared power is increased, the pulling speed is reduced, or the CO2 flow rate is adjusted to promote the crosslinking reaction. If the crosslinking degree is above the standard, the opposite adjustment measures are taken, achieving closed-loop control of the process parameters and ensuring that the pipe crosslinking degree remains within the ideal range.

[0078] The traction machine 700 is used to provide traction for the pipe and guide the pipe to move along its own axial direction.

[0079] A pipe cutting machine 800 may also be provided on the side of the tractor 700 facing away from the infrared spectrometer 600 .

[0080] In the process of producing 4-inch cross-linked polyethylene pipes according to the American standard ASTM F876, this embodiment improves cross-linking uniformity by more than 50% and peroxide utilization by 35% compared with traditional vertical cross-linking furnaces.

[0081] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A system for manufacturing peroxide cross-linked polyethylene pipes, characterized in that: include: An extruder, which is used for extruding pipes; a cross-linking furnace having a cross-linking chamber with front and rear openings, wherein the cross-linking chamber is used for the pipe to pass through and undergo a cross-linking reaction; a first microwave generator disposed between the extruder and the inlet of the cross-linking furnace, the first microwave generator having a first activation cavity for the tube to pass through, the microwaves generated by the first microwave generator acting on the tube through the first activation cavity to activate the tube; The first microwave generator includes a cabinet, a resonant mechanism, and a magnetron. The resonant mechanism and the magnetron are arranged inside the cabinet. The resonant mechanism has a housing forming a resonant cavity. The housing also forms the first activation cavity in the form of a through hole. The magnetron is arranged around the cavity wall of the first activation cavity. The cross-linking furnace has an infrared emitter, and the infrared rays emitted by the infrared emitter are emitted into the cross-linking chamber. The cross-linking chamber includes a first chamber, a second chamber, and a third chamber arranged in sequence along the movement direction of the pipe. The wavelength of the infrared rays emitted by the infrared emitter into the first chamber is within a first frequency band, the wavelength of the infrared rays emitted by the infrared emitter into the second chamber is within a second frequency band, and the wavelength of the infrared rays emitted by the infrared emitter into the third chamber is within a third frequency band. The first frequency band is greater than the second frequency band, the second frequency band is greater than the third frequency band, and the first frequency band, the second frequency band, and the third frequency band do not overlap with each other.

2. The system for manufacturing peroxide cross-linked polyethylene pipes according to claim 1, characterized in that: Also includes: A second microwave generator is arranged at the outlet side of the cross-linking furnace. The second microwave generator has a second activation cavity for the tube to pass through. The microwaves generated by the second microwave generator act on the tube through the second activation cavity, causing the unreacted groups or cross-linking points inside the tube to continue to react.

3. The system for manufacturing peroxide cross-linked polyethylene pipe according to claim 2, characterized in that: The structure of the first microwave generator is the same as that of the second microwave generator.

4. The system for manufacturing peroxide cross-linked polyethylene pipes according to claim 1, characterized in that: The microwaves generated by the first microwave generator have a frequency range of 2.4 GHz to 2.5 GHz and a power range of 0.5 kW to 2 kW.

5. The system for manufacturing peroxide cross-linked polyethylene pipes according to claim 1, characterized in that: A reflective surface is provided on the cavity wall of the first activation cavity, and the reflective surface is at least a portion of the cavity wall of the first activation cavity.

6. The system for manufacturing peroxide cross-linked polyethylene pipes according to claim 1, characterized in that: The first microwave generator further includes a cooling tube. A through hole is provided on the resonant mechanism. At least a portion of the cooling tube extends into the through hole and communicates with the first activation cavity. The cooling medium of the cooling tube is protective gas.

7. The system for manufacturing peroxide cross-linked polyethylene pipes according to claim 1, characterized in that: The extruder has a first nozzle for introducing a protective gas into the inner hole of the pipe; The cross-linking furnace has a second nozzle for introducing protective gas into the cross-linking chamber, and the gas outlet direction of the second nozzle is arranged along the radial direction of the pipe.

8. The system for manufacturing peroxide cross-linked polyethylene pipes according to claim 7, characterized in that: Also includes: A cooling water tank, an infrared spectrometer and a traction machine are sequentially arranged along the moving direction of the pipe extruded by the extruder, and the cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipes, the cooling water tank, the infrared spectrometer and the traction machine are sequentially arranged.

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