Multilayer composite piping material and its manufacturing method

Abstract

A multilayer composite piping material and a method for producing the same, the piping material comprising I) an outer layer made of a polyamide composition (A) containing at least one semicrystalline polyamide (A1), II) an inner layer made of a polyolefin composition (B) containing at least one copolymerized polyethylene (B1), and III) an adhesive layer made of a modified polyolefin material (C), which is an olefin polymer modified with a polar group, for adhering the outer layer I and the inner layer II. The multilayer composite piping material has excellent high-temperature resistance and long-term usability, high strength and low-temperature toughness, and good chemical resistance, and can be processed into piping of various shapes, expanding the range of uses for piping.

Description

[Technical Field]

[0001] The present invention relates to the technical field of multilayer pipes, and more particularly to a multilayer composite piping material and a method for manufacturing the same. [Background technology]

[0002] Currently, the materials used for automotive cooling pipes are generally EPDM, TPV, and nylon 12. Cooling pipes made of rubber generally have a wall thickness of 4 mm or more. When used in automobiles, these pipes increase the weight of the entire piping system and are prone to deterioration after long-term use, significantly increasing the fuel efficiency and power consumption per 100 kilometers of the automobile. In addition, they occupy a very large amount of space, which is unfavorable for the layout of cooling pipes. Furthermore, cooling pipes made of single-layer nylon 12 have certain problems with hydrolysis resistance and therefore have too high water vapor permeability, which poses certain risks for new energy vehicles.

[0003] In response to the existing deficiencies, some improvements have been attempted in this field. Patent document CN1906022A discloses a multi-layer piping structure in which the inner layer is made of a polypropylene material, the middle layer is an adhesive layer, and the outer layer is made of a polyamide material. This piping structure has high hydrolysis resistance, but the polypropylene material has low resistance to brittleness at low temperatures, so the material of the multi-layer piping has low low-temperature resistance. Furthermore, when the PP material is treated to be chemical-resistant, fine cracks occur in the molded product, which is likely to cause failure of the piping.

[0004] Patent document CN108343790A discloses a multilayer structure pipe having an inner layer of ethylene propylene diene rubber, a middle layer of ethylene propylene diene rubber modified with a polypropylene group, and an outer layer of modified nylon 12. This structure improves the wall thickness of the pipe and significantly reduces the weight of conventionally used rubber pipes. However, the burst pressure of this multilayer structure pipe is not high, and the heat resistance of the rubber material is not high, so its applications are limited.

[0005] In view of the above circumstances, there is an urgent need to develop multilayer piping for cooling systems (e.g., automobiles) that can solve the problems of existing piping, such as low high and low temperature resistance, low hydrolysis resistance, and high burst resistance. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to provide a multi-layer composite piping material and a manufacturing method thereof to address the problems existing in conventional multi-layer piping for cooling systems (e.g., automobiles). A three-layer piping structure is obtained by using a copolymerized polyethylene with a wide molecular weight distribution, a high content of copolymerizable monomers, and a large number of large molecular chain segments as the inner layer, thereby improving the high-temperature resistance and long-term usage performance of the piping. The polyamide material of the outer layer provides the piping with high strength, low-temperature toughness, and good chemical resistance. More importantly, it also increases the rupture elongation of the piping and reduces internal stress, allowing it to be processed into piping of various shapes, thereby expanding the range of uses for the piping material. [Means for solving the problem]

[0007] To achieve the above object, the present invention provides the following technical solutions.

[0008] In a first aspect, I. An outer layer made of a polyamide composition (A), wherein the polyamide composition (A) contains at least one semi-crystalline polyamide (A1), and the average number of carbon atoms Nc of each nitrogen atom is 8 to 18 (e.g., 10, 11, 14, or 16), preferably 9 to 12; II. An inner layer made of a polyolefin composition (B), wherein the polyolefin composition (B) contains at least one copolymerized polyethylene (B1); III. A multilayer composite piping material is provided, which includes an adhesive layer made of a modified polyolefin material (C), which is an olefin polymer modified with a polar group, for adhering an outer layer I and an inner layer II.

[0009] According to some embodiments of the multilayer composite piping material of the present invention, the copolymerized polyethylene (B1) has a molecular weight (Mw) of 150,000 to 400,000 (e.g., 160,000, 180,000, 200,000, 250,000, 300,000, 350,000) and a molecular weight distribution of 10 to 25 (e.g., 11, 12, 14, 16, 18, 20, 22, 24).

[0010] In some embodiments, the copolymerized polyethylene (B1) has a melt flow index at 190°C and 5 kg of 0.2 to 1.5 g / 10 min, 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 to 0.97 g / cm 3 (e.g., 0.94 g / cm 3 , 0.95g / cm 3 , 0.96g / cm 3 ), a crystallinity of <70% (e.g., 10%, 20%, 30%, 50%, 60%, 65%), and a melting point of 120 to 140°C (e.g., 125°C, 130°C).

[0011] In some embodiments, the copolymerized polyethylene (B1) is a copolymer formed from ethylene and one or more α-olefins, the introduction of a comonomer improving the entanglement of the material chain segments and promoting the formation of tie molecules.

[0012] In some embodiments, the α-olefin is selected from C2 to C12 olefin monomers, preferably C4 to C8 olefin monomers (eg, 1-butylene, 1-hexene, 4-methyl-1-pentene, 1-octene).

[0013] The long-term performance of polyethylene copolymer materials is determined jointly by the amorphous and crystalline phases. From a microscopic perspective, the avoidance of performance degradation is mainly due to the entanglement of the crystalline and amorphous phases. The more the entanglement network formed by the branched molecules in the crystalline and amorphous phases is complete, the better the long-term performance will be. During long-term use, the lamellar crystals are connected by tie molecular chains in the amorphous regions. When two adjacent lamellar crystals are subjected to external stretching, the tie molecular chains generate sufficient internal stress to resist the external force on the lamellar crystals, further preventing the lamellar crystals from deforming or further decomposing. At this time, the material will not easily break due to the disentanglement of the molecular chains. In polyethylene copolymer materials, during the process of craze growth into cracks, the internal stress generated in the tie molecular chains resists the external stress experienced by the lamellar crystals. Under the continuous action of external stress, the lamellar crystals and the tie molecular chains form a large molecular network to resist overall deformation and destruction. Eventually, the large molecular network exceeds the stress range it can withstand and relaxes, resulting in a decline in mechanical performance. Therefore, the key to the long-term use performance of polyethylene copolymer materials lies in the molecular connections between the lamellar crystals.

[0014] The connection between the lamellar crystals depends on the tie molecules, and the magnitude of the stress that the tie molecule chains can withstand is related to their number and distribution, which in turn indicates the molecular weight and width of the molecular weight distribution of the entire material. Compared to conventional polyethylene or polypropylene, the inventors have selected copolymerized polyethylene, which takes advantage of its wide molecular weight distribution and contains large and small molecular chain segments. The small molecular chain segments play a role in the fluidity of the large molecular chain segments, which can improve the processability of the polymer while taking into account the mechanical performance. That is, during material processing, not only the performance of the material but also the processability is improved, and the molecular weight distribution shows a typical bimodal or trimodal distribution.

[0015] In some embodiments, the content of the copolymerized monomer in the copolymerized 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 %) relative to the total weight of the copolymerized polyethylene (B1).

[0016] In some embodiments, the content of the copolymerized polyethylene (B1) is in the range of 80-99 wt%, for example, 82 wt%, 85 wt%, 90 wt%, 95 wt%, or 98 wt%, based on the total weight of the polyolefin composition (B).

[0017] In some embodiments, the polyolefin composition (B) comprises: 0.3 to 1.2 wt% (e.g., 0.4 wt%, 0.6 wt%, 0.8 wt%, 1.0 wt%) of an antioxidant (B2); 0 to 0.5 wt% (e.g., 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%) of a lubricant (B3); 0 to 15 wt% (e.g., 0.5 wt%, 1 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%) of filler (B4); and further comprising 0 to 15 wt% (for example, 0.5 wt%, 1 wt%, 4 wt%, 8 wt%, 12 wt%) of other auxiliary agents (B5).

[0018] The multilayer composite piping material of the present invention is used in various environments (e.g., long-term deterioration resistance, water resistance, alcohol resistance, etc.), and the thermal degradation inhibitor selected must be able to continuously exert its effect over a long period of time and not precipitate in the medium (e.g., coolant), thereby achieving better long-term use performance.Antioxidants can be added to the polyolefin matrix as conventional additives, but not all antioxidants can achieve the objectives of the present invention.

[0019] In some embodiments, the antioxidant (B2) is a precipitation-resistant antioxidant, preferably one or more selected from aromatic amine antioxidants, sterically hindered phenol antioxidants, sulfur-containing synergists, and hydroxylamine benzofuranone derivatives, such as Antioxidant 1330, Antioxidant 1790, Irganox 1098, and Irganox 168.

[0020] In some embodiments, the lubricant (B3) is one or more selected from titanate esters, stearic acid, erucamide, oleamide, and silicones.

[0021] In some embodiments, the filler (B4) is selected from inorganic or organic fillers, preferably one or more selected from silicon dioxide, talc, wollastonite, and calcium carbonate.

[0022] The other additives (B5) may include, but are not limited to, one or more of a flame retardant, an ultraviolet absorber, a pigment, a leveling agent, a chain extender, a thermal conductive agent, an electrically conductive additive, and a toughness improver (e.g., POE, etc.). These additives are common additives in the art, and detailed descriptions of them are omitted here. In some embodiments, the other additives (B5) are one or more selected from a photoaging inhibitor, a leveling agent, and a toughness improver.

[0023] For example, the ultraviolet absorber mainly includes one or more of benzoic acid-based, benzophenone derivatives, and benzotriazoles, and the light stabilizer mainly includes hindered amine-based stabilizers, and the two can be used in combination at a weight ratio of 0.5 to 2:1.

[0024] The semi-crystalline polyamide in Layer I can be made from a diamine and a dicarboxylic acid, or from an aminocarboxylic acid or the corresponding lactam. In semi-crystalline polyamide resins made from lactams, each nitrogen atom contains at least 8 carbon atoms, and in the case of a combination of a diamine and a dicarboxylic acid, the arithmetic average number of carbon atoms in the combined components of the diamine and the dicarboxylic acid is at least 8.

[0025] Examples of suitable semi-crystalline polyamides include, but are not limited to, one or more of PA1012 (made from decamethylenediamine having 10 carbon atoms and dodecanedioic acid having 12 carbon atoms), PA12 (condensation polymerization of dodecane lactam), PA612, PA610, PA614, PA11, PA1212, PA614, PA616, and PA618, for example, Wanamid L3000, Wanamid L2000, etc.

[0026] In some embodiments of the multilayer composite piping material according to the present invention, the semi-crystalline polyamide (A1) is one or more selected from PA1012, PA12, PA612, PA610, PA614, PA1212, PA614, PA616, and PA618.

[0027] In some embodiments, the content of the semi-crystalline polyamide (A1) relative to the total weight of the polyamide composition (A) is ≧50 wt % (e.g., 55 wt %, 60 wt %, 75 wt %, 85 wt %, 95 wt %), preferably 70 to 99 wt %, more preferably 80 to 99 wt %.

[0028] In some embodiments, the polyamide composition (A) further comprises one or more of an impact modifier (A2), a plasticizer (A3), and an additive component (A4).

[0029] In some embodiments, based on the total weight of the polyamide composition (A), The content of the impact modifier (A2) is 0 to 25 wt% (for example, 0.5 wt%, 1 wt%, 4 wt%, 5 wt%, 10 wt%, 12 wt%, or 15 wt%), preferably 3 to 20 wt%, and more preferably 3 to 10 wt%; the content of the plasticizer (A3) is 0 to 20 wt % (for example, 0.5 wt %, 1 wt %, 4 wt %, 10 wt %, or 18 wt %), preferably 1 to 15 wt %, and more preferably 2 to 12 wt %, The content of the additive component (A4) is 0 to 5 wt % (for example, 0.5 wt %, 1.5 wt %, 2 wt %, 4 wt %), and preferably 1 to 3 wt %.

[0030] In some embodiments, the impact modifier (A2) is an elastomeric copolymer, preferably one or more selected from ethylene / butylene copolymers, ethylene / hexene copolymers, ethylene / octene copolymers, ethylene / (meth)acrylic acid alkyl ester copolymers, ethylene / styrene / butadiene copolymers, styrene / butadiene diblock / triblock copolymers, and ethylene-propylene diblock / triblock copolymers.

[0031] The impact modifier (A2) is a modified copolymer, and the selectable modifying functional groups include one or more of acid anhydride, epoxy group, halogen, carboxyl group, amino group, hydroxyl group, and derivatives thereof. Suitable examples include, but are not limited to, N493 (grafted maleic anhydride), SOG-03 (a graft polymer containing GMA functional groups, grafted epoxy group), and MD715 (grafted maleic anhydride). In some embodiments, the elastomeric copolymer contains a polar functional group, and the polar functional group is preferably one or more selected from acid anhydride, epoxy group, halogen, carboxyl group, amino group, hydroxyl group, and derivatives thereof.

[0032] The plasticizer (A3) may be a C1-C20 ester of p-hydroxybenzoic acid or an amide formed from an arylsulfonic acid and a C2-C12 amine, and suitable examples include, but are not limited to, one or more of p-benzenesulfonamide, N-butylbenzenesulfonamide (BBSA), p-hydroxybenzoic acid methyl ester, N-methylbenzenesulfonamide, p-hydroxybenzoic acid ethyl ester, p-hydroxybenzoic acid octyl ester, p-hydroxybenzoic acid-isohexadecyl ester, methylbenzenesulfonic acid-n-octylamide, benzenesulfonic acid-n-butylamide, and benzenesulfonic acid-2-ethylhexylamide.

[0033] The additive component (A4) may include, but is not limited to, one or more of antioxidants, UV absorbers, light stabilizers, lubricants, flame retardants, pigments, leveling agents, chain extenders, thermal conduction agents, conductive additives, and other thermoplastics.

[0034] For example, the ultraviolet absorber mainly includes one or more of benzoic acid-based, benzophenone derivatives, and benzotriazoles, and the light stabilizer mainly includes hindered amine-based stabilizers, and the two can be used in combination at a weight ratio of 0.5 to 2:1.

[0035] For example, the lubricant may be one or more of calcium stearate, zinc stearate, polyethylene wax, and ethylene bisstearamide.

[0036] For example, the antioxidant may include a single antioxidant or a mixture of antioxidants used in combination with each other, and in one specific embodiment, the antioxidant may include one or more of a phenolic antioxidant, a phosphite, cuprous iodide (CuI), and potassium iodide (KI).

[0037] In some embodiments of the multilayer composite piping material according to the present invention, in the modified polyolefin material (C), the polar group as the modifying functional group is one or more selected from the group consisting of an acid anhydride, a carboxyl group, an amino group, a hydroxyl group, and derivatives thereof.

[0038] In some embodiments, the content of the polar group ranges from 0.1 to 2.0 wt% (eg, 0.15 wt%, 0.3 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 1.8 wt%).

[0039] The third layer is a modified polyolefin material (C), which is modified with a branched or unbranched C2-C12 olefin or a mixture thereof, and may be selected from polyethylene, polypropylene, etc. The modified polyolefin material can be produced by grafting or copolymerizing at least one monomer selected from maleic anhydride, glycidyl acrylate, glycidyl methacrylate, acrylic acid, methacrylic acid, and vinyl acetate. The use of a polar monomer-modified polyolefin material as the adhesive layer achieves both the adhesiveness of the inner and outer layers. The inner layer achieves chemical bonding through the entanglement of chain segments between the modified polyolefin material and the shared polarity of the olefin polymer. The outer layer material achieves chemical bonding through the grafted polar functional groups and the polyamide composition, thereby achieving adhesion between the three layers of materials and improving the formability of the multilayer composite pipe.

[0040] According to the multilayer composite piping material of the present invention, in some embodiments, the outer diameter of the multilayer composite piping material is 4 to 30 mm (e.g., 5 mm, 10 mm, 15 mm, 20 mm, 25 mm), preferably 8 to 24 mm, and the wall thickness is 0.6 to 3 mm (e.g., 0.8 mm, 1.2 mm, 1.5 mm, 2.2 mm, 2.5 mm), preferably 1 to 2 mm; The thickness of the outer layer I made of the polyamide composition (A) does not exceed 80% (for example, 10%, 25%, 40%, 60%, or 75%) of the total thickness of the multilayer composite piping material, is preferably 20 to 70% of the total thickness of the multilayer composite piping material, and is more preferably 30 to 50% of the total thickness of the multilayer composite piping material; The thickness of the adhesive layer III, which is the modified polyolefin material (C), does not exceed 20% of the total thickness of the multilayer composite piping material (e.g., 1%, 4%, 8%, 12%, 15%, 18%), and is preferably 10 to 20% of the total thickness of the multilayer composite piping material.

[0041] In some embodiments, the multilayer composite piping material is an oriented, smooth, multilayer pipe, and the stretch ratio in the extrusion direction is less than 1:5 (e.g., 1:1, 1:2, 1:2.5, 1:3, 1:3.5, 1:4.5), preferably the stretch ratio in the extrusion direction is 1:1.5 to 1:4. In this specification, when the stretch ratio is less than 1:5, "1" represents the cross-sectional area of ​​the piping port after extrusion, and "5" represents the cross-sectional area of ​​the piping at the head of the multilayer coextrusion apparatus immediately after extrusion.

[0042] In a second aspect, there is provided a method for producing the above multilayer composite piping material, in which piping molding processing is carried out using a multilayer coextrusion device, with the polyamide composition (A) as an outer layer, the polyolefin composition (B) as an inner layer, and the modified polyolefin material (C) as an intermediate layer that bonds the outer layer and the inner layer, to produce a multilayer composite piping material.

[0043] In the present invention, the polyamide composition (A) and the polyolefin composition (B) can both be granulated by a screw extrusion process. The extrusion device and extrusion process are both common choices in the field, and detailed descriptions thereof are omitted here. Furthermore, the multi-layer co-extrusion device and multi-layer co-extrusion process are also common choices in the field, and detailed descriptions thereof are omitted here.

[0044] In the method for producing the multilayer composite piping material, for example, the thickness of each layer and the total thickness of the multilayer composite piping can be controlled by the amount of material extruded for each layer in the extrusion process.

[0045] In the extrusion process, smooth pipes, bellows, irregular-shaped pipes, etc. can be extruded according to various applications. The multilayer composite pipe of the present invention can be used for fluid transport pipes, such as chemical-resistant pipes for cooling pipes, drainage pipes, air brake pipes, and fuel transport pipes.

[0046] The multi-layer composite piping material described in the present invention can be achieved by co-extrusion to form a multi-layer structure. A composition containing a copolymerized polyethylene material is selected as the inner layer of the multi-layer structure. Due to the structural properties and improved performance of the copolymerized polyethylene material itself, it has both long-term heat resistance and chemical resistance, so that the multi-layer composite piping material has performance advantages in certain applications. The outer layer is selected from a polyamide material. The semi-crystalline polyamide material itself has excellent strength and low-temperature toughness, so the entire multi-layer composite piping is well protected. In addition, in combination with a suitable piping elongation ratio, a certain degree of orientation can be achieved by controlling the elongation ratio. An appropriate elongation ratio is advantageous to realize finer crystals in the material system during the extrusion process, which improves the performance of the material (for example, has excellent performance in hydrolysis resistance, long-term temperature resistance, etc.), and contributes to the stability of the extrusion process (the key is the stability of the dimensional and appearance of the piping material).

[0047] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0048] By setting the layer structure arrangement of the multilayer composite piping, selecting appropriate materials for each layer based on the layer structure arrangement, and combining them with an appropriate piping elongation ratio, the resulting three-layer composite piping material can be endowed with excellent high temperature resistance, hydrolysis resistance, long-term use performance, good chemical resistance (coolant), and excellent low-temperature toughness.

[0049] When the polyolefin composition (B) is used as the inner layer of a pipe and the polyamide composition (A) is used as the outer layer, the polyolefin composition (B) contains a copolymerized polyethylene component with a wide molecular weight distribution, a high content of copolymerization monomers, and many large molecular chain segments, which can improve the long-term use performance of the pipe material. In addition, by applying an appropriate stretching ratio during the pipe extrusion process, the crystals of the material can be made finer, contributing to improving the performance of the entire material. The aliphatic polyamide outer layer material has a low amide bond density due to its long chain structure, which gives the material excellent environmental corrosion resistance, salt fog resistance, stone impact resistance, etc., ensuring that the manufactured piping material can meet application requirements in various environments. The polar group-modified polyolefin material (C) is introduced as an adhesive layer, and the entanglement of chain segments during cooling of the polymer material and the improvement of polar functional groups increase the microscopic bonding force between the materials of each layer, thereby achieving effective adhesion between both the inner and outer layer materials and preventing separation during use of the pipe. DETAILED DESCRIPTION OF THE INVENTION

[0050] In order to allow a more detailed understanding of the technical features and contents of the present invention, the preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention will be described in the examples, it should be understood that the present invention is not limited to the embodiments described herein and can be realized in various forms.

[0051] <Origin of raw materials> The sources of the main raw materials used in each example are shown in Table 1.

[0052] [Table 1]

[0053] An example of the production of a polyethylene copolymer is as follows.

[0054] The copolymerized polyethylene (B1) matrix resin contained in the polyolefin composition (B) of the present invention can be produced by a multi-stage copolymerization method, i.e., in each corresponding reactor stage, the reaction product (including the catalyst) from the previous stage is transferred to the reactor of the next reaction stage to continue the reaction.

[0055] The reactions in each reactor were set according to different reaction conditions, different material addition ratios, or different material types to produce ethylene copolymers containing two or more components. The specific reaction materials and reaction conditions are shown in Table 2.

[0056] [Table 2]

[0057] The properties of the polyethylene copolymer (B1) produced by the above production method are shown in Table 3 below.

[0058] [Table 3]

[0059] Production of polyolefin composition (B) The raw materials for the copolymerized polyethylene (B1) matrix resin obtained by the above production method and each of the other components were weighed according to the component types and amounts (parts by weight) shown in Table 4, mixed for 5 minutes in a high-speed mixer, and the mixed blend was extruded and granulated in a twin-screw extruder. The twin-screw extruder had a screw diameter of 35 mm, a screw length ratio of 48, and an extrusion rotation speed of 450 rpm / min.

[0060] The mixture was processed and granulated using a twin-screw extruder to produce the polyolefin compositions (B) for the inner layer, and the products were designated as PE1# to PE8#, respectively.

[0061] [Table 4]

[0062] Preparation of polyamide composition (A) The polyamide composition (A) for the outer layer contains the components shown in Table 5 below. Raw materials were weighed according to the components and blending ratios (parts by weight) in Table 5 and mixed for 5 minutes in a high-speed mixer to homogeneously mix the raw materials. The mixed blend was extruded and granulated in a twin-screw extruder with a screw diameter of 28 mm, a major axis ratio of the extrusion screw of 40, and an extrusion rotation speed of 700 rpm / min. The polyamide compositions (A) for the outer layer were produced by extrusion processing, and the products were designated PA1# to PA3#, respectively.

[0063] [Table 5]

[0064] Multi-layer composite piping manufacturing The polyolefin composition (B) produced as above was used as an inner layer, the polyamide composition (A) as an outer layer, and the modified polyolefin material (C) as an intermediate layer, and the mixture was extruded using a multi-layer coextrusion device to obtain a multi-layer composite pipe, the structure and performance tests of each layer of which are shown in Table 7. The pipe had an outer diameter of 8 mm and a wall thickness of 1 mm.

[0065] The extrusion linear speed of the multi-layer co-extrusion device was 12 m / min. The processing temperatures of each zone of the multi-layer co-extrusion device are shown in Table 6 below (unit: °C).

[0066] [Table 6]

[0067] [Table 7]

[0068] As can be seen from the results of Examples 1 to 8, by designing the layer structure of a multilayer composite pipe, selecting the appropriate materials for each layer based on the layer structure, and combining it with an appropriate pipe elongation ratio, the resulting three-layer composite pipe material (which underwent initial performance testing) was endowed with high strength and low-temperature impact toughness. After treatment at 100°C for 1,000 hours in a coolant environment, the pipe's elongation strength and impact toughness were both still well maintained, with only minimal performance degradation. The multilayer pipe material exhibited excellent high-temperature resistance, long-term use performance, and good chemical (coolant) resistance.

[0069] Compared with Examples 2 and 4, Comparative Examples 1 and 2 selected a polyethylene component outside the scope of the present invention as the inner layer of the pipe, and under the same processing conditions, the initial stretchability of the manufactured multilayer pipe was somewhat low, some pipes were broken in the low-temperature toughness test, and the number of pipes broken in the low-temperature toughness test after long-term treatment with a coolant further increased. As a result, the multilayer pipe materials of Comparative Examples 1 and 2 did not have high initial stretch strength or low-temperature toughness, and after treatment at 100°C for 1,000 hours in a coolant environment, the impact toughness of the pipe further decreased, and they did not have high temperature resistance, long-term use performance, or good chemical resistance (to coolants), demonstrating the advantages of the type of copolymer polyethylene selected in the present invention.

[0070] Compared with Example 3, the stretch ratio of Comparative Example 3 is 1:6, so the initial stretch strength of the pipe is lower, and after long-term treatment with the cooling liquid, the attenuation of the stretch strength of the pipe is more serious. This shows that the limited stretch ratio in the present invention is more favorable to maintaining the mechanical properties of the pipe material, and has better chemical resistance and long-term use performance.

[0071] The initial performance of the pipe obtained in Comparative Example 4 was basically the same as that of Example 4. However, since antioxidant 1010 was selected in Comparative Example 4, the mechanical properties of the pipe produced therein, such as tensile strength and low-temperature toughness, were significantly reduced after long-term treatment with a coolant. This indicates that the preferred types of antioxidants of the present invention have a significant advantage in the long-term use performance and good chemical resistance (to coolants) of the pipe.

[0072] Although some embodiments of the present invention have been described above, the above description is illustrative rather than exhaustive and is not limited to the disclosed embodiments. Various modifications and alterations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A multi-layer composite piping material, I. An outer layer made of a polyamide composition (A), wherein the polyamide composition (A) contains at least one semi-crystalline polyamide (A1), and the average number of carbon atoms Nc of each nitrogen atom is 8 to 18, preferably 9 to 12; II. An inner layer made of a polyolefin composition (B), wherein the polyolefin composition (B) contains at least one copolymerized polyethylene (B1); III. A multilayer composite piping material characterized by including an adhesive layer made of a modified polyolefin material (C), which is an olefin polymer modified with a polar group, for adhering an outer layer I and an inner layer II.

2. The copolymerized polyethylene (B1) has a molecular weight of 150,000 to 400,000 and a molecular weight distribution of 10 to 25, and / or The copolymerized polyethylene (B1) has a melt flow index of 0.2 to 1.5 g / 10 min (190°C, 5 kg) and a density of 0.93 to 0.97 g / cm 3 , a crystallinity of <70% and a melting point of 120-140°C, and / or The polyethylene copolymer (B1) is a copolymer formed of ethylene and one or more α-olefins, and the α-olefins are preferably selected from C2 to C12 olefin monomers, more preferably C4 to C8 olefin monomers, and / or 2. The multilayer composite piping material according to claim 1, wherein the content of the copolymerized monomer in the copolymerized polyethylene (B1) is 1 to 5 wt % relative to the total weight of the copolymerized polyethylene (B1).

3. The content of the copolymerized polyethylene (B1) is in the range of 80 to 99 wt % based on the total weight of the polyolefin composition (B), and / or The polyolefin composition (B) is 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 other auxiliary agents (B5), Preferably, the antioxidant (B2) is a precipitation-resistant antioxidant, more preferably one or more selected from the group consisting of aromatic amine antioxidants, sterically hindered phenol antioxidants, sulfur-containing synergists, and hydroxylamine benzofuranone derivatives; Preferably, the lubricant (B3) is one or more selected from the group consisting of titanate ester, stearic acid, erucic acid amide, oleic acid amide, and silicone; Preferably, the filler (B4) is selected from inorganic fillers or organic fillers, more preferably one or more selected from silicon dioxide, talc, wollastonite, and calcium carbonate; The multilayer composite piping material according to claim 1, wherein the other auxiliary agent (B5) is preferably one or more selected from the group consisting of a photoaging inhibitor, a leveling agent, and a toughness improver.

4. The semi-crystalline polyamide (A1) is one or more selected from PA1012, PA12, PA612, PA610, PA614, PA1212, PA614, PA616 and PA618, and / or The multilayer composite piping material according to claim 1, characterized in that the content of said semi-crystalline polyamide (A1) is ≧50 wt%, preferably 70-99 wt%, more preferably 80-99 wt%, based on the total weight of said polyamide composition (A).

5. the polyamide composition (A) further comprises one or more of an impact modifier (A2), a plasticizer (A3) and an additive component (A4); and / or Relative to the total weight of the polyamide composition (A), The content of the impact modifier (A2) is 0 to 25 wt %, preferably 3 to 20 wt %, and more preferably 3 to 10 wt %; the content of the plasticizer (A3) is 0 to 20 wt %, preferably 1 to 15 wt %, and more preferably 2 to 12 wt %, 2. The multilayer composite piping material according to claim 1, wherein the content of the additive component (A4) is 0 to 5 wt %, preferably 1 to 3 wt %.

6. The impact modifier (A2) is an elastomer copolymer, preferably one or more selected from ethylene / butylene copolymers, ethylene / hexene copolymers, ethylene / octene copolymers, ethylene / (meth)acrylic acid alkyl ester copolymers, ethylene / styrene / butadiene copolymers, styrene / butadiene diblock / triblock copolymers, and ethylene-propylene diblock / triblock copolymers; The multilayer composite piping material according to claim 5, characterized in that the elastomer copolymer contains a polar functional group, and the polar functional group is preferably one or more selected from the group consisting of an acid anhydride, an epoxy group, a halogen, a carboxyl group, an amino group, a hydroxyl group, and derivatives thereof.

7. In the modified polyolefin material (C), the polar group as the modifying functional group is one or more selected from the group consisting of an acid anhydride, a carboxyl group, an amino group, a hydroxyl group, and derivatives thereof; and / or 2. The multilayer composite piping material according to claim 1, wherein the content of the polar group is in the range of 0.1 to 2.0 wt %.

8. The multilayer composite piping material has an outer diameter of 4 to 30 mm, preferably 8 to 24 mm, and a wall thickness of 0.6 to 3 mm, preferably 1 to 2 mm; the thickness of the outer layer I made of the polyamide composition (A) is 80% or less of the total thickness of the multilayer composite piping material, preferably 20 to 70% of the total thickness of the multilayer composite piping material, and more preferably 30 to 50% of the total thickness of the multilayer composite piping material; The multilayer composite piping material described in claim 1, characterized in that the thickness of the adhesive layer III, which is the modified polyolefin material (C), is 20% or less of the total thickness of the multilayer composite piping material, preferably 10 to 20% of the total thickness of the multilayer composite piping material.

9. The multi-layer composite piping material according to claim 1, characterized in that the multi-layer composite piping material is an oriented smooth multi-layer pipe, and the stretch ratio in the extrusion direction is less than 1:5, preferably the stretch ratio is 1:1.5 to 1:

4.

10. The method for producing a multilayer composite piping material according to any one of claims 1 to 9, characterized in that the polyamide composition (A) is used as an outer layer, the polyolefin composition (B) is used as an inner layer, and the modified polyolefin material (C) is used as an intermediate layer that bonds the outer layer and the inner layer, and then the method for producing a multilayer composite piping material is carried out by a multilayer co-extrusion device.

Images