Multilayer polyolefin pipe and preparation method thereof

Abstract

The invention discloses a multilayer polyolefin pipe and a preparation method thereof, and relates to the technical field of high polymer materials. The multilayer polyolefin pipe sequentially comprises a polyolefin layer, a first bonding layer, an oxygen barrier layer, a second bonding layer and a protective layer from inside to outside, the oxygen barrier layer is prepared from polyketone, an ethylene-vinyl alcohol copolymer and a compatilizer, and the weight ratio of the polyketone to the ethylene-vinyl alcohol copolymer to the compatilizer is (80-100): (8-25): (1-6); the protective layer comprises the following raw materials: polyolefin resin, an antioxidant and a light stabilizer, and the weight ratio of the polyolefin resin to the antioxidant to the light stabilizer is (90-100): (0.1-0.6): (0.2-3). Through the arrangement of the oxygen barrier layer and the protective layer, the environmental tolerance of the multi-layer polyolefin pipe is greatly improved, and the long-term stability and reliability of the pipe in a humid and light environment are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, in particular to a multilayer polyolefin tube and a preparation method thereof. Background Art

[0002] Currently, multi-layer oxygen-barrier polyolefin pipes typically use ethylene-vinyl alcohol copolymer (EVOH) as the oxygen barrier layer. However, EVOH has poor anti-fouling and chemical corrosion resistance, especially in humid environments, where it absorbs moisture. This significantly increases EVOH's oxygen permeability, rendering its oxygen barrier ineffective. Polyketone (POK) is a new biodegradable engineering plastic made from carbon monoxide and unsaturated hydrocarbons, polymerized under a catalyst. POK has excellent gas barrier properties and, compared to EVOH, offers resistance to hydrolysis and chemical corrosion, making it a potential alternative to EVOH as an oxygen barrier layer. However, POK's high processing temperature increases the complexity of the process and results in poor product stability. Furthermore, POK has poor photostability and is susceptible to degradation and aging under light, leading to a decrease in its oxygen barrier function and product failure. Summary of the Invention

[0003] The present invention aims to overcome the shortcomings of the prior art by providing a multilayer polyolefin tube and a method for preparing the same. By providing an oxygen barrier layer and a protective layer, the present invention significantly improves the environmental resistance of the multilayer polyolefin tube, enhancing the long-term stability and reliability of the tube in humid and sunny environments.

[0004] To achieve the above object, the technical solution adopted by the present invention is: In a first aspect, the present invention provides a multi-layer polyolefin tube, comprising, from the inside out, a polyolefin layer, a first adhesive layer, an oxygen barrier layer, a second adhesive layer, and a protective layer, wherein the raw materials of the oxygen barrier layer include polyketone (POK), an ethylene-vinyl alcohol copolymer, and a compatibilizer, and the weight ratio of the polyketone, the ethylene-vinyl alcohol copolymer, and the 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 (90-100): (0.1-0.6): (0.2-3).

[0005] The present invention incorporates polyketone and ethylene-vinyl alcohol copolymer into the oxygen barrier layer, imparting excellent hydrolysis and chemical corrosion resistance to the oxygen barrier layer, thereby enhancing the long-term stability of the multilayer polyolefin tube. Furthermore, the present invention utilizes a specific compatibilizer to enhance the compatibility between the polyketone and ethylene-vinyl alcohol copolymer, further improving the stability of the multilayer polyolefin tube. Furthermore, the present invention incorporates a light stabilizer into the protective layer, thereby enhancing not only the light aging resistance of the multilayer polyolefin tube but also the long-term oxygen barrier stability of the multilayer polyolefin tube.

[0006] The invention is beneficial to further improve the long-term stability and reliability of the multilayer polyolefin pipe by controlling the weight ratio of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer and the weight ratio of polyolefin resin, antioxidant and light stabilizer.

[0007] Preferably, the weight ratio of the polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer is (80-90): (10-20): (2-5).

[0008] Preferably, the polyolefin layer has a thickness of 1.5-3.0 mm.

[0009] Preferably, the polyolefin layer includes one of a polyethylene layer, a polypropylene layer and a polybutylene layer.

[0010] More preferably, the polyethylene layer is one of a high-density polyethylene layer, a heat-resistant polyethylene layer, and a cross-linked polyethylene layer.

[0011] More preferably, the heat-resistant polyethylene layer is a PE-RT I type layer or a PE-RT II type layer.

[0012] Preferably, the polypropylene layer is one of a copolymer polypropylene layer and a block copolymer polypropylene layer.

[0013] Preferably, the thickness of the first adhesive layer and the second adhesive layer are both 0.03-0.15 mm.

[0014] More preferably, the thickness of the first adhesive layer and the second adhesive layer is within the range of any one or both of 0.03 mm, 0.05 mm, 0.08 mm, 0.10 mm, 0.12 mm, and 0.15 mm.

[0015] Preferably, the first adhesive layer and the second adhesive layer are both hot melt adhesive layers. The hot melt adhesive of the present invention may include but is not limited to maleic anhydride grafted polyolefin.

[0016] Preferably, the thickness of the oxygen barrier layer is 0.03-0.15 mm.

[0017] More preferably, the thickness of the oxygen barrier layer is within the range of any one or both of 0.03 mm, 0.05 mm, 0.08 mm, 0.10 mm, 0.12 mm, and 0.15 mm.

[0018] Preferably, the thickness of the protective layer is 0.5-1.5 mm.

[0019] More preferably, the weight ratio of the polyolefin resin, antioxidant and light stabilizer in the protective layer is 100: (0.2-0.4): (0.5-2).

[0020] Preferably, the polyolefin resin includes one of polyethylene resin, polypropylene resin and polybutene resin.

[0021] Preferably, the type of polyolefin in the protective layer is the same as the type of polyolefin in the polyolefin layer.

[0022] Preferably, the antioxidant includes at least one of tocopherol, antioxidant 1076, and antioxidant 1010.

[0023] Preferably, the light stabilizer includes at least one of carbon black, hindered amine light stabilizer, and UV-531.

[0024] In a second aspect, the present invention further provides a method for preparing a multilayer polyolefin tube, comprising the following steps: (1) adding a polyolefin resin into a first twin-screw extruder and extruding the polyolefin resin to obtain a polyolefin layer; (2) adding the raw materials of the first adhesive layer into a second twin-screw extruder and extruding and coating the raw materials on the outer surface of the polyolefin layer to obtain the first adhesive layer; (3) adding a mixture of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer into a third twin-screw extruder and extruding and coating the mixture on the outer surface of the first adhesive layer to obtain an oxygen barrier layer; (4) adding the raw materials of the second adhesive layer into a fourth twin-screw extruder, and extruding and coating the raw materials on the outer surface of the oxygen barrier layer to obtain the second adhesive layer; (5) Adding a mixture of polyolefin resin, antioxidant and light stabilizer into a fifth twin-screw extruder, extrusion coating the mixture on the outer surface of the second adhesive layer to obtain a protective layer; finally, vacuum sizing and cooling to obtain a multilayer polyolefin tube.

[0025] Preferably, the extrusion temperature of the first twin-screw extruder is 140-240°C; the extrusion temperature of the second twin-screw extruder is 150-225°C; the extrusion temperature of the third twin-screw extruder is 170-240°C; the extrusion temperature of the fourth twin-screw extruder is 150-225°C; and the extrusion temperature of the fifth twin-screw extruder is 140-240°C.

[0026] Compared with the prior art, the present invention has the following beneficial effects: The present invention incorporates polyketone and ethylene-vinyl alcohol copolymer into the oxygen barrier layer, resulting in a low oxygen permeability and excellent hydrolysis and chemical corrosion resistance. Furthermore, the polyketone and ethylene-vinyl alcohol copolymer blend has a low melting point and low processing temperature, making the process easy to control and more stable. The lower processing temperature also reduces energy consumption during production. Furthermore, by adding a light stabilizer to the protective layer, the present invention significantly improves the light aging resistance and stability of the multilayer polyolefin tube, thereby enhancing the long-term reliability and service life of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of the multi-layer 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 DESCRIPTION

[0028] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below with reference to specific embodiments, but the protection scope and implementation methods of the present invention are not limited thereto.

[0029] Unless otherwise specified, the materials and reagents used in the following examples are commercially available. The following examples and comparative examples all use materials from the above sources.

[0030] Example 1 This embodiment discloses a multilayer polyolefin tube, such as Figure 1 As shown, from the inside to the outside, 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.

[0031] 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.

[0032] The polyolefin layer is a polyethylene layer, and its raw material is polyethylene resin. The raw materials of the first adhesive layer and the second adhesive layer are both hot melt adhesive.

[0033] The raw materials of the oxygen barrier layer include polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer, and the weight ratio of the polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer is 80:20:5; the compatibilizer is polyamide (Rilsan® PA1212).

[0034] The raw materials of the protective layer include polyethylene resin, antioxidant, and light stabilizer, and the weight ratio of polyethylene resin, antioxidant, and light stabilizer is 100:0.4:2.0; the antioxidant is tocopherol, and the light stabilizer is carbon black.

[0035] This embodiment also discloses a method for preparing a multilayer polyolefin tube, comprising the following steps: (1) Adding polyethylene resin into a first twin-screw extruder for extrusion to obtain a polyethylene layer; the extrusion temperature of the first twin-screw extruder is: 140-170°C in zone 1; 170-190°C in zone 2; 190-210°C in zone 3; and 200-220°C in zone 4.

[0036] (2) Add the hot melt adhesive in the first adhesive layer into a second twin-screw extruder and extrude and coat it on the outer surface of the polyethylene layer to obtain the first adhesive layer; the extrusion temperature of the second twin-screw extruder is: 150-170°C in zone 1; 170-195°C in zone 2; 195-210°C in zone 3; and 200-225°C in zone 4.

[0037] (3) Adding a mixture of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer into a third twin-screw extruder and extruding and coating it 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: 170-190°C in zone 1; 190-210°C in zone 2; 210-230°C in zone 3; and 220-240°C in zone 4.

[0038] (4) Add the hot melt adhesive in the second adhesive layer into a fourth twin-screw extruder, extrude and coat it 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°C in zone 1; 170-195°C in zone 2; 195-210°C in zone 3; and 200-225°C in zone 4.

[0039] (5) Adding a mixture of polyethylene resin, antioxidant and light stabilizer into a fifth twin-screw extruder, extrusion coating the mixture on the outer surface of the second adhesive layer to obtain a protective layer; finally, vacuum sizing and cooling and shaping are performed to obtain a multi-layer polyolefin tube. The extrusion temperatures of the fifth twin-screw extruder are: 140-170°C in zone 1; 170-190°C in zone 2; 190-210°C in zone 3; and 200-220°C in zone 4.

[0040] Example 2 A multi-layer polyolefin tube is different 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.

[0041] Example 3 A multi-layer polyolefin tube is different 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.

[0042] Example 4 A multi-layer polyolefin tube is different from Example 1 in that the weight ratio of the polyethylene resin, the antioxidant, and the light stabilizer in the protective layer is 100:0.2:1.

[0043] Example 5 A multi-layer polyolefin tube is different from Example 1 in that the weight ratio of the polyethylene resin, the antioxidant, and the light stabilizer in the protective layer is 100:0.6:3.

[0044] Example 6 This embodiment discloses a multilayer polyolefin tube, such as Figure 1 As shown, from the inside to the outside, 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.

[0045] 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.

[0046] The polyolefin layer is a polybutylene layer made from polybutylene resin. Both the first and second adhesive layers are made from hot-melt adhesive. The oxygen barrier layer includes polyketone, ethylene-vinyl alcohol copolymer, and a compatibilizer in a weight ratio of 100:15:5. The compatibilizer is a polyamide (Rilsan® PA1212).

[0047] The raw materials of the protective layer include polybutene resin, antioxidant, and light stabilizer, and the weight ratio of polybutene resin, antioxidant, and light stabilizer is 100:0.1:1.0; the antioxidant is antioxidant 1076, and the light stabilizer is Tinuvin 622.

[0048] This embodiment also discloses a method for preparing a multilayer polyolefin tube, comprising the following steps: (1) Adding polybutene resin into a first twin-screw extruder and extruding it to obtain a polybutene layer; the extrusion temperature of the first twin-screw extruder is: 160-180°C in zone 1; 180-200°C in zone 2; 200-220°C in zone 3; and 220-240°C in zone 4.

[0049] (2) Add the hot melt adhesive in the first adhesive layer into a second twin-screw extruder and extrude and coat it on the outer surface of the polybutene layer to obtain the first adhesive layer; the extrusion temperature of the second twin-screw extruder is: 150-170°C in zone 1; 170-195°C in zone 2; 195-210°C in zone 3; and 200-225°C in zone 4.

[0050] (3) Adding a mixture of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer into a third twin-screw extruder and extruding and coating it 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: 170-190°C in zone 1; 190-210°C in zone 2; 210-230°C in zone 3; and 220-240°C in zone 4.

[0051] (4) Add the hot melt adhesive in the second adhesive layer to a fourth twin-screw extruder, extrude and coat it 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°C in zone 1; 170-195°C in zone 2; 195-210°C in zone 3; and 200-225°C in zone 4.

[0052] (5) Adding a mixture of polybutene resin, antioxidant and light stabilizer into a fifth twin-screw extruder, extrusion coating the mixture on the outer surface of the second adhesive layer to obtain a protective layer; finally, vacuum sizing and cooling to obtain a multi-layer polyolefin tube, with the temperature of zone 1 being 160-180°C; zone 2 being 180-200°C; zone 3 being 200-220°C; and zone 4 being 220-240°C.

[0053] Example 7 This embodiment discloses a multilayer polyolefin tube, such as Figure 1 As shown, from the inside to the outside, 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.

[0054] 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.

[0055] The polyolefin layer is a polypropylene layer, and the raw material is polypropylene resin. The raw materials of the first adhesive layer and the second adhesive layer are both hot melt adhesive.

[0056] The raw materials of 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 the 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.

[0057] The raw materials of the protective layer include polypropylene resin, antioxidant, and light stabilizer, and the weight ratio of polypropylene resin, antioxidant, and light stabilizer is 90:0.3:0.5; the antioxidant is antioxidant 1010, and the light stabilizer is UV-531.

[0058] This embodiment also discloses a method for preparing a multilayer polyolefin tube, comprising the following steps: (1) Adding polypropylene resin into a first twin-screw extruder and extruding to obtain a polypropylene layer; the extrusion temperature of the first twin-screw extruder is: 170-190°C in zone 1; 190-210°C in zone 2; 210-230°C in zone 3; and 220-240°C in zone 4.

[0059] (2) Add the hot melt adhesive in the first adhesive layer into a second twin-screw extruder and extrude and coat it on the outer surface of the polypropylene layer to obtain the first adhesive layer; the extrusion temperature of the second twin-screw extruder is: 150-170°C in zone 1; 170-195°C in zone 2; 195-210°C in zone 3; and 200-225°C in zone 4.

[0060] (3) Adding a mixture of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer into a third twin-screw extruder and extruding and coating it 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: 170-190°C in zone 1; 190-210°C in zone 2; 210-230°C in zone 3; and 220-240°C in zone 4.

[0061] (4) Add the hot melt adhesive in the second adhesive layer to a fourth twin-screw extruder, extrude and coat it 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°C in zone 1; 170-195°C in zone 2; 195-210°C in zone 3; and 200-225°C in zone 4.

[0062] (5) Adding a mixture of polypropylene resin, antioxidant and light stabilizer into a fifth twin-screw extruder, extrusion coating the mixture on the outer surface of the second adhesive layer to obtain a protective layer; finally, vacuum sizing and cooling and shaping are performed to obtain a multi-layer polyolefin tube. The extrusion temperature of the fifth twin-screw extruder is 170-190°C in zone 1; 190-210°C in zone 2; 210-230°C in zone 3; and 220-240°C in zone 4.

[0063] Comparative Example 1 A multi-layer polyolefin tube, which is different from Example 1 in that polyketone is not added to the raw materials of the oxygen barrier layer.

[0064] Comparative Example 2 A multi-layer polyolefin tube, which is different from Example 1 in that no light stabilizer is added to the raw materials of the protective layer.

[0065] Comparative Example 3 A multi-layer polyolefin tube is different 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.

[0066] Comparative Example 4 A multi-layer polyolefin tube is different 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.

[0067] Comparative Example 5 A multi-layer polyolefin tube is different from Example 1 in that the weight ratio of the polyethylene resin, the antioxidant, and the light stabilizer in the protective layer is 100:0.6:0.1.

[0068] Comparative Example 6 A multi-layer polyolefin tube is different from Example 1 in that the weight ratio of the polyethylene resin, the antioxidant, and the light stabilizer in the protective layer is 100:0.6:4.

[0069] Comparative Example 7 A multilayer polyolefin tube is different from Example 1 in that polyethylene glycol of equal mass is used instead of ethylene-vinyl alcohol copolymer.

[0070] Comparative Example 8 A multi-layer polyolefin tube, which is different from Example 1 in that polyacrylic acid of equal mass is used instead of polyamide.

[0071] Performance testing 1. Oxygen permeability: Tested in accordance with Method II in GB / T 34437-2017.

[0072] 2. Hydrostatic pressure: Tested in accordance with GB / T 28799.2-2020 (polyethylene), GBT 19473.2-2020 (polybutylene), and GB / T18742.2-2017 (polypropylene).

[0073] 3. Hot and cold water circulation: Test in accordance with GB / T 19993-2005.

[0074] 4. Xenon lamp aging: Tested in accordance with ASTM D2565-2016.

[0075] The above test results are shown in Table 1.

[0076] Table 1 It can be seen from Table 1 that the multilayer polyolefin tube of the present invention has excellent light aging resistance and long-term oxygen barrier stability.

[0077] 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, resulting in 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. This shows that the present invention, by adding polyketone to the oxygen barrier layer and a light stabilizer to the protective layer, improves the light aging resistance and long-term oxygen barrier stability of the multilayer polyolefin tube.

[0078] 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 ethylene-vinyl alcohol copolymer content is too high, the oxygen barrier layer's water absorption increases after hot and cold water circulation, significantly increasing the oxygen permeability. Excessive polyketone content can make the oxygen barrier layer more susceptible to degradation under UV light aging, reducing the light aging resistance of the multilayer polyolefin tube. Therefore, the present invention improves the light aging resistance and long-term oxygen barrier stability of the multilayer polyolefin tube by controlling the weight ratio of polyketone, ethylene-vinyl alcohol copolymer, and compatibilizer to (80-100): (8-25): (1-6).

[0079] Comparing Comparative Examples 5-6 with Example 1, we can see that if the light stabilizer content in the protective layer is too low, it will be difficult to prevent the decomposition of POK in the oxygen barrier layer under UV irradiation, resulting in a significant increase in oxygen permeability and a decrease in the light aging resistance of the multilayer polyolefin tube. If the light stabilizer content is too high, it may affect the performance of the tube and, in turn, its light aging resistance. Therefore, the present invention, by controlling the weight ratio of polyolefin resin, antioxidant, and light stabilizer to (90-100): (0.1-0.6): (0.2-3), can prevent the decomposition of POK in the oxygen barrier layer under UV irradiation, thereby improving the light aging resistance and long-term oxygen barrier stability of the multilayer polyolefin tube.

[0080] Comparing Comparative Examples 7 and 8 with Example 1, we can see that in Comparative Example 7, an equal amount of polyethylene glycol was used to replace the ethylene-vinyl alcohol copolymer. However, polyethylene glycol lacks oxygen barrier properties, resulting in a decrease in oxygen barrier performance. The initial oxygen permeability value cannot meet the requirements for oxygen barrier performance. This demonstrates that not all polymers combined with polyketone can achieve excellent long-term oxygen barrier stability in multilayer polyolefin tubes. Furthermore, in Comparative Example 8, an equal amount of polyacrylic acid was used to replace the polyamide. POK and EVOH are not well compatible, resulting in a decrease in the oxygen barrier performance of the oxygen barrier layer. The initial oxygen permeability value is no longer sufficient for oxygen barrier performance. This demonstrates that not all compatibilizers can achieve excellent long-term oxygen barrier stability and light aging resistance in multilayer polyolefin tubes.

[0081] 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 the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A multilayer polyolefin tube, characterized in that: The invention comprises, from the inside to the outside, 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, 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 (90-100): (0.1-0.6): (0.2-3).

2. The multilayer polyolefin pipe according to claim 1, wherein 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 according to claim 1, wherein The weight ratio of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer in the oxygen barrier layer is (80-90): (10-20): (2-5); And / or, the weight ratio of the polyolefin resin, antioxidant and light stabilizer in the protective layer is 100: (0.2-0.4): (0.5-2).

4. The multilayer polyolefin pipe according to claim 1, wherein The polyolefin layer includes one of a polyethylene layer, a polypropylene layer, and a polybutylene layer.

5. The multilayer polyolefin pipe according to claim 4, wherein The polyethylene layer is one of a high-density polyethylene layer, a heat-resistant polyethylene layer, and a cross-linked polyethylene layer.

6. The multilayer polyolefin pipe according to claim 4, wherein The polypropylene layer is one of a copolymerized polypropylene layer and a block copolymerized polypropylene layer.

7. The multilayer polyolefin pipe according to claim 1, wherein The first adhesive layer and the second adhesive layer are both hot melt adhesive layers.

8. The multi-layer polyolefin pipe according to claim 1, wherein 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 according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) adding a polyolefin resin into a first twin-screw extruder and extruding the polyolefin resin to obtain a polyolefin layer; (2) adding the raw materials of the first adhesive layer into a second twin-screw extruder and extruding and coating the raw materials on the outer surface of the polyolefin layer to obtain the first adhesive layer; (3) adding a mixture of polyketone, ethylene-vinyl alcohol copolymer and compatibilizer into a third twin-screw extruder and extruding and coating the mixture on the outer surface of the first adhesive layer to obtain an oxygen barrier layer; (4) adding the raw materials of the second adhesive layer into a fourth twin-screw extruder, and extruding and coating the raw materials on the outer surface of the oxygen barrier layer to obtain the second adhesive layer; (5) Adding a mixture of polyolefin resin, antioxidant and light stabilizer into a fifth twin-screw extruder, extrusion coating the mixture on the outer surface of the second adhesive layer to obtain a protective layer; finally, vacuum sizing and cooling to obtain a multilayer polyolefin tube.

10. The method for preparing a multilayer polyolefin pipe according to claim 9, wherein: The extrusion temperature of the first twin-screw extruder is 140-240°C; the extrusion temperature of the second twin-screw extruder is 150-225°C; the extrusion temperature of the third twin-screw extruder is 170-240°C; the extrusion temperature of the fourth twin-screw extruder is 150-225°C; and the extrusion temperature of the fifth twin-screw extruder is 140-240°C.

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