Multi-layer pipeline and preparation method and application thereof

Abstract

The invention belongs to the technical field of multi-layer pipelines, and particularly relates to a multi-layer pipeline and a preparation method and application thereof. The multi-layer pipeline comprises an outer layer and an inner layer, wherein (I) the outer layer is made of a polyamide / polyolefin alloy material, and the polyamide / polyolefin alloy material at least comprises polyamide, polyolefin and an interlayer bonding lubricant; wherein the content of the interlayer bonding lubricant is 0.05-1.0 wt%, the content of the polyolefin is 2-20 wt%, and the content of the polyamide is greater than or equal to 50 wt%; the polyamide at least comprises one kind of long-carbon-chain polyamide; the number of carbon atoms in a repeating unit of the long-carbon-chain polyamide is greater than or equal to 8; (II) the inner layer is made of a hydrolysis-resistant polyolefin material, the hydrolysis-resistant polyolefin material at least comprises co-polypropylene, and the content of the co-polypropylene is greater than or equal to 50wt%. The multilayer pipeline disclosed by the invention has excellent apparent glossiness, low-temperature impact toughness and high hydrolysis resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of multi-layer pipelines, and in particular relates to a multi-layer pipeline and a preparation method and application thereof. Background Art

[0002] With the increasing global awareness of environmental protection and the transformation of energy structure, the new energy vehicle (NEV) industry is developing rapidly at an unprecedented speed. This rapid development is not only reflected in the expansion of market scale, but also drives the technological innovation of the entire industry chain. As one of the core components of automobiles, the design and manufacture of vehicle pipeline systems face unprecedented challenges and opportunities. With the advancement of new energy vehicle technology, the requirements for vehicle pipelines are also increasing. Not only must they meet basic fluid transmission functions, but they must also adapt to the unique working environment of new energy vehicles. At present, rubber pipelines such as EPDM commonly used in traditional automobiles are gradually being eliminated by the market due to factors such as heavy weight and poor recyclability.

[0003] Polyamide materials play an important role in the automotive field due to their excellent mechanical properties, excellent chemical corrosion resistance and outstanding wear resistance. In particular, long-chain polyamides, such as PA11 and PA12, are widely used in pipeline systems for transporting water, gas, chemical solvents and fuel due to their excellent weather resistance, oil resistance and high flexibility under low temperature conditions. However, single-layer long-chain nylon pipes have some problems such as high cost and insufficient hydrolysis resistance. Therefore, multi-layer composite pipe technology is currently booming. For example:

[0004] Patent document CN108343790 A discloses a multi-layer pipeline structure characterized by an inner layer of ethylene propylene diene monomer rubber (EPDM), a middle layer of polypropylene-modified EPDM, 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 bursting pressure of the 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. The 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 polyamide and polypropylene do not adhere to each other, so it requires an expensive adhesive layer and a more complicated extrusion process, which affects its production and processing efficiency.

[0006] Therefore, it is expected in this field to develop a new type of multilayer pipeline that can not only meet the needs of long-term hydrolysis resistance, heat aging resistance and high explosion 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 the present invention is to provide a multi-layer pipeline and a preparation method and application thereof in view of the deficiencies in the prior art. By optimizing the composition of the outer layer material and the inner layer material, the multi-layer pipeline processing can achieve high-layer bonding strength only with a double-layer extruder, that is, efficient bonding between multi-layer pipes can be achieved without adhesive layer bonding, which greatly reduces the requirements for production equipment and improves production efficiency. At the same time, the apparent gloss of the multi-layer pipeline can be significantly improved, and problems such as die precipitation can be reduced. The multi-layer pipeline also has the advantages of excellent low-temperature impact toughness and high hydrolysis resistance.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] In a first aspect, a multilayer pipe is provided, comprising an outer layer and an inner layer:

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

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

[0012] According to the multilayer pipe provided by the present invention, in some embodiments, the polyamide / polyolefin alloy material of the outer layer includes the following components in percentage by weight:

[0013] Long carbon chain polyamide, 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, 0.05-1.0 wt% (e.g., 0.06 wt%, 0.08 wt%, 0.1 wt%, 0.2 wt%, 0.4 wt%, 0.5 wt%, 0.8 wt%);

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

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

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

[0019]

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

[0021]

[0022] 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.

[0023] In some embodiments, the interlayer adhesive lubricant is selected from one or more of N-(2-isobutyloxyphenyl)-N'-(2-isobutylphenyl)-oxamide, N-(2-(3,4-methylpentyloxy)phenyl)-N'-(2-(3,4-methylpentyl)phenyl)-oxamide and N-(2-(5,6-methylheptyloxy)phenyl)-N'-(2-(5,6-methylheptyl)phenyl)-oxamide. That is, in the characteristic structure shown in formula (I), R is a compound corresponding to the structure shown in formula R1 (isobutyl), formula R2 (methylpentyl) or formula R3 (methylheptyl).

[0024] In some embodiments, 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, and its Ubbelohde viscosity is between 1.8 and 2.6 (for example, 1.9, 2.0, 2.1, 2.2, 2.4, 2.5).

[0025] In some embodiments, in the polyamide / polyolefin alloy material, the polyolefin is selected from one or more of polyethylene, copolymer polypropylene and homopolypropylene, preferably copolymer polypropylene.

[0026] In some embodiments, the polyolefin has a melt index of 0.1 to 5 Kg / 10 min (e.g., 0.2 Kg / 10 min, 0.5 Kg / 10 min, 1.0 Kg / 10 min, 2.0 Kg / 10 min, 3.0 Kg / 10 min, 4.0 Kg / 10 min) at 230° C. and 2.16 Kg.

[0027] In some embodiments, in the polyamide / polyolefin alloy material, the plasticizer is selected from one or more of N-butylbenzenesulfonamide, phthalates and 2-hexyldecyl 4-hydroxybenzoate, preferably N-butylbenzenesulfonamide.

[0028] In some embodiments, in the polyamide / polyolefin alloy material, the other processing aids include one or more of antioxidants, lubricants, hydrolysis resistance agents, flame retardants, UV stabilizers, light stabilizers, pigments, masterbatches and inorganic salts.

[0029] An interlayer bonding lubricant is added to the polyamide / polyolefin alloy material of the outer layer. During the extrusion process of the multi-layer pipeline, the interlayer bonding lubricant migrates to the melt surface due to the interaction between the benzene ring contained in the interlayer bonding lubricant and the molecular weight of the polyamide. On the one hand, the two R groups contained in the interlayer bonding lubricant have strong compatibility with the polyolefin material of the inner layer, and the two amide groups contained in the interlayer bonding lubricant have strong compatibility with the polyamide material of the outer layer, thereby effectively improving the interlayer bonding force; on the other hand, during the extrusion process, the outer surface in contact with the metal of the extruder die can form a non-polar protective film composed of R groups, which effectively reduces the bonding force between the polar amide bond and the metal die and reduces the processing friction, thereby significantly improving the apparent gloss of the multi-layer pipeline and reducing problems such as die precipitation.

[0030] In addition, the polyolefin contained in the polyamide / polyolefin alloy material of the outer layer can, on the one hand, improve the compatibility between the outer layer material and the inner layer material, and on the other hand, increase the tying molecules between the polyamide crystal regions, thereby effectively improving the low-temperature impact toughness of the multilayer pipeline.

[0031] According to the multilayer pipe provided by the present invention, in some embodiments, the hydrolysis-resistant polyolefin material of the inner layer includes: polypropylene, polyethylene, a graft toughening agent and optionally other processing aids.

[0032] In some embodiments, the polypropylene is a copolymer polypropylene or a combination of a copolymer polypropylene and a homopolypropylene.

[0033] In some embodiments, the grafted 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%, 0.6%.

[0034] In some embodiments, in the hydrolysis-resistant polyolefin material, the weight percentage of the grafted toughening agent is 5 to 25 wt% (e.g., 6 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, 24 wt%).

[0035] In some embodiments, in the hydrolysis-resistant polyolefin material, the weight percentage of the polyethylene is 1-15wt% (for example, 2wt%, 4wt%, 5wt%, 8wt%, 10wt%, 12wt%, 14wt%); the content of other processing aids is 0-5wt% (for example, 0.05wt%, 0.1wt%, 0.2wt%, 0.4wt%, 0.5wt%, 1.0wt%, 1.5wt%, 1.8wt%, 2.0wt%, 4.0wt%).

[0036] The other processing aids in the hydrolysis-resistant polyolefin material include one or more of antioxidants, lubricants, hydrolysis resistance agents, flame retardants, ultraviolet stabilizers, light stabilizers, pigments, masterbatches and inorganic salts.

[0037] In some embodiments, the hydrolysis-resistant polyolefin material includes the following components in weight percentage:

[0038] Copolymer polypropylene, 55-90wt%;

[0039] Polyethylene, 0-15wt%;

[0040] Graft toughening agent, 5-25wt%;

[0041] Other processing aids, 0-5wt%.

[0042] The hydrolysis-resistant polyolefin material used as the inner layer contains copolymerized polypropylene in a weight percentage of ≥50wt%, which can provide excellent hydrolysis resistance. At the same time, the contained grafted toughening agent can effectively improve the low-temperature toughness of the inner layer material, solving the problem of poor low-temperature toughness of copolymerized polypropylene. Therefore, the hydrolysis-resistant polyolefin material used as the inner layer provides excellent hydrolysis resistance and fuel erosion resistance to the multi-layer pipeline, while effectively reducing the overall cost of the multi-layer pipeline.

[0043] According to the multilayer pipeline provided by the present invention, in some embodiments, the type of the multilayer pipeline is a corrugated tube or a smooth tube, and its outer diameter is 6 to 55 mm (for example, 8 mm, 10 mm, 12 mm, 15 mm, 18 mm, 20 mm, 25 mm, 30 mm, 40 mm, 50 mm), preferably 6 to 22 mm; its total wall thickness is 1 to 5 mm (for example, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm), preferably 1 to 3 mm;

[0044] The wall thickness of the outer layer accounts for 20% to 80% (for example, 25%, 30%, 35%, 45%, 50%, 60%, 65%, 75%) of the total wall thickness of the multilayer pipeline, and preferably 40% to 70%.

[0045] In a second aspect, a method for preparing the multilayer pipeline as described above is provided, comprising the following steps:

[0046] (1) Preparation of polyamide / polyolefin alloy material particles for the outer layer

[0047] The raw material components are uniformly mixed, and the resulting mixed ingredients are melt-extruded in a twin-screw extruder;

[0048] In some embodiments, the speed of the twin-screw extruder is 200-500rpm (e.g., 250rpm, 300rpm, 350rpm, 400rpm, 450rpm); the extrusion processing temperatures are: the feeding section temperature is 210-230°C, the plasticizing section and homogenizing section temperature is 230-250°C, the die head temperature is 210-230°C, and the vacuum degree is -0.01 to -0.08MPa (e.g., -0.02MPa, -0.04MPa, -0.05MPa, -0.06MPa); the plasticizer is added by a liquid side feeding loss-in-weight scale;

[0049] (2) Preparation of hydrolysis-resistant polyolefin material particles for the inner layer

[0050] The raw material components are uniformly mixed, and the resulting mixed ingredients are melt-extruded in a twin-screw extruder;

[0051] In some embodiments, the speed of the twin-screw extruder is 200-500 rpm (e.g., 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm), and the extrusion processing temperatures are: the feeding section temperature is 190-200° C., the plasticizing section and homogenizing section temperatures are 200-220° C., the die temperature is 190-210° C., and the vacuum degree is -0.01 to -0.08 MPa (e.g., -0.02 MPa, -0.04 MPa, -0.05 MPa, -0.06 MPa);

[0052] (3) Multi-layer co-extrusion process

[0053] Using a double-layer extruder, the polyamide / polyolefin alloy material particles and the hydrolysis-resistant polyolefin material particles prepared in the above steps are respectively added to the feeding ports of the outer layer extruder and the inner layer extruder for processing to prepare the multilayer pipeline;

[0054] Preferably, the coextrusion 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 layer extruder is 240-250°C, and the processing temperature of the inner layer extruder is 200-220°C.

[0055] In a third aspect, there is provided a multilayer pipeline as described above or the multilayer pipeline prepared by the preparation method as described above for use in the fields of air brake pipelines, cooling pipelines, fuel pipelines, lubricating oil pipelines and oil and gas pipelines.

[0056] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0057] (1) Providing an innovative multi-layer pipeline structure, which can solve the problem of heavy weight and difficulty in recycling of EPDM hoses; at the same time, it can make up for the problem of insufficient hydrolysis resistance of single-layer nylon hoses, low burst pressure and poor low-temperature toughness of single-layer polyolefin hoses; compared with the currently emerging polyamide / glue layer / polypropylene multi-layer pipelines, the multi-layer pipeline of the present invention can achieve efficient bonding between layers without a glue layer, greatly reducing the requirements for production equipment and improving production efficiency;

[0058] (2) The innovative introduction of interlayer bonding lubricant into the outer alloy material effectively improves the interlayer bonding strength of the multilayer pipe. At the same time, it can effectively reduce the bonding strength between the polar amide bond and the metal mold during the pipe extrusion process, reduce processing friction, and significantly improve the apparent gloss of the multilayer pipe. At the same time, it can reduce problems such as die precipitation. In addition, the polyolefin contained in the polyamide / polyolefin alloy material of the outer layer can effectively improve the low-temperature impact toughness of the multilayer pipe.

[0059] (3) The hydrolysis-resistant polyolefin material of the inner layer contains copolymerized polypropylene in a weight percentage of ≥50wt%, which can provide excellent hydrolysis resistance. At the same time, the grafted toughening agent contained in the material can effectively improve the low-temperature toughness of the inner layer material, thereby solving the problem of poor low-temperature toughness of copolymerized polypropylene. DETAILED DESCRIPTION

[0060] In order to understand the technical features and content of the present invention in detail, the preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described in the embodiments, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. For those who do not specify specific conditions in the embodiments, they are carried out according to normal conditions or the conditions recommended by the manufacturer.

[0061] The raw material grades and supplier information used in the preparation examples and embodiments of the present invention are as follows:

[0062] Table 1 Raw material grades and supplier information

[0063] Raw material grade Material Type Raw material manufacturers L3001 Polyamide 12 Wanhua Chemical Group Co., Ltd. N-Butylbenzenesulfonamide Plasticizers ANNAIJI CHEMICAL CO., LTD. Interlayer bonding lubricant Interlayer bonding lubricant self made 456J Copolymer polypropylene Wanhua Chemical Group Co., Ltd. 23050 Polyethylene Wanhua Chemical Group Co., Ltd. GR216 Graft toughening agent DowDuPont Black mother Black Masterbatch Shanghai Cabot Chemical Co., Ltd. UV329 UV absorber BASF SE 1098 Antioxidants BASF SE 168 Antioxidants BASF SE Erucamide Lubricants Croda Chemical Silicone Lubricants Slike Technology Co., Ltd.

[0064] Preparation of interlayer bonding lubricant

[0065] In the structure shown in formula (I), the preparation process of the compound in which R is a structure shown in formula R1 (i.e., N-(2-isobutyloxyphenyl)-N'-(2-isobutylphenyl)-oxalamide) is as follows:

[0066] 1.0MPaG low-pressure saturated steam is introduced outside the heat exchange tube, and liquid dimethyl oxalate begins to evaporate under steam heating conditions, and the evaporation pressure of dimethyl oxalate is controlled to be about 0.1MPaG, and the evaporation temperature is about 130°C; then the vaporized dimethyl oxalate is continuously introduced into a reactor to which 2-isobutyloxybenzene and 2-isobutylbenzene have been added, and the initial concentration of each component material in the reactor is 1mol / L, the reaction pressure of the reactor is controlled to be about 0.1MPaG, the reaction temperature is about 130°C, and the reaction time is 30min to obtain a mixture; then the mixture is separated by a liquid chromatography column, different components are collected, the enriched liquid of the interlayer bonding lubricant is determined by mass spectrometry, and the final product is obtained by a rotary evaporator separator.

[0067] Preparation of polyamide / polyolefin alloy material particles for the outer layer of multilayer pipelines

[0068] Example A1

[0069] In the polyamide / polyolefin alloy material used for the outer layer of the multi-layer pipeline, the weight of each component is 100wt%, and the components and their amounts are as follows:

[0070] Long carbon chain polyamide, 78wt%;

[0071] Interlayer bonding lubricant, 0.4wt%;

[0072] Polyolefin, 10 wt%;

[0073] Plasticizer, 10wt%;

[0074] Other processing aids, 1.6 wt%;

[0075] in,

[0076] The long carbon chain polyamide is polyamide 12;

[0077] The interlayer bonding lubricant has the structure shown in the following formula:

[0078] In the formula, two R are isobutyl groups;

[0079] That is, the N-(2-isobutyloxyphenyl)-N'-(2-isobutylphenyl)-oxalamide prepared as above has a purity greater than 99% as characterized by GC-MS;

[0080] The polyolefin is copolymerized polypropylene, the grade is 456J, and its melt index at 230°C and 2.16Kg is 2.1Kg / 10min;

[0081] The plasticizer is N-butylbenzenesulfonamide;

[0082] The antioxidant grades are 1098 (dosage is 0.4wt%) and 168 (dosage is 0.2wt%);

[0083] Other processing aids include: lubricant (erucamide at 0.1wt%, silicone at 0.1wt%), UV stabilizer UV 329 (at 0.1wt%), light stabilizer 770 (at 0.1wt%) and black masterbatch (at 0.6wt%).

[0084] The polyamide / polyolefin alloy material particles A1 are prepared by the following steps:

[0085] Long carbon chain polyamide, interlayer adhesive lubricant, polyolefin and other processing aids are added into a low mixer according to the proportion and uniformly mixed at a rotation speed of 100 rpm and a mixing time of 10 min. The obtained mixed ingredients are then melt-extruded in a twin-screw extruder at a rotation speed of 500 rpm. During the extrusion process, the processing temperature is 230°C in the feeding section, about 250°C in the plasticizing section and the homogenizing section, 230°C in the die head temperature, 50Kg / h in production capacity, and -0.05MPa in vacuum degree. The plasticizer is added through a liquid side feeding loss-in-weight scale.

[0086] Example A2

[0087] The preparation steps of polyamide / polyolefin alloy material particles A2 refer to Example A1, with the only difference that in the polyamide / polyolefin alloy material formula, the amount of interlayer bonding lubricant is changed to 1.0wt%, and the amount of long carbon chain polyamide is changed to 77.4wt%. Other process conditions and operating steps are the same as Example A1.

[0088] Example A3

[0089] The preparation steps of polyamide / polyolefin alloy material particles A3 refer to Example A1, with the only difference that in the polyamide / polyolefin alloy material formula, the amount of interlayer bonding lubricant is changed to 0.05wt%, and the amount of long carbon chain polyamide is changed to 78.35wt%. Other process conditions and operating steps are the same as Example A1.

[0090] Example A4

[0091] The preparation steps of polyamide / polyolefin alloy material particles A4 refer to Example A1, with the only difference that in the polyamide / polyolefin alloy material formula, the amount of interlayer bonding lubricant is changed to 0.2wt%, and the amount of long carbon chain polyamide is changed to 78.2wt%. Other process conditions and operating steps are the same as Example A1.

[0092] Example A5

[0093] The preparation steps of polyamide / polyolefin alloy material particles A5 refer to Example A1, with the only difference that in the polyamide / polyolefin alloy material formula, the amount of polyolefin is changed to 20wt%, and the amount of long carbon chain polyamide is changed to 68wt%. Other process conditions and operating steps are the same as Example A1.

[0094] Comparative Example A1'

[0095] The preparation steps of polyamide / polyolefin alloy material particles A1' refer to 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%. Other process conditions and operation steps are the same as Example A1.

[0096] Comparative Example A2'

[0097] The preparation steps of polyamide / polyolefin alloy material particles A2' refer to Example A1, except that the amount of interlayer bonding lubricant is changed to 0wt%, the amount of long carbon chain polyamide is changed to 78.4wt%, and other process conditions and operation steps are the same as Example A1.

[0098] Comparative Example A3'

[0099] The preparation steps of polyamide / polyolefin alloy material particles A3' refer to Example A1, except that the amount of polyolefin is changed to 25wt% and the amount of long carbon chain polyamide is changed to 63wt%. Other process conditions and operation steps are the same as Example A1.

[0100] Comparative Example A4'

[0101] The preparation steps of polyamide / polyolefin alloy material particles A4' refer to Example A1, except that the amount of polyolefin is changed to 0wt% and the amount of long carbon chain polyamide is changed to 88wt%. Other process conditions and operation steps are the same as Example A1.

[0102] Preparation of hydrolysis-resistant polyolefin material particles for the inner layer of multi-layer pipelines

[0103] Example B1

[0104] In the hydrolysis-resistant polyolefin material used for the inner layer of the multi-layer pipe, the weight of each component is 100wt%, and the components and their amounts are as follows:

[0105] Copolymer polypropylene, 75wt%;

[0106] Polyethylene, 8.4 wt%;

[0107] Graft toughening agent, 15wt%;

[0108] Other processing aids, 1.6 wt%;

[0109] in,

[0110] The copolymer polypropylene grade is 456J, and its 230°C, 2.16Kg melt index is 2.1Kg / 10min;

[0111] The polyethylene grade is 23050, and its melt index at 190°C and 2.16Kg is 0.3Kg / 10min;

[0112] The graft toughening agent brand is GR216;

[0113] The antioxidant brands are 1098 (dosage is 0.4wt%) and 168 (dosage is 0.2wt%);

[0114] Other processing aids include: lubricant (erucamide at 0.1wt%, silicone at 0.1wt%), UV stabilizer UV 329 (at 0.1wt%), light stabilizer 770 (at 0.1wt%) and black masterbatch (at 0.6wt%).

[0115] The hydrolysis-resistant polyolefin material particles B1 are prepared by the following steps:

[0116] Copolymer polypropylene, polyethylene, graft toughening agent and other processing aids are added into a low mixer according to a proportion and uniformly mixed at a rotation speed of 100 rpm and a mixing time of 10 min; then the obtained mixed ingredients are melt-extruded in a twin-screw extruder at a rotation speed of 500 rpm. During the extrusion process, the processing temperature is 200° C. in the feeding section, about 220° C. in the plasticizing section and the homogenizing section, 210° C. in the die head, with a production capacity of 40 Kg / h and a vacuum degree of -0.05 MPa.

[0117] Comparative Example B1'

[0118] The preparation steps of hydrolysis-resistant polyolefin material particles B1' are the same as those of Example B1, except that the amount of copolymerized polypropylene is changed to 25wt%, and the amount of polyethylene is changed to 58.4wt%. Other process conditions and operation steps are the same as those of Example B1.

[0119] The material particles obtained in Examples A1 to A5, Example B1 and Comparative Examples A1'-A4', B1' were tested according to the following method:

[0120] (1) Retention rate of tensile strength of coolant resistance at 120°C for 1000 h (%): The specimen to be tested is immersed in an autoclave filled with coolant (50% ethylene glycol + 50% water) for (1000±1) h at a temperature of (120±1)°C. After storage, the coolant in the autoclave is cooled to (23±2)°C. The specimen is then taken out of the coolant, rinsed with water, wiped dry with cotton cloth, and placed in a standard environment for at least 24 h before being tested in accordance with GB / T 1040.2.

[0121] (2) Strength retention rate after thermal oxidative aging at 120°C for 1000 h (%): Place the specimens to be tested in a forced air oven for (1000±1) h at a temperature of (120±1)°C. After storage, remove the specimens from the oven and place them in a standard environment for at least 24 h before testing them in accordance with GB / T1040.2.

[0122] (3) Simple supported beam notched impact strength (23℃ & -30℃): tested in accordance with ISO 178-2:2020.

[0123] Table 2 Test results of material particles

[0124]

[0125] Preparation of multilayer pipes

[0126] Example C1

[0127] Bellaform 5050 double-layer extruder was used for processing, and the polyamide / polyolefin alloy material particles and hydrolysis-resistant polyolefin material particle samples prepared as above were continuously added to the feeding ports of the outer extruder and the inner extruder. The size of the core die was 24 / 20 mm, the line speed was 20 m / min, the processing temperature of the outer extruder was 240-250°C, and the processing temperature of the inner extruder was 200-220°C; a multilayer tube with an outer diameter of 18 mm and a total wall thickness of 1.5 mm was extruded; the core die, sizing sleeve, and vacuum box were cleaned before each sample switching, and the multilayer tube samples were collected after stable extrusion for 1 hour; wherein,

[0128] The outer layer extrusion material is the material particles prepared in Example A1, and the outer layer wall thickness is controlled to be 0.75 mm; the inner layer extrusion material is the material particles prepared in Example B1, and the inner layer wall thickness is controlled to be 0.75 mm; the tolerance range of the inner and outer layer wall thickness is ±0.05 mm.

[0129] Example C2

[0130] The multi-layer pipeline preparation process refers to Example C1, with the only difference being that the outer layer extrusion material is replaced with the material particles prepared in Example A2, and the other conditions are the same as in Example C1.

[0131] Example C3

[0132] The multi-layer pipeline preparation process refers to Example C1, the only difference is that the outer layer extrusion material is replaced with the material particles prepared in Example A3, and the other conditions are the same as Example C1.

[0133] Example C4

[0134] The multi-layer pipeline preparation process refers to Example C1, with the only difference being that the outer layer extrusion material is replaced with the material particles prepared in Example A4, and the other conditions are the same as in Example C1.

[0135] Example C5

[0136] The multi-layer pipeline preparation process refers to Example C1, with the only difference being that the outer layer extrusion material is replaced with the material particles prepared in Example A5, and the other conditions are the same as in Example C1.

[0137] Example C6

[0138] The multi-layer pipeline preparation process refers to 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; other conditions are the same as Example C1.

[0139] Example C7

[0140] The multi-layer pipeline preparation process refers to Example C1, the only difference is that the outer layer wall thickness is adjusted to 0.60 mm, and the inner layer wall thickness is adjusted to 0.90 mm; other conditions are the same as Example C1.

[0141] Comparative Example C1'

[0142] The preparation process of the multilayer pipeline is similar to that of Example C1, except that the outer layer extrusion material is replaced with the material particles prepared in Comparative Example A1', and the other conditions are the same as those of Example C1.

[0143] Comparative Example C2'

[0144] The preparation process of the multilayer pipeline is similar to that of Example C1, except that the outer layer extrusion material is replaced with the material particles prepared in Comparative Example A2', and the other conditions are the same as those of Example C1.

[0145] Comparative Example C3'

[0146] The preparation process of the multilayer pipeline is similar to that of Example C1, except that the outer layer extrusion material is replaced with the material particles prepared in Comparative Example A3', and the other conditions are the same as those of Example C1.

[0147] Comparative Example C4'

[0148] The preparation process of the multilayer pipeline is similar to that of Example C1, except that the outer layer extrusion material is replaced with the material particles prepared in Comparative Example A4', and the other conditions are the same as those of Example C1.

[0149] Comparative Example C5'

[0150] The multi-layer pipeline preparation process refers to Example C1, the only difference is that the outer layer wall thickness is adjusted to 1.3 mm, and the inner layer wall thickness is adjusted to 0.2 mm. Other conditions are the same as Example C1.

[0151] Comparative Example C6'

[0152] The multi-layer pipeline preparation process refers to Example C1, the only difference is that the outer layer wall thickness is adjusted to 0.2 mm, and the inner layer wall thickness is adjusted to 1.3 mm. Other conditions are the same as Example C1.

[0153] Comparative Example C7'

[0154] The preparation process of the multilayer pipeline is similar to that of Example C1, except that the inner layer extrusion material is replaced with the material particles prepared in Comparative Example B1', and the other conditions are the same as those of Example C1.

[0155] The multilayer pipe materials prepared in Examples C1 to C7 and Comparative Examples C1'-C7' were tested according to the following method:

[0156] (1) Retention rate of elongation at break for hydrolysis resistance at 120°C for 1000 h (%): The pipeline specimen to be tested is immersed in an autoclave filled with coolant (50% ethylene glycol + 50% water) for (1000±1) h at a temperature of (120±1)°C. After storage, the coolant in the autoclave is cooled to (23±2)°C, and the specimen is then taken out of the coolant, rinsed with water, wiped dry with cotton cloth, and placed in a standard environment for at least 24 h before the pipeline tensile test is carried out in accordance with GB / T 1040.2.

[0157] (2) Interlayer adhesion (N): Cut the pipeline sample to be tested into standard 5A specimen size, cut the inner and outer layers along one clamping end to half the test length with a utility knife, clamp the inner and outer layers separately on a universal material testing machine, and perform a tensile test in accordance with GB / T 1040.2. Calculate the adhesion based on the tensile force value and the remaining area.

[0158] (3) Low-temperature impact performance of pipelines at -40 degrees Celsius (every 10 pipes): 10 pipeline samples to be tested are randomly selected for pipeline impact test at -40 degrees Celsius. 0 / 10 means that none of the 10 pipes fail, and all 10 pipes pass the impact test, which means they are qualified.

[0159] Table 3 Performance test results of multi-layer pipelines

[0160]

[0161]

[0162]

[0163] As can be seen from Table 2, the outer layer polyamide / polyolefin alloy material prepared in Examples A1 to A5 of the present invention has excellent heat aging resistance and room temperature and low temperature impact properties. The thermal oxidation aging strength retention rate at 20°C and 1000h is ≥80%, and the low temperature impact strength is ≥115KJ / m 2 ; Compared with Comparative Examples A1'-A4', in the outer layer polyamide / polyolefin alloy material formula, the introduction of the interlayer bonding lubricant or its dosage has little effect on the basic mechanical properties of the obtained material, while the introduction of copolymerized polyolefin is beneficial to improve its hydrolysis resistance and low-temperature impact toughness, but its excessive dosage has a negative effect on the impact performance;

[0164] Example B1 of the present invention exhibits excellent hydrolysis resistance, and its coolant-resistant tensile strength retention rate at 120°C and 1000h is ≥85%; compared with Example B1, Comparative Example B1' reduces the content of copolymerized polypropylene and increases the content of polyethylene in the inner layer material formula, which has a negative effect on its hydrolysis resistance, heat resistance and impact strength.

[0165] It can be seen from Table 3 that, since an interlayer adhesive is added to the outer layer polyamide / polyolefin alloy material formula used in the embodiment of the present invention, the interlayer bonding force of the obtained multilayer pipeline is greater than or equal to 100N, and the pipeline does not break under low-temperature impact. At the same time, the appearance of the continuously extruded multilayer pipeline is good; and, a reasonable amount of copolymerized polypropylene is added to the inner layer material formula, and the obtained multilayer pipeline has excellent hydrolysis resistance, and its elongation at break retention rate after hydrolysis at 120°C and 1000h is ≥85%.

[0166] Compared with the embodiment, the interlayer bonding lubricant is not added to the outer layer material formula or its amount is not controlled within a reasonable range, which cannot effectively improve the interlayer bonding strength of the multilayer pipeline, nor can it achieve the effect of the bonding-free layer and give it a good appearance; at the same time, the outer layer thickness is controlled within a reasonable range, which can significantly improve the low-temperature impact performance of the multilayer pipeline. If the outer layer thickness is not controlled within an appropriate range, the low-temperature impact performance or water resistance of the multilayer pipeline will be poor; and excessive content of copolymerized polyolefin in the outer layer material formula will lead to insufficient low-temperature impact performance of the multilayer pipeline. Failure to add copolymerized olefin to the outer layer material formula will also lead to a certain degree of decrease in the hydrolysis resistance and interlayer bonding strength of the multilayer pipeline; the inner layer hydrolysis-resistant polyolefin material effectively improves the hydrolysis resistance of the multilayer pipeline, while insufficient content of copolymerized polypropylene will lead to low hydrolysis resistance of the multilayer pipeline.

[0167] The present invention uses the above-mentioned embodiments to illustrate a multilayer pipe and material of the present invention, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present 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 at least comprises polyamide, polyolefin and an interlayer bonding lubricant; wherein the weight percentage of the interlayer bonding lubricant is 0.05-1.0wt%, the weight percentage of the polyolefin is 2-20wt%, and the weight percentage of the polyamide is greater than or equal to 50wt%; the polyamide comprises at least one long carbon chain polyamide; and the number of carbon atoms in the repeating unit of the long carbon chain polyamide is ≥8; (II) The inner layer is made of a hydrolysis-resistant polyolefin material, wherein the hydrolysis-resistant polyolefin material at least includes copolymerized polypropylene, and the weight percentage of the copolymerized polypropylene is greater than or equal to 50 wt %.

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

3. The multi-layer pipeline according to claim 1 or 2, characterized in that: In the polyamide / polyolefin alloy material, the interlayer bonding lubricant has a characteristic structure as shown in formula (I): In the formula: R is a saturated alkyl group having 1 to 12 carbon atoms, preferably a branched alkyl group having 1 to 12 carbon atoms, and more preferably a combination of one or more structures selected from the following formula R1, formula R2 or formula R3; Preferably, the relative molecular weight of the interlayer adhesive lubricant is less than or equal to 600, preferably less than or equal to 500.

4. The multilayer pipeline according to any one of claims 1 to 3, 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.

5. The multi-layer pipeline according to any one of claims 1 to 4, characterized in that: In the polyamide / polyolefin alloy material, the polyolefin is selected from one or more of polyethylene, copolymer polypropylene and homopolypropylene, preferably copolymer polypropylene; The polyolefin has a melting index of 0.1 to 5 Kg / 10 min at 230° C. and 2.16 Kg.

6. The multi-layer pipeline according to any one of claims 1 to 5, characterized in that: In the polyamide / polyolefin alloy material, the plasticizer is selected from one or more of N-butylbenzenesulfonamide, phthalate and 2-hexyldecyl 4-hydroxybenzoate, preferably N-butylbenzenesulfonamide; In the polyamide / polyolefin alloy material, the other processing aids include one or more of antioxidants, lubricants, hydrolysis resistance agents, flame retardants, ultraviolet stabilizers, light stabilizers, pigments, masterbatches and inorganic salts.

7. The multi-layer pipeline according to any one of claims 1 to 6, characterized in that: The hydrolysis-resistant polyolefin material of the inner layer comprises: polypropylene, polyethylene, a graft toughening agent and other optional processing aids; The polypropylene is copolymer polypropylene or a combination of copolymer polypropylene and homopolymer polypropylene; The graft toughening agent is selected from one or more of POE-MAH, POE-GMA, EPDM-MAH, EPDM-GMA, EMA-GMA and EBA-GMA; Preferably, in the hydrolysis-resistant polyolefin material, the weight percentage of the graft toughening agent is 5 to 25 wt %.

8. The multi-layer pipeline according to any one of claims 1 to 7, characterized in that: The multi-layer pipe is a corrugated pipe or a smooth pipe, and its outer diameter is 6 to 55 mm, preferably 6 to 22 mm; its total wall thickness is 1 to 5 mm, preferably 1 to 3 mm; The wall thickness of the outer layer accounts for 20% to 80% of the total wall thickness of the multi-layer pipeline, preferably 40% to 70%.

9. The method for preparing a multi-layer pipeline according to any one of claims 1 to 8, characterized in that: The steps include: (1) Preparation of polyamide / polyolefin alloy material particles for the outer layer The raw material components are uniformly mixed, and the resulting mixed ingredients are melt-extruded in a twin-screw extruder; Preferably, the speed of the twin-screw extruder is 200-500rpm; the extrusion processing temperatures are: the feeding section temperature is 210-230°C, the plasticizing section and homogenizing section temperatures are 230-250°C, the die head temperature is 210-230°C, and the vacuum degree is -0.01 to -0.08MPa; the plasticizer is added through a liquid side feeding weight loss scale; (2) Preparation of hydrolysis-resistant polyolefin material particles for the inner layer The raw material components are uniformly mixed, and the resulting mixed ingredients are melt-extruded in a twin-screw extruder; Preferably, the speed of the twin-screw extruder is 200-500rpm, the extrusion processing temperatures are: the feeding section temperature is 190-200°C, the plasticizing section and homogenizing section temperatures are 200-220°C, the die head temperature is 190-210°C, and the vacuum degree is -0.01 to -0.08MPa; (3) Multi-layer co-extrusion process Using a double-layer extruder, the polyamide / polyolefin alloy material particles and the hydrolysis-resistant polyolefin material particles prepared in the above steps are respectively added to the feeding ports of the outer layer extruder and the inner layer extruder for processing to prepare the multilayer pipeline; Preferably, the co-extrusion line speed is 5-30 m / min; the processing temperature of the outer layer extruder is 240-250°C, and the processing temperature of the inner layer extruder is 200-220°C.

10. Application of the multilayer pipeline according to any one of claims 1 to 8 or the multilayer pipeline prepared by the preparation method according to claim 9 in the fields of air brake pipelines, cooling pipelines, fuel pipelines, lubricating oil pipelines and oil and gas pipelines.

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