Adhesive material for multilayer nylon pipe containing an evo h layer and method for producing the same

Abstract

This invention provides an adhesive material for multilayer nylon tubing containing an EVOH layer and its preparation method, belonging to the field of polymer materials technology. The adhesive material comprises the following components: long-chain nylon resin, compatibilizer, plasticizer, bisphenol A epoxy resin, maleic anhydride-grafted EVA, antioxidant, and lubricant. The LLDPE-g-MAH in the adhesive material provided by this invention exhibits good flexibility and flowability, and its molecular structure simultaneously contains polyethylene molecular chains and anhydride groups, resulting in excellent compatibility with both long-chain nylon and EVOH. The adhesive material provided by this invention simultaneously contains maleic anhydride-grafted EVA and bisphenol A epoxy resin. Through the combined use of these components, a good synergistic effect is formed, improving the bonding strength of the adhesive layer, increasing resistance to heat and water, and solving the problem of delamination in multilayer nylon tubing after heat-induced fuel immersion.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a multilayer nylon tube adhesive material containing an EVOH layer and its preparation method. Background Technology

[0002] In the early 19th century, automotive fuel lines used metal tubing. Because the lines were connected by threads, fuel leaks were common, posing a significant safety hazard. Furthermore, the manufacturing process was costly and time-consuming. Later, rubber tubing evolved from metal tubing. While rubber tubing offered no issues with connection or safety, it was thicker, took up more space, and wasn't significantly lighter than metal tubing. Most importantly, the rubber compounding process was toxic, hindering environmental protection and energy conservation. Finally, multi-layer nylon tubing was developed. Multi-layer nylon tubing met the demands of the automotive industry, possessing excellent corrosion and chemical resistance; good flexibility and abrasion resistance; superior high-temperature resistance and penetration protection; and excellent lightweight and environmental performance.

[0003] Multilayer nylon tubing primarily utilizes the excellent high and low temperature resistance, corrosion resistance, chemical solvent resistance, and zinc chloride resistance of long-chain nylon. However, long-chain nylon has poor resistance to fuel permeation, necessitating the addition of an anti-permeation material, namely the EVOH layer.

[0004] EVOH (ethylene-vinyl alcohol copolymer) generally contains 25-45% ethylene and is a high barrier material with excellent processing performance and gas barrier properties. The material itself has a large number of hydroxyl groups, and its barrier effect is mainly determined by the content of vinyl alcohol.

[0005] EVOH possesses excellent oil and organic solvent resistance, as well as superior transparency, gloss, mechanical properties, elasticity, abrasion resistance, cold resistance, and surface hardness. EVOH also effectively prevents the penetration of gases such as oxygen and carbon dioxide; its gas barrier properties are 100 times higher than PA and 1000 times higher than PE and PP. Along with vinylidene chloride (PVDC) and polyacrylonitrile (PAN), it is currently recognized worldwide as one of the three highest barrier materials.

[0006] However, EVOH also has drawbacks. It is prone to moisture absorption, and its barrier properties decrease significantly after moisture absorption. Therefore, in daily use, EVOH is used as an intermediate layer and requires adhesive materials to bond it to long-chain nylon. According to the principle of "like dissolves like," common components are easier to bond. The bonding between the adhesive material and the long-chain nylon is relatively easier to solve, but the bonding with EVOH is more difficult. Especially in the case of heat-resistant fuel immersion, delamination has always been a problem in the materials industry. Delamination mainly involves the separation of the adhesive material from the EVOH layer. Improving the bonding strength between the adhesive material and EVOH is the key to solving this technical problem. Summary of the Invention

[0007] Based on this, the purpose of the present invention is to provide an adhesive material for multilayer nylon tubes containing an EVOH layer and a method for preparing the same, so as to solve the problems mentioned in the background art.

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

[0009] This invention provides an adhesive material for multilayer nylon tubing containing an EVOH layer, comprising the following raw materials in parts by weight:

[0010] 40-80 parts of long-chain nylon resin,

[0011] 5-20 parts compatibilizer

[0012] 5-10 parts plasticizer

[0013] 1-5 parts of bisphenol A type epoxy resin

[0014] 5-10 parts of maleic anhydride grafted onto EVA

[0015] Antioxidant 0.2-1 part,

[0016] Lubricant 0.2-0.7 parts,

[0017] Long-chain nylon resin is a high-viscosity resin with a relative viscosity of 4-5. Long-chain nylon has a low melting point, low water absorption, and a certain degree of flexibility. The use of long-chain nylon resin can enhance the bonding force between adhesive materials and the nylon layer in nylon tubes.

[0018] The compatibilizer is maleic anhydride-grafted polyolefin, preferably linear low-density polyethylene grafted with maleic anhydride (LLDPE-g-MAH). The function of LLDPE-g-MAH is to achieve common bonding with the EVOH layer. The ethylene structure contained in LLDPE-g-MAH has good compatibility with EVOH. In addition, considering the flexibility of adhesive materials, soft materials are generally used, and LLDPE-g-MAH can meet the above performance requirements. Moreover, LLDPE-g-MAH has a significant price advantage and low cost.

[0019] Bisphenol A type epoxy resins include at least one of E20, E51, E19, and NPEL-128. The main chain of bisphenol A type epoxy resins contains two benzene rings bridged by isopropyl groups, giving it high rigidity and thermal stability, reducing the risk of scorching and carbonization of adhesive materials during extrusion. Furthermore, the coexistence of ether bonds (-O-), secondary hydroxyl groups (-OH), and epoxy end groups in the molecular structure of bisphenol A type epoxy resins enhances the intermolecular forces, and the high density of epoxy groups at both ends results in significantly higher reactivity than general alicyclic epoxy resins, leading to better processability and excellent heat resistance and flowability.

[0020] Antioxidants include primary antioxidants and secondary antioxidants. The primary antioxidant is at least one or more of antioxidants 245, 1010, 1098, and 9228, and the secondary antioxidant is at least one of antioxidants 168 and 626. Antioxidants improve the antioxidant effect of materials.

[0021] The lubricant is at least one or more of PETS, OP wax, silicone, silicone oil and mesoamide, which improves the processing performance of the material.

[0022] Plasticizers include at least one of N-butylbenzenesulfonamide, benzoate plasticizers, and plasticizer JZ-218. The role of plasticizers is to improve the ductility and impact resistance of the adhesive layer and reduce the risk of cracking after curing.

[0023] The present invention also provides a method for preparing the adhesive material described above, comprising the following steps:

[0024] Weigh each component according to the mass percentage, mix the long carbon chain nylon resin, LLDPE-g-MAH, maleic anhydride grafted EVA and bisphenol A type epoxy resin evenly, then add lubricant and antioxidant and mix evenly to obtain the mixture.

[0025] The mixture is added to the main feed port of a twin-screw extruder, and the plasticizer is injected from the side feed port through a liquid pump. After melting, extrusion, cooling, air drying and pelletizing, a multi-layer nylon tube adhesive material containing an EVOH layer is obtained.

[0026] The adhesive material provided by this invention meets the requirements for multi-layer plastic fuel lines used in automobiles (Standard for Multi-layer Plastic Fuel Lines for Automobiles QC-T 798-2008), conforming to the requirements of its industry standard QC / T 798-2008. It is suitable for multi-layer plastic fuel lines with a normal operating temperature between -40℃ and +115℃ (continuous operating temperature not exceeding 90℃) and a maximum operating pressure not exceeding 0.7MPa. Furthermore, after 500 hours of fuel resistance testing, the interlayer bonding strength remained excellent. Inspection of the edges of the sheared portion of the multi-layer pipe after the test revealed no signs of delamination between the layers in the sheared area.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] The LLDPE-g-MAH compatibilizer in the adhesive material provided by this invention exhibits excellent flexibility and flowability. Furthermore, its molecular structure contains both polyethylene molecular chains and acid anhydride groups, resulting in excellent compatibility with long-chain nylon and EVOH. The adhesive material also contains maleic anhydride-grafted EVA and bisphenol A type epoxy resin. Through the combined use of these components, a synergistic effect is achieved, improving the bonding strength of the adhesive layer, increasing its resistance to heat and water, and solving the problem of delamination in multilayer nylon tubes after heat-induced fuel immersion.

[0029] The maleic anhydride-grafted EVA used in this invention consists of a basic ethylene-vinyl acetate (EVA) copolymer backbone and maleic anhydride-grafted side groups. The EVA backbone provides flexibility, while the anhydride groups in the side chains are strongly polar groups. These polar groups form an amphiphilic structure with the non-polar EVA backbone, giving the maleic anhydride-grafted EVA both polar and non-polar properties. This increases the bonding between adhesive components and enhances the adhesion to EVOH. Furthermore, the EVA backbone of the maleic anhydride-grafted EVA contains vinyl acetate (-CH2-CH(OCOCH3)-) units. The acetoxy groups in these units, along with the anhydride groups in the side chains, bond with hydrogen atoms in the secondary hydroxyl and alkyl groups of the bisphenol A epoxy resin through hydrogen bonds, further promoting the interaction between the components. This invention utilizes the synergistic effect between maleic anhydride-grafted EVA and bisphenol A epoxy resin to further enhance the adhesion between the adhesive material and the EVOH layer.

[0030] This invention, through innovative material and process design, significantly improves the adhesion between the adhesive layer and the nylon and EVOH layers. The extruded pipe slices exhibit tight bonding between layers without delamination. Even after immersion in high-temperature fuel oil for 120 hours, no delamination occurs, and peeling is not performed under force. Performance testing conforms to the automotive industry standard "Standard for Multi-Layer Plastic Fuel Pipes for Automobiles" QC-T 798 2008. It achieves the performance of similar materials from well-known international companies, meets product requirements, and has excellent prospects for widespread application. Detailed Implementation

[0031] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0033] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0034] The lubricant is a silicone masterbatch manufactured by Dow Corning, with the brand name MB50-002.

[0035] The main antioxidant is antioxidant 1098, manufactured by Tianjin Lianlong New Materials Co., Ltd.

[0036] The auxiliary antioxidant is antioxidant 168, manufactured by Tianjin Lianlong New Materials Co., Ltd.

[0037] The compatibilizer is LLDPE-g-MAH, manufactured by Shenyang Ketong Plastics Co., Ltd., and its grade is NJM3025. The grade NJM3025 is a refined LLDPE-g-MAH, which can avoid the formation of lumps compared to ordinary grafting materials. This invention selects this grade of material as the raw material through the selection of various raw materials, which can make the product performance optimal.

[0038] Maleic anhydride grafted EVA, manufactured by DuPont, USA, with the grade 21E533.

[0039] Bisphenol A type epoxy resin, manufactured by Nan Ya Chemical, brand name E20;

[0040] Plasticizer, manufactured by Suzhou Jinzhong Chemical Co., Ltd., brand name JZ-218

[0041] The long-chain nylon resin, manufactured by Huitong Special Materials Technology Co., Ltd., is grade HB-50 (PA612) with a relative viscosity of 4.8.

[0042] All materials are commercially available, commonly used products.

[0043] It is understood that the above-mentioned raw materials and reagents are merely examples of some specific embodiments of the present invention, making the technical solution of the present invention clearer, and do not mean that the present invention can only use the above-mentioned reagents. The specific scope shall be determined by the claims. In addition, unless otherwise specified, "parts" in the examples and comparative examples refer to parts by weight.

[0044] Any range described in this invention includes the endpoint, any value between the endpoints, and any subrange consisting of the endpoint or any value between the endpoints.

[0045] Example 1

[0046] A method for preparing a multilayer nylon tubing adhesive material containing an EVOH layer includes the following steps:

[0047] Weighing: First, dry the long-chain nylon resin PA612, maleic anhydride-grafted EVA and bisphenol A epoxy resin E20 at 80℃ for 4 hours for later use; then weigh the following raw materials: 12 parts compatibilizer, 0.6 parts lubricant, 0.2 parts main antioxidant, 0.2 parts auxiliary antioxidant, 10 parts maleic anhydride-grafted EVA, 3 parts bisphenol A epoxy resin, 6 parts plasticizer, and 68 parts PA612 resin;

[0048] Mixing: Add the weighed PA612, bisphenol A epoxy resin, compatibilizer, and maleic anhydride-grafted EVA to a high-speed mixer, mix at high speed for 5 minutes, then add the weighed lubricant, primary antioxidant, and secondary antioxidant and continue mixing at high speed for 5 minutes to obtain the mixture.

[0049] Melt extrusion: The mixture is added to the main feed of a twin-screw extruder, and the plasticizer is injected through the liquid injection port of a liquid pump. The temperature of the twin-screw extruder from the first zone to the die head is 65℃ (to prevent resin from clumping at the feed port), 215℃, 235℃, 235℃, 235℃, 230℃, 230℃, 230℃, 230℃, 230℃, 230℃, 245℃; the screw speed is 300 r / min, and the feed rate is 20 r / min.

[0050] Extrusion pelletizing: The extruded material is cooled, dried, pelletized, passed through a vibrating screen, homogenized in a homogenizing tank, and packaged to obtain the finished product, which is the corresponding adhesive material.

[0051] Example 2

[0052] Compared with Example 1, the difference in this example lies in the amount of each raw material used; all other processes are the same as in Example 1. The amounts of each raw material used in this example are as follows:

[0053] Compatibilizer 20 parts, lubricant 0.6 parts, main antioxidant 0.2 parts, auxiliary antioxidant 0.2 parts, maleic anhydride grafted EVA 10 parts, bisphenol A type epoxy resin 3 parts, plasticizer 6 parts, PA612 resin 60 parts.

[0054] Example 3

[0055] Compared with Example 1, the difference in this example lies in the amount of each raw material used; all other processes are the same as in Example 1. The amounts of each raw material used in this example are as follows:

[0056] 5 parts compatibilizer, 0.6 parts lubricant, 0.2 parts primary antioxidant, 0.2 parts secondary antioxidant, 10 parts maleic anhydride-grafted EVA, 3 parts bisphenol A epoxy resin, 6 parts plasticizer, and 75 parts PA612 resin.

[0057] Example 4

[0058] Compared with Example 1, the difference in this example lies in the amount of each raw material used; all other processes are the same as in Example 1. The amounts of each raw material used in this example are as follows:

[0059] Compatibilizer 12 parts, lubricant 0.2 parts, main antioxidant 0.4 parts, auxiliary antioxidant 0.4 parts, maleic anhydride grafted EVA 5 parts, bisphenol A type epoxy resin 5 parts, plasticizer 5 parts, PA612 resin 72 parts.

[0060] Example 5

[0061] Compared with Example 1, the difference in this example lies in the amount of each raw material used; all other processes are the same as in Example 1. The amounts of each raw material used in this example are as follows:

[0062] Compatibilizer 12 parts, lubricant 0.4 parts, main antioxidant 0.3 parts, auxiliary antioxidant 0.3 parts, maleic anhydride grafted EVA 10 parts, bisphenol A type epoxy resin 1 part, plasticizer 8 parts, PA612 resin 61 parts.

[0063] Comparative Example 1

[0064] Compared with Example 1, the difference in this comparative example lies in the amount of each raw material used; all other processes are the same as in Example 1. The amounts of each raw material used in this comparative example are as follows:

[0065] Compatibilizer 12 parts, lubricant 0.6 parts, main antioxidant 0.2 parts, auxiliary antioxidant 0.2 parts, maleic anhydride grafted EVA 10 parts, bisphenol A type epoxy resin 0 parts, plasticizer 6 parts, PA612 resin 71 parts.

[0066] Comparative Example 2

[0067] Compared with Example 1, the difference in this comparative example lies in the amount of each raw material used; all other processes are the same as in Example 1. The amounts of each raw material used in this comparative example are as follows:

[0068] Compatibilizer 12 parts, lubricant 0.6 parts, main antioxidant 0.2 parts, auxiliary antioxidant 0.2 parts, maleic anhydride grafted EVA 10 parts, bisphenol A type epoxy resin 6 parts, plasticizer 6 parts, PA612 resin 65 parts.

[0069] Comparative Example 3

[0070] Compared with Example 1, the difference in this comparative example lies in the amount of each raw material used; all other processes are the same as in Example 1. The amounts of each raw material used in this comparative example are as follows:

[0071] Compatibilizer 12 parts, lubricant 0.6 parts, main antioxidant 0.2 parts, auxiliary antioxidant 0.2 parts, maleic anhydride grafted EVA 10 parts, bisphenol A type epoxy resin 3 parts, plasticizer 11 parts, PA612 resin 63 parts.

[0072] Comparative Example 4

[0073] Compared with Example 1, the difference in this comparative example lies in the amount of each raw material used; all other processes are the same as in Example 1. The amounts of each raw material used in this comparative example are as follows:

[0074] Compatibilizer 12 parts, lubricant 0.6 parts, main antioxidant 0.2 parts, auxiliary antioxidant 0.2 parts, maleic anhydride grafted EVA 4 parts, bisphenol A type epoxy resin 3 parts, plasticizer 6 parts, PA612 resin 74 parts.

[0075] Comparative Example 5

[0076] Compared with Example 1, the difference in this comparative example lies in the amount of each raw material used; all other processes are the same as in Example 1. The amounts of each raw material used in this comparative example are as follows:

[0077] Compatibilizer 12 parts, lubricant 0.6 parts, main antioxidant 0.2 parts, auxiliary antioxidant 0.2 parts, maleic anhydride grafted EVA 16 parts, bisphenol A type epoxy resin 3 parts, plasticizer 6 parts, PA612 resin 62 parts.

[0078] Comparative Example 6

[0079] Compared with Example 1, the difference in this comparative example lies in the amount of each raw material used; all other processes are the same as in Example 1. The amounts of each raw material used in this comparative example are as follows:

[0080] Compatibilizer 12 parts, lubricant 0.6 parts, main antioxidant 0.2 parts, auxiliary antioxidant 0.2 parts, maleic anhydride grafted EVA 13 parts, bisphenol A type epoxy resin 0 parts, plasticizer 6 parts, PA612 resin 68 parts.

[0081] Comparative Example 7

[0082] Compared with Example 1, the difference in this comparative example lies in the amount of each raw material used; all other processes are the same as in Example 1. The amounts of each raw material used in this comparative example are as follows:

[0083] Compatibilizer 12 parts, lubricant 0.6 parts, main antioxidant 0.2 parts, auxiliary antioxidant 0.2 parts, maleic anhydride grafted EVA 0 parts, bisphenol A type epoxy resin 13 parts, plasticizer 6 parts, PA612 resin 68 parts.

[0084] The materials prepared in each embodiment and comparative example were subjected to performance and application tests. The application test was a tube extrusion test (the tube was a five-layer nylon tube, from the inside out: PA612 layer, adhesive layer, EVOH layer, adhesive layer, PA12 layer. The layer thicknesses were 0.2 mm, 0.1 mm, 0.15 mm, 0.1 mm, and 0.45 mm, respectively). Due to insufficient liquid pump flow and unstable injection volume, some materials prepared in the comparative example had poor flowability and could not be extruded, resulting in the inability to prepare products. Therefore, some tests could not be performed, resulting in no data. The performance test methods and conditions are shown in Table 1; the test results are shown in Tables 2 and 3.

[0085] Table 1

[0086]

[0087] Table 2

[0088]

[0089] Note: NB in ​​the table means that the impact specimen did not break even when it was outside the measurement range during the test; the same applies to Table 3.

[0090] Table 3

[0091]

[0092] Note: Comparative Examples 2 and 5 failed to produce any products due to changes in the ratio of raw materials used, therefore no relevant test data is available.

[0093] The test results in the table above show that the materials prepared in Examples 1 to 5 can be extruded smoothly, have good mechanical properties, a flexural modulus of less than 600 MPa, good flexibility, and are suitable for extruded pipes. The extrusion process is smooth, the pipe wall is smooth, and the interlayer bonding is tight when the cross-section of the pipe is cut open. The interlayer does not separate after being immersed in fuel at 60°C for 120 hours. Even when forcibly peeled off with tweezers, no separation occurs.

[0094] The test results from Examples 1-5 show that maleic anhydride-grafted EVA at a concentration between 5-10% provides excellent auxiliary bonding. Even when the amounts of maleic anhydride-grafted EVA and bisphenol A epoxy resin are within reasonable limits, the bonding effect remains satisfactory.

[0095] The test results of Comparative Example 1 show that, in the absence of bisphenol A type epoxy resin, the interlayer adhesion of the obtained product is insufficient, and some delamination occurs between the two layers during the fuel impregnation process.

[0096] The test results of Comparative Example 2 show that when the amount of bisphenol A type epoxy resin is high, the active groups such as epoxy in it have a strong chain extension effect, which causes it to stick to the metal wall of the extruder, reducing its fluidity and causing degradation due to the residence time in the machine.

[0097] The results of Comparative Example 3 show that when the amount of plasticizer is high, reaching 11 parts, the plasticizer is heated and precipitated during the extrusion process, forming an oil film at the interface layer. The adhesion between the adhesive layer and the EVOH layer is poor, and the two layers are easy to separate during the fuel immersion test.

[0098] The results of Comparative Example 4 show that when the amount of maleic anhydride-grafted EVA is low, the interlayer structure bonding is not strong, and it will detach in the subsequent related fuel immersion test, failing to meet the product requirements.

[0099] The results of Comparative Example 5 show that when the amount of maleic anhydride-grafted EVA is too high, a certain cross-linking effect is produced, which leads to reduced fluidity, affects the mixing effect of the adhesive layer and the polyamide layer, and results in weak bonding. Crystal points and small lumps are generated during the extrusion process, which affects the bonding effect and appearance. In subsequent related fuel immersion tests, detachment occurs, and the product requirements are not met.

[0100] The results of Comparative Example 6 show that when no bisphenol A epoxy resin is added and all the bisphenol A epoxy resin is replaced with maleic anhydride-grafted EVA, there are no abnormalities in the production process. However, due to the limited adhesion, after the heat-resistant fuel is burned, the cross-section shows separation between the adhesive layer and the nylon layer.

[0101] The results of Comparative Example 7 show that when maleic anhydride-grafted EVA is not added and all the parts of maleic anhydride-grafted EVA are replaced with bisphenol A type epoxy resin, there are no abnormalities in the production process. However, due to the limited adhesion, after the heat-resistant fuel is burned, the cross-section is cut open and observed to show that the glue layer and the EVOH layer are separated.

[0102] The results of Comparative Examples 6 and 7 show that maleic anhydride-grafted EVA and bisphenol A type epoxy resin have a synergistic effect. A single component cannot pass the hot fuel immersion test. By combining maleic anhydride-grafted EVA and bisphenol A type epoxy resin, the bonding performance of the adhesive can be improved, so that it can pass the hot fuel immersion test when applied to nylon pipes.

[0103] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0104] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. An adhesive material for multilayer nylon tubing containing an EVOH layer, characterized in that, The adhesive material comprises, by weight, the following raw materials: 40-80 parts of long-chain nylon resin, 5-20 parts compatibilizer 5-10 parts plasticizer 1-5 parts of bisphenol A type epoxy resin 5-10 parts of maleic anhydride grafted onto EVA Antioxidant 0.2-1 part, Lubricant 0.2-0.7 parts; The compatibilizer is linear low-density polyethylene grafted with maleic anhydride.

2. The adhesive material for multilayer nylon tubing containing an EVOH layer according to claim 1, characterized in that, The bisphenol A type epoxy resin is at least one of E20, E51, E19, and NPEL-128.

3. The adhesive material for multilayer nylon tubing containing an EVOH layer according to claim 1, characterized in that, The plasticizer is at least one of N-butylbenzenesulfonamide and benzoic acid ester plasticizers.

4. The adhesive material for multilayer nylon tubing containing an EVOH layer according to claim 1, characterized in that, The relative viscosity of the long-chain nylon resin is 4-5.

5. The adhesive material for multilayer nylon tubing containing an EVOH layer according to claim 1, characterized in that, The antioxidants include primary antioxidants and secondary antioxidants.

6. The adhesive material for multilayer nylon tubing containing an EVOH layer according to claim 5, characterized in that, The primary antioxidant is at least one of antioxidant 245, antioxidant 1010, antioxidant 1098, and antioxidant 9228.

7. The adhesive material for multilayer nylon tubing containing an EVOH layer according to claim 5, characterized in that, The auxiliary antioxidant is at least one of antioxidant 168 and antioxidant 626.

8. The adhesive material for multilayer nylon tubing containing an EVOH layer according to claim 1, characterized in that, The lubricant is at least one of PETS, OP wax, silicone, silicone oil, and mesoamide.

9. The method for preparing the adhesive material for multilayer nylon tubing containing an EVOH layer as described in any one of claims 1 to 8, characterized in that, Includes the following steps: After mixing long-chain nylon resin, LLDPE-g-MAH, maleic anhydride-grafted EVA, and bisphenol A epoxy resin evenly, lubricant and antioxidant are added and mixed evenly to obtain a mixture. The mixture is added to the main feed port of a twin-screw extruder, and the plasticizer is injected from the side feed port through a liquid pump. After melting, extrusion, cooling, air drying, and pelletizing, the adhesive material is obtained.

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