High-temperature-resistant polyamide composite reinforced pipe and preparation method thereof

Abstract

The application discloses a kind of high-temperature-resistant polyamide composite reinforced pipes and preparation method thereof, wherein, a kind of high-temperature-resistant polyamide composite reinforced pipe includes from inside to outside: inner liner, including PVDF formed inner tube and PA / PVDF composite material formed outer tube;Reinforced layer, by pre-impregnated tape winding on the outer surface of inner liner constitutes, the pre-impregnated tape uses continuous reinforced fiber pre-impregnated MAH / PA composite material and is formed;Outer coating, its material is thermoplastic material, is coated in the outer surface of reinforced layer;The PA / PVDF composite material is PA and PVDF mixed material grafted with sulfonic acid base;The MAH / PA composite material is POE-g-MAH and PA mixed material.The application effectively improves the bonding strength between PVDF layer in inner liner and reinforced layer, avoids the case that high-temperature-resistant polyamide composite reinforced pipe appears interlayer peeling.

Description

Technical Field

[0001] This invention relates to the field of composite reinforced pipe technology, specifically to a high-temperature resistant polyamide composite reinforced pipe and its preparation method. Background Technology

[0002] The application conditions of composite reinforced pipes have gradually shifted from low-temperature conditions below 60℃ to higher-temperature conditions (up to around 140℃). However, the conventionally used polyethylene (PE) material, currently the mainstream material, has a long-term operating temperature not exceeding 65℃, making it difficult to meet the requirements. While polyvinylidene fluoride (PVDF) can withstand temperatures above 120℃, its material cost is high. Polyamide (PA) can typically be used in conditions above 80℃, but due to the presence of polar amide bonds in its molecular chain, its resistance to high-temperature water is weak, making it prone to hydrolysis and material failure.

[0003] To address the issue that current polyamide-reinforced pipes are difficult to withstand the erosion of high-temperature water, a structure is provided in which PVDF is added as a barrier layer to the inner lining of a composite pipe to improve its resistance to high-temperature hydrolysis. However, the PVDF added to the inner lining can cause interlayer delamination between the PVDF and other plastic layers when the pressure changes rapidly. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is that the PVDF added to the inner lining layer can cause interlayer delamination when the pressure changes rapidly with other plastic layers, thereby providing a high-temperature resistant polyamide composite reinforced pipe and its preparation method to solve the above problem.

[0005] A high-temperature resistant polyamide composite reinforced pipe, comprising, from the inside out:

[0006] The inner lining consists of a PVDF-molded inner tube and a PA / PVDF composite material-molded outer tube.

[0007] The reinforcing layer is formed by winding a continuous fiber prepreg tape around the outer surface of the inner liner layer. The continuous fiber prepreg tape is made of continuous reinforcing fiber prepreg MAH / PA composite material.

[0008] The outer cladding layer, made of thermoplastic material, is wrapped around the outer surface of the reinforcing layer;

[0009] The PA / PVDF composite material is a mixture of PA and PVDF grafted with sulfonic acid groups;

[0010] In a preferred embodiment, the raw materials of the sulfonic acid-grafted PA and PVDF mixture include PA, PVDF, sulfonic acid-grafted monomers, stabilizers, peroxide initiators, and azo initiators;

[0011] The mass ratio of PA to PVDF is 60-75:40-25; based on the total amount of PA and PVDF, the amount of sulfonic acid grafted monomer added is 15-25 wt%, the amount of peroxide initiator added is 1-3 wt%, the amount of azo initiator added is 1-2 wt%, and the amount of stabilizer added is 0.5-1.5 wt%.

[0012] Alternatively, peroxide initiators and azo initiators can be compounded in a weight ratio of (1-3):1.

[0013] For example, the mass ratio of PA to PVDF can be 60:40, 65:35, 70:30, 75:25, etc.; the amount of sulfonic acid grafted monomer added can be 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, etc.; the amount of peroxide initiator added can be 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, etc.; the amount of azo initiator added can be 1wt%, 1.5wt%, 2wt%, etc.; the amount of stabilizer added can be 0.5wt%, 1wt%, 1.5wt%, etc.; and the weight ratio of peroxide initiator to azo initiator can be 1:1, 2:1, 3:1, etc.

[0014] In a preferred embodiment, the MAH / PA composite material comprises a material formed by granulation after mixing POE-g-MAH and PA and extruding at 180-220°C, wherein the mass percentage of POE-g-MAH in the MAH / PA composite material is 3-8%, preferably 4-6%.

[0015] For example, the extrusion temperature can be 180℃, 190℃, 200℃, 210℃, 220℃, etc., and the mass percentage of POE-g-MAH in MAH / PA composite materials can be 3%, 4%, 5%, 6%, 7%, 8%, etc.

[0016] The MAH / PA composite material is a mixture of POE-g-MAH and PA. POE-g-MAH is maleic anhydride-grafted POE, a functionalized material in which maleic anhydride groups are introduced onto the molecular chain of POE (polyolefin elastomer) through a chemical reaction.

[0017] The preparation process of this PA / PVDF composite material is as follows:

[0018] S1. Weigh PVDF and PA, add sulfonic acid grafted monomers, stabilizers, peroxide initiators and azo initiators, and premix them in a high-speed mixer to obtain a mixture.

[0019] S2. Add the mixture to the twin-screw extruder and set the temperature gradient as follows: feeding section 170-280 ℃, low temperature grafting zone 180-300 ℃, high temperature grafting zone 210-350 ℃, die head temperature (discharge section) 190-300 ℃, and extrude the melt.

[0020] S3. The melt is cooled and pelletized by water, and then dried to obtain PA / PVDF composite material.

[0021] For example, the temperature of the feeding section can be 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, etc.; the temperature of the low-temperature grafting zone can be 180℃, 190℃, 200℃, 210℃, 220℃, etc.; the temperature of the high-temperature grafting zone can be 180℃, 190℃, 200℃, 210℃, 220℃, etc.; and the temperature of the discharge section can be 180℃, 190℃, 200℃, 210℃, 220℃, etc.

[0022] In one optional embodiment, during the preparation process of the PA / PVDF composite material:

[0023] In step S1, the high-speed mixer premixes for 5-8 minutes, for example, the premixing time can be 5 minutes, 6 minutes, 7 minutes, 8 minutes, etc.

[0024] In step S2, the screw speed of the extrusion is 30-40 rpm, and the mixture is melt-blended in the twin-screw extruder for 5-10 minutes. For example, the screw speed can be 30 rpm, 32 rpm, 34 rpm, 36 rpm, 38 rpm, 40 rpm, etc., and the blending time can be 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, etc.

[0025] In step S3, the drying method is vacuum drying at 80 ℃ for 4-8 hours. For example, the drying time can be 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc.

[0026] In one optional embodiment, the weight-average molecular weight of PVDF is 200,000. 400000; The polyamide matrix resin is any one or more of PA6, PA66, PA46, PA56, PA612, PA610, PA1010, PA12, PA1212, PA1012, PA11, PA510, PA512, PA6T, PA5T, PA9T, PA10T, PA11T, PA12T, PA6I, MXD6, MXD10, PPTA, and aramid 1313;

[0027] The sulfonic acid grafting monomer is selected from one or a mixture of sodium methacrylate sulfonate (MAS), sodium acrylate sulfonate (AAS), sodium ethylene sulfonate (VES);

[0028] The stabilizer is urea, which is used to absorb the acidic byproducts produced during the grafting reaction;

[0029] Peroxide initiators are high-temperature initiators, including at least one of dicumyl peroxide (DCP), di-tert-butyl peroxide (DTBP), and benzoyl peroxide (BPO);

[0030] Azo initiators are low-temperature initiators, including at least one of dimethyl azobisisobutyrate (AIBME) and azobisisobutyronitrile (AIBN).

[0031] In a preferred embodiment, the thickness of the inner tube is 10%-20% of the total thickness of the inner lining, preferably 13%-17%; for example, the thickness of the inner tube can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% of the total thickness of the inner lining.

[0032] In a preferred embodiment, the material of the continuous reinforcing fiber includes any one or more of glass fiber, carbon fiber, polyester fiber, aramid fiber, polyimide fiber, basalt fiber, steel cord, and steel wire.

[0033] In a preferred embodiment, the continuous fiber prepreg tapes of adjacent layers are wound by a spiral cross-winding process, with the winding directions being opposite along the same axis.

[0034] Furthermore, the winding angle of the continuous fiber prepreg tape is 30-55° with respect to the axial direction, and the number of winding layers is 2n layers, where n is a positive integer ≥1; for example, the winding angle of the continuous fiber prepreg tape with respect to the axial direction can be 30°, 35°, 40°, 45°, 50°, 55°, etc., and n can be 1, 2, 3, 4, 5, 6, 7, 8, etc.

[0035] Furthermore, the winding angle of the continuous fiber prepreg tape is 40-50° with the axial direction.

[0036] In a preferred embodiment, the thermoplastic material includes any one or more of polyetheretherketone (PEEK), polyvinylidene fluoride (PVDF), polyamide (PA), polyethylene (PE), and polypropylene (PP).

[0037] The preparation method of the above-mentioned high-temperature resistant polyamide composite reinforced tube includes:

[0038] The inner liner is made by co-extruding two layers of PVDF and PA / PVDF composite materials in a single extrusion process after a first heat treatment.

[0039] A continuous fiber prepreg tape is wound around the outer surface of the inner lining layer and then subjected to a second heat treatment to form a reinforcing layer;

[0040] Thermoplastic material is extruded and coated onto the outer layer of the reinforcing layer, followed by a third heat treatment to form a finished product that simultaneously has an inner liner, a reinforcing layer, and an outer coating.

[0041] In this invention, the diameter of the high-temperature resistant polyamide composite reinforced pipe is adjusted based on application requirements, and the thickness of each layer is adjusted based on the pressure requirements of the application environment. The design of this invention can be applied to composite reinforced pipes of any specification. Therefore, the thickness and diameter of the composite reinforced pipe will not be described again in this invention.

[0042] In a preferred embodiment, the temperature of the first heat treatment is 190-260℃, for example, the temperature of the first heat treatment can be 190℃, 195℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, etc.

[0043] The temperature of the second heat treatment is 190-200℃, for example, the temperature of the second heat treatment can be 190℃, 192℃, 194℃, 196℃, 198℃, 200℃, etc.

[0044] The temperature of the third heat treatment is 200-210℃, for example, the temperature of the third heat treatment can be 200℃, 202℃, 204℃, 206℃, 208℃, 210℃, etc.

[0045] As is known to those skilled in the art, the heat treatment time during extrusion needs to be adjusted according to the extrusion rate and the treatment temperature. Generally, any parameter conditions that enable the interaction between the two layers to achieve bonding are acceptable and cannot be specifically limited. Therefore, the extrusion rate and treatment time will not be elaborated in this invention. It is sufficient to ensure that the layers can bond together into an integral structure after the first heat treatment and one-time extrusion.

[0046] The technical solution of this invention has the following advantages:

[0047] 1. The introduction of the PVDF layer in the inner lining of the high-temperature resistant polyamide composite reinforced pipe of the present invention improves the gas barrier capability of the pipe compared with the original PE and PA matrix. Furthermore, by using a specific PA / PVDF composite material as the outer pipe and the MAH / PA composite material pre-impregnated in the reinforcement layer, the bonding strength between the PVDF layer in the inner lining and the reinforcement layer can be effectively improved, avoiding interlayer delamination in the high-temperature resistant polyamide composite reinforced pipe, with significant effects.

[0048] 2. In this invention, the thickness of the inner tube is 10%-20% of the total thickness of the inner lining layer, preferably 13%-17%. This thickness not only ensures that the inner wall of the high-temperature resistant polyamide composite reinforced tube can withstand the erosion of high-temperature water, but also significantly reduces the cost of raw materials due to the small thickness of the PVDF layer. Attached Figure Description

[0049] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0050] Figure 1 This is a structural diagram of the high-temperature resistant polyamide composite reinforced tube prepared in Example 1 of the present invention;

[0051] Figure label:

[0052] 11-Inner tube, 12-Outer tube;

[0053] 21 - First enhancement layer;

[0054] 22 - Second reinforcement layer;

[0055] 3-Outer cladding. Detailed Implementation

[0056] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0057] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0058] PA12: Wanhua Chemical Group Co., Ltd., Wanamid;

[0059] PA11: Produced by Arkema (Shanghai) Chemical Co., Ltd., AESNO;

[0060] PA1012: Produced by Shandong Xianglong New Material Co., Ltd., A170;

[0061] PE: Wanhua Chemical Group Co., Ltd., 4731B.

[0062] Example 1

[0063] A high-temperature resistant polyamide composite reinforced pipe, such as Figure 1 As shown, it includes an inner lining layer, a reinforcing layer, and an outer cladding layer.

[0064] In this embodiment, the inner liner is produced by a one-time extrusion using a two-layer co-extrusion device. The inner liner includes an inner tube 11 composed of a PVDF layer and an outer tube 12 composed of PA / PVDF composite material. The inner tube 11 and the outer tube 12 are extruded at a temperature of 190°C using a two-layer co-extrusion method and then bonded together using their own materials to form the inner liner. After extrusion, the thickness of the inner tube 11 is 15% of the total thickness of the inner liner.

[0065] Since oil and gas pipelines typically contain mixtures of oil, water, and gas, and these fluids are often at high temperatures, and pure PA materials are susceptible to hydrolysis, the inner lining layer, using PVDF as the inner tube 11, isolates the fluid to provide a waterless, high-temperature operating environment. The outer tube 12 is made of PA / PVDF composite material, a mixture of sulfonic acid-grafted PA12 and PVDF resin. This material serves two purposes: firstly, it ensures adhesion between the inner tube 11 and the reinforcing layer; secondly, it provides the main material with high-temperature resistance for oil and gas pipeline transportation, up to 105℃ compared to PE materials. This lining design ensures improved pipeline temperature resistance and avoids the risk of reduced lifespan due to material hydrolysis over prolonged use.

[0066] The preparation process of the PA / PVDF composite material is as follows: S1. Weigh the raw materials according to the mass ratio of PVDF:PA12 = 30:70, add 20 wt% MAS (sodium methacrylate), 2 wt% initiator (1 wt% DCP + 1 wt% AIBN), and 1 wt% urea, and premix in a high-speed mixer for 10 minutes; S2. Add the mixture to a twin-screw extruder, set the temperature gradient as follows: feeding section 170℃, low-temperature grafting section 180℃, high-temperature grafting section 210℃, discharge section 190℃, screw speed 50 rpm, and melt-blend for 10 minutes; S3. After water cooling and pelletizing, dry at 80℃ for 24 h to obtain the PA / PVDF composite material. The weight-average molecular weight of PVDF is 200,000.

[0067] In this embodiment, the reinforcing layer material is a continuous glass fiber and MAH / PA composite material. This MAH / PA composite material is a low-viscosity material, providing good dispersion performance during prepreg production. Simultaneously, the MAH / PA composite material undergoes certain modification, specifically by grafting maleic anhydride with POE as the reactive site, forming chemical bonds between PA12 and the glass fibers, thereby preparing PA12-based glass fiber prepreg (hereinafter referred to as prepreg). The glass fibers in the prepreg are continuous, uniform, and parallel, dispersed in the PA12 matrix resin. The preparation process of the MAH / PA composite material is as follows: POE-g-MAH is mixed with PA12, extruded at 190°C, and then granulated. The mass percentage of POE-g-MAH in the MAH / PA composite material is 6%.

[0068] In this embodiment, the reinforcing layer is fabricated through a multi-layer spiral cross-process. The specific preparation process is as follows: the inner lining pipe is circumferentially heated to soften the outer layer of the outer pipe 12, and the matrix resin of the continuous fiber prepreg tape is softened by heating. The inner lining pipe is then wound around the outer pipe 12 at a 45° angle along its axial direction to form the first reinforcing layer 21, which then enters the circumferential heating channel to ensure adhesion between the first reinforcing layer 21 and the outer pipe 12. The second reinforcing layer 22 is disposed adjacent to the first reinforcing layer 21. Except for the reverse winding direction, the other operation processes are identical, with two layers wound in a cycle. The number of winding layers varies according to the design pressure. Each layer needs to pass through an annular heating area to ensure the matrix resin has adhesive force during multi-layer winding. The heating temperature of the reinforcing layer is 190°C.

[0069] In this embodiment, the outer coating layer 3 is made of PA12 to achieve good interlayer adhesion of the pipe. The specific process is to melt and extrude the outer coating material and form it to cover the outer layer of the reinforcing layer. The heating temperature for processing the outer coating layer 3 is 200°C and the heating time is 5 minutes.

[0070] Example 2

[0071] A high-temperature resistant polyamide composite reinforced pipe includes an inner lining, a reinforcing layer, and an outer coating.

[0072] The inner lining layer includes an inner tube 11 made of PVDF layer and an outer tube 12 made of PA / PVDF composite material. The inner tube 11 and the outer tube 12 are extruded and formed at a temperature of 190°C by two-layer co-extrusion and are bonded to each other by their own materials. The thickness of the inner tube 11 is 15% of the total thickness of the inner lining layer. The outer tube 12 is made of a mixed resin of PA11 and PVDF, namely a sulfonic acid-grafted PVDF and PA11 mixed material. The preparation process of the mixed resin of PA11 and PVDF in the inner liner is as follows: S1, Weigh the raw materials according to the mass ratio of PVDF:PA11=40:60, add 20 wt% MAS (sodium methacrylate), 3 wt% initiator (1.5 wt% DCP + 1.5 wt% AIBN), and 1.5 wt% urea, and premix for 8 minutes in a high-speed mixer; S2, Add the mixture to a twin-screw extruder, set the temperature gradient as follows: feeding section 170 ℃, low temperature grafting section 180 ℃, high temperature grafting section 210 ℃, discharge section 190 ℃, screw speed 50 rpm, melt blend for 10 minutes; S3, After the melt is water-cooled and pelletized, it is dried at 80 ℃ for 4 h to obtain the PA / PVDF composite material. The weight-average molecular weight of PVDF is 400,000.

[0073] In this embodiment, the reinforcing layer material is a continuous glass fiber and a MAH / PA composite material. The MAH / PA composite material is prepared by mixing POE-g-MAH with PA11, extruding at 200°C, and then granulating. The mass percentage of POE-g-MAH in the MAH / PA composite material is 5%.

[0074] In this embodiment, the reinforcing layer is fabricated through a multi-layer spiral cross-process. The specific preparation process is as follows: the inner lining pipe is circumferentially heated to soften the outer layer of the outer pipe 12, and the matrix resin of the continuous fiber prepreg tape is softened by heating. The inner lining pipe is then wound around the outer pipe 12 at a 45° angle along its axial direction to form the first reinforcing layer 21, which then enters the circumferential heating channel to ensure adhesion between the first reinforcing layer 21 and the outer pipe 12. The second reinforcing layer 22 is disposed adjacent to the first reinforcing layer 21. Except for the reverse winding direction, the other operation processes are identical, with two layers wound in a cycle. The number of winding layers varies according to the design pressure. Each layer needs to pass through an annular heating area to ensure the matrix resin has adhesive force during multi-layer winding. The heating temperature of the reinforcing layer is 200°C.

[0075] In this embodiment, the outer coating layer 3 is made of PA11 to achieve good interlayer adhesion of the pipe. The specific process is to melt and extrude the outer coating material and form it to cover the outer layer of the reinforcing layer. The heating temperature for processing the outer coating layer 3 is 210°C and the heating time is 5 minutes.

[0076] Example 3

[0077] A high-temperature resistant polyamide composite reinforced pipe includes an inner lining, a reinforcing layer, and an outer coating.

[0078] The inner liner consists of an inner tube 11 made of PVDF and an outer tube 12 made of PA / PVDF composite material. The inner tube 11 and the outer tube 12 are extruded at 190°C using a two-layer co-extrusion method and bonded together using their own materials. The thickness of the inner tube 11 is 10% of the total thickness of the inner liner. The outer tube 12 is made of a mixed resin of PA1012 and PVDF, i.e., a sulfonic acid-grafted PA1012 and PVDF mixture. The preparation process of this sulfonic acid-grafted PA1012 and PVDF mixture is as follows: S1. Weigh the raw materials according to the mass ratio of PVDF: PA1012 = 30:70, add 25 wt% MAS (sodium methacrylate), 3 wt% initiator (2 wt% DCP + 1 wt% AIBN), and 1 wt% urea, and premix in a high-speed mixer for 5 minutes; S2. Add the mixture to a twin-screw extruder, and set the temperature gradient as follows: feeding section 170°C, low-temperature grafting section 180°C. The PA / PVDF composite material was prepared by melting and blending at 10 minutes with a high-temperature grafting section of 210 °C and a discharge section of 190 °C, and a screw speed of 50 rpm for 10 minutes. S3: After water cooling and pelletizing, the melt was dried at 80 °C for 6 hours to obtain the PA / PVDF composite material. The weight-average molecular weight of PVDF was 300,000.

[0079] In this embodiment, the reinforcing layer material is a continuous glass fiber and MAH / PA composite material. The preparation process of the MAH / PA composite material is as follows: POE-g-MAH and PA1012 are mixed and extruded at 200°C and then granulated. The mass ratio of POE-g-MAH in the MAH / PA composite material is 4%.

[0080] In this embodiment, the reinforcing layer is fabricated through a multi-layer spiral cross-process. The specific preparation process is as follows: the inner lining pipe is circumferentially heated to soften the outer layer of the outer pipe 12, and the matrix resin of the continuous fiber prepreg tape is softened by heating. The inner lining pipe is then wound around the outer pipe 12 at a 55° angle along its axial direction to form the first reinforcing layer 21, which then enters the circumferential heating channel to ensure adhesion between the first reinforcing layer 21 and the outer pipe 12. The second reinforcing layer 22 is disposed adjacent to the first reinforcing layer 21. Except for the reverse winding direction, the other operation processes are identical, with two layers wound in a cycle. The number of winding layers varies according to the design pressure. Each layer needs to pass through an annular heating area to ensure the matrix resin has adhesive strength during multi-layer winding. The heating temperature of the reinforcing layer is 200°C.

[0081] In this embodiment, the outer coating layer 3 is made of PA1012 to achieve good interlayer adhesion of the pipe. The specific process is to melt and extrude the outer coating material and form it to cover the outer layer of the reinforcing layer. The heating temperature for processing the outer coating layer 3 is 210°C and the heating time is 5 minutes.

[0082] Example 4

[0083] A high-temperature resistant polyamide composite reinforced pipe includes an inner lining, a reinforcing layer, and an outer coating.

[0084] The inner lining layer includes an inner tube 11 made of PVDF layer and an outer tube 12 made of PA / PVDF composite material. The inner tube 11 and the outer tube 12 are extruded at 190°C by co-extrusion and bonded together by their own materials. The thickness of the inner tube 11 is 20% of the total thickness of the inner lining layer. The outer tube 12 is made of a mixed resin of PA12 and PVDF, namely a sulfonic acid-grafted PA12 and PVDF mixture. The preparation process of this sulfonic acid-grafted PA12 and PVDF mixture is as follows: S1. Weigh the raw materials according to the mass ratio of PVDF:PA12=25:75, add 20 wt% MAS (sodium methacrylate), 2 wt% initiator (1 wt% DCP + 1 wt% AIBN), and 0.5 wt% urea, and premix for 5 minutes in a high-speed mixer; S2. Add the mixture to a twin-screw extruder, set the temperature gradient as follows: feeding section 170 ℃, low temperature grafting section 180 ℃, high temperature grafting section 210 ℃, discharge section 190 ℃, screw speed 50 rpm, and melt-blend for 10 minutes; S3. After water cooling and pelletizing, dry at 80 ℃ for 8 h to obtain the PA / PVDF composite material.

[0085] In this embodiment, the reinforcing layer material is a continuous glass fiber and MAH / PA composite material. The preparation process of the MAH / PA composite material is as follows: POE-g-MAH and PA12 are mixed, extruded at 200°C, and then granulated to form the composite material. The mass percentage of POE-g-MAH in the MAH / PA composite material is 6%.

[0086] In this embodiment, the reinforcing layer is fabricated through a multi-layer spiral cross-process. The specific preparation process is as follows: the inner lining pipe is circumferentially heated to soften the outer layer of the outer pipe 12, and the matrix resin of the continuous fiber prepreg tape is softened by heating. The inner lining pipe is then wound around the outer pipe 12 at a 30° angle along its axial direction to form the first reinforcing layer 21, which then enters the circumferential heating channel to ensure adhesion between the first reinforcing layer 21 and the outer pipe 12. The second reinforcing layer 22 is disposed adjacent to the first reinforcing layer 21. Except for the reverse winding direction, the other operation processes are identical, with two layers wound in a cycle. The number of winding layers varies according to the design pressure. Each winding layer needs to pass through an annular heating area to ensure the matrix resin has adhesive force during multi-layer winding. The heating temperature of the reinforcing layer is 200°C.

[0087] In this embodiment, the outer coating layer 3 is made of PE. The specific process involves melting and extruding the outer coating material and molding it to cover the outer layer of the reinforcing layer. The heating temperature for processing the outer coating layer 3 is 210°C, and the heating time is 5 minutes.

[0088] Example 5

[0089] The difference from Example 1 lies in the fact that the PA / PVDF composite material and the MAH / PA composite material are different, as detailed below:

[0090] The preparation process of PA / PVDF composite material is as follows: S1. Weigh the raw materials according to the mass ratio of PVDF: PA12 = 40:60, add 25% sodium propylene sulfonate (AAS), 5% initiator (3% DTBP + 2% AIBME), and 1.5% urea, and premix in a high-speed mixer for 10 minutes; S2. Add the mixture to a twin-screw extruder, set the temperature gradient as follows: feeding section 200 ℃, low-temperature grafting section 240 ℃, high-temperature grafting section 280 ℃, discharge section 240 ℃, screw speed 40 rpm, and melt-blend for 8 minutes; S3. After water cooling and pelletizing, dry at 80 ℃ for 8 h to obtain PA / PVDF composite material.

[0091] The preparation process of MAH / PA composite material is to mix POE-g-MAH with PA12, extrude at 220℃ and then granulate to form the composite material. The mass ratio of POE-g-MAH in MAH / PA composite material is 8%.

[0092] Example 6

[0093] The difference from Example 1 lies in the fact that the PA / PVDF composite material and the MAH / PA composite material are different, as detailed below:

[0094] The preparation process of PA / PVDF composite material is as follows: S1. Weigh the raw materials according to the mass ratio of PVDF: PA12 = 25: 75, add 15% sodium ethylene sulfonate (VES), 2% initiator (1% BPO + 1% AIBN), and 0.5% urea, and premix in a high-speed mixer for 10 minutes; S2. Add the mixture to a twin-screw extruder, set the temperature gradient as follows: feeding section 280 ℃, low-temperature grafting section 300 ℃, high-temperature grafting section 350 ℃, discharge section 300 ℃, screw speed 30 rpm, and melt-blend for 5 minutes; S3. After water cooling and pelletizing, dry at 80 ℃ for 4 h to obtain PA / PVDF composite material.

[0095] The preparation process of MAH / PA composite material is to mix POE-g-MAH with PA12, extrude at 180℃ and then granulate to form the composite material. The mass ratio of POE-g-MAH in MAH / PA composite material is 3%.

[0096] Comparative Example 1

[0097] The difference from Example 1 is that the PA / PVDF composite material and the MAH / PA composite material in this comparative example are different, while the other conditions are the same as in Example 1.

[0098] S1. Weigh the raw materials according to the mass ratio of PVDF:PA12 = 25:75, and premix them in a high-speed mixer for 10 minutes; S2. Add the mixture to a twin-screw extruder, set the temperature gradient as follows: feeding section 170 ℃, low-temperature grafting section 180 ℃, high-temperature grafting section 210 ℃, discharge section 190 ℃, screw speed 50 rpm, and melt-blend for 5-10 minutes; S3. After water cooling and pelletizing, dry the melt at 80 ℃ for 24 h to obtain PA / PVDF composite material.

[0099] The MAH / PA composite material was replaced with PA12.

[0100] Comparative Example 2

[0101] The difference from Example 1 is that the PA / PVDF composite material is different in this comparative example, while the other conditions are the same as in Example 1.

[0102] S1. Weigh the raw materials according to the mass ratio of PVDF:PA12 = 25:75, and premix them in a high-speed mixer for 10 minutes; S2. Add the mixture to a twin-screw extruder, set the temperature gradient as follows: feeding section 170 ℃, low-temperature grafting section 180 ℃, high-temperature grafting section 210 ℃, discharge section 190 ℃, screw speed 50 rpm, and melt-blend for 5-10 minutes; S3. After water cooling and pelletizing, dry the melt at 80 ℃ for 24 h to obtain PA / PVDF composite material.

[0103] Comparative Example 3

[0104] The difference from Example 1 is that the MAH / PA composite material in this comparative example is different. In this comparative example, the MAH / PA composite material is replaced with PA12, and the other conditions are the same as in Example 1.

[0105] Comparative Example 4

[0106] The difference from Example 1 lies in the preparation of the sulfonic acid-grafted PVDF and PA11 composite material. Specifically, the preparation process of the PA11 and PVDF composite resin is as follows: S1. Weigh the raw materials according to the mass ratio of PVDF:PA11 = 40:60, add 20 wt% MAS (sodium methacrylate), 3 wt% initiator (3 wt% DCP), and 1.5 wt% urea, and premix in a high-speed mixer for 8 minutes; S2. Add the mixture to a twin-screw extruder, set the temperature gradient as follows: feeding section 170 ℃, low-temperature grafting section 180 ℃, high-temperature grafting section 210 ℃, discharge section 190 ℃, screw speed 50 rpm, and melt-blend for 10 minutes; S3. After water cooling and pelletizing, dry at 80 ℃ for 4 h to obtain the PA / PVDF composite material. The weight-average molecular weight of PVDF is 400,000.

[0107] Comparative Example 5

[0108] The difference from Example 1 lies in the preparation of the sulfonic acid-grafted PVDF and PA11 mixture. Specifically, the preparation process of the PA11 and PVDF mixture resin is as follows: S1. Weigh the raw materials according to the mass ratio of PVDF:PA11 = 40:60, add 20 wt% MAS (sodium methacrylate), 3 wt% initiator (3 wt% AIBN), and 1.5 wt% urea, and premix in a high-speed mixer for 8 minutes; S2. Add the mixture to a twin-screw extruder, set the temperature gradient as follows: feeding section 170 ℃, low-temperature grafting section 180 ℃, high-temperature grafting section 210 ℃, discharge section 190 ℃, screw speed 50 rpm, and melt-blend for 10 minutes; S3. After water cooling and pelletizing, dry at 80 ℃ for 4 h to obtain the PA / PVDF composite material. The weight-average molecular weight of PVDF is 400,000.

[0109] Experimental Example 1 - Verification of the peel strength of the PVDF-molded inner tube and the PA / PVDF composite material-molded outer tube in the lining layer.

[0110] The specific operating steps are as follows: Cut the high-temperature resistant polyamide composite reinforced tube into a standard size of 25 mm × 150 mm, and fix it on the peel tester to test the peel strength.

[0111] The test results are shown in Table 1 below.

[0112] Table 1. Test results of peel strength

[0113]

[0114] By comparing the peel strength data of the high-temperature resistant polyamide composite reinforced pipes in the above embodiments and comparative examples, it can be seen that the introduction of the PVDF layer in the inner lining of the high-temperature resistant polyamide composite reinforced pipe of the present invention, the use of a specific PA / PVDF composite material as the outer pipe, and the use of the pre-impregnated MAH / PA composite material in the reinforcing layer can effectively improve the bonding strength between the PVDF layer and the reinforcing layer in the inner lining, and effectively avoid interlayer peeling in the high-temperature resistant polyamide composite reinforced pipe.

[0115] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A high temperature resistant polyamide composite reinforced tube, characterized in that, From inside to outside, it includes: The inner lining consists of a PVDF-molded inner tube and a PA / PVDF composite material-molded outer tube. The reinforcing layer is formed by winding a continuous fiber prepreg tape around the outer surface of the inner liner layer. The continuous fiber prepreg tape is made of continuous reinforcing fiber prepreg MAH / PA composite material. The outer cladding layer, made of thermoplastic material, is wrapped around the outer surface of the reinforcing layer; The PA / PVDF composite material is a mixture of PA and PVDF grafted with sulfonic acid groups, and the initiator of the mixture of PA and PVDF grafted with sulfonic acid groups is a peroxide initiator and an azo initiator. The MAH / PA composite material is a mixture of POE-g-MAH and PA.

2. The high-temperature resistant polyamide composite reinforced pipe according to claim 1, characterized in that, The raw materials for the sulfonic acid-grafted PA and PVDF mixture include PA, PVDF, sulfonic acid-grafted monomers, stabilizers, peroxide initiators, and azo initiators; wherein the mass ratio of PA to PVDF is (60-75):(40-25); based on the total amount of PA and PVDF, the amount of sulfonic acid-grafted monomers added is 15-25 wt%, the amount of peroxide initiators added is 1-3 wt%, the amount of azo initiators added is 1-2 wt%, and the stabilizer is urea, with an amount of 0.5-1.5 wt%. And / or, the POE-g-MAH accounts for 3-8% of the mass of the MAH / PA composite material.

3. The high-temperature resistant polyamide composite reinforced pipe according to claim 2, characterized in that, The peroxide initiator and the azo initiator are compounded in a weight ratio of (1-3):

1.

4. The high-temperature resistant polyamide composite reinforced pipe according to any one of claims 1-3, characterized in that, The thickness of the inner tube is 10%-20% of the total thickness of the inner lining.

5. The high-temperature resistant polyamide composite reinforced pipe according to any one of claims 1-3, characterized in that, The material of the continuous reinforcing fiber includes any one or more of glass fiber, carbon fiber, polyester fiber, aramid fiber, polyimide fiber, basalt fiber, steel cord, and steel wire.

6. The high-temperature resistant polyamide composite reinforced pipe according to any one of claims 1-3, characterized in that, The two adjacent layers of continuous fiber prepreg tape are wound by a spiral cross-winding process, with the winding directions being opposite along the same axis.

7. The high-temperature resistant polyamide composite reinforced pipe according to claim 6, characterized in that, The winding angle of the continuous fiber prepreg tape is 30-55° with respect to the axial direction, and the number of winding layers is 2n layers, where n is a positive integer ≥1.

8. The high-temperature resistant polyamide composite reinforced pipe according to claim 7, characterized in that, The winding angle of the continuous fiber prepreg tape is 40-50° with the axial direction.

9. The high-temperature resistant polyamide composite reinforced pipe according to any one of claims 1-3, characterized in that, The thermoplastic material includes any one or more of polyetheretherketone, polyvinylidene fluoride, polyamide, polyethylene, and polypropylene.

10. A method for preparing a high-temperature resistant polyamide composite reinforced pipe, characterized in that, include: The inner liner is made by two-layer co-extrusion of PVDF and PA / PVDF composite materials, followed by a first heat treatment and one-time extrusion. The temperature of the first heat treatment is 190-260℃. A continuous fiber prepreg tape is wound around the outer surface of the inner lining layer and then subjected to a second heat treatment to form a reinforcing layer. The temperature of the second heat treatment is 190-200℃. Thermoplastic material is extruded and coated onto the outer surface of the reinforcing layer, and then subjected to a third heat treatment to form a finished product that simultaneously has an inner liner, a reinforcing layer, and an outer coating layer. The temperature of the third heat treatment is 200-210℃.

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