A continuous fiber filament wound reinforced polyethylene composite pipe and a method of making the same

Abstract

The present application relates to the technical field of composite pipe, in particular to a continuous fiber winding reinforced polyethylene composite pipe and a preparation method thereof, wherein the continuous fiber winding reinforced polyethylene composite pipe is composed of an inner polyethylene pipe, a fiber reinforced layer wound on the inner polyethylene pipe, an outer polyethylene protective layer wound outside the fiber reinforced layer, and an outer reinforced pipe wound on the surface of the outer polyethylene protective layer. The continuous fiber winding reinforced polyethylene composite pipe prepared by the present application has excellent flexibility, simple production process, high production efficiency, and can realize all production processes of multi-layer composite through one station.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite pipes, in particular to a continuous fiber winding reinforced polyethylene composite pipe and a preparation method thereof. BACKGROUND

[0002] At present, the main pipe materials used in the application market of medium and large diameter pipes are prestressed steel cylinder cement pipes, ductile cast iron pipes and welded steel pipes. However, these pipe materials have some defects. For example, the prestressed steel wire of the prestressed steel cylinder cement pipe is easy to break, causing the pipe to fail, and the self weight of the pipe is large, so the construction and installation cost is high. The metal pipe cannot be buried in the underground with acid, alkali and salt corrosion, and the corrosion resistance and flexibility of the pipe are poor. The polyethylene pipe has the advantages of good corrosion resistance, strong compression resistance and light weight compared with the prestressed steel cylinder cement pipe and the metal pipe. However, the rigidity of the polyethylene pipe is low, and the compression capacity is poor.

[0003] Winding glass fiber tape on the surface of the polyethylene pipe is an effective method to improve the rigidity and tensile strength of the polyethylene pipe. However, the existing production method of winding glass fiber tape reinforcing layer in the industry is to first wind the inner layer base pipe, then hoist the mold of the wound base pipe to another work station for the winding fiber tape process, and only wind along one side of the base pipe in one direction, without left-right cross winding, which causes poor stability of the winding composite process, and easily causes the hidden danger of delamination failure of the reinforced composite layer. The existing process also lacks the process of arranging the fiber reinforcing layer along the axis of the base pipe, which causes the insufficient axial tensile strength of the polyethylene pipe. After winding the fiber reinforcing layer, the drum mold needs to be hoisted again to the extrusion process for the winding of the protective layer and the winding of the outer pressure-resistant reinforcing pipe. This way of hoisting the drum mold multiple times not only wastes time and causes low production efficiency, but also causes large heat loss during hoisting, and is prone to the problem of poor composite welding. In addition, in the existing technology, the abrupt transition of about 45° angle is adopted between the socket section and the straight pipe section without slope design, which makes it difficult to wind the fiber to the socket section. Even if the fiber is forced to wind, the angle will change suddenly, which will cause the fiber to not fit the pipe body well, seriously affecting the realization of the production process and the quality of the final product.

[0004] Patent CN119081271A discloses a kind of weathering anti-aging polyethylene pipeline and its preparation method, pipeline uses high-density polyethylene resin, linear low-density polyethylene resin, polyimide resin micro powder, nano silicon dioxide, nano hexagonal boron nitride, polybenzimidazole fiber, salvinic acid, zinc glycyrrhetinate, antioxidant 1010, hindered amine light stabilizer, polydimethylsiloxane titanate crosslinking polymer, 3-methacryloyl oxypropyl triethoxysilane is raw material;Among them, polyimide resin micro powder, salvinic acid and zinc glycyrrhetinate are uniformly mixed, then modified at 300-350 DEG C for 30-60 min, to obtain modified substance, can better improve the weather resistance, anti-aging of pipeline.Each component is compatible with each other, special modification preparation method is adopted, and the synergistic effect of components is better, the weather resistance and anti-aging of polyethylene pipeline are greatly improved.However, the formula has the problems of high cost and complex processing technology, among which, nano materials such as nano silicon dioxide and boron nitride are prone to agglomeration, and the compatibility of polyimide, polybenzimidazole and polyethylene is poor, and the processing temperature of the former two is higher than that of polyethylene, which may cause degradation of part of polyethylene.

[0005] Patent CN104448488A discloses a kind of fiber reinforced polyethylene pipeline material, which is prepared from the following raw materials in weight parts: polyethylene resin, carbon black, fiber, compatibilizer, coupling agent, lubricant, antioxidant;The fiber is one or more of surface-treated glass fiber, carbon fiber and basalt fiber;The fiber length is 1-8 mm. The compatibilizer is maleic anhydride grafted polyethylene;The coupling agent is one of silane coupling agent, titanate coupling agent and aluminate coupling agent;The lubricant is one of erucamide, calcium stearate, zinc stearate, stearic acid and polyethylene wax;The antioxidant is a complex of hindered phenolic antioxidant 1010 or 1076 and phosphite antioxidant 168. It has good mechanical properties, excellent weather resistance, high strength, good aging resistance, good safety, long service life and other advantages. However, adding a large amount of fiber filler during polyethylene processing can increase the melt viscosity, affecting the processing performance of the raw material. The addition of fiber can improve the tensile strength and stiffness, but also cause the toughness, ductility and compression resistance of the material to decrease.

[0006] Therefore, there is an urgent need in the market for a polyethylene composite pipe with excellent rigidity and compression resistance, reliable pipe interface quality and high production efficiency. SUMMARY

[0007] To solve the problems in the prior art, the purpose of the present application is to obtain a continuous fiber winding reinforced polyethylene composite pipe with excellent rigidity and compression resistance, strong adhesion between layers, the same structural strength of each part of the pipe and high production efficiency.

[0008] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0009] The present application provides a continuous fiber winding reinforced polyethylene composite pipe, which comprises an inner polyethylene pipe, a fiber reinforced layer wound on the inner polyethylene pipe, an outer polyethylene protective layer wound outside the fiber reinforced layer, and an outer reinforced pipe wound on the surface of the outer polyethylene protective layer.

[0010] The present application provides a preparation method of a continuous fiber winding reinforced polyethylene composite pipe, which comprises the following steps:

[0011] S1, the core pipe polyethylene material is added to the core pipe extruder, the heating wire is pre-buried at the end of the core pipe die socket, the gas jet flame is used to pre-heat the core pipe die, and the inner polyethylene pipe is obtained by melting extrusion winding at 170-220 DEG C. The fiber belt is wound on the inner polyethylene pipe through the forward and reverse annular cross winding and the axial multi-layer winding composite machine group to form a fiber reinforced layer; the outer layer polyethylene material is added to the extruder, and the outer polyethylene protective layer is formed by extrusion winding on the surface of the fiber reinforced layer to obtain a fiber reinforced polyethylene composite pipe with a three-layer structure of inner and outer polyethylene pipes and a fiber reinforced layer in the middle;

[0012] S2, the polypropylene material is added to the single-wall corrugated pipe extruder, the polyethylene material is added to the extruder, and the outer reinforced pipe with the inner polypropylene layer and the outer polyethylene layer is obtained by co-extrusion at 200-220 DEG C.

[0013] S3, the outer reinforced pipe obtained in step S2 is wound on the fiber reinforced polyethylene composite pipe obtained in step S1 to obtain a continuous fiber winding reinforced polyethylene composite pipe.

[0014] Preferably, the thickness of the polypropylene layer in the outer reinforced pipe is 2-4 mm, and the thickness of the polyethylene layer is 1.5-6 mm.

[0015] The present application realizes all production processes of multi-layer composite in one station, the resistance wire can be pre-arranged on the core pipe die through the groove outside the end of the die socket, the problem of resistance wire arrangement and maintenance is solved, the heat efficiency is improved, the uniformity of heat distribution is guaranteed, and the product quality is improved. The fiber belt is wound on the inner polyethylene pipe through the forward and reverse annular cross winding and the axial multi-layer winding composite machine group, the function of bidirectional reinforcement of annular and axial directions is realized, and the compression resistance of the product is improved.

[0016] In some embodiments, the core pipe polyethylene material contains the following raw materials by mass fraction: high-density polyethylene 60-90 parts, compatibilizer 2-6 parts, and antioxidant 0.1-1 part.

[0017] In some embodiments, the preparation method of the compatibilizer comprises the following steps:

[0018] A1, hexagonal boron nitride and KH-550 silane coupling agent are added into an ethanol aqueous solution, ultrasonic treatment is performed at 40-50°C for 40-60 min, and drying is performed to obtain modified hexagonal boron nitride;

[0019] A2, itaconic acid, dicumyl peroxide and linear low-density polyethylene are uniformly mixed in a high-speed mixer, the modified hexagonal boron nitride obtained in step A1 and sodium hypophosphite are added and uniformly mixed to obtain a mixture;

[0020] A3, the mixture obtained in step A2 is added into a twin-screw extruder, and extrusion is performed at 170-190°C to obtain the product.

[0021] In some embodiments, the mass ratio of the hexagonal boron nitride and the KH-550 silane coupling agent is 1: (0.05-0.15).

[0022] The present application uses itaconic acid to modify linear low-density polyethylene, so that a large number of carboxyl groups are contained on the prepared compatilizer, and the addition of the compatilizer into the core pipe polyethylene material can enhance the interaction force between the glass fiber and the core pipe, enhance the adhesion between the fiber reinforced layer and the inner layer and the protective layer, and is beneficial to improving the rigidity and internal pressure bearing performance of the composite pipe.

[0023] The present application further adds modified hexagonal boron nitride in the preparation of the compatilizer. The hydrogen bond force exists between the carboxyl groups on the itaconic acid modified linear low-density polyethylene and the hydroxyl groups and amino groups on the hexagonal boron nitride, so that the hexagonal boron nitride has good compatibility in the polyethylene material. The nanometer hexagonal boron nitride sheet layer has very high strength and modulus, and is uniformly dispersed in the polyethylene matrix, which can play a supporting role similar to a “skeleton” to limit the movement of polymer chain segments, thereby improving the elastic modulus and tensile strength of the composite material. When the material is impacted, the uniformly dispersed nanometer hexagonal boron nitride sheet layer can initiate a silver streak and deflect the crack path, effectively absorbing and dispersing impact energy, thereby possibly improving the compressive strength. The nanometer hexagonal boron nitride also has certain barrier properties, can block oxygen, moisture and the like in the external environment from entering the inside of the pipe, and can improve the aging resistance and corrosion resistance of the core pipe.

[0024] In some embodiments, the mass ratio of the itaconic acid and the linear low-density polyethylene is (0.05-0.15): 1.

[0025] In some embodiments, the mass ratio of the modified hexagonal boron nitride and the linear low-density polyethylene in step A2 is (0.04-0.08): 1.

[0026] In some embodiments, the antioxidant is composed of a primary antioxidant and a secondary antioxidant, the primary antioxidant is one or more of 1010, antioxidant 1076, antioxidant 330; the secondary antioxidant is antioxidant 168 or antioxidant 626.

[0027] In some embodiments, the fiber belt is one or more of a glass fiber belt pre-impregnated with polyethylene resin, a carbon fiber belt pre-impregnated with polyethylene resin, an aramid fiber belt pre-impregnated with polyethylene resin.

[0028] In some embodiments, the inner polyethylene pipe has a thickness of 6-20 mm, the fiber reinforced layer has a thickness of 0.6-9 mm, and the outer polyethylene protective layer has a thickness of 6-20 mm.

[0029] In some embodiments, the core pipe mold comprises a straight pipe section, a transition section, and a socket end; the transition section has a slope structure with a slope angle of 2-7°; and the length of the transition section is 500-1500 mm.

[0030] The present application can ensure that the socket is first shaped and then shrunk and demolded, and can make the fiber well adhere to the pipe body, thereby solving the adhesion problems between the multiple layers of the fiber reinforced layer and between the fiber reinforced layer and the inner layer and the protective layer, and making the various parts of the pipe maintain the same structural strength.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] (1) The present application realizes all production processes of multi-layer compounding through one station, and solves the adhesion problems between the multiple layers of the fiber reinforced layer and between the fiber reinforced layer and the inner layer and the protective layer by providing a groove for embedding resistance wires outside the socket mold, pre-embedding resistance wires on the roller mold, and adopting an internal expansion method for the socket mold part, and then shrinking and demolding after the socket is wound and shaped, and solves the process problem of the fiber reinforced layer in the positive and negative circumferential and axial compounding reinforcement, and realizes the function of circumferential and axial double reinforcement.

[0033] (2) The present application uses itaconic acid modified linear low-density polyethylene to make the prepared compatibilizer contain a large number of carboxyl groups, and the addition of the compatibilizer to the core pipe polyethylene material can enhance the interaction force between the glass fiber and the core pipe, and enhance the adhesion between the fiber reinforced layer and the inner layer and the protective layer, which is beneficial to improving the rigidity and internal pressure bearing performance of the composite pipe.

[0034] (3) The carboxyl groups on the prepared itaconic acid modified linear low-density polyethylene can form hydrogen bond forces with the hydroxyl groups and amino groups on the hexagonal boron nitride, so that the hexagonal boron nitride has good compatibility in the polyethylene material, and the rigidity, compression strength, corrosion resistance, and aging resistance of the polyethylene composite pipe are improved. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 Figure 1 is a structural schematic diagram of a core pipe mold;

[0036] 1, straight pipe section; 2, transition section; 3, bell end.

[0037] Figure 2 Figure 2 is a physical diagram of a continuous fiber winding reinforced polyethylene composite pipe of Example 1;

[0038] ① inner polyethylene pipe; ② fiber reinforced layer; ③ outer polyethylene protective layer; ④ polypropylene layer; ⑤ polyethylene layer. DETAILED DESCRIPTION

[0039] The present application will be described in detail below with reference to specific embodiments. It should be noted that the following examples are examples of the present application and are only used to illustrate the present application, but not to limit the present application. Other combinations and various modifications within the concept of the present application can be made without departing from the spirit or scope of the present application.

[0040] In the following examples and comparative examples, the compounds and related reagents used, except for the compatibilizer, can be purchased from the market, wherein the high-density polyethylene is 041, purchased from Shanghai Petrochemical; the polypropylene material is PPB-M02, purchased from Shanghai Petrochemical; the glass fiber tape of the pre-impregnated polyethylene resin is GE60473-01, purchased from Qingdao Zhongji Chuangying Composite Material Technology Co., Ltd.; the hexagonal boron nitride is BN-1, purchased from Qinghe County Beiyuan Metal Material Co., Ltd.; the maleic anhydride grafted low-density polyethylene is NF358E, purchased from Mitsui Chemical.

[0041] The color of the continuous fiber winding reinforced polyethylene composite pipe can be added with different color master batches for conventional dyeing and adjustment according to actual needs, and is not specially limited. The core pipe polyethylene material, outer layer polyethylene material, polyethylene material, and polypropylene material in the following examples have been colored by conventional methods.

[0042] Preparation Example 1

[0043] The preparation method of the compatibilizer-1 comprises the following steps:

[0044] A1, 60g of hexagonal boron nitride and 6g of KH-550 silane coupling agent are added to 300g of 80wt% ethanol aqueous solution, ultrasonic treatment at 45℃ for 50min, and dried to obtain modified hexagonal boron nitride;

[0045] A2, 100g of itaconic acid, 10g of dicumyl peroxide and 1000g of linear low-density polyethylene are mixed uniformly in a high-speed mixer, 60g of the modified hexagonal boron nitride obtained in step A1 is added and mixed uniformly to obtain a mixture;

[0046] A3, the mixture obtained in step A2 was added into a twin-screw extruder and extruded at 180°C to obtain the compatilizer-1.

[0047] Preparation Example 2

[0048] The preparation method of compatilizer-2 was the same as that of Preparation Example 1, except that the amount of itaconic acid added was 200 g.

[0049] Preparation Example 3

[0050] The preparation method of compatilizer-3 was the same as that of Preparation Example 1, except that the amount of modified hexagonal boron nitride added in step A2 was 100 g.

[0051] Preparation Example 4

[0052] The preparation method of compatilizer-4 included the following steps:

[0053] A1, 100 g of itaconic acid, 10 g of dicumyl peroxide and 1000 g of linear low-density polyethylene were mixed uniformly in a high-speed mixer to obtain a mixture;

[0054] A2, the mixture obtained in step A1 was added into a twin-screw extruder and extruded at 180°C to obtain the compatilizer-1.

[0055] Preparation Example 5

[0056] The preparation method of compatilizer-5 included the following steps:

[0057] A1, 60 g of hexagonal boron nitride and 6 g of KH-550 silane coupling agent were added into 300 g of 80 wt% aqueous ethanol solution, ultrasonicated at 45°C for 50 min, and dried to obtain modified hexagonal boron nitride;

[0058] A2, 1000 g of maleic anhydride grafted low-density polyethylene and 60 g of hexagonal boron nitride obtained in step A1 were mixed uniformly in a high-speed mixer to obtain a mixture;

[0059] A3, the mixture obtained in step A2 was added into a twin-screw extruder and extruded at 180°C to obtain the compatilizer-1.

[0060] Example 1

[0061] Reference to the attached Figure 1 , attached Figure 2 A method for preparing a continuous fiber-wound reinforced polyethylene composite pipe included the following steps:

[0062] S1, the core pipe polyethylene material is added to the core pipe extruder, the heating wire is pre-buried in the socket end 3 of the core pipe mold, the core pipe mold is preheated by gas jet, and the inner layer polyethylene pipe ① with a thickness of 12 mm is obtained by melting extrusion and winding at 190 DEG C; the glass fiber band impregnated with polyethylene resin is wound on the inner layer polyethylene pipe ① through the forward and reverse annular cross winding and axial multi-layer winding composite machine group to form the fiber reinforced layer ② with a thickness of 8 mm; the outer layer polyethylene material is added to the extruder, and the outer polyethylene protective layer ③ with a thickness of 6 mm is formed by extrusion winding and compounding on the surface of the fiber reinforced layer ② to obtain the fiber reinforced polyethylene composite pipe with a three-layer structure of the polyethylene pipe as the inner and outer layers and the fiber reinforced layer ② in the middle;

[0063] S2, the polypropylene material is added to the single-wall corrugated pipe extruder, the polyethylene material is added to the extruder, and the outer reinforced pipe with the inner layer of the polypropylene layer 4 with a thickness of 3 mm and the outer layer of the polyethylene layer 5 with a thickness of 2 mm is obtained by co-extrusion at 210 DEG C;

[0064] S3, the outer reinforced pipe obtained in step S2 is wound on the fiber reinforced polyethylene composite pipe obtained in step S1 to obtain the continuous fiber winding reinforced polyethylene composite pipe.

[0065] The core pipe polyethylene material contains the following raw materials in parts by mass: 75 parts of high-density polyethylene, 4 parts of a compatibilizer-1, 0.3 parts of an antioxidant 1010, and 0.2 parts of an antioxidant 168.

[0066] The core pipe mold comprises a straight pipe section 1, a transition section 2, and a socket end 3; the transition section 2 has a slope structure with a slope angle of 6.46°; and the length of the transition section is 570 mm.

[0067] Figure 2 It is a physical diagram of the continuous fiber winding reinforced polyethylene composite pipe of example 1.

[0068] Example 2

[0069] Reference is made to the accompanying drawings Figure 1 , the accompanying drawings Figure 2 A method for preparing a continuous fiber winding reinforced polyethylene composite pipe, comprising the following steps:

[0070] S1, the core pipe polyethylene material is added to the core pipe extruder, the heating wire is pre-buried in the socket end 3 of the core pipe mold, the core pipe mold is preheated by gas jet, and the inner layer polyethylene pipe ① with a thickness of 12 mm is obtained by melting extrusion and winding at 190 DEG C; the glass fiber band impregnated with polyethylene resin is wound on the inner layer polyethylene pipe ① through the forward and reverse annular cross winding and axial multi-layer winding composite machine group to form the fiber reinforced layer ② with a thickness of 8 mm; the outer layer polyethylene material is added to the extruder, and the outer polyethylene protective layer ③ with a thickness of 6 mm is formed by extrusion winding and compounding on the surface of the fiber reinforced layer ② to obtain the fiber reinforced polyethylene composite pipe with a three-layer structure of the polyethylene pipe as the inner and outer layers and the fiber reinforced layer ② in the middle;

[0071] S2, polypropylene material is added to a single-wall corrugated pipe extruder, and polyethylene material is added to the extruder, and an outer reinforcing pipe with an inner layer of a 3mm-thick polypropylene layer 4 and an outer layer of a 2mm-thick polyethylene layer 5 is co-extruded at 200°C;

[0072] S3, the outer reinforcing pipe obtained in step S2 is wound on the fiber-reinforced polyethylene composite pipe obtained in step S1 to obtain a continuous fiber-wound reinforced polyethylene composite pipe.

[0073] The core pipe polyethylene material contains the following raw materials in parts by mass: 60 parts of high-density polyethylene, 2 parts of compatibilizer-1, 0.06 parts of antioxidant 1010, and 0.04 parts of antioxidant 168.

[0074] The core pipe mold includes a straight pipe section 1, a transition section 2, and a socket end 3. The transition section 2 has a slope structure with a slope angle of 6.46°, and the length of the transition section is 570mm.

[0075] Example 3

[0076] Reference to the accompanying drawings Figure 1 , the accompanying drawings Figure 2 A method for preparing a continuous fiber-wound reinforced polyethylene composite pipe, comprising the following steps:

[0077] S1, core pipe polyethylene material is added to a core pipe extruder, an electric heating wire is embedded at the socket end 3 of the core pipe mold, a gas torch is used to preheat the core pipe mold, and an inner layer polyethylene pipe 1 with a thickness of 12mm is obtained by melting and extruding at 220°C. A glass fiber tape impregnated with polyethylene resin is wound on the inner layer polyethylene pipe 1 by a forward and reverse cross-winding and axial multi-layer winding composite machine group to form a fiber-reinforced layer 2 with a thickness of 8mm. An outer layer polyethylene material is added to the extruder, and an outer polyethylene protective layer 3 with a thickness of 6mm is obtained by extruding and winding on the surface of the fiber-reinforced layer 2 to obtain a fiber-reinforced polyethylene composite pipe with a three-layer structure of inner and outer polyethylene pipes and a fiber-reinforced layer 2 in between;

[0078] S2, polypropylene material is added to a single-wall corrugated pipe extruder, and polyethylene material is added to the extruder, and an outer reinforcing pipe with an inner layer of a 3mm-thick polypropylene layer 4 and an outer layer of a 2mm-thick polyethylene layer 5 is co-extruded at 220°C;

[0079] S3, the outer reinforcing pipe obtained in step S2 is wound on the fiber-reinforced polyethylene composite pipe obtained in step S1 to obtain a continuous fiber-wound reinforced polyethylene composite pipe.

[0080] The core pipe polyethylene material contains the following raw materials in parts by mass: 60 parts of high-density polyethylene, 2 parts of compatibilizer-1, 0.06 parts of antioxidant 1010, and 0.04 parts of antioxidant 168.

[0081] The core pipe mold comprises a straight pipe section 1, a transition section 2 and a socket end 3; the transition section 2 is in a slope structure, and the slope angle is 6.46°; the length of the transition section is 570 mm.

[0082] Example 4

[0083] A preparation method of a continuous fiber winding reinforced polyethylene composite pipe, the specific implementation manner is the same as that of example 1, and the difference lies in that the compatibilizer-1 is replaced by the compatibilizer-2 in equal amount.

[0084] Example 5

[0085] A preparation method of a continuous fiber winding reinforced polyethylene composite pipe, the specific implementation manner is the same as that of example 1, and the difference lies in that the compatibilizer-1 is replaced by the compatibilizer-3 in equal amount.

[0086] Example 6

[0087] A preparation method of a continuous fiber winding reinforced polyethylene composite pipe, the specific implementation manner is the same as that of example 1, and the difference lies in that the compatibilizer-1 is replaced by the compatibilizer-4 in equal amount.

[0088] Example 7

[0089] A preparation method of a continuous fiber winding reinforced polyethylene composite pipe, the specific implementation manner is the same as that of example 1, and the difference lies in that the compatibilizer-1 is replaced by the compatibilizer-5 in equal amount.

[0090] Performance test

[0091] The fiber reinforced polyethylene composite pipe obtained from each example is cut into a test sample with a length of 200 mm and a width of 25 mm, and tensile strength test and glass fiber tape welding strength test are performed. The continuous fiber winding reinforced polyethylene composite pipe is subjected to hydrostatic test. The test method is shown in Table 1:

[0092] Table 1

[0093]

[0094] The test results are shown in Table 2:

[0095] Table 2

[0096]

[0097] From the data in Table 2, it can be seen that the continuous fiber wound reinforced polyethylene composite pipe prepared in Examples 1-3 has good mechanical properties and compressive strength and high interlayer adhesion strength. It can be seen from the comparison between Example 4 and Example 1 that changing the ratio of itaconic acid and linear low density polyethylene can cause self-polymerization of itaconic acid, resulting in a decrease in the grafting rate of itaconic acid on the polyethylene segment, thereby reducing the mechanical properties, interlayer adhesion strength and compressive properties of the polyethylene composite pipe. It can be seen from the comparison between Example 5 and Example 1 that changing the ratio of modified hexagonal boron nitride and linear low density polyethylene can cause the modified hexagonal boron nitride to agglomerate, and the active carboxyl groups on the compatibilizer to decrease, thereby reducing the mechanical properties, interlayer adhesion strength and compressive properties of the polyethylene composite pipe. It can be seen from the comparison between Example 6 and Example 1 that when the compatibilizer does not contain modified hexagonal boron nitride, the mechanical properties and compressive strength decrease. It can be seen from the comparison between Example 7 and Example 1 that when the itaconic acid grafted low density polyethylene is replaced by maleic anhydride grafted polyethylene, the mechanical properties, interlayer adhesion strength and compressive properties of the polyethylene composite pipe are poorer.

[0098] The above embodiments are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application should be covered within the protection scope of the present application.

Claims

1. A method for preparing a continuous fiber-wound reinforced polyethylene composite pipe, characterized in that, Includes the following steps: S1. Add the core polyethylene material to the core tube extruder, pre-embed an electric heating wire at the socket end of the core tube die, preheat the core tube die with gas flame, and melt and extrude at 170-220℃ to obtain the inner layer polyethylene tube. Wrap the fiber tape on the inner layer polyethylene tube through a forward and reverse circumferential cross-winding and axial multi-layer winding composite unit to form a fiber reinforcement layer. Add the outer layer polyethylene material to the extruder, and extrude and wind composite on the surface of the fiber reinforcement layer to form an outer polyethylene protective layer, resulting in a three-layer fiber-reinforced polyethylene composite pipe with inner and outer polyethylene tubes and a fiber reinforcement layer in the middle. S2. Add polypropylene material to a single-wall corrugated pipe extruder, add polyethylene material to the extruder, and co-extrude at 200-220℃ to obtain an outer reinforced pipe with a polypropylene inner layer and a polyethylene outer layer. S3. The outer reinforcing tube obtained in step S2 is wound around the fiber-reinforced polyethylene composite tube obtained in step S1 to obtain a continuous fiber-wound reinforced polyethylene composite tube. The core tube polyethylene material, by weight, contains the following raw materials: 60-90 parts high-density polyethylene, 2-6 parts compatibilizer, and 0.1-1 parts antioxidant. The method for preparing the compatibilizer includes the following steps: A1. Add hexagonal boron nitride and KH-550 silane coupling agent to an ethanol aqueous solution, sonicate at 40-50℃ for 40-60 min, and dry to obtain modified hexagonal boron nitride. A2. Mix itaconic acid, dicumyl peroxide and linear low-density polyethylene evenly in a high-speed mixer, add the modified hexagonal boron nitride and sodium hypophosphite obtained in step A1, mix evenly to obtain a mixture; A3. Add the mixture obtained in step A2 to a twin-screw extruder and extrude it at 170-190℃ to obtain the final product. The mass ratio of the hexagonal boron nitride to the KH-550 silane coupling agent is 1:(0.05-0.15). The mass ratio of itaconic acid to linear low-density polyethylene is (0.05-0.15):1; The mass ratio of modified hexagonal boron nitride to linear low-density polyethylene in step A2 is (0.04-0.08):

1.

2. The method for preparing a continuous fiber-wound reinforced polyethylene composite pipe according to claim 1, characterized in that, The fiber tape is one or more of the following: glass fiber tape pre-impregnated with polyethylene resin, carbon fiber tape pre-impregnated with polyethylene resin, and aramid fiber tape pre-impregnated with polyethylene resin.

3. The method for preparing a continuous fiber-wound reinforced polyethylene composite pipe according to claim 1, characterized in that, The inner polyethylene tube has a thickness of 6-20 mm, the fiber reinforcement layer has a thickness of 0.6-9 mm, and the outer polyethylene protective layer has a thickness of 6-20 mm.

4. The method for preparing a continuous fiber-wound reinforced polyethylene composite pipe according to claim 1, characterized in that, The core tube mold includes a straight tube section, a transition section, and a socket end; the transition section has a sloping structure with a slope angle of 2-7°; the length of the transition section is 500-1500mm.

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