A polyurethane composite pipe and a method for producing the same
By simultaneously forming axial anchoring ribs during the inner tube molding process of polyurethane composite pipe and integrating them with the outer protective tube for foaming, the problem of insufficient bonding force between the inner tube and the insulation layer is solved, achieving efficient and stable composite pipe production and improving insulation performance and production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG AKAN IND CO LTD
- Filing Date
- 2025-09-15
- Publication Date
- 2026-05-12
AI Technical Summary
Traditional polyurethane composite pipes have insufficient bonding strength between the inner tube and the insulation layer, which makes the layers easy to peel off. In addition, the foaming agent is unevenly distributed during the production process, and gaps are easily left between the layers, resulting in low production efficiency and large fluctuations in dimensional accuracy.
An axial anchoring rib is formed simultaneously during the molding process using an inner tube extruder, and then wrapped around the outside of the inner tube using an outer tube extruder. Foaming agent is evenly injected into the mold to achieve one-time composite molding of the inner tube, insulation layer and outer protective tube. One-stop production is achieved using continuous production equipment.
This improved the bonding strength between the inner tube and the insulation layer, prevented interlayer separation, ensured insulation performance and structural protection, and improved production efficiency and product dimensional consistency.
Smart Images
Figure CN121133066B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of urethane composite pipes, specifically to a polyurethane composite pipe and its preparation method. Background Technology
[0002] Polyurethane composite pipes are widely used in heating, water supply and drainage, and chemical fluid transportation due to their excellent thermal insulation, structural stability and corrosion resistance. Their core structure usually includes an inner pipe, a polyurethane insulation layer and an outer protective pipe. The interlayer bonding strength between the inner pipe and the insulation layer directly determines the overall performance and service life of the composite pipe.
[0003] On the one hand, the outer wall of the inner tube of traditional composite pipes is mostly smooth and lacks an anchoring structure to enhance the bonding strength. During the bonding process between the insulation layer and the inner tube, the connection is achieved only by the limited adhesive force between the materials, resulting in low interlayer bonding strength. Under the influence of temperature changes, vibration and other factors during long-term use, the insulation layer is prone to peeling and loosening from the inner tube, leading to increased heat loss and even causing the failure of the entire pipeline structure.
[0004] On the other hand, in existing processes, the inner tube forming, outer tube extrusion, and polyurethane foaming are mostly carried out independently in separate steps: typically, the inner and outer tubes are formed separately first, and then the two are assembled and the foaming agent is injected from the end. This asynchronous production method has obvious drawbacks: first, the foaming agent is difficult to distribute evenly within the annular space, easily forming local voids or uneven density, affecting the insulation effect; second, the outer tube is already fully shaped, and during the foaming process, it cannot achieve a tight fusion with the insulation layer through expansion pressure, easily leaving gaps between layers; third, the step-by-step operation requires multiple material transfers and clamping, resulting in a long production cycle, low efficiency, and difficulty in ensuring the coaxiality of each layer structure, leading to large fluctuations in product dimensional accuracy. Therefore, how to solve the problem of insufficient bonding between the inner tube and the insulation layer and achieve synchronous composite of the outer tube and the foaming process has become a key technical challenge for improving the performance and production efficiency of polyurethane composite pipes. Summary of the Invention
[0005] The purpose of this invention is to solve the problems in the background art and provide a polyurethane composite pipe and its preparation method.
[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution:
[0007] A method for preparing a polyurethane composite pipe includes the following steps:
[0008] S1. Inner tube forming: The inner tube blank is extruded by the inner tube extruder and continuously passed through the inner tube vacuum sizing equipment. During the one-time forming process, axial anchoring ribs are formed on the outer wall of the inner tube. After cooling and shaping, it is output by the inner tube traction machine.
[0009] S2. Composite co-extrusion: The inner tube with anchoring ribs made in step S1 is introduced into the composite molding foaming mold. At the same time, the molten outer tube preform is extruded through the outer tube annular extrusion ring by the outer tube extruder, so that it wraps around the outside of the inner tube, thereby forming an annular foaming agent introduction space between the inner tube and the outer tube preform.
[0010] S3. Injection foaming: The polyurethane foaming agent is injected into the space by a foaming machine, so that it reacts and foams in the sizing pipe, filling the space and tightly wrapping the anchoring ribs on the inner pipe to form a polyurethane insulation layer. At the same time, the outer pipe blank is shaped into an outer protective pipe, realizing the one-time composite molding of the inner pipe, insulation layer and outer protective pipe.
[0011] S4. Cooling and Shaping: The composite tube is cooled and shaped by a composite tube vacuum cooler and then pulled out by a composite tube traction machine.
[0012] This invention enables one-stop continuous production of polyurethane composite pipes. The inner tube anchoring ribs are formed in one step, eliminating the need for traditional multi-process processing and material transfer. The composite co-extrusion and synchronous foaming in the mold are combined to ensure that the insulation layer and the inner tube anchoring ribs are tightly interlocked and thermally fused with the outer protective pipe, completely eliminating interlayer separation, reducing the risk of interlayer detachment, and ensuring both insulation performance and structural protection.
[0013] Preferably, the composite pipe continuous production equipment includes an inner pipe extruder, an inner pipe vacuum sizing device, an inner pipe traction machine, a composite molding foaming mold, a composite pipe vacuum cooling machine, and a composite pipe traction machine arranged sequentially from left to right on the frame. An outer pipe extruder is provided on the front side of the composite molding foaming mold, and a foaming machine is provided on the left side of the outer pipe extruder. The output end of the foaming machine is connected to the inlet end of the composite molding foaming mold.
[0014] This invention achieves one-stop continuous production of polyurethane composite pipes by extruding, sizing, cooling, and traction of the inner tube to create an inner tube with anchoring ribs. The manufactured inner tube is then transported to a composite molding foaming mold. An outer tube is then extruded by an outer tube extruder and fitted onto the inner tube, forming a foaming agent inlet space between the inner and outer tubes. A foaming machine then transports foaming liquid to the composite molding foaming mold to fill the foaming agent inlet space, forming a composite pipe with internal anchoring ribs. The composite pipe is then cooled and cut by a composite pipe traction machine. This realizes one-stop continuous production of polyurethane composite pipes, reducing material transfer and repeated clamping in intermediate links, and significantly improving production efficiency.
[0015] Preferably, the inner tube vacuum sizing device includes a vacuum sizing box, which has an inlet end and an outlet end. The inlet end is provided with a shaped vacuum sizing sleeve, which includes a fixed sleeve, a sizing sleeve, a limiting strip, and a limiting strip telescopic mechanism. The fixed sleeve is fixed to the inlet end of the vacuum sizing box, and the sizing sleeve is fixed inside the fixed sleeve. The sizing sleeve is divided into a sizing area and a cooling area. The sizing area is provided with a vacuum hole, and the fixed sleeve is provided with an air passage communicating with the vacuum hole. The sizing sleeve has a limiting groove along the axial direction, and four or more limiting grooves are evenly distributed along the circumference. The limiting strip is provided in the limiting groove, and the limiting strip telescopic mechanism is used to limit the movement position of the limiting strip within the limiting groove.
[0016] This invention uses a fixing sleeve to fix a non-circular vacuum sizing sleeve to the input end of a vacuum sizing box. Then, the inner tube extruded from the extruder is sizing through the vacuum holes on the sizing sleeve. An anchoring rib is provided in the shaped inner tube through a limiting groove, successfully solving the problem of one-time, continuous extrusion forming of inner tubes with axial anchoring ribs. It also overcomes the limitation that traditional vacuum sizing sleeves can only produce smooth, round tubes. Furthermore, the depth of the limiting strip within the limiting groove can be controlled through a telescopic mechanism and the limiting strip itself. Extending deeper reduces the height of the extruded anchoring rib, while retracting slightly increases the rib height. This dynamic adjustment allows the tube dimensions to be corrected back to standard values at any time, ensuring a high product qualification rate and extremely high dimensional consistency. Simultaneously, it enables production switching between inner tubes with and without anchoring ribs, facilitating the production of different specifications within a certain range and improving the flexibility and efficiency of the production line.
[0017] Preferably, the limiting strip telescopic mechanism includes an internal gear ring, a rack, a fixed ring, a rotating gear, a rotary motor, and a bearing. The fixed ring is located between the sizing zone and the cooling zone. The outer ring of the bearing is fixedly connected to the fixed sleeve, and the inner ring of the bearing is fixedly connected to the internal gear ring. The fixed ring is located inside the internal gear ring. The rack is evenly distributed along the circumferential direction of the fixed ring. Both the fixed ring and the internal gear ring are provided with radial grooves to facilitate radial sliding of the rack. The rotating gear meshes with the rack and the internal gear ring respectively. One of the rotating gears is fixedly connected to the rotary motor. The motor end of the rotary motor is fixed to the fixed sleeve. The support ring is located at the bottom of the rotating gear. The rotating gear is rotatably mounted on the support ring via a bearing.
[0018] This invention uses a rotary motor to drive a connected rotary gear, which meshes with both an internal gear ring and a rack. The rotation of the gear travels on the internal gear ring and simultaneously drives the rack to move precisely radially within the radial groove of the fixed ring. This synchronously pushes all the circumferentially distributed limit bars to extend or retract, thereby controlling the depth of the anchoring ribs. This achieves high-precision synchronous linkage adjustment, ensuring that the adjustment amount of each limit bar is consistent.
[0019] Preferably, the composite molding foaming mold includes a foaming agent annular delivery pipe, an outer tube annular extrusion ring, and a sizing pipe. The outer tube annular extrusion ring is disposed inside the foaming agent annular delivery pipe, and a foaming agent introduction space is formed between the outer tube annular extrusion ring and the foaming agent annular delivery pipe. The sizing pipe is disposed at the output end of the foaming agent annular delivery pipe, and the foaming agent annular delivery pipe and the outer tube annular extrusion ring are aligned with the same axis.
[0020] This invention involves extruding molten outer tube material from an outer tube annular extrusion ring to form a tubular shape. Simultaneously, polyurethane foaming agent is uniformly and circumferentially injected into the foaming agent inlet space. Then, it moves forward together with the inner tube in the sizing tube. The foaming agent reacts and expands rapidly, is wrapped by the molten outer tube, and cools and solidifies together. Thus, the inner tube, insulation layer, and outer tube are simultaneously and synchronously composited in one step, resulting in uniform insulation layer thickness and a strong fusion with the inner wall of the outer tube under high temperature and pressure, completely eliminating the risk of interlayer separation.
[0021] Preferably, the outer tube annular extrusion ring includes an extrusion annular tube body, the inner sidewall of the extrusion annular tube body is provided with a plurality of extrusion holes along the circumferential direction, and the outer sidewall of the extrusion annular tube body is fixed with a feed pipe, the feed pipe being connected to the outer tube extruder.
[0022] In this invention, molten raw material is transported from the outer tube extruder through the feed pipe to the internal cavity of the extrusion annular tube. Subsequently, under pressure, the melt is simultaneously and equally extruded outward from several extrusion holes evenly distributed around the annular tube, thereby achieving uniform distribution and equal extrusion of the molten material in the circumferential direction.
[0023] Preferably, the foaming agent annular delivery pipe includes a foaming agent annular pipe body, an output pipe, a delivery pipe, and a closing ring. The middle part of the foaming agent annular pipe body is an inner pipe delivery channel. The closing ring is sleeved and fixed on the side wall of the foaming agent annular pipe body and is threadedly connected to the outer side wall of the foaming agent annular pipe body. The output pipe is located on the right side of the foaming agent annular pipe body and communicates with the inside of the foaming agent annular pipe body. Several output pipes are arranged in a circumferential array on the foaming agent annular pipe body. The delivery pipe is located on the left side of the foaming agent annular pipe body.
[0024] In this invention, the polyurethane mixed foaming agent is injected into the annular cavity of the foaming agent ring tube through a delivery pipe, and fills the cavity under pressure to achieve initial pressure equalization of the foaming agent. Subsequently, the foaming agent filling the cavity is synchronously and equally transported radially inward to the foaming agent introduction space through several output pipes distributed in a circumferential array. Thus, stable, uniform and synchronous delivery of the foaming agent in the 360° circumferential direction is achieved, ensuring that the foaming agent can be uniformly distributed around the inner tube with consistent pressure and flow rate, providing a core guarantee for the final formation of a polyurethane insulation layer of uniform thickness.
[0025] Preferably, the outer side of the extrusion annular tube is provided with a heat insulation ring, which ensures that the molten material maintains the constant high temperature and good fluidity required by the process when flowing through the extrusion hole. This avoids problems such as poor material fluidity, extrusion pressure fluctuation, surface roughness or even cold material blockage caused by uneven temperature or heat loss, and ensures the stability and surface quality of the outer protective tube extrusion.
[0026] A polyurethane composite pipe includes an inner pipe, a polyurethane insulation layer covering the outside of the inner pipe, and an outer protective pipe covering the outside of the polyurethane insulation layer. The inner pipe has anchoring ribs on its side wall for enhancing interlayer bonding, and four or more anchoring ribs are provided along the outer side wall of the inner pipe.
[0027] The core design of this invention features four or more anchoring ribs on the outer side of the inner tube. By strengthening the bond between the inner tube and the polyurethane insulation layer, and in conjunction with the synergistic effect of the insulation layer and the outer protective tube, it not only improves the overall stability of the pipeline to reduce the risk of interlayer detachment, but also ensures the insulation performance and structural protection, significantly enhancing the reliability and lifespan of the pipeline.
[0028] In summary, the beneficial effects of this invention are as follows:
[0029] 1. This invention realizes one-stop continuous production of polyurethane composite pipes. The inner tube anchor rib is formed in one step, eliminating the need for traditional multi-process processing and material transfer. The composite co-extrusion and synchronous foaming in the mold are combined to make the insulation layer and the inner tube anchor rib tightly interlocked and thermally fused with the outer protective pipe, completely eliminating interlayer separation, reducing the risk of interlayer detachment, and ensuring insulation performance and structural protection.
[0030] 2. This invention produces an inner tube with anchoring ribs by extruding, sizing, cooling, and traction of the inner tube. The produced inner tube is then transported to a composite molding foaming mold. An outer tube is then extruded by an outer tube extruder and fitted onto the inner tube, creating a foaming agent inlet space between the inner and outer tubes. A foaming machine then transports foaming liquid to the composite molding foaming mold to fill the foaming agent inlet space, forming a composite tube with internal anchoring ribs. The composite tube is then cooled and cut by a composite tube traction machine, achieving one-stop continuous production of polyurethane composite tubes. This reduces material transfer and repeated clamping in intermediate steps, significantly improving production efficiency.
[0031] 3. This invention uses a fixing sleeve to fix the irregularly shaped vacuum sizing sleeve to the input end of the vacuum sizing box. Then, the inner tube extruded by the extruder is sizing through the vacuum hole on the sizing sleeve. The shaped inner tube has anchoring ribs through the limiting groove, which successfully solves the problem of one-time continuous extrusion forming of inner tubes with axial anchoring ribs. It also solves the problem that traditional vacuum sizing sleeves can only produce smooth round tubes. At the same time, the depth of the limiting strip in the limiting groove can be controlled by the telescopic mechanism of the limiting strip and the limiting strip. The deeper it extends, the lower the height of the extruded anchoring rib will be. Conversely, the lower it retracts, the higher the rib height will be. Through this dynamic adjustment, the tube size can be corrected back to the standard value at any time, ensuring the product qualification rate and extremely high dimensional consistency. At the same time, it can switch between producing inner tubes with anchoring ribs and those without anchoring ribs, realizing the production of different specifications of products within a certain range, improving the flexibility and efficiency of the production line.
[0032] 4. The core design of this invention features four or more anchoring ribs on the outer side of the inner tube. By strengthening the bond between the inner tube and the polyurethane insulation layer, and in conjunction with the synergistic effect of the insulation layer and the outer protective tube, the overall stability of the pipeline is improved to reduce the risk of interlayer detachment, while also ensuring insulation performance and structural protection, significantly enhancing reliability and lifespan. Attached Figure Description
[0033] Figure 1 This is an overall schematic diagram of the composite pipe continuous production equipment of the present invention;
[0034] Figure 2 This is an overall schematic diagram of the irregularly shaped vacuum sizing sleeve of the present invention;
[0035] Figure 3 This is a schematic diagram of the cooling zone of the irregularly shaped vacuum sizing sleeve of the present invention;
[0036] Figure 4 This is a schematic diagram of the sizing region of the irregularly shaped vacuum sizing sleeve of the present invention;
[0037] Figure 5 This is a schematic diagram of the support plate for the irregularly shaped vacuum sizing sleeve of the present invention;
[0038] Figure 6 This is a schematic diagram of the limit bar telescopic mechanism of the present invention;
[0039] Figure 7 This is a schematic diagram of the composite molding foaming mold of the present invention;
[0040] Figure 8 This is a cross-sectional schematic diagram of the composite molding foaming mold of the present invention;
[0041] Figure 9 This is a schematic diagram of the annular extrusion ring of the outer tube of the present invention;
[0042] Figure 10 This is a cross-sectional schematic diagram of the polyurethane composite pipe of the present invention;
[0043] Figure 11 This is a schematic diagram of the inner tube of the polyurethane composite pipe of the present invention;
[0044] 1. Inner tube extruder; 2. Inner tube vacuum sizing equipment; 904. Anchor rib; 3. Inner tube traction machine; 900. Inner tube with anchor rib; 4. Composite molding foaming mold; 7. Outer tube extruder; 42. Outer tube annular extrusion ring; 44. Foaming agent introduction space; 8. Foaming machine, polyurethane foaming agent; 43. Sizing tube; 901. Polyurethane insulation layer; 903. Outer protective tube; 5. Composite tube vacuum cooler; 6. Composite tube traction machine; 105. Composite tube continuous production equipment; 21. Vacuum sizing box; 22. Irregularly shaped vacuum sizing sleeve; 221. Fixing sleeve; 222. Sizing sleeve; 224. Limiting strip; 23. Limiting strip Telescopic mechanism, 220, sizing zone, 223, cooling zone, 225, vacuum hole, 226, limiting groove, 231, internal gear ring, 232, rack, 233, fixing ring, 234, rotating gear, 235, rotating motor, 236, bearing, 238, support ring, 237, radial groove, 41, foaming agent annular conveying pipe, 421, extrusion annular pipe body, 422, extrusion hole, 423, feed pipe, 411, foaming agent annular pipe body, 412, output pipe, 413, conveying pipe, 414, closing ring, 415, inner pipe conveying channel, 424, insulation ring, polyurethane composite pipe, 900, inner pipe. Detailed Implementation
[0045] The following specific embodiments are merely illustrative of the present invention and are not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to these embodiments without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of the present invention.
[0046] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Example
[0047] A method for preparing a polyurethane composite pipe includes the following steps:
[0048] S1. Inner tube forming: The inner tube blank is extruded by the inner tube extruder 1 and continuously passed through the inner tube vacuum sizing equipment 2. During the one-time forming process, axial anchoring ribs 904 are simultaneously formed on the outer wall of the inner tube. After cooling and shaping, it is output by the inner tube traction machine 3.
[0049] S2. Composite co-extrusion: The inner tube 900 with anchoring ribs made in step S1 is introduced into the composite molding foaming mold 4. At the same time, the molten outer tube preform is extruded through the outer tube annular extrusion ring 42 by the outer tube extruder 7, so that it wraps around the outside of the inner tube, thereby forming an annular foaming agent introduction space 44 between the inner tube and the outer tube preform.
[0050] S3. Injection foaming: The polyurethane foaming agent is injected into the space 44 by the foaming machine 8, so that it reacts and foams in the sizing pipe 43, filling the space and tightly wrapping the anchor ribs 904 on the inner pipe to form a polyurethane insulation layer 901. At the same time, the outer pipe blank is shaped into an outer protective pipe 903, realizing the one-time composite molding of the inner pipe, insulation layer and outer protective pipe.
[0051] S4. Cooling and Shaping: The composite tube is cooled and shaped by the composite tube vacuum cooler 5 and then pulled out by the composite tube traction machine 6.
[0052] like Figure 1 As shown, the composite pipe continuous production equipment 105 includes, from left to right, an inner pipe extruder 1, an inner pipe vacuum sizing device 2, an inner pipe traction machine 3, a composite molding foaming mold 4, a composite pipe vacuum cooler 5, and a composite pipe traction machine 6, all arranged on the frame. An outer pipe extruder 7 is provided in front of the composite molding foaming mold 4, and a foaming machine 8 is provided on the left side of the outer pipe extruder 7. The output end of the foaming machine 8 is connected to the inlet end of the composite molding foaming mold 4. The inner pipe vacuum sizing device 2 includes a vacuum sizing box 21, which has an inlet end and an outlet end. The inlet end is provided with a shaped vacuum sizing sleeve 22.
[0053] like Figures 2-5As shown, the irregularly shaped vacuum sizing sleeve 22 includes a fixed sleeve 221, a sizing sleeve 222, a limiting strip 224, and a limiting strip telescopic mechanism 23. The fixed sleeve 221 is fixed to the inlet end of the vacuum sizing box 21, and the sizing sleeve 222 is fixed inside the fixed sleeve 221. The sizing sleeve 222 is divided into a sizing area 220 and a cooling area 223. The sizing area 220 is provided with a vacuum hole 225, and the fixed sleeve 221 is provided with an air passage communicating with the vacuum hole 225. The sizing sleeve 222 has a limiting groove 226 along the axial direction, and four or more limiting grooves 226 are evenly distributed along the circumference. The limiting strip 224 is disposed in the limiting groove 226. The limiting strip telescopic mechanism 23 is used to limit the movement position of the limiting strip 224 within the limiting groove 226. The limiting strip telescopic mechanism 23 includes an internal gear ring 231, a rack 232, a fixed ring 233, and a rotating... The system comprises a gear 234, a rotary motor 235, a bearing 236, and a support ring 238. A fixed ring 233 is located between a sizing zone 220 and a cooling zone 223. The outer ring of the bearing 236 is fixedly connected to a fixed sleeve 221, and the inner ring of the bearing 236 is fixedly connected to an internal gear ring 231. The fixed ring 233 is located inside the internal gear ring 231. A rack 232 is evenly distributed along the circumferential direction of the fixed ring 233. Both the fixed ring 233 and the internal gear ring 231 are provided with radial grooves 237 to facilitate the radial sliding of the rack 232. A rotary gear 234 meshes with the rack 232 and the internal gear ring 231 respectively. One of the rotary gears 234 is fixedly connected to the rotary motor 235. The motor end of the rotary motor 235 is fixed to the fixed sleeve 221. The support ring 238 is located at the bottom of the rotary gear 234, and the rotary gear 234 is rotatably mounted on the support ring 238.
[0054] like Figures 6-9As shown, the composite molding foaming mold 4 includes a foaming agent annular delivery pipe 41, an outer tube annular extrusion ring 42, and a sizing pipe 43. The outer tube annular extrusion ring 42 is disposed inside the foaming agent annular delivery pipe 41, and a foaming agent inlet space 44 is formed between the outer tube annular extrusion ring 42 and the foaming agent annular delivery pipe 41. The sizing pipe 43 is disposed at the output end of the foaming agent annular delivery pipe 41. The foaming agent annular delivery pipe 41 and the outer tube annular extrusion ring 42 are coaxial. The outer tube annular extrusion ring 42 includes an extrusion annular tube body 421. The inner sidewall of the extrusion annular tube body 421 is provided with a plurality of extrusion holes 422 along the circumferential direction. The outer sidewall of the extrusion annular tube body 421 is fixed with a feed pipe 423. The feed pipe 423 and the outer tube... The extruder 7 is connected. The foaming agent annular conveying pipe 41 includes a foaming agent annular pipe body 411, an output pipe 412, a conveying pipe 413, and a closing ring 414. The middle part of the foaming agent annular pipe body 411 is an inner pipe conveying channel 415. The closing ring 414 is sleeved and fixed on the side wall of the foaming agent annular pipe body 411. The closing ring 414 is threadedly connected to the outer side wall of the foaming agent annular pipe body 411. The output pipe 412 is located on the right side of the foaming agent annular pipe body 411 and communicates with the inside of the foaming agent annular pipe body 411. Several output pipes 412 are arranged in a circumferential array on the foaming agent annular pipe body 411. The conveying pipe 413 is located on the left side of the foaming agent annular pipe body 411. A heat preservation ring 424 is provided on the outer side of the extrusion annular pipe body 421.
[0055] like Figures 10-11 As shown, a polyurethane composite pipe includes an inner pipe 900, a polyurethane insulation layer 901 covering the outside of the inner pipe 900, and an outer protective pipe 903 covering the outside of the polyurethane insulation layer 901. The inner pipe 900 has anchoring ribs 904 on its side wall for enhancing interlayer bonding, and four or more anchoring ribs 904 are provided along the outer side wall of the inner pipe 900.
[0056] Working principle: such as Figures 1-11As shown, the inner tube extruder 1 extrudes molten plastic raw material to form a tubular preform. This high-temperature preform immediately enters the inner tube vacuum sizing device 2. The preform first passes through the irregularly shaped vacuum sizing sleeve 22. Multiple circumferentially distributed limiting strips 224 on the inner circumference of the sizing sleeve are pressed against the outer surface of the preform to form axial anchoring ribs 904. At the same time, the vacuum holes 225 on the sizing zone 220 generate adsorption force, tightly adhering the outer wall of the ribbed preform to the inner surface of the sizing sleeve for preliminary shaping and water cooling. Subsequently, the pre-shaped inner tube enters the cooling zone 223 for full cooling and solidification. The cooling zone can be equipped with cooling channels for cooling. During this process, the extension amount of the limiting strips can be dynamically adjusted by the limiting strip extension mechanism 23 to precisely control the forming size of the anchoring ribs. Finally, the inner tube traction machine 3 provides traction power to stably output the fully shaped and cooled inner tube with anchoring ribs into the inner tube conveying channel 415 of the composite molding foaming mold 4. Meanwhile, the outer tube extruder 7 extrudes molten plastic raw material into the inner tube conveying channel 415 of the composite molding foaming mold 4. The raw material for the outer protective tube is fed into the annular cavity of the outer tube annular extrusion ring 42 through the feed pipe 423. The melt is then stably extruded from the circumferentially distributed extrusion holes 422 to form a molten outer tube preform that encloses the inner tube 900. During this process, the foaming agent annular conveying pipe 41 and the outer tube annular extrusion ring 42 remain coaxial, thereby forming an annular foaming agent introduction space 44 between the inner tube 900 and the outer tube preform. The foaming machine 8 delivers the mixed polyurethane raw material through the conveying pipe 423. 13. The foaming agent is pumped into the annular cavity of the annular tube 411 for pressure equalization. Then, through multiple output tubes 412 distributed in a circumferential array, the foaming agent is uniformly, equally, and synchronously injected into the foaming agent introduction space 44. In the sizing tube 43 of the composite molding foaming mold 4, the injected foaming agent begins a chemical reaction and rapidly expands and foams, filling all the gaps between the inner tube 900 and the outer tube preform, while simultaneously pushing the molten outer tube preform to adhere to the inner wall of the sizing tube 43 for cooling and shaping. During this process, the inner tube, the foaming polyurethane insulation layer 901, and the outer protective tube 903 are composite molded in one step, and then cooled and cut to form a polyurethane composite tube.
Claims
1. A method for preparing a polyurethane composite pipe, characterized in that, The method uses a composite pipe continuous production equipment (105), which includes an inner pipe extruder (1), an inner pipe vacuum sizing device (2), an inner pipe traction machine (3), a composite molding foaming mold (4), a composite pipe vacuum cooler (5), and a composite pipe traction machine (6) arranged sequentially from left to right on the frame. An outer pipe extruder (7) is provided on the front side of the composite molding foaming mold (4), and a foaming machine (8) is provided on the left side of the outer pipe extruder (7). The output end of the foaming machine (8) is connected to the inlet end of the composite molding foaming mold (4). The inner tube vacuum sizing device (2) includes a vacuum sizing box (21), which has an inlet end and an outlet end, and the inlet end is provided with a special-shaped vacuum sizing sleeve (22). The irregularly shaped vacuum sizing sleeve (22) includes a fixed sleeve (221), a sizing sleeve (222), a limiting strip (224), and a limiting strip telescopic mechanism (23). The fixed sleeve (221) is fixed at the inlet end of the vacuum sizing box (21), and the sizing sleeve (222) is fixed inside the fixed sleeve (221). The sizing sleeve (222) is divided into a sizing area (220) and a cooling area (223). The sizing area (220) is provided with a vacuum hole (224). 5) The fixed sleeve (221) is provided with an air passage communicating with the vacuum hole (225). The sizing sleeve (222) is provided with a limiting groove (226) along the axial direction. There are four or more limiting grooves (226) evenly distributed along the circumferential direction. The limiting strip (224) is provided in the limiting groove (226). The limiting strip telescopic mechanism (23) is used to limit the movement position of the limiting strip (224) in the limiting groove (226). The composite molding foaming mold (4) includes a foaming agent annular delivery pipe (41), an outer tube annular extrusion ring (42), and a sizing pipe (43). The outer tube annular extrusion ring (42) is located inside the foaming agent annular delivery pipe (41). A foaming agent introduction space (44) is formed between the outer tube annular extrusion ring (42) and the foaming agent annular delivery pipe (41). The sizing pipe (43) is located at the output end of the foaming agent annular delivery pipe (41). The foaming agent annular delivery pipe (41) and the outer tube annular extrusion ring (42) are aligned with the same axis. Polyurethane composite pipes produced using a continuous composite pipe production equipment (105) Includes the following steps: S1. Inner tube forming: The inner tube blank is extruded by the inner tube extruder (1) and continuously passed through the inner tube vacuum sizing equipment (2). During the one-time forming process, axial anchoring ribs (904) are simultaneously formed on the outer wall of the inner tube. After cooling and shaping, it is output by the inner tube traction machine (3). S2. Composite co-extrusion: The inner tube (900) with anchoring ribs made in step S1 is introduced into the composite molding foaming mold (4). At the same time, the molten outer tube preform is extruded through the outer tube annular extrusion ring (42) by the outer tube extruder (7) to wrap around the outside of the inner tube, thereby forming an annular foaming agent introduction space (44) between the inner tube and the outer tube preform. S3. Injection foaming: The polyurethane foaming agent is injected into the foaming agent introduction space (44) by the foaming machine (8), so that it reacts and foams in the sizing pipe (43), filling the space and tightly wrapping the anchoring ribs (904) on the inner pipe, forming a polyurethane insulation layer (901), while the outer pipe blank is shaped into an outer protective pipe (903), realizing the one-time composite molding of the inner pipe, insulation layer and outer protective pipe; S4. Cooling and shaping: The composite tube is cooled and shaped by a composite tube vacuum cooler (5) and then pulled out by a composite tube traction machine (6).
2. The method for preparing a polyurethane composite pipe according to claim 1, characterized in that, The limiting bar telescopic mechanism (23) includes an internal gear ring (231), a rack (232), a fixed ring (233), a rotating gear (234), a rotating motor (235), a bearing (236), and a support ring (238). The fixed ring (233) is located between the sizing zone (220) and the cooling zone (223). The outer ring of the bearing (236) is fixedly connected to the fixed sleeve (221), and the inner ring of the bearing (236) is fixedly connected to the internal gear ring (231). The fixed ring (233) is located inside the internal gear ring (231), and the rack (232) moves along the fixed ring (234). 233) The fixed ring (233) and the internal gear ring (231) are evenly distributed in the circumferential direction. Both the fixed ring (233) and the internal gear ring (231) are provided with radial grooves (237) to facilitate the radial sliding of the rack (232). The rotating gear (234) meshes with the rack (232) and the internal gear ring (231) respectively. One of the rotating gears (234) is fixedly connected to the rotating motor (235). The motor end of the rotating motor (235) is fixed on the fixed sleeve (221). The support ring (238) is located at the bottom of the rotating gear (234). The rotating gear (234) is rotatably located on the support ring (238).
3. The method for preparing a polyurethane composite pipe according to claim 1, characterized in that, The outer tube annular extrusion ring (42) includes an extrusion annular tube body (421). The inner sidewall of the extrusion annular tube body (421) is provided with a plurality of extrusion holes (422) along the circumferential direction. The outer sidewall of the extrusion annular tube body (421) is fixed with a feed pipe (423). The feed pipe (423) is connected to the outer tube extruder (7).
4. The method for preparing a polyurethane composite pipe according to claim 3, characterized in that, The foaming agent annular delivery pipe (41) includes a foaming agent annular pipe body (411), an output pipe (412), a delivery pipe (413), and a closing ring (414). The middle part of the foaming agent annular pipe body (411) is an inner pipe delivery channel (415). The closing ring (414) is sleeved and fixed on the side wall of the foaming agent annular pipe body (411). The closing ring (414) is threadedly connected to the outer side wall of the foaming agent annular pipe body (411). The output pipe (412) is located on the right side of the foaming agent annular pipe body (411) and communicates with the inside of the foaming agent annular pipe body (411). Several output pipes (412) are arranged in a circumferential array on the foaming agent annular pipe body (411). The delivery pipe (413) is located on the left side of the foaming agent annular pipe body (411).
5. The method for preparing a polyurethane composite pipe according to claim 3, characterized in that, The outer side of the extruded annular tube (421) is provided with a heat-insulating ring (424).