Antistatic composite corrugated pipe and preparation method and application thereof

Abstract

The application provides an antistatic composite corrugated pipe and a preparation method and application thereof, and belongs to the technical field of gas pipelines. The antistatic composite corrugated pipe comprises a spiral welded corrugated steel pipe framework and a functional coating which is combined on the inner and outer surfaces of the spiral welded corrugated steel pipe framework; the functional coating is a three-layer gradient structure, and comprises, from inside to outside, a buffer layer containing a polar polymer modified polyolefin, a flame-retardant layer containing a high-temperature-resistant engineering plastic alloy, and a conductive layer taking an elastomer as a matrix and dispersing a two-phase conductive network containing fibrous conductive fillers and particulate conductive fillers. The three-layer gradient structure design of the functional coating endows the antistatic composite corrugated pipe with multiple excellent performances.

Description

Technical Field

[0001] This application relates to the field of gas pipeline technology, and in particular to an antistatic composite corrugated pipe, its preparation method and application. Background Technology

[0002] Traditional coal mine pipes fall into two main categories. The first category is steel pipes, which have several well-known drawbacks: they are significantly heavier, seven times that of PE pipes, making underground operations difficult; they have poor corrosion resistance, and impacts can easily generate sparks, posing safety hazards; they are also expensive and inconvenient to install and maintain. The second category is fiberglass pipes, which, while having better corrosion resistance than steel pipes, have stringent requirements for joints and are prone to leakage; they also present numerous difficulties during installation and use; and they are expensive.

[0003] In recent years, the country has vigorously promoted the application of plastic pipes. Due to their superior performance and energy-saving characteristics, plastic pipes are rapidly replacing metal and other traditional pipe materials. This has led to the emergence of a third major category of pipe materials for coal mines—plastic pipes. They possess the following excellent characteristics: antistatic and flame-retardant; non-toxic, corrosion-resistant, and high-pressure resistant; lightweight and easy to install, making them an ideal pipe material for "replacing steel with plastic" and achieving resource optimization. However, existing plastic pipes have relatively small diameters, which cannot meet the comprehensive requirements of current coal mines.

[0004] Plastic pipes for coal mines are used in high-risk environments such as coal mines. In addition to possessing the general physical and mechanical properties of plastic pipes, these pipes must also have antistatic properties, self-extinguishing properties, and their combustion products must not be highly toxic. Existing composite pipes attempt to unify various properties through overall blending, but often fall into a performance dilemma: increasing rigidity sacrifices toughness, adding flame retardants deteriorates processability and mechanical properties, and high levels of conductive fillers lead to easy surface wear and failure. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and its purpose is to provide an antistatic composite corrugated pipe, its preparation method and application.

[0006] Specifically, the first aspect of this application provides an antistatic composite corrugated pipe, comprising a spiral welded corrugated steel pipe skeleton and a functional coating composited on the inner and outer surfaces of the spiral welded corrugated steel pipe skeleton; the functional coating is a three-layer gradient structure, consisting of the following layers from the inside out:

[0007] A buffer layer comprising a polar polymer-modified polyolefin;

[0008] Flame-retardant layer, comprising high-temperature resistant engineering plastic alloy;

[0009] The conductive layer has an elastomer as its matrix and disperses a two-phase conductive network containing fibrous conductive fillers and particulate conductive fillers.

[0010] Furthermore, the buffer layer comprises maleic anhydride-grafted polyethylene.

[0011] Furthermore, the buffer layer comprises, by weight parts, the following components: 90-100 parts of maleic anhydride-grafted polyethylene, 0-10 parts of hydrogenated styrene-butadiene-styrene block copolymer (SEBS), 0.1-0.5 parts of antioxidant 1010, and 0.1-0.5 parts of antioxidant 168.

[0012] Furthermore, the flame-retardant layer comprises an alloy of polyphenylene sulfide and polyetherimide, as well as a flame retardant.

[0013] Furthermore, the flame retardant layer comprises the following components in parts by weight: 50-70 parts of polyphenylene sulfide, 30-50 parts of polyetherimide, 10-20 parts of aluminum hypophosphite, 3-5 parts of zinc molybdate, 1-3 parts of nano-silica, and 0.2-0.8 parts of polytetrafluoroethylene (PTFE) ultrafine powder.

[0014] Furthermore, the weight ratio of polyphenylene sulfide to polyetherimide is (50-70):(30-50), and the flame retardant comprises aluminum hypophosphite, zinc molybdate, and nano-silica.

[0015] Furthermore, the fibrous conductive filler in the conductive layer is nickel-plated carbon fiber.

[0016] Furthermore, the granular conductive filler is copper-plated silicon carbide particles.

[0017] Furthermore, based on the total weight of the conductive layer, the content of the fibrous conductive filler is 2-6 wt%, and the content of the particulate conductive filler is 8-15 wt%.

[0018] Furthermore, the conductive layer comprises, by weight, the following components: 100 parts thermoplastic polyurethane, 2-6 parts nickel-plated carbon fiber, 8-15 parts copper-plated silicon carbide particles, 1-2 parts dispersant (polyethylene wax), and 3-5 parts polyurethane adhesion promoter.

[0019] Furthermore, the wall thickness of the spiral welded corrugated steel pipe skeleton is 1.0-1.5 mm, and its outer wall has a hollow spiral reinforcing rib structure formed by cold pressing.

[0020] A second aspect of this invention provides a method for preparing an antistatic composite corrugated pipe, comprising the following steps:

[0021] (a) Provide a spiral welded corrugated steel pipe skeleton and clean and activate its outer surface;

[0022] (b) A buffer layer and a flame-retardant layer are sequentially formed on the spiral welded corrugated steel pipe skeleton by co-extrusion composite method to form a composite base pipe;

[0023] (c) A conductive layer is formed on the outer surface of the composite base tube by a powder sintering process;

[0024] (d) Cool and shape the composite tube after it is coated with the conductive layer and perform post-treatment.

[0025] Further, the cleaning and activation treatment described in step (a) is atmospheric pressure plasma treatment; and / or, the working gas for the plasma treatment is a mixture of argon and oxygen, wherein the volume percentage of oxygen is 3%-10%.

[0026] Further, in step (b), the spiral welded corrugated steel pipe skeleton is preheated, the melt of the buffer layer is extruded using a first extruder, the melt of the flame retardant layer is extruded using a second extruder, and the two melts and the preheated steel pipe skeleton are introduced into a composite die for lamination, wherein the temperature of the composite die is set to 290-320℃, and the lamination pipe is subjected to gradient cooling.

[0027] Further, in step (c), the powder sintering process includes: cleaning and activating the outer surface of the composite base tube, uniformly applying the powder made from the raw material of the conductive layer to the activated outer surface by electrostatic adsorption, and melting and sintering the powder by heating from the inside out to form a dense conductive layer.

[0028] Furthermore, the heating method from the inside out is induction heating, in which the internal steel pipe skeleton is heated by an induction coil, and the heat is conducted to the outer powder, causing it to melt and sinter in a temperature range of 180-190°C.

[0029] Further, in step (d), the cooling and shaping process employs a zoned gradient cooling method, including:

[0030] First, enter the hot air slow cooling zone, where the temperature is controlled at 120-150℃;

[0031] Then enter the spray cooling zone, where the water temperature is controlled at 10-20℃.

[0032] The third aspect of this application provides an application of the aforementioned antistatic composite corrugated pipe in a coal mine gas extraction system.

[0033] The present invention has the following beneficial effects:

[0034] This invention relates to an antistatic composite corrugated pipe with a functional coating design. The buffer layer, made of polar polymer-modified polyolefin, effectively relieves stress, improves the pipe's flexibility and impact resistance, and reduces damage caused by external impacts. The flame-retardant layer, a high-temperature resistant engineering plastic alloy, endows the pipe with excellent flame-retardant properties, effectively preventing the spread of fire when exposed to a source of ignition, reducing the risk of fire. Furthermore, the alloy of polyphenylene sulfide and polyetherimide, along with a specific flame-retardant formulation, ensures both flame retardancy and material strength and toughness. The conductive layer, based on an elastomer matrix and containing a dispersed biphase conductive network, utilizes a conductive network formed by nickel-plated carbon fiber and copper-plated silicon carbide particles. This network not only rapidly conducts static electricity, achieving antistatic functionality, but the elastomer matrix also provides the conductive layer with good flexibility and wear resistance, avoiding the surface wear and failure problems caused by traditional high-filler conductive agents.

[0035] The preparation method first involves cleaning and activating the spiral welded corrugated steel pipe skeleton, which improves the bonding force between the skeleton and the functional coating, ensuring that the functional coating can be firmly bonded to the skeleton surface. Three independent extruders are used to plasticize materials of different layers separately, and then the layers are simultaneously coated and bonded through a composite die. This process ensures the uniformity and tightness of the bonding between each layer. The zoned gradient cooling method, with initial hot air slow cooling followed by rapid spray cooling, helps eliminate internal stress in the pipe, improving the dimensional stability and physical properties of the pipe.

[0036] In coal mine gas extraction systems, the antistatic properties of this antistatic composite corrugated pipe can effectively prevent static electricity buildup from generating sparks and reduce the risk of gas explosions; its flame-retardant properties can ensure the integrity of the pipeline and reduce losses in the event of a fire; its good flexibility and impact resistance enable it to adapt to complex underground geological conditions and installation environments; and its lighter weight facilitates transportation and installation, reducing construction difficulty and costs. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this application clearer, the following description and illustration are provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0038] Obviously, the following description is merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0039] An embodiment of the first aspect of this application provides an antistatic composite corrugated pipe, comprising a spiral welded corrugated steel pipe skeleton and a functional coating composited on the inner and outer surfaces of the spiral welded corrugated steel pipe skeleton; the functional coating is a three-layer gradient structure, consisting of the following layers from the inside out:

[0040] A buffer layer comprising a polar polymer-modified polyolefin;

[0041] Flame-retardant layer, comprising high-temperature resistant engineering plastic alloy;

[0042] The conductive layer has an elastomer as its matrix and disperses a two-phase conductive network containing fibrous conductive fillers and particulate conductive fillers.

[0043] This invention relates to an antistatic composite corrugated pipe with a functional coating design. The buffer layer, made of polar polymer-modified polyolefin, effectively relieves stress, improves the pipe's flexibility and impact resistance, and reduces damage caused by external impacts. The flame-retardant layer, a high-temperature resistant engineering plastic alloy, endows the pipe with excellent flame-retardant properties, effectively preventing the spread of fire when exposed to a source of ignition, reducing the risk of fire. Furthermore, the alloy of polyphenylene sulfide and polyetherimide, along with a specific flame-retardant formulation, ensures both flame retardancy and material strength and toughness. The conductive layer, based on an elastomer matrix and containing a dispersed biphase conductive network, utilizes a conductive network formed by nickel-plated carbon fiber and copper-plated silicon carbide particles. This network not only rapidly conducts static electricity, achieving antistatic functionality, but the elastomer matrix also provides the conductive layer with good flexibility and wear resistance, avoiding the surface wear and failure problems caused by traditional high-filler conductive agents.

[0044] In this embodiment, the buffer layer comprises maleic anhydride-grafted polyethylene. The buffer layer, by weight, comprises the following components: 90-100 parts maleic anhydride-grafted polyethylene, 0-10 parts hydrogenated styrene-butadiene-styrene block copolymer (SEBS), 0.1-0.5 parts antioxidant 1010, and 0.1-0.5 parts antioxidant 168. Preferably, the buffer layer comprises 95 parts maleic anhydride-grafted polyethylene, 5 parts hydrogenated styrene-butadiene-styrene block copolymer (SEBS), 0.3 parts antioxidant 1010, and 0.3 parts antioxidant 168. Maleic anhydride-grafted polyethylene has good polarity and reactivity, enabling better compatibility with polar polymer-modified polyolefins, further enhancing the performance of the buffer layer. It can improve the interfacial bonding force between the buffer layer and the spiral welded corrugated steel pipe skeleton, allowing the buffer layer to adhere more tightly to the skeleton, thereby improving the structural stability of the entire composite corrugated pipe. Meanwhile, maleic anhydride-grafted polyethylene can improve the flexibility and elasticity of the buffer layer, enabling it to better absorb and disperse energy under external forces, reducing damage to the pipe. Hydrogenated styrene-butadiene-styrene block copolymer (SEBS), purchased from Guangzhou Jiushun New Materials Co., Ltd., grade 7551, possesses excellent aging resistance, weather resistance, and flexibility. When used in combination with maleic anhydride-grafted polyethylene, it can further enhance the overall performance of the buffer layer. It can increase the elastic modulus of the buffer layer, improve its stability under different temperature environments, and ensure the pipe maintains good performance during long-term use. The addition of antioxidants 1010 and 168 can effectively prevent oxidative degradation of the buffer layer material during processing and use, extending the service life of the buffer layer and ensuring its long-term performance stability.

[0045] In this embodiment, the flame-retardant layer comprises an alloy of polyphenylene sulfide and polyetherimide, and a flame retardant. The flame-retardant layer provides the pipe structure with rigidity, strength, and core flame-retardant properties. Further, the weight ratio of polyphenylene sulfide to polyetherimide is (50-70):(30-50), and the flame retardant comprises aluminum hypophosphite, zinc molybdate, and nano-silica.

[0046] The flame-retardant layer comprises, by weight parts, the following components: 50-70 parts polyphenylene sulfide, 30-50 parts polyetherimide, 10-20 parts aluminum hypophosphite, 3-5 parts zinc molybdate, 1-3 parts nano-silica, and 0.2-0.8 parts ultrafine polytetrafluoroethylene (PTFE) powder. Preferably, the flame-retardant layer comprises, by weight parts, 60 parts polyphenylene sulfide, 40 parts polyetherimide, 15 parts aluminum hypophosphite, 4 parts zinc molybdate, 2 parts nano-silica, and 0.5 parts ultrafine polytetrafluoroethylene (PTFE) powder.

[0047] Polyphenylene sulfide (PPS) is a crystalline, high-performance thermoplastic engineering plastic with excellent high-temperature resistance, chemical corrosion resistance, flame retardancy, and mechanical properties. Polyetherimide (PEI) is a non-crystalline, high-performance engineering plastic with high heat resistance, high strength, high rigidity, and good processability. Alloying PPS and PII in a specific ratio combines the advantages of both, resulting in a flame-retardant layer that possesses both good rigidity and strength, as well as excellent heat resistance and flame retardancy. Aluminum hypophosphite is a novel inorganic phosphorus-based flame retardant with advantages such as high efficiency, low toxicity, and low smoke. At high temperatures, it decomposes to produce phosphoric acid and metaphosphite, forming a dense char layer that prevents the transfer of oxygen and heat, thus achieving flame retardancy. Zinc molybdate is an environmentally friendly flame retardant synergist that can work synergistically with aluminum hypophosphite to enhance the flame retardant effect. During combustion, zinc molybdate can form stable complexes with other flame retardants, enhancing the strength and stability of the char layer and further inhibiting the spread of fire. Nano-silica possesses a large specific surface area and high surface activity, allowing it to act as a reinforcing agent to improve the mechanical properties and thermal stability of flame-retardant layers. Simultaneously, nano-silica can form a protective silica film during combustion, providing heat insulation and oxygen barrier functions, further aiding in flame retardancy. Ultrafine polytetrafluoroethylene (PTFE) powder can serve as a lubricant and anti-dripping agent, improving the processing and flame-retardant properties of the flame-retardant layer and preventing dripping during combustion.

[0048] In this embodiment, the conductive layer is used to resist mechanical wear and provide durable and stable antistatic properties. The elastomer is thermoplastic polyurethane, the fibrous conductive filler in the conductive layer is nickel-plated carbon fiber, and the granular conductive filler is copper-plated silicon carbide particles.

[0049] In this embodiment, based on the total weight of the conductive layer, the content of the fibrous conductive filler is 2-6 wt%, and the content of the particulate conductive filler is 8-15 wt%.

[0050] The conductive layer, by weight, comprises the following components: 100 parts thermoplastic polyurethane, 2-6 parts nickel-plated carbon fiber, 8-15 parts copper-plated silicon carbide particles, 1-2 parts dispersant (polyethylene wax), and 3-5 parts polyurethane adhesion promoter. Preferably, the conductive layer, by weight, comprises the following components: 100 parts thermoplastic polyurethane, 4 parts nickel-plated carbon fiber, 10 parts copper-plated silicon carbide particles, 1.5 parts dispersant (polyethylene wax), and 4 parts polyurethane adhesion promoter.

[0051] The thermoplastic polyurethane possesses excellent flexibility, wear resistance, and chemical corrosion resistance. As the matrix of the conductive layer, it provides a stable supporting structure for the nickel-plated carbon fiber and copper-plated silicon carbide particles. The nickel-plated carbon fiber is 150 μm long, 7 μm in diameter, and has a coating thickness of 0.5 μm, serving as a "long-range conductive skeleton." This nickel-plated carbon fiber was purchased from Shanghai Lishuo Composite Materials Technology Co., Ltd. The nickel-plated carbon fiber exhibits excellent conductivity and high strength, enabling it to form effective conductive pathways within the conductive layer and rapidly dissipate static electricity. The silicon carbide core particle size (D50) is 20 μm, and the chemically plated copper layer is 1 μm thick, serving as a "locally conductive reinforcing and wear-resistant phase." This copper-plated silicon carbide particle was purchased from Hangzhou Jiayou New Materials Co., Ltd., CAS No. 409-21-2. The copper-plated silicon carbide particle not only possesses good conductivity but also high hardness and wear resistance, enhancing the wear resistance of the conductive layer and preventing surface damage due to friction. The addition of a dispersant (polyethylene wax) ensures uniform dispersion of nickel-plated carbon fiber and copper-plated silicon carbide particles within the thermoplastic polyurethane matrix, preventing filler agglomeration and thus guaranteeing the stability and uniformity of the conductive layer's performance. The polyurethane adhesion promoter was purchased from Wuhan Jihechang New Materials Co., Ltd.

[0052] In this embodiment, the spiral welded corrugated steel pipe skeleton has a wall thickness of 1.0-1.5 mm, and its outer wall has a hollow spiral reinforcing rib structure formed by cold pressing. Furthermore, the spiral welded corrugated steel pipe skeleton of this antistatic composite corrugated pipe also has unique advantages. Its wall thickness of 1.0-1.5 mm ensures the strength of the skeleton without making the pipe too heavy. The hollow spiral reinforcing rib structure on the outer wall further enhances the ring stiffness and compressive strength of the pipe, enabling it to withstand greater external pressure and adapt to the complex geological conditions and working environment of underground coal mines. Simultaneously, this structure also increases the flexibility of the pipe, allowing for better bending and laying during installation, reducing installation difficulty and cost.

[0053] In practical applications, the antistatic properties of this antistatic composite corrugated pipe effectively prevent static electricity buildup from generating sparks, reducing the risk of gas explosions and ensuring the safety of coal mine production. Its flame-retardant properties prevent the spread of fire in the event of a fire, protecting the integrity of the pipeline and reducing losses caused by fire. Its good flexibility and impact resistance allow it to adapt to complex underground geological conditions and installation environments, and it is not easily damaged even when subjected to external impacts.

[0054] A second aspect of the present invention provides a method for preparing an antistatic composite corrugated pipe, comprising the following steps:

[0055] (a) Provide a spiral welded corrugated steel pipe skeleton and clean and activate its outer surface;

[0056] (b) A buffer layer and a flame-retardant layer are sequentially formed on the spiral welded corrugated steel pipe skeleton by co-extrusion composite method to form a composite base pipe;

[0057] (c) A conductive layer is formed on the outer surface of the composite base tube by a powder sintering process;

[0058] (d) Cool and shape the composite tube after it is coated with the conductive layer and perform post-treatment.

[0059] Specifically, this method also includes raw material pretreatment:

[0060] (1) PPS was dried in a forced-air oven at 140°C for 4 hours; PEI was dried in a vacuum oven at 150°C for 6 hours; and TPU was dried in a dehumidifying dryer at 80°C for 4 hours. All fillers (aluminum hypophosphite, Sb2O3, Ni-CF, Cu-SiC) were dried at 110°C for 2 hours.

[0061] (2) Two co-rotating twin-screw extruders (length-to-diameter ratio L / D=40:1) were used to prepare functional masterbatches for each layer; the process parameters for each layer are shown in Table 1.

[0062] Table 1 Process parameters for each layer

[0063]

[0064] After extrusion, the material is water-cooled and pelletized to obtain functional masterbatches for each layer. Two single-screw extruders and a specially designed composite die are used.

[0065] In this embodiment, the cleaning and activation treatment in step (a) is atmospheric pressure plasma treatment; the working gas of the plasma treatment is a mixture of argon and oxygen, wherein the volume percentage of oxygen is 3%-10%.

[0066] Specifically, the corrugated steel pipe is passed through an atmospheric pressure plasma treatment device at a speed of 1.5 m / min, with a power of 2.0 kW. The treatment gas is a mixture of argon (95%) and oxygen (5%), and the nozzle is 10 mm away from the surface of the steel pipe.

[0067] In step (b) of this embodiment, the spiral welded corrugated steel pipe skeleton is preheated to 180°C-190°C, the melt of the buffer layer is extruded using a first extruder, and the melt of the flame retardant layer is extruded using a second extruder. The two melt layers and the preheated steel pipe skeleton are introduced into a composite die for lamination. The temperature of the composite die is set to 290-320°C, and the laminated pipe is subjected to gradient cooling.

[0068] In step (c), a conductive layer is formed on the outer surface of the composite base tube using a powder sintering process. This powder sintering process includes: cleaning and activating the outer surface of the composite base tube; uniformly applying powder made from the conductive layer's raw materials to the activated outer surface via electrostatic adsorption; and melting and sintering the powder using an inside-out heating method to form a dense conductive layer. The inside-out heating method is induction heating, where an induction coil heats the internal steel tube frame, transferring the heat to the outer powder layer, causing it to melt and sinter within a temperature range of 180-190°C.

[0069] In this embodiment, in step (d), the coated composite pipe immediately enters a three-stage cooling water tank, wherein:

[0070] Zone 1 (Hot Air Slow Cooling Zone): 4 meters long, hot air temperature 130℃, to allow the intermediate layer of PPS / PEI to fully crystallize.

[0071] Second zone (spray cooling zone): 6 meters long, water temperature 15℃, to quickly set the inner and outer layers.

[0072] The third zone (immersion cooling zone): 4 meters in length, with a water temperature of 25°C, allows the pipe to cool down evenly to room temperature, eliminating internal stress.

[0073] The final product is obtained through online detection with a laser diameter gauge, inkjet printing, and fixed-length cutting.

[0074] The third aspect of this application provides an application of the aforementioned antistatic composite corrugated pipe in a coal mine gas extraction system.

[0075] Example

[0076] The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight. Unless otherwise stated, all reagents used in the examples are available commercially or synthesized using conventional methods and are ready for use without further processing. Unless otherwise stated, all instruments used in the examples are available commercially.

[0077] Example 1

[0078] An antistatic composite corrugated pipe includes a spiral welded corrugated steel pipe skeleton and a functional coating composited on the inner and outer surfaces of the spiral welded corrugated steel pipe skeleton; the functional coating has a three-layer gradient structure, from the inside to the outside as follows:

[0079] The buffer layer comprises, by weight, 95 parts maleic anhydride-grafted polyethylene, 5 parts hydrogenated styrene-butadiene-styrene block copolymer (SEBS), 0.3 parts antioxidant 1010, and 0.3 parts antioxidant 168;

[0080] The flame-retardant layer comprises, by weight parts, 60 parts of polyphenylene sulfide, 40 parts of polyetherimide, 15 parts of aluminum hypophosphite, 4 parts of zinc molybdate, 2 parts of nano-silica, and 0.5 parts of polytetrafluoroethylene ultrafine powder.

[0081] The conductive layer comprises, by weight, 100 parts thermoplastic polyurethane, 4 parts nickel-plated carbon fiber, 10 parts copper-plated silicon carbide particles, and 1.5 parts polyethylene wax.

[0082] The preparation method of the antistatic composite corrugated pipe includes the following steps:

[0083] (a) The corrugated steel pipe is passed through an atmospheric pressure plasma treatment device at a speed of 1.5 m / min, with a power of 2.0 kW. The treatment gas is a mixture of argon (95%) and oxygen (5%), and the nozzle is 10 mm away from the surface of the steel pipe.

[0084] (b) The spiral welded corrugated steel pipe skeleton is preheated, the melt of the buffer layer is extruded using a first extruder, the melt of the flame retardant layer is extruded using a second extruder, and the two melts and the preheated steel pipe skeleton are introduced into a composite die for lamination, wherein the temperature of the composite die is set to 290-320°C, and the lamination pipe is subjected to gradient cooling to form a composite base pipe.

[0085] (c) The outer surface of the composite base tube is cleaned and treated with atmospheric pressure plasma to activate the surface and increase its surface energy. A thin layer of polyurethane adhesion promoter is sprayed on the composite base tube. The other raw materials of the conductive layer are made into powder with a particle size of 80-120 mesh. The composite base tube is grounded and passed through a powder electrostatic spraying chamber. The negatively charged powder is uniformly adsorbed on the entire outer surface of the tube. The tube with uniformly adsorbed powder is passed through a medium frequency induction heating coil. The induction coil heats the internal steel tube frame and conducts the heat to the outer powder, so that it melts and sintersects and flows in the temperature range of 180-190°C to form a dense conductive layer.

[0086] (d) Immediately place the coated composite pipe into a three-stage cooling water tank, wherein:

[0087] Zone 1 (Hot Air Slow Cooling Zone): 4 meters long, hot air temperature 130℃, to allow the intermediate layer of PPS / PEI to fully crystallize.

[0088] Second zone (spray cooling zone): 6 meters long, water temperature 15℃, to quickly set the inner and outer layers.

[0089] The third zone (immersion cooling zone): 4 meters in length, with a water temperature of 25°C, allows the pipe to cool down evenly to room temperature, eliminating internal stress.

[0090] Example 2

[0091] The preparation method of this embodiment is the same as that of Example 1, except that in the functional coating:

[0092] The buffer layer comprises, by weight, 100 parts maleic anhydride-grafted polyethylene, 0.3 parts antioxidant 1010, and 0.3 parts antioxidant 168;

[0093] The flame-retardant layer comprises, by weight parts, 70 parts polyphenylene sulfide, 30 parts polyetherimide, 10 parts aluminum hypophosphite, 3 parts zinc molybdate, 1 part nano silica, and 0.5 parts polytetrafluoroethylene ultrafine powder.

[0094] The conductive layer comprises, by weight, 100 parts thermoplastic polyurethane, 3 parts nickel-plated carbon fiber, 8 parts copper-plated silicon carbide particles, and 1.5 parts polyethylene wax.

[0095] Example 3

[0096] The preparation method of this embodiment is the same as that of Example 1, except that in the functional coating:

[0097] The buffer layer comprises, by weight, 90 parts maleic anhydride-grafted polyethylene, 10 parts hydrogenated styrene-butadiene-styrene block copolymer (SEBS), 0.3 parts antioxidant 1010, and 0.3 parts antioxidant 168;

[0098] The flame-retardant layer comprises, by weight parts, 50 parts of polyphenylene sulfide, 50 parts of polyetherimide, 20 parts of aluminum hypophosphite, 5 parts of zinc molybdate, 3 parts of nano-silica, and 0.5 parts of polytetrafluoroethylene ultrafine powder.

[0099] The conductive layer comprises, by weight, 100 parts thermoplastic polyurethane, 5 parts nickel-plated carbon fiber, 12 parts copper-plated silicon carbide particles, and 1.5 parts polyethylene wax.

[0100] Example 4

[0101] The preparation method of this embodiment is the same as that of Example 1, except that in the functional coating:

[0102] The buffer layer comprises, by weight, 95 parts maleic anhydride-grafted polyethylene, 5 parts hydrogenated styrene-butadiene-styrene block copolymer (SEBS), 0.3 parts antioxidant 1010, and 0.3 parts antioxidant 168;

[0103] The flame-retardant layer comprises, by weight parts, 60 parts of polyphenylene sulfide, 40 parts of polyetherimide, 15 parts of aluminum hypophosphite, 4 parts of zinc molybdate, 2 parts of nano-silica, and 0.5 parts of polytetrafluoroethylene ultrafine powder.

[0104] The conductive layer comprises, by weight, 100 parts thermoplastic polyurethane, 2 parts nickel-plated carbon fiber, 15 parts copper-plated silicon carbide particles, and 1.5 parts polyethylene wax.

[0105] Example 5

[0106] The preparation method of this embodiment is the same as that of Example 1, except that in the functional coating:

[0107] The buffer layer comprises, by weight, 95 parts maleic anhydride-grafted polyethylene, 5 parts hydrogenated styrene-butadiene-styrene block copolymer (SEBS), 0.3 parts antioxidant 1010, and 0.3 parts antioxidant 168;

[0108] The flame retardant layer comprises, by weight parts, 55 parts polyphenylene sulfide, 45 parts polyetherimide, 18 parts aluminum hypophosphite, 4.5 parts zinc molybdate, 2.5 parts nano silica, and 0.5 parts polytetrafluoroethylene ultrafine powder.

[0109] The conductive layer comprises, by weight, 100 parts thermoplastic polyurethane, 6 parts nickel-plated carbon fiber, 8 parts copper-plated silicon carbide particles, and 1.5 parts polyethylene wax.

[0110] Comparative Example 1

[0111] This comparative example is basically the same as Example 1, except that the conductive layer does not use a two-phase conductive network, but only 8 parts of conductive carbon black are used as an antistatic agent.

[0112] Comparative Example 2

[0113] This comparative example is basically the same as Example 1, except that the flame retardant layer does not use PPS / PEI alloy, but only 100 parts of PPS.

[0114] Comparative Example 3

[0115] This comparative example is basically the same as Example 1, except that no copper-plated silicon carbide particles are added to the outer layer of the conductive layer, and only 4 parts of nickel-plated carbon fiber are used.

[0116] Comparative Example 4

[0117] This comparative example is basically the same as Example 1, except that step (a) of plasma treatment of the steel pipe skeleton is omitted, and the flame retardant layer uses ordinary high-density polyethylene instead of maleic anhydride-grafted polyethylene.

[0118] Comparative Example 5

[0119] This comparative example is basically the same as Example 1, except that the cooling process in step (d) uses direct water cooling (20°C) instead of zoned gradient cooling.

[0120] Experimental Case 1

[0121] The following tests were conducted on the bellows of Examples 1-5 and Comparative Examples 1-5:

[0122] Surface resistivity: Measured on the outer surface of the pipe using a high-resistivity meter according to GB / T 1410-2006 standard.

[0123] Abrasion resistance: According to GB / T 1768-2006 standard, using a Taber abrasion tester (CS10 grinding wheel, 1kg load), record the mass loss (mg) and surface resistivity after 1000 abrasion cycles.

[0124] The test results are shown in Table 2.

[0125] Table 2. Results of antistatic and abrasion resistance durability tests for Examples 1-5 and Comparative Examples 1-5

[0126]

[0127] As shown in Table 2, the resistivity of Examples 1-5 increased only slightly after wear, remaining at around 10. 4 -10 5 The excellent antistatic performance of Ω / sq is due to the fact that even if the Ni-CF network on the surface is partially worn away, the Cu-SiC particles inside and on the surface of the conductive layer quickly fill the gap, forming new conductive pathways. The Cu-SiC particles play a dual role of wear resistance and conductivity, which is the key to achieving long-lasting antistatic performance.

[0128] Comparative Example 1: Using only conductive carbon black, the carbon black layer was completely worn away after abrasion, exposing the insulating TPU matrix, and the antistatic function was completely lost; Comparative Example 3: Lacking the Cu-SiC particle backup network, the Ni-CF network was broken after abrasion, the conductivity decreased significantly, and the surface resistivity increased to 10. 8 The effect is on the order of Ω / sq. Comparative Example 2: Using only PPS without the PPS / PEI alloy, although the initial performance is acceptable, during long-term use, due to the inherent characteristics of PPS, the durability of wear resistance and antistatic properties may not be as good as that achieved with the alloy in the examples. Comparative Example 4: The plasma treatment step for the steel pipe skeleton was omitted, and ordinary high-density polyethylene was used instead of maleic anhydride-grafted polyethylene for the flame-retardant layer. This may reduce the bonding strength between the functional coating and the steel pipe skeleton; however, the results show little impact on initial performance, but it may affect the overall performance stability during long-term use.

[0129] Experimental Case 2

[0130] The following tests were conducted on the bellows of Examples 1-5 and Comparative Examples 1-5:

[0131] Flame retardancy: Evaluated according to the alcohol torch burning test in MT 181-1988 "Safety Performance Inspection Specification for Plastic Pipes Used in Coal Mines". Record the flaming burning time, the flameless burning time, and whether melting and dripping occur.

[0132] The test results are shown in Table 3.

[0133] Table 3 Flame retardancy test results of Examples 1-5 and Comparative Examples 1-5

[0134]

[0135] As shown in Table 3, Examples 1-5 all exhibited excellent flame retardancy (extremely short flaming time and no dripping). This is due to the synergistic effect of the PPS / PEI alloy with flame retardants such as aluminum hypophosphite and zinc molybdate. PPS itself has certain flame retardancy, while PEI can form a stable char layer at high temperatures, further preventing the spread of combustion. Aluminum hypophosphite, zinc molybdate, and nano-silica, as highly efficient flame retardants, can decompose during combustion to produce inert gases and refractory oxides, diluting oxygen and covering the material surface, thereby inhibiting combustion. Comparative Example 1: Both flaming and extinguished flame times were long, and melting and dripping occurred. This is because only conductive carbon black was used as an antistatic agent, without an effective flame retardant system. The material could not form an effective barrier layer during combustion, resulting in a long combustion duration and easy dripping. Comparative Example 2: Although the flaming time was short, melting and dripping occurred. Only PPS was used without the PPS / PEI alloy, and a stable char layer could not be formed during combustion, making the flame retardant performance of the material less than ideal. Comparative Example 3: The flame retardant performance is similar to that of the Example, indicating that the absence of copper-plated silicon carbide particles and nickel-plated carbon fiber has little impact on the flame retardant performance. The flame retardant performance mainly depends on the flame retardant system of the flame retardant layer. Comparative Example 4: The flame retardant performance is similar to that of the Example. Eliminating the plasma treatment step of the steel pipe skeleton and using ordinary high-density polyethylene instead of maleic anhydride-grafted polyethylene in the flame retardant layer has no significant impact on the flame retardant performance, indicating that these improvements mainly affect the bonding strength between the functional coating and the steel pipe skeleton, and other properties, rather than the flame retardant performance. Comparative Example 5: The flame retardant performance is similar to that of the Example. Using direct water cooling instead of zoned gradient cooling has no significant impact on the flame retardant performance, indicating that the cooling process mainly affects the internal stress and crystallization of the material, and has a relatively small impact on the flame retardant performance. In this invention, this multi-component flame retardant system enables the corrugated pipe to quickly form a heat insulation layer when exposed to a fire source, effectively preventing the spread of flames and the transfer of heat.

[0136] Experimental Case 3

[0137] The following tests were conducted on the bellows of Examples 1-5 and Comparative Examples 1-5:

[0138] Interlayer peel strength: In accordance with GB / T 2790-1995, standard specimens were prepared and the peel force (N / cm) between layers was tested using a universal tensile testing machine.

[0139] Ring stiffness: Tested according to GB / T 9647-2015 standard.

[0140] The test results are shown in Table 4.

[0141] Table 4. Mechanical property test results of Examples 1-5 and Comparative Examples 1-5

[0142]

[0143] *Note: Due to the extremely poor interlayer bonding in Comparative Example 4, the cladding layer and the skeleton slipped relative to each other during the test, resulting in a distorted and lower ring stiffness test value.

[0144] As shown in Table 4, Examples 1-5 exhibit a peel strength of approximately 50 N / cm, with cohesive failure as the failure mode, indicating that the interfacial strength is higher than that of the material itself. This is direct evidence that plasma-activated active groups form strong chemical bonds with the anhydride groups in maleic anhydride-grafted polyethylene.

[0145] Comparative Example 4 (Weak Interface): A peel strength of only 12 N / cm indicates that the interface is merely physically adsorbed and is extremely prone to failure under stress. Its extremely low ring stiffness test value is not due to the material itself being inadequate, but rather because the coating and the skeleton have become "disconnected," unable to cooperate in bearing stress, which is disastrous in engineering applications. Comparative Example 5 (Rapid Cooling): A peel strength of 35 N / cm, while higher than Comparative Example 4, is far lower than the example. This is because rapid cooling causes uneven cooling shrinkage in each layer, especially the crystalline polymer, generating enormous internal stress. This stress weakens the effective bonding force of the interface.

[0146] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. An antistatic composite corrugated pipe, characterized in that, It includes a spiral welded corrugated steel pipe skeleton and a functional coating composited on the inner and outer surfaces of the spiral welded corrugated steel pipe skeleton; the functional coating is a three-layer gradient structure, consisting of a buffer layer, a flame-retardant layer, and a conductive layer, from the surface near the spiral welded corrugated steel pipe skeleton to the surface away from the spiral welded corrugated steel pipe skeleton. The buffer layer comprises, by weight, the following components: 90-100 parts of maleic anhydride-grafted polyethylene, 0-10 parts of hydrogenated styrene-butadiene-styrene block copolymer, 0.1-0.5 parts of antioxidant 1010, and 0.1-0.5 parts of antioxidant 168; The flame-retardant layer comprises the following components in parts by weight: 50-70 parts polyphenylene sulfide, 30-50 parts polyetherimide, 10-20 parts aluminum hypophosphite, 3-5 parts zinc molybdate, 1-3 parts nano silica, and 0.2-0.8 parts polytetrafluoroethylene ultrafine powder. The conductive layer has an elastomer as its matrix and disperses a two-phase conductive network comprising fibrous conductive fillers and granular conductive fillers; the fibrous conductive fillers are nickel-plated carbon fibers; the granular conductive fillers are copper-plated silicon carbide particles; based on the total weight of the conductive layer, the content of the fibrous conductive fillers is 2-6 wt%, and the content of the granular conductive fillers is 8-15 wt%. The conductive layer is formed on the outer surface of a composite base tube with a buffer layer and a flame-retardant layer by a powder sintering process. The conductive layer comprises the following components in parts by weight: 100 parts thermoplastic polyurethane, 2-6 parts nickel-plated carbon fiber, 8-15 parts copper-plated silicon carbide particles, 1-2 parts polyethylene wax, and 3-5 parts polyurethane adhesion promoter.

2. The antistatic composite corrugated pipe according to claim 1, characterized in that, The wall thickness of the spiral welded corrugated steel pipe skeleton is 1.0-1.5 mm, and the outer wall of the spiral welded corrugated steel pipe skeleton is provided with a hollow spiral reinforcing rib structure formed by cold pressing.

3. A method for preparing an antistatic composite corrugated pipe, characterized in that, The method for preparing the antistatic composite corrugated pipe according to any one of claims 1-2 includes the following steps: (a) Provide a spiral welded corrugated steel pipe skeleton and clean and activate its outer surface; (b) A buffer layer and a flame-retardant layer are sequentially formed on the spiral welded corrugated steel pipe skeleton by co-extrusion composite method to form a composite base pipe; (c) A conductive layer is formed on the outer surface of the composite base tube by a powder sintering process; (d) Cool and shape the composite tube after it is coated with the conductive layer and perform post-treatment.

4. The method for preparing the antistatic composite corrugated pipe according to claim 3, characterized in that, The cleaning and activation process described in step (a) is atmospheric pressure plasma treatment; And / or, the working gas for the plasma treatment is a mixture of argon and oxygen, wherein the oxygen volume percentage is 3%-10%.

5. The method for preparing the antistatic composite corrugated pipe according to claim 3, characterized in that, In step (b), the spiral welded corrugated steel pipe skeleton is preheated, the melt of the buffer layer is extruded using a first extruder, the melt of the flame retardant layer is extruded using a second extruder, and the two melt layers and the preheated steel pipe skeleton are introduced into a composite die for lamination. The temperature of the composite die is set to 290-320℃, and the lamination pipe is subjected to gradient cooling. And / or, in step (c), the powder sintering process includes: cleaning and activating the outer surface of the composite base tube, uniformly applying the powder made from the raw material of the conductive layer to the activated outer surface by electrostatic adsorption, and melting and sintering the powder by heating from the inside out to form a dense conductive layer.

6. The method for preparing the antistatic composite corrugated pipe according to claim 3, characterized in that, In step (d), the cooling and shaping process employs a zoned gradient cooling method, including: First, enter the hot air slow cooling zone, where the temperature is controlled at 120-150℃; Then enter the spray cooling zone, where the water temperature is controlled at 10-20℃.

7. The application of the antistatic composite corrugated pipe as described in any one of claims 1-2 in a coal mine gas extraction system.

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