Hot melt adhesive and preparation method thereof

Abstract

The invention provides a hot melt adhesive and a preparation method thereof, and relates to the technical field of adhesives. According to the hot melt adhesive, amorphous polyolefin (APAO) is used as a main body, ethylene-vinyl acetate copolymer (EVA) is added as a compatilizer, and Fischer-Tropsch wax is used as a viscosity modifier. The preparation method comprises the following steps: firstly synthesizing a dopamine functional polymer, and then carrying out melt blending on the dopamine functional polymer, APAO, EVA, tackifying resin and other components so as to stably introduce a catechol group into a hot melt adhesive system. When the hot melt adhesive is bonded with a metal surface, the catechol group can form a firm coordinate bond with metal ions, so that the adhesive force is greatly improved. The product provided by the invention has high adhesive force, excellent flexibility, good compatibility and construction performance, and is suitable for bonding and sealing metal materials.

Description

Technical Field

[0001] This application relates to the field of adhesive technology, and more specifically, to a hot melt adhesive. Background Technology

[0002] Hot melt adhesives, as an environmentally friendly adhesive, exhibit unique advantages in numerous fields. They are solid at room temperature, melt into a liquid upon heating, and rapidly solidify upon cooling after application, making them highly convenient and efficient in operation and application. Among them, hot melt adhesives based on amorphous polyolefins (APAO) have been widely used in packaging, automotive, textile, and other industries due to their excellent performance. APAO hot melt adhesives possess excellent flexibility, allowing them to maintain good adhesion even under certain degrees of bending and stretching, preventing cracking or detachment. Simultaneously, their low-temperature resistance is outstanding, maintaining stable physical and chemical properties even at low temperatures, ensuring reliable bonding. Furthermore, they exhibit good adhesion to various non-polar materials, meeting the bonding needs of different material combinations.

[0003] However, APAO-based hot melt adhesives exhibit significant shortcomings in their bonding performance with polar materials, especially metal surfaces, generally exhibiting poor adhesion. This problem stems from the non-polar molecular structure of APAO, while metal surfaces possess high surface energy, creating a mismatch. This mismatch hinders APAO from achieving good interfacial wetting on metal surfaces, resulting in weak intermolecular forces and ultimately preventing the formation of a stable adhesive interface.

[0004] To improve the adhesion performance of APAO-based hot melt adhesives to metals, several methods have been explored. One common approach is to graft polar monomers onto APAO, introducing polar groups into the APAO molecular chain to alter its molecular structure and enhance its interaction with the metal surface. Another method is to add tackifying resins to the formulation, utilizing the properties of these resins to improve the adhesive's adhesion to metals. However, these methods all have limitations. Polar monomer grafting modification is complex, requiring precise control of reaction conditions such as reaction temperature, time, and monomer dosage; otherwise, achieving the desired modification effect is difficult. Furthermore, modified APAO is prone to aging and embrittlement at high temperatures, leading to a decrease in its flexibility and durability. While adding tackifying resins can improve adhesion to some extent, the tackifying effect is often limited and insufficient for high-strength bonding requirements. More importantly, these methods, while improving adhesion, struggle to simultaneously maintain APAO's inherent excellent flexibility and low-temperature resistance, thus restricting the application of APAO hot melt adhesives.

[0005] Dopamine, a key functional component of mussel adhesive protein, possesses unique adhesive properties. Its catechol groups exhibit extremely strong coordination and covalent bonding abilities with various inorganic and organic surfaces, especially metal surfaces. This powerful adhesive ability makes dopamine a promising candidate for applications in materials bonding, offering a new approach to solving the problem of poor adhesion to metals by APAO-based hot melt adhesives. Inspired by this, researchers have attempted to introduce dopamine or its analogues into adhesive systems to improve the adhesion of adhesives to metals.

[0006] However, in practice, directly physically blending dopamine into hot melt adhesive systems presents numerous problems. Dopamine is prone to migration in hot melt adhesive systems, gradually precipitating out of the adhesive over time, leading to decreased adhesion performance. Simultaneously, its thermal stability is poor, easily decomposing and failing at high temperatures, failing to meet the requirements of some high-temperature applications. Furthermore, dopamine has poor compatibility with the hot melt adhesive matrix, making it difficult to disperse uniformly within the matrix, thus affecting the overall performance of the adhesive. Particularly when dopamine is introduced into the non-polar APAO system, severe phase separation occurs due to the differences in their properties. This phase separation leads to defects within the colloid, such as pores and cracks, which not only significantly limits the adhesive performance of dopamine, preventing effective improvement in adhesion to metals, but also severely damages the mechanical properties of the adhesive layer, such as reducing its strength and toughness, and affecting its durability, thus shortening its service life.

[0007] In summary, it is necessary to provide a hot melt adhesive and its preparation method to better solve the above-mentioned technical problems. Summary of the Invention

[0008] The purpose of this application is to provide a hot melt adhesive and its preparation method, which can solve the technical problem that APAO-type hot melt adhesives generally have poor adhesion to polar materials, especially metal surfaces.

[0009] This application provides a hot melt adhesive comprising the following components in parts by weight:

[0010] 40-60 parts of amorphous polyolefin (APAO);

[0011] 3-10 parts of ethylene-vinyl acetate copolymer (EVA);

[0012] 20-40 parts of dopamine-functionalized polymer;

[0013] 10-25 parts of tackifying resin;

[0014] Fischer-Tropsch wax 5-15 parts;

[0015] Antioxidant 0.1-1 part;

[0016] 0.5-2 parts of coupling agent.

[0017] Furthermore, the vinyl acetate (VA) content of the ethylene-vinyl acetate copolymer (EVA) is 18-33%, and the melt index (MI, 190℃ / 2.16kg) is 10-50g / 10min, which facilitates rapid melting and blending with other components at the processing temperature. In the system, it acts as a compatibilizer, effectively bridging the APAO phase and the dopamine-functionalized polymer phase through the compatibility of the ethylene segment in the molecular chain with APAO and the compatibility of the vinyl acetate segment with the polar segment of the dopamine-functionalized polymer, thereby improving phase separation.

[0018] Furthermore, the dopamine-functionalized polymer is a polymer with a catechol-terminated chain, generated by reacting a terminal isocyanate-based prepolymer with dopamine; wherein the terminal isocyanate-based prepolymer is prepared by reacting a polymeric polyol with an excess of diisocyanate. Specifically, the primary amine group in the dopamine molecule preferentially reacts with the terminal isocyanate group of the prepolymer, thereby introducing the dopamine structure in the form of terminal groups and ensuring that its catechol structure is completely preserved.

[0019] Further, the polymer polyol is a polyether polyol (such as PPG, PTMEG) or a polyester polyol with a molecular weight of 400-2000; the diisocyanate is any of 4,4'-diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI).

[0020] Furthermore, the tackifying resin is any of several selected from hydrogenated rosin glycerol ester, C5 petroleum resin, C9 petroleum resin, and terpene resin.

[0021] Furthermore, the Fischer-Tropsch wax has a melting point of 70-105°C, which is used to reduce the melt viscosity of hot melt adhesives, improve application fluidity and wettability, and adjust the balance between open time and curing speed.

[0022] Furthermore, the antioxidant is a hindered phenolic antioxidant (such as antioxidant 1010) or a phosphite antioxidant (such as antioxidant 168).

[0023] Furthermore, the coupling agent is a silane coupling agent, such as γ-aminopropyltriethoxysilane (KH-550) or γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560).

[0024] Specifically, the polymer chain of the hot melt adhesive has segments with catechol end groups. When the hot melt adhesive comes into contact with the metal surface, the catechol groups of these segments can form stable chelates or coordination bonds with metal ions, thereby greatly enhancing the interfacial adhesion between the adhesive layer and the metal substrate.

[0025] Based on the same inventive concept, this application also provides a method for preparing the above-mentioned hot melt adhesive, comprising the following steps:

[0026] S1. Preparation of dopamine functionalized polymers

[0027] Under a dry, inert atmosphere, a measured amount of diisocyanate is dissolved in an anhydrous solvent. Under vigorous stirring, a measured amount of polymeric polyol is slowly added to the system, controlling the reaction temperature to not exceed 60°C. The molar ratio of the hydroxyl groups of the polymeric polyol to the isocyanate groups (-NCO) of the diisocyanate is 1: (1.1 ~ 1.3), ensuring that the diisocyanate is in excess. The reaction produces a prepolymer with -NCO end groups.

[0028] Subsequently, the system was cooled to 0-5°C in an ice-water bath. Under continuous vigorous stirring, dopamine dissolved in anhydrous solvent was slowly added dropwise to the prepolymer system. The dropping rate was controlled so that the reaction temperature did not exceed 10°C. After the addition was completed, the temperature was raised to room temperature and the reaction continued for 2-4 hours. The intensity of the -NCO characteristic absorption peak of the system was monitored by Fourier transform infrared spectroscopy (FTIR) until it no longer changed significantly, indicating that the reaction was basically completed and a dopamine functionalized polymer solution was obtained.

[0029] Finally, the solvent was separated and recovered by vacuum distillation to obtain a viscous dopamine-functionalized polymer, which was then sealed for later use.

[0030] S2. Synthesis and Mixing of Main Rubber Compound

[0031] Add APAO, EVA, tackifying resin, Fischer-Tropsch wax and antioxidant to the reactor, heat to 120-140℃, and stir for 1-2 hours to mix evenly.

[0032] Add the dopamine-functionalized polymer prepared in step S1, add the coupling agent and stir rapidly, then continue stirring for 0.5-1 hour.

[0033] S3. Discharge and Forming

[0034] The above-mentioned adhesive solution is transferred to an underwater pelletizer for granulation and cooling while it is still hot to obtain the hot melt adhesive.

[0035] The beneficial effects of this invention are:

[0036] The hot melt adhesive provided by this invention uses a dopamine-terminated polymer containing a catechol structure to blend into an APAO matrix, effectively preventing the physical migration and thermal decomposition of dopamine and ensuring the long-term stability of product performance. By adding EVA with a specific VA content as a compatibilizer, the compatibility between APAO and non-polar polyolefins and dopamine-functionalized polyurethane is effectively improved, reducing phase separation and resulting in a more uniform distribution of dopamine functionalized segments in the colloid, avoiding performance inconsistencies and interfacial defects caused by phase separation. The presence of catechol groups intact at the ends of the polymer chains allows the hot melt adhesive to form strong, multidentate complexes with metal surface oxides during bonding, generating interfacial interactions far exceeding van der Waals forces. This significantly improves adhesion to metals such as stainless steel, aluminum, and copper. The addition of Fischer-Tropsch wax significantly reduces the melt viscosity of the hot melt adhesive, improving its fluidity and wetting ability on the adhered surfaces. Simultaneously, it precisely controls the balance between open time and curing speed, ensuring that the product achieves high adhesion while maintaining excellent flexibility, impact resistance, and workability.

[0037] The preparation method provided by this invention has a simple process flow, good process compatibility, and is compatible with traditional hot melt adhesive production processes. It requires no special equipment and is easy to realize industrial production. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a flowchart illustrating the preparation process in an embodiment of the present invention. Detailed Implementation

[0040] To facilitate understanding of the present invention, it will be described more fully below through embodiments, and preferred embodiments are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Any other implementation schemes obtained by modifying or equivalently substituting the technical solutions of the present invention without inventive step are all within the protection scope of the present invention.

[0041] 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. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0042] The numerical values ​​disclosed in the embodiments of this invention are approximate values, not definitive values. Where error or experimental conditions permit, all values ​​within the error range may be included, and the specific numerical values ​​disclosed in the embodiments of this invention are not limited to those specified.

[0043] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0044] It should be noted that there are multiple grades of APAO in the hot melt adhesive components of this application. This application does not limit the specific grade of APAO. The specific APAO grades exemplified in the following specific embodiments are for illustrative purposes only and do not limit the range of APAO options in this application.

[0045] The following are specific examples.

[0046] Example 1

[0047] This embodiment provides a method for preparing hot melt adhesive, including the following preparation steps:

[0048] S1. Preparation of dopamine-functionalized polymers:

[0049] Under nitrogen protection, 5.3 g (0.024 mol) of isophorone diisocyanate (IPDI) was dissolved in 60 mL of anhydrous tetrahydrofuran. Under vigorous stirring, 20.0 g (0.02 mol) of polypropylene glycol (PPG, Mn=1000) was slowly added to the system, and the reaction temperature was controlled not to exceed 60 °C. The reaction was carried out for 2 hours to generate terminal-NCO prepolymer.

[0050] Subsequently, the system was cooled to 0-5°C in an ice-water bath. Under continuous vigorous stirring, 0.76 g (0.004 mol) of dopamine hydrochloride was dissolved in 40 mL of anhydrous DMF containing 0.4 g (0.004 mol) of triethylamine and neutralized. The dropping rate was controlled so that the reaction temperature did not exceed 10°C.

[0051] After the addition was complete, the temperature was raised to room temperature and the reaction continued for 2 hours. Fourier transform infrared spectroscopy (FTIR) was used to monitor that the intensity of the characteristic absorption peak of -NCO in the system no longer changed significantly, indicating that the reaction was basically completed and a dopamine functionalized polymer solution was obtained.

[0052] Finally, the solvent was separated to obtain a brownish-brown viscous dopamine-functionalized polymer, which was then sealed for later use.

[0053] S2. Preparation of hot melt adhesive:

[0054] 45 parts of APAO (brand name: REXtac RT 2585), 5 parts of EVA (VA content 28%, MI=25 g / 10min), 20 parts of hydrogenated rosin glycerol ester, 8 parts of Fischer-Tropsch wax (melting point 95℃), and 0.5 parts of antioxidant 1010 were added to a reaction vessel, heated to 130℃, and stirred for 1.5 hours to mix evenly. Then, 35 parts of the dopamine functionalized polymer with catechol-terminated chains prepared by the aforementioned method and 0.5 parts of silane coupling agent KH-550 were added, and the mixture was stirred rapidly for another 0.5 hours.

[0055] S3. Discharge and Forming:

[0056] The above-mentioned adhesive solution is transferred to an underwater pelletizer for granulation and cooling while it is still hot to obtain the flexible hot melt adhesive product.

[0057] Example 2

[0058] This embodiment provides a method for preparing hot melt adhesive, including the following preparation steps:

[0059] S1. Preparation of dopamine-functionalized polymers:

[0060] This step is the same as in Example 1, except that: 5.8g (0.026 mol) of IPDI is used to react with 16.0g (0.02 mol) of polyethylene glycol (PEG, Mn=800), the molar ratio of hydroxyl to -NCO is 1:1.3, the amount of dopamine is adjusted to 1.13g (0.006 mol), and the amount of triethylamine is 0.6g (0.006 mol).

[0061] S2. Preparation of hot melt adhesive:

[0062] Add 50 parts APAO, 5 parts EVA (VA content 18%, MI=15 g / 10min), 15 parts hydrogenated C5 petroleum resin, 10 parts Fischer-Tropsch wax (melting point 85℃), and 0.3 parts antioxidant 168 to a reactor, heat to 135℃, and stir for 1 hour to mix evenly. Add 25 parts of the dopamine functionalized polymer with catechol-terminated chain ends prepared by the aforementioned method and 0.3 parts silane coupling agent KH-560, stir rapidly, and continue stirring for 1 hour.

[0063] S3. Discharge and Forming:

[0064] The resulting adhesive solution is transferred to an underwater pelletizer for granulation and cooling to obtain the product.

[0065] Example 3

[0066] This embodiment provides a method for preparing hot melt adhesive, including the following preparation steps:

[0067] S1. Preparation of dopamine-functionalized polymers:

[0068] This step is the same as in Example 1, except that: 6.0 g (0.024 mol) of diphenylmethane diisocyanate (MDI) is used to react with 20.0 g (0.02 mol) of PPG (Mn=1000), the molar ratio of hydroxyl to -NCO is 1:1.2, and the amount of dopamine used is the same as in Example 1.

[0069] S2. Preparation of hot melt adhesive:

[0070] 40 parts APAO, 8 parts EVA (VA content 33%, MI=40 g / 10min), 25 parts terpene resin, 12 parts Fischer-Tropsch wax (melting point 105℃), and 0.8 parts antioxidant 1076 were added to a reactor and heated to 125℃. The mixture was stirred for 2 hours until homogeneous. Then, 35 parts of the dopamine functionalized polymer with catechol-terminated chains prepared by the aforementioned method and 0.5 parts of silane coupling agent KH-550 were added, and the mixture was stirred rapidly for another 0.5 hours.

[0071] S3. Discharge and Forming:

[0072] The resulting adhesive solution is transferred to an underwater pelletizer for granulation and cooling to obtain the product.

[0073] Comparative Example 1

[0074] This comparative example provides a method for preparing a hot melt adhesive, the preparation steps of which are as follows:

[0075] 75 parts APAO, 5 parts EVA (VA content 28%), 25 parts hydrogenated rosin glycerol ester, 8 parts Fischer-Tropsch wax (melting point 95℃), and 0.5 parts antioxidant 1010 were added to a reactor and heated to 130℃. The mixture was stirred for 1.5 hours until homogeneous. Then, 1 part silane coupling agent KH-550 was added, and the mixture was stirred rapidly for another 0.5 hours. Granulation and cooling were performed to obtain the product.

[0076] Comparative Example 2

[0077] This comparative example provides a method for preparing a hot melt adhesive, the preparation steps of which are as follows:

[0078] Add 60 parts APAO, 5 parts EVA (VA content 28%), 20 parts hydrogenated rosin glycerol ester, 8 parts Fischer-Tropsch wax (melting point 95℃), and 0.5 parts antioxidant 1010 to a reaction vessel, heat to 130℃, and stir for 1.5 hours to mix evenly. Directly add 2.0 parts dopamine powder and 1 part silane coupling agent KH-550, stir rapidly, continue stirring for 0.5 hours, granulate, and cool to obtain the product.

[0079] Comparative Example 3

[0080] This comparative example provides a method for preparing a hot melt adhesive, the preparation steps of which are as follows:

[0081] Preparation of dopamine-functionalized polymers:

[0082] Under nitrogen protection, 4.44 g (0.02 mol) of isophorone diisocyanate (IPDI) was dissolved in 60 mL of anhydrous tetrahydrofuran. Under vigorous stirring, 20.0 g (0.02 mol) of polypropylene glycol (PPG, Mn=1000) was slowly added to the system, controlling the reaction temperature to not exceed 60 °C, and the reaction was carried out for 2 hours. Finally, the solvent was separated to obtain the polyurethane polymer, which was then sealed for later use.

[0083] Preparation of hot melt adhesive:

[0084] Add 45 parts APAO (brand name: REXtac RT 2585), 5 parts EVA (VA content 28%, MI=25 g / 10min), 20 parts hydrogenated rosin glycerol ester, 8 parts Fischer-Tropsch wax (melting point 95℃), and 0.5 parts antioxidant 1010 to a reaction vessel, heat to 130℃, and stir for 1.5 hours to mix evenly. Add 35 parts of the polyurethane prepared in step 1 and 0.5 parts of silane coupling agent KH-550, stir rapidly, and continue stirring for 0.5 hours.

[0085] The above-mentioned adhesive solution is transferred to an underwater pelletizer for pelletizing and cooling while it is still hot to obtain the hot melt adhesive product.

[0086] Performance testing

[0087] The hot melt adhesive granules prepared in Examples 1-3 and Comparative Examples 1-3 were melted on a melt coating machine at 180°C, coated onto standard stainless steel test pieces, and then cooled and cured after bonding. The 180° peel strength (for stainless steel) was tested according to GB / T 2791-1995 standard, and the test results are shown in the table below:

[0088] sample 180° peel strength (N / cm) Flexibility observation Example 1 19.4 Excellent, the adhesive layer is soft and does not break easily. Example 2 22.3 Excellent, the adhesive layer is soft and does not break easily. Example 3 17.5 Excellent, the adhesive layer is soft and does not break easily. Comparative Example 1 3.6 Poor quality, interface is easily peeled off. Comparative Example 2 4.7 Good; the colloid has a slightly rough feel, and the interface is easy to peel off. Comparative Example 3 8.5 Good, easy to peel off the interface

[0089] Test results show that the hot melt adhesive containing a chemically bonded dopamine structure prepared in this invention has a peel strength to metal that is several times higher than that of the traditional APAO hot melt adhesive (Comparative Example 1). More importantly, compared with Comparative Example 3, which only added ordinary polyurethane, the peel strength of the embodiment of this invention is also about twice as high. This strongly demonstrates the key role of the terminal catechol group in improving metal adhesion.

[0090] In summary, the hot melt adhesive provided by this invention is based on amorphous polyolefin (APAO), with ethylene-vinyl acetate copolymer (EVA) added as a compatibilizer and Fischer-Tropsch wax as a viscosity modifier. First, a dopamine-functionalized polymer is synthesized, and then it is melt-blended with APAO, EVA, tackifying resin, and other components to stably introduce catechol groups into the hot melt adhesive system. When this hot melt adhesive bonds to a metal surface, the catechol groups can form strong coordination bonds with metal ions, greatly improving adhesion. The product of this invention possesses high adhesion, excellent flexibility, good compatibility, and good workability, making it suitable for bonding and sealing metal materials.

[0091] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A hot melt adhesive, characterized in that, The components include the following parts by mass: 40-60 parts of amorphous polyolefin; 3-10 parts of ethylene-vinyl acetate copolymer; 20-40 parts of dopamine-functionalized polymer; 10-25 parts of tackifying resin; Fischer-Tropsch wax 5-15 parts; Antioxidant 0.1-1 part; 0.5-2 parts of coupling agent.

2. The hot melt adhesive according to claim 1, characterized in that, The ethylene-vinyl acetate copolymer has a vinyl acetate content of 18-33% and a melt index of 10-50 g / 10 min.

3. The hot melt adhesive according to claim 1, characterized in that, The dopamine-functionalized polymer is a polymer with catechol-terminated chains generated by reacting a terminal isocyanate prepolymer with dopamine; wherein the terminal isocyanate prepolymer is prepared by reacting a polymer polyol with an excess of diisocyanate.

4. The hot melt adhesive according to claim 3, characterized in that, The polymer polyol is a polyether polyol or a polyester polyol with a molecular weight of 400-2000; the diisocyanate is any of 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate.

5. The hot melt adhesive according to claim 1, characterized in that, The tackifying resin is any of several of hydrogenated rosin glycerol ester, C5 petroleum resin, C9 petroleum resin, and terpene resin.

6. The hot melt adhesive according to claim 1, characterized in that, The melting point of the Fischer-Tropsch wax is 70-105℃.

7. The hot melt adhesive according to claim 1, characterized in that, The antioxidants mentioned are hindered phenolic antioxidants or phosphite antioxidants.

8. The hot melt adhesive according to claim 1, characterized in that, The coupling agent is a silane coupling agent, such as γ-aminopropyltriethoxysilane or γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

9. A method for preparing a hot melt adhesive as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Preparation of dopamine functionalized polymers Under a dry, inert atmosphere, a measured amount of diisocyanate is dissolved in an anhydrous solvent. Under vigorous stirring, a measured amount of polymeric polyol is slowly added to the system, controlling the reaction temperature to not exceed 60°C. The molar ratio of the hydroxyl groups of the polymeric polyol to the isocyanate groups of the diisocyanate is 1:(1.1~1.3), ensuring that the diisocyanate is in excess. The reaction produces a prepolymer with -NCO end groups. Subsequently, the system was cooled to 0-5°C in an ice-water bath. Under continuous vigorous stirring, dopamine dissolved in anhydrous solvent was slowly added dropwise to the prepolymer system. The dropping rate was controlled so that the reaction temperature did not exceed 10°C. After the addition was completed, the temperature was raised to room temperature and the reaction continued for 2-4 hours. The intensity of the characteristic absorption peak of -NCO in the system was monitored by Fourier transform infrared spectroscopy until it no longer changed significantly, indicating that the reaction was basically completed and a dopamine functionalized polymer solution was obtained. Finally, the solvent was separated and recovered by vacuum distillation to obtain a viscous dopamine-functionalized polymer, which was then sealed for later use. S2. Synthesis and Mixing of Main Rubber Compound Amorphous polyolefin, ethylene-vinyl acetate copolymer, tackifying resin, Fischer-Tropsch wax and antioxidant are added to a reaction vessel, heated to 120-140℃, and stirred for 1-2 hours to mix evenly. Add the dopamine-functionalized polymer prepared in step S1, add the coupling agent and stir rapidly, then continue stirring for 0.5-1 hour; S3. Discharge and Forming The above-mentioned adhesive solution is transferred to an underwater pelletizer for granulation and cooling while it is still hot to obtain the hot melt adhesive.

Images