A multilayer pipe and a method for manufacturing and using the same

Abstract

This invention belongs to the field of multilayer piping technology, and particularly relates to a multilayer piping system, its preparation method, and its application. The multilayer piping system comprises an outer layer and an inner layer: (I) The outer layer is made of a polyamide / polyolefin alloy material, which includes at least polyamide, polyolefin, and an interlayer adhesive lubricant; wherein the content of the interlayer adhesive lubricant is 0.05–1.0 wt%, the content of the polyolefin is 2–20 wt%, and the content of the polyamide is ≥50 wt%; the polyamide includes at least one long-chain polyamide; the repeating unit of the long-chain polyamide has ≥8 carbon atoms; (II) The inner layer is made of a hydrolysis-resistant polyolefin material, which includes at least copolymer polypropylene, and the content of the copolymer polypropylene is greater than or equal to 50 wt%. The multilayer piping system of this invention has excellent surface gloss, low-temperature impact toughness, and high hydrolysis resistance.

Description

Technical Field

[0001] This invention belongs to the field of multilayer pipeline technology, and particularly relates to a multilayer pipeline, its preparation method and application. Background Technology

[0002] With increasing global awareness of environmental protection and the transformation of energy structures, the new energy vehicle (NEV) industry is developing rapidly at an unprecedented pace. This rapid development is not only reflected in the expansion of market size but also drives technological innovation throughout the entire industry chain. As a core component of automobiles, the design and manufacturing of the vehicle piping system faces unprecedented challenges and opportunities. With the advancement of new energy vehicle technology, the requirements for vehicle piping are also increasing, needing not only to meet basic fluid transmission functions but also to adapt to the unique working environment of new energy vehicles. Currently, traditional automotive rubber hoses such as EPDM are gradually being phased out of the market due to their heavy weight and poor recyclability.

[0003] Polyamide materials play a vital role in the automotive industry due to their excellent mechanical properties, superior chemical resistance, and outstanding abrasion resistance. Long-chain polyamides, such as PA11 and PA12, in particular, are widely used in piping systems for transporting water, gases, chemical solvents, and fuels because of their excellent weather resistance, oil resistance, and high flexibility maintained at low temperatures. However, single-layer long-chain nylon piping suffers from drawbacks such as high cost and insufficient hydrolysis resistance. Therefore, multilayer composite piping technology is currently developing rapidly. For example:

[0004] Patent document CN108343790 A discloses a multi-layer pipeline structure, characterized by an inner layer of ethylene propylene diene monomer (EPDM) rubber, a middle layer of polypropylene-modified EPDM rubber, and an outer layer of modified nylon 12. This pipeline design not only optimizes the wall thickness but also significantly reduces the weight of traditional rubber pipelines. However, the burst pressure of this pipeline is low, and the heat resistance of the rubber material is insufficient.

[0005] Patent document CN 117734240 A discloses a polyamide adhesive layer / polypropylene three-layer composite pipe for use in new energy vehicles. This three-layer composite pipe can be used for straight pipes and corrugated pipes and has excellent mechanical properties and low-temperature toughness. However, it has the problem that the polyamide and polypropylene do not bond together, so an expensive adhesive layer and a more complex extrusion process are required, which affects its production and processing efficiency.

[0006] Therefore, there is a need in this field to develop a new type of multilayer pipeline that can not only meet the requirements of long-term hydrolysis resistance, heat aging resistance and high burst pressure in the field of new energy vehicles, but also has a reliable pipeline structure, simple processing technology and high production efficiency. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a multilayer pipeline, its preparation method, and its application. By optimizing the composition of the outer and inner layers, the multilayer pipeline can achieve interlayer adhesion using only a double-layer extruder, eliminating the need for adhesive layers and enabling efficient bonding between multiple layers. This significantly reduces the requirements for production equipment and improves production efficiency. Furthermore, it can significantly enhance the surface gloss of the multilayer pipeline, reduce die exudation, and provide advantages such as excellent low-temperature impact toughness and high hydrolysis resistance.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] In the first aspect, a multi-layer conduit is provided, comprising an outer layer and an inner layer:

[0010] (I) The outer layer is made of a polyamide / polyolefin alloy material, which includes at least polyamide and an interlayer adhesive lubricant; wherein the interlayer adhesive lubricant has a weight percentage of 0.05~1.0 wt% (e.g., 0.06 wt%, 0.08 wt%, 0.1 wt%, 0.2 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.8 wt%, 0.9 wt%), and the polyamide has a weight percentage of greater than or equal to 50 wt% (e.g., 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%); the polyamide contains at least one long-chain polyamide; and the repeating unit of the long-chain polyamide has ≥8 carbon atoms.

[0011] (II) The inner layer is made of a hydrolysis-resistant polyolefin material, which includes at least a copolymer polypropylene, and the weight percentage of the copolymer polypropylene is greater than or equal to 50 wt% (e.g., 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%).

[0012] In some embodiments of the multilayer piping provided by the present invention, the outer polyamide / polyolefin alloy material comprises the following components in weight percentages:

[0013] Long-chain polyamides, 57~97.85 wt% (e.g., 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%).

[0014] Interlayer bonding lubricant, 0.05~1.0wt% (e.g., 0.06wt%, 0.08wt%, 0.1wt%, 0.2wt%, 0.4wt%, 0.5wt%, 0.8wt%).

[0015] Polyolefins, 2~20wt% (e.g., 3wt%, 5wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt%).

[0016] Plasticizer, 0~20wt% (e.g., 1wt%, 3wt%, 5wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt%).

[0017] Other processing aids, 0.1~2wt% (e.g., 0.15wt%, 0.2wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.8wt%, 1.0wt%, 1.5wt%, 1.8wt%).

[0018] According to the multilayer piping provided by the present invention, in some embodiments, the interlayer bonding lubricant in the polyamide / polyolefin alloy material has a characteristic structure as shown in formula (I):

[0019] , formula (I)

[0020] In the formula: R is a saturated alkyl group having 1-12 carbon atoms (e.g., propyl, butyl, pentyl, hexyl, heptyl, octyl), preferably a branched alkyl group having 1-12 carbon atoms, more preferably selected from one or more combinations of the structures shown in the following formulas R1, R2 or R3;

[0021] Formula R1;

[0022] Equation R2;

[0023] , Formula R3.

[0024] In some embodiments, the relative molecular weight of the interlayer bonding lubricant is less than or equal to 600 (e.g., 80, 100, 120, 150, 200, 220, 250, 300, 350, 400, 450, 480, 500, 550, 580), preferably less than or equal to 500.

[0025] In some embodiments, the interlayer bonding lubricant is selected from one or more of N-(2-isobutoxyphenyl)-N'-(2-isobutylphenyl)-oxalamide, N-(2-(3,4-methylpentoxyphenyl)phenyl)-N'-(2-(3,4-methylpentyl)phenyl)-oxalamide, and N-(2-(5,6-methylheptoxyphenyl)phenyl)-N'-(2-(5,6-methylheptyl)phenyl)-oxalamide. That is, R in the characteristic structure shown in formula (I) corresponds to the compound shown in formula R1 (isobutyl), formula R2 (methylpentyl), or formula R3 (methylheptyl).

[0026] In some embodiments, the long-chain polyamide in the polyamide / polyolefin alloy material is selected from one or more of PA610, PA612, PA1012, PA11, PA12 and PA1212, and its Ubbelohde viscosity is between 1.8 and 2.6 (e.g. 1.9, 2.0, 2.1, 2.2, 2.4, 2.5).

[0027] In some embodiments, the polyolefin in the polyamide / polyolefin alloy material is selected from one or more of polyethylene, copolymer polypropylene, and homopolymer polypropylene, preferably copolymer polypropylene.

[0028] In some embodiments, the plasticizer in the polyamide / polyolefin alloy material is selected from one or more of N-butylbenzenesulfonamide, phthalate and 2-hexyldecyl 4-hydroxybenzoate, preferably N-butylbenzenesulfonamide.

[0029] In some embodiments, the other processing aids in the polyamide / polyolefin alloy material include one or more of antioxidants, lubricants, hydrolysis resistant agents, flame retardants, UV stabilizers, light stabilizers, pigments, masterbatches, and inorganic salts.

[0030] An interlayer bonding lubricant is added to the outer polyamide / polyolefin alloy material. During the extrusion process of multilayer pipelines, the interlayer bonding lubricant migrates to the melt surface due to the interaction between the benzene rings and the molecular weight of the polyamide. On the one hand, the two R groups have strong compatibility with the inner polyolefin material, and the two amide groups have strong compatibility with the outer polyamide material, thus effectively improving the interlayer adhesion. On the other hand, during the extrusion process, a non-polar protective film composed of R groups can be formed on the outer surface in contact with the metal of the extruder die, effectively reducing the adhesion between the polar amide bonds and the metal die, reducing processing friction, and thus significantly improving the surface gloss of the multilayer pipeline while reducing problems such as die exudation.

[0031] In addition, the polyolefin contained in the outer polyamide / polyolefin alloy material can improve the compatibility between the outer and inner materials, and increase the binding molecules between the polyamide crystal regions, thereby effectively improving the low-temperature impact toughness of the multilayer pipeline.

[0032] In some embodiments of the multilayer piping provided by the present invention, the hydrolysis-resistant polyolefin material of the inner layer includes: polypropylene, polyethylene, graft toughening agents, and optional other processing aids.

[0033] In some embodiments, the polypropylene is copolymer polypropylene or a combination of copolymer polypropylene and homopolymer polypropylene.

[0034] In some embodiments, the graft toughening agent is selected from one or more of POE-MAH, POE-GMA, EPDM-MAH, EPDM-GMA, EMA-GMA and EBA-GMA; and its grafting rate is 0.1~0.8%, for example, 0.2%, 0.3%, 0.4%, 0.5% and 0.6%.

[0035] In some embodiments, the graft toughening agent in the hydrolysis-resistant polyolefin material has a weight percentage of 5 to 25 wt% (e.g., 6 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, 24 wt%).

[0036] In some embodiments, the polyethylene content in the hydrolysis-resistant polyolefin material is 1-15 wt% (e.g., 2 wt%, 4 wt%, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%); and the content of other processing aids is 0-5 wt% (e.g., 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.4 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 1.8 wt%, 2.0 wt%, 4.0 wt%).

[0037] The other processing aids in the hydrolysis-resistant polyolefin material include one or more of antioxidants, lubricants, hydrolysis-resistant agents, flame retardants, UV stabilizers, light stabilizers, pigments, masterbatches, and inorganic salts.

[0038] In some embodiments, the hydrolysis-resistant polyolefin material comprises the following components by weight percentage:

[0039] Copolymer polypropylene, 55-90 wt%;

[0040] Polyethylene, 0-15 wt%;

[0041] Graft toughening agent, 5-25 wt%;

[0042] Other processing aids, 0-5 wt%.

[0043] The hydrolysis-resistant polyolefin material used as the inner layer contains ≥50wt% copolymer polypropylene, which provides excellent hydrolysis resistance. At the same time, the grafted toughening agent effectively improves the low-temperature toughness of the inner layer material, solving the problem of poor low-temperature toughness of copolymer polypropylene. Therefore, the hydrolysis-resistant polyolefin material, as the inner layer, provides excellent hydrolysis resistance and fuel erosion resistance for multi-layer pipelines, while effectively reducing the overall cost of multi-layer pipelines.

[0044] According to the multi-layer pipeline provided by the present invention, in some embodiments, the multi-layer pipeline is a corrugated pipe or a smooth pipe, with an outer diameter of 6~55mm (e.g., 8mm, 10mm, 12mm, 15mm, 18mm, 20mm, 25mm, 30mm, 40mm, 50mm), preferably 6~22mm; and a total wall thickness of 1~5mm (e.g., 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm), preferably 1~3mm;

[0045] The outer layer's wall thickness accounts for 20% to 80% of the total wall thickness of the multilayer pipeline (e.g., 25%, 30%, 35%, 45%, 50%, 60%, 65%, 75%), preferably 40% to 70%.

[0046] In a second aspect, a method for preparing the multilayer pipeline as described above is provided, comprising the following steps:

[0047] (1) Preparation of outer layer polyamide / polyolefin alloy material particles

[0048] The raw material components are mixed evenly, and then the resulting mixture is melt-extruded in a twin-screw extruder.

[0049] In some implementations, the twin-screw extruder operates at a speed of 200-500 rpm (e.g., 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm); the extrusion processing temperatures are: 210-230°C in the feeding section, 230-250°C in the plasticizing and homogenizing sections, and 210-230°C in the die head; the vacuum level is -0.01 to -0.08 MPa (e.g., -0.02 MPa, -0.04 MPa, -0.05 MPa, -0.06 MPa); the plasticizer is added via a liquid-side feed loss-in-weight weighing system.

[0050] (2) Preparation of hydrolysis-resistant polyolefin material particles for the inner layer

[0051] The raw material components are mixed evenly, and then the resulting mixture is melt-extruded in a twin-screw extruder.

[0052] In some implementations, the twin-screw extruder operates at a speed of 200-500 rpm (e.g., 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm), with extrusion processing temperatures of 190-200°C in the feeding section, 200-220°C in the plasticizing and homogenizing sections, 190-210°C in the die head, and a vacuum of -0.01 to -0.08 MPa (e.g., -0.02 MPa, -0.04 MPa, -0.05 MPa, -0.06 MPa).

[0053] (3) Multi-layer co-extrusion process

[0054] Using a double-layer extruder, the polyamide / polyolefin alloy material particles and hydrolysis-resistant polyolefin material particles obtained in the above steps are respectively added to the feed ports of the outer extruder and the inner extruder for processing to prepare the multilayer pipeline;

[0055] Preferably, the co-extrusion line speed is 5-30 m / min (e.g., 6 m / min, 10 m / min, 15 m / min, 20 m / min, 25 m / min); the processing temperature of the outer extruder is 240-250℃, and the processing temperature of the inner extruder is 200-220℃.

[0056] In a third aspect, the application of the multilayer pipeline as described above or the multilayer pipeline prepared by the method described above in the fields of pneumatic brake pipelines, cooling pipelines, fuel pipelines, lubricating oil pipelines, and oil-gas pipelines is provided.

[0057] Compared with the prior art, the beneficial effects of the technical solution of the present invention are at least as follows:

[0058] (1) An innovative multi-layer pipeline structure is provided, which can solve the problems of heavy weight and difficulty in recycling of EPDM hoses; at the same time, it can make up for the problems of insufficient hydrolysis resistance of single-layer nylon hoses and low burst pressure and poor low-temperature toughness of single-layer polyolefin hoses; compared with the emerging polyamide / adhesive layer / polypropylene multi-layer pipelines, the multi-layer pipeline of the present invention can achieve efficient bonding between layers without adhesive layer, which greatly reduces the requirements for production equipment and improves production efficiency;

[0059] (2) The innovative introduction of interlayer bonding lubricant into the outer alloy material effectively improves the interlayer bonding force of the multilayer pipeline. At the same time, it can also effectively reduce the bonding force between the polar amide bond and the metal mold during the pipe extrusion process, reduce the processing friction, significantly improve the surface gloss of the multilayer pipeline, and reduce problems such as die precipitation. In addition, the polyolefin contained in the outer polyamide / polyolefin alloy material can effectively improve the low-temperature impact toughness of the multilayer pipeline.

[0060] (3) The inner layer of hydrolysis-resistant polyolefin material contains ≥50wt% copolymer polypropylene, which can provide excellent hydrolysis resistance. At the same time, the grafting toughening agent contained therein can effectively improve the low temperature toughness of the inner layer material, thus solving the problem of poor low temperature toughness of copolymer polypropylene. Detailed Implementation

[0061] To provide a detailed understanding of the technical features and content of this invention, preferred embodiments will be described in more detail below. While preferred embodiments are described in the examples, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply.

[0062] The raw material grades and supplier information used in the preparation examples and embodiments of this invention are as follows:

[0063] Table 1 Raw material grades and supplier information

[0064]

[0065] Preparation of interlayer bonding lubricant

[0066] The preparation process of the compound with R as shown in formula (I) (i.e., N-(2-isobutoxyphenyl)-N'-(2-isobutylphenyl)-oxalamide) is as follows:

[0067] Low-pressure saturated steam (1.0 MPaG) was introduced outside the heat exchange tubes, and liquid dimethyl oxalate began to evaporate under steam heating conditions. The evaporation pressure of dimethyl oxalate was controlled at approximately 0.1 MPaG, and the evaporation temperature at approximately 130°C. The vaporized dimethyl oxalate was then continuously fed into a reactor containing 2-isobutoxybenzene and 2-isobutylbenzene. The initial concentration of each component in the reactor was 1 mol / L. The reaction pressure in the reactor was controlled at approximately 0.1 MPaG, the reaction temperature at approximately 130°C, and the reaction time at approximately 30 min, resulting in a mixture. This mixture was then separated by liquid chromatography, and the different components were collected. Mass spectrometry was used to determine the enriched liquid of this interlayer bonding lubricant, and the final product was obtained by rotary evaporation.

[0068] Preparation of polyamide / polyolefin alloy material particles for the outer layer of multilayer pipelines

[0069] Example A1

[0070] In polyamide / polyolefin alloy materials used for the outer layer of multilayer pipelines, the components and their amounts are as follows, based on a weight of 100wt% for each component:

[0071] Long-chain polyamide, 78 wt%

[0072] Interlayer bonding lubricant, 0.4 wt%;

[0073] Polyolefin, 10 wt%

[0074] Plasticizer, 10 wt%;

[0075] Other processing aids, 1.6 wt%;

[0076] in,

[0077] The long-chain polyamide is polyamide 12;

[0078] Interlayer bonding lubricant has the structure shown in the following formula:

[0079] In the formula, the two R's are isobutyl groups;

[0080] That is, the N-(2-isobutoxyphenyl)-N'-(2-isobutylphenyl)-oxalamide prepared as above has a purity greater than 99% as characterized by GC-MS;

[0081] The polyolefin is a copolymer polypropylene, grade 456J, with a melt index of 2.1 g / 10 min at 230℃ and 2.16 kg.

[0082] The plasticizer is N-butylbenzenesulfonamide;

[0083] The antioxidant brands are 1098 (0.4 wt%) and 168 (0.2 wt%).

[0084] Other processing aids include: lubricant (0.1 wt% erucamide and 0.1 wt% silicone), UV stabilizer UV 329 (0.1 wt%), light stabilizer 770 (0.1 wt%), and black masterbatch (0.6 wt%).

[0085] Polyamide / polyolefin alloy material particles A1 are prepared by the following steps:

[0086] Long-chain polyamide, interlayer bonding lubricant, polyolefin, and other processing aids are added to a low-speed mixer according to the specified ratio and mixed evenly at 100 rpm for 10 minutes. The resulting mixture is then melt-extruded in a twin-screw extruder at 500 rpm. During the extrusion process, the processing temperature is 230°C in the feeding section, approximately 250°C in the plasticizing and homogenizing sections, and 230°C at the die head. The capacity is 50 kg / h, and the vacuum degree is -0.05 MPa. The plasticizer is added via a liquid-side feed loss weighing system.

[0087] Example A2

[0088] The preparation steps of polyamide / polyolefin alloy material particles A2 are the same as in Example A1, except that the amount of interlayer bonding lubricant in the polyamide / polyolefin alloy material formulation is changed to 1.0 wt%, and the amount of long carbon chain polyamide is changed to 77.4 wt%. All other process conditions and operation steps are the same as in Example A1.

[0089] Example A3

[0090] The preparation steps of polyamide / polyolefin alloy material particles A3 are the same as in Example A1, except that the amount of interlayer bonding lubricant in the polyamide / polyolefin alloy material formulation is changed to 0.05wt% and the amount of long carbon chain polyamide is changed to 78.35wt%. All other process conditions and operation steps are the same as in Example A1.

[0091] Example A4

[0092] The preparation steps of polyamide / polyolefin alloy material particles A4 are the same as in Example A1, except that the amount of interlayer bonding lubricant in the polyamide / polyolefin alloy material formulation is changed to 0.2wt%, and the amount of long carbon chain polyamide is changed to 78.2wt%. All other process conditions and operation steps are the same as in Example A1.

[0093] Example A5

[0094] The preparation steps of polyamide / polyolefin alloy material particles A5 are the same as in Example A1, except that the amount of polyolefin in the polyamide / polyolefin alloy material formulation is changed to 20wt% and the amount of long carbon chain polyamide is changed to 68wt%. All other process conditions and operation steps are the same as in Example A1.

[0095] Comparative Example A1'

[0096] The preparation steps of polyamide / polyolefin alloy material particles A1' are the same as in Example A1, except that the amount of interlayer bonding lubricant is changed to 1.5wt% and the amount of long carbon chain polyamide is changed to 76.9wt%. All other process conditions and operation steps are the same as in Example A1.

[0097] Comparative Example A2'

[0098] The preparation steps of polyamide / polyolefin alloy material particles A2' are the same as in Example A1, except that the amount of interlayer bonding lubricant is changed to 0 wt% and the amount of long carbon chain polyamide is changed to 78.4 wt%. All other process conditions and operation steps are the same as in Example A1.

[0099] Comparative Example A3'

[0100] The preparation steps of polyamide / polyolefin alloy material particles A3' are the same as in Example A1, except that the amount of polyolefin is changed to 25wt% and the amount of long carbon chain polyamide is changed to 63wt%. All other process conditions and operation steps are the same as in Example A1.

[0101] Comparative Example A4'

[0102] The preparation steps of polyamide / polyolefin alloy material particles A4' are the same as in Example A1, except that the amount of polyolefin is changed to 0 wt% and the amount of long carbon chain polyamide is changed to 88 wt%. All other process conditions and operation steps are the same as in Example A1.

[0103] Preparation of hydrolysis-resistant polyolefin material particles for the inner layer of multi-layer pipelines

[0104] Example B1

[0105] In hydrolysis-resistant polyolefin materials used for the inner layer of multi-layer pipes, the components and their amounts are as follows, based on a weight of 100wt% for each component:

[0106] Copolymer polypropylene, 75 wt%;

[0107] Polyethylene, 8.4 wt%;

[0108] Graft toughening agent, 15 wt%;

[0109] Other processing aids, 1.6 wt%;

[0110] in,

[0111] The copolymer polypropylene grade is 456J, and its melt flow index at 230℃ and 2.16Kg is 2.1 g / 10min.

[0112] The polyethylene grade is 23050, and its melt flow index at 190℃ and 2.16Kg is 0.3 g / 10min.

[0113] The grafting toughening agent is designated as GR216.

[0114] The antioxidant brands are 1098 (0.4 wt%) and 168 (0.2 wt%).

[0115] Other processing aids include: lubricant (0.1 wt% erucamide and 0.1 wt% silicone), UV stabilizer UV 329 (0.1 wt%), light stabilizer 770 (0.1 wt%), and black masterbatch (0.6 wt%).

[0116] Hydrolysis-resistant polyolefin material particles B1 are prepared through the following steps:

[0117] Copolymer polypropylene, polyethylene, graft toughening agent and other processing aids are added to a low-speed mixer according to the formula and mixed evenly at 100 rpm for 10 min. The resulting mixture is then melt-extruded in a twin-screw extruder at 500 rpm. During the extrusion process, the processing temperature is 200℃ in the feeding section, about 220℃ in the plasticizing and homogenizing sections, and 210℃ in the die head. The capacity is 40 kg / h and the vacuum degree is -0.05 MPa.

[0118] Comparative Example B1'

[0119] The preparation steps of hydrolysis-resistant polyolefin material particles B1' are the same as in Example B1, except that the amount of copolymer polypropylene is changed to 25 wt% and the amount of polyethylene is changed to 58.4 wt%. All other process conditions and operating steps are the same as in Example B1.

[0120] The material particles obtained in Examples A1 to A5, Example B1, and Comparative Examples A1'-A4' and B1' were tested according to the following method:

[0121] (1) Tensile strength retention rate (%) of the coolant at 120℃ and 1000h: The test sample was immersed in a pressure vessel containing coolant (50% ethylene glycol + 50% water) for (1000±1)h and at (120±1)℃. After storage, the coolant in the pressure vessel was cooled to (23±2)℃. The sample was then removed from the coolant, rinsed with water, dried with cotton cloth, and placed in a standard environment for at least 24h. The test was then conducted in accordance with GB / T 1040.2.

[0122] (2) Strength retention rate (%) of thermo-oxidative aging at 120℃ and 1000h: The test sample was placed in a forced-air oven for (1000±1)h and at (120±1)℃. After storage, the sample was taken out of the oven and placed in a standard environment for at least 24h. The test was carried out in accordance with GB / T 1040.2.

[0123] (3) Notched impact strength of simply supported beam (23℃ & -30℃): Tested according to ISO 178-2:2020 standard.

[0124] Table 2 Test results of material particles

[0125]

[0126] Preparation of multilayer pipelines

[0127] Example C1

[0128] The process was performed using a Bellaform 5050 dual-layer extruder. Polyamide / polyolefin alloy particles and hydrolysis-resistant polyolefin particles, prepared as described above, were continuously fed into the feed ports of both the outer and inner extruders. The mandrel size was 24 / 20 mm, the linear speed was 20 m / min, the outer extruder processing temperature was 240-250℃, and the inner extruder processing temperature was 200-220℃. Multi-layer tubes with an outer diameter of 18 mm and a total wall thickness of 1.5 mm were extruded. Before each sample change, the mandrel, sizing sleeve, and vacuum chamber were cleaned. After 1 hour of stable extrusion, the multi-layer tube samples were collected.

[0129] The outer extruded material is the material particles prepared in Example A1, and its outer wall thickness is controlled to be 0.75 mm; the inner extruded material is the material particles prepared in Example B1, and its inner wall thickness is controlled to be 0.75 mm; the tolerance range of the inner and outer wall thicknesses is ±0.05 mm.

[0130] Example C2

[0131] The preparation process of the multilayer pipeline is the same as in Example C1, except that the outer extrusion material is replaced with the material particles prepared in Example A2, and all other conditions are the same as in Example C1.

[0132] Example C3

[0133] The preparation process of the multilayer pipeline is the same as in Example C1, except that the outer extrusion material is replaced with the material particles prepared in Example A3, and all other conditions are the same as in Example C1.

[0134] Example C4

[0135] The preparation process of the multilayer pipeline is the same as in Example C1, except that the outer extrusion material is replaced with the material particles prepared in Example A4, and all other conditions are the same as in Example C1.

[0136] Example C5

[0137] The preparation process of the multilayer pipeline is the same as in Example C1, except that the outer extrusion material is replaced with the material particles prepared in Example A5, and all other conditions are the same as in Example C1.

[0138] Example C6

[0139] The fabrication process of the multilayer pipeline is the same as in Example C1, except that the outer layer wall thickness is adjusted to 1.05 mm and the inner layer wall thickness is adjusted to 0.45 mm; all other conditions are the same as in Example C1.

[0140] Example C7

[0141] The fabrication process of the multilayer pipeline is the same as in Example C1, except that the outer layer wall thickness is adjusted to 0.60 mm and the inner layer wall thickness is adjusted to 0.90 mm; all other conditions are the same as in Example C1.

[0142] Comparative Example C1'

[0143] The preparation process of the multilayer pipeline is the same as in Example C1, except that the outer extrusion material is replaced with the material particles prepared in Comparative Example A1', and all other conditions are the same as in Example C1.

[0144] Comparative example C2'

[0145] The preparation process of the multilayer pipeline is the same as in Example C1, except that the outer extrusion material is replaced with the material particles prepared in Comparative Example A2', and all other conditions are the same as in Example C1.

[0146] Comparative example C3'

[0147] The preparation process of the multilayer pipeline is the same as in Example C1, except that the outer extrusion material is replaced with the material particles prepared in Comparative Example A3', and all other conditions are the same as in Example C1.

[0148] Comparative Example C4'

[0149] The preparation process of the multilayer pipeline is the same as in Example C1, except that the outer extrusion material is replaced with the material particles prepared in Comparative Example A4', and all other conditions are the same as in Example C1.

[0150] Comparative Example C5'

[0151] The fabrication process of the multilayer pipeline is the same as in Example C1, except that the outer layer wall thickness is adjusted to 1.3 mm and the inner layer wall thickness is adjusted to 0.2 mm. All other conditions are the same as in Example C1.

[0152] Comparative Example C6'

[0153] The fabrication process of the multilayer pipeline is the same as in Example C1, except that the outer layer wall thickness is adjusted to 0.2 mm and the inner layer wall thickness is adjusted to 1.3 mm. All other conditions are the same as in Example C1.

[0154] Comparative Example C7'

[0155] The preparation process of the multilayer pipeline is the same as in Example C1, except that the inner extrusion material is replaced with the material particles prepared in Comparative Example B1', and all other conditions are the same as in Example C1.

[0156] The multilayer pipe materials prepared in Examples C1 to C7 and Comparative Examples C1'-C7' were tested according to the following method:

[0157] (1) Elongation at break retention rate (%) under hydrolysis resistance at 120℃ and 1000h: The pipeline sample to be tested was immersed in a pressure vessel containing coolant (50% ethylene glycol + 50% water) for (1000±1)h and at (120±1)℃. After storage, the coolant in the pressure vessel was cooled to (23±2)℃. Then the sample was taken out of the coolant, rinsed with water, dried with cotton cloth, and placed in a standard environment for at least 24h. Then the pipeline tensile test was carried out in accordance with GB / T 1040.2.

[0158] (2) Interlayer adhesion (N): Cut the pipeline sample to be tested into a standard 5A strip size, cut the inner and outer layers along one end of the clamping end with a utility knife to half the test length, clamp the inner and outer layers on a universal testing machine, and perform a tensile test according to GB / T 1040.2. Calculate the adhesion force according to the tensile force value and the remaining area.

[0159] (3) Low temperature impact performance of pipelines at -40 degrees Celsius (per 10 pipes): 10 pipeline samples were randomly selected for the pipeline impact test at -40 degrees Celsius. 0 / 10 means that 0 out of 10 pipes failed. If all 10 pipes passed the impact test, the test was qualified.

[0160] Table 3 Performance test results of multi-layer pipelines

[0161]

[0162] As shown in Table 2, the outer polyamide / polyolefin alloy materials prepared in Examples A1 to A5 of this invention have excellent heat aging resistance and room temperature and low temperature impact performance. Their thermo-oxidative aging strength retention rate is ≥80% at 20℃ for 1000h, and their low temperature impact strength is ≥115KJ / m. 2 Compared with comparative examples A1'-A4', in the formulation of the outer polyamide / polyolefin alloy material, the introduction of interlayer adhesive lubricant or its amount has little effect on the basic mechanical properties of the resulting material, while the introduction of copolymer polyolefin is beneficial to improving its hydrolysis resistance and low-temperature impact toughness, but its excessive amount has a negative effect on impact performance.

[0163] Example B1 of the present invention exhibits excellent hydrolysis resistance, with a coolant tensile strength retention rate of ≥85% at 120°C and 1000h. Compared with Example B1, Comparative Example B1' reduces the content of copolymer polypropylene and increases the content of polyethylene in the inner layer material formulation, which has a negative effect on its hydrolysis resistance, heat resistance and impact strength.

[0164] As can be seen from Table 3, because an interlayer binder was added to the outer polyamide / polyolefin alloy material formulation used in the embodiments of the present invention, the interlayer adhesion of the multilayer pipeline is greater than or equal to 100N, and the pipeline did not break under low temperature impact. At the same time, the appearance of the continuously extruded multilayer pipeline is good. Furthermore, the addition of a reasonable amount of copolymer polypropylene to the inner layer material formulation results in excellent hydrolysis resistance of the multilayer pipeline, with a rupture elongation retention rate of ≥85% after hydrolysis at 120℃ for 1000h.

[0165] Compared to the previous examples, the absence of interlayer adhesive lubricant in the outer layer material formulation, or the failure to control its dosage within a reasonable range, fails to effectively improve the interlayer adhesion of multilayer pipelines, and also fails to achieve the effect of an adhesive-free layer or provide a good appearance. Simultaneously, controlling the outer layer thickness within a reasonable range significantly improves the low-temperature impact performance of multilayer pipelines; however, if the outer layer thickness is not controlled within a suitable range, the low-temperature impact performance or water resistance of the multilayer pipelines will be poor. Furthermore, excessive content of copolyolefins in the outer layer material formulation leads to insufficient low-temperature impact performance of the multilayer pipelines, and the absence of copolyolefins in the outer layer material formulation also results in a certain degree of decrease in the hydrolysis resistance and interlayer adhesion of the multilayer pipelines. The inner layer hydrolysis-resistant polyolefin material effectively improves the hydrolysis resistance of the multilayer pipelines, while insufficient copolypropylene content leads to low hydrolysis resistance of the multilayer pipelines.

[0166] This invention illustrates a multilayer pipeline and material through the above embodiments, but the invention is not limited to the above embodiments, meaning that the invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the invention, equivalent substitutions of raw materials, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this invention.

Claims

1. A multi-layer pipeline, comprising an outer layer and an inner layer, characterized in that, (I) The outer layer is made of a polyamide / polyolefin alloy material, wherein the polyamide / polyolefin alloy material includes at least polyamide, polyolefin, and interlayer adhesive lubricant; wherein the weight percentage of the interlayer adhesive lubricant is 0.05~1.0 wt%, the weight percentage of the polyolefin is 2-20 wt%, and the weight percentage of the polyamide is greater than or equal to 50 wt%; the polyamide includes at least one long-chain polyamide; the number of carbon atoms in the repeating unit of the long-chain polyamide is ≥8; the interlayer adhesive lubricant has the characteristic structure shown in formula (I): Equation (I) In the formula: R is a saturated alkyl group having 1-12 carbon atoms; (II) The inner layer is made of a hydrolysis-resistant polyolefin material, which includes at least a copolymer polypropylene, and the copolymer polypropylene has a weight percentage greater than or equal to 50 wt%.

2. The multi-layer pipeline according to claim 1, characterized in that, The outer polyamide / polyolefin alloy material comprises the following components in weight percentages: Long-chain polyamide, 57~97.85 wt%; Interlayer bonding lubricant, 0.05~1.0wt%; Polyolefin, 2~20wt%; Plasticizer, 0~20wt%; Other processing aids, 0.1~2wt%.

3. The multi-layer pipeline according to claim 1, characterized in that, In formula (I): R is a branched alkyl group having 1-12 carbon atoms.

4. The multi-layer pipeline according to claim 1, characterized in that, In formula (I): R is selected from one or more combinations of the structures shown in formula R1, formula R2 or formula R3; Formula R1; Equation R2; , Formula R3.

5. The multi-layer pipeline according to claim 1, characterized in that, The relative molecular weight of the interlayer bonding lubricant is less than or equal to 600.

6. The multi-layer pipeline according to claim 1, characterized in that, The relative molecular weight of the interlayer bonding lubricant is less than or equal to 500.

7. The multi-layer pipeline according to claim 1, characterized in that, In the polyamide / polyolefin alloy material, the long carbon chain polyamide is selected from one or more of PA610, PA612, PA1012, PA11, PA12 and PA1212.

8. The multi-layer pipeline according to any one of claims 1-7, characterized in that, In the polyamide / polyolefin alloy material, the polyolefin is selected from one or more of polyethylene, copolymer polypropylene, and homopolymer polypropylene.

9. The multi-layer pipeline according to claim 8, characterized in that, In the polyamide / polyolefin alloy material, the polyolefin is copolymer polypropylene.

10. The multi-layer pipeline according to claim 2, characterized in that, In the polyamide / polyolefin alloy material, the plasticizer is selected from one or more of N-butylbenzenesulfonamide, phthalate, and 2-hexyldecyl4-hydroxybenzoate; In the polyamide / polyolefin alloy material, the other processing aids include one or more of antioxidants, lubricants, hydrolysis resistant agents, flame retardants, light stabilizers, pigments, and inorganic salts.

11. The multi-layer pipeline according to claim 10, characterized in that, In the polyamide / polyolefin alloy material, the plasticizer is N-butylbenzenesulfonamide.

12. The multi-layer pipeline according to claim 1, characterized in that, The hydrolysis-resistant polyolefin material of the inner layer includes: polypropylene, polyethylene, graft toughening agents, and other processing aids; The polypropylene is copolymer polypropylene or a combination of copolymer polypropylene and homopolymer polypropylene; The grafting toughening agent is selected from one or more of POE-MAH, POE-GMA, EPDM-MAH, EPDM-GMA, EMA-GMA, and EBA-GMA.

13. In the multilayer pipeline according to claim 12, the graft toughening agent in the hydrolysis-resistant polyolefin material has a weight percentage content of 5-25 wt%.

14. The multi-layer pipeline according to any one of claims 1-7 and 9-13, characterized in that, The multi-layer pipeline is of the type of corrugated pipe or plain pipe, with an outer diameter of 6~55mm and a total wall thickness of 1~5mm; The outer layer accounts for 20% to 80% of the total wall thickness of the multilayer pipeline.

15. The multi-layer pipeline according to claim 14, characterized in that, The outer diameter of the multi-layer pipeline is 6~22mm.

16. The multi-layer pipeline according to claim 14, characterized in that, The total wall thickness of the multi-layer pipeline is 1~3mm.

17. The multi-layer pipeline according to claim 14, characterized in that, The outer layer accounts for 40% to 70% of the total wall thickness of the multilayer pipeline.

18. The method for preparing a multilayer pipeline as described in any one of claims 1-17, characterized in that, Includes the following steps: (1) Preparation of outer layer polyamide / polyolefin alloy material particles The raw material components are mixed evenly, and then the resulting mixture is melt-extruded in a twin-screw extruder. (2) Preparation of hydrolysis-resistant polyolefin material particles for the inner layer The raw material components are mixed evenly, and then the resulting mixture is melt-extruded in a twin-screw extruder. (3) Multi-layer co-extrusion process Using a double-layer extruder, the polyamide / polyolefin alloy material particles and hydrolysis-resistant polyolefin material particles obtained in the above steps are respectively added to the feed ports of the outer extruder and the inner extruder for processing to prepare the multilayer pipeline.

19. The method for preparing a multilayer pipeline according to claim 18, characterized in that, In step (1), the rotation speed of the twin-screw extruder is 200-500 rpm; the extrusion processing temperatures are: 210-230℃ for the feeding section, 230-250℃ for the plasticizing and homogenizing sections, 210-230℃ for the die head, and -0.01 to -0.08 MPa for the vacuum degree; the plasticizer is added by a liquid-side feed loss weighing system.

20. The method for preparing a multilayer pipeline according to claim 18, characterized in that, In step (2), the rotation speed of the twin-screw extruder is 200-500 rpm, and the extrusion processing temperatures are: 190-200℃ for the feeding section, 200-220℃ for the plasticizing and homogenizing sections, 190-210℃ for the die head, and -0.01 to -0.08 MPa for the vacuum degree.

21. The method for preparing a multilayer pipeline according to claim 18, characterized in that, In step (3), the co-extrusion line speed is 5-30 m / min; the processing temperature of the outer extruder is 240-250℃, and the processing temperature of the inner extruder is 200-220℃.

22. The application of the multilayer pipeline as described in any one of claims 1-17 or the multilayer pipeline prepared by the method as described in any one of claims 18-21 in the fields of air brake pipelines, cooling pipelines, fuel pipelines, lubricating oil pipelines and oil-gas pipelines.

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