Easy hot melt welded PE water supply pipe and preparation method thereof

Abstract

The application discloses an easy hot-melt welding PE water supply pipe and a preparation method thereof. The raw materials of the PE water supply pipe comprise the following components in parts by weight: 85-90 parts of high-density polyethylene resin, 3.0-5.0 parts of linear low-density polyethylene grafting material, 3.0-4.0 parts of carbon black masterbatch, 2.0-3.0 parts of leveling master powder, 1.0-1.5 parts of lubricant, 0.2-0.5 parts of organic silicon modified polyacrylate and 0.15-0.25 parts of antioxidant. The leveling master powder is obtained by coating high-sphericity inorganic powder with octaphenylcyclotetrasiloxane, can significantly improve the leveling property of the high-density polyethylene high-temperature hot melt, and when the pipe material is hot-melt welded, the hot melt edge can be automatically leveled, the bubble defects are significantly reduced, the hot melt material at the joint is fully fused, and the welding strength is increased. Without using low-melting-point high-flowing material, the problem of poor flowability and easy air entrapment during welding of the third-generation PE100-grade pipe material is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of polymer pipe technology, and specifically relates to a PE water supply pipe that is easy to heat melt weld and its preparation method. Background Technology

[0002] Polyethylene (PE) pipes possess excellent corrosion resistance, low-temperature flexibility, and durability, leading to their widespread use in municipal water supply networks. In particular, third-generation PE100 grade pipes have enhanced strength and crack resistance. Furthermore, PE pipes offer reliable connections, convenient construction, safety, and hygiene, resulting in their increasing use in underground water supply projects with a service life exceeding 50 years. However, due to complex environmental changes such as foundation settlement and water pressure overload, leakage is inevitable in PE pipes. Feedback from engineering projects indicates that leakage primarily occurs at the weld joints of the PE pipes. Ultrasonic detection reveals that the presence of numerous air bubbles or impurities at the weld seams is the primary cause of leakage.

[0003] Currently, the main method for connecting large-diameter polyethylene pipes is thermofusion butt welding. Thermofusion butt welding involves heating the end faces of two polyethylene pipes to a molten state, then quickly joining them together under pressure to fuse them completely into a single, continuous pipeline. The strength of the thermofusion joint is a crucial indicator of the quality of the connection. Due to the material's thermal deformation and the thermofusion welding process, the mechanical properties of the thermofusion butt weld are relatively weak. During thermofusion welding, if the temperature is too low, the polyethylene material cannot fully melt, affecting the bonding; if the temperature is too high, it can lead to localized degradation and hardening of the polyethylene, edge curling, foaming, and gas inclusion, resulting in reduced weld strength.

[0004] Currently, to increase the strength of welded joints in polyethylene pipes, welding is typically performed by increasing the degree of fusion and welding pressure to ensure full fusion at the joint. However, increasing welding pressure can cause excessive flanging at the hot melt joint, resulting in an uneven weld surface. Increasing the degree of fusion can also introduce gas, creating new stress defects. These bubble stress defects cause slow crack propagation, especially in buried pipes with a diameter exceeding 200mm, where bubble stress defects can jeopardize the service life of the pipeline.

[0005] Current technologies, in developing the third-generation PE100 grade pipes, primarily utilize low melt index high-density polyethylene (HDPE). HDPE has high viscosity and poor fluidity after melting, leading to poor uniformity during hot-melt welding and thus affecting weld strength. Research has mainly focused on improving strength and toughness. For example, Chinese invention patent publication CN116162301B discloses a reinforced polyethylene pipe and its production method, using mica powder and rod-shaped zinc oxide as reinforcing fillers, combined with polyethylene octene elastomer to improve the strength and low-temperature impact resistance of the high-density polyethylene pipe. Chinese invention patent publication CN115572428B discloses a water supply pipe and its preparation method, using a composite of EPDM rubber, paraffin oil, titanium powder, and calcium carbonate as reinforcing materials to strengthen high-density polyethylene, thereby improving the tensile strength of the water supply pipe.

[0006] There is currently limited research on how to improve the weld strength of polyethylene pipes. Based on existing publicly available technologies, such as Chinese Invention Patent Publication No. CN114316442B which discloses a method to make polypropylene materials easier to hot-plate welded and achieve high weld strength through hyperbranched polyacrylate oligomers, and Chinese Invention Patent Publication No. CN112094472B which discloses a high-weld-strength polypropylene composition that improves melt strength by adding low-density polyethylene and ethylene-propylene random copolymer, thus having a synergistic effect on weld strength.

[0007] Based on the above, increasing welding strength mainly involves using polymers with low melting points and high heat melt flowability. However, this inevitably leads to a decrease in melt viscosity, resulting in reduced heat resistance and overall strength of the PE pipe, which is extremely detrimental to the development of third-generation PE100 grade pipes. Summary of the Invention

[0008] To address the problems encountered in the development of third-generation PE100 grade pipes, such as poor material flow during hot-melt welding and the tendency for gas to be trapped in the weld seams, leading to stress defects and reduced weld strength, this invention provides a PE water supply pipe that is easily hot-melt welded and its preparation method. The technology employed increases the flowability of the hot-melt material during PE pipe butt welding, promptly eliminating air bubbles trapped in the weld seams, removing weld defects, forming a seamless weld, and increasing the strength of the hot-melt weld.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] One object of the present invention is to provide a PE water supply pipe that is easily heat-fused and welded. The main raw materials of the PE water supply pipe, by weight, include: 85-90 parts of high-density polyethylene resin, 3.0-5.0 parts of linear low-density polyethylene graft, 3.0-4.0 parts of carbon black masterbatch, 2.0-3.0 parts of leveling masterbatch, 1.0-1.5 parts of lubricant, 0.2-0.5 parts of organosilicon-modified polyacrylate, and 0.15-0.25 parts of antioxidant.

[0011] The linear low-density polyethylene graft is a modified product grafted with any monomer of maleic anhydride or itaconic anhydride.

[0012] The leveling masterbatch is obtained by coating high-sphericity inorganic powder with octaphenylcyclotetrasiloxane.

[0013] Preferably, the melt flow rate (MFR) of the high-density polyethylene is 0.1-0.5 g / 10 min (5 kg, 190 °C). Particularly preferably, the high-density polyethylene is selected from either HDPE7600M (Yanshan Petrochemical) or BorSafe HE3490-LS (Borealis), both of which have a bimodal molecular weight distribution.

[0014] Preferably, the linear low-density polyethylene graft is a modified product obtained by grafting any monomer of maleic anhydride or itaconic anhydride onto linear low-density polyethylene at a mass ratio of (1-2):100 under the influence of an initiator. The linear low-density polyethylene graft has good weldability, improving the hot-melt weldability of high-density polyethylene; it also has compatibility and dispersibility, promoting the uniform dispersion of carbon black masterbatch, leveling masterbatch, and silicone-modified polyacrylate in the high-density polyethylene system.

[0015] Preferably, the carbon black content of the carbon black masterbatch is 30-50%. Appropriate introduction of carbon black maintains the black and glossy appearance of the PE water supply pipe and provides good resistance to UV aging. Excessive addition of carbon black can lead to difficulties in pipe flowability during extrusion molding.

[0016] Preferably, the leveling masterbatch is obtained by coating the high-sphericity inorganic powder with octaphenylcyclotetrasiloxane at a mass ratio of 1:(8-10) under heating conditions.

[0017] More preferably, the high-sphericity inorganic powder is selected from at least one of spherical alumina, silica powder, and glass microspheres with a sphericity >85% and a particle size <10µm. The high-sphericity inorganic powder possesses good flowability, while octaphenylcyclotetrasiloxane exhibits excellent high-temperature resistance and defoaming properties that promote the leveling of the hot melt. By agglomerating on the surface of the high-sphericity inorganic powder during hot melting, it serves as a leveling master powder, resulting in better dispersibility and flowability. During high-temperature hot-melt butt welding of high-density polyethylene resin pipes, the leveling master powder can significantly reduce the surface tension of the hot melt, promote its leveling, and prevent air bubbles from being trapped, thereby increasing the integrity and strength of the hot-melt weld. The leveling master powder uses high-sphericity inorganic powder as the main base material, reducing the use of octaphenylcyclotetrasiloxane and resulting in superior high-temperature stability.

[0018] Preferably, the silicone-modified polyacrylate is a polyacrylate modified with epoxy silane. It exhibits good high-temperature resistance and promotes melt flow leveling during the high-temperature hot-melt state of high-density polyethylene.

[0019] Preferably, the lubricant is a stearate lubricant; specifically, at least one of zinc stearate and calcium stearate.

[0020] Preferably, the antioxidant is a hindered phenolic antioxidant as the main antioxidant and a phosphite antioxidant as an auxiliary antioxidant, used in a synergistic ratio of 2:1 by mass to increase the oxidation induction period (OIT) of the material.

[0021] Preferably, the hindered phenolic antioxidant is one of antioxidant 1010 or antioxidant 1330. The hindered phenolic antioxidant can significantly inhibit the formation of polyolefin carbonyl groups, delay aging, and thus increase the service life of the pipe. The phosphite antioxidant is antioxidant 168.

[0022] During butt welding of PE pipes, air trapped in the hot-melt ferrule is difficult to expel, easily resulting in residual air bubbles in the weld and affecting weld strength. By synergistically using leveling masterbatch and silicone-modified polyacrylate in high-density polyethylene (HDPE), which exhibits good high-temperature resistance, the heat melt undergoes rheological deregulation and viscosity reduction during hot-melt welding, lowering surface tension and rapidly eliminating trapped air bubbles. This promotes melt leveling and prevents the formation of air bubbles and pinholes. Furthermore, by using linear low-density polyethylene (LDPE) grafts, the excellent hot-melt weldability of LDPE is utilized to improve the hot-melt welding effect of HDPE and promote the dispersion of carbon black masterbatch, leveling masterbatch, and silicone-modified polyacrylate within the HDPE system.

[0023] Another object of the present invention is to provide a method for preparing the easily heat-fused PE water supply pipe, characterized by comprising the following steps:

[0024] S1. Preparation of linear low-density polyethylene graft: Linear low-density polyethylene, monomer, and initiator are mixed evenly in a high-speed mixer, and then fed into a co-rotating twin-screw extruder for hot-melt graft modification to obtain low-density polyethylene graft; the monomer is either maleic anhydride or itaconic anhydride; the initiator is either dicumyl peroxide or benzoyl peroxide.

[0025] S2. Preparation of leveling master powder: Octaphenylcyclotetrasiloxane and high sphericity inorganic powder are added to a high-speed disperser, and the heating temperature is gradually increased from 100℃ to 200℃. Under high-speed dispersion conditions, octaphenylcyclotetrasiloxane gradually melts and coats the high sphericity inorganic powder to obtain leveling master powder.

[0026] S3. Preparation of PE pipe material: According to weight, 2.0-3.0 parts of leveling masterbatch, 1.0-1.5 parts of lubricant, 0.2-0.5 parts of silicone-modified polyacrylate, and 0.15-0.25 parts of antioxidant are premixed in a kneader; then the premix is ​​added to a high-speed mixer along with 85-90 parts of high-density polyethylene resin, 3.0-5.0 parts of linear low-density polyethylene graft, and 3.0-4.0 parts of carbon black masterbatch, and mixed evenly at 80℃; the mixture is then fed into a single-screw granulator for hot melt extrusion granulation to obtain PE pipe material;

[0027] S4. Pipe preparation: The PE pipe material is transported to the pipe production line, first dried, and then hot-melted extruded by the pipe extruder. The hot-melted material is divided by a spiral flow and formed into a tubular blank in the die forming section. It is then extruded by the die, shaped by the negative pressure sizing box, and further sprayed for cooling, laser marking, cutting and stacking to obtain a PE water supply pipe that is easy to hot melt weld.

[0028] Preferably, in step S1, the hot melt extrusion temperature of the co-rotating twin-screw extruder is controlled at 160-180℃.

[0029] Preferably, the stirring speed of the high-speed disperser in step S2 is greater than 1000 rpm. In the high-speed dispersion state, octaphenylcyclotetrasiloxane gradually melts and fully coats the high-sphericity inorganic powder.

[0030] Preferably, in step S3, the hot melt extrusion temperature of the single screw granulator is controlled at 200-220℃.

[0031] Preferably, the drying process parameters in step S4 are drying at 80°C for 1-2 hours.

[0032] Preferably, the temperature and pressure of the pipe extruder in step S4 are set as follows: feeding section 80-100℃; plasticizing section 190-200℃; homogenizing section 210-230℃; die 210-220℃; extrusion pressure 15-30MPa.

[0033] The advantages and beneficial effects of this invention are as follows:

[0034] 1) This invention uses leveling masterbatch and silicone-modified polyacrylate to synergistically improve the leveling properties of high-density polyethylene high-temperature hot melt. When the pipe is hot melt welded, the hot melt edge automatically levels, making it less likely to introduce gas, significantly reducing bubble defects, and the hot melt material at the joint is fully fused, increasing the welding strength.

[0035] 2) In the PE pipe material of the present invention, the use of linear low-density polyethylene graft material improves the hot-melt butt welding effect of high-density polyethylene by taking advantage of its good hot-melt weldability, and promotes the dispersion of carbon black masterbatch, leveling masterbatch, and organosilicon modified polyacrylate in the high-density polyethylene system.

[0036] 3) The material of the present invention greatly optimizes the welding effect of hot melt welding of pipes, eliminating the need to use low melting point and high flow materials, and effectively solving the problems of poor flowability and easy air entrapment during welding of third-generation PE100 grade pipes. Attached Figure Description

[0037] Figure 1 Example 1: A diagram showing the rolled edge of a PE water supply pipe after hot-melt welding.

[0038] Figure 2 Comparative Example 1: The rolled edge of the PE water supply pipe after hot-melt welding. Detailed Implementation

[0039] The preferred embodiments of the present invention are described in detail below to make the advantages of the present invention more readily understood by those skilled in the art. Importantly, the influence of the raw material formulations of each embodiment on hot-melt welding is compared and analyzed. Unless otherwise specified, the equipment and process parameters used are conventional choices in the art. Some raw material parameters used in the embodiments are as follows:

[0040] High-density polyethylene: BorSafe HE3490-LS, MFR 0.3g / 10min (5kg, 190℃), Borealis.

[0041] Linear low-density polyethylene: DFDA-7047 NT7, MFR 1.0g / 10min (2.16kg, 190℃), Dow Chemical.

[0042] Octaphenylcyclotetrasiloxane: CAS No. 546-56-5, Jiangxi Ford Chemical New Materials Co., Ltd.

[0043] Carbon black masterbatch: PE2084, carbon black content 45%, Guangdong Jiucai New Materials Co., Ltd.

[0044] Example 1

[0045] S1. Preparation of linear low-density polyethylene graft: Linear low-density polyethylene, maleic anhydride, and initiator dicumyl peroxide are mixed evenly in a high-speed mixer at a mass ratio of 100:2:0.2, and then fed into a ⌀65 type co-rotating twin-screw extruder for hot melt extrusion. The temperature control of each zone is set as follows: Zone 1 160℃; Zone 2 170℃; Zone 3 175℃; Zone 4 180℃; Zone 5 180℃; Zone 6 180℃; Zone 7 175℃; Zone 8 170℃; Zone 9 160℃; Zone 10 160℃; screw speed 150 rpm; water-cooled strip drawing and pelletizing to obtain low-density polyethylene graft;

[0046] S2. Preparation of leveling master powder: Octaphenylcyclotetrasiloxane and glass microspheres (sphericity >90%, particle size <10µm) are added to a high-speed disperser at a mass ratio of 1:10. The materials are completely dispersed by stirring at a high speed of 1200rpm. The heating temperature is gradually increased from 100℃ to 200℃. In the dispersed state, the octaphenylcyclotetrasiloxane is gradually melted to fully coat the glass microspheres. After cooling and grinding, leveling master powder is obtained.

[0047] S3. Preparation of PE pipe material: According to the weight, 2.5 parts of leveling masterbatch, 1.0 part of zinc stearate lubricant, 0.2 parts of epoxy silane modified polyacrylate, 0.1 parts of antioxidant 1010, and 0.05 parts of antioxidant 168 are premixed in a kneader; then the premix is ​​added to a high-speed mixer along with 88 parts of high-density polyethylene resin, 5.0 parts of linear low-density polyethylene graft, and 3.0 parts of carbon black masterbatch, and mixed evenly at 80°C; the mixture is then fed into a single-screw granulator for hot melt extrusion granulation, with the hot melt extrusion temperature of the single-screw granulator controlled at 210°C to obtain PE pipe material;

[0048] S4. The PE pipe material is transported to the pipe production line and dried at 80℃ for 1 hour in the drying silo. It is then transported to the pipe extruder, and the extrusion temperature and pressure are set as follows: feeding section 100℃; plasticizing section 190℃; homogenizing section 210℃; die 220℃; extrusion pressure 20MPa. After hot melt extrusion by the pipe extruder, the hot melt material is spirally diverted to form a tubular preform in the die forming section, and then extruded by the die. It is then shaped by the negative pressure sizing box, further sprayed and cooled, laser-marked, cut and stacked to obtain a PE water supply pipe that is easy to hot melt weld.

[0049] Example 2

[0050] S1. Preparation of linear low-density polyethylene graft: Linear low-density polyethylene, itaconic anhydride, and initiator benzoyl peroxide are mixed evenly in a high-speed mixer at a mass ratio of 100:2:0.3, and then fed into a ⌀65 type co-rotating twin-screw extruder for hot melt extrusion. The temperature control of each zone is set as follows: Zone 1 160℃; Zone 2 170℃; Zone 3 175℃; Zone 4 180℃; Zone 5 180℃; Zone 6 180℃; Zone 7 175℃; Zone 8 170℃; Zone 9 160℃; Zone 10 160℃; Screw speed 200 rpm; water-cooled strip drawing and pelletizing to obtain low-density polyethylene graft;

[0051] S2. Preparation of leveling master powder: Octaphenylcyclotetrasiloxane and spherical alumina (sphericity >85%, particle size <10µm) are added to a high-speed disperser at a mass ratio of 1:9. The materials are completely dispersed by high-speed stirring at 1200rpm. The heating temperature is gradually increased from 100℃ to 200℃. In the dispersed state, octaphenylcyclotetrasiloxane is gradually melted to fully coat the spherical alumina. After cooling and grinding, leveling master powder is obtained.

[0052] S3. Preparation of PE pipe material: According to the weight, 3.0 parts of leveling masterbatch, 1.0 part of calcium stearate lubricant, 0.3 parts of epoxy silane modified polyacrylate, 0.15 parts of antioxidant 1330, and 0.1 parts of antioxidant 168 are premixed in a kneader; then the premix is ​​added to a high-speed mixer along with 90 parts of high-density polyethylene resin, 4.0 parts of linear low-density polyethylene graft, and 4.0 parts of carbon black masterbatch, and mixed evenly at 80°C; the mixture is then fed into a single-screw granulator for hot melt extrusion granulation, with the hot melt extrusion temperature of the single-screw granulator controlled at 220°C to obtain PE pipe material;

[0053] S4. The PE pipe material is transported to the pipe production line and dried at 80℃ for 2 hours in the drying silo. It is then transported to the pipe extruder, and the extrusion temperature and pressure are set as follows: feeding section 80℃; plasticizing section 190℃; homogenizing section 210℃; die 220℃; extrusion pressure 25MPa. After hot melt extrusion by the pipe extruder, the hot melt material is spirally diverted to form a tubular preform in the die forming section, and then extruded by the die. It is then shaped by the negative pressure sizing box, further sprayed and cooled, laser-marked, cut and stacked to obtain a PE water supply pipe that is easy to hot melt weld.

[0054] Example 3

[0055] S1. Preparation of linear low-density polyethylene graft: Linear low-density polyethylene, maleic anhydride, and initiator dicumyl peroxide are mixed evenly in a high-speed mixer at a mass ratio of 100:1.5:0.3, and then fed into a ⌀65 type co-rotating twin-screw extruder for hot melt extrusion. The temperature control of each zone is set as follows: Zone 1 160℃; Zone 2 170℃; Zone 3 175℃; Zone 4 180℃; Zone 5 180℃; Zone 6 180℃; Zone 7 175℃; Zone 8 170℃; Zone 9 160℃; Zone 10 160℃; Screw speed 200 rpm; water-cooled strip drawing and pelletizing to obtain low-density polyethylene graft.

[0056] S2. Preparation of leveling master powder: Octaphenylcyclotetrasiloxane and silica powder (sphericity >85%, particle size <10µm) are added to a high-speed disperser at a mass ratio of 1:8. The material is completely dispersed at a high speed of 1200rpm. The heating temperature is gradually increased from 100℃ to 200℃. In the dispersed state, octaphenylcyclotetrasiloxane is gradually melted to fully coat the silica powder. After cooling and grinding, leveling master powder is obtained.

[0057] S3. Preparation of PE pipe material: According to the weight, 3.0 parts of leveling masterbatch, 1.2 parts of zinc stearate lubricant, 0.5 parts of epoxy silane modified polyacrylate, 0.15 parts of antioxidant 1010, and 0.05 parts of antioxidant 168 are premixed in a kneader; then the premix is ​​added to a high-speed mixer with 90 parts of high-density polyethylene resin, 5.0 parts of linear low-density polyethylene graft material, and 4.0 parts of carbon black masterbatch, and mixed evenly at 80℃; the mixture is then fed into a single-screw granulator for hot melt extrusion granulation, and the hot melt extrusion temperature of the single-screw granulator is controlled at 220℃ to obtain PE pipe material;

[0058] S4. The PE pipe material is transported to the pipe production line and dried at 80℃ for 1 hour in the drying silo. It is then transported to the pipe extruder, and the extrusion temperature and pressure are set as follows: feeding section 100℃; plasticizing section 200℃; homogenizing section 230℃; die 210℃; extrusion pressure 20MPa. After hot melt extrusion by the pipe extruder, the hot melt material is spirally diverted to form a tubular preform in the die forming section, and then extruded by the die. It is then shaped by the negative pressure sizing box, further sprayed and cooled, laser-marked, cut and stacked to obtain a PE water supply pipe that is easy to heat melt weld.

[0059] Comparative Example 1

[0060] Based on the scheme of Example 1, without adding leveling masterbatch and epoxy silane modified polyacrylate, an equal amount of high-density polyethylene was used instead.

[0061] Comparative Example 2

[0062] Based on the scheme of Example 1, without adding leveling masterbatch, an equal amount of high-density polyethylene was used instead.

[0063] Comparative Example 3

[0064] Based on the scheme of Example 1, without adding epoxy silane modified polyacrylate, an equal amount of high-density polyethylene was used instead.

[0065] Comparative Example 4

[0066] Based on the scheme of Example 1, glass microspheres were directly used to replace the leveling masterbatch.

[0067] Comparative Example 5

[0068] Based on the scheme of Example 1, the leveling masterbatch was directly replaced with octaphenylcyclotetrasiloxane.

[0069] The PE pipes of Examples 1-3 and Comparative Examples 1-5 were subjected to hot-melt butt welding, and the performance of the welded pipes was tested.

[0070] (1) Effect of butt welding of pipes:

[0071] The pipe specifications obtained from each scheme are: outer diameter 200mm, wall thickness 18.2mm. Referring to the relevant provisions of GB / T 19809-2005, the pipes were subjected to hot-melt butt welding. The two ends of the pipes to be welded were preheated on a hot plate at 220℃. When the edge height exceeded 2.5mm, the pressure was reduced to 0.08MPa for 200s of heat absorption. After heat absorption was complete, the heating plate was removed, with the switching time controlled within 8s. Pressure was then applied to the two ends to be welded, with a butt welding pressure of 0.15MPa to ensure tight contact between the two welding surfaces until cooling was complete. 24 hours after hot-melt butt welding, the welded parts of the pipes were inspected for defects, including visual inspection and internal testing, as shown in Table 1.

[0072] Table 1: Pipe Welding Quality

[0073]

[0074] Based on the analysis in Table 1, the PE pipe of the present invention exhibits good leveling during hot-melt welding, with uniform and delicate flanging and no air bubbles; there are no fusion defects or obvious air bubbles inside. Figure 1 This is a picture of the rolled edge of the PE water supply pipe after hot-melt welding in Example 1. The rolled edge is delicate. Figure 2 The image shows the rolled edge of the PE water supply pipe after hot-melt welding, as shown in Comparative Example 1. The rolled edge is rough.

[0075] (2) Tensile strength test of hot-melt butt joint:

[0076] Sampling was performed according to GB / T19810-2005 "Determination of Tensile Strength and Failure Mode of Butt-Melt Joints for Polyethylene (PE) Pipes and Fittings". The samples were stretched at a constant tensile rate of 5 mm / min until complete failure. The tensile strength and failure mode of the butt-melt joints were then tested to determine the welding quality. Simultaneously, the tensile strength and failure mode of the base material from the same batch were tested for comparison. A butt-melt joint with a tensile strength exceeding 80% of the base material's tensile strength was considered a qualified weld; a butt-melt joint with a tensile strength exceeding 90% of the base material's tensile strength was considered an excellent weld. Specific results are shown in Table 2.

[0077] Table 2: Comparison of Strength of Hot-Melt Joint and Base Material

[0078]

[0079] Table 2 compares the strength of the hot-melt joint with that of the base material. The tensile strength of the PE pipe after hot-melt butt welding exceeds 90% of the base material strength. During hot-melt welding, the joint is uniformly leveled, introducing fewer air bubbles, resulting in good adhesion, forming a bonded whole with few defects, and exhibiting ductile fracture. This effectively prevents premature failure at the joint, ensuring the overall safety of the pipeline.

[0080] (3) Static hydraulic resistance test:

[0081] According to the technical requirements of GB / T13663.2-2018 "Polyethylene (PE) Piping Systems for Water Supply - Part 2: Pipes", test parameters were set according to the technical requirements of PE100 grade. Referring to GB / T 6111-2018, the hydrostatic resistance of the pipe material after hot-melt butt welding under a ring stress of 12.0 MPa at 20℃ was tested for comparison. Specific results are shown in Table 3.

[0082] Table 3: Comparison of hydrostatic resistance of hot-melt butt-welded pipes with that of the base material

[0083]

[0084] Table 3 shows the hydrostatic resistance of the hot-melt welded pipe under high circumferential stress. The hydrostatic resistance of the PE pipe after hot-melt welding is essentially the same as that of the base material. It can withstand a circumferential stress of 12.0 MPa at 20℃ for 100 hours without failure, demonstrating complete integration through the hot-melt weld.

[0085] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A PE water supply pipe that is easily heat-fused and welded, characterized in that, The main raw materials of the PE water supply pipe, by weight, include: 85-90 parts of high-density polyethylene resin, 3.0-5.0 parts of linear low-density polyethylene graft, 3.0-4.0 parts of carbon black masterbatch, 2.0-3.0 parts of leveling masterbatch, 1.0-1.5 parts of lubricant, 0.2-0.5 parts of organosilicon-modified polyacrylate, and 0.15-0.25 parts of antioxidant. The linear low-density polyethylene graft is a modified product grafted with any monomer of maleic anhydride or itaconic anhydride. The leveling master powder is obtained by adding octaphenylcyclotetrasiloxane and high sphericity inorganic powder in a mass ratio of 1:(8-10) to a high-speed disperser, and gradually increasing the heating temperature from 100℃ to 200℃. Under high-speed dispersion conditions, octaphenylcyclotetrasiloxane gradually heat-melts and coats the high sphericity inorganic powder. The organosilicon-modified polyacrylate is a polyacrylate modified with epoxy silane.

2. The PE water supply pipe for easy heat fusion welding according to claim 1, characterized in that, The high-density polyethylene used is 5 kg, with a melt flow rate of 0.1-0.5 g / min at 190°C, and a molecular weight distribution with bimodal distribution.

3. The PE water supply pipe for easy heat fusion welding according to claim 1, characterized in that, The linear low-density polyethylene graft is obtained by grafting and modifying linear low-density polyethylene with any monomer of maleic anhydride or itaconic anhydride and an initiator at a mass ratio of 100:(1-2):(0.2-0.3).

4. The PE water supply pipe that is easily heat-fused and welded according to claim 1, characterized in that, The high-sphericity inorganic powder is selected from at least one of spherical alumina, silica powder, and glass microspheres with a sphericity >85% and a particle size <10µm.

5. The PE water supply pipe for easy heat fusion welding according to claim 1, characterized in that, The lubricant used is a stearate-based lubricant.

6. The PE water supply pipe for easy heat fusion welding according to claim 1, characterized in that, The antioxidant is selected as hindered phenolic antioxidant as the main antioxidant and phosphite antioxidant as the auxiliary antioxidant, and they are used synergistically at a mass ratio of 2:

1.

7. The method for preparing the easily heat-fused weldable PE water supply pipe according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Preparation of linear low-density polyethylene graft: Linear low-density polyethylene, monomer, and initiator are mixed evenly in a high-speed mixer, and then fed into a co-rotating twin-screw extruder for hot-melt graft modification to obtain low-density polyethylene graft; the monomer is either maleic anhydride or itaconic anhydride; the initiator is either dicumyl peroxide or benzoyl peroxide. S2. Preparation of leveling master powder: Octaphenylcyclotetrasiloxane and high sphericity inorganic powder are added to a high-speed disperser, and the heating temperature is gradually increased from 100℃ to 200℃. Under high-speed dispersion conditions, octaphenylcyclotetrasiloxane gradually melts and coats the high sphericity inorganic powder to obtain leveling master powder. S3. Preparation of PE pipe material: According to weight, 2.0-3.0 parts of leveling masterbatch, 1.0-1.5 parts of lubricant, 0.2-0.5 parts of silicone-modified polyacrylate, and 0.15-0.25 parts of antioxidant are premixed in a kneader; then the premix is ​​added to a high-speed mixer along with 85-90 parts of high-density polyethylene resin, 3.0-5.0 parts of linear low-density polyethylene graft, and 3.0-4.0 parts of carbon black masterbatch, and mixed evenly at 80℃; the mixture is then fed into a single-screw granulator for hot melt extrusion granulation to obtain PE pipe material; S4. Pipe preparation: The PE pipe material is transported to the pipe production line, first dried, and then hot-melted extruded by the pipe extruder. The hot-melted material is divided by a spiral flow and formed into a tubular blank in the die forming section. It is then extruded by the die, shaped by the negative pressure sizing box, and further sprayed for cooling, laser marking, cutting and stacking to obtain a PE water supply pipe that is easy to hot melt weld.

8. The method for preparing the easily heat-fused weldable PE water supply pipe according to claim 7, characterized in that, The temperature and pressure settings of the pipe extruder in step S4 are as follows: feeding section 80-100℃; plasticizing section 190-200℃; homogenizing section 210-230℃; die 210-220℃; extrusion pressure 15-30MPa.

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