A star-shaped pipe and a preparation method thereof

Abstract

This invention discloses a plum blossom tube, comprising the following raw materials: high-density polyethylene, metallocene-catalyzed linear low-density polyethylene, ethylene-octene copolymer elastomer, modified nano-calcium carbonate, processing aids, and antioxidants. The plum blossom tube has an elongation at break ≥250%, a wall thickness deviation ≤±0.20mm, and its appearance does not deform during extrusion production.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite material molding and processing technology, and specifically relates to a plum blossom tube and its preparation method. Background Technology

[0002] Plum blossom pipe is an integrated, porous, shaped sheathed pipe made primarily of high-density polyethylene through extrusion molding. Due to its advantages such as insulation and corrosion resistance, convenient construction, and low overall cost, it is widely used in 5G communication base stations, municipal underground pipe networks, power cable laying, and low-voltage electrical engineering. According to relevant industry standards, plum blossom pipe has a breaking elongation of ≥250%, a wall thickness deviation allowable within ±0.5mm, and the pipe's appearance must be free from defects such as twisting, edge collapse, warping, hole deformation, and weld line cracking.

[0003] Currently, the following problems are commonly found in the production of plum blossom tubes using traditional manufacturing techniques in the industry: Severe deformation during extrusion molding occurs due to the low melt strength of pure HDPE resin. The plum blossom tube has a complex porous irregular cross-sectional structure, and its self-support capacity is insufficient after the melt is extruded. It is prone to thermal creep, edge collapse, out-of-round hole shape, and overall warping deformation. Once the shape is set, it cannot be repaired, which directly leads to a high scrap rate.

[0004] Porous cross-sections have poor wall thickness uniformity. Traditional formulations have poor melt flowability and obvious pulsation during extrusion. The melt is unevenly distributed in the flow channel, resulting in excessive deviations in the circumferential wall thickness and the wall thickness at each hole. In actual production, the wall thickness deviation generally reaches ±0.60mm-±1.0mm, which exceeds the standard allowable range. Local thinner wall thickness will significantly reduce the mechanical properties and service life of the pipe.

[0005] The difficulty in achieving the required elongation at break and the inability to balance strength and toughness present an irreconcilable contradiction in conventional technologies in the industry: adding ordinary inorganic fillers to improve rigidity and resistance to deformation leads to a decrease in material toughness, with some products having an elongation at break below the standard lower limit of 250%; simply adding elastomers for toughening results in insufficient pipe rigidity, lower melt strength, and further aggravated extrusion deformation, making it impossible to achieve a synergistic improvement in rigidity, toughness, and melt strength.

[0006] Most of the currently disclosed related technologies only employ conventional methods such as single toughening, single filler modification, and single temperature parameter adjustment. Some technologies rely on improvements to mold structure and die flow channels to achieve better results, which not only results in high modification costs and poor versatility, but also leads to severe homogenization of technical solutions. Therefore, there is an urgent need in this field for a technical solution that can simultaneously solve the three core problems of extrusion deformation, uneven wall thickness, and low elongation at break without modifying molds and equipment, relying solely on material formulation and preparation process innovation. Summary of the Invention

[0007] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a plum blossom tube and its preparation method, wherein the plum blossom tube has an elongation at break ≥250%, a wall thickness deviation ≤±0.20mm, and its appearance does not deform during extrusion production.

[0008] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A plum blossom tube comprises the following raw materials: high-density polyethylene, metallocene-catalyzed linear low-density polyethylene, ethylene-octene copolymer elastomer, modified nano-calcium carbonate, processing aids, and antioxidants.

[0009] In some embodiments of the present invention, the plum blossom tube comprises the following raw materials in parts by weight: high-density polyethylene: 80-120 parts; metallocene-catalyzed linear low-density polyethylene: 12-18 parts; ethylene-octene copolymer elastomer: 5-8 parts; modified nano-calcium carbonate: 4-6 parts; processing aids: 0.4-0.6 parts; antioxidants: 0.3-0.5 parts.

[0010] In some embodiments of the present invention, the high-density polyethylene is PE100 grade high-density polyethylene.

[0011] In some embodiments of the present invention, the melt flow rate of the high-density polyethylene under test conditions of 190°C / 2.16kg is 0.35-0.45g / 10min.

[0012] In some embodiments of the present invention, the density of the high-density polyethylene is 0.950-0.955 g / cm³.

[0013] In some embodiments of the present invention, the melt strength of the metallocene-catalyzed linear low-density polyethylene is ≥10 cN.

[0014] In some embodiments of the present invention, the octene monomer content of the ethylene-octene copolymer elastomer is 25%-30%, and the melt strength of the ethylene-octene copolymer elastomer is ≥12cN.

[0015] In some embodiments of the present invention, the modified nano-calcium carbonate is nano-calcium carbonate that has been surface-modified with a titanate coupling agent.

[0016] In some embodiments of the present invention, the modified nano-calcium carbonate is prepared by mixing nano-calcium carbonate with a titanate coupling agent and stirring at 500-800 rpm for 15-20 min at 100-120°C, wherein the amount of titanate coupling agent used during mixing is 2.5%-3.0% of the mass of nano-calcium carbonate.

[0017] In some embodiments of the present invention, the modified nano-calcium carbonate has a particle size of 40-60 nm.

[0018] In some embodiments of the present invention, the processing aid is a compound of a fluoropolymer processing aid and oxidized polyethylene wax in a mass ratio of 1:(1-2).

[0019] In some embodiments of the present invention, the fluoropolymer processing aid is at least one of vinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, and tetrafluoroethylene-hexafluoropropylene copolymer.

[0020] In some embodiments of the present invention, the antioxidant is obtained by compounding antioxidant 1010 and antioxidant 168 in a mass ratio of 1:(1-3).

[0021] In some embodiments of the present invention, the elongation at break of the plum blossom tube is ≥250%, and the wall thickness deviation is ≤±0.20mm.

[0022] A method for preparing a plum blossom tube as described above includes the following steps: mixing the raw materials and then melting and granulating them to obtain granules, then melting and extruding the granules to sizing and shaping them, and finally cutting them after cooling.

[0023] In some embodiments of the present invention, the mixing is carried out in a mixer, the mixing speed is 800-1000 r / min, and the mixing time is 5-8 min.

[0024] In some embodiments of the present invention, the melt granulation is carried out in a twin-screw extruder, and the temperatures of each section of the twin-screw extruder are set sequentially as follows: Zone 1 170-175℃, Zone 2 175-180℃, Zone 3 180-185℃, Zone 4 185-190℃, and the die head temperature 190-195℃.

[0025] In some embodiments of the present invention, during the melt granulation process, the screw speed of the twin-screw extruder is 350-450 r / min, and the melt pressure is controlled at 12-15 MPa.

[0026] In some embodiments of the present invention, the melt extrusion involves adding the granules to a single-screw extruder and using a melt metering pump to achieve steady-flow extrusion.

[0027] In some embodiments of the present invention, during melt extrusion, the temperatures of each section of the single screw extruder are set sequentially as follows: Zone 1 165-175℃, Zone 2 175-185℃, Zone 3 180-190℃, Neck 185-190℃, and Head 185-195℃.

[0028] In some embodiments of the present invention, during melt extrusion, the screw speed of the single-screw extruder is 35-45 r / min.

[0029] In some embodiments of the present invention, the discharge flow rate fluctuation of the melt metering pump is ≤±1%.

[0030] In some embodiments of the present invention, the sizing forming adopts a three-stage vacuum sizing and gradient spray cooling forming, which includes: front stage vacuum degree: -0.03 to -0.04 MPa, cooling water temperature 40 to 50°C; middle stage vacuum degree: -0.05 to -0.06 MPa, cooling water temperature 25 to 30°C; rear stage vacuum degree: -0.04 to -0.05 MPa, cooling water temperature 15 to 20°C.

[0031] In some embodiments of the present invention, during the melt extrusion, a servo synchronous traction machine is used for traction, and the linkage error between the traction speed and the extrusion speed is ≤ ±0.5%.

[0032] The beneficial effects of this invention are: (1) The innovative formulation of the plum blossom pipe of this invention is the first of its kind, which is a quaternary synergistic system of high-density polyethylene, metallocene-catalyzed linear low-density polyethylene, ethylene-octene copolymer elastomer, and modified nano-calcium carbonate. Combined with special processing aids and antioxidants, it breaks the industry's technical prejudice that "reinforcement reduces toughness" and achieves simultaneous improvement in melt strength, rigidity, and elongation at break. Among them, high-density polyethylene, as the matrix resin, provides the basic rigidity, mechanical strength and processing foundation of the pipe. Metallocene-catalyzed linear low-density polyethylene is used to improve the rheological uniformity of the melt and enhance the longitudinal ductility. In addition to low-temperature toughness, stable extrusion state, and reduced internal stress, ethylene-octene copolymer elastomer synergistically toughens the pipe without reducing its rigidity, significantly improving elongation at break. Modified nano-calcium carbonate has excellent compatibility with the polyolefin matrix, which can significantly improve melt support strength and dimensional stability without causing a significant decrease in elongation at break. Processing aids can effectively reduce extrusion torque and die buildup, suppress melt pulsation, and improve wall thickness uniformity. Antioxidants can effectively inhibit thermo-oxidative aging and molecular chain degradation during high-temperature extrusion, ensuring the long-term performance of the pipe. (2) The preparation method of the plum blossom tube of the present invention adopts five-in-one precise control of gradient temperature control, metering pump flow stabilization, three-stage vacuum, gradient cooling and synchronous traction, which further ensures the appearance of the plum blossom tube during production extrusion and avoids the occurrence of unqualified products. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments.

[0034] Example 1: A seven-hole plum blossom tube comprises the following raw materials in parts by weight: high-density polyethylene: 100 parts; metallocene-catalyzed linear low-density polyethylene: 15 parts; ethylene-octene copolymer elastomer: 6 parts; modified nano-calcium carbonate: 5 parts; processing aids: 0.5 parts; antioxidants: 0.4 parts. The high-density polyethylene is PE100 grade high-density polyethylene. Under test conditions of 190℃ / 2.16kg, the melt flow rate of the high-density polyethylene is 0.40g / 10min, the density of the high-density polyethylene is 0.952g / cm³, the melt strength of the metallocene-catalyzed linear low-density polyethylene is 12cN, and the octene monomer content of the ethylene-octene copolymer elastomer is 28%. The melt strength of the copolymer elastomer is 15 cN. The modified nano-calcium carbonate is nano-calcium carbonate with surface modification by a titanate coupling agent. The modified nano-calcium carbonate is prepared by mixing nano-calcium carbonate with a titanate coupling agent and stirring at 110°C and 600 rpm for 16 min. The amount of titanate coupling agent used during mixing is 2.8% of the mass of nano-calcium carbonate. The particle size of the modified nano-calcium carbonate is 50 nm. The processing aid is a fluoropolymer processing aid and oxidized polyethylene wax compounded at a mass ratio of 1:1.5. The fluoropolymer processing aid is vinylidene fluoride-hexafluoropropylene copolymer. The antioxidant is antioxidant 1010 and antioxidant 168 compounded at a mass ratio of 1:2.

[0035] A method for preparing a seven-hole plum blossom tube as described above includes the following steps: (1) Raw material mixing: Add each component raw material to a high-speed mixer according to the weight ratio, stir and mix for 6 minutes at a mixing speed of 900 r / min to obtain a uniform mixture; (2) Melt granulation: The mixture is added to a parallel twin-screw extruder for melt blending and granulation. The temperature of each section of the twin screw is set as follows: Zone 1 175℃, Zone 2 180℃, Zone 3 185℃, Zone 4 190℃, and the die head temperature is 195℃. The screw speed is 400r / min, the melt pressure is controlled at 13MPa, and the special modified granules are obtained by water cooling and pelletizing. (3) Gradient temperature control extrusion: The modified granules are added to a single screw extruder and equipped with a high-precision melt metering pump to achieve steady flow extrusion; the single screw extrusion temperature is set as follows: Zone 1 170℃, Zone 2 180℃, Zone 3 185℃, Neck 190℃, and Head 190℃; the screw speed is controlled at 40r / min, and the discharge flow rate fluctuation of the melt metering pump is ≤±1%; (4) Vacuum sizing and gradient cooling: Three-stage vacuum sizing and gradient spray cooling are adopted for sizing. The vacuum degree of the first stage is -0.04MPa and the cooling water temperature is 45℃; the vacuum degree of the middle stage is -0.05MPa and the cooling water temperature is 28℃; the vacuum degree of the last stage is -0.04MPa and the cooling water temperature is 18℃. (5) Synchronous traction and cutting: A servo synchronous traction machine is used for traction. The linkage error between traction speed and extrusion speed is ≤ ±0.5%. After the pipe is completely cooled, it is cut to a fixed length to obtain the finished seven-hole plum blossom pipe.

[0036] Example 2: A seven-hole plum blossom tube comprises the following raw materials in parts by weight: high-density polyethylene: 120 parts; metallocene-catalyzed linear low-density polyethylene: 12 parts; ethylene-octene copolymer elastomer: 5 parts; modified nano-calcium carbonate: 4 parts; processing aids: 0.4 parts; antioxidants: 0.3 parts. The high-density polyethylene is PE100 grade high-density polyethylene. Under test conditions of 190℃ / 2.16kg, the melt flow rate of the high-density polyethylene is 0.35g / 10min, the density of the high-density polyethylene is 0.950g / cm³, the melt strength of the metallocene-catalyzed linear low-density polyethylene is 10cN, and the octene monomer content of the ethylene-octene copolymer elastomer is 25%. The melt strength of the olefin copolymer elastomer is 12 cN. The modified nano-calcium carbonate is nano-calcium carbonate with surface modification by a titanate coupling agent. The modified nano-calcium carbonate is prepared by mixing nano-calcium carbonate with a titanate coupling agent and stirring at 500 rpm for 20 min at 120℃. The amount of titanate coupling agent used during mixing is 2.5% of the mass of nano-calcium carbonate. The particle size of the modified nano-calcium carbonate is 40 nm. The processing aid is a fluoropolymer processing aid and oxidized polyethylene wax compounded at a mass ratio of 1:1. The fluoropolymer processing aid is vinylidene fluoride-hexafluoropropylene copolymer. The antioxidant is antioxidant 1010 and antioxidant 168 compounded at a mass ratio of 1:1.

[0037] A method for preparing a seven-hole plum blossom tube as described above is exactly the same as in Example 1.

[0038] Example 3: A seven-hole plum blossom tube comprises the following raw materials in parts by weight: high-density polyethylene: 80 parts; metallocene-catalyzed linear low-density polyethylene: 18 parts; ethylene-octene copolymer elastomer: 8 parts; modified nano-calcium carbonate: 6 parts; processing aids: 0.6 parts; antioxidants: 0.5 parts. The high-density polyethylene is PE100 grade high-density polyethylene. Under test conditions of 190℃ / 2.16kg, the melt flow rate of the high-density polyethylene is 0.45g / 10min, the density of the high-density polyethylene is 0.955g / cm³, the melt strength of the metallocene-catalyzed linear low-density polyethylene is 11cN, and the octene monomer content of the ethylene-octene copolymer elastomer is 30%. The melt strength of the copolymer elastomer is 13 cN. The modified nano-calcium carbonate is nano-calcium carbonate with surface modification by a titanate coupling agent. The modified nano-calcium carbonate is prepared by mixing nano-calcium carbonate with a titanate coupling agent and stirring at 800 rpm for 15 min at 100 °C. The amount of titanate coupling agent used during mixing is 3.0% of the mass of nano-calcium carbonate. The particle size of the modified nano-calcium carbonate is 60 nm. The processing aid is a fluoropolymer processing aid and oxidized polyethylene wax compounded at a mass ratio of 1:2. The fluoropolymer processing aid is vinylidene fluoride-hexafluoropropylene copolymer. The antioxidant is antioxidant 1010 and antioxidant 168 compounded at a mass ratio of 1:3.

[0039] A method for preparing a seven-hole plum blossom tube as described above is exactly the same as in Example 1.

[0040] Comparative Example 1: A seven-hole plum blossom tube comprises the following raw materials in parts by weight: 100 parts of pure PE100 grade high-density polyethylene, 0.3 parts of antioxidant, 0.5 parts of oxidized polyethylene wax, wherein the antioxidant is obtained by compounding antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0041] A method for preparing a seven-hole plum blossom tube as described above includes the following steps: mixing the raw materials and then melting and granulating them using a twin-screw extruder. The temperatures of each section of the twin-screw extruder are set sequentially as follows: Zone 1 175℃, Zone 2 180℃, Zone 3 185℃, Zone 4 190℃, and the die head temperature 195℃. The granules are then added to a single-screw extruder, and the extrusion temperatures of the single-screw extruder are set as follows: Zone 1 190℃, Zone 2 190℃, Zone 3 190℃, the neck 190℃, and the die head 190℃. The product is then shaped by single-stage vacuum sizing (vacuum degree -0.05MPa), room temperature cooling, and then cut by ordinary traction to obtain the finished product.

[0042] Comparative Example 2: A seven-hole plum blossom tube differs from Example 1 in that the raw material used is unmodified ordinary heavy calcium carbonate modified with nano calcium carbonate, while the rest of the formula and proportions are exactly the same as in Example 1.

[0043] A method for preparing a seven-hole plum blossom tube as described above is exactly the same as in Example 1.

[0044] Test example: The plum blossom tubes of Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests according to relevant industry standards. The test results are shown in Table 1 below.

[0045] Table 1. Performance Test Results

[0046] As shown in Table 1, the excellent elongation at break and the strong and tough balance system of the plum blossom tube of the present invention ensure that the elongation at break is stable at ≥250%, and can reach up to 423%, far exceeding the lower limit requirement of the standard. The wall thickness deviation is ≤±0.20mm, which is far better than the standard requirement of ≤±0.5mm. It does not break under 10 / 10 drop hammer impact, the longitudinal shrinkage rate is ≤1.9%, the stiffness is ≥15kN / m², and the service life is extended to more than 50 years. It has extremely strong industrial applicability, uses universal raw materials, is compatible with existing production lines, does not require modification of molds, has controllable costs, and can be stably replicated on a large scale.

[0047] Comparative Example 1, a pure HDPE system, suffers from severe deformation, elongation below the standard lower limit, and excessive wall thickness. Comparing Example 1 and Comparative Example 2, it can be seen that when unmodified calcium carbonate is used, the elongation of the resulting plum blossom pipe is substandard and the wall thickness deviation exceeds the standard, both failing to meet production and usage requirements.

[0048] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A plum blossom tube, characterized in that: The raw materials include: high-density polyethylene, metallocene-catalyzed linear low-density polyethylene, ethylene-octene copolymer elastomer, modified nano-calcium carbonate, processing aids, and antioxidants.

2. The plum blossom tube according to claim 1, characterized in that: The raw materials include the following parts by weight: high-density polyethylene: 80-120 parts; metallocene-catalyzed linear low-density polyethylene: 12-18 parts; ethylene-octene copolymer elastomer: 5-8 parts; modified nano calcium carbonate: 4-6 parts; processing aids: 0.4-0.6 parts; antioxidants: 0.3-0.5 parts.

3. The plum blossom tube according to claim 1, characterized in that: The melt flow rate of the high-density polyethylene under test conditions of 190℃ / 2.16kg is 0.35-0.45g / 10min.

4. A plum blossom tube according to claim 1, characterized in that: The melt strength of the metallocene-catalyzed linear low-density polyethylene is ≥10 cN.

5. A plum blossom tube according to claim 1, characterized in that: The octene monomer content of the ethylene-octene copolymer elastomer is 25%-30%, and the melt strength of the ethylene-octene copolymer elastomer is ≥12cN.

6. A plum blossom tube according to claim 1, characterized in that: The modified nano-calcium carbonate is nano-calcium carbonate with a surface modified by a titanate coupling agent.

7. A method for preparing a plum blossom tube as described in any one of claims 1 to 6, characterized in that: Includes the following steps: The raw materials are mixed, melted and granulated to obtain granules, which are then melted, extruded and sized, cooled and cut to obtain the final product.

8. The method for preparing a plum blossom tube according to claim 7, characterized in that: The melt granulation is carried out in a twin-screw extruder, and the temperatures of each section of the twin-screw extruder are set sequentially as follows: Zone 1 170-175℃, Zone 2 175-180℃, Zone 3 180-185℃, Zone 4 185-190℃, and the die head temperature 190-195℃.

9. The method for preparing a plum blossom tube according to claim 7, characterized in that: The melt extrusion involves adding the granules to a single-screw extruder and using a melt metering pump to achieve steady-flow extrusion.

10. The method for preparing a plum blossom tube according to claim 7, characterized in that: The sizing forming process employs a three-stage vacuum sizing and gradient spray cooling forming method, which includes: a front stage with a vacuum degree of -0.03 to -0.04 MPa and a cooling water temperature of 40 to 50°C; a middle stage with a vacuum degree of -0.05 to -0.06 MPa and a cooling water temperature of 25 to 30°C; and a rear stage with a vacuum degree of -0.04 to -0.05 MPa and a cooling water temperature of 15 to 20°C.

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