A polyolefin tube with copper ion resistance and preparation method thereof

Abstract

The present invention discloses a polyolefin pipe with copper ion resistance and a preparation method thereof, and relates to the technical field of pipes. A copper-resistant polyolefin material comprises the following components in mass percentage: PPRCT 95-98%; modified wollastonite composite material 2-5%; the modified wollastonite composite material comprises wollastonite, an antioxidant and a surfactant sequentially grafted on the surface of wollastonite, the mass ratio of wollastonite, surfactant and antioxidant is (2-2.5): (0.3-0.6): 1.5, and the crystallinity of β crystals in PPRCT is 60-80%. The polyolefin pipe of the present invention has excellent pressure resistance, low thermal conductivity and good heat resistance. In the long-term use of a hot water pipe system containing copper, the pipe can be free from the catalytic influence of metallic copper or free copper.

Description

Technical Field

[0001] The invention relates to the technical field of pipes, and in particular to a polyolefin pipe resistant to copper ions and a preparation method thereof. Background Art

[0002] PPRCT pipe is the abbreviation of random copolymer polypropylene pipe (also known as type 4 polypropylene pipe), which is a random copolymer formed by copolymerization of propylene and another olefin monomer; the molecular structure of polypropylene is changed due to the irregular distribution of the copolymer monomer and the polypropylene chain, thus forming the excellent physical and chemical properties of this pipe. Due to its light weight, corrosion resistance, smooth inner wall without scaling, simple construction and maintenance, and long service life, it is widely used in building water supply and drainage, urban and rural drainage, municipal administration and other fields.

[0003] In actual situations, copper-embedded pipe fittings are used to connect equipment or bathroom products in the PPRCT hot and cold water piping system; in the equipment room, copper components are used in the pipes of the equipment and hot water circulation system, and PPRCT pipes play the role of distribution pipes in the above two situations. In these usage scenarios, when PPRCT materials come into contact with metallic copper or free copper, they will catalyze chemical oxidation corrosion of random copolymer polypropylene, causing premature degradation of PPRCT materials, and then causing the pipes to fail before reaching the expected design life.

[0004] In the existing hot water circulation system pipelines, polyolefin pipes are mainly used to maintain the operation of the pipeline system. During the operation, metallic copper and free copper appear and catalyze the aging of the polyolefin pipes, making the actual service life of the polyolefin pipes shorter than the designed service life, resulting in an increase in the maintenance cost of the polyolefin pipes under this working condition. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a polyolefin pipe with copper ion resistance and a preparation method thereof. The polyolefin pipe of the present invention has excellent pressure resistance, low thermal conductivity, and good heat resistance. In the long-term use of a hot water pipe system containing copper, the pipe can be free from the catalytic influence of metallic copper or free copper.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present invention provides a copper-resistant polyolefin material, wherein the copper-resistant polyolefin material comprises the following components in percentage by mass: 95-98% PPRCT; 2-5% modified wollastonite composite material;

[0008] The modified wollastonite composite material comprises wollastonite, an antioxidant and a surfactant sequentially grafted on the surface of the wollastonite, the mass ratio of the wollastonite, the surfactant and the antioxidant is (2-2.5): (0.3-0.6): 1.5, and the crystallinity of the β crystal in the PPRCT is 60-80%.

[0009] The PPRCT described in the present invention can be purchased from Borealis 7050 or Yanshan Petrochemical 3120.

[0010] Preferably, the mass ratio of wollastonite, surfactant and antioxidant is 2.3:(0.3-0.6):1.5.

[0011] Preferably, the crystallinity of the β extraction (β crystal form) is controlled at 70-80%.

[0012] Preferably, the antioxidant includes at least one of antioxidant 1024 and antioxidant 369.

[0013] Preferably, the surfactant includes at least one of sodium dodecyl sulfate, sodium N,N-oleoylmethyl taurate, sodium fatty alcohol sulfate, and sodium dodecylbenzene sulfonate.

[0014] Preferably, the wollastonite is calcined at a temperature of 800-900°C in advance.

[0015] Preferably, the method for preparing the modified wollastonite composite material comprises the following steps:

[0016] (1) Mixing an antioxidant and a surfactant in an alkaline aqueous solution and controlling the pH value of the system to be 9-11 to form a surfactant solution;

[0017] (2) Adding the surfactant solution into the calcined wollastonite and mixing them evenly, a modified wollastonite composite material is obtained after the surfactant and the antioxidant are grafted.

[0018] Preferably, the preparation method of the calcined wollastonite comprises the following steps:

[0019] Add desiliconization alkali solution and calcium hydroxide to ultrapure water in a reactor and react at a constant temperature of 200-300°C for 2-3 hours. After the reaction is completed, filter and wash to obtain a filter cake, and then dry the obtained filter cake at 150-200°C to obtain calcined wollastonite.

[0020] Preferably, the desiliconization alkali solution and calcium hydroxide are mixed at a molar ratio of silicon oxide to calcium hydroxide in the desiliconization alkali solution of 1:(1-2), the desiliconization alkali solution and water are used as liquids, and calcium hydroxide is used as a solid, and the liquid-to-solid mass ratio is (4-7):1.

[0021] Preferably, the wollastonite is flaky and nano-sized, with a particle size of 15-30 nm.

[0022] In a second aspect, the present invention further provides a method for preparing a copper-resistant polyolefin material, comprising the following steps:

[0023] The modified wollastonite composite material and PPRCT are uniformly mixed, the temperature is controlled to be 190° C.-220° C., and extrusion granulation is performed to obtain the copper-resistant polyolefin material.

[0024] In a third aspect, the present invention further provides a polyolefin tube resistant to copper ions, the polyolefin tube comprising an outer layer and an inner layer, the inner layer comprising the above-mentioned copper-resistant polyolefin material, and the outer layer comprising a PPRCT material.

[0025] In a fourth aspect, the present invention further provides a method for preparing a polyolefin tube having copper ion resistance, comprising the following steps:

[0026] (1) Adding the inner layer material and the outer layer material to a single-screw double-layer pipe forming machine for co-extrusion, vacuuming, sizing, and cooling to obtain a composite pipe semi-finished product;

[0027] (2) The semi-finished composite pipe is placed in a temperature range of 100-120° C. for annealing, and then cooled to obtain the polyolefin pipe having copper ion resistance.

[0028] Preferably, the specific steps of the annealing treatment in step (2) are:

[0029] The composite pipe semi-finished product is placed in a temperature of 100-105°C for preheating treatment for 30-50 minutes, and then heated to 110-120°C for insulation treatment for 60-80 minutes. After the end, it is naturally cooled to room temperature to complete the annealing treatment.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) In the study of the copper resistance of pipelines, the present invention found that by controlling the crystallinity of β crystals (β crystal form) in the PPRCT matrix material to 60-80%, the probability of the material itself being attacked by copper ions and accelerated aging can be reduced, the breakage rate of the molecular chain structure of the material itself can be slowed down, and the material itself can be effectively protected from attack by copper ions and other copper-containing element solutions, thereby increasing the overall service life of the pipeline.

[0032] (2) The present invention modifies wollastonite by using an antioxidant and a surfactant so that the antioxidant is grafted onto the surface of wollastonite particles, thereby forming a chemical bond between the antioxidant and wollastonite, which is more stable and long-lasting on the surface of wollastonite. The effectively grafted antioxidant migrates into the solution during solution flushing, thereby maximizing its effect. In addition, the modified wollastonite can better adsorb the copper element components on the surface of the pipe material or inside the pipe material, and then the adsorbed copper element components are eliminated by the antioxidant inside the pipe material, effectively avoiding the problem of copper elements accelerating pipeline aging, thereby improving the copper resistance of the inner layer of the pipeline. At the same time, the surface coating of the surfactant can effectively reduce the surface energy of the wollastonite, which is beneficial to the uniform dispersion of the wollastonite in the polyolefin matrix material, and more effectively assists in improving the resistance of the polyolefin material to copper ion catalytic aging, thereby improving the overall copper resistance. DETAILED DESCRIPTION

[0033] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the protection scope and implementation methods of the present invention are not limited thereto.

[0034] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0035] Example 1

[0036] The present embodiment discloses a copper-resistant polyolefin material, which includes the following components in percentage by mass: 98% PPRCT (Borealis 7050); and 2% modified wollastonite composite material.

[0037] The preparation method of the modified wollastonite composite material comprises the following steps:

[0038] (1) adding desiliconization alkali solution and calcium hydroxide to ultrapure water in a reactor to react at a constant temperature of 200° C. for 2 hours. After the reaction is completed, filtering and washing to obtain a filter cake, and then drying the obtained filter cake at 150° C. to obtain flaky nano-scale wollastonite, wherein the molar ratio of silicon oxide to calcium hydroxide in the desiliconization alkali solution is 1:1;

[0039] (2) calcining the flaky nano-scale wollastonite at 800°C for 3 hours;

[0040] (3) Dissolve the antioxidant (antioxidant 369) in a 0.1 mol / L sodium hydroxide aqueous solution, add the long-chain surfactant fatty alcohol sodium sulfate, mix well, and control the pH value of the system to 10 to form an alkaline surfactant aqueous solution;

[0041] (4) Adding an alkaline surfactant aqueous solution to the calcined wollastonite, stirring at room temperature for 24 hours, filtering, washing with ultrapure water, and drying the obtained solid at 70°C to constant weight to obtain a modified wollastonite composite material after the surfactant and antioxidant are grafted.

[0042] The mass ratio of wollastonite, surfactant and antioxidant in the modified wollastonite composite material is 2:0.3:1.5, and the crystallinity of β crystals in PPRCT is 70%.

[0043] This embodiment also discloses a method for preparing a copper-resistant polyolefin material, comprising the following steps:

[0044] The modified wollastonite composite material and PPRCT are mixed evenly, added into a granulator and stirred at a speed of 1800 r / min for thorough mixing, and the temperature is controlled at 190° C. for extrusion granulation, and the copper-resistant polyolefin material is obtained after drying.

[0045] This embodiment also discloses a copper ion resistant polyolefin tube, comprising an outer layer and an inner layer, wherein the inner layer comprises a copper resistant polyolefin material, and the outer layer comprises a PPRCT material.

[0046] This embodiment also discloses a method for preparing a copper ion-resistant polyolefin tube, comprising the following steps:

[0047] (1) Adding the inner layer material and the outer layer material into a single-screw double-layer pipe forming machine for co-extrusion at a temperature of 190° C., vacuuming and sizing, and cooling to obtain a composite pipe semi-finished product with an inner layer thickness of 1 mm;

[0048] (2) The composite pipe semi-finished product is placed in an oven with uniform temperature and controllable lifting and lowering. The temperature is uniformly raised to 100°C within 40 minutes, and the temperature is controlled to be constant for preheating for 30 minutes. Then the temperature is uniformly raised to 110°C within 10 minutes, and the temperature is controlled to be constant for 65 minutes. After the temperature is removed from the oven, it is naturally cooled to room temperature to obtain a polyolefin pipe with copper ion resistance after annealing treatment. The crystallinity of the β crystal of the inner layer PPRCT is 70%.

[0049] Example 2

[0050] The present embodiment discloses a copper-resistant polyolefin material, which includes the following components in percentage by mass: 96% of PPRCT (Borealis 7050) and 4% of modified wollastonite composite material.

[0051] The preparation method of the modified wollastonite composite material comprises the following steps:

[0052] (1) adding desiliconization alkali solution and calcium hydroxide to ultrapure water in a reactor to react at a constant temperature of 300° C. for 3 hours. After the reaction is completed, filtering and washing to obtain a filter cake, and then drying the obtained filter cake at 200° C. to obtain flaky nano-scale wollastonite, wherein the molar ratio of silicon oxide to calcium hydroxide in the desiliconization alkali solution is 1:2;

[0053] (2) calcining the flaky nano-scale wollastonite at 900°C for 3 hours;

[0054] (3) Dissolve the antioxidant (antioxidant 1024) in a 0.1 mol / L sodium hydroxide aqueous solution, add the long carbon chain surfactant sodium N-oleoyl-N-methyl taurate, mix well, and control the pH value of the system to 9 to form an alkaline surfactant aqueous solution;

[0055] (4) Adding an alkaline surfactant aqueous solution to the calcined wollastonite, stirring at room temperature for 24 hours, filtering, washing with ultrapure water, and drying the obtained solid at 70°C to constant weight to obtain a modified wollastonite composite material after the surfactant and antioxidant are grafted.

[0056] The mass ratio of wollastonite, surfactant and antioxidant in the modified wollastonite composite material is 2.5:0.6:1.5, so that the crystallinity of β crystals in PPRCT is 75%.

[0057] This embodiment also discloses a method for preparing a copper-resistant polyolefin material, comprising the following steps:

[0058] The modified wollastonite composite material and PPRCT are mixed evenly, added into a granulator and stirred at a speed of 1500 r / min for thorough mixing, and the temperature is controlled at 220° C. for extrusion granulation, and the copper-resistant polyolefin material is obtained after drying.

[0059] This embodiment also discloses a copper ion resistant polyolefin tube, comprising an outer layer and an inner layer, wherein the inner layer comprises a copper resistant polyolefin material, and the outer layer comprises a PPRCT material.

[0060] This embodiment also discloses a method for preparing a copper ion-resistant polyolefin tube, comprising the following steps:

[0061] (1) Add the inner layer material and the outer layer material into a single-screw double-layer pipe forming machine for co-extrusion, control the temperature to 220° C., evacuate and sizing, cool, and obtain a composite pipe semi-finished product with an inner layer thickness of 1 mm;

[0062] (2) The composite pipe semi-finished product is placed in an oven with uniform temperature and controllable lifting and lowering. The temperature is uniformly raised to 100°C within 40 minutes, and the temperature is controlled to be constant for preheating for 50 minutes. Then the temperature is uniformly raised to 120°C within 10 minutes, and the temperature is controlled to be constant for 80 minutes. After the temperature is removed from the oven, it is naturally cooled to room temperature to obtain a polyolefin pipe with copper ion resistance after annealing treatment. The crystallinity of the β crystal of the inner layer PPRCT is 75%.

[0063] Example 3

[0064] The present embodiment discloses a copper-resistant polyolefin material, which includes the following components in percentage by mass: 97% PPRCT (Borealis 7050); and 3% modified wollastonite composite material.

[0065] The preparation method of the modified wollastonite composite material comprises the following steps:

[0066] (1) adding desiliconization alkali solution and calcium hydroxide to ultrapure water in a reactor to react at a constant temperature of 200° C. for 2 hours. After the reaction is completed, filtering and washing to obtain a filter cake, and then drying the obtained filter cake at 150° C. to obtain flaky nano-scale wollastonite, wherein the molar ratio of silicon oxide to calcium hydroxide in the desiliconization alkali solution is 1:1;

[0067] (2) calcining the flaky nano-scale wollastonite at 800°C for 3 hours;

[0068] (3) Dissolve the antioxidant (antioxidant 1024) in a 0.1 mol / L sodium hydroxide aqueous solution, add the long carbon chain surfactant sodium dodecyl sulfate, mix well, and control the pH value of the system to 10 to form an alkaline surfactant aqueous solution;

[0069] (4) Adding an alkaline surfactant aqueous solution to the calcined wollastonite, stirring at room temperature for 28 hours, filtering, washing with ultrapure water, and drying the obtained solid at 70°C to constant weight to obtain a modified wollastonite composite material after the surfactant and antioxidant are grafted.

[0070] The mass ratio of wollastonite, surfactant and antioxidant in the modified wollastonite composite material is 2.3:0.5:1.5, so that the crystallinity of β crystals in PPRCT is 80%.

[0071] This embodiment also discloses a method for preparing a copper-resistant polyolefin material, comprising the following steps:

[0072] The modified wollastonite composite material and PPRCT are mixed evenly, added into a granulator and stirred at a speed of 1100 r / min for thorough mixing, and the temperature is controlled at 200° C. for extrusion granulation, and the copper-resistant polyolefin material is obtained after drying.

[0073] This embodiment also discloses a copper ion resistant polyolefin tube, comprising an outer layer and an inner layer, wherein the inner layer comprises a copper resistant polyolefin material, and the outer layer comprises a PPRCT material.

[0074] This embodiment also discloses a method for preparing a copper ion-resistant polyolefin tube, comprising the following steps:

[0075] (1) Add the inner layer material and the outer layer material into a single-screw double-layer pipe forming machine for co-extrusion, control the temperature to 220° C., evacuate and sizing, cool, and obtain a composite pipe semi-finished product with an inner layer thickness of 1 mm;

[0076] (2) The composite pipe semi-finished product is placed in an oven with uniform temperature and controllable lifting and lowering. The temperature is uniformly raised to 100°C within 40 minutes, and the temperature is controlled to be constant for preheating for 40 minutes. Then the temperature is uniformly raised to 115°C within 10 minutes, and the temperature is controlled to be constant for 70 minutes. After the temperature is removed from the oven, it is naturally cooled to room temperature to obtain a polyolefin pipe with copper ion resistance after annealing treatment. The crystallinity of the β crystal of the inner layer PPRCT is 80%.

[0077] Comparative Example 1

[0078] A copper-resistant polyolefin material, which is different from Example 1 in that no modified wollastonite composite material is added.

[0079] Comparative Example 2

[0080] A method for preparing a polyolefin pipe resistant to copper ions, which is different from Example 1 in that the semi-finished composite pipe in step (2) is not annealed.

[0081] Comparative Example 3

[0082] A copper-resistant polyolefin material is different from Example 1 in that the mass ratio of wollastonite, surfactant and antioxidant in the modified wollastonite composite material is 1:0.3:1.5.

[0083] Comparative Example 4

[0084] A copper-resistant polyolefin material is different from Example 1 in that the mass ratio of wollastonite, surfactant and antioxidant in the modified wollastonite composite material is 2:0.8:1.5.

[0085] Comparative Example 5

[0086] A copper-resistant polyolefin material, which is different from Example 1 in that the copper-resistant polyolefin material comprises the following components in percentage by mass: 93% PPRCT; 7% modified wollastonite composite material.

[0087] Comparative Example 6

[0088] A copper-resistant polyolefin material, which is different from Example 1 in that the copper-resistant polyolefin material comprises the following components in percentage by mass: 99% of PPRCT and 1% of modified wollastonite composite material.

[0089] Comparative Example 7

[0090] A method for preparing a copper ion-resistant polyolefin pipe, which is different from Example 1 in that, in step (2): the composite pipe semi-finished product is placed in an oven with uniform temperature and controllable lifting and lowering, the temperature is uniformly raised to 100° C. within 40 minutes, and the temperature is controlled to be kept constant for preheating for 10 minutes, and then the temperature is uniformly raised to 110° C. within 10 minutes, and the temperature is controlled to be kept constant for 30 minutes, and then the semi-finished product is removed from the oven and naturally cooled to room temperature.

[0091] Comparative Example 8

[0092] A method for preparing a copper ion-resistant polyolefin pipe, which is different from Example 1 in that, in step (2): the composite pipe semi-finished product is placed in an oven with uniform temperature and controllable lifting and lowering, the temperature is uniformly raised to 100° C. within 40 minutes, and the temperature is controlled to be kept constant for preheating for 50 minutes, and then the temperature is uniformly raised to 130° C. within 10 minutes, and the temperature is controlled to be kept constant for 90 minutes, and then the semi-finished product is removed from the oven and naturally cooled to room temperature.

[0093] Performance Testing

[0094] Copper ion solution immersion experiment: Prepare 3.0 mg / L copper ion solution, and inject the copper ion solution into multiple sections of 30 cm ± 0.5 cm pipe at a constant temperature of 65 ° C and a pH value of 7 ± 0.5.

[0095] Oxidation induction time (OIT) test: Before immersion and after immersion for 3000h, take the inner layer of copper-resistant polyolefin pipe and test it according to standard GB / T 19466.6-2009.

[0096] The hydrostatic test is carried out in accordance with GB / T 6111-2003 standard.

[0097] The above experimental results are shown in Table 1 and Table 2.

[0098] Table 1 Oxidation Induction Time (OIT) Test

[0099]

[0100] Table 2 Hydrostatic performance test

[0101]

[0102]

[0103] According to Table 1, the present invention can effectively improve the copper resistance of the material as a whole by adding modified wollastonite composite material and performing annealing treatment. In addition, the present invention can reduce the probability of accelerated aging of the material itself by copper ion attack by controlling the crystallinity of β crystal (β crystal form) in the PPRCT matrix material to 60-80%, slow down the breakage rate of the molecular chain structure of the material itself, effectively improve the material itself from being attacked by copper ions and other copper-containing element solutions, and improve the overall service life of the pipeline.

[0104] The present invention modifies wollastonite by using an antioxidant and a surfactant, so that the antioxidant is grafted on the surface of wollastonite particles, thereby enabling the antioxidant to form a chemical bond with the wollastonite, which is more stable and long-lasting on the surface of the wollastonite, is conducive to the uniform dispersion of wollastonite in a polyolefin matrix material, and more effectively assists in improving the performance of the polyolefin material in resisting copper ion catalytic aging, thereby improving the overall copper resistance.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A copper-resistant polyolefin material, characterized in that: The copper-resistant polyolefin material includes the following components in percentage by mass: PPRCT 95-97%; Modified wollastonite composite material 3-5%; The modified wollastonite composite material comprises wollastonite, an antioxidant and a surfactant sequentially grafted on the surface of wollastonite, wherein the mass ratio of the wollastonite, the surfactant and the antioxidant is (2-2.5): (0.3-0.6): 1.5, and the crystallinity of the β crystal in the PPRCT is 60-80%; The antioxidant includes at least one of antioxidant 1024 and antioxidant 369.

2. The copper-resistant polyolefin material according to claim 1, characterized in that: The mass ratio of the wollastonite, surfactant and antioxidant is 2.3:(0.3-0.6):1.5, and the crystallinity of the β crystal in the PPRCT is 70-80%.

3. The copper-resistant polyolefin material according to claim 1, characterized in that: The wollastonite is calcined at a temperature of 800-900°C in advance.

4. The copper-resistant polyolefin material according to claim 3, characterized in that: The preparation method of the modified wollastonite composite material comprises the following steps: (1) Mixing an antioxidant and a surfactant in an alkaline aqueous solution and controlling the pH value of the system to be 9-11 to form a surfactant solution; (2) Adding the surfactant solution into the calcined wollastonite and mixing them evenly, a modified wollastonite composite material is obtained after the surfactant and the antioxidant are grafted.

5. The copper-resistant polyolefin material according to claim 4, characterized in that: The steps of preparing the calcined wollastonite are as follows: Add desiliconization alkali solution and calcium hydroxide to ultrapure water in a reactor and react at a constant temperature of 200-300°C for 2-3 hours. After the reaction is completed, filter and wash to obtain a filter cake, and then dry the obtained filter cake at 150-200°C to obtain calcined wollastonite.

6. The copper-resistant polyolefin material according to claim 5, characterized in that: The molar ratio of silicon oxide to calcium hydroxide in the desiliconization alkali solution is 1:(1-2).

7. The copper-resistant polyolefin material according to claim 1, characterized in that: The surfactant includes at least one of sodium dodecyl sulfate, sodium N,N-oleoylmethyl taurate, sodium fatty alcohol sulfate, and sodium dodecylbenzene sulfonate.

8. The method for preparing the copper-resistant polyolefin material according to any one of claims 1 to 7, characterized in that: The following steps are involved: The modified wollastonite composite material and PPRCT are uniformly mixed, the temperature is controlled to be 190° C.-220° C., and extrusion granulation is performed to obtain the copper-resistant polyolefin material.

9. A polyolefin tube having copper ion resistance, characterized in that: The polyolefin tube comprises an outer layer and an inner layer, the inner layer comprises the copper-resistant polyolefin material according to any one of claims 1 to 7, and the outer layer comprises a PPRCT material.

10. The method for preparing a polyolefin tube having copper ion resistance according to claim 9, characterized in that: The following steps are involved: (1) Adding the inner layer material and the outer layer material to a single-screw double-layer pipe forming machine for co-extrusion, vacuuming, sizing, and cooling to obtain a composite pipe semi-finished product; (2) placing the semi-finished composite pipe at a temperature of 100-120° C. for annealing, and cooling the semi-finished composite pipe to obtain the polyolefin pipe having copper ion resistance; The specific steps of the annealing treatment in step (2) are: The composite pipe semi-finished product is placed in a temperature of 100-105°C for preheating treatment for 30-50 minutes, and then heated to 110-120°C for insulation treatment for 60-80 minutes. After the end, it is naturally cooled to room temperature to complete the annealing treatment.

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