Polymer blend of anti-aging PE (polyethylene) pipe for municipal engineering

Abstract

The invention relates to the technical field of high polymer material synthesis, in particular to a high polymer blend of an anti-aging PE (polyethylene) pipe for municipal engineering, which comprises 40-60 parts of LLDPE (linear low density polyethylene) as a base, 20-30 parts of novel anti-aging functional polymer with hindered amine and self-repairing disulfide bond structure and 5-10 parts of nano titanium dioxide / graphene composite filler loaded with silver nanoparticles. And the plasticizer, the compound antioxidant, the microcapsule light stabilizer and the like are matched, so that all the components synergistically improve the performance. The blend disclosed by the invention has the advantages of remarkable aging resistance, capability of self-repairing microcracks, enhanced mechanical and antibacterial properties, capability of monitoring aging damage, good processability and capability of reducing maintenance, prolonging the service life of the PE pipe in municipal engineering and guaranteeing stable operation of a municipal system.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material synthesis, and specifically to a polymer blend for anti-aging PE pipes used in municipal engineering. Background Art

[0002] In the field of municipal engineering, PE pipes are widely used in water supply, drainage, and gas transmission systems due to their good corrosion resistance, flexibility, and easy processability. However, during long-term use, ordinary PE pipes are prone to aging under the influence of factors such as ultraviolet rays, temperature changes, chemical substance erosion, and mechanical stress, greatly shortening their service life and increasing maintenance costs and safety hazards.

[0003] Ultraviolet rays are one of the important factors causing the aging of PE pipes. Under ultraviolet irradiation, polymer molecules in ordinary PE pipes are prone to photo-oxidation reactions, generating free radicals, which trigger the breakage and cross-linking of molecular chains, making the pipe brittle and reducing its strength. Traditional anti-aging measures mostly use the addition of conventional light stabilizers, but the effect is limited, and it is difficult to resist ultraviolet damage for a long time. For example, in some outdoor municipal water supply pipeline projects, PE pipes using conventional light stabilizers showed obvious aging signs after 2-3 years, with cracks on the surface and a decrease in compressive capacity.

[0004] Temperature changes also have a significant impact on PE pipes. In cold regions, the low temperature in winter makes PE pipes hard and brittle, and their impact resistance is greatly reduced, making them prone to rupture due to internal water pressure or external impact; in hot regions, the high temperature in summer accelerates the movement of molecular chains, promotes oxidation reactions, and intensifies the aging process. Most PE pipes on the market at present are difficult to adapt to a large temperature span and cannot meet the long-term stable use requirements of municipal engineering under different climate conditions.

[0005] Chemical substance erosion also threatens the life of PE pipes. Acid-base substances contained in municipal sewage, heavy metal ions and corrosive organic substances in industrial wastewater, etc., after contacting with PE pipes, will enter the pipe interior through penetration, diffusion, etc., and react chemically with polymer molecules, destroying the molecular structure and causing the deterioration of pipe performance. In some municipal drainage projects in industrial agglomeration areas, ordinary PE pipes showed serious leakage problems due to chemical corrosion within less than 1 year.

[0006] In terms of mechanical stress, operations such as stretching, bending, and extrusion during municipal construction, as well as the internal pressure and soil pressure that the pipeline bears for a long time, will cause micro-cracks inside the PE pipe. These cracks gradually expand under long-term stress, eventually leading to the failure of the pipe. Traditional PE pipes lack an effective self-repair mechanism. Once micro-cracks appear, the aging speed will accelerate. Summary of the Invention

[0007] (I) Technical Problems to be Solved Aiming at the deficiencies of the prior art, the present invention provides a polymer blend for anti-aging PE pipes used in municipal engineering.

[0008] (II) Technical Solution The polymer blend for anti-aging PE pipes used in municipal engineering is composed of the following components: 40-60 parts of linear low-density polyethylene (LLDPE); 20-30 parts of a novel anti-aging functional polymer, which is copolymerized from vinyltrimethoxysilane and 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, and a disulfide bond with self-healing function is introduced into the molecular main chain, and its chemical structure is: ;

[0009] The disulfide bond is introduced with 3,3'-dithiobis(propionic acid) dimethyl ester as the raw material, and the 4-acryloyloxy-2,2,6,6-tetramethylpiperidine is synthesized by demethylation from 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine, and the CAS number of 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine is 15051-46-4; 5-10 parts of nano-titanium dioxide / graphene composite filler, wherein the particle size of nano-titanium dioxide is 20-50 nm, the thickness of graphene sheets is 1-2 nm, and silver nanoparticles with photocatalytic antibacterial function are further loaded on the surface of nano-titanium dioxide; nano-titanium dioxide and graphene are compounded through a surface-modified silane coupling agent γ-aminopropyltriethoxysilane, and one end of the silane coupling agent reacts with the surface hydroxyl groups of nano-titanium dioxide, and the other end of the amino group reacts with the oxygen-containing functional groups on the surface of graphene; 3-8 parts of plasticizer, poly(propylene adipate) (PPA) is selected, and a hydroxyl group capable of forming hydrogen bonds with the polymer matrix is introduced into its molecular structure; 1-3 parts of antioxidant, which is composed of a main antioxidant pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] 1010 and a co-antioxidant triphenyl phosphite (TPP) in a mass ratio of 2:1, and 0.1%-0.3% by mass of a metal ion chelating agent ethylenediaminetetraacetic acid disodium (EDTA-2Na) is added; 1-3 parts of light stabilizer, a novel hindered amine light stabilizer bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate is used, and it is microencapsulated, and the microcapsule wall material is biodegradable polylactic acid (PLA) with a particle size of 1-5 μm.

[0010] Preferably, it further includes 0.5-1 part of an intelligent color-changing indicator; the indicator is an organic compound containing a spiropyran structure. When the PE pipe undergoes severe aging or is damaged, its molecular structure changes, resulting in a color change, which is convenient for timely detecting problems of the PE pipe; through a specific synthesis process, it is evenly dispersed in the blend and has good compatibility with the polymer matrix.

[0011] Preferably, it further includes adding carbon nanotubes with a mass fraction of 0.05% - 0.1% during the preparation of the blend; these carbon nanotubes are surface carboxylated and can form a three-dimensional network structure with the nano-titanium dioxide / graphene composite filler and the polymer matrix, further enhancing the mechanical properties and electrical conductivity of the blend, and can be used to monitor the stress and damage conditions of pipelines in municipal engineering.

[0012] Preferably, the molar ratio of vinyltrimethoxysilane to 4-acryloyloxy-2,2,6,6-tetramethylpiperidine in the novel anti-aging functional polymer is 3:1 - 5:1; the content of dynamic covalent bond disulfide bonds in the polymer is 0.5% - 1.5%.

[0013] Preferably, in the nano-titanium dioxide / graphene composite filler, the mass ratio of nano-titanium dioxide to graphene is 2:1 - 3:1; the loading amount of silver nanoparticles on the surface of nano-titanium dioxide is 1% - 3%.

[0014] Preferably, the number average molecular weight of the novel environmentally friendly polyester plasticizer poly(propylene adipate) is 2000 - 3000; the content of hydroxyl groups introduced into its molecular structure is 0.5 mmol / g - 1 mmol / g.

[0015] Preferably, a method for preparing the polymer blend for the anti-aging PE pipe used in municipal engineering includes the following steps: S1: Raw material pretreatment: Dry linear low-density polyethylene at 80 - 100 °C for 2 - 3 hours to remove moisture; vacuum dry the nano-titanium dioxide / graphene composite filler at 120 - 150 °C for 3 - 4 hours to improve its dispersibility; perform surface carboxylation treatment on the carbon nanotubes. Add the carbon nanotubes to a mixed acid of concentrated sulfuric acid: concentrated nitric acid = 3:1, stir and react at 50 - 60 °C for 2 - 3 hours, then wash with deionized water until neutral, and dry at 80 - 100 °C for standby; S2: Synthesis of the novel anti-aging functional polymer: Add an appropriate amount of vinyltrimethoxysilane, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, initiator, and organic solvent to the reaction kettle. After purging the air with nitrogen, heat up to 70 - 80 °C and react for 4 - 6 hours. Add a crosslinking agent containing disulfide bonds, dimethyl 3,3'-dithiobispropionate, for copolymerization in the later stage of the reaction to synthesize the novel anti-aging functional polymer; after the reaction is completed, remove the organic solvent by vacuum distillation to obtain the product; S3: Mixing and Stirring: Add the dried linear low-density polyethylene, synthesized novel anti-aging functional polymer, nano-titanium dioxide / graphene composite filler, plasticizer, compound antioxidant, light stabilizer, intelligent color-changing indicator, and carbon nanotubes into a high-speed mixer in proportion, and mix for 10 - 15 minutes at a rotation speed of 150 - 200 r / min to preliminarily mix all components evenly; during the mixing process, control the temperature at 40 - 50 °C to prevent the material from degrading due to heat generated by friction; S4: Melt Blending: Transfer the preliminarily mixed material to a twin-screw extruder, set the temperature of each section of the extruder at 160 - 200 °C, and the screw rotation speed at 200 - 300 r / min for melt blending; after the material undergoes sufficient shearing and mixing in the extruder, it is extruded and pelletized to obtain polymer blend pellets for anti-aging PE pipes used in municipal engineering.

[0016] Preferably, in step S2, the dosage of initiator azobisisobutyronitrile is 0.5% - 1% of the total mass of the monomers, the dosage of organic solvent toluene is 1 - 2 times the total volume of the monomers; the dosage of the cross-linking agent containing disulfide bonds is 0.5% - 1% of the total mass of the monomers.

[0017] Preferably, in step S3, the mixing chamber of the high-speed mixer adopts a jacket structure to control the mixing temperature through circulating water; during the mixing process, an ultrasonic-assisted dispersion technology is adopted, with an ultrasonic frequency of 20 - 30 kHz and a power of 100 - 200 W to promote the uniform dispersion of each component.

[0018] Preferably, in step S4, the length-diameter ratio of the twin-screw extruder is 30:1 - 40:1, with good mixing effect to ensure that each component is evenly dispersed in the blend; during the extrusion process, an on-line quality monitoring system is adopted to monitor the melt flow rate and density of the blend in real time to ensure the stable quality of the product.

[0019] (III) Beneficial Technical Effects Compared with the existing technology, the beneficial effects of the present invention are: 1. The hindered amine groups in the novel anti-aging functional polymer can efficiently capture free radicals, inhibit the degradation of molecular chains, and the dynamic covalent bonds can achieve self-repair of microcracks, greatly extending the service life of PE pipes. Through accelerated aging experiment tests, the aging time of PE pipes using the blend of the present invention is greatly extended compared with ordinary PE pipes.

[0020] 2. The nano-titanium dioxide / graphene composite filler and the loaded silver nanoparticles synergistically enhance the mechanical properties, endow the pipe with antibacterial function, reduce microbial corrosion, and are especially suitable for environments such as sewage transportation. In the simulated sewage environment test, the amount of microbial adhesion on the surface of this pipe is greatly reduced compared with ordinary pipes, and the compressive strength is improved.

[0021] 3. The plasticizer introduces hydrogen-bond functional groups, which can improve the processing fluidity without reducing the anti-aging performance, ensuring a smooth production process and stable product quality. The compound antioxidant and metal ion chelating agent act synergistically to effectively inhibit the oxidation reaction. The microencapsulation treatment of the light stabilizer prolongs the action time and further enhances the anti-aging effect.

[0022] 4. The addition of the intelligent color-changing indicator and carbon nanotubes endows the PE pipe with a self-monitoring function. When the pipe ages or is damaged, the indicator changes color to remind maintenance. The three-dimensional network structure formed by the carbon nanotubes enhances the mechanical and electrical properties, facilitating the monitoring of pipeline stress and damage through electrical methods. Generally speaking, the polymer blend of the present invention comprehensively improves the performance of PE pipes in municipal engineering, reduces the maintenance cost, and ensures the stable operation of the municipal system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart of the polymer blend for the anti-aging PE pipe used in municipal engineering proposed by the present invention; Figure 2 is a line comparison chart of the tensile strength and the retention rate of tensile strength after aging of the examples and comparative examples; Figure 3 is a column comparison chart of the antibacterial rates of the examples and comparative examples; Figure 4 is a line comparison chart of the elongation at break of the examples and comparative examples; Figure 5 is the nuclear magnetic resonance hydrogen spectrum of dimethyl 3,3'-dithiobispropionate. DETAILED DESCRIPTION OF THE INVENTION

[0024] According to Figures 1 to 5 , the detailed implementation manners of the present invention are as follows: Examples

[0025] Raw material preparation: Prepare 40 parts of linear low density polyethylene (LLDPE); 20 parts of a new anti-aging functional polymer, in which the molar ratio of vinyltrimethoxysilane to 4-acryloyloxy-2,2,6,6-tetramethylpiperidine is 3:1, and the content of dynamic covalent bond disulfide bond is 0.5% (mole fraction); 5 parts of nano-titanium dioxide / graphene composite filler, the mass ratio of nano-titanium dioxide to graphene is 2:1, and the silver nanoparticle loading is 1% (mass fraction); 3 parts of plasticizer, the number average molecular weight of poly(propylene adipate) is 2000, and the hydroxyl content is 0.5 mmol / g; 1 part of antioxidant, the mass ratio of the main antioxidant pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] to the auxiliary antioxidant triphenyl phosphite is 2:1, and 0.1% (mass fraction) of disodium ethylenediaminetetraacetate is added; 1 part of light stabilizer, which is microencapsulated bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, and the microcapsule particle size is 1 μm; 0.5 part of intelligent color-changing indicator; 0.05 part of carbon nanotubes, which are surface carboxylated.

[0026] Raw material pretreatment: Dry LLDPE at 80 °C for 3 hours; vacuum dry the nano-titanium dioxide / graphene composite filler at 120 °C for 4 hours; add carbon nanotubes to a mixed acid (concentrated sulfuric acid: concentrated nitric acid = 3:1), stir and react at 50 °C for 3 hours, then wash with deionized water until neutral, and dry at 80 °C for standby.

[0027] Synthesis of new anti-aging functional polymer: Add vinyltrimethoxysilane, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, initiator azobisisobutyronitrile (dosage is 0.5% of the total mass of monomers) and organic solvent toluene (dosage is 1 times the total volume of monomers) into the reaction kettle. After purging the air with nitrogen, heat up to 70 °C and react for 6 hours. In the later stage of the reaction, add a cross-linking agent containing disulfide bonds (dosage is 0.5% of the total mass of monomers) for copolymerization. After the reaction is completed, remove the organic solvent by vacuum distillation to obtain the product.

[0028] Mixing and stirring: Add the above pretreated raw materials into a high-speed mixer in proportion, mix at a speed of 150 r / min for 15 minutes, control the temperature at 40 °C during the mixing process, and adopt ultrasonic-assisted dispersion technology with an ultrasonic frequency of 20 kHz and a power of 100 W.

[0029] Melt blending: Transfer the preliminarily mixed materials to a twin-screw extruder, set the temperature of each section of the extruder at 160 °C, and the screw speed at 200 r / min for melt blending and extrusion granulation to obtain polymer blend particles for anti-aging PE pipes used in municipal engineering. Example

[0030] Raw material preparation: 50 parts of linear low density polyethylene (LLDPE); 25 parts of a new anti-aging functional polymer, with a molar ratio of vinyltrimethoxysilane to 4-acryloyloxy-2,2,6,6-tetramethylpiperidine of 4:1 and a dynamic covalent bond disulfide bond content of 1% (mole fraction); 7 parts of nano-titanium dioxide / graphene composite filler, with a mass ratio of nano-titanium dioxide to graphene of 2.5:1 and a silver nanoparticle loading of 2% (mass fraction); 5 parts of plasticizer, poly(propylene adipate) with a number average molecular weight of 2500 and a hydroxyl content of 0.75 mmol / g; 2 parts of antioxidant, with a mass ratio of primary antioxidant to secondary antioxidant of 2:1, and 0.2% (mass fraction) of disodium ethylenediaminetetraacetate added; 2 parts of light stabilizer, microencapsulated bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, with a microcapsule particle size of 3 μm; 0.7 part of intelligent color-changing indicator; 0.07 part of carbon nanotubes, which have been surface carboxylated.

[0031] Raw material pretreatment: LLDPE is dried at 90 °C for 2.5 hours; the nano-titanium dioxide / graphene composite filler is vacuum dried at 135 °C for 3.5 hours; the carbon nanotubes are carboxylated according to the method of Example 1.

[0032] Synthesis of new anti-aging functional polymer: The amount of initiator azobisisobutyronitrile is 0.7% of the total mass of the monomers, the amount of organic solvent toluene is 1.5 times the total volume of the monomers, the reaction is carried out at 75 °C for 5 hours, and a disulfide bond cross-linking agent (the amount is 0.7% of the total mass of the monomers) is added later.

[0033] Mixing and stirring: Mix at a speed of 175 r / min for 12 minutes, control the temperature at 45 °C, the ultrasonic frequency at 25 kHz, and the power at 150 W.

[0034] Melt blending: The temperature of each section of the extruder is 180 °C, and the screw speed is 250 r / min. Example

[0035] Raw material preparation: 60 parts of linear low density polyethylene (LLDPE); 30 parts of a new anti-aging functional polymer, with the molar ratio of vinyltrimethoxysilane to 4-acryloyloxy-2,2,6,6-tetramethylpiperidine being 5:1 and the content of dynamic covalent bond disulfide bond being 1.5% (mole fraction); 10 parts of nano-titanium dioxide / graphene composite filler, with the mass ratio of nano-titanium dioxide to graphene being 3:1 and the silver nanoparticle loading being 3% (mass fraction); 8 parts of plasticizer, the number average molecular weight of poly(propylene adipate) being 3000 and the hydroxyl content being 1 mmol / g; 3 parts of antioxidant, with the mass ratio of primary antioxidant to secondary antioxidant being 2:1, and 0.3% (mass fraction) of disodium ethylenediaminetetraacetate being added; 3 parts of light stabilizer, microencapsulated bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, with the microcapsule particle size being 5 μm; 1 part of intelligent color-changing indicator; 0.1 part of carbon nanotubes, which have been surface carboxylated.

[0036] Raw material pretreatment: LLDPE is dried at 100 °C for 2 hours; the nano-titanium dioxide / graphene composite filler is vacuum dried at 150 °C for 3 hours; the treatment method of carbon nanotubes is the same as that in Example 1.

[0037] Synthesis of new anti-aging functional polymer: The dosage of initiator azobisisobutyronitrile is 1% of the total mass of monomers, the dosage of organic solvent toluene is 2 times the total volume of monomers, the reaction is carried out at 80 °C for 4 hours, and a disulfide bond crosslinking agent (dosage is 1% of the total mass of monomers) is added later.

[0038] Mixing and stirring: Mix at a rotation speed of 200 r / min for 10 minutes, control the temperature at 50 °C, the ultrasonic frequency at 30 kHz, and the power at 200 W.

[0039] Melt blending: The temperature of each section of the extruder is 200 °C, and the screw rotation speed is 300 r / min.

[0040] Comparative example Using the ordinary PE pipe preparation method, the raw material is only linear low density polyethylene, and conventional light stabilizers and antioxidants are added, without adding the new anti-aging functional polymer, nano-titanium dioxide / graphene composite filler, intelligent color-changing indicator, carbon nanotubes and other components in the present invention. The PE pipe is prepared according to the traditional mixing and melt extrusion process.

[0041] Comparison of the tensile strength and elongation at break of the PE pipes in the examples and comparative example is as follows in the table: Item Example 1 Example 2 Example 3 Comparative Example Tensile strength (MPa) 25 28 30 18 Elongation at break (%) 600 650 700 400 Table 1 Conclusion: The table clearly shows that the examples are significantly superior to the comparative examples in terms of tensile strength and elongation at break. The tensile strength of the examples is between 25 MPa and 30 MPa, while that of the comparative example is only 18 MPa; the elongation at break of the examples is between 600% and 700%, and that of the comparative example is 400%. This indicates that the PE pipes prepared from the polymer blend of the present invention have better mechanical properties.

[0042] Comparison of the tensile strength retention rate and antibacterial rate of the PE pipes of the examples and the comparative examples after aging is as follows in the table: Item Example 1 Example 2 Example 3 Comparative Example Retention rate of tensile strength after aging (%) 85 90 92 60 Antibacterial rate (%) 80 85 90 20 Table 2 Conclusion: This table compares the tensile strength retention rate and antibacterial rate of the PE pipes of the examples and the comparative examples after aging. The tensile strength retention rate of the examples after aging is above 85%, and the antibacterial rate is above 80%, while the tensile strength retention rate of the comparative example after aging is 60%, and the antibacterial rate is only 20%. This fully demonstrates that the polymer blend of the present invention enables the PE pipes to have better anti-aging properties and antibacterial properties.

[0043] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A polymer blend for anti-aging PE pipes used in municipal engineering, characterized in that, It consists of the following components: 40 - 60 parts of linear low density polyethylene (LLDPE); 20 - 30 parts of a novel anti-aging functional polymer, which is copolymerized from vinyltrimethoxysilane and 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, and a disulfide bond with self-healing function is introduced into the molecular main chain, and its chemical structure is: ； The disulfide bond is introduced with dimethyl 3,3'-dithiobispropionate as the raw material; 5 - 10 parts of nano-titanium dioxide / graphene composite filler, where the particle size of nano-titanium dioxide is 20 - 50 nm, the thickness of graphene sheets is 1 - 2 nm, and silver nanoparticles with photocatalytic antibacterial function are further loaded on the surface of nano-titanium dioxide; nano-titanium dioxide and graphene are compounded through the surface-modified silane coupling agent γ-aminopropyltriethoxysilane. One end of the silane coupling agent reacts with the surface hydroxyl groups of nano-titanium dioxide, and the other end of the amino group reacts with the oxygen-containing functional groups on the surface of graphene; 3 - 8 parts of plasticizer, poly(propylene adipate) (PPA) is selected, and a hydroxyl group that can form hydrogen bonds with the polymer matrix is introduced into its molecular structure; 1 - 3 parts of antioxidant, which is composed of the main antioxidant pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] 1010 and the auxiliary antioxidant triphenyl phosphite (TPP) in a mass ratio of 2:1, and 0.1% - 0.3% by mass of the metal ion chelating agent ethylenediaminetetraacetic acid disodium (EDTA-2Na) is added; 1 - 3 parts of light stabilizer, a novel hindered amine light stabilizer bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate is used, and it is microencapsulated. The microcapsule wall material is biodegradable polylactic acid (PLA), and the particle size is 1 - 5 μm.

2. The polymer blend of the anti-aging PE pipe for municipal engineering according to claim 1, characterized in that, It also includes 0.5 - 1 part of an intelligent color-changing indicator; this indicator is an organic compound containing a spiropyran structure. When the PE pipe undergoes severe aging or is damaged, its molecular structure changes, resulting in a color change, which is convenient for timely detection of problems with the PE pipe; through a specific synthesis process, it is evenly dispersed in the blend and has good compatibility with the polymer matrix.

3. The polymer blend of the anti-aging PE pipe for municipal engineering according to claim 1, characterized in that, It also includes adding 0.05% - 0.1% by mass of carbon nanotubes during the preparation of the blend; these carbon nanotubes are surface carboxylated and can form a three-dimensional network structure with the nano-titanium dioxide / graphene composite filler and the polymer matrix, further enhancing the mechanical properties and electrical conductivity of the blend, and can be used to monitor the stress and damage of pipes in municipal engineering.

4. The polymer blend of the anti-aging PE pipe for municipal engineering according to claim 1, characterized in that, In the novel anti-aging functional polymer, the molar ratio of vinyltrimethoxysilane to 4-acryloyloxy-2,2,6,6-tetramethylpiperidine is 3:1 - 5:1; the content of the dynamic covalent bond disulfide bond in the polymer is 0.5% - 1.5%.

5. The polymer blend of the anti-aging PE pipe for municipal engineering according to claim 1, characterized in that In the nano-titanium dioxide / graphene composite filler, the mass ratio of nano-titanium dioxide to graphene is 2:1 - 3:1; the loading amount of silver nanoparticles on the surface of nano-titanium dioxide is 1% - 3%.

6. The polymer blend of the anti-aging PE pipe for municipal engineering according to claim 1, characterized in that The number-average molecular weight of the novel environmentally friendly polyester plasticizer poly(propylene adipate) is 2,000 - 3,000; the hydroxyl content introduced in its molecular structure is 0.5 mmol / g - 1 mmol / g.

7. A method for preparing a polymer blend for the anti-aging PE pipe for municipal engineering according to claim 1, characterized in that, It includes the following steps: S1: Raw material pretreatment: Dry linear low-density polyethylene at 80 - 100 °C for 2 - 3 hours to remove moisture; vacuum dry the nano-titanium dioxide / graphene composite filler at 120 - 150 °C for 3 - 4 hours to improve its dispersibility; perform surface carboxylation treatment on carbon nanotubes, add carbon nanotubes to a mixed acid of concentrated sulfuric acid: concentrated nitric acid = 3:1, stir and react at 50 - 60 °C for 2 - 3 hours, then wash with deionized water until neutral, and dry at 80 - 100 °C for standby; S2: Synthesis of novel anti-aging functional polymer: Add appropriate amounts of vinyltrimethoxysilane, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, initiator, and organic solvent to the reaction kettle. After purging the air with nitrogen, raise the temperature to 70 - 80 °C and react for 4 - 6 hours. Add dimethyl 3,3'-dithiobispropionate containing a disulfide bond for copolymerization in the later stage of the reaction to synthesize a novel anti-aging functional polymer; after the reaction, remove the organic solvent by vacuum distillation to obtain the product; S3: Mixing and stirring: Add the dried linear low-density polyethylene, synthesized novel anti-aging functional polymer, nano-titanium dioxide / graphene composite filler, plasticizer, compound antioxidant, light stabilizer, intelligent color-changing indicator, and carbon nanotubes to a high-speed mixer in proportion, and mix at a rotation speed of 150 - 200 r / min for 10 - 15 minutes to preliminarily mix each component evenly; during the mixing process, control the temperature at 40 - 50 °C to prevent the material from degrading due to frictional heat generation; S4: Melt blending: Transfer the preliminarily mixed material to a twin-screw extruder, set the temperature of each section of the extruder at 160 - 200 °C, and the screw speed at 200 - 300 r / min for melt blending; after the material undergoes sufficient shearing and mixing in the extruder, extrude and pelletize to obtain polymer blend particles for anti-aging PE pipes used in municipal engineering.

8. The method according to claim 7, wherein In step S2, the dosage of the initiator azobisisobutyronitrile is 0.5% - 1% of the total mass of the monomers, the dosage of the organic solvent toluene is 1 - 2 times the total volume of the monomers; the dosage of the crosslinking agent containing a disulfide bond is 0.5% - 1% of the total mass of the monomers.

9. The method according to claim 7, wherein In step S3, the mixing chamber of the high-speed mixer adopts a jacket structure, and the mixing temperature is controlled by circulating water; during the mixing process, an ultrasonic-assisted dispersion technology is adopted, with an ultrasonic frequency of 20 - 30 kHz and a power of 100 - 200 W to promote the uniform dispersion of each component.

10. The method according to claim 7, characterized in that In step S4, the length-diameter ratio of the twin-screw extruder is 30:1 - 40:1, which has a good mixing effect and ensures that each component is evenly dispersed in the blend; during the extrusion process, an on-line quality monitoring system is adopted to monitor the melt flow rate and density of the blend in real time to ensure the stable quality of the product.

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