PE-Xa pipe with chlorine resistance as well as preparation method and application of PE-Xa pipe

Abstract

The invention discloses a PE-Xa pipe with chlorine resistance as well as a preparation method and application of the PE-Xa pipe, and relates to the technical field of high polymer materials. The PE-Xa pipe comprises the following raw material components in parts by weight: 100 parts of high density polyethylene; 0.2 to 1 part of a cross-linking agent; 0.5 to 1.5 parts of modified hydrotalcite; 0.3 to 0.8 part of sulfonated ion exchange resin microspheres; 0.3 to 1 part of an antioxidant; 0.1 to 0.3 part of zinc oxide whisker; the modified hydrotalcite comprises magnesium aluminum hydrotalcite and nano zero-valent iron loaded on the magnesium aluminum hydrotalcite; the sulfonated ion exchange resin microspheres are formed by sulfonating ion exchange resin microspheres, and the ion exchange resin microspheres comprise at least one of styrene anion resin microspheres, polyacrylic acid anion resin microspheres, epoxy anion resin microspheres and quaternized styrene resin microspheres. The PE-Xa pipe disclosed by the invention has excellent chlorine resistance and cracking resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a PE-Xa pipe with chlorine resistance, a preparation method thereof, and an application thereof. Background Art

[0002] The anti-chlorine technology of traditional peroxide-crosslinked polyethylene (PE-Xa) pipes mainly neutralizes chloride ions by adding acid scavengers (such as calcium stearate and hydrotalcite), but there are the following bottlenecks: (1) Limited adsorption capacity: The chloride ion adsorption capacity of conventional hydrotalcite is only 2-3 mmol / g, which is difficult to cope with high-chlorine environments (greater than 10 mg / L); (2) Dynamic failure: During long-term use, the acid scavenger is prone to saturation or precipitation, resulting in the attenuation of chlorine resistance performance; (3) Insufficient synergy: The interaction between the anti-chlorine agent and the crosslinking agent and antioxidant has not been fully explored.

[0003] Therefore, it is an urgent problem to be solved at present that PE-Xa pipes need to have excellent chlorine resistance performance. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a PE-Xa pipe with chlorine resistance, a preparation method thereof, and an application thereof. The PE-Xa pipe of the present invention has excellent chlorine resistance and crack resistance performance.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: In the first aspect, the present invention provides a PE-Xa pipe with chlorine resistance, comprising the following raw material components in parts by weight: 100 parts of high-density polyethylene (HDPE); 0.2-1 part of crosslinking agent; 0.5-1.5 parts of modified hydrotalcite; 0.3-0.8 part of ion exchange resin microspheres; 0.3-1 part of antioxidant; 0.1-0.3 part of zinc oxide whiskers; The modified hydrotalcite includes magnesium-aluminum hydrotalcite (Mg-Al-LDH) and nano-zero-valent iron (nZVI) loaded on the magnesium-aluminum hydrotalcite, and the mass ratio of nano-zero-valent iron to magnesium-aluminum hydrotalcite in the modified hydrotalcite is (5-15):(85-95); The sulfonated ion exchange resin microspheres are obtained by sulfonating ion exchange resin microspheres, and the ion exchange resin microspheres include at least one of styrene anion resin microspheres, polyacrylic acid anion resin microspheres, epoxy group anion resin microspheres, and quaternized styrene resin microspheres.

[0006] In the present invention, the modified hydrotalcite loads nano-zero-valent iron on magnesium-aluminum hydrotalcite to form an "adsorption-reduction" dual-mechanism composite anti-chlorine system. Magnesium-aluminum hydrotalcite adsorbs chloride ions through interlayer anion exchange, and nano-zero-valent iron reduces HClO to Cl through redox reaction.- and H2O, and the reaction formula is: Fe + HClO + H + → Fe 2+ + Cl - + H2O; Therefore, when the modified hydrotalcite adsorbs Cl - , it also reduces hypochlorous acid (HClO → Cl - + H2O), which improves the adsorption amount of chloride ions. The ion exchange resin microspheres can provide long-term chloride ion capture. Zinc oxide whiskers can inhibit the chain-breaking catalysis of chloride ions on the polyethylene molecular chain and improve the stress cracking resistance of PE-Xa pipes. Therefore, through the synergistic effect of the modified hydrotalcite, sulfonated ion exchange resin microspheres, and zinc oxide whiskers, the present invention not only helps to improve the ability to adsorb chloride ions, thereby improving the anti-chlorine performance of PE-Xa pipes, but also helps to improve the crack resistance of PE-Xa pipes.

[0007] If the mass ratio of nano-zero-valent iron to magnesium-aluminum hydrotalcite is too small and the content of nano-zero-valent iron is too low, the ability to reduce hypochlorous acid (HClO) is limited, resulting in a decrease in the anti-chlorine performance of PE-Xa pipes; if the mass ratio of nano-zero-valent iron to magnesium-aluminum hydrotalcite is too large and the content of nano-zero-valent iron is too high, nano-zero-valent iron is prone to agglomeration, reducing its specific surface area. At the same time, it will also damage the structure of magnesium-aluminum hydrotalcite, leading to a decrease in the adsorption capacity of the modified hydrotalcite. Therefore, by controlling the mass ratio of nano-zero-valent iron to magnesium-aluminum hydrotalcite within the above range, the present invention is beneficial to improving the ability of the modified hydrotalcite to adsorb chloride ions, thereby improving the anti-chlorine performance of PE-Xa pipes. At the same time, by subjecting the ion exchange resin microspheres to surface sulfonation treatment to introduce sulfonic acid groups (-SO3H), the present invention is beneficial to improving the chloride ion exchange efficiency, thereby further improving the anti-chlorine performance of PE-Xa pipes.

[0008] Preferably, the mass ratio of nano-zero-valent iron to magnesium-aluminum hydrotalcite in the modified hydrotalcite is any one or the range value of both of 5:95, 6:94, 7:93, 8:92, 9:91, 10:90, 11:89, 12:88, 13:87, 14:86, 15:85.

[0009] Preferably, the PE-Xa pipe comprises the following raw material components in parts by weight: 100 parts of high-density polyethylene; 0.5 - 1 part of cross-linking agent; 0.8 - 1.5 parts of modified hydrotalcite; 0.5 - 0.8 part of sulfonated ion exchange resin microspheres; 0.6 - 0.8 part of antioxidant; 0.2 - 0.3 part of zinc oxide whiskers.

[0010] Preferably, the high-density polyethylene includes high-density polyethylene with a high molecular weight distribution and high-density polyethylene with a low molecular weight distribution. The molecular weight distribution of the high-density polyethylene with a high molecular weight distribution is A, and the molecular weight distribution of the high-density polyethylene with a low molecular weight distribution is B. A and B satisfy the following relationship: 100%×(A - B) / B = 30% - 50%; and the mass ratio of the high-density polyethylene with a high molecular weight distribution to the high-density polyethylene with a low molecular weight distribution is (5 - 6):(4 - 5).

[0011] The present invention uses a blend of two high-density polyethylenes with different molecular weight distributions, which is beneficial to improving the strength and processing fluidity of the melt material, inhibiting local degradation caused by uneven shear stress during the cross-linking process, and thus improving the mechanical properties of PE-Xa pipes.

[0012] It should be noted that the molecular weight distribution (MWD) described in the present invention is the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn), and is represented by Mw / Mn.

[0013] Preferably, the preparation method of the magnesium-aluminum hydrotalcite includes the following steps: (1) Dissolve magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) and aluminum nitrate nonahydrate (Al(NO3)3·9H2O) in water to obtain a mixed solution. The molar ratio of Mg 2+ to Al 3+ is (4 - 5):1; (2) Dropwise add an alkaline solution to the mixed solution until the pH of the solution is 9 - 11, and carry out a hydrothermal reaction at 70 - 80 °C for 20 - 24 h to obtain a product; (3) Centrifuge and wash the product until it is neutral, dry, grind and pass through a sieve to obtain magnesium-aluminum hydrotalcite.

[0014] The present invention controls the molar ratio of Mg 2+ to Al 3+ as well as the temperature and time of the hydrothermal reaction to obtain high-crystallinity Mg-Al-LDH, which improves the adsorption performance of the magnesium-aluminum hydrotalcite.

[0015] Preferably, the alkaline solution in step (2) includes one of sodium hydroxide solution, potassium hydroxide solution, and ammonia water solution.

[0016] Preferably, the particle size of the magnesium-aluminum hydrotalcite is 0.1 - 5 μm, and the specific surface area is 180 - 250 m 2 / g.

[0017] Preferably, the preparation method of the modified hydrotalcite includes the following steps: Disperse magnesium aluminum hydrotalcite in an organic solvent to obtain a dispersion; then add an iron ion solution to the dispersion, mix evenly, and dropwise add a sodium borohydride (NaBH4) solution to obtain a modified hydrotalcite.

[0018] Preferably, the organic solvent includes one of ethanol, isopropanol, and acetone. Ethanol is preferred.

[0019] Preferably, the iron ion solution includes one of ferric chloride solution, ferric sulfate solution, and ferric nitrate solution. Ferric chloride solution is preferred, and the reduction efficiency is higher.

[0020] Preferably, the rate of dropping the NaBH4 solution is 0.3 - 0.5 mL / min.

[0021] Preferably, the 3+ molar ratio of Fe

[0022] :NaBH4 is 1:(2 - 3), preferably 1:3. 3+ In the preparation of the modified hydrotalcite, by adjusting the reduction rate of NaBH4 and the concentration of Fe

[0023] Preferably, the particle size of the nano zero-valent iron is 15 - 30 nm, the average particle size is 22 nm, and the specific surface area is 30 - 50 m 2 / g.

[0024] The present invention uses nano zero-valent iron with a small particle size, which has a higher specific surface area and is beneficial to improving the reduction efficiency of hypochlorous acid.

[0025] Preferably, the particle size of the sulfonated ion exchange resin microspheres is 1 - 5 μm.

[0026] Preferably, the preparation method of the styrene anion resin microspheres includes the following steps: Disperse styrene and divinylbenzene evenly in a sorbitan monooleate (Span-80) solution, and polymerize at 50 - 60 °C for 22 - 24 h to obtain styrene anion resin microspheres.

[0027] Preferably, the preparation method of the sulfonated ion exchange resin microspheres includes the following steps: Swell the ion exchange resin microspheres in dichloromethane; then add chlorosulfonic acid, sulfonate at 0 - 5 °C for 1 - 2 h, wash with water until neutral, and finally obtain sulfonated ion exchange resin microspheres after washing and drying.

[0028] Preferably, the zinc oxide whiskers are four-needle-shaped structures, with a single-needle length of 10-20 μm, a single-needle diameter of 0.5-1 μm, and a length-to-diameter ratio of the single needle of (20-50):1.

[0029] In the present invention, by using zinc oxide whiskers with a high length-to-diameter ratio, a three-dimensional network is formed during the cross-linking process to inhibit the Cl - penetration path, so that the hydrostatic strength of the pipe is improved.

[0030] Preferably, the cross-linking agent includes at least one of dicumyl peroxide (DTBP), di-tert-butyl peroxide (DTBP), and benzoyl peroxide (BPO).

[0031] Preferably, the antioxidant includes a hindered phenol antioxidant and a thioester antioxidant.

[0032] Preferably, the hindered phenol antioxidant includes at least one of antioxidant 1010 and antioxidant 1076.

[0033] Preferably, the thioester antioxidant includes at least one of antioxidant DSTDP (dilauryl thiodipropionate) and antioxidant DLTDP (distearyl thiodipropionate).

[0034] In a second aspect, the present invention also provides a method for preparing a PE-Xa pipe with chlorine resistance, including the following steps: Adding high-density polyethylene, a cross-linking agent, an antioxidant, modified hydrotalcite, sulfonated ion exchange resin microspheres, and zinc oxide whiskers into a mixer, and obtaining a mixture after mixing evenly; then melting and extruding the mixture by an extruder, and cooling to obtain the PE-Xa pipe with chlorine resistance.

[0035] Preferably, the extruder is a three-stage extruder: the temperature range of the first stage is 140-160 °C, the temperature range of the second stage is 200-230 °C, the temperature range of the third stage is 180-200 °C, the die head pressure of the extruder is 15-20 MPa, and the extrusion speed is 1.5-2.5 m / min.

[0036] In the present invention, by using a three-stage extruder, the mixture is plasticized in the first-stage temperature range, dynamically cross-linked in the second-stage temperature range, and shaped in the third-stage temperature range. By controlling the cross-linking degree and dispersibility in sections, it is beneficial to improve the ability of the pipe to adsorb chloride ions.

[0037] Preferably, a three-stage cooling water tank is used for cooling, and the temperature gradient is set as follows: the first stage: 80-90 °C, the second stage: 50-60 °C, the third stage: 20-30 °C.

[0038] The pipe material is slowly cooled at a high temperature in the first stage to promote cross-linking of the inner layer, then is shaped at a medium temperature in the second stage to balance the stresses between the inner and outer layers, and finally is rapidly cooled at a low temperature in the third stage to lock the cross-linked structure. Through gradient cooling, it is ensured that the inner and outer layers of the pipe cool down synchronously, reducing the difference in thermal stress, which is beneficial to improving the crack resistance of the pipe material.

[0039] Preferably, the temperature during mixing is 120 - 140 °C, the shear rate is 200 - 400 rpm, and the mixing time is 10 - 15 min.

[0040] Thirdly, the present invention also provides an application of a PE-Xa pipe material with chlorine resistance in a water supply and chemical fluid transportation system.

[0041] Specifically, the PE-Xa pipe material can be applied to environments with high chlorine content and extreme chlorine concentrations.

[0042] The high-chlorine environment refers to a Cl - concentration of 10 - 50 mg / L, which is applicable to tap water (residual chlorine 0.5 - 2 mg / L), pool water (3 - 5 mg / L), and mild industrial wastewater (10 - 50 mg / L).

[0043] The extreme chlorine concentration refers to a Cl - concentration > 50 mg / L, such as seawater desalination pretreatment (500 - 2000 mg / L), industrial concentrated brine (> 10,000 mg / L).

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention combines a modified hydrotalcite with "adsorption - reduction" dual functions and ion exchange resin microspheres for the first time, overcoming the problem of long-term chlorine resistance of pipes in high-chlorine environments.

[0045] (2) The present invention adopts a three-stage extrusion process, improving the dispersibility of the modified hydrotalcite and ion exchange resin microspheres, thereby improving the chlorine resistance of the PE-Xa pipe material.

[0046] (3) The present invention eliminates the stress difference between the inner and outer layers of the pipe by adopting a three-stage cooling method, improving the crack resistance of the PE-Xa pipe material. Description of the Drawings

[0047] Figure 1 is an electron micrograph of the PE-Xa pipe material after cooling by the three-stage cooling method of the present invention.

[0048] Figure 2 is an electron micrograph of the PE-Xa pipe material after cooling by the traditional cooling method. Detailed Embodiments

[0049] To better illustrate the purpose, technical solution 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 manner of the present invention are not limited thereto.

[0050] For the materials, reagents, etc. used in the following embodiments, unless otherwise specified, they are reagents and materials that can be obtained from commercial channels.

[0051] Example 1 This example discloses a PE-Xa pipe with chlorine resistance, which comprises the following raw material components in parts by weight: 100 parts of high-density polyethylene; 0.8 part of cross-linking agent; 1.2 parts of modified hydrotalcite; 0.5 part of sulfonated ion exchange resin microspheres; 0.6 part of antioxidant; 0.2 part of zinc oxide whiskers.

[0052] The high-density polyethylene includes high-density polyethylene with a high molecular weight distribution and high-density polyethylene with a low molecular weight distribution. The high-density polyethylene with a high molecular weight distribution is the high-density polyethylene of South Korea's LG XL1800 (Mw = 800,000, Mw / Mn = 8.0), and the molecular weight distribution is 8.0; the high-density polyethylene with a low molecular weight distribution is the high-density polyethylene of Saudi Arabia's SABIC PE100 (Mw = 500,000, Mw / Mn = 5.5), and the molecular weight distribution is 5.5.

[0053] The mass ratio of the high-density polyethylene with a high molecular weight distribution to the high-density polyethylene with a low molecular weight distribution is 6:4, and the difference in their molecular weight distributions is: (8 - 5.5) / 8 × 100% = 31.25%.

[0054] The cross-linking agent is dicumyl peroxide.

[0055] The antioxidant includes antioxidant 1010 and antioxidant DSTDP, and the mass ratio of the two is 2:1.

[0056] The zinc oxide whiskers have a four-needle structure. The zinc oxide whiskers are the ZnO whiskers of Panasonic, Japan, model: ZNO-30, and the aspect ratio is 20:1.

[0057] The modified hydrotalcite includes magnesium-aluminum hydrotalcite and nano-zero-valent iron loaded on the magnesium-aluminum hydrotalcite. The mass ratio of nano-zero-valent iron to magnesium-aluminum hydrotalcite in the modified hydrotalcite is 10:90.

[0058] The particle size of the magnesium-aluminum hydrotalcite is 5 μm, and the specific surface area is 200 m 2 / g; the particle size of the nano-zero-valent iron is 15 - 30 nm, and the specific surface area is 30 - 50 m 2 / g.

[0059] The preparation method of the modified hydrotalcite includes the following steps: (1) Dissolve Mg(NO3)2·6H2O (5 mol) and Al(NO3)3·9H2O (1 mol) in deionized water to prepare a mixed solution with a concentration of 0.5 mol / L.

[0060] (2) Add 2 mol / L NaOH solution dropwise to the mixed solution until the pH of the solution reaches 10, carry out a hydrothermal reaction at 80 °C for 24 h to obtain the product; then centrifuge and wash the product until it is neutral, and finally dry the product in vacuum at 60 °C and grind and screen it to obtain magnesium-aluminum hydrotalcite.

[0061] (3) Disperse 50 g of magnesium-aluminum hydrotalcite in 200 mL of ethanol, then add 50 mL of FeCl3 solution, and ultrasonically disperse for 30 min. The concentration of the FeCl3 solution is 0.1 mol / L.

[0062] (4) Add 0.5 mol / L NaBH4 solution dropwise to step (3) to reduce Fe 3+ , with a dropping rate of 0.5 mL / min, to obtain the modified hydrotalcite. Control the molar ratio of Fe 3+ :NaBH4 to be 1:3 to ensure that Fe 3+ is completely reduced to Fe, and maintain the reaction pH at 12 - 13 to stabilize nZVI.

[0063] The ion exchange resin microspheres are styrene anion resin microspheres, and the preparation method of the styrene anion resin microspheres includes the following steps: Dissolve 2 g of Span-80 in 500 mL of water to obtain a Span-80 solution; add 80 g of styrene and 20 g of divinylbenzene to the Span-80 solution and disperse evenly, and polymerize at 60 °C for 24 h to prepare styrene anion resin microspheres with a particle size of 1 - 5 μm.

[0064] The styrene anion resin microspheres are subjected to sulfonation treatment, including the following steps: Immerse 100 g of styrene anion resin microspheres in 200 mL of dichloromethane and swell for 2 h; then add 200 mL of chlorosulfonic acid (50 mL / g), stir and react in an ice-water bath (0 - 5 °C) for 4 h; then slowly pour it into ice water to terminate the reaction, filter and neutralize with 5% NaHCO3 solution until pH = 7; finally wash with ethanol 3 times and dry in vacuum at 60 °C to obtain sulfonated styrene anion resin microspheres.

[0065] This example also discloses a preparation method of a PE-Xa pipe with chlorine resistance, including the following steps: (1) Add HDPE, crosslinking agent, modified hydrotalcite, sulfonated ion exchange resin microspheres, and zinc oxide whiskers into a twin-screw mixer. The mixing temperature is 140 °C, the shear rate is 300 rpm, and the mixing time is 15 min to obtain a mixed material.

[0066] (2) Then, melt and extrude the mixed material through a three-stage extruder. The first stage (plasticization) is at 140 - 160 °C, the second stage (dynamic crosslinking) is at 200 - 230 °C, the third stage (shaping) is at 180 - 200 °C, the die head pressure is 15 - 20 MPa, and the extrusion speed is 1.5 m / min.

[0067] (3) Finally, cool it using a three-stage cooling water tank, and the PE-Xa pipe with chlorine resistance is obtained after cooling.

[0068] The temperature gradient of the three-stage cooling water tank is set as follows: The first stage: 80 - 90 °C (slow cooling at high temperature to promote inner layer crosslinking); The second stage: 50 - 60 °C (medium temperature shaping to balance the stress between the inner and outer layers); The third stage: 20 - 30 °C (rapid cooling at low temperature to lock the crosslinked structure); The cooling water flow rates in the first stage, the second stage, and the third stage are distributed according to the ratio of 1:2:3 to ensure synchronous cooling of the inner and outer layers of the pipe, reduce the difference in thermal stress, and the total cooling time is 120 s.

[0069] Example 2 A PE-Xa pipe with chlorine resistance, different from Example 1, wherein the PE-Xa pipe comprises the following raw material components in parts by weight: 100 parts of high-density polyethylene; 0.2 part of crosslinking agent; 1.5 parts of modified hydrotalcite; 0.8 part of sulfonated ion exchange resin microspheres; 0.3 part of antioxidant; 0.3 part of zinc oxide whiskers.

[0070] Example 3 A PE-Xa pipe with chlorine resistance, different from Example 1, wherein the PE-Xa pipe comprises the following raw material components in parts by weight: 100 parts of high-density polyethylene; 1 part of crosslinking agent; 0.5 part of modified hydrotalcite; 0.3 part of sulfonated ion exchange resin microspheres; 1 part of antioxidant; 0.1 part of zinc oxide whiskers.

[0071] Example 4 A PE-Xa pipe with chlorine resistance, different from Example 1, wherein the mass ratio of nano-zero-valent iron to magnesium-aluminum hydrotalcite in the modified hydrotalcite is 5:95.

[0072] Example 5 A PE-Xa pipe with chlorine resistance, different from Example 1, wherein the mass ratio of nano-zero-valent iron to magnesium-aluminum hydrotalcite in the modified hydrotalcite is 15:85.

[0073] Example 6 A PE-Xa pipe with chlorine resistance performance, which is different from that of Example 1 in that the high-density polyethylene includes high-density polyethylene with a high molecular weight distribution and high-density polyethylene with a low molecular weight distribution. The high-density polyethylene with a high molecular weight distribution is the high-density polyethylene of Mitsui 5602 in Japan (Mw = 900,000, Mw / Mn = 7.0), and the molecular weight distribution is 7.0; the high-density polyethylene with a low molecular weight distribution is the high-density polyethylene of Borealis HE3490-LS (Mw = 600,000, Mw / Mn = 4.0), and the molecular weight distribution is 4.0.

[0074] The mass ratio of the high-density polyethylene with a high molecular weight distribution to the high-density polyethylene with a low molecular weight distribution is 5:5, and the difference in their molecular weight distributions is: (7 - 4) / 7×100% = 42.86%.

[0075] Example 7 A PE-Xa pipe with chlorine resistance performance, which is different from that of Example 1 in that the zinc oxide whiskers are four-needle-shaped structures, and the oxidation whiskers are ZnO whiskers of Merck KGaA in Germany, model: ZnO-Tetra-25, and the aspect ratio is 25:1.

[0076] Example 8 A PE-Xa pipe with chlorine resistance performance, which is different from that of Example 1 in that the ion exchange resin microspheres are polyacrylic acid anion resin microspheres.

[0077] The polyacrylic acid anion resin microspheres are Amberlite™ IRC120 (H+ type) of Dow Chemical in the United States and are converted into an anion form by alkali treatment.

[0078] Example 9 A PE-Xa pipe with chlorine resistance performance, which is different from that of Example 1 in that the ion exchange resin microspheres are epoxy group anion resin microspheres.

[0079] The epoxy group anion resin microspheres are Lewatit® MK 51 (epoxy group modified) of Lanxess in Germany.

[0080] Example 10 A PE-Xa pipe with chlorine resistance performance, which is different from that of Example 1 in that the ion exchange resin microspheres are quaternized styrene resin microspheres.

[0081] The quaternized styrene resin microspheres are Purolite® A520E (quaternized styrene resin) of Purolite in the United Kingdom.

[0082] Comparative Example 1 A PE-Xa pipe with chlorine resistance performance, which is different from Example 1 in that ion exchange resin microspheres are not added to the raw material components of the PE-Xa pipe.

[0083] Comparative Example 2 A PE-Xa pipe with chlorine resistance performance, which is different from Example 1 in that modified hydrotalcite is not added to the raw material components of the PE-Xa pipe.

[0084] Comparative Example 3 A PE-Xa pipe with chlorine resistance performance, which is different from Example 1 in that zinc oxide whiskers are not added to the raw material components of the PE-Xa pipe.

[0085] Comparative Example 4 A PE-Xa pipe with chlorine resistance performance, which is different from Example 1 in that in the raw material components of the PE-Xa pipe, equal mass of magnesium-aluminum hydrotalcite is used to replace the modified hydrotalcite, that is, the magnesium-aluminum hydrotalcite is not loaded with nano-zero-valent iron.

[0086] Comparative Example 5 A PE-Xa pipe with chlorine resistance performance, which is different from Example 1 in that the mass ratio of nano-zero-valent iron to magnesium-aluminum hydrotalcite in the modified hydrotalcite is 1:99.

[0087] Comparative Example 6 A PE-Xa pipe with chlorine resistance performance, which is different from Example 1 in that the mass ratio of nano-zero-valent iron to magnesium-aluminum hydrotalcite in the modified hydrotalcite is 20:80.

[0088] Comparative Example 7 A PE-Xa pipe with chlorine resistance performance, which is different from Example 1 in that the styrene anion resin microspheres are not sulfonated.

[0089] Performance Testing 1. Crosslinking degree: Tested according to the xylene extraction method (ASTM D2765-16(2024)): The crosslinking degree is calculated by the mass of insoluble matter.

[0090] 2. Chloride ion adsorption capacity: Tested according to GB / T 12496.1-1999, test conditions: Oscillating adsorption at 25 °C for 24 h.

[0091] 3. Hypochlorous acid reduction rate: The change in the concentration of HClO in the solution is detected by UV-Vis, test conditions: UV-Vis detection at 25 °C (λ = 292 nm).

[0092] 4. Long-term chlorine residue rate: The pipe is immersed in 20 mg / L Cl- Measured after 12 weeks for the solution (pH 6.5).

[0093] 5. Hydrostatic strength: Tested according to ASTM D1598 - 24 standard, test conditions: 95 °C, 1000 h.

[0094] 6. Crack resistance performance: Tested according to ASTM D1693 - 21 (Environmental Stress Cracking Test).

[0095] The above test results are shown in Table 1.

[0096] Table 1 It can be seen from Table 1 that the PE-Xa pipe described in the present invention has a high degree of crosslinking, and also has excellent chlorine resistance and crack resistance performance.

[0097] It can be seen from Examples 1, 4, and 5 that by controlling the mass ratio of nano zero-valent iron to magnesium-aluminum hydrotalcite to be (5 - 15):(85 - 95) in the present invention, the PE-Xa pipe can simultaneously have excellent chlorine resistance and crack resistance performance.

[0098] It can be seen from Examples 1, 8 - 10 that the ion exchange resin microspheres described in the present invention are selected from styrene anion resin microspheres, polyacrylic acid anion resin, epoxy group anion resin or quaternized styrene resin, which is beneficial to improving the chlorine resistance and crack resistance performance of the PE-Xa pipe.

[0099] By comparing Comparative Examples 1 - 3 with Example 1 respectively, it can be obtained that in Comparative Example 1, no ion exchange resin microspheres are added, in Comparative Example 2, no modified hydrotalcite is added, and in Comparative Example 3, no zinc oxide whiskers are added. The chlorine ion adsorption capacity in Comparative Examples 1 - 3 decreases, the long-term chlorine residue rate is higher than that in Example 1, and the crack resistance performance is also inferior to that in Example 1. This shows that by using the synergistic effect of modified hydrotalcite, ion exchange resin microspheres and zinc oxide whiskers in the present invention, it is not only beneficial to improve the chlorine resistance of the PE-Xa pipe, but also beneficial to improve the crack resistance performance of the PE-Xa pipe.

[0100] By comparing Comparative Example 4 with Example 1, it can be obtained that in Comparative Example 4, the magnesium-aluminum hydrotalcite is not loaded with nano zero-valent iron, the hypochlorous acid reduction rate significantly decreases, and the chlorine ion adsorption capacity also decreases, indicating that only when the magnesium-aluminum hydrotalcite is loaded with nano zero-valent iron and reduces hypochlorous acid while adsorbing Cl - can the adsorption amount of chlorine ions be significantly increased, thereby improving the chlorine resistance of the PE-Xa pipe.

[0101] Comparing Comparative Examples 5-6 with Example 1 respectively, it can be seen that in Comparative Example 5, the mass ratio of nano-zero-valent iron to magnesium-aluminum hydrotalcite is too small, and the content of nano-zero-valent iron is too low, resulting in a decrease in the ability of the modified hydrotalcite to adsorb chloride ions; in Comparative Example 6, the mass ratio of nano-zero-valent iron to magnesium-aluminum hydrotalcite is too large, and the content of nano-zero-valent iron is too high, which makes the nano-zero-valent iron prone to agglomeration, reducing its specific surface area. At the same time, it will also damage the structure of magnesium-aluminum hydrotalcite, leading to a decline in the adsorption capacity of the modified hydrotalcite. Therefore, by controlling the mass ratio of nano-zero-valent iron to magnesium-aluminum hydrotalcite within the range defined in the present invention, it is beneficial to improve the ability of the modified hydrotalcite to adsorb chloride ions, thereby improving the chlorine resistance of PE-Xa pipes.

[0102] Comparing Comparative Example 7 with Example 1, it can be seen that in Comparative Example 7, the ion exchange resin microspheres were not sulfonated, resulting in a decrease in the chloride ion exchange capacity, indicating that the chloride ion exchange capacity of the unsulfonated resin microspheres is relatively low. In the present invention, by sulfonating the ion exchange resin microspheres, it is beneficial to improve the ion exchange efficiency, thereby improving the chlorine resistance of PE-Xa pipes.

[0103] Figure 2 is the electron micrograph after cooling by the traditional cooling method, that is, the extruded pipe is directly immersed in a normal temperature water bath for rapid cooling. From Figure 2 , many small cracks can be seen, indicating that due to the excessive temperature difference between the inner and outer layers, the thermal stress distribution is uneven, and microcracks are easily induced. In contrast, the three-stage gradient cooling (80-90°C → 50-60°C → 20-30°C) of the present invention effectively balances the stress and inhibits crack formation by regulating the cooling rate in stages (as shown in Figure 1 ), indicating that using the three-stage cooling method described in the present invention for cooling can improve the crack resistance of PE-Xa pipes.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A PE-Xa pipe with chlorine resistance performance, characterized in that, It comprises the following raw material components in parts by weight: 100 parts of high-density polyethylene; 0.2 - 1 part of cross-linking agent; 0.5 - 1.5 parts of modified hydrotalcite; 0.3 - 0.8 part of sulfonated ion exchange resin microspheres; 0.3 - 1 part of antioxidant; 0.1 - 0.3 part of zinc oxide whiskers; The modified hydrotalcite includes magnesium-aluminum hydrotalcite and nano zero-valent iron loaded on the magnesium-aluminum hydrotalcite, and the mass ratio of nano zero-valent iron to magnesium-aluminum hydrotalcite in the modified hydrotalcite is (5 - 15):(85 - 95); The sulfonated ion exchange resin microspheres are obtained by sulfonating ion exchange resin microspheres, and the ion exchange resin microspheres include at least one of styrene anion resin microspheres, polyacrylic acid anion resin microspheres, epoxy group anion resin microspheres, and quaternized styrene resin microspheres.

2. The PE-Xa pipe with chlorine resistance as described in claim 1, characterized in that, The high-density polyethylene includes high-density polyethylene with a high molecular weight distribution and high-density polyethylene with a low molecular weight distribution. The molecular weight distribution of the high-density polyethylene with a high molecular weight distribution is A, and the molecular weight distribution of the high-density polyethylene with a low molecular weight distribution is B. A and B satisfy the following relationship: 100%×(A - B) / A = 30% - 50%; And the mass ratio of the high-density polyethylene with a high molecular weight distribution to the high-density polyethylene with a low molecular weight distribution is (5 - 6):(4 - 5).

3. The PE-Xa pipe with chlorine resistance according to claim 1, characterized in that The particle size of the magnesium aluminum hydrotalcite is 0.1 - 5 μm, and the specific surface area is 180 - 250 m 2 / g; And / or, the particle size of the nano zero-valent iron is 15 - 30 nm, and the specific surface area is 30 - 50 m 2 / g.

4. The PE-Xa pipe with chlorine resistance according to claim 1, characterized in that, The preparation method of the modified hydrotalcite includes the following steps: Disperse magnesium-aluminum hydrotalcite in an organic solvent to obtain a dispersion; then add an iron ion solution to the dispersion, mix evenly and then dropwise add sodium borohydride solution to obtain the modified hydrotalcite.

5. The PE-Xa pipe with chlorine resistance according to claim 1, characterized in that The particle size of the sulfonated ion exchange resin microspheres is 1 - 5 μm.

6. The PE-Xa pipe with chlorine resistance according to claim 1, wherein, The preparation method of the sulfonated ion exchange resin microspheres includes the following steps: Swell the ion exchange resin microspheres in dichloromethane; then add chlorosulfonic acid, sulfonate at 0 - 5 °C for 1 - 2 h, wash with water until neutral, and dry to obtain the sulfonated ion exchange resin microspheres.

7. The PE-Xa pipe with chlorine resistance according to claim 1, characterized in that, The zinc oxide whiskers are in a four-needle structure, and the aspect ratio of a single needle is (20 - 50):

1.

8. A method for preparing a PE-Xa pipe with chlorine resistance as described in any one of claims 1-7, characterized in that, It includes the following steps: Add high-density polyethylene, cross-linking agent, antioxidant, modified hydrotalcite, sulfonated ion exchange resin microspheres, and zinc oxide whiskers into a mixer, mix evenly to obtain a mixture; then melt and extrude the mixture in an extruder, and cool to obtain the PE-Xa pipe with chlorine resistance.

9. The preparation method of the PE-Xa pipe with chlorine resistance as claimed in claim 8, characterized in that, The extruder is a three-stage extruder: the temperature range of the first stage is 140 - 160 °C, the temperature range of the second stage is 200 - 230 °C, the temperature range of the third stage is 180 - 200 °C, the die head pressure of the extruder is 15 - 20 MPa, and the extrusion speed is 1.5 - 2.5 m / min; And / or, use a three-stage cooling water tank for cooling, and the temperature gradient is set as: the first stage: 80 - 90 °C, the second stage: 50 - 60 °C, the third stage: 20 - 30 °C; And / or, the temperature during mixing is 120 - 140 °C, the shear rate is 200 - 400 rpm, and the mixing time is 10 - 15 min.

10. Application of a PE-Xa pipe with chlorine resistance according to any one of claims 1 - 7 in a water supply and chemical fluid transportation system.

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