PERT prefabricated thermal insulation pipe and preparation method thereof

Abstract

The invention relates to the technical field of thermal insulation pipelines, and particularly discloses a PERT prefabricated thermal insulation pipe and a preparation method thereof. The PERT prefabricated thermal insulation pipe comprises an outer protective sleeve and a working inner pipe, the working inner pipe and the outer protective sleeve are connected through a polyurethane thermal insulation layer, and the working inner pipe is a PERT pipe; the outer sheath pipe comprises the following raw materials in parts by weight: 60-70 parts of modified polyethylene resin; 30 to 50 parts of EVA resin; 5-8 parts of carbon black; 3-8 parts of a silane coupling agent; 5-10 parts of an anti-ultraviolet agent; 1-5 parts of an antioxidant; 1-5 parts of an anti-aging agent; 1-5 parts of a stabilizer; the modified polyethylene resin is obtained by grafting butyl carbamate to polyethylene resin through irradiation; the anti-ultraviolet agent is obtained by modifying phenyl salicylate with diethanol amine. The prefabricated thermal insulation pipe has the advantage of being good in aging resistance.

Description

Technical Field

[0001] The present application relates to the technical field of thermal insulation pipes, and more specifically, to a PERT prefabricated thermal insulation pipe and a preparation method thereof. Background Art

[0002] In construction and municipal engineering, the performance of the pipeline system, as an important facility for conveying fluids, directly affects the operating efficiency and safety of the entire system. With the increasing requirements for energy conservation, emission reduction and environmental protection, traditional pipeline materials can no longer meet the needs of modern engineering in terms of insulation, corrosion resistance and aging resistance. PERT materials have been widely used in the field of pipeline manufacturing due to their excellent heat resistance, flexibility and processing performance. Especially in the field of prefabricated insulated pipes, PERT materials have become an ideal choice for the preparation of high-efficiency insulated pipes due to their excellent heat resistance and easy processing.

[0003] At present, the traditional PERT prefabricated insulated pipe is mainly composed of an inner PERT pipe, a middle insulation layer and an outer protective layer. Although this three-layer structure has improved the insulation performance and service life of the pipe to a certain extent, its aging resistance still needs to be improved. Especially in harsh environments such as ultraviolet radiation, high and low temperature alternation, and chemical corrosion, the pipe material is prone to aging, leading to performance degradation, embrittlement, cracking and other problems, which in turn affects the safety and service life of the pipe system. Therefore, the PERT prefabricated insulated pipe in the prior art has the defect of poor aging resistance. Summary of the invention

[0004] In order to enhance the aging resistance of a PERT prefabricated thermal insulation pipe, the present application provides a PERT prefabricated thermal insulation pipe and a preparation method thereof.

[0005] The PERT prefabricated insulation pipe provided in this application adopts the following technical solution: A PERT prefabricated insulation pipe, comprising an outer sheath pipe and a working inner pipe, wherein the working inner pipe and the outer sheath pipe are connected via a polyurethane insulation layer, and the working inner pipe is a PERT pipe; the outer sheath pipe comprises the following raw materials in parts by weight: 60-70 parts of modified polyethylene resin; 30-50 parts of EVA resin; Carbon black 5-8 parts; Silane coupling agent 3-8 parts; 5-10 parts of UV-resistant agent; 1-5 parts of antioxidant; 1-5 parts of anti-aging agent; 1-5 parts of stabilizer; The modified polyethylene resin is obtained by grafting butyl carbamate onto polyethylene resin through radiation; The anti-ultraviolet agent is obtained by modifying phenyl salicylate with diethanolamine.

[0006] By adopting the above technical solution, the polyethylene resin is modified and butyl carbamate is grafted to introduce butyl side chains into the polyethylene resin. Since the combination of the butyl side chain and the main chain has a very stable chemical structure, the outer sheath tube can be endowed with good aging resistance. In addition, since the butyl carbamate molecule contains carbamate groups, the nitrogen atoms in the carbamate groups can interact with oxygen atoms to form stable chemical bonds, thereby resisting the occurrence of oxidation reactions, thereby further enhancing the aging resistance of the outer sheath tube.

[0007] Phenyl salicylate itself has a certain ability to absorb ultraviolet light. However, when facing the application scenario of high-density outer sheath tube, its absorption efficiency of ultraviolet light is relatively low. This results in the outer sheath tube having poor anti-ultraviolet performance under ultraviolet light irradiation, and is prone to segmented aging caused by ultraviolet light. In order to improve this situation, the present application modifies phenyl salicylate by using diethanolamine. This treatment process aims to introduce amino and hydroxyl functional groups, thereby adding new photoreaction sites to the outer sheath tube material. These newly added photoreaction sites can enhance the rate or degree of photoreaction and effectively improve the material's ability to absorb ultraviolet light. Finally, the modified outer sheath tube exhibits enhanced aging resistance and better resistance to damage from ultraviolet light.

[0008] Optionally, the modified polyethylene resin is prepared by the following method: The first step: placing polyethylene resin particles and butyl carbamate in a radiation field, and subjecting them to high-energy irradiation treatment under nitrogen conditions, and obtaining an irradiated product after the irradiation time is 1-3 hours; Step 2: Add the irradiated product to ethanol, heat to 50-60°C and keep warm for 30-50 minutes, perform magnetic stirring during the insulation process, and then filter to obtain the grafted product, then wash the grafted product with ethanol, and then dry it to obtain the modified polyethylene resin.

[0009] By adopting the above technical solution, by irradiating the polyethylene resin particles and butyl carbamate in a high-energy radiation field, the functional groups of butyl carbamate can be effectively introduced into the polyethylene molecular chain to form a stable chemical bond. This irradiation method is not only easy to operate, but also can ensure the uniform distribution of functional groups in the polyethylene molecules, thereby improving the overall performance of the modified polyethylene resin. Irradiation treatment under nitrogen conditions can effectively prevent the polyethylene resin from oxidative degradation during the irradiation process and maintain its original excellent performance. Nitrogen, as an inert gas, can provide a stable irradiation environment to ensure the smooth progress of the modification process. After being treated by the above modification method, the performance of the polyethylene resin has been significantly improved. In particular, the modified polyethylene resin has shown better performance in aging resistance.

[0010] Optionally, the irradiation dose rate of the high energy radiation is 10.5-11.5 kGy·h -1 .

[0011] By adopting the above technical solution, a higher energy radiation dose can provide more energy in a short time, thereby accelerating the grafting reaction. This can shorten the reaction time and improve production efficiency. The high radiation dose rate can also produce a higher grafting density. The increase in grafting density can increase the bonding strength between the polyethylene molecules and the butyl carbamate monomers, thereby fully improving the stability of the modified polyethylene resin material, thereby ensuring product quality.

[0012] Optionally, the anti-ultraviolet agent is prepared by the following method: A. Add phenyl salicylate and diethanolamine to acetone, stir for 10-30 minutes, then add titanium chloride triisopropoxide, raise the temperature to 60-70° C., and react under reflux for 2-4 hours to obtain a reaction solution; B. The reaction solution is transferred to a rotary evaporator for rotary evaporation to obtain a reaction product, and the reaction product is washed and dried to obtain an anti-ultraviolet agent.

[0013] By adopting the above technical scheme, phenyl salicylate is modified by diethanolamine, and amino and hydroxyl groups are introduced, thereby adding new photoreaction sites, thereby enhancing the rate or degree of photoreaction. The adsorption capacity of ultraviolet light is improved, thereby enhancing the aging resistance of the outer sheath tube. During the modification process, triisopropanol titanium chloride is used as a catalyst to effectively promote the formation of coordination bonds between phenyl salicylate and amino and ester groups, thereby forming a stable reaction intermediate, reducing the activation energy of the reaction, and thus accelerating the reaction rate. The addition of the anti-ultraviolet agent significantly improves the ultraviolet resistance of the PERT prefabricated insulation pipe, and reduces the problems of material aging, embrittlement and cracking caused by ultraviolet light exposure. This is of great significance for extending the service life of the insulation pipe and improving the overall stability of the system.

[0014] Optionally, in step A, the mass ratio of phenyl salicylate, diethanolamine and acetone is 2:1:(5-10).

[0015] By adopting the above technical solution and reasonable raw material ratio, the stability and controllability of the preparation process of the UV-resistant agent are ensured. This refined control helps to maximize the performance of the UV-resistant agent.

[0016] Optionally, the amount of titanium chloride propoxide added in step A is 1%-5% of the mass of phenyl salicylate.

[0017] Optionally, the antioxidant is any one of pentaerythritol ester, disulfide and triphosphite.

[0018] By adopting the above technical solutions and selecting these excellent antioxidants, the aging resistance of PERT prefabricated insulation pipes is further improved. These antioxidants can effectively capture and remove free radicals, thereby delaying the oxidative degradation process of the material.

[0019] Optionally, the anti-aging agent is any one of Tinuvin 770 and benzotriazole.

[0020] By adopting the above technical solutions and selecting these excellent anti-aging agents, the light aging and heat aging resistance of PERT prefabricated insulation pipes are further enhanced. These anti-aging agents can effectively absorb and shield ultraviolet light, inhibit thermal oxidation degradation and other processes, thereby extending the service life of the material.

[0021] The present application also provides a method for preparing a PERT prefabricated thermal insulation pipe, which adopts the following technical solution: A method for preparing a PERT prefabricated thermal insulation pipe comprises the following steps: S1. The modified polyethylene resin, EVA resin, carbon black, silane coupling agent, UV inhibitor, antioxidant, anti-aging agent and stabilizer are uniformly mixed and then formed by an extruder to obtain an outer sheath pipe; S2. The outer sheath tube is placed on the working inner tube, and then polyurethane raw materials are poured between the working inner tube and the outer sheath tube to obtain a PERT prefabricated insulation tube after foaming and curing.

[0022] In summary, this application has the following beneficial effects: 1. The present application significantly improves the aging resistance of the insulation pipe by using modified polyethylene resin as the main raw material of the outer sheath pipe. The modified polyethylene resin is obtained by irradiating and grafting butyl carbamate on polyethylene resin. The carbamate group and butyl side chain in the butyl carbamate molecule give the polyethylene resin a more stable chemical structure. This structure not only enhances the mechanical properties of the material, but also enables it to resist the occurrence of oxidation reactions, thereby extending the service life of the material. In addition, a variety of additives such as UV inhibitors, antioxidants and anti-aging agents are added to the outer sheath pipe. These additives work synergistically to further enhance the light aging and heat aging resistance of the outer sheath pipe. Therefore, the PERT prefabricated insulation pipe of the present application can maintain stable performance even in harsh environments, reducing the maintenance and replacement costs caused by aging.

[0023] 2. The anti-ultraviolet agent in the present application is obtained by modifying phenyl salicylate with diethanolamine. This treatment process introduces amino and hydroxyl functional groups, adds new photoreaction sites, and thus improves the material's ability to adsorb ultraviolet light. This anti-ultraviolet agent can not only effectively absorb and shield ultraviolet light, but also convert the absorbed ultraviolet light energy into harmless heat or other forms of energy through photoreaction, thereby avoiding direct damage to the material by ultraviolet light. In addition, the addition of the anti-ultraviolet agent also reduces problems such as material aging, embrittlement and cracking caused by ultraviolet light irradiation, and further extends the service life of the insulation pipe. Therefore, the PERT prefabricated insulation pipe of the present application can also maintain stable performance in environments with high ultraviolet light intensity such as outdoors or in direct sunlight.

[0024] 3. The present application optimizes the component selection and preparation process of the outer sheath pipe to ensure the synergy between the components and the maximum improvement of the overall performance. Through reasonable raw material ratios and refined control, the uniform distribution and effective effect of additives such as UV inhibitors, antioxidants, and anti-aging agents in the material are achieved. At the same time, advanced preparation processes such as extruder basic molding and polyurethane foam curing are adopted to ensure the close connection between the outer sheath pipe and the working inner pipe and the stability of the overall structure. This optimized material ratio and preparation process not only improves the performance and quality of the insulation pipe, but also reduces production costs and energy consumption. Therefore, the PERT prefabricated insulation pipe of the present application also has significant advantages in terms of cost performance and environmental protection. DETAILED DESCRIPTION

[0025] The present application is further described in detail below with reference to the embodiments.

[0026] Preparation example of modified polyethylene resin Preparation Example 1 The modified polyethylene resin is prepared by the following method: Step 1: Mix polyethylene resin particles and butyl carbamate in a mass ratio of 1:0.3, then preheat at 80°C for 1h, and then place the mixture of polyethylene resin particles and butyl carbamate in a 60 High-energy irradiation treatment was carried out in a nitrogen atmosphere in the radiation field of Co-γ rays, with an irradiation dose rate of 10.5 kGy·h -1 , the irradiation product was obtained after irradiation for 3 h; Step 2: Add the irradiated product to ethanol, heat to 50°C and keep warm for 50 minutes. Perform magnetic stirring during the heat preservation process, and then filter to obtain the grafted product. Then, wash the grafted product with ethanol and dry it to obtain the modified polyethylene resin.

[0027] Preparation Example 2 The modified polyethylene resin is prepared by the following method: Step 1: Mix polyethylene resin particles and butyl carbamate in a mass ratio of 1:0.3, then preheat at 80°C for 1h, and then place the mixture of polyethylene resin particles and butyl carbamate in a 60 High-energy irradiation treatment was carried out in a nitrogen atmosphere in the radiation field of Co-γ rays, with an irradiation dose rate of 11.0 kGy·h -1 , the irradiation product was obtained after irradiation for 2 h; Step 2: Add the irradiated product to ethanol, heat to 55°C and keep warm for 40 minutes. Perform magnetic stirring during the heat preservation process, and then filter to obtain the grafted product. The grafted product is then washed with ethanol and dried to obtain the modified polyethylene resin.

[0028] Preparation Example 3 The modified polyethylene resin is prepared by the following method: Step 1: Mix polyethylene resin particles and butyl carbamate in a mass ratio of 1:0.3, then preheat at 80°C for 1h, and then place the mixture of polyethylene resin particles and butyl carbamate in a 60 High-energy irradiation treatment was carried out in a nitrogen atmosphere in the radiation field of Co-γ rays, with an irradiation dose rate of 11.5 kGy·h -1 , the irradiation product was obtained after irradiation for 1 h; Step 2: Add the irradiated product to ethanol, heat to 60°C and keep warm for 30 minutes. Perform magnetic stirring during the heat preservation process, and then filter to obtain the grafted product. Then, wash the grafted product with ethanol and dry it to obtain the modified polyethylene resin.

[0029] Preparation Example 4 The difference between the modified polyethylene resin and Preparation Example 3 is that the irradiation dose rate in this Preparation Example is 2.5 kGy·h-1 .

[0030] Preparation Example 5 The modified polyethylene resin is different from Preparation Example 3 in that an equal amount of methyl acrylate is used instead of butyl carbamate as a monomer for grafting reaction in this Preparation Example.

[0031] Preparation example of UV-resistant agent Preparation Example 6 The anti-ultraviolet agent is prepared by the following method: A. Add 20 g of phenyl salicylate and 10 g of diethanolamine to 50 g of acetone, stir for 10 min, then add 0.2 g of titanium chloride triisopropoxide, heat to 60° C., and react under reflux for 4 h to obtain a reaction solution; B. The reaction solution is transferred to a rotary evaporator for rotary evaporation to obtain a reaction product, and the reaction product is washed and dried to obtain an anti-ultraviolet agent.

[0032] Preparation Example 7 The anti-ultraviolet agent is prepared by the following method: A. Add 20 g of phenyl salicylate and 10 g of diethanolamine to 80 g of acetone, stir for 20 min, then add 0.6 g of titanium triisopropoxide chloride, heat to 65 ° C, and react under reflux for 3 h to obtain a reaction solution; B. The reaction solution is transferred to a rotary evaporator for rotary evaporation to obtain a reaction product, and the reaction product is washed and dried to obtain an anti-ultraviolet agent.

[0033] Preparation Example 8 The anti-ultraviolet agent is prepared by the following method: A. Add 20 g of phenyl salicylate and 10 g of diethanolamine to 100 g of acetone, stir for 30 min, then add 1.0 g of titanium chloride triisopropoxide, heat to 70° C., and react under reflux for 2 h to obtain a reaction solution; B. The reaction solution is transferred to a rotary evaporator for rotary evaporation to obtain a reaction product, and the reaction product is washed and dried to obtain an anti-ultraviolet agent.

[0034] Preparation Example 9 The difference between the anti-ultraviolet agent and Preparation Example 8 is that an equal amount of triethylamine is used instead of triisopropoxytitanium chloride as a catalyst in this embodiment.

[0035] Example Example 1 A PERT prefabricated thermal insulation pipe comprises an outer sheath pipe and a working inner pipe, wherein the working inner pipe and the outer sheath pipe are connected by a polyurethane thermal insulation layer, and the working inner pipe is a PERT pipe; the original components and dosages of the outer sheath pipe are shown in Table 1, wherein the modified polyethylene resin is the modified polyethylene resin prepared in Preparation Example 1; the anti-ultraviolet agent is the anti-ultraviolet agent prepared in Preparation Example 6; the antioxidant is pentaerythritol ester; the anti-aging agent is Tinuvin 770; and the stabilizer is a calcium zinc stabilizer.

[0036] A PERT prefabricated thermal insulation pipe is prepared by the following method: S1. The modified polyethylene resin, EVA resin, carbon black, silane coupling agent, UV inhibitor, antioxidant, anti-aging agent and stabilizer are uniformly mixed and then formed by an extruder to obtain an outer sheath pipe; S2. The outer sheath tube is placed on the working inner tube, and then polyurethane raw materials are poured between the working inner tube and the outer sheath tube to obtain a PERT prefabricated insulation tube after foaming and curing.

[0037] Example 2 A PERT prefabricated thermal insulation pipe comprises an outer sheath pipe and a working inner pipe, wherein the working inner pipe and the outer sheath pipe are connected via a polyurethane thermal insulation layer, and the working inner pipe is a PERT pipe; the original components and dosages of the outer sheath pipe are shown in Table 1, wherein the modified polyethylene resin is the modified polyethylene resin prepared in Preparation Example 2; the anti-ultraviolet agent is the anti-ultraviolet agent prepared in Preparation Example 6; the antioxidant is disulfide; the anti-aging agent is benzotriazole; and the stabilizer is a calcium zinc stabilizer.

[0038] A PERT prefabricated thermal insulation pipe is prepared by the following method: S1. The modified polyethylene resin, EVA resin, carbon black, silane coupling agent, UV inhibitor, antioxidant, anti-aging agent and stabilizer are uniformly mixed and then formed by an extruder to obtain an outer sheath pipe; S2. The outer sheath tube is placed on the working inner tube, and then polyurethane raw materials are poured between the working inner tube and the outer sheath tube to obtain a PERT prefabricated insulation tube after foaming and curing.

[0039] Example 3 A PERT prefabricated thermal insulation pipe comprises an outer sheath pipe and a working inner pipe, wherein the working inner pipe and the outer sheath pipe are connected by a polyurethane thermal insulation layer, and the working inner pipe is a PERT pipe; the original components and dosages of the outer sheath pipe are shown in Table 1, wherein the modified polyethylene resin is the modified polyethylene resin prepared in Preparation Example 3; the anti-ultraviolet agent is the anti-ultraviolet agent prepared in Preparation Example 6; the antioxidant is triphosphite; the anti-aging agent is benzotriazole; and the stabilizer is a calcium zinc stabilizer.

[0040] A PERT prefabricated thermal insulation pipe is prepared by the following method: S1. The modified polyethylene resin, EVA resin, carbon black, silane coupling agent, UV inhibitor, antioxidant, anti-aging agent and stabilizer are uniformly mixed and then formed by an extruder to obtain an outer sheath pipe; S2. The outer sheath tube is placed on the working inner tube, and then polyurethane raw materials are poured between the working inner tube and the outer sheath tube to obtain a PERT prefabricated insulation tube after foaming and curing.

[0041] Table 1 Raw material components and dosage of the outer sheath pipe of the thermal insulation pipe in Examples 1-3 (kg)

[0042] Example 4 A PERT prefabricated thermal insulation pipe, which is different from Example 3 in that the anti-ultraviolet agent in this example is the anti-ultraviolet agent prepared in Preparation Example 7.

[0043] Example 5 A PERT prefabricated thermal insulation pipe, which is different from Example 3 in that the anti-ultraviolet agent in this example is the anti-ultraviolet agent prepared in Preparation Example 8.

[0044] Example 6 A PERT prefabricated thermal insulation pipe, which is different from Example 3 in that the anti-ultraviolet agent in this example is the anti-ultraviolet agent prepared in Preparation Example 9.

[0045] Example 7 A PERT prefabricated insulation pipe, which is different from Example 3 in that the modified polyethylene resin in this example is the modified polyethylene resin prepared in Preparation Example 4.

[0046] Comparative Example Comparative Example 1 A PERT prefabricated insulation pipe, which is different from Example 3 in that an equal amount of unmodified polyethylene resin is used in the raw materials of this comparative example to replace the modified polyethylene resin.

[0047] Comparative Example 2 A PERT prefabricated thermal insulation pipe, which is different from Example 3 in that the modified polyethylene resin in this example is the modified polyethylene resin prepared in Preparation Example 5.

[0048] Comparative Example 3 A PERT prefabricated insulation pipe, which is different from Example 3 in that an equal amount of phenyl salicylate is used to replace the anti-ultraviolet agent in this comparative example.

[0049] Performance testing Detection Methods Step 1. First, the thermal conductivity and impact strength of the insulation pipes in Examples 1-7 and Comparative Examples 1-3 are respectively tested, wherein the thermal conductivity test method is carried out in accordance with GB / T3399-1982 "Test method for thermal conductivity of plastics - guarded flat plate method"; the compressive strength test method is carried out in accordance with GB / T8813-2020 "Determination of compression properties of rigid foam plastics".

[0050] Step 2: Place the insulation pipes in Examples 1-7 and Comparative Examples 1-3 in an aging test chamber, respectively. The temperature in the aging test chamber is set to 85°C, the relative humidity is 35%, and the ultraviolet light is turned on to simulate sunlight irradiation. The ultraviolet light intensity is 100mW / m², and the aging treatment is carried out in the aging test chamber for 1000h. Then, the thermal conductivity and impact strength of the insulation pipe after aging are tested according to the method in Step 1. The test results are shown in Table 2.

[0051] Table 2 Test results

[0052] It can be seen from Examples 1-5 and Table 2 that the changes in thermal conductivity and compressive strength of the thermal insulation pipe of the present application before and after the aging test are relatively small, indicating that the thermal insulation pipe provided in the embodiments of the present application has good aging resistance.

[0053] From the combination of Example 3, Example 6 and Table 2, it can be seen that since Example 6 adopts the anti-ultraviolet agent prepared in Preparation Example 9, the thermal conductivity and compressive strength of the insulation pipe of Example 6 change greatly before and after the aging test, which means that the insulation performance and compressive strength of the insulation pipe of Example 6 are greatly lost after the aging test. Therefore, the aging resistance of the insulation pipe of Example 6 is lower than that of the insulation pipe of Example 3.

[0054] From Example 3, Example 7 and Table 2, it can be seen that, since Example 6 adopts the modified polyethylene resin prepared in Preparation Example 4, the thermal conductivity and compressive strength of the insulation pipe of Example 6 change greatly before and after the aging test, indicating that the thermal insulation performance and compressive strength of the insulation pipe of Example 6 lose a lot after the aging test, indicating that the irradiation dose rate of the modified polyethylene resin during the modification process has a certain degree of influence on the aging resistance of the modified polyethylene resin.

[0055] Combining Example 3, Comparative Example 1 and Table 2, it can be seen that the thermal conductivity and compressive strength loss of the insulation pipe of Comparative Example 1 before and after the aging test significantly increase, indicating that the aging resistance of conventional polyethylene resin is poor.

[0056] From Example 3, Comparative Example 2 and Table 2, it can be seen that since Comparative Example 2 uses the modified polyethylene resin prepared in Preparation Example 5, the thermal conductivity and compressive strength of the insulation pipe of Comparative Example 2 show a significant increase in loss before and after the aging test, indicating that the effect of using methacrylate to modify polyethylene is not as good as that of butyl carbamate.

[0057] Combining Example 3, Comparative Example 3 and Table 2, it can be seen that since Comparative Example 3 directly uses phenyl salicylate as an anti-ultraviolet agent, the thermal conductivity and compressive strength of the insulation pipe of Comparative Example 3 before and after the aging test are significantly increased, indicating that the absorption capacity of phenyl salicylate directly used for ultraviolet light is not as good as that of the modified phenyl salicylate.

[0058] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A PERT prefabricated insulation pipe, characterized in that: It includes an outer sheath tube and a working inner tube, wherein the working inner tube and the outer sheath tube are connected by a polyurethane insulation layer, and the working inner tube is a PERT tube; the outer sheath tube includes the following raw materials in parts by weight: 60-70 parts of modified polyethylene resin; 30-50 parts of EVA resin; Carbon black 5-8 parts; Silane coupling agent 3-8 parts; 5-10 parts of UV-resistant agent; 1-5 parts of antioxidant; 1-5 parts of anti-aging agent; 1-5 parts of stabilizer; The modified polyethylene resin is obtained by grafting butyl carbamate onto polyethylene resin through radiation; The anti-ultraviolet agent is obtained by modifying phenyl salicylate with diethanolamine.

2. A PERT prefabricated thermal insulation pipe according to claim 1, characterized in that: The modified polyethylene resin is prepared by the following method: The first step: placing polyethylene resin particles and butyl carbamate in a radiation field, and subjecting them to high-energy irradiation treatment under nitrogen conditions, and obtaining an irradiated product after the irradiation time is 1-3 hours; Step 2: Add the irradiated product to ethanol, heat to 50-60°C and keep warm for 30-50 minutes, perform magnetic stirring during the insulation process, and then filter to obtain the grafted product, then wash the grafted product with ethanol, and then dry it to obtain the modified polyethylene resin.

3. A PERT prefabricated thermal insulation pipe according to claim 2, characterized in that: The irradiation dose rate of the high energy irradiation treatment is 10.5-11.5 kGy·h -1 .

4. The PERT prefabricated thermal insulation pipe according to claim 1, characterized in that: The anti-ultraviolet agent is prepared by the following method: A. Add phenyl salicylate and diethanolamine to acetone, stir for 10-30 minutes, then add titanium chloride triisopropoxide, raise the temperature to 60-70° C., and react under reflux for 2-4 hours to obtain a reaction solution; B. The reaction solution is transferred to a rotary evaporator for rotary evaporation to obtain a reaction product, and the reaction product is washed and dried to obtain an anti-ultraviolet agent.

5. The PERT prefabricated thermal insulation pipe according to claim 4, characterized in that: In step A, the mass ratio of phenyl salicylate, diethanolamine and acetone is 2:1:(5-10).

6. The PERT prefabricated thermal insulation pipe according to claim 4, characterized in that: In step A, the amount of titanium chloride propoxide added is 1%-5% of the mass of phenyl salicylate.

7. The PERT prefabricated thermal insulation pipe according to claim 1, characterized in that: The antioxidant is any one of pentaerythritol ester, disulfide and triphosphite.

8. The PERT prefabricated thermal insulation pipe according to claim 1, characterized in that: The anti-aging agent is any one of Tinuvin 770 and benzotriazole.

9. A method for preparing a PERT prefabricated thermal insulation pipe according to any one of claims 1 to 8, characterized in that: The steps include: S1. The modified polyethylene resin, EVA resin, carbon black, silane coupling agent, UV inhibitor, antioxidant, anti-aging agent and stabilizer are uniformly mixed and then formed by an extruder to obtain an outer sheath pipe; S2. The outer sheath tube is placed on the working inner tube, and then polyurethane raw materials are poured between the working inner tube and the outer sheath tube to obtain a PERT prefabricated insulation tube after foaming and curing.

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