A multilayer polyolefin pipe and its preparation method

Abstract

This invention discloses a multilayer polyolefin pipe and its preparation method, relating to the technical field of polymer materials. A multilayer polyolefin pipe, from the inside out, comprises a polyolefin layer, a first adhesive layer, an oxygen barrier layer, a second adhesive layer, and a protective layer. The raw materials for the oxygen barrier layer include polyketone, ethylene-vinyl alcohol copolymer, and a compatibilizer, with a weight ratio of (80-100):(8-25):(1-6). The raw materials for the protective layer include polyolefin resin, an antioxidant, and a light stabilizer, with a weight ratio of (90-100):(0.1-0.6):(0.2-3). This invention, through the provision of the oxygen barrier layer and the protective layer, significantly improves the environmental tolerance of the multilayer polyolefin pipe, enhancing its long-term stability and reliability under humid and sunlight conditions.

Description

Technical Field

[0001] This invention relates to the technical field of polymer materials, and in particular to a multilayer polyolefin tube and its preparation method. Background Technology

[0002] Currently, multilayer oxygen-barrier polyolefin pipes typically use ethylene-vinyl alcohol copolymer (EVOH) as the oxygen barrier layer. However, EVOH has poor anti-scaling and chemical corrosion resistance, especially in humid environments. EVOH absorbs moisture, and its oxygen permeability increases significantly after water absorption, leading to the failure of its oxygen barrier function. Polyketone (POK) is a biodegradable engineering plastic polymerized from carbon monoxide and unsaturated hydrocarbons under the action of a catalyst. POK has good gas barrier properties and, compared to EVOH, has advantages such as resistance to hydrolysis and chemical corrosion, making it a potential alternative to EVOH as an oxygen barrier layer. However, POK requires a higher processing temperature, leading to increased processing difficulty and poor product stability. Furthermore, POK has poor light stability and is prone to degradation and aging under light exposure, resulting in decreased oxygen barrier function and product failure. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a multilayer polyolefin pipe and its preparation method. By incorporating an oxygen barrier layer and a protective layer, this invention significantly improves the environmental tolerance of the multilayer polyolefin pipe, enhancing its long-term stability and reliability under humid and sunlight conditions.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] In a first aspect, the present invention provides a multilayer polyolefin pipe, comprising, from the inside out, a polyolefin layer, a first adhesive layer, an oxygen barrier layer, a second adhesive layer, and a protective layer. The raw materials of the oxygen barrier layer include polyketone (POK), ethylene-vinyl alcohol copolymer, and a compatibilizer, and the weight ratio of the polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer is (80-100):(8-25):(1-6). The compatibilizer includes at least one of maleic anhydride-grafted polyethylene, maleic anhydride-grafted ethylene-vinyl acetate, and polyamide.

[0006] The raw materials of the protective layer include polyolefin resin, antioxidant, and light stabilizer, and the weight ratio of the polyolefin resin, antioxidant, and light stabilizer is (90-100):(0.1-0.6):(0.2-3).

[0007] This invention adds a polyketone and ethylene-vinyl alcohol copolymer to the oxygen barrier layer, giving it excellent resistance to hydrolysis and chemical corrosion, thus improving the long-term stability of the multilayer polyolefin tube. Furthermore, the invention selects specific compatibilizers to improve the compatibility between the polyketone and ethylene-vinyl alcohol copolymers, further enhancing the stability of the multilayer polyolefin tube. Simultaneously, by adding a light stabilizer to the protective layer, this invention not only improves the light aging resistance of the multilayer polyolefin tube but also enhances its long-term oxygen barrier stability.

[0008] This invention, by controlling the weight ratio of polyketone, ethylene-vinyl alcohol copolymer, compatibilizer, and polyolefin resin, antioxidant, and light stabilizer, is beneficial to further improve the long-term stability and reliability of multilayer polyolefin pipes.

[0009] Preferably, the weight ratio of the polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer is (80-90):(10-20):(2-5).

[0010] Preferably, the thickness of the polyolefin layer is 1.5-3.0 mm.

[0011] Preferably, the polyolefin layer includes one of a polyethylene layer, a polypropylene layer, and a polybutene layer.

[0012] More preferably, the polyethylene layer is one of a high-density polyethylene layer, a heat-resistant polyethylene layer, or a cross-linked polyethylene layer.

[0013] More preferably, the heat-resistant polyethylene layer is a PE-RT type I layer or a PE-RT type II layer.

[0014] Preferably, the polypropylene layer is one of a copolymer polypropylene layer or a block copolymer polypropylene layer.

[0015] Preferably, the thickness of both the first adhesive layer and the second adhesive layer is 0.03-0.15 mm.

[0016] More preferably, the thickness of the first adhesive layer and the second adhesive layer is any one or a combination of 0.03 mm, 0.05 mm, 0.08 mm, 0.10 mm, 0.12 mm, and 0.15 mm.

[0017] Preferably, both the first adhesive layer and the second adhesive layer are hot melt adhesive layers. The selection of the hot melt adhesive described in this invention includes, but is not limited to, maleic anhydride-grafted polyolefins.

[0018] Preferably, the thickness of the oxygen barrier layer is 0.03-0.15 mm.

[0019] More preferably, the thickness of the oxygen barrier layer is any one or a combination of 0.03 mm, 0.05 mm, 0.08 mm, 0.10 mm, 0.12 mm, and 0.15 mm.

[0020] Preferably, the thickness of the protective layer is 0.5-1.5 mm.

[0021] More preferably, the weight ratio of polyolefin resin, antioxidant and light stabilizer in the protective layer is 100:(0.2-0.4):(0.5-2).

[0022] Preferably, the polyolefin resin includes one of polyethylene resin, polypropylene resin, and polybutene resin.

[0023] Preferably, the type of polyolefin in the protective layer is the same as the type of polyolefin in the polyolefin layer.

[0024] Preferably, the antioxidant includes at least one of tocopherol, antioxidant 1076, and antioxidant 1010.

[0025] Preferably, the light stabilizer includes at least one of carbon black, hindered amine light stabilizer, and UV-531.

[0026] Secondly, the present invention also provides a method for preparing a multilayer polyolefin tube, comprising the following steps:

[0027] (1) Polyolefin resin is added to the first twin-screw extruder and extruded to obtain a polyolefin layer;

[0028] (2) The raw material in the first adhesive layer is added to the second twin-screw extruder and extruded and coated onto the outer surface of the polyolefin layer to obtain the first adhesive layer;

[0029] (3) A mixture of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer is added to a third twin-screw extruder and extruded onto the outer surface of the first adhesive layer to obtain an oxygen barrier layer;

[0030] (4) The raw material in the second adhesive layer is added to the fourth twin-screw extruder and extruded and coated on the outer surface of the oxygen barrier layer to obtain the second adhesive layer;

[0031] (5) Add the mixture of polyolefin resin, antioxidant and light stabilizer to the fifth twin-screw extruder and extrude it onto the outer surface of the second adhesive layer to obtain a protective layer; finally, after vacuum sizing and cooling, a multilayer polyolefin pipe is obtained.

[0032] Preferably, the extrusion temperature of the first twin-screw extruder is 140-240℃; the extrusion temperature of the second twin-screw extruder is 150-225℃; the extrusion temperature of the third twin-screw extruder is 170-240℃; the extrusion temperature of the fourth twin-screw extruder is 150-225℃; and the extrusion temperature of the fifth twin-screw extruder is 140-240℃.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] This invention adds a polyketone and ethylene-vinyl alcohol copolymer to the oxygen barrier layer, giving it advantages such as low oxygen permeability, good resistance to hydrolysis and chemical corrosion. Furthermore, the polyketone and ethylene-vinyl alcohol copolymer blend has a low melting point and low processing temperature, making the processing easier to control and more stable. The lower processing temperature also reduces energy consumption during production. Simultaneously, by adding a light stabilizer to the protective layer, this invention significantly improves the light aging resistance and stability of the multilayer polyolefin pipe, thereby enhancing the long-term reliability and service life of the product. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the multilayer polyolefin tube of the present invention, wherein 1 is the polyolefin layer, 2 is the first adhesive layer, 3 is the oxygen barrier layer, 4 is the second adhesive layer, and 5 is the protective layer. Detailed Implementation

[0036] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the scope of protection and implementation of the present invention are not limited thereto.

[0037] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0038]

[0039] The following examples and comparative examples all use substances from the above-mentioned sources.

[0040] Example 1

[0041] This embodiment discloses a multilayer polyolefin pipe, such as Figure 1 As shown, from the inside out, it includes a polyolefin layer 1, a first adhesive layer 2, an oxygen barrier layer 3, a second adhesive layer 4, and a protective layer 5.

[0042] The thicknesses of the polyolefin layer 1, the first adhesive layer 2, the oxygen barrier layer 3, the second adhesive layer 4, and the protective layer 5 are 2.3 mm, 0.05 mm, 0.10 mm, 0.05 mm, and 0.6 mm, respectively.

[0043] The polyolefin layer is a polyethylene layer, and the raw material is polyethylene resin. The raw materials for both the first adhesive layer and the second adhesive layer are hot melt adhesives.

[0044] The raw materials for the oxygen barrier layer include polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer, and the weight ratio of polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer is 80:20:5; the compatibilizer is polyamide (Rilsan® PA1212).

[0045] The protective layer is made of polyethylene resin, antioxidant, and light stabilizer, with the weight ratio of polyethylene resin, antioxidant, and light stabilizer being 100:0.4:2.0; the antioxidant is tocopherol, and the light stabilizer is carbon black.

[0046] This embodiment also discloses a method for preparing a multilayer polyolefin tube, including the following steps:

[0047] (1) Polyethylene resin is added to the first twin-screw extruder and extruded to obtain a polyethylene layer; the extrusion temperature of the first twin-screw extruder is: Zone 1 140-170℃; Zone 2 170-190℃; Zone 3 190-210℃; Zone 4 200-220℃.

[0048] (2) The hot melt adhesive in the first adhesive layer is added to the second twin-screw extruder and extruded and coated on the outer surface of the polyethylene layer to obtain the first adhesive layer; the extrusion temperature of the second twin-screw extruder is: Zone 1 150-170℃; Zone 2 170-195℃; Zone 3 195-210℃; Zone 4 200-225℃.

[0049] (3) The mixture of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer is added to the third twin-screw extruder and extruded and coated on the outer surface of the first adhesive layer to obtain an oxygen barrier layer; the extrusion temperature of the third twin-screw extruder is: Zone 1 170-190℃; Zone 2 190-210℃; Zone 3 210-230℃; Zone 4 220-240℃.

[0050] (4) The hot melt adhesive in the second adhesive layer is added to the fourth twin-screw extruder and extruded and coated on the outer surface of the oxygen barrier layer to obtain the second adhesive layer; the extrusion temperature of the fourth twin-screw extruder is 150-170℃ in zone 1; 170-195℃ in zone 2; 195-210℃ in zone 3; and 200-225℃ in zone 4.

[0051] (5) A mixture of polyethylene resin, antioxidant and light stabilizer is added to the fifth twin-screw extruder and extruded to coat the outer surface of the second adhesive layer to obtain a protective layer; finally, the multilayer polyolefin pipe is obtained by vacuum sizing and cooling. The extrusion temperature of the fifth twin-screw extruder is: Zone 1 140-170℃; Zone 2 170-190℃; Zone 3 190-210℃; Zone 4 200-220℃.

[0052] Example 2

[0053] A multilayer polyolefin pipe, which differs from Example 1 in that the weight ratio of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer in the oxygen barrier layer is 100:8:1.

[0054] Example 3

[0055] A multilayer polyolefin pipe, which differs from Example 1 in that the weight ratio of polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer in the oxygen barrier layer is 90:25:6.

[0056] Example 4

[0057] A multilayer polyolefin pipe, which differs from Example 1 in that the weight ratio of polyethylene resin, antioxidant, and light stabilizer in the protective layer is 100:0.2:1.

[0058] Example 5

[0059] A multilayer polyolefin pipe, which differs from Example 1 in that the weight ratio of polyethylene resin, antioxidant, and light stabilizer in the protective layer is 100:0.6:3.

[0060] Example 6

[0061] This embodiment discloses a multilayer polyolefin pipe, such as Figure 1 As shown, from the inside out, it includes a polyolefin layer 1, a first adhesive layer 2, an oxygen barrier layer 3, a second adhesive layer 4, and a protective layer 5.

[0062] The thicknesses of the polyolefin layer 1, the first adhesive layer 2, the oxygen barrier layer 3, the second adhesive layer 4, and the protective layer 5 are 1.9 mm, 0.15 mm, 0.05 mm, 0.15 mm, and 1.0 mm, respectively.

[0063] The polyolefin layer is a polybutene layer, and the raw material is polybutene resin. The raw materials for the first adhesive layer and the second adhesive layer are both hot melt adhesives. The raw materials for the oxygen barrier layer include polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer, and the weight ratio of polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer is 100:15:5; the compatibilizer is polyamide (Rilsan® PA1212).

[0064] The protective layer is made of polybutene resin, antioxidant, and light stabilizer, with the weight ratio of polybutene resin, antioxidant, and light stabilizer being 100:0.1:1.0; the antioxidant is antioxidant 1076, and the light stabilizer is Tinuvin 622.

[0065] This embodiment also discloses a method for preparing a multilayer polyolefin tube, including the following steps:

[0066] (1) Polybutene resin is added to the first twin-screw extruder and extruded to obtain a polybutene layer; the extrusion temperature of the first twin-screw extruder is: Zone 1 160-180℃; Zone 2 180-200℃; Zone 3 200-220℃; Zone 4 220-240℃.

[0067] (2) The hot melt adhesive in the first adhesive layer is added to the second twin-screw extruder and extruded to coat the outer surface of the polybutene layer to obtain the first adhesive layer; the extrusion temperature of the second twin-screw extruder is: Zone 1 150-170℃; Zone 2 170-195℃; Zone 3 195-210℃; Zone 4 200-225℃.

[0068] (3) The mixture of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer is added to the third twin-screw extruder and extruded and coated on the outer surface of the first adhesive layer to obtain an oxygen barrier layer; the extrusion temperature of the third twin-screw extruder is: Zone 1 170-190℃; Zone 2 190-210℃; Zone 3 210-230℃; Zone 4 220-240℃.

[0069] (4) The hot melt adhesive in the second adhesive layer is added to the fourth twin-screw extruder and extruded and coated on the outer surface of the oxygen barrier layer to obtain the second adhesive layer; the extrusion temperature of the fourth twin-screw extruder is: Zone 1 150-170℃; Zone 2 170-195℃; Zone 3 195-210℃; Zone 4 200-225℃.

[0070] (5) Add the mixture of polybutene resin, antioxidant and light stabilizer to the fifth twin-screw extruder and extrude it onto the outer surface of the second adhesive layer to obtain a protective layer; finally, after vacuum sizing and cooling, multilayer polyolefin pipe is obtained, with zone 1 at 160-180℃; zone 2 at 180-200℃; zone 3 at 200-220℃; and zone 4 at 220-240℃.

[0071] Example 7

[0072] This embodiment discloses a multilayer polyolefin pipe, such as Figure 1 As shown, from the inside out, it includes a polyolefin layer 1, a first adhesive layer 2, an oxygen barrier layer 3, a second adhesive layer 4, and a protective layer 5.

[0073] The thicknesses of the polyolefin layer 1, the first adhesive layer 2, the oxygen barrier layer 3, the second adhesive layer 4, and the protective layer 5 are 1.6 mm, 0.10 mm, 0.15 mm, 0.10 mm, and 1.3 mm, respectively.

[0074] The polyolefin layer is a polypropylene layer, and the raw material is polypropylene resin. The raw materials for both the first adhesive layer and the second adhesive layer are hot melt adhesives.

[0075] The raw materials for the oxygen barrier layer include polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer, and the weight ratio of polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer is 90:10:2; the compatibilizer includes maleic anhydride-grafted ethylene-vinyl acetate and maleic anhydride-grafted polyethylene, and the mass ratio of maleic anhydride-grafted ethylene-vinyl acetate and maleic anhydride-grafted polyethylene is 6:4.

[0076] The protective layer is made of polypropylene resin, antioxidant, and light stabilizer, with a weight ratio of 90:0.3:0.5. The antioxidant is antioxidant 1010, and the light stabilizer is UV-531.

[0077] This embodiment also discloses a method for preparing a multilayer polyolefin tube, including the following steps:

[0078] (1) Polypropylene resin is added to the first twin-screw extruder and extruded to obtain a polypropylene layer; the extrusion temperature of the first twin-screw extruder is: Zone 1 170-190℃; Zone 2 190-210℃; Zone 3 210-230℃; Zone 4 220-240℃.

[0079] (2) The hot melt adhesive in the first adhesive layer is added to the second twin-screw extruder and extruded and coated on the outer surface of the polypropylene layer to obtain the first adhesive layer; the extrusion temperature of the second twin-screw extruder is: Zone 1 150-170℃; Zone 2 170-195℃; Zone 3 195-210℃; Zone 4 200-225℃.

[0080] (3) The mixture of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer is added to the third twin-screw extruder and extruded and coated on the outer surface of the first adhesive layer to obtain an oxygen barrier layer; the extrusion temperature of the third twin-screw extruder is: Zone 1 170-190℃; Zone 2 190-210℃; Zone 3 210-230℃; Zone 4 220-240℃.

[0081] (4) The hot melt adhesive in the second adhesive layer is added to the fourth twin-screw extruder and extruded and coated on the outer surface of the oxygen barrier layer to obtain the second adhesive layer; the extrusion temperature of the fourth twin-screw extruder is: Zone 1 150-170℃; Zone 2 170-195℃; Zone 3 195-210℃; Zone 4 200-225℃.

[0082] (5) A mixture of polypropylene resin, antioxidant and light stabilizer is added to the fifth twin-screw extruder and extruded to coat the outer surface of the second adhesive layer to obtain a protective layer; finally, the multilayer polyolefin pipe is obtained by vacuum sizing and cooling. The extrusion temperature of the fifth twin-screw extruder is 170-190℃ in zone 1; 190-210℃ in zone 2; 210-230℃ in zone 3; and 220-240℃ in zone 4.

[0083] Comparative Example 1

[0084] A multilayer polyolefin pipe, which differs from Example 1 in that the oxygen barrier layer does not contain polyketone.

[0085] Comparative Example 2

[0086] A multilayer polyolefin tube, which differs from Example 1 in that no light stabilizer is added to the raw material of the protective layer.

[0087] Comparative Example 3

[0088] A multilayer polyolefin pipe, which differs from Example 1 in that the weight ratio of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer in the oxygen barrier layer is 80:40:5.

[0089] Comparative Example 4

[0090] A multilayer polyolefin tube, which differs from Example 1 in that the weight ratio of polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer in the oxygen barrier layer is 100:5:2.

[0091] Comparative Example 5

[0092] A multilayer polyolefin pipe, which differs from Example 1 in that the weight ratio of polyethylene resin, antioxidant, and light stabilizer in the protective layer is 100:0.6:0.1.

[0093] Comparative Example 6

[0094] A multilayer polyolefin pipe, which differs from Example 1 in that the weight ratio of polyethylene resin, antioxidant, and light stabilizer in the protective layer is 100:0.6:4.

[0095] Comparative Example 7

[0096] A multilayer polyolefin tube, which differs from Example 1 in that it uses polyethylene glycol instead of ethylene-vinyl alcohol copolymer in equal mass.

[0097] Comparative Example 8

[0098] A multilayer polyolefin tube, which differs from Example 1 in that it uses an equal mass of polyacrylic acid instead of polyamide.

[0099] Performance testing

[0100] 1. Oxygen permeability: Tested according to Method II in GB / T 34437-2017.

[0101] 2. Hydrostatic pressure: Tested according to GB / T 28799.2-2020 (polyethylene), GB / T 19473.2-2020 (polybutene), and GB / T18742.2-2017 (polypropylene).

[0102] 3. Hot and cold water circulation: Tested in accordance with GB / T 19993-2005.

[0103] 4. Xenon lamp aging: Tested according to ASTM D2565-2016.

[0104] The test results are shown in Table 1.

[0105] Table 1

[0106]

[0107] As shown in Table 1, the multilayer polyolefin tube of the present invention has excellent resistance to light aging and long-term oxygen barrier stability.

[0108] Comparing Comparative Examples 1-2 with Example 1, it can be seen that if polyketone is not added to the oxygen barrier layer, the water absorption of the oxygen barrier layer increases after hot and cold water circulation, leading to an increase in oxygen permeability. If a light stabilizer is not added to the protective layer, the light aging resistance of the multilayer polyolefin tube decreases. Therefore, the present invention, by adding polyketone to the oxygen barrier layer and a light stabilizer to the protective layer, is beneficial to improving the light aging resistance and long-term oxygen barrier stability of the multilayer polyolefin tube.

[0109] Comparing Comparative Examples 3-4 with Example 1, it can be seen that ethylene-vinyl alcohol copolymer can improve the light stability of polyketone. However, if the content of ethylene-vinyl alcohol copolymer is too high, the water absorption of the oxygen barrier layer will increase after hot and cold water circulation, resulting in a significant increase in oxygen permeability. If the content of polyketone is too high, the oxygen barrier layer will be more easily degraded under ultraviolet light aging, thus reducing the light aging resistance of the multilayer polyolefin tube. Therefore, by controlling the weight ratio of polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer to (80-100):(8-25):(1-6), this invention is beneficial to improving the light aging resistance and long-term oxygen barrier stability of multilayer polyolefin tubes.

[0110] Comparing Comparative Examples 5-6 with Example 1, it can be seen that if the content of light stabilizer in the protective layer is too low, it is difficult to prevent the decomposition of POK in the oxygen barrier layer under ultraviolet irradiation, resulting in a significant increase in oxygen permeability and a decrease in the light aging resistance of the multilayer polyolefin pipe. If the content of light stabilizer is too high, it may affect the performance of the pipe material, thereby affecting its light aging resistance. Therefore, by controlling the weight ratio of polyolefin resin, antioxidant, and light stabilizer to (90-100):(0.1-0.6):(0.2-3), this invention can prevent the decomposition of POK in the oxygen barrier layer under ultraviolet irradiation, thereby improving the light aging resistance and long-term oxygen barrier stability of the multilayer polyolefin pipe.

[0111] Comparing Comparative Examples 7-8 with Example 1, it can be seen that in Comparative Example 7, an equal mass of polyethylene glycol was used to replace ethylene-vinyl alcohol copolymer. Since polyethylene glycol lacks oxygen barrier properties, this resulted in a decrease in oxygen barrier performance, and the initial oxygen permeability value could not meet the requirements for oxygen barrier. This indicates that not any polymer can be blended with polyketide to achieve excellent long-term oxygen barrier stability in multilayer polyolefin tubes. Furthermore, in Comparative Example 8, an equal mass of polyacrylic acid was used to replace polyamide. POK and EVOH are not well compatible, leading to a decrease in the oxygen barrier performance of the oxygen barrier layer. The initial oxygen permeability value was insufficient to meet the requirements for oxygen barrier, demonstrating that not any compatibilizer can guarantee excellent long-term oxygen barrier stability and resistance to photoaging in multilayer polyolefin tubes.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A multilayer polyolefin pipe, characterized in that, The structure, from the inside out, comprises a polyolefin layer, a first adhesive layer, an oxygen barrier layer, a second adhesive layer, and a protective layer. The raw materials for the oxygen barrier layer include polyketone, ethylene-vinyl alcohol copolymer, and a compatibilizer, and the weight ratio of the polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer is (80-100):(8-25):(1-6). The compatibilizer includes at least one of maleic anhydride-grafted polyethylene, maleic anhydride-grafted ethylene-vinyl acetate, and polyamide. The raw materials of the protective layer include polyolefin resin, antioxidant, and light stabilizer, and the weight ratio of the polyolefin resin, antioxidant, and light stabilizer is 100:(0.2-0.4):(0.5-2).

2. The multilayer polyolefin pipe as described in claim 1, characterized in that, The thickness of the polyolefin layer is 1.5-3.0 mm; And / or, the thickness of the first adhesive layer is 0.03-0.15 mm; And / or, the thickness of the second adhesive layer is 0.03-0.15 mm; And / or, the thickness of the oxygen barrier layer is 0.03-0.15 mm; And / or, the thickness of the protective layer is 0.5-1.5 mm.

3. The multilayer polyolefin pipe as described in claim 1, characterized in that, The weight ratio of polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer in the oxygen barrier layer is (80-90):(10-20):(2-5).

4. The multilayer polyolefin pipe as described in claim 1, characterized in that, The polyolefin layer includes one of a polyethylene layer, a polypropylene layer, and a polybutene layer.

5. The multilayer polyolefin pipe as described in claim 4, characterized in that, The polyethylene layer is one of high-density polyethylene, heat-resistant polyethylene, or cross-linked polyethylene.

6. The multilayer polyolefin pipe as described in claim 4, characterized in that, The polypropylene layer is a copolymer polypropylene layer.

7. The multilayer polyolefin pipe as described in claim 1, characterized in that, Both the first adhesive layer and the second adhesive layer are hot melt adhesive layers.

8. The multilayer polyolefin pipe as described in claim 1, characterized in that, The antioxidant includes at least one of tocopherol, antioxidant 1076, and antioxidant 1010; And / or, the light stabilizer includes at least one of carbon black, hindered amine light stabilizer, and UV-531.

9. A method for preparing a multilayer polyolefin pipe as described in any one of claims 1-8, characterized in that, Includes the following steps: (1) Polyolefin resin is added to the first twin-screw extruder and extruded to obtain a polyolefin layer; (2) The raw material in the first adhesive layer is added to the second twin-screw extruder and extruded and coated onto the outer surface of the polyolefin layer to obtain the first adhesive layer; (3) A mixture of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer is added to a third twin-screw extruder and extruded onto the outer surface of the first adhesive layer to obtain an oxygen barrier layer; (4) The raw material in the second adhesive layer is added to the fourth twin-screw extruder and extruded and coated on the outer surface of the oxygen barrier layer to obtain the second adhesive layer; (5) Add the mixture of polyolefin resin, antioxidant and light stabilizer to the fifth twin-screw extruder and extrude it onto the outer surface of the second adhesive layer to obtain a protective layer; finally, after vacuum sizing and cooling, a multilayer polyolefin pipe is obtained.

10. The method for preparing a multilayer polyolefin pipe as described in claim 9, characterized in that, The extrusion temperature of the first twin-screw extruder is 140-240℃; the extrusion temperature of the second twin-screw extruder is 150-225℃; the extrusion temperature of the third twin-screw extruder is 170-240℃; the extrusion temperature of the fourth twin-screw extruder is 150-225℃; and the extrusion temperature of the fifth twin-screw extruder is 140-240℃.

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