Multilayer composite tubing material and method of making same

Abstract

The present application belongs to the technical field of multilayer pipe, and particularly relates to a multilayer composite pipe material and a preparation method thereof. The pipe material comprises the following layers: I, an outer layer made of a polyamide composition (A) comprising at least one semi-crystalline polyamide (A1); II, an inner layer made of a polyolefin composition (B) comprising at least one copolymerized polyethylene (B1); III, a modified polyolefin material (C) as a bonding layer, which is an olefin polymer modified by a polar group, for bonding the outer layer I and the inner layer II. The multilayer composite pipe of the present application has excellent high-temperature resistance and long-term use performance, better strength and low-temperature toughness, good medium resistance, and can be processed into pipes of different shapes, thereby widening the use range of the pipe.

Description

Technical Field

[0001] This invention belongs to the technical field of multilayer pipes, and particularly relates to a multilayer composite pipe material and its preparation method. Background Technology

[0002] Currently, the materials used for cooling pipes in automobiles are generally EPDM, TPV, and Nylon 12. Cooling pipes made of rubber materials generally have a wall thickness of more than 4mm. Using them in automobiles will increase the weight of the entire piping system and they are also prone to aging after long-term use, which will seriously increase the fuel consumption and power consumption per 100 kilometers. They will also take up a lot of space and are not conducive to the layout of cooling pipes. On the other hand, cooling pipes made of single-layer Nylon 12 have certain problems in terms of hydrolysis resistance, resulting in excessive water vapor permeation, which may pose certain risks in new energy vehicles.

[0003] To address the existing shortcomings, some improvements have been attempted in this field. For example:

[0004] Patent document CN1906022A discloses a multi-layer structure pipeline with an inner layer of polypropylene, a middle layer of adhesive, and an outer layer of polyamide. This pipeline structure has good hydrolysis resistance, but the low-temperature brittleness of polypropylene is poor, which leads to poor low-temperature performance of the multi-layer structure pipeline. At the same time, after the PP material is exposed to the medium, micro-cracks will appear in the component, which can easily lead to pipeline failure.

[0005] Patent document CN108343790A discloses a multi-layered pipe structure with EPDM rubber as the inner layer, polypropylene-modified EPDM rubber as the middle layer, and modified nylon 12 as the outer layer. This structure can improve the wall thickness of the pipe and greatly reduce the weight of the original rubber pipe. However, the burst pressure of this multi-layered pipe structure is not high, and the heat resistance of the rubber material is not high, which limits its application.

[0006] In view of this, there is an urgent need to develop a multi-layer piping system for (such as automobiles) cooling systems to solve the current problems of poor resistance to high and low temperatures, poor hydrolysis resistance, and high burst damage. Summary of the Invention

[0007] The purpose of this invention is to address the problems existing in existing multi-layer pipe systems used in (e.g., automotive) cooling systems by providing a multi-layer composite pipe material and its preparation method. A three-layer pipe structure is obtained by using copolymer polyethylene, which has a wide molecular weight distribution, high comonomer content, and many macromolecular chain segments, as the inner layer. This improves the pipe's high-temperature resistance and long-term performance, while the outer polyamide material imparts good strength, low-temperature toughness, and good media resistance. More importantly, it also results in a high elongation at break and low internal stress, allowing for the fabrication of pipes in various shapes and broadening the application range of the pipe material.

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

[0009] In a first aspect, a multilayer composite piping material is provided, comprising the following layers:

[0010] I. An outer layer made of a polyamide composition (A), wherein the polyamide composition (A) comprises at least one semi-crystalline polyamide (Al), wherein each nitrogen atom has an average number of carbon atoms Nc between 8 and 18 (e.g., 10, 11, 14, 16), preferably between 9 and 12;

[0011] II. An inner layer made of a polyolefin composition (B), wherein the polyolefin composition (B) comprises at least one copolymer polyethylene (B1);

[0012] III. Modified polyolefin material (C) is used as an adhesive layer. It is an olefin polymer modified with polar groups and is used to bond the outer layer I and the inner layer II.

[0013] In some embodiments of the multilayer composite pipeline material provided by the present invention, the molecular weight (Mw) of the copolymer polyethylene (B1) is 150,000 to 400,000 (e.g., 160,000, 180,000, 200,000, 250,000, 300,000, 350,000), and the molecular weight distribution is 10 to 25 (e.g., 11, 12, 14, 16, 18, 20, 22, 24).

[0014] In some embodiments, the copolymer polyethylene (B1) has a melt index of 0.2–1.5 g / 10 min at 190°C and 5 kg, for example, 0.3 g / 10 min, 0.4 g / 10 min, 0.5 g / 10 min, 0.8 g / 10 min, 1.0 g / 10 min, or 1.2 g / 10 min, and a density of 0.93–0.97 g / cm³. 3 (For example, 0.94 g / cm) 3 0.95g / cm 3 0.96g / cm 3 Crystallinity <70% (e.g., 10%, 20%, 30%, 50%, 60%, 65%), melting point 120–140°C (e.g., 125°C, 130°C).

[0015] In some embodiments, the copolyethylene (B1) is a copolymer formed from one or more of ethylene and α-olefins. The introduction of comonomers enhances the entanglement of material segments, promoting the formation of ligand molecules.

[0016] In some embodiments, the α-olefin is selected from C2 to C12 olefin monomers, preferably from C4 to C8 olefin monomers (such as 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene).

[0017] The long-term performance of copolymer polyethylene materials is determined by both the amorphous and crystalline regions. From a microscopic perspective, preventing performance degradation primarily stems from the entanglement between the crystalline and amorphous regions. When the entangled network formed by branched molecules in the crystalline and amorphous regions becomes complete, its long-term performance is superior. During long-term use, the lamellae are connected by ligand molecular chains in the amorphous regions. When adjacent lamellae are subjected to external tensile forces, the ligand molecular chains generate sufficient internal stress to resist the external force, thus hindering deformation and further decomposition. At this point, the material is less prone to chain breakage due to the disentanglement of molecular chains. During the propagation of crazes into cracks in copolymer polyethylene materials, the internal stress generated by the ligand molecular chains resists the external stress on the lamellae. Under continuous external stress, the lamellae and ligand molecular chains form a macromolecular network to resist overall deformation and damage. Finally, the macromolecular network relaxes beyond its stress tolerance, leading to a decrease in mechanical properties. Therefore, the key to the long-term performance of copolymer polyethylene materials lies in the molecular connections between the lamellae.

[0018] The connections between lamellar crystals rely on ligand molecules. The stress that these ligand molecular chains can withstand depends on their quantity and distribution, which in turn reflects the overall molecular weight and molecular weight distribution width of the material. Compared to conventional polyethylene or polypropylene, the inventors chose copolymer polyethylene and utilized its wide molecular weight distribution, containing both macromolecular and small molecular weight segments. The small molecular weight segments act as the flow mechanism for the macromolecular segments, improving the polymer's processability while maintaining mechanical properties. In other words, this improves both the material's performance and processability during processing, resulting in a typical bimodal or trimodal molecular weight distribution.

[0019] In some embodiments, the content of copolymer monomers in the copolymer polyethylene (B1) is 1 to 5 wt% (e.g., 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, 4.0 wt%, 4.5 wt%) based on the total weight of the copolymer polyethylene (B1).

[0020] In some embodiments, the content of the copolyethylene (B1) ranges from 80 to 99 wt% based on the total weight of the polyolefin composition (B), for example, 82 wt%, 85 wt%, 90 wt%, 95 wt%, 98 wt%.

[0021] In some embodiments, the polyolefin composition (B) further includes the following components:

[0022] Antioxidant (B2), 0.3–1.2 wt% (e.g., 0.4 wt%, 0.6 wt%, 0.8 wt%, 1.0 wt%);

[0023] Lubricant (B3), 0–0.5 wt% (e.g., 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%);

[0024] Filler (B4), 0–15 wt% (e.g., 0.5 wt%, 1 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%);

[0025] Other adjuvants (B5), 0–15 wt% (e.g., 0.5 wt%, 1 wt%, 4 wt%, 8 wt%, 12 wt%).

[0026] The multilayer composite pipe material described in this invention will be used in various environments (such as resistance to long-term aging, water resistance, and alcohol resistance). The selection of the heat aging agent needs to ensure its long-term continuous function and prevent precipitation in the medium (such as coolant) to achieve superior long-term performance. Although antioxidants are conventional additives that can be added to polyolefin matrices, not all antioxidants can achieve the objectives of this invention.

[0027] In some embodiments, the antioxidant (B2) is a precipitation-resistant antioxidant, preferably selected from one or more of aromatic amine antioxidants, sterically hindered phenolic antioxidants, sulfur-containing synergists, and hydroxylamine benzofuranone derivatives. For example, it may be antioxidant 1330, antioxidant 1790, Irganox 1098, or Irganox 168.

[0028] In some embodiments, the lubricant (B3) is selected from one or more of titanate, stearic acid, erucamide, oleamide and silicone.

[0029] In some embodiments, the filler (B4) is selected from inorganic or organic fillers, preferably from one or more of silica, talc, wollastonite and calcium carbonate.

[0030] Other additives (B5) may include, but are not limited to, one or more of flame retardants, ultraviolet absorbers, pigments, leveling agents, chain extenders, thermally conductive agents, conductive additives, and toughening agents (such as POE). These additives are all conventional additives in the art and will not be described in detail here. In some embodiments, the other additives (B5) are selected from one or more of photoaging agents, leveling agents, and toughening agents.

[0031] For example, the ultraviolet absorber mainly includes one or more of benzoic acid, benzophenone derivatives, and benzotriazole, and the light stabilizer mainly includes hindered amine stabilizers. The two can be used in combination at a weight ratio of 0.5 to 2:1.

[0032] The semi-crystalline polyamide in layer I can be prepared by diamine and dicarboxylic acid or by aminocarboxylic acid or the corresponding lactam. The semi-crystalline polyamide resin prepared by lactam has at least 8 carbon atoms per nitrogen atom, and in the case of a combination of diamine and dicarboxylic acid, the arithmetic mean of the carbon atoms in the mixed component of the diamine and dicarboxylic acid is at least 8.

[0033] Suitable examples of semi-crystalline polyamides include, but are not limited to: PA1012 (prepared from decanediamine with 10 carbon atoms and dodecanoic acid with 12 carbon atoms), PA12 (dodecanoic acid condensation), PA612, PA610, PA614, PA12, PA11, PA1212, PA614, PA616, PA618, and one or more thereof. For example, Wanamid L3000 and Wanamid L2000.

[0034] In some embodiments of the multilayer composite pipeline material provided by the present invention, the semi-crystalline polyamide (Al) is selected from one or more of PA1012, PA12, PA612, PA610, PA614, PA12, PA1212, PA614, PA616 and PA618.

[0035] In some embodiments, the content of the semi-crystalline polyamide (A1) is ≥50 wt% (e.g., 55 wt%, 60 wt%, 75 wt%, 85 wt%, 95 wt%), preferably 70 to 99 wt%, and more preferably 80 to 99 wt%, based on the total weight of the polyamide composition (A).

[0036] In some embodiments, the polyamide composition (A) further includes one or more of an impact modifier (A2), a plasticizer (A3), and an additive component (A4).

[0037] In some embodiments, based on the total weight of the polyamide composition (A), wherein:

[0038] The impact modifier (A2) is present in a content of 0 to 25 wt% (e.g., 0.5 wt%, 1 wt%, 4 wt%, 5 wt%, 10 wt%, 12 wt%, 15 wt%), preferably 3 to 20 wt%, more preferably 3 to 10 wt%.

[0039] The content of the plasticizer (A3) is 0 to 20 wt% (e.g., 0.5 wt%, 1 wt%, 4 wt%, 10 wt%, 18 wt%), preferably 1 to 15 wt%, more preferably 2 to 12 wt%.

[0040] The content of the additive component (A4) is 0 to 5 wt% (e.g., 0.5 wt%, 1.5 wt%, 2 wt%, 4 wt%), preferably 1 to 3 wt%.

[0041] In some embodiments, the impact modifier (A2) is an elastomer copolymer, preferably selected from one or more of ethylene / butene copolymers, ethylene / hexene copolymers, ethylene / octene copolymers, ethylene / (meth)acrylate alkyl ester copolymers, ethylene / styrene / butadiene copolymers, styrene / butadiene and ethylene-propylene two- or three-block copolymers.

[0042] The impact modifier (A2) is a modified copolymer, and the optional modified functional groups include one or more of acid anhydrides, epoxy groups, halogens, carboxyl groups, amino groups, and hydroxyl groups and their derivatives. Suitable examples include, but are not limited to, N493 (grafted maleic anhydride), SOG-03 (a grafted polymer containing GMA functional groups, grafted with epoxy groups), and MD715 (grafted maleic anhydride). In some embodiments, the elastomeric polymer contains polar functional groups, which are preferably selected from one or more of acid anhydrides, epoxy groups, halogens, carboxyl groups, amino groups, and hydroxyl groups and their derivatives.

[0043] The plasticizer (A3) may be a C1-C20 ester of p-hydroxybenzoic acid or an amide formed by an aryl sulfonic acid and a C2-C12 amine. Suitable examples include, but are not limited to, one or more of p-benzenesulfonamide, N-butylbenzenesulfonamide (BBSA), methyl p-hydroxybenzoate, N-methylbenzenesulfonamide, ethyl p-hydroxybenzoate, octyl p-hydroxybenzoate, p-isohexadecyl p-hydroxybenzoate, toluenesulfonic acid-n-octylamide, benzenesulfonic acid-n-butylamide, and benzenesulfonic acid-2-ethylhexylamide.

[0044] The additive component (A4) may include, but is not limited to, one or more of antioxidants, ultraviolet absorbers, light stabilizers, lubricants, flame retardants, pigments, leveling agents, chain extenders, thermal conductive agents, conductive additives, and other thermoplastics.

[0045] For example, the ultraviolet absorber mainly includes one or more of benzoic acid, benzophenone derivatives, and benzotriazole; the light stabilizer mainly includes hindered amine stabilizers, and the two can be used in combination at a weight ratio of 0.5 to 2:1.

[0046] For example, the lubricant may be one or more of calcium stearate, zinc stearate, polyethylene wax, and ethylene distearate amine.

[0047] For example, the antioxidant may include antioxidants used alone or mixtures of antioxidants used in combination; as a specific embodiment, the antioxidant may include one or more of phenolic antioxidants, phosphites, cuprous iodide (CuI), and potassium iodide (KI).

[0048] In some embodiments of the multilayer composite pipeline material provided by the present invention, the polar groups serving as modified functional groups in the modified polyolefin material (C) are selected from one or more of acid anhydrides, carboxyl groups, amino groups, hydroxyl groups, and their derivatives.

[0049] In some embodiments, the content of the polar group ranges from 0.1 to 2.0 wt% (e.g., 0.15 wt%, 0.3 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 1.8 wt%).

[0050] Layer III is a modified polyolefin material (C), which is obtained by modifying branched or unbranched C2 to C12 olefins or mixtures thereof, and can be selected from polyethylene, polypropylene, etc. The modified polyolefin material can be obtained by modifying at least one monomer selected from the following: maleic anhydride, glycidyl acrylate, glycidyl methacrylate, acrylic acid, methacrylic acid, and vinyl acetate through grafting or copolymerization modification. Using a polar monomer-modified polyolefin material as an adhesive layer ensures both the inner and outer layers are bonded. The inner layer achieves chemical bonding through the segmental entanglement between the modified polyolefin materials and the common polarity of the olefin polymers. The outer layer material achieves chemical bonding through the grafted polar functional groups and the polyamide composition, thereby achieving bonding of the three layers and improving the formability of the multilayer composite pipeline.

[0051] According to the multilayer composite pipe material provided by the present invention, in some embodiments, the outer diameter of the multilayer composite pipe material is 4-30 mm (e.g., 5 mm, 10 mm, 15 mm, 20 mm, 25 mm), preferably 8-24 mm; the wall thickness is 0.6-3 mm (e.g., 0.8 mm, 1.2 mm, 1.5 mm, 2.2 mm, 2.5 mm), preferably 1-2 mm; wherein:

[0052] The outer layer I made of the polyamide composition (A) has a wall thickness of no more than 80% (e.g., 10%, 25%, 40%, 60%, 75%) of the total wall thickness of the multilayer composite pipe material, preferably 20-70% of the total wall thickness of the multilayer composite pipe material, and more preferably 30-50% of the total wall thickness of the multilayer composite pipe material.

[0053] The modified polyolefin material (C) serves as the adhesive layer III, and its wall thickness does not exceed 20% of the total wall thickness of the multilayer composite pipe material (e.g., 1%, 4%, 8%, 12%, 15%, 18%), preferably 10-20% of the total wall thickness of the multilayer composite pipe material.

[0054] In some embodiments, the multilayer composite pipe material is an oriented smooth multilayer pipe with a draw ratio in the extrusion direction of less than 1:5 (e.g., 1:1, 1:2, 1:2.5, 1:3, 1:3.5, 1:4.5), preferably 1:1.5 to 1:4. In this text, the draw ratio of less than 1:5 means that "1" represents the cross-sectional area of ​​the pipe end after extrusion, and "5" represents the cross-sectional area of ​​the pipe at the die head of the multilayer co-extrusion equipment immediately after extrusion.

[0055] In a second aspect, a method for preparing the multilayer composite pipeline material as described above is provided, wherein the polyamide composition (A) is used as the outer layer, the polyolefin composition (B) is used as the inner layer, and the modified polyolefin material (C) is used as the intermediate layer for bonding the outer and inner layers, and the pipeline is formed by using a multilayer co-extrusion device to obtain the multilayer composite pipeline material.

[0056] In this invention, both the polyamide composition (A) and the polyolefin composition (B) can be granulated using a screw extrusion process. The extrusion equipment and extrusion process are conventional choices in the art and will not be described in detail here. Similarly, the multilayer co-extrusion equipment and multilayer co-extrusion process involved are also conventional choices in the art and will not be described in detail here.

[0057] In the preparation method of the multilayer composite pipeline material, for example, the wall thickness of each layer and the total wall thickness of the multilayer composite pipeline can be controlled by the extrusion amount of each layer of material during the extrusion process.

[0058] During the extrusion process, smooth tubes, corrugated tubes, and shaped tubes can be extruded to meet different application requirements. The multi-layer composite pipeline of this invention can be applied to fluid transportation pipelines, such as cooling pipes, drainage pipes, pneumatic brake pipes, oil pipelines, and other media-resistant pipelines.

[0059] The multilayer composite pipeline material of this invention can achieve a multilayer structure through co-extrusion. A composition containing copolymer polyethylene is selected as the inner layer of the multilayer structure. Through the structural characteristics of the copolymer polyethylene itself and improvements in its performance, it possesses both long-term heat resistance and media resistance, giving the multilayer composite pipeline material performance advantages in certain application scenarios. The outer layer is made of polyamide material. Semi-crystalline polyamide itself has excellent strength and low-temperature toughness, which provides good protection for the entire multilayer composite pipeline. Simultaneously, combined with a preferred pipeline stretch ratio, a certain degree of orientation can be achieved by controlling the stretch ratio. A suitable stretch ratio is beneficial for refining the crystals in the system during the extrusion process, improving material performance (such as good performance in hydrolysis resistance and long-term temperature resistance), and also helps to achieve a stable extrusion process (focusing on the dimensional and appearance stability of the pipeline material).

[0060] Compared with existing technologies, the beneficial effects of the technical solution of this invention are as follows:

[0061] By setting up a layered structure for the multi-layer composite pipeline and selecting suitable materials for each layer based on this structure, and combining it with a suitable pipeline stretch ratio, the resulting three-layer composite pipeline material can have excellent high-temperature resistance, hydrolysis resistance, long-term service performance, good resistance to media (coolant), and excellent low-temperature toughness.

[0062] Using polyolefin composition (B) as the inner layer of the pipeline and polyamide composition (A) as the outer layer, the polyolefin composition (B) contains a copolymer polyethylene component with a wide molecular weight distribution, high content of comonomers and many macromolecular chain segments, which can improve the long-term performance of the pipeline material. At the same time, the pipeline is subjected to a suitable stretch ratio during the extrusion process, which makes the crystals of the material refined and plays a positive role in improving the overall performance of the material.

[0063] The outer aliphatic polyamide material, due to its long chain structure, has a low amide bond density, which gives the material excellent resistance to environmental corrosion, salt spray, and gravel impact. The pipeline material prepared can ensure that it can meet the application requirements in different environments.

[0064] By introducing a polar group-modified polyolefin material (C) as a bonding layer, the microscopic bonding force between the layers is improved through the entanglement of polymer material cooling segments and the improvement of polar functional groups, thereby achieving effective bonding between the inner and outer layers and preventing separation during pipeline use. Detailed Implementation

[0065] 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 of the invention 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.

[0066] <Source of Raw Materials>

[0067] The sources of the main raw materials used in each embodiment are shown in Table 1.

[0068] Table 1 Sources of main raw materials

[0069]

[0070]

[0071] An example of preparing copolymer polyethylene is shown below:

[0072] The copolymer polyethylene (B1) matrix resin contained in the polyolefin composition (B) of the present invention can be prepared by a multi-stage copolymerization method, that is, in the corresponding reactors at each stage, the reaction product (containing a catalyst) of the previous stage is transferred to the reactor of the next stage of reaction to continue the reaction.

[0073] In the reactors at each stage, different reaction conditions, material addition ratios, or material types are configured to prepare ethylene copolymers containing two or more components. Specific reactants and reaction conditions are shown in Table 2.

[0074] Table 2. Reactants and reaction conditions for copolyethylene.

[0075]

[0076]

[0077] The properties of the copolymer polyethylene (B1) prepared by the above method are shown in Table 3 below.

[0078] Table 3 shows the properties of the obtained copolymer polyethylene.

[0079] Preparation Example molecular weight Molecular weight distribution Types of comonomers Comonomer content, wt% PE-a 150000 10 Hexene 1 PE-b 400000 25 Hexene 5 PE-c 250000 15 Hexene 3 PE-d 250000 15 Butene 3 PE-e 250000 15 Hexene and Butene 3 PE-f 250000 25 Hexene 4 PE-g 250000 15 none none

[0080] Preparation of polyolefin composition (B)

[0081] The copolymer polyethylene (B1) matrix resin obtained by the above preparation method, along with other components, were weighed according to the component types and dosages (parts by weight) shown in Table 4. The raw materials were mixed in a high-speed mixer for 5 minutes, and the mixed blend was extruded and granulated through a twin-screw extruder. The twin-screw extruder had a screw diameter of 35 mm, an extrusion screw length-to-diameter ratio of 48, and an extrusion speed of 450 rpm / min.

[0082] The polyolefin composition (B) as the inner layer is obtained by processing and granulation using a twin-screw extruder, and the products are labeled as PE1# to PE8# respectively.

[0083] Table 4. Types and proportions (parts by weight) of components in polyolefin composition (B)

[0084] category PE1# PE2# PE3# PE4# PE5# PE6# PE7# PE8# PE-a 98 PE-b 98 PE-c 93 PE-d 98 98 PE-e 98 PE-f 90 PE-g 98 Engage 7467 8 <![CDATA[SiO2]]> 5 1330 0.3 0.3 0.3 0.3 0.3 0.3 0.3 1790 0.3 0.3 0.3 0.3 0.3 0.3 0.3 1010 0.3 UV770 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Irganox 168 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Black mother 1 1 1 1 1 1 1 1

[0085] Preparation of polyamide composition (A)

[0086] The polyamide composition (A) serving as the outer layer comprises the components shown in Table 5 below. Raw materials are weighed according to the components and proportions (parts by weight) in Table 5, mixed in a high-speed mixer for 5 minutes to ensure uniform mixing, and the resulting blend is extruded and granulated using a twin-screw extruder with a screw diameter of 28 mm, a length-to-diameter ratio of 40, and an extrusion speed of 700 rpm / min. The polyamide composition (A) serving as the outer layer is obtained through extrusion processing, and the products are labeled as PA1# to PA3#.

[0087] Table 5. Components and their amounts (parts by weight) of polyamide composition (A)

[0088] PA1# PA2# PA3# Wanamid L3000 98.3 85.3 DMVO 87.3 Butylbenzenesulfonamide 8 8 FUSABOND N493 5 3 Irganox 1098 0.3 0.3 0.3 Irganox 168 0.2 0.2 0.2 Zinc stearate 0.2 0.2 0.2 Black mother 1 1 1

[0089] Fabrication of multilayer composite pipelines

[0090] Using the polyolefin composition (B) prepared above as the inner layer, the polyamide composition (A) as the outer layer, and the modified polyolefin material (C) as the intermediate layer, a multilayer composite pipeline was formed by multilayer co-extrusion equipment. The structure and performance tests of each layer are shown in Table 7. The outer diameter of the pipeline is 8 mm, and the wall thickness is 1 mm.

[0091] The extrusion line speed of the multi-layer co-extrusion equipment is 12 m / min. The processing temperatures of each zone in the multi-layer co-extrusion equipment are shown in Table 6 below (unit: °C):

[0092]

[0093] Note: In the table above, Z represents the screw and H represents the head.

[0094] Table 7. Test data on the structure and performance of each layer of the multilayer composite pipeline.

[0095]

[0096] Note: The low-temperature impact toughness test procedure involves randomly selecting 10 sample tubes for a drop ball impact test. In the table, x / 10 represents the number of tubes that failed out of the 10 tubes; for example, 0 / 10 means that 0 out of the 10 tubes failed, and all 10 tubes passed the test.

[0097] The results from Examples 1-8 show that by setting the layer structure of the multilayer composite pipeline and selecting the appropriate material types for different layers based on this layer structure, combined with a suitable pipeline stretching ratio, the resulting three-layer composite pipeline material (after initial performance testing) can exhibit good strength and low-temperature impact toughness. After being treated at 100°C for 1000 hours in a coolant environment, the tensile strength and impact toughness of the pipeline remain good, with minimal performance degradation, demonstrating the excellent high-temperature resistance, long-term performance, and good resistance to media (coolant) of the multilayer pipeline material.

[0098] Compared with Examples 2 and 4, Comparative Examples 1-2 used polyethylene components not limited to those of this invention as the inner layer of the pipe. Under the same processing conditions, the initial tensile properties of the resulting multilayer pipes were lower, and some pipes were found to be broken in the low-temperature toughness test. Furthermore, after long-term treatment with coolant, the number of broken pipes in the low-temperature toughness test increased further. This indicates that the initial tensile strength and low-temperature toughness of the multilayer pipe materials in Comparative Examples 1-2 are poor, and after being treated at 100°C for 1000 hours in a coolant environment, the impact toughness of the pipes further decreased. They do not possess high-temperature resistance, long-term use performance, or good resistance to media (coolant), demonstrating the advantages of the copolymer polyethylene type selected in this invention.

[0099] Compared with Example 3, the stretching ratio of Comparative Example 3 is 1:6, which results in a lower initial tensile strength of the pipeline. After long-term coolant treatment, the tensile strength of the pipeline decreases more severely. This indicates that the stretching ratio specified in this invention is more conducive to maintaining the mechanical properties of the pipeline material and has better resistance to media and long-term use.

[0100] Compared with Example 4, although the initial performance of the pipeline obtained in Comparative Example 4 is basically the same, the tensile strength and low-temperature toughness of the pipeline obtained in Comparative Example 4 decreased significantly after long-term coolant treatment because antioxidant 1010 was used. This shows that the antioxidant type preferred by the present invention has a great advantage for the long-term performance of the pipeline and good resistance to media (coolant).

[0101] Some embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A multilayer composite tubing material, characterized by, It comprises the following layers: I. an outer layer made of a polyamide composition (A) comprising at least one semi-crystalline polyamide (A1) having an average number of carbon atoms per nitrogen atom Nc in the range of 8 to 18; II. an inner layer made of a polyolefin composition (B) comprising at least one copolymer polyethylene (B1) in an amount in the range of 80 to 99 wt.-%, based on the total weight of the polyolefin composition (B), said copolymer polyethylene (B1) having a crystallinity < 70 % and a melting point in the range of 120 to 140 °C, and said copolymer polyethylene (B1) having a comonomer content in the range of 1 to 5 wt.-%, based on the total weight of the copolymer polyethylene (B1); III. a modified polyolefin material (C) as an adhesive layer, which is an olefin polymer modified with polar groups in an amount in the range of 0.1 to 2.0 wt.-%, for the adhesion of the outer layer I to the inner layer II; the outer layer I made of a polyamide composition (A) has a wall thickness in the range of 30 to 50 % of the total wall thickness of the multilayer pipe material; the multilayer pipe material is an oriented smooth multilayer pipe having a draw ratio in the range of 1 : 1.5 to 1 : 4 in the extrusion direction.

2. The multi-layer composite tubing material of claim 1, wherein, the copolymer polyethylene (B1) has a molecular weight in the range of 150000 to 400000 and a molecular weight distribution in the range of 10 to 25; and / or The melt index of the copolymer polyethylene (B1) is 0.2 to 1.5 g / 10 min (190°C, 5 kg), and the density is 0.93 to 0.97 g / cm 3 ; and / or the copolymer polyethylene (B1) is a copolymer of ethylene and one or more a-olefins.

3. The multi-layer composite tubing material of claim 2, wherein, the a-olefins are selected from the group consisting of C2 to C12 olefin monomers.

4. The multi-layer composite tubing material of claim 2, wherein the a-olefins are selected from the group consisting of C4 to C8 olefin monomers.

5. The multilayer composite tubing material of claim 1, wherein the polyolefin composition (B) further comprises the following components, based on the total weight of the polyolefin composition (B): 0.3 to 1.2 wt.-% of an antioxidant (B2), 0 to 0.5 wt.-% of a lubricant (B3), 0 to 15 wt.-% of a filler (B4), 0 to 15 wt.-% of further auxiliaries (B5).

6. The multilayer pipe material according to claim 5, wherein the antioxidant (B2) is a non-extractable antioxidant selected from the group consisting of aromatic amine antioxidants, sterically hindered phenol antioxidants, sulfur containing synergists and hydroxylamine benzofuranone derivatives; the lubricant (B3) is selected from the group consisting of one or more of titanates, stearic acid, erucamide, oleamide and silicone; the filler (B4) is selected from the group consisting of one or more of silica, talc, wollastonite and calcium carbonate; the further auxiliaries (B5) are selected from the group consisting of one or more of light stabilizers, leveling agents and flexibilizers.

7. The multilayer composite tubing material of claim 1, wherein the semi-crystalline polyamide (A1) is selected from the group consisting of one or more of PA1012, PA12, PA612, PA610, PA614, PA12, PA1212, PA614, PA616 and PA618; and / or the semi-crystalline polyamide (A1) is present in an amount of > 50 wt.-%, based on the total weight of the polyamide composition (A).

8. The multi-layer composite tubing material of claim 7, wherein, the semi-crystalline polyamide (A1) is present in an amount in the range of 70 to 99 wt.-%, based on the total weight of the polyamide composition (A).

9. The multi-layer composite tubing material of claim 7, wherein, The content of the semi-crystalline polyamide (A1) is 80 to 99 wt.-%, based on the total weight of the polyamide composition (A).

10. The multilayer composite tubing material of claim 1, wherein The average number of carbon atoms per nitrogen atom Nc of the semi-crystalline polyamide (A1) is between 9 and 12.

11. The multilayer composite tubing material of claim 1, wherein The polyamide composition (A) further comprises one or more of an impact modifier (A2), a plasticizer (A3) and an additive component (A4); and / or The content of the semi-crystalline polyamide (A1) is 80 to 99 wt.-%, based on the total weight of the polyamide composition (A). The content of the impact modifier (A2) is 0 to 25 wt.-%, based on the total weight of the polyamide composition (A). The content of the plasticizer (A3) is 0 to 20 wt.-%, based on the total weight of the polyamide composition (A). The content of the additive component (A4) is 0 to 5 wt.-%, based on the total weight of the polyamide composition (A).

12. The multi-layer composite tubing material of claim 11, wherein, The content of the impact modifier (A2) is 3 to 20 wt.-%, based on the total weight of the polyamide composition (A). The content of the plasticizer (A3) is 1 to 15 wt.-%, based on the total weight of the polyamide composition (A). The content of the additive component (A4) is 1 to 3 wt.-%, based on the total weight of the polyamide composition (A). The content of the impact modifier (A2) is 3 to 10 wt.-%, based on the total weight of the polyamide composition (A).

13. The multi-layer composite tubing material of claim 11, wherein The content of the plasticizer (A3) is 2 to 12 wt.-%, based on the total weight of the polyamide composition (A).

14. The multi-layer composite tubing material of claim 11, wherein, The impact modifier (A2) is an elastomeric copolymer; 15. The multi-layer composite tubing material of claim 11, wherein, The elastomeric copolymer comprises polar functional groups selected from one or more of anhydride, epoxy group, halogen, carboxyl, amino and hydroxyl groups and derivatives thereof. The impact modifier (A2) is selected from one or more of ethylene / butene copolymer, ethylene / hexene copolymer, ethylene / octene copolymer, ethylene / alkyl (meth)acrylate copolymer, ethylene / styrene / butadiene copolymer, styrene / butadiene and di- or tri-block copolymer of ethylene-propylene.

16. The multi-layer composite tubing material of claim 15, wherein The polar groups as modifying functional groups in the modified polyolefin material (C) are selected from one or more of anhydride, carboxyl, amino and hydroxyl groups and derivatives thereof.

17. The multilayer composite tubing material of claim 1, wherein The multi-layer composite pipe material has an outer diameter of 4 to 30 mm and a wall thickness of 0.6 to 3 mm; wherein:

18. The multi-layer composite tubing material of claim 1, wherein, The modified polyolefin material (C) as tie layer III has a wall thickness of not more than 20 % of the total wall thickness of the multi-layer composite pipe material. The modified polyolefin material (C) as tie layer III has a wall thickness of 10 to 20 % of the total wall thickness of the multi-layer composite pipe material.

19. The multi-layer composite tubing material of claim 18, wherein, The multi-layer composite pipe material is produced by pipe forming processing of the polyamide composition (A) as outer layer, the polyolefin composition (B) as inner layer and the modified polyolefin material (C) as intermediate layer bonding the outer and inner layers, by means of a multi-layer co-extrusion device.

20. The method of making a multi-layer composite tubing material of any one of claims 1-19, wherein, ​

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