Modified PVC thermal insulation pipe integrated processing technology

Abstract

The application discloses a modified PVC thermal insulation pipe integrated processing technology. The process includes seven steps of inner layer modified material preparation, thermal insulation foaming material preparation, outer layer protection material preparation, integrated co-extrusion and feeding, synchronous shaping and foaming under vacuum environment, gradient cooling shaping, and traction and online detection adjustment. The interface modifier of maleic anhydride grafted polyethylene and epoxy fatty acid methyl ester is added in the inner layer modified material, and nano silicon dioxide aerogel powder and foaming agent are added in the thermal insulation foaming material. The three melt bodies are independently plasticized and then synchronously extruded at the same co-extrusion outlet to form a tubular parison, the parison is immediately introduced into a negative pressure environment to synchronously complete the outer wall shaping and the in-situ foaming of the thermal insulation layer, and then the finished product is obtained through three-stage gradient cooling and traction cutting. The application realizes the integrated continuous molding of the modified PVC thermal insulation pipe, and the obtained pipe has strong interlayer bonding force, excellent thermal insulation performance and high size precision, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of polymer material pipe processing technology, specifically an integrated processing technology for modified PVC insulation pipes. Background Technology

[0002] PVC insulated pipes are widely used in building water supply and drainage, chemical material transportation, and municipal engineering due to their excellent corrosion resistance, flame retardancy, and processing performance. Currently, the processing of PVC insulated pipes mainly employs the following methods.

[0003] 1. Multilayer co-extrusion foaming process: Two or three extruders are used to co-extrude inner and outer layers of dense PVC material and a core layer containing foaming agent into the same die head, forming a three-layer structure with inner and outer rigid PVC layers sandwiching a foamed layer in the middle. Although this process achieves the combination of two plastics with different proportions, the bonding between the inner and outer layers and the foamed core layer is only physical, with limited interlayer bonding strength, making it prone to interlayer delamination during long-term use.

[0004] 2. The step-by-step composite process involves first preparing the inner tube, then wrapping it with polyethylene (PEF) insulation or polyurethane foam, and finally adding an outer plastic tube. This process has many steps, a long production cycle, and gaps between the insulation layer and the pipe wall, resulting in unsatisfactory insulation performance.

[0005] 3. An external insulation layer is added, where insulation cotton or rock wool is wrapped around the PVC pipe. This method results in a discontinuous insulation layer, exposed sections of the pipe, and the insulation cotton is prone to aging and falling off after long-term use, limiting its insulation capacity. Summary of the Invention

[0006] The purpose of this invention is to provide an integrated processing technology for modified PVC insulation pipes, which aims to solve the problems of insufficient interlayer bonding, scattered processes, low production efficiency, and poor bonding between the insulation layer and the pipe body in existing PVC insulation pipe processing technologies.

[0007] To solve the above-mentioned technical problems, the present invention provides an integrated processing technology for modified PVC thermal insulation pipes, comprising the following steps: Step 1: Preparation of the inner layer modifier. By weight, take 100 parts of PVC resin, 3 to 5 parts of heat stabilizer, 1 to 2 parts of lubricant, 6 to 10 parts of toughening modifier, and 2 to 4 parts of interface modifier, and add them to a high-speed mixer. Mix at 100 to 120 degrees Celsius for 10 to 15 minutes to obtain the inner layer modified mixture. The interface modifier is a compound of maleic anhydride-grafted polyethylene and epoxy fatty acid methyl ester, with a mass ratio of 1:1.

[0008] Step 2: Preparation of Thermal Insulation Foaming Material. By weight, take 100 parts of PVC resin, 2 to 4 parts of heat stabilizer, 4 to 8 parts of foaming agent, 1 to 3 parts of foaming aid, 0.5 to 1.5 parts of nucleating agent, and 8 to 15 parts of nano-silica aerogel powder. Add these to a high-speed mixer and mix for 8 to 12 minutes at 80 to 100 degrees Celsius to obtain the thermal insulation foaming mixture. The foaming agent is a compound of azodicarbonamide and sodium bicarbonate, with a mass ratio of 3:1. The nano-silica aerogel powder has a particle size of 20 to 50 nanometers and a thermal conductivity of less than 0.020 W / m Kelvin.

[0009] Step 3: Preparation of the outer protective material. By weight, take 100 parts of PVC resin, 3 to 5 parts of heat stabilizer, 1.5 to 3 parts of lubricant, 5 to 8 parts of weather-resistant modifier, 0.5 to 1 part of ultraviolet absorber, and 10 to 20 parts of reinforcing filler, and put them into a high-speed mixer. Mix them at a temperature of 110 to 130 degrees Celsius for 10 to 15 minutes to obtain the outer protective mixture.

[0010] Step 4: Integrated Co-extrusion Plasticization and Feeding. The inner layer modified mixture obtained in Step 1 is plasticized at a temperature of 170 to 190 degrees Celsius, the thermal insulation foaming mixture obtained in Step 2 is plasticized at a temperature of 160 to 180 degrees Celsius, and the outer layer protective mixture obtained in Step 3 is plasticized at a temperature of 175 to 195 degrees Celsius. The three plasticized melts are fed to the same co-extrusion port through independent runners. The outlet temperature of the inner layer melt is controlled at 175 to 185 degrees Celsius, the outlet temperature of the thermal insulation layer melt is 165 to 175 degrees Celsius, and the outlet temperature of the outer layer melt is 180 to 190 degrees Celsius. The three melts are extruded simultaneously at the co-extrusion port to form a tubular preform in which the inner layer, thermal insulation layer, and outer layer are tightly composited from the inside out.

[0011] Step 5: Synchronous Shaping and Foaming under Vacuum Environment. The tubular preform obtained in Step 4 is immediately introduced into a negative pressure environment. The absolute pressure of this environment is controlled at 0.06 to 0.09 MPa, applying a uniform negative pressure to the outer wall of the preform to shape it under this pressure. Simultaneously, the foaming agent in the insulation layer decomposes and foams under the combined effect of the residual heat carried by the preform after extrusion in Step 4 and the negative pressure environment, forming a uniform and dense closed-cell foam structure inside the insulation layer. The residence time of the tubular preform in the negative pressure environment is 30 to 90 seconds.

[0012] Step Six: Gradient Cooling and Shaping. The pipe processed in Step Five is sequentially introduced into three cooling media. The temperature of the first cooling medium is 60 to 80 degrees Celsius, the temperature of the second cooling medium is 30 to 50 degrees Celsius, and the temperature of the third cooling medium is 15 to 25 degrees Celsius. The residence time of the pipe in each cooling medium is 20 to 40 seconds, resulting in a semi-finished modified PVC insulation pipe.

[0013] Step 7: Traction and Online Monitoring and Adjustment. The semi-finished product obtained in Step 6 is tractioned and sent out at a traction speed of 0.5 to 2 meters per minute. During the traction process, the outer diameter of the pipe and the thickness of each layer are monitored online. The traction speed and the amount of melt supplied to each layer are adjusted according to the monitoring data to ensure that the thickness of each layer of the pipe is uniform. Finally, the pipe is cut to a fixed length according to the set length to obtain the finished modified PVC insulation pipe.

[0014] Furthermore, the toughening modifier mentioned in step one is a compound of chlorinated polyethylene and acrylonitrile butadiene styrene copolymer, with a compounding mass ratio of 2 to 1.

[0015] Furthermore, the preparation method of the interface modifier mentioned in step one is as follows: maleic anhydride grafted polyethylene and epoxy fatty acid methyl ester are mixed at a mass ratio of 1:1, melt-mixed at a temperature of 80 to 100 degrees Celsius for 10 to 20 minutes, cooled and then pulverized to 100 to 200 mesh.

[0016] Furthermore, the foaming agent mentioned in step two is a compound of zinc oxide and zinc stearate, with a mass ratio of 1:1.

[0017] Furthermore, the nucleating agent mentioned in step two is nano-calcium carbonate with an average particle size of 100 to 300 nanometers.

[0018] Furthermore, the weather-resistant modifier mentioned in step three is an acrylate-based impact modifier, the ultraviolet absorber is a benzotriazole-based ultraviolet absorber, and the reinforcing filler is light calcium carbonate surface-treated with a silane coupling agent.

[0019] Furthermore, the plasticizing time of the three melts mentioned in step four is independently 2 to 6 minutes.

[0020] Furthermore, the pressure in the negative pressure environment described in step five is 0.07 to 0.08 MPa.

[0021] Furthermore, in step six, all three cooling media are water, and each cooling medium is applied to the pipe surface by spraying.

[0022] Furthermore, the modified PVC insulation pipe produced by this process has an inner layer thickness of 1.5 to 3 mm, an insulation layer thickness of 5 to 15 mm, an outer layer thickness of 1.5 to 3 mm, and a total wall thickness of 8 to 21 mm, wherein the insulation layer thickness accounts for 60% to 75% of the total wall thickness.

[0023] In summary, due to the adoption of the above-mentioned technologies, the beneficial effects of this invention are: 1. This invention realizes the integrated continuous molding of modified PVC thermal insulation pipes. The three melts are simultaneously extruded and tightly compounded at the co-extrusion port, eliminating the intermediate steps and secondary processing links of the existing step-by-step compounding process, which greatly improves production efficiency and reduces energy consumption and labor costs.

[0024] 2. This invention incorporates an interface modifier, a blend of maleic anhydride-grafted polyethylene and epoxy fatty acid methyl ester, into the inner layer modified material. This interface modifier migrates to the interface between the inner layer and the insulation layer during co-extrusion molding. Through the chemical bonding of maleic anhydride groups with the PVC molecular chains in the foam layer, and the compatibilizing effect of epoxy groups on the inner layer PVC, the interfacial bonding strength between the inner layer and the insulation layer is significantly improved. Simultaneously, due to the exit temperature gradient design and synchronous extrusion process, the molecular chains in the molten state diffuse and entangle between the outer protective material and the insulation layer, resulting in a much stronger interlayer bonding force than traditional physical bonding methods, effectively solving the problem of easy peeling and detachment of the insulation layer in existing technologies.

[0025] 3. This invention combines the two processes of negative pressure shaping of the pipe outer wall and foaming of the insulation layer into one. While the tubular preform is shaped under pressure in a negative pressure environment, the foaming agent in the insulation layer undergoes in-situ foaming under the combined effects of the preform's residual heat and the negative pressure conditions. The negative pressure environment ensures accurate pipe outer diameter dimensions and a smooth outer wall, while also facilitating the uniform release of decomposition gases from the foaming agent and the growth of foam cells, resulting in a uniform and dense closed-cell foam structure within the insulation layer. Compared to the separate processes of shaping followed by foaming or foaming followed by shaping in existing technologies, the simultaneous process of this invention reduces heat loss, improves foaming efficiency, and simultaneously ensures the uniformity of the insulation layer's foam cell structure and the stability of the pipe dimensions.

[0026] 4. This invention incorporates nano-silica aerogel powder into the thermal insulation foam material. This material possesses extremely high porosity and extremely low thermal conductivity. When combined with the foamed PVC matrix, it can form a nanoscale thermal insulation network within the pores of the foam structure, significantly reducing the thermal conductivity of the insulation layer. Simultaneously, the nano-size effect of the nano-silica aerogel can act as heterogeneous nucleation sites, promoting uniform nucleation and refinement of pores during the foaming process, further improving pore density and closed-cell ratio.

[0027] 5. This invention implements gradient temperature control at the co-extrusion outlet for the three melt streams: the inner layer outlet temperature is 175-185 degrees Celsius, the insulation layer outlet temperature is 165-175 degrees Celsius, and the outer layer outlet temperature is 180-190 degrees Celsius. This ensures that the insulation layer temperature is slightly lower than the inner and outer layer temperatures, guaranteeing that the foaming agent has a suitable foaming temperature within the insulation layer while preventing degradation or deformation of the inner and outer layers due to excessively high temperatures. This gradient temperature control method ensures that the three melt streams exhibit similar rheological behavior and compatibility when they merge, reducing the generation of interlayer stress.

[0028] 6. This invention employs a three-stage gradient cooling method, gradually reducing temperature from high to low, thus preventing internal stress and warping deformation of the pipe due to rapid cooling. Simultaneously, the foam structure of the insulation layer remains fixed and stable during the cooling process, ensuring the durability of the insulation performance. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention, making other features, objects, and advantages of the invention more apparent. The illustrative embodiments of the invention illustrated in the drawings and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be understood that the terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the drawings and are only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0032] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific context of the specification.

[0033] Example 1 This embodiment provides an integrated processing technology for modified PVC thermal insulation pipes, specifically including the following steps: 1. Preparation of inner layer modified material: By weight, take 100 parts of PVC resin, 4 parts of calcium-zinc composite heat stabilizer, 1.5 parts of stearic acid lubricant, 8 parts of toughening modifier compounded with chlorinated polyethylene and acrylonitrile butadiene styrene copolymer (compounded mass ratio 2:1), and 3 parts of interface modifier compounded with maleic anhydride grafted polyethylene and epoxy fatty acid methyl ester (compounded mass ratio 1:1), put them into a high-speed mixer, and mix for 12 minutes at a temperature of 110 degrees Celsius to obtain inner layer modified mixture.

[0034] 2. Preparation of thermal insulation foam material: By weight, take 100 parts of PVC resin, 3 parts of calcium-zinc composite heat stabilizer, 6 parts of azodicarbonamide and sodium bicarbonate compound foaming agent (compound mass ratio 3:1), 2 parts of zinc oxide and zinc stearate compound foaming aid (compound mass ratio 1:1), 1 part of nano calcium carbonate nucleating agent, and 12 parts of nano silica aerogel powder (particle size 30 nm, thermal conductivity 0.018 W / m Kelvin), put them into a high-speed mixer, and mix them at 90 degrees Celsius for 10 minutes to obtain thermal insulation foam mixture.

[0035] 3. Preparation of outer protective material: By weight, take 100 parts of PVC resin, 4 parts of calcium-zinc composite heat stabilizer, 2 parts of stearic acid lubricant, 6 parts of acrylate impact modifier, 0.8 parts of benzotriazole ultraviolet absorber, and 15 parts of light calcium carbonate reinforcing filler surface treated with silane coupling agent, put them into a high-speed mixer, and mix them at 120 degrees Celsius for 12 minutes to obtain the outer protective mixture.

[0036] 4. Integrated Co-extrusion Plasticization and Feeding: The inner layer modified mixture is plasticized at 180°C for 4 minutes, the thermal insulation foam mixture at 170°C for 4 minutes, and the outer layer protective mixture at 185°C for 4 minutes. The three plasticized melts are then fed to the same co-extrusion port through independent flow channels. The outlet temperatures of the inner layer melt, the thermal insulation layer melt, and the outer layer melt are controlled at 180°C, 170°C, and 185°C, respectively. The three melts are extruded simultaneously at the co-extrusion port to form a tubular preform with the inner, thermal insulation, and outer layers sequentially composited from the inside out.

[0037] 5. Synchronous shaping and foaming under vacuum: The tubular preform is immediately introduced into a negative pressure environment, with the absolute pressure controlled at 0.08 MPa, and a uniform negative pressure is applied to the outer wall of the tubular preform. The tubular preform remains in the negative pressure environment for 60 seconds. Under the combined action of the residual heat carried by the preform after extrusion and the negative pressure environment, the foaming agent in the insulation layer decomposes and foams, forming a closed-cell foam structure.

[0038] 6. Gradient cooling and shaping: The pipe is sequentially introduced into three cooling water sections. The first section has a water temperature of 70 degrees Celsius and a holding time of 30 seconds. The second section has a water temperature of 40 degrees Celsius and a holding time of 30 seconds. The third section has a water temperature of 20 degrees Celsius and a holding time of 30 seconds, resulting in a semi-finished product.

[0039] 7. Traction and Online Monitoring and Adjustment: The semi-finished product is tractioned and sent out at a speed of 1 meter per minute. During the traction process, the outer diameter of the pipe and the thickness of each layer are monitored online. The traction speed and the amount of melt fed into each layer are adjusted according to the monitoring data. Finally, the finished product is cut to the set length.

[0040] The modified PVC insulated pipe obtained in this embodiment has an inner layer thickness of 2 mm, an insulation layer thickness of 10 mm, and an outer layer thickness of 2 mm, with a total wall thickness of 14 mm. The insulation layer thickness accounts for 71.4% of the total wall thickness. Testing showed that the interlayer peel strength reached 4.5 N / mm, the thermal conductivity was 0.028 W / m Kelvin, and the outer diameter deviation of the pipe was within ±0.3 mm.

[0041] Example 2 The difference between this embodiment and Embodiment 1 is that the amount of interface modifier added to the inner layer modified material is 4 parts, the amount of nano-silica aerogel powder added to the thermal insulation foaming material is 15 parts, the absolute pressure of the negative pressure environment is 0.07 MPa, and the traction speed is 0.8 m / min. The remaining steps and parameters are the same as in Embodiment 1.

[0042] The modified PVC insulation pipe obtained in this embodiment has a thermal conductivity of 0.025 W / m Kelvin and an interlayer peel strength of 4.8 N / mm.

[0043] Example 3 The difference between this embodiment and Embodiment 1 is that the inner layer thickness is 1.5 mm, the insulation layer thickness is 15 mm, and the outer layer thickness is 1.5 mm. The melt plasticizing temperature of the inner layer is 185 degrees Celsius, the melt plasticizing temperature of the insulation layer is 175 degrees Celsius, and the melt plasticizing temperature of the outer layer is 190 degrees Celsius. The melt outlet temperature of the inner layer is 185 degrees Celsius, the melt outlet temperature of the insulation layer is 175 degrees Celsius, and the melt outlet temperature of the outer layer is 190 degrees Celsius. The remaining steps and parameters are the same as in Embodiment 1.

[0044] The modified PVC insulation pipe obtained in this embodiment has a thermal conductivity of 0.026 W / m Kelvin and a ring stiffness of 12 kN / m².

[0045] Comparative Example To verify the technical effects of the present invention, the following comparative examples are provided.

[0046] Comparative Example 1: A traditional dual-machine co-extrusion core layer foaming process was adopted. The inner and outer layers shared a single set of plasticizers, while the foamed core layer was supplied by a separate set. Both sets of melts were fed to the same co-extrusion port. No outlet gradient temperature control was implemented, and no interface modifiers or nano-silica aerogel were added. The pipe's outer wall shaping and foaming were performed in separate steps. The resulting pipe had an interlayer peel strength of 2.1 N / mm and a thermal conductivity of 0.045 W / m Kelvin.

[0047] Comparative Example 2: A step-by-step composite process was used, first preparing the inner tube, then covering it with a polyethylene foam insulation layer, and finally inserting a U-PVC outer tube. The resulting pipe had an interlayer peel strength of 1.5 N / mm, a thermal conductivity of 0.038 W / m Kelvin, and a relatively large deviation in the outer diameter.

[0048]

[0049] Table 1. Main differences between each embodiment and the comparative example. The comparison shows that the pipes produced by the process of this invention are significantly superior to the prior art in terms of interlayer bonding strength, thermal insulation performance and dimensional accuracy.

Claims

1. An integrated processing technology for modified PVC thermal insulation pipes, characterized in that: Includes the following steps: Step 1: Preparation of inner layer modified material: By weight, 100 parts of PVC resin, 3 to 5 parts of heat stabilizer, 1 to 2 parts of lubricant, 6 to 10 parts of toughening modifier, and 2 to 4 parts of interface modifier are added to a high-speed mixer and mixed for 10 to 15 minutes at a temperature of 100 to 120 degrees Celsius to obtain an inner layer modified mixture. The interface modifier is a compound of maleic anhydride-grafted polyethylene and epoxy fatty acid methyl ester, with a compounding mass ratio of 1:

1. Step 2: Preparation of thermal insulation foam material: By weight, 100 parts of PVC resin, 2 to 4 parts of heat stabilizer, 4 to 8 parts of foaming agent, 1 to 3 parts of foaming aid, 0.5 to 1.5 parts of nucleating agent, and 8 to 15 parts of nano-silica aerogel powder are added to a high-speed mixer and mixed for 8 to 12 minutes at a temperature of 80 to 100 degrees Celsius to obtain a thermal insulation foam mixture. The foaming agent is a compound of azodicarbonamide and sodium bicarbonate, with a mass ratio of 3:

1. The nano-silica aerogel powder has a particle size of 20 to 50 nanometers and a thermal conductivity of less than 0.020 W / m Kelvin. Step 3: Preparation of the outer protective material: By weight, take 100 parts of PVC resin, 3 to 5 parts of heat stabilizer, 1.5 to 3 parts of lubricant, 5 to 8 parts of weather-resistant modifier, 0.5 to 1 part of ultraviolet absorber, and 10 to 20 parts of reinforcing filler, put them into a high-speed mixer, and mix them for 10 to 15 minutes at a temperature of 110 to 130 degrees Celsius to obtain the outer protective mixture. Step 4: Integrated co-extrusion molding: The inner layer modified mixture obtained in step one is plasticized at a temperature of 170 to 190 degrees Celsius, the thermal insulation foamed mixture obtained in step two is plasticized at a temperature of 160 to 180 degrees Celsius, and the outer layer protective mixture obtained in step three is plasticized at a temperature of 175 to 195 degrees Celsius. The three plasticized melts are then fed to the same co-extrusion port through independent flow channels. The outlet temperature of the inner layer melt is controlled at 175 to 185 degrees Celsius, the outlet temperature of the thermal insulation layer melt is 165 to 175 degrees Celsius, and the outlet temperature of the outer layer melt is 180 to 190 degrees Celsius. The three melts are simultaneously extruded at the co-extrusion port to form a tubular preform in which the inner layer, thermal insulation layer, and outer layer are tightly composited from the inside out. Step 5: Vacuum shaping and foaming: The tubular preform obtained in step four is immediately introduced into a negative pressure environment, with the absolute pressure controlled at 0.06 to 0.09 MPa. A uniform negative pressure is applied to the outer wall of the preform, causing the outer wall to solidify under the negative pressure. Simultaneously, the foaming agent in the insulation layer decomposes and foams under the combined effect of the residual heat carried by the preform after extrusion in step four and the negative pressure environment, forming a uniform and dense closed-cell foam structure inside the insulation layer. The residence time of the tubular preform in the negative pressure environment is 30 to 90 seconds. Step Six: Cooling and Shaping The pipes processed in step five are sequentially introduced into three cooling media. The temperature of the first cooling media is 60 to 80 degrees Celsius, the temperature of the second cooling media is 30 to 50 degrees Celsius, and the temperature of the third cooling media is 15 to 25 degrees Celsius. The residence time of the pipes in each cooling media is 20 to 40 seconds, thus obtaining the modified PVC insulation pipe semi-finished product. Step 7, Traction and Online Testing: The semi-finished product obtained in step six is ​​pulled out at a traction speed of 0.5 to 2 meters per minute. During the traction process, the outer diameter of the pipe and the thickness of each layer are monitored online. The traction speed and the amount of melt supplied to each layer are adjusted according to the monitoring data to ensure that the thickness of each layer of the pipe is uniform. Finally, the pipe is cut to a fixed length according to the set length to obtain the finished modified PVC insulation pipe.

2. The integrated processing technology for modified PVC thermal insulation pipes according to claim 1, characterized in that, The toughening modifier mentioned in step one is a compound of chlorinated polyethylene and acrylonitrile butadiene styrene copolymer, with a compounding mass ratio of 2:

1.

3. The integrated processing technology for modified PVC thermal insulation pipes according to claim 1, characterized in that, Maleic anhydride-grafted polyethylene and epoxy fatty acid methyl ester are mixed in a 1:1 mass ratio and melt-mixed at a temperature of 80 to 100 degrees Celsius for 10 to 20 minutes. After cooling, the mixture is pulverized to 100 to 200 mesh.

4. The integrated processing technology for modified PVC thermal insulation pipes according to claim 1, characterized in that, The foaming agent mentioned in step two is a compound of azodicarbonamide and sodium bicarbonate with a mass ratio of 3:1; the foaming aid is a compound of zinc oxide and zinc stearate with a mass ratio of 1:

1.

5. The integrated processing technology for modified PVC thermal insulation pipes according to claim 1, characterized in that, The nano-silica aerogel powder mentioned in step two has a particle size of 20 to 50 nanometers and a thermal conductivity of less than 0.020 W / m Kelvin; the nucleating agent is nano-calcium carbonate with an average particle size of 100 to 300 nanometers.

6. The integrated processing technology for modified PVC thermal insulation pipes according to claim 1, characterized in that, The ultraviolet absorber is a benzotriazole ultraviolet absorber, and the reinforcing filler is light calcium carbonate that has been surface-treated with a silane coupling agent.

7. The integrated processing technology for modified PVC thermal insulation pipes according to claim 1, characterized in that, The plasticizing time of the three melts mentioned in step four is 2 to 6 minutes each.

8. The integrated processing technology for modified PVC thermal insulation pipes according to claim 1, characterized in that, The absolute pressure of the negative pressure environment described in step five is 0.07 to 0.08 MPa.

9. The integrated processing technology for modified PVC thermal insulation pipes according to claim 1, characterized in that, In step six, the three cooling media are all water, and each cooling medium is applied to the surface of the pipe by spraying.

10. The integrated processing technology for modified PVC thermal insulation pipes according to claim 1, characterized in that, The modified PVC insulation pipe produced by this process has an inner layer thickness of 1.5 to 3 mm, an insulation layer thickness of 5 to 15 mm, an outer layer thickness of 1.5 to 3 mm, and a total wall thickness of 8 to 21 mm. The insulation layer thickness accounts for 60% to 75% of the total wall thickness.

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