Hot melt adhesive for bonding thermoplastic elastomer as well as preparation method and application of hot melt adhesive

Abstract

The invention discloses a hot melt adhesive for bonding a thermoplastic elastomer as well as a preparation method and application of the hot melt adhesive. The hot melt adhesive is prepared from the following raw materials: 40 to 80 parts of polyester type thermoplastic polyurethane, 20 to 60 parts of polyolefin elastomer, 0.5 to 10 parts of glycidyl methacrylate, 0.05 to 1 part of free radical initiator and 0.5 to 1 part of antioxidant. During preparation, a twin-screw reactive extrusion process is adopted, and in-situ grafting and ring-opening reaction are realized in melt blending by utilizing GMA, so that in-situ compatibilization of TPU and POE is completed. According to the method, the problems of gel and fluidity of MAH grafting are solved, and the incompatibility of TPU / POE is overcome. The obtained hot melt adhesive has the advantages of high melt index and extremely low gel content (lt; 0.5%), which has excellent peel strength (gt; 40N / 25mm) and cohesive failure are achieved, prime coat treatment is not needed, and the application prospect is wide.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high polymer material science and adhesive technology, and particularly relates to a hot melt adhesive for bonding thermoplastic elastomer, a preparation method and application thereof. BACKGROUND

[0002] In modern automobile manufacturing, medical device packaging and high-end consumer electronics assembly, multi-material composite bonding technology plays a crucial role. Thermoplastic elastomer (TPE), especially TPE based on styrene block copolymer and thermoplastic vulcanized rubber (TPV), has become the first choice for soft-touch handles, seals and flexible components due to its excellent flexibility, weather resistance, touch and easy processability. However, TPE materials are non-polar polymers in chemical nature, with extremely low surface energy and lack of active functional groups in the molecular chain. This inherent chemical inertness makes it extremely difficult for TPE to be effectively wetted and bonded by conventional polar adhesives (such as polyurethane adhesive, epoxy resin adhesive or acrylic ester adhesive), forming a widely recognized "bonding difficulty" in the industry.

[0003] Thermoplastic polyurethane (TPU) as a high-performance polar block copolymer, composed of hard segments (isocyanate and chain extender) and soft segments (polyester or polyether polyol), has excellent wear resistance, high elasticity and adjustable mechanical strength, and is an ideal hot melt adhesive matrix material. However, when trying to directly use polar TPU hot melt adhesive to bond non-polar TPE substrates, due to the significant difference in solubility parameters between the two, the interfacial thermodynamic affinity is poor, usually resulting in too low bonding strength, and the failure mode is mostly interfacial debonding, which cannot meet the requirements of structural bonding.

[0004] In the face of this technical bottleneck, the existing technology mainly adopts the following two solutions, but both have obvious limitations:

[0005] One is the surface pretreatment method, which is also the most commonly used method in the industry. That is, before gluing, a layer of primer is coated on the surface of the TPE substrate. The primer usually contains chlorinated polyolefin (CPO) or other modified resins and is dissolved in organic solvents such as toluene and xylene. Although this method can effectively improve the bonding strength, the use and emission of volatile organic compounds (VOC) in the primer brings serious environmental pollution and occupational health risks, and increases the complexity and time cost of the process.

[0006] Secondly, physical blending method, namely trying to melt blend non-polar polymer (such as POE) with TPU to dilute the polarity of TPU and improve its affinity to non-polar substrate. However, TPU and POE are completely incompatible in thermodynamics. The physical blend will be seriously phase separated during melt processing and form coarse and unstable 'island-in-sea structure'. In this morphology, the dispersed phase (island) is usually micron or above, and there is lack of interfacial bonding force between the dispersed phase and the continuous phase (sea), which leads to sharp decrease of mechanical properties of the blend and the cohesive strength required as high-performance adhesive.

[0007] To solve the phase separation problem of physical blending, the industry has widely studied reactive compatibilizers, and the most common technique is to use maleic anhydride (MAH) grafted polyolefin elastomer (POE-g-MAH). In melt blending, the anhydride groups of MAH can theoretically react with the urethane bonds or terminal amino groups on the TPU backbone. However, there is a significant chemical defect in the MAH grafting technique: in the presence of free radical initiator, the polyolefin (especially ethylene-octene copolymer) is prone to crosslinking side reaction (gelation) of macromolecular chains. This crosslinking will cause the melt viscosity of hot melt adhesive to rise exponentially, the melt index (MFI) to decrease significantly, and insoluble and infusible gel particles to form. This not only makes the hot melt adhesive lose flowability and makes it difficult to perform precise gluing operation, but also may even block the extrusion equipment.

[0008] Therefore, it is a technical problem to be solved in the current industry to develop a new type of hot melt adhesive which can realize high-strength bonding of TPE and avoid gelation in the grafting process and maintain good flowability. SUMMARY

[0009] The purpose of the present application is to provide a hot melt adhesive for thermoplastic elastomer bonding and its preparation method and application.

[0010] To achieve the above purpose, the technical solution adopted by the present application is:

[0011] A hot melt adhesive for thermoplastic elastomer bonding, the raw materials of which comprise the following components in parts by weight:

[0012] 40-80 parts of polyester type thermoplastic polyurethane (TPU),

[0013] 20-60 parts of polyolefin elastomer (POE),

[0014] 0.5-10 parts of glycidyl methacrylate (GMA),

[0015] 0.05-1 part of free radical initiator,

[0016] 0.5-1 part of antioxidant.

[0017] In the above scheme, the polyester TPU, POE, GMA and free radical initiator are the core reaction components. The polyester TPU as the matrix of the hot melt adhesive provides excellent cohesive strength, heat resistance and adhesion to polar substrates (such as PET fabric). POE as a non-polar component gives the hot melt adhesive compatibility with non-polar TPE substrates.

[0018] In a further aspect, the polyester TPU is a product based on polyester polyol and diisocyanate; the polyester polyol is at least one selected from polycaprolactone (PCL) polyol, polyethylene adipate, and polybutylene adipate; the diisocyanate is at least one selected from methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), and hexamethylene diisocyanate (HDI); and the Shore hardness of the polyester TPU is 60A to 95A. Preferably, the polyester TPU is a product based on adipic acid polyester or polycaprolactone (PCL) polyol and methylene diphenyl diisocyanate (MDI).

[0019] It is crucial to select polyester TPU rather than polyether TPU. During synthesis or processing, the terminal of polyester polyol often remains a high concentration of carboxyl groups (-COOH), which is the key active site for ring-opening reaction with GMA epoxy groups. In contrast, the terminal of polyether TPU is mainly a low-activity hydroxyl group with large steric hindrance, making it difficult to achieve efficient chemical compatibilization. Experiments show that the peel strength of hot melt adhesive prepared using polyester TPU is significantly higher than that of polyether TPU.

[0020] In a further aspect, the polyolefin elastomer (POE) is an ethylene-octene copolymer or ethylene-butene copolymer synthesized using a metallocene catalyst, preferably an ethylene-octene copolymer with a density range of 0.857-0.885 g / cm³ and a melt index of 0.5-30 g / 10 min at 190°C / 2.16 kg.

[0021] Low-density POE has higher amorphous region content and flexibility, which is beneficial for wetting the TPE substrate surface at a lower temperature, and its side chain octene group helps to break the ethylene crystal, improving the grafting efficiency.

[0022] Further technical solutions, the free radical initiator is selected from one or several mixtures of dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (DBPH), di-tert-butyl peroxide (DTBP), benzoyl peroxide (BPO). Preferably dicumyl peroxide (DCP), its half-life temperature matches the processing temperature of reactive extrusion (170~200℃), ensuring that the initiator is completely decomposed in the reaction section of the screw, initiating the grafting reaction, and no premature decomposition occurs in the feeding section.

[0023] Further technical solutions, the antioxidant is selected from one or several mixtures of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010), tris[2,4-di-tert-butylphenyl] phosphite (antioxidant 168), n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1076). Preferably a mixture of tris[2,4-di-tert-butylphenyl] phosphite (antioxidant 168) and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010).

[0024] The addition of antioxidants needs to be strictly controlled, both to prevent thermal oxidative degradation of TPU and POE at high temperatures, and not to be excessive so as to quench free radicals and interfere with the grafting reaction.

[0025] Further technical solutions, the weight ratio of the polyester thermoplastic polyurethane (TPU) to the polyolefin elastomer (POE) is 50:50 to 70:30, and the gel content of the hot melt adhesive is less than 0.5%, and the T-type peeling strength of the styrene-ethylene-butylene-styrene block copolymer substrate (SEBS) is greater than 40N / 25mm.

[0026] Further, the application also discloses a preparation method of the hot melt adhesive for thermoplastic elastomer bonding.

[0027] Step one, in the drying equipment, the polyester TPU particles and POE particles are dried at 60~80℃ for 3~5 hours to remove water, preventing hydrolytic degradation of TPU during processing; at the same time, the solid free radical initiator (DCP) is dissolved in the liquid GMA monomer to prepare a uniform reaction aid liquid.

[0028] Step two, the dried polyester TPU, POE and antioxidant are added through the main feeding port of the twin-screw extruder.

[0029] Step three, after the melt conveying section of the twin-screw extruder screw, the reaction aid liquid prepared in step one is injected into the barrel by using a high-pressure liquid metering pump. At this time, the polymer is in a molten state, which is beneficial to the rapid dispersion of the monomer.

[0030] Step four, reactive extrusion is carried out by using a co-rotating twin-screw extruder. The temperature range of the reaction zone is set to 170-200℃, the screw rotation speed is 30-200rpm, and the residence time of the material in the barrel is controlled to be 2-5 minutes. In this process, cascade chemical reactions occur: first, DCP thermal decomposition generates primary free radicals; second, the free radicals capture hydrogen atoms on the POE chain to form macromolecular free radicals; third, GMA monomers are grafted onto the POE macromolecular chain to generate POE-g-GMA; and finally, ring-opening esterification reaction occurs between the epoxy groups of the POE-g-GMA side chain and the carboxyl groups at the end of the TPU to generate a TPU-POE block / graft copolymer.

[0031] Step five, a vacuum exhaust port is arranged at the end of the extruder (Z8 or Z9 zone), and under the vacuum degree of-0.08~-0.1MPa, unreacted GMA monomer residues and other small molecular volatile components are removed to ensure the environmental protection of the product.

[0032] Step six, the melt is extruded through a die, cooled and shaped in a water tank, air-dried, and then cut into particles to obtain the finished hot melt adhesive.

[0033] In a further technical solution, the twin-screw extruder is a co-rotating parallel twin-screw extruder, the length-diameter ratio (L / D) of which is 40:1 to 48:1, and the temperature setting range is: zone one is 60-110℃, zones two to three are 160-180℃, zones four to seven are 180-200℃, zones eight to nine are 180-190℃, and the die head is 170-185℃.

[0034] In a further technical solution, in step four, cascade chemical reactions occur: first, thermal decomposition of the free radical initiator generates primary free radicals; second, the free radicals capture hydrogen atoms on the polyolefin elastomer chain to form macromolecular free radicals; third, glycidyl methacrylate monomers are grafted onto the polyolefin elastomer macromolecular chain to generate polyolefin elastomer grafted glycidyl methacrylate; and finally, ring-opening esterification reaction occurs between the epoxy groups of the polyolefin elastomer grafted glycidyl methacrylate side chain and the carboxyl groups at the end of the polyester-based thermoplastic polyurethane to generate a TPU-POE block / graft copolymer.

[0035] Further, the application also discloses an application of the hot melt adhesive, which is used for bonding a non-polar thermoplastic elastomer (TPE) substrate and a polar substrate.

[0036] The polar substrate is at least one of polyester (PET) fabric, polycarbonate (PC), acrylonitrile-butadiene-styrene copolymer (ABS), and polyester thermoplastic polyurethane (TPU) film, and the adhesive joint shows cohesive failure of the adhesive body after the peel strength test.

[0037] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" or the like are open-ended, that is, meaning "including but not limited to".

[0038] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" or the like are open-ended, that is, meaning "including but not limited to".

[0039] The working principle and advantages of the present application are as follows:

[0040] The present application relates to a hot melt adhesive for thermoplastic elastomer bonding, and a preparation method and application thereof, which is based on graft copolymerization of thermoplastic polyurethane (TPU) and polyolefin elastomer (POE) and prepared by reactive extrusion using a twin-screw extruder.

[0041] The core of the present application is to replace the traditional maleic anhydride (MAH) with glycidyl methacrylate (GMA). The GMA molecule contains both a double bond that can participate in free radical reaction and an epoxy group that is easy to react with a polar group. Under certain process conditions, GMA can effectively inhibit the crosslinking side reaction of the POE molecular chain and significantly reduce gel formation. More importantly, the GMA epoxy group grafted onto the POE can react with the carboxyl group (-COOH) at the end of the polyester TPU to form a TPU-g-POE copolymer in situ. As a high-efficiency interfacial compatibilizer, the copolymer can significantly reduce the interfacial tension between the two phases, refine the dispersed phase particle size to the sub-micron level, and thus significantly improve the mechanical properties of the material.

[0042] The preparation process is a "one-pot" reaction extrusion: in the same extrusion process, the free radical initiator first initiates the grafting of GMA onto the alpha-carbon atom of POE; then, the GMA epoxy group grafted on the POE undergoes ring-opening addition reaction with the carboxyl or hydroxyl group at the end of the polyester TPU, and finally forms a TPU-g-POE block or graft copolymer in situ at the interface between the two phases.

[0043] Compared with MAH, GMA has a unique stabilizing effect on polyolefin macroradicals, and its grafting reaction rate is much higher than the coupling termination rate of macroradicals, thereby effectively competing and inhibiting the crosslinking between POE molecular chains. Test data show that the hot melt adhesive gel content prepared by the application can be controlled below 0.5%, and the melt index (MFI) is maintained at 7-13 g / 10min, fully meeting the requirements of subsequent processing processes such as injection molding, casting or spraying.

[0044] The TPU-g-POE copolymer generated in situ by the "one-pot method" of the application can closely connect the polar TPU phase and the non-polar POE phase, not only refining the phase structure, but also significantly improving the cohesive strength of the material. In T-type peeling test, the bonding strength can reach 40-55 N / 25mm, and the failure mode is cohesive failure, completely solving the common interface debonding problem of traditional physical blending.

[0045] In summary, the process of the application is simple, does not need to prepare a grafting material in advance, and can be directly mixed and extruded, with high production efficiency. At the same time, the hot melt adhesive can be directly applied to the TPE substrate without primer treatment, avoiding the use and discharge of organic solvents, and meeting the green and environmentally friendly industrial development trend. DETAILED DESCRIPTION

[0046] The application will be further described below in conjunction with examples:

[0047] The following detailed description will clearly illustrate the application, and any person skilled in the art can modify and modify the technology taught by the application without departing from the spirit and scope of the application.

[0048] The language used in this document is only for describing specific embodiments and is not intended to limit the application. The singular forms "a", "this", "this", "this" and "the" as used herein also include the plural forms.

[0049] Raw material description:

[0050] Polyester TPU (A): BASF Elastollan®685A, based on adipic acid polyester and MDI, Shore hardness 85A.

[0051] Polyether TPU (B): BASF Elastollan®1185A.

[0052] POE: Dow Engage®8150, ethylene-octene copolymer.

[0053] GMA: Glycidyl methacrylate, analytical pure.

[0054] MAH (for comparison): Maleic anhydride, analytical pure.

[0055] Initiator: Dicumyl peroxide (DCP).

[0056] Antioxidant: Irganox 1010 and Irgafos 168 compounded at 1:1.

[0057] Examples 1-5: A hot melt adhesive for thermoplastic elastomer (TPE) bonding, which is composed of the components shown in Table 1 in parts by weight.

[0058] Table 1 Examples 1-5

[0059]

[0060] Detailed preparation method:

[0061] The method for preparing the hot melt adhesive of Examples 1-5 and subsequent comparative examples includes the following steps:

[0062] Step one, drying and premixing: Put TPU (A) and POE particles into a dehumidifying dryer and dry at 80°C for 4 hours to ensure the moisture content <200 ppm. Add a measured amount of DCP initiator powder into the liquid GMA monomer, and magnetically stir until completely dissolved to prepare a uniform transparent reaction solution.

[0063] Step two, feeding: Use a co-rotating twin-screw extruder with a length-diameter ratio (L / D) of 44:1 (screw diameter 40 mm). Dry TPU, POE particles and antioxidant are added through a loss-on-ignition feeder from the main feeding port (Zone 0).

[0064] Step three, liquid injection: Use a high-pressure micro-injection pump to inject the GMA / DCP reaction solution prepared in step one from Zone 3 of the extruder barrel (after the melt closed section).

[0065] Step four, reaction extrusion: The screw rotation speed is set to 150 rpm. The temperature distribution is set as follows: Zone 1: 100°C; Zone 2-3: 160-170°C; Zone 4-8: 180-200°C, Zone 9 (vacuum exhaust): 180°C (vacuum degree -0.09 MPa); die head: 180°C.

[0066] Step five, granulation: After the extruded strip is cooled in a water tank and blown dry by an air knife, it is fed into a granulator for granulation, and then dried again at 80°C for 2 hours to remove surface moisture, finally obtaining hot melt adhesive granules, which are sealed and packaged.

[0067] In order to verify the technical effect of the present application, three groups of comparative examples were set. Comparative example 1 was simple physical blending without adding initiator, comparative example 2 was traditional MAH grafting, and comparative example 3 selected TPU as polyether type. The specific formula is shown in Table 2.

[0068] Table 2: Formula composition of comparative examples 1-3

[0069]

[0070] Performance test:

[0071] The hot melt adhesives obtained from examples 1-5 and comparative examples 1-3 of the present application were subjected to performance test, and the results are shown in Table 3.

[0072] Melt index (MFI): tested according to ASTM D1238 standard at 190℃ under 2.16kg load, unit g / 10min. This index reflects the flowability and processing performance of the material.

[0073] Gel content: accurately weigh 2g sample, extract with boiling xylene at 120℃ for 12 hours, filter, dry, weigh the insoluble matter. Gel content (%) = (insoluble matter mass / original sample mass) x 100%. This index reflects the degree of crosslinking side reaction.

[0074] T-type peeling strength: the hot melt adhesive was made into a 0.2mm film, placed between TPE sheet (SEBS-based, Shore 79A) and polyester fabric. Hot-pressed at 120℃ under 0.2MPa pressure for 180 seconds. After cooling for 24 hours, the universal testing machine was used to test the T-type peeling according to ASTM D1876 standard, with a tensile speed of 50mm / min.

[0075] Table 3: Performance test results

[0076]

[0077] As can be seen from the data in Table 3, with the increase of POE content (from example 5 to example 1), the melt index (MFI) of the material showed an upward trend. This is mainly due to the low viscosity of POE itself, which can play a lubricating role in the system. In terms of bonding strength, example 3 performed best, with a peeling strength of 50.4 N / 25mm. Analysis shows that at this ratio, the cohesive strength contributed by TPU and the interfacial affinity provided by POE achieve the best balance.

[0078] In contrast, Comparative Example 1 used simple physical blending, which had very low peel strength and failed to form effective bonding. Comparative Example 2 used a traditional maleic anhydride (MAH) grafting process, and the resulting hot melt adhesive had a very low melt index and a gel content as high as 35.6%, which did not have the application performance of a hot melt adhesive. This result verified the side effect of MAH easily initiating crosslinking of polyolefins under free radical conditions. In sharp contrast, Example 3 used the GMA system, which had a MFI of 10.2 g / 10 min, achieved high-strength bonding, and also ensured excellent processing fluidity. This was attributed to the unique stabilizing effect of GMA monomers on macroradicals, which preferentially underwent grafting reactions rather than crosslinking reactions.

[0079] In addition, Comparative Example 3 used a polyether TPU, which had a peel strength of only 22.6 N / 25 mm and an interfacial failure mode. This result strongly confirmed the mechanism of the present application: the carboxyl groups at the ends of the polyester TPU are the key reaction sites for chemical bonding with the epoxy groups of GMA. The polyether TPU lacks such high-activity sites, so the grafted GMA POE cannot effectively react with it, resulting in a significant decrease in compatibilization and the final bonding performance.

[0080] The above examples are only to illustrate the technical concepts and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A hot melt adhesive for thermoplastic elastomer bonding, characterized by: The raw materials include the following components by weight: polyester thermoplastic polyurethane 40~80 parts, polyolefin elastomer 20~60 parts, glycidyl methacrylate 0.5~10 parts, free radical initiator 0.05~1 part, antioxidant 0.5~1 part.

2. A hot melt adhesive for bonding thermoplastic elastomers according to claim 1, characterized in that: The polyester thermoplastic polyurethane is a product prepared by reacting polyester polyol with diisocyanate; the polyester polyol is selected from at least one of polycaprolactone polyol, polyethylene glycol adipate, polybutylene glycol adipate; the diisocyanate is selected from at least one of diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate; the Shore hardness of the polyester TPU is 60A to 95A.

3. A hot melt adhesive for bonding thermoplastic elastomers according to claim 1, characterized in that: The polyolefin elastomer is an ethylene-octene copolymer or ethylene-butene copolymer synthesized using a metallocene catalyst, with a density range of 0.857~0.885g / cm³ and a melt index of 0.5~30g / 10min at 190℃ / 2.16kg.

4. The hot melt adhesive for thermoplastic elastomer bonding according to claim 1, characterized by: The free radical initiator is selected from one or a mixture of several of benzoyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, di-tert-butyl peroxide, and benzoyl peroxide.

5. The hot melt adhesive for thermoplastic elastomer bonding according to claim 1, characterized by: The antioxidant is selected from one or a mixture of several of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester, tris[2,4-di-tert-butylphenyl]phosphite, and n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

6. A hot melt adhesive for bonding thermoplastic elastomers according to claim 1, characterized in that: The weight ratio of the polyester thermoplastic polyurethane to the polyolefin elastomer is 50:50 to 70:30, and the gel content of the hot melt adhesive is less than 0.5%, and the T-type peeling strength on a styrene-ethylene-butylene-styrene block copolymer substrate is greater than 40N / 25mm.

7. A process for the preparation of a hot melt adhesive for thermoplastic elastomer bonding, characterized in that: The preparation method for preparing the hot melt adhesive of any one of claims 1~6 comprises: Step one, dry the polyester thermoplastic polyurethane particles and polyolefin elastomer particles at 60℃~80℃ for 3~5 hours to reduce the moisture content to less than 0.05%; dissolve the free radical initiator in the glycidyl methacrylate monomer to prepare a reaction aid liquid; Step two, place the dried polyester thermoplastic polyurethane particles, polyolefin elastomer particles, and antioxidant into the main feeding port of the twin-screw extruder according to the formula ratio; Step three, inject the reaction aid liquid through a liquid metering pump after the melting section of the twin-screw extruder; Step four, control the reaction temperature of the twin-screw extruder to be 170~200℃, the screw rotation speed to be 30~200rpm, and the material residence time to be 2~5 minutes to carry out in-situ grafting and compatibilization reaction; Step five, perform vacuum exhaust at the end of the twin-screw extruder to remove unreacted monomers and volatile components; Step six, perform extrusion drawing, cool in water, and then cut into particles to obtain the hot melt adhesive for thermoplastic elastomer bonding.

8. A process for the preparation of a hot melt adhesive for thermoplastic elastomers according to claim 7, characterized in that: The twin-screw extruder is a parallel co-rotating twin-screw extruder, the length-diameter ratio of which is 40:1 to 48:1, and the temperature setting range is: 60-110 DEG C for the first zone, 160-180 DEG C for the second to third zones, 180-200 DEG C for the fourth to seventh zones, 180-190 DEG C for the eighth to ninth zones, and 170-185 DEG C for the die head.

9. A method for preparing a hot melt adhesive for bonding thermoplastic elastomers according to claim 7, characterized in that: In step four, a cascade chemical reaction occurs: firstly, a primary free radical is generated by thermal decomposition of the free radical initiator; secondly, a macromolecular free radical is formed by the free radical taking hydrogen atoms on the polyolefin elastomer chain; thirdly, glycidyl methacrylate monomers are grafted onto the polyolefin elastomer macromolecular chain to generate polyolefin elastomer grafted glycidyl methacrylate; and finally, ring-opening esterification occurs between the epoxy groups of the polyolefin elastomer grafted glycidyl methacrylate side chain and the carboxyl groups at the end of the polyester thermoplastic polyurethane to generate a block / graft copolymer.

10. Use of a hot melt adhesive, characterized in that: The hot melt adhesive for bonding thermoplastic elastomers according to any one of claims 1-6 is used to bond non-polar thermoplastic elastomer substrates with polar substrates; The polar substrate is at least one of polyester fabric, polycarbonate, acrylonitrile-butadiene-styrene copolymer and polyester thermoplastic polyurethane film, and the failure mode of the adhesive joint after peel strength testing is cohesive failure of the adhesive body.

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