High-temperature-resistant high-toughness HDPE (high-density polyethylene) double-wall corrugated pipe and preparation method thereof

Abstract

According to the high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe and the preparation method thereof, through the raw material formula, the alpha crystal form nucleating agent, the organic modified montmorillonite, the elastomer toughening agent, the specific compatilizer, the lubricating agent and the antioxidant system containing the hydrazinium salicylate are scientifically proportioned, the montmorillonite modification technology is optimized, and the high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe is obtained. The surface of the modified montmorillonite is driven to be enriched to form a high-temperature-resistant functional layer, and parameters such as melt blending temperature and time, adsorption molding pressure control and gradient cooling are accurately regulated and controlled. Performance tests show that the thermal deformation temperature of the pipe is higher than 135 DEG C, the creep rate is as low as 3.2%, the impact strength reaches 43.5 kJ / m < 2 >, the tensile strength retention rate reaches 85% or above, the ring stiffness is stabilized to be about 9 kN / m < 2 >, and the obtained pipe has high ring stiffness, high impact strength and ultralow creep rate and can stably serve for a long time in a high-temperature environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of HDPE double-wall corrugated pipe processing, in particular to a high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe and a preparation method thereof. BACKGROUND

[0002] High-density polyethylene (HDPE) double-wall corrugated pipes are widely used in municipal engineering and power cable protection fields due to their light weight, corrosion resistance, and convenient construction, etc. The unique double-layer hollow structure design of the pipes effectively reduces material consumption while ensuring ring stiffness by optimizing the cross-section mechanical distribution. Compared with traditional metal pipes, the HDPE double-wall corrugated pipes not only significantly reduce construction load, but also significantly shorten construction period and reduce comprehensive cost, thereby promoting the technological innovation and sustainable development of related industries.

[0003] However, with the acceleration of urbanization and the complexity of industrial application scenarios, the existing HDPE double-wall corrugated pipe technology faces many bottlenecks that need to be broken through: (1) The traditional HDPE corrugated pipe is prone to softening and deformation in a high-temperature environment, and the ring stiffness and creep resistance decrease, which increases the risk of pipe collapse. (2) The existing technology relies on a high proportion of recycled materials or ordinary fillers, which results in insufficient pipe toughness and high cost. (3) The existing toughening modification mostly uses rubber blending, which causes a 20-30% decrease in ring stiffness, and it is difficult to balance the impact resistance and temperature resistance. SUMMARY

[0004] Therefore, the present application provides a high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe and a preparation method thereof to solve the above problems.

[0005] The technical scheme of the present application is implemented as follows: A high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe comprises the following raw materials by weight: 85-92 parts of HDPE resin, 0.3-0.5 parts of an alpha crystal nucleating agent, 2-4 parts of organically modified montmorillonite, 3-5 parts of a compatibilizer, 2-8 parts of an elastomer toughening agent, 0.5-1.5 parts of a lubricant, and 0.2-0.8 parts of an antioxidant, wherein the organically modified montmorillonite is nano-montmorillonite treated with a silane coupling agent on the surface and having an interlayer spacing of ≥2.8 nm.

[0006] Further, the following raw materials by weight are included: 90 parts of HDPE resin, 0.4 parts of an alpha crystal nucleating agent, 3 parts of organically modified montmorillonite, 4 parts of a compatibilizer, 5 parts of an elastomer toughening agent, 1 part of a lubricant, and 0.5 parts of an antioxidant.

[0007] Further, the alpha crystal nucleating agent is a sorbitol nucleating agent, which is any one of dibenzylidene sorbitol (DBS), 1,3;2,4-bis(p-methylbenzylidene)sorbitol (MDBS), or di(3,4-dimethyl dibenzylidene)sorbitol (DMDBS) and has a particle size D50≤5 μm.

[0008] Further, the compatibilizer is a mixture of one or more of maleic anhydride grafted polyethylene (POE-g-MAH), ethylene-methyl acrylate copolymer (EMA) or ethylene-glycidyl methacrylate copolymer.

[0009] Further, the elastomer toughening agent is hydrogenated styrene-butadiene-styrene block copolymer (SEBS) or polyolefin elastomer (POE).

[0010] Further, the lubricant is calcium stearate, oxidized polyethylene wax and microcrystalline wax in a mass ratio of (3-7):(5-10):(1-3).

[0011] Further, the antioxidant is a compound system composed of hindered phenolic antioxidant 1010, phosphite antioxidant 168 and hydrazine salicylate in a mass ratio of (5-7):(2-3):(1-2).

[0012] Further, a preparation method of a high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe, comprising the following steps: (1) Montmorillonite modification: disperse the montmorillonite in ethanol, add silane coupling agent KH550, stir and react at 50-70°C for 3-5 hours, filter, wash and dry after the reaction to obtain modified montmorillonite with an interlayer spacing of 2.8-3.5 nm; the mass ratio of the silane coupling agent KH550 to the montmorillonite is (1-3):10; (2) Pre-mixing: dry mix the HDPE resin, α-crystal nucleating agent, organic modified montmorillonite and compatibilizer in a high-speed mixer at 500-1000 rpm and 80-100°C for 3-5 min; (3) Melt blending: add the pre-mixed material into a twin-screw extruder, extrude and granulate at a temperature of 170-200°C and a screw speed of 200-300 rpm to obtain modified masterbatch; (4) Corrugated pipe forming: deliver the modified masterbatch to a corrugated pipe forming machine, melt and plasticize at 200-220°C, adopt vacuum adsorption forming by inner and outer molds, then cool, size and cut to obtain the high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe.

[0013] Further, in step (4), the outer mold adsorption pressure is 0.4-0.6 MPa, the inner mold adsorption pressure is 0.2-0.4 MPa, and the vacuum adsorption time is ≥15 s.

[0014] Further, in step (4), the cooling process adopts gradient cooling: the first-stage water cooling temperature is 50±5°C, and the cooling time is ≥30 s; the second-stage water cooling temperature is 25±3°C, and the pipe wall temperature is ≤40°C after cooling.

[0015] Compared with the prior art, the application has the following advantages: (1) Excellent high-temperature resistance: By adding a specific proportion of an α crystal form nucleating agent and modified montmorillonite, a nano-composite reinforcing system is formed, the crystallization morphology of the HDPE resin is optimized, the pipe material can be used for a long time in an environment of 85°C, the high-temperature-resistant insulation layer formed on the surface of the pipe material effectively inhibits the thermal motion of molecular chain segments at high temperatures, and the ring stiffness can still remain ≥9 kN / m 2 , significantly reducing the risk of pipe body collapse.

[0016] (2) Synergistic improvement of mechanical properties: By using the synergistic effect of an elastomer toughening agent and a compatibilizer, the impact strength of the pipe material is greatly improved while the ring stiffness is ensured. The impact strength of the pipe material reaches 43.5 kJ / m 2 , and the ring stiffness does not decrease significantly, achieving a balance between high toughness and high stiffness.

[0017] (3) Precise control of process parameters: The whole process from montmorillonite modification to corrugated pipe forming is optimized, including specific modification temperature and time, speed and temperature control of a high-speed mixer, and parameter setting of a double-screw extruder and vacuum adsorption forming, to ensure uniform dispersion of each component and improve the stability of the comprehensive performance of the material. Process control such as gradient cooling avoids stress concentration in the pipe material and improves the yield of the product. DETAILED DESCRIPTION

[0018] In order to better understand the technical content of the application, the following specific examples are provided to further illustrate the application.

[0019] The experimental methods used in the embodiments of the application are conventional methods unless otherwise specified.

[0020] The materials, reagents, etc. used in the embodiments of the application can be obtained from commercial channels unless otherwise specified.

[0021] Example 1 A high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe comprises the following raw materials by weight: 85 parts of HDPE resin, 0.3 parts of an α crystal form nucleating agent, 2 parts of organically modified montmorillonite, 3 parts of a compatibilizer, 2 parts of an elastomer toughening agent, 0.5 parts of a lubricant, and 0.2 parts of an antioxidant. Among them: The α crystal form nucleating agent is DBS, and the particle size D50 is ≤5 μm; The compatibilizer is maleic anhydride grafted polyethylene (POE-g-MAH); The elastomer toughening agent is hydrogenated styrene-butadiene-styrene block copolymer (SEBS); The lubricant is calcium stearate, oxidized polyethylene wax and microcrystalline wax in a mass ratio of 3:5:1. The antioxidant is a compound system composed of hindered phenolic antioxidant 1010, phosphite antioxidant 168 and hydrazine salt of salicylic acid in a mass ratio of 5:2:1.

[0022] Embodiment 2 A high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe comprises the following raw materials in parts by weight: HDPE resin 92 parts, alpha crystal nucleating agent 0.5 part, organic modified montmorillonite 4 parts, compatibilizer 5 parts, elastomer toughening agent 8 parts, lubricant 1.5 parts, antioxidant 0.8 part; Among them: The alpha crystal nucleating agent is MDBS, and the particle size D50 is ≤5 μm; The compatibilizer is ethylene-methyl acrylate copolymer (EMA); The elastomer toughening agent is polyolefin elastomer (POE); The lubricant is calcium stearate, oxidized polyethylene wax and microcrystalline wax in a mass ratio of 7:10:-3; The antioxidant is a compound system composed of hindered phenolic antioxidant 1010, phosphite antioxidant 168 and hydrazine salt of salicylic acid in a mass ratio of 7:3:2.

[0023] Embodiment 3 A high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe comprises the following raw materials in parts by weight: HDPE resin 90 parts, alpha crystal nucleating agent 0.4 part, organic modified montmorillonite 3 parts, compatibilizer 4 parts, elastomer toughening agent 5 parts, lubricant 1 part, antioxidant 0.5 part; Among them: The alpha crystal nucleating agent is DMDBS, and the particle size D50 is ≤5 μm; The compatibilizer is ethylene-methyl acrylate copolymer; The elastomer toughening agent is polyolefin elastomer (POE); The lubricant is calcium stearate, oxidized polyethylene wax and microcrystalline wax in a mass ratio of 5:8:2; The antioxidant is a compound system composed of hindered phenolic antioxidant 1010, phosphite antioxidant 168 and hydrazine salt of salicylic acid in a mass ratio of 6:2.5:1.5. The above embodiments 1-3 are prepared by the following method: (1) Montmorillonite modification: disperse montmorillonite in ethanol, add silane coupling agent KH550, stir and react at 60℃ for 4 hours, filter, wash and dry after the reaction to obtain modified montmorillonite with an interlayer spacing of 3.0 nm; the mass ratio of the silane coupling agent KH550 to montmorillonite is 2:10; (2) Premixing: the HDPE resin, the alpha crystal nucleating agent, the organically modified montmorillonite and the compatibilizer were dry mixed in a high-speed mixer at 800 rpm and 90℃ for 4 min; (3) Melt blending: the premixed material was added into a twin-screw extruder and extruded and granulated at a temperature of 180℃ and a screw rotation speed of 250 rpm to obtain a modified masterbatch; (4) Corrugated pipe forming: the modified masterbatch was transported to a corrugated pipe forming machine, melted and plasticized at 210℃, and then formed by vacuum adsorption with an inner and outer mold, the outer mold adsorption pressure was 0.5 MPa, the inner mold adsorption pressure was 0.3 MPa, the vacuum adsorption time was ≥15 s, and then the pipe was cooled, sized and cut to obtain a corrugated pipe, The cooling process adopted gradient cooling: The first-stage water cooling temperature was 50℃, and the cooling time was 35 s; The second-stage water cooling temperature was 25℃, and the pipe wall temperature was 30℃ after cooling.

[0024] Comparative Example 1 The difference between this comparative example and Example 3 was that no elastomer toughening agent was added.

[0025] Comparative Example 2 The difference between this comparative example and Example 3 was that the montmorillonite was not modified.

[0026] Comparative Example 3 The difference between this comparative example and Example 3 was that the antioxidant system was not salicylic acid hydrazine salt, but 1010+168 two-component (6:4).

[0027] Comparative Example 4 The difference between this comparative example and Example 3 was that no alpha crystal nucleating agent was added to the raw materials.

[0028] Comparative Example 5 The difference between this comparative example and Example 3 was that the outer mold adsorption pressure in step (4) was 0.3 MPa, and the inner mold adsorption pressure was 0.1 MPa.

[0029] Comparative Example 6 The difference between this comparative example and Example 3 was that no gradient cooling was performed in step (4), and the pipe was directly cooled by water at 25℃.

[0030] Performance test: The corrugated pipes prepared in Examples 1-3 and Comparative Examples 1-6 were tested, and the test items and standards are shown in Table 1 below:

[0031] Tensile strength retention rate (%) after weathering aging = tensile strength of the sample after aging / tensile strength of the sample before aging x 100% The test results are shown in Table 2 below:

[0032] The above results show that the example group of the application maintains ring stiffness > 9 kN / m 2 while achieving impact strength > 40 kJ / m 2 , and heat distortion temperature > 130℃.

[0033] Comparing example 3 with comparative example 1, the elastomer toughening agent provides a flexible support skeleton for the α crystal / montmorillonite system, and the impact strength is increased by nearly 87.5% compared with comparative example 1, which fully reflects the key role of the elastomer toughening agent in enhancing the toughness of the pipe material. Comparative example 1 has no elastic buffer network, and the molecular chain is more prone to oxidation and rupture, so the tensile strength retention rate decreases significantly.

[0034] Comparative example 2 uses unmodified montmorillonite, and the ring stiffness and heat distortion temperature are poor, and the creep rate increases. The interlayer spacing of montmorillonite is insufficient, and the agglomerates hinder the crosslinking of the molecular chain. It is shown that the modification treatment (2.8-3.5 nm) can significantly enhance the compatibility of montmorillonite and HDPE resin, accommodate the insertion of HDPE molecular chain, enhance the bonding force of polymer-filler interface, reduce agglomeration, improve dispersibility, and improve the comprehensive performance of the pipe material. The tensile strength retention rate of comparative example 3 after weathering and aging decreases significantly, and the antioxidant system fails to accelerate material aging, which shows that hydrazine salt of salicylic acid can block the high-temperature catalytic oxidation chain reaction by chelating metal ions.

[0035] Comparative example 4 has no α crystal buffer interface, and the thermal stress directly damages the rigid network, so the ring stiffness at 85℃ is 8.5 kN / m 2 , which shows that the rigid and tough balance effect of the α crystal nucleating agent in example 3 is more outstanding in structure strength and toughness, and solves the contradiction between toughening and heat resistance.

[0036] Comparative example 5 has a lower driving effect of nanometer montmorillonite migration under an adsorption pressure <0.4 MPa, which leads to insufficient thickness of the nanometer functional layer. Comparative example 6 generates shrinkage stress and causes microcracks due to quenching. Comparative examples 5 and 6 change the mold adsorption pressure and cooling process, which leads to a decrease in ring stiffness, impact strength, and creep performance. It is shown that precise control of the molding process parameters is the key to ensuring the mechanical properties of the pipe material.

[0037] The above only describes the preferred embodiments of the application and is not intended to limit the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A high-temperature resistant and high-toughness HDPE double-wall corrugated pipe, characterized by: The invention comprises the following raw materials in parts by weight: 85-92 parts of HDPE resin, 0.3-0.5 parts of α-crystal nucleating agent, 2-4 parts of organic modified montmorillonite, 3-5 parts of compatibilizer, 2-8 parts of elastomer toughening agent, 0.5-1.5 parts of lubricant, and 0.2-0.8 parts of antioxidant. The organic modified montmorillonite is nano-montmorillonite that has been surface-treated with a silane coupling agent and has an interlayer spacing of ≥2.8 nm.

2. The high-temperature resistant and high-toughness HDPE double-wall corrugated pipe according to claim 1, characterized in that: The method comprises the following raw materials in parts by weight: 90 parts of HDPE resin, 0.4 parts of α-crystal nucleating agent, 3 parts of organic modified montmorillonite, 4 parts of compatibilizer, 5 parts of elastomer toughening agent, 1 part of lubricant and 0.5 parts of antioxidant.

3. The high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe according to claim 1, characterized in that: The α-crystal nucleating agent is a sorbitol nucleating agent, which is any one of dibenzylidene sorbitol, 1,3;2,4-di(p-methylbenzylidene) sorbitol or di(3,4-dimethyldibenzylidene) sorbitol, and its particle size D50 is ≤5μm.

4. The high-temperature resistant and high-toughness HDPE double-wall corrugated pipe according to claim 1, characterized in that: The compatibilizer is a mixture of one or more of maleic anhydride grafted polyethylene, ethylene-methyl acrylate copolymer, or ethylene-glycidyl methacrylate copolymer.

5. The high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe according to claim 1, characterized in that: The elastomer toughening agent is a hydrogenated styrene-butadiene-styrene block copolymer or a polyolefin elastomer.

6. The high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe according to claim 1, characterized in that: The lubricant comprises calcium stearate, oxidized polyethylene wax and microcrystalline wax in a mass ratio of (3-7):(5-10):(1-3).

7. The high-temperature-resistant and high-toughness HDPE double-wall corrugated pipe according to claim 1, characterized in that: The antioxidant is a compound system composed of hindered phenol antioxidant 1010, phosphite antioxidant 168 and salicylic acid hydrazine salt in a mass ratio of (5-7):(2-3):(1-2).

8. The method for preparing a high-temperature resistant and high-toughness HDPE double-wall corrugated pipe according to claim 1, characterized in that: The following steps are involved: (1) Montmorillonite modification: Montmorillonite was dispersed in ethanol, and a silane coupling agent KH550 was added. The mixture was stirred at 50-70°C for 3-5 hours. After the reaction, the mixture was filtered, washed, and dried to obtain a modified montmorillonite with an interlayer spacing of 2.8-3.5 nm. The mass ratio of the silane coupling agent KH550 to the montmorillonite was (1-3):

10. (2) Premixing: dry mix HDPE resin, α-crystal nucleating agent, organic modified montmorillonite and compatibilizer in a high-speed mixer at 500-1000 rpm and 80-100°C for 3-5 minutes; (3) Melt blending: Add the premix to a twin-screw extruder and extrude into pellets at a temperature of 170-200°C and a screw speed of 200-300 rpm to obtain a modified masterbatch; (4) Corrugated pipe molding: The modified masterbatch is transported to the corrugated pipe molding machine, melted and plasticized at 200-220℃, and then vacuum-adsorbed by inner and outer double molds. After cooling, sizing, and cutting, a high-temperature resistant and high-toughness HDPE double-wall corrugated pipe is obtained.

9. The method for preparing a high-temperature resistant and high-toughness HDPE double-wall corrugated pipe according to claim 8, characterized in that: In step (4), the outer mold adsorption pressure is 0.4-0.6 MPa, the inner mold adsorption pressure is 0.2-0.4 MPa, and the vacuum adsorption time is ≥15 s.

10. The method for preparing a high-temperature resistant and high-toughness HDPE double-wall corrugated pipe according to claim 8, characterized in that: The cooling process in step (4) adopts gradient cooling: The first-level water cooling temperature is 50±5℃, and the cooling time is ≥30s; The secondary water cooling temperature is 25±3℃, cooling to the tube wall temperature ≤40℃.

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