Hot-melt pressure sensitive adhesive, and preparation method and application thereof

Abstract

The present application relates to the technical field of adhesive, and discloses a hot melt pressure sensitive adhesive and a preparation method and application thereof.The hot melt pressure sensitive adhesive comprises the following components in percentage by mass: base adhesive 80wt%-95wt%, lipoic acid 3wt%-15wt%, and polyvinylpyrrolidone 1wt%-7wt%.The present application successfully overcomes the technical problem of bonding failure of traditional hot melt pressure sensitive adhesive in underwater environment by introducing a complex formed by lipoic acid and polyvinylpyrrolidone, the complex can effectively absorb the water film on the surface of the base material, significantly enhance the wetting ability of the adhesive to the wet interface, and greatly improve the cohesive strength and interfacial bonding force of the colloid through the synergistic effect with the SIS base adhesive.The 180° peeling strength of the hot melt pressure sensitive adhesive after 24h of underwater immersion can reach 53.58N / inch at the highest, which is much better than the existing solvent type, reaction type and supramolecular underwater adhesives, and there is no shedding phenomenon, and the shear strength (≥70N) in the simulated seawater environment can still remain excellent, showing good environmental tolerance.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to a hot melt pressure-sensitive adhesive, its preparation method, and its application. Background Technology

[0002] Hot melt pressure-sensitive adhesives (HPIs) possess significant advantages such as being solvent-free, having a fast application speed, high production efficiency, and simplified processes. They are widely used in dry environments such as packaging, labeling, medical dressings, and industrial assembly, becoming an indispensable category in the adhesive field. However, when used directly in humid environments or underwater, the adhesive performance of traditional HPIs significantly deteriorates, sometimes even failing to achieve effective bonding, greatly limiting their application scenarios. The core reason for this is that under humid or underwater conditions, a continuous or semi-continuous water film easily forms on the surface of the substrate. This water film directly blocks the adhesive from fully wetting and effectively contacting the substrate surface, inhibiting the establishment of intermolecular forces, ultimately leading to a significant reduction in interfacial adhesion and causing bonding failure.

[0003] To meet the practical needs of underwater or wet bonding, existing technologies have proposed a variety of solutions. For example, traditional adhesives such as epoxy resin, polyurethane, and ethyl cyanoacrylate can achieve underwater bonding under specific conditions; some technologies enhance the wettability of the adhesive on wet surfaces by introducing hydrophilic groups into the adhesive molecule structure; other solutions improve adhesive adhesion by pre-coating drainage or interface-activating primers; and biomimetic supramolecular adhesives based on dopamine and catechol structures also exhibit good underwater adhesion potential due to their special molecular interactions.

[0004] However, some of the aforementioned materials have high raw material costs, and others have low peel strength and cohesive strength, failing to meet the requirements of high-load bonding. More importantly, most systems are difficult to adapt to the melt processing and rapid application processes of hot-melt pressure-sensitive adhesives, and are incompatible with existing industrial production processes. In addition, some underwater adhesives have cumbersome application steps, long curing cycles, insufficient durability and environmental tolerance, and significant performance fluctuations in different aquatic environments such as freshwater and seawater.

[0005] Therefore, there is an urgent need to develop an adhesive system that can fully retain the inherent advantages of hot melt pressure-sensitive adhesives, while achieving rapid, stable, and durable pressure-sensitive bonding in humid, underwater, and even seawater environments, thereby promoting the expansion of hot melt pressure-sensitive adhesives into underwater and wet surface applications. Summary of the Invention

[0006] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one objective of the present invention is to provide a hot melt pressure-sensitive adhesive.

[0007] The second objective of this invention is to provide a method for preparing this hot melt pressure-sensitive adhesive.

[0008] The third objective of this invention is to provide applications for this hot melt pressure-sensitive adhesive.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a hot melt pressure-sensitive adhesive comprising, by weight percentage: 80wt%-95wt% base adhesive, 3wt%-15wt% thioctic acid, and 1wt%-7wt% polyvinylpyrrolidone.

[0010] In some embodiments of the present invention, the hot melt pressure-sensitive adhesive comprises the following components by weight percentage: base adhesive 80wt%-95wt%, thioctic acid 3wt%-13.5wt%, and polyvinylpyrrolidone 1.5wt%-7wt%.

[0011] In some embodiments of the present invention, the mass ratio of thioctic acid to polyvinylpyrrolidone in the hot melt pressure-sensitive adhesive is (1-8):1.

[0012] In some preferred embodiments of the present invention, the mass ratio of thioctic acid to polyvinylpyrrolidone in the hot melt pressure-sensitive adhesive is (1-2):1.

[0013] In some embodiments of the present invention, the base adhesive comprises the following components: 22-34 parts of SIS block copolymer, 37-56 parts of hydrogenated petroleum resin, 20-30 parts of naphthenic oil, and 0.1-0.5 parts of antioxidant.

[0014] In some preferred embodiments of the present invention, the base adhesive comprises the following components: 25-31 parts of SIS block copolymer, 42-51 parts of hydrogenated petroleum resin, 22-27 parts of naphthenic oil, and 0.3-0.5 parts of antioxidant.

[0015] In some embodiments of the present invention, the SIS block copolymer is linear, with a styrene content of 25.0±2.0% and a diblock content of 25.0±2.0%.

[0016] In some embodiments of the present invention, the antioxidant is selected from hindered phenolic antioxidants, phosphite antioxidants, or combinations thereof.

[0017] In some embodiments of the present invention, the base adhesive is prepared by a method comprising the following steps: mixing naphthenic oil, SIS block copolymer and antioxidant, stirring continuously under heating conditions until the system is completely melted and free of particulate raw materials; adding hydrogenated petroleum resin, continuing to stir at a constant temperature, and performing vacuum degassing on the mixed system to obtain the base adhesive.

[0018] In some embodiments of the present invention, the base adhesive is prepared using a kneader.

[0019] In some embodiments of the present invention, the base adhesive is prepared at a heating temperature of 140-160°C.

[0020] In some preferred embodiments of the present invention, the base adhesive is prepared at a heating temperature of 145-155°C.

[0021] In some embodiments of the present invention, the time for continuing constant temperature stirring after obtaining the base adhesive is 0.5-1.5 h.

[0022] In some preferred embodiments of the present invention, the time for continuing constant temperature stirring after obtaining the base adhesive is 0.8-1.2 h.

[0023] A second aspect of the present invention provides a method for preparing the hot melt pressure-sensitive adhesive described in the first aspect of the present invention, comprising the following steps: S1. Mix thioctic acid and polyvinylpyrrolidone and heat to react to obtain polythioctic acid-polyvinylpyrrolidone complex; S2. After heating and melting the base adhesive, add the polythioctic acid-polyvinylpyrrolidone compound and mix well. Degas under vacuum to obtain the hot melt pressure-sensitive adhesive.

[0024] In some embodiments of the present invention, the hot melt pressure-sensitive adhesive is prepared using a kneader.

[0025] In some embodiments of the present invention, in step S1, the heating reaction temperature is 120-140°C and the time is 0.5-1.5h.

[0026] In some preferred embodiments of the present invention, in step S1, the heating reaction temperature is 125-135°C and the time is 0.8-1.2h.

[0027] In some embodiments of the present invention, in step S2, the temperature of heating and melting is 120-140°C.

[0028] In some preferred embodiments of the present invention, in step S2, the heating and melting temperature is 125-135°C.

[0029] In some embodiments of the present invention, in step S2, the mixing time is 20-40 min.

[0030] In some preferred embodiments of the present invention, in step S2, the mixing time is 25-35 min.

[0031] The third aspect of the present invention provides the application of the hot melt pressure-sensitive adhesive described in the first aspect of the present invention in bonding on wet surfaces or in underwater environments.

[0032] In some embodiments of the present invention, the underwater environment includes a freshwater environment and a seawater environment.

[0033] Compared with the prior art, the beneficial effects of the present invention are: The hot-melt pressure-sensitive adhesive provided by this invention successfully overcomes the technical challenge of adhesion failure in underwater environments of traditional hot-melt pressure-sensitive adhesives by introducing a compound formed from thioctic acid and polyvinylpyrrolidone. This compound can effectively absorb the water film on the substrate surface, significantly enhancing the adhesive's wetting ability at wet interfaces. Simultaneously, through synergistic effects with SIS-based adhesives, it greatly improves the cohesive strength and interfacial bonding of the adhesive. Experimental data shows that the hot-melt pressure-sensitive adhesive of this invention achieves a maximum 180° peel strength of 53.58 N / inch after 24 hours of underwater immersion, far superior to existing solvent-based, reactive, and supramolecular underwater adhesives, with no detachment. Furthermore, this invention maintains excellent shear strength (≥70 N) in simulated seawater environments, demonstrating good environmental tolerance. This adhesive fully retains the advantages of traditional hot-melt pressure-sensitive adhesives: solvent-free, melt-processable, and rapid application. The preparation process only involves melt blending, making it simple to operate, cost-effective, and suitable for large-scale industrial production. Attached Figure Description

[0034] Figure 1 DSC curves of thioctic acid crystals after 3 months of storage; Figure 2 The DSC curves of the base adhesive and hot melt pressure-sensitive adhesive in Example 1 after 3 months of storage are shown. Detailed Implementation

[0035] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0036] Note: The SIS block copolymers used in the following examples and comparative examples are 1220 linear SIS block copolymers with a styrene content of 25.0±2.0% and a diblock content of 25.0±2.0%; purchased from Shandong Jusheng Technology Co., Ltd. 2. The hydrogenated petroleum resin is a hydrogenated dcpd resin; its softening point is 100℃. 3. The naphthenic oil is 4010 naphthenic oil; its kinematic viscosity at 40℃ is approximately 330 cSt. 4. The antioxidant is pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1010).

[0037] Example 1 This embodiment prepares a hot melt pressure-sensitive adhesive, the components and contents of which are shown in Table 1: Table 1. Components and content of the hot melt pressure-sensitive adhesive in Example 1

[0038] The preparation steps are as follows: S11. Mix thioctic acid and polyvinylpyrrolidone, heat to 130°C, stir at constant temperature for 1 hour to allow the two to react fully, and cool after the reaction to obtain polythioctic acid-polyvinylpyrrolidone complex. S21. Add naphthenic oil, SIS block copolymer and antioxidant to kneader, heat to 150°C, stir until there are no granular raw materials, add hydrogenated petroleum resin, continue to stir at constant temperature for 1 hour, remove air bubbles by vacuuming, discharge, cool to room temperature to obtain base rubber. S22. Add the base adhesive to the kneader, heat to 130℃, and stir to melt; add the polythioctic acid-polyvinylpyrrolidone compound, stir evenly for 30 minutes, then vacuum to remove air bubbles, discharge the material, and cool to room temperature to obtain the hot melt pressure-sensitive adhesive.

[0039] Example 2 This embodiment prepares a hot melt pressure-sensitive adhesive, the components and contents of which are shown in Table 2: Table 2. Components and content of the hot melt pressure-sensitive adhesive in Example 2

[0040] The preparation steps are as follows: S11. Mix thioctic acid and polyvinylpyrrolidone, heat to 130°C, stir at constant temperature for 1 hour to allow the two to react fully, and cool after the reaction to obtain polythioctic acid-polyvinylpyrrolidone complex. S21. Add naphthenic oil, SIS block copolymer and antioxidant to kneader, heat to 150°C, stir until there are no granular raw materials, add hydrogenated petroleum resin, continue to stir at constant temperature for 1 hour, remove air bubbles by vacuuming, discharge, cool to room temperature to obtain base rubber. S22. Add the base adhesive to the kneader, heat to 130℃, and stir to melt; add the polythioctic acid-polyvinylpyrrolidone compound, stir evenly for 30 minutes, then vacuum to remove air bubbles, discharge the material, and cool to room temperature to obtain the hot melt pressure-sensitive adhesive.

[0041] Example 3 This embodiment prepares a hot melt pressure-sensitive adhesive, the components and contents of which are shown in Table 3: Table 3. Components and content of the hot melt pressure-sensitive adhesive in Example 3

[0042] The preparation steps are as follows: S11. Mix thioctic acid and polyvinylpyrrolidone, heat to 130°C, stir at constant temperature for 1 hour to allow the two to react fully, and cool after the reaction to obtain polythioctic acid-polyvinylpyrrolidone complex. S21. Add naphthenic oil, SIS block copolymer and antioxidant to kneader, heat to 150°C, stir until there are no granular raw materials, add hydrogenated petroleum resin, continue to stir at constant temperature for 1 hour, remove air bubbles by vacuuming, discharge, cool to room temperature to obtain base rubber. S22. Add the base adhesive to the kneader, heat to 130℃, and stir to melt; add the polythioctic acid-polyvinylpyrrolidone compound, stir evenly for 30 minutes, then vacuum to remove air bubbles, discharge the material, and cool to room temperature to obtain the hot melt pressure-sensitive adhesive.

[0043] Example 4 This embodiment prepares a hot melt pressure-sensitive adhesive, the components and contents of which are shown in Table 4: Table 4. Components and content of the hot melt pressure-sensitive adhesive in Example 4

[0044] The preparation steps are as follows: S11. Mix thioctic acid and polyvinylpyrrolidone, heat to 130°C, stir at constant temperature for 1 hour to allow the two to react fully, and cool after the reaction to obtain polythioctic acid-polyvinylpyrrolidone complex. S21. Add naphthenic oil, SIS block copolymer and antioxidant to kneader, heat to 150°C, stir until there are no granular raw materials, add hydrogenated petroleum resin, continue to stir at constant temperature for 1 hour, remove air bubbles by vacuuming, discharge, cool to room temperature to obtain base rubber. S22. Add the base adhesive to the kneader, heat to 130℃, and stir to melt; add the polythioctic acid-polyvinylpyrrolidone compound, stir evenly for 30 minutes, then vacuum to remove air bubbles, discharge the material, and cool to room temperature to obtain the hot melt pressure-sensitive adhesive.

[0045] Example 5 This embodiment prepares a hot melt pressure-sensitive adhesive, the components and contents of which are shown in Table 5: Table 5. Components and content of the hot melt pressure-sensitive adhesive in Example 5

[0046] The preparation steps are as follows: S11. Mix thioctic acid and polyvinylpyrrolidone, heat to 130°C, stir at constant temperature for 1 hour to allow the two to react fully, and cool after the reaction to obtain polythioctic acid-polyvinylpyrrolidone complex. S21. Add naphthenic oil, SIS block copolymer and antioxidant to kneader, heat to 150°C, stir until there are no granular raw materials, add hydrogenated petroleum resin, continue to stir at constant temperature for 1 hour, remove air bubbles by vacuuming, discharge, cool to room temperature to obtain base rubber. S22. Add the base adhesive to the kneader, heat to 130℃, and stir to melt; add the polythioctic acid-polyvinylpyrrolidone compound, stir evenly for 30 minutes, then vacuum to remove air bubbles, discharge the material, and cool to room temperature to obtain the hot melt pressure-sensitive adhesive.

[0047] Example 6 This embodiment prepares a hot melt pressure-sensitive adhesive, the components and contents of which are shown in Table 6: Table 6. Components and content of the hot melt pressure-sensitive adhesive in Example 6

[0048] The preparation steps are as follows: S11. Mix thioctic acid and polyvinylpyrrolidone, heat to 130°C, stir at constant temperature for 1 hour to allow the two to react fully, and cool after the reaction to obtain polythioctic acid-polyvinylpyrrolidone complex. S21. Add naphthenic oil, SIS block copolymer and antioxidant to kneader, heat to 150°C, stir until there are no granular raw materials, add hydrogenated petroleum resin, continue to stir at constant temperature for 1 hour, remove air bubbles by vacuuming, discharge, cool to room temperature to obtain base rubber. S22. Add the base adhesive to the kneader, heat to 130℃, and stir to melt; add the polythioctic acid-polyvinylpyrrolidone compound, stir evenly for 30 minutes, then vacuum to remove air bubbles, discharge the material, and cool to room temperature to obtain the hot melt pressure-sensitive adhesive.

[0049] Example 7 This embodiment prepares a hot melt pressure-sensitive adhesive, the components and contents of which are shown in Table 7: Table 7. Components and content of the hot melt pressure-sensitive adhesive in Example 7

[0050] The preparation steps are as follows: S11. Mix thioctic acid and polyvinylpyrrolidone, heat to 130°C, stir at constant temperature for 1 hour to allow the two to react fully, and cool after the reaction to obtain polythioctic acid-polyvinylpyrrolidone complex. S21. Add naphthenic oil, SIS block copolymer and antioxidant to kneader, heat to 150°C, stir until there are no granular raw materials, add hydrogenated petroleum resin, continue to stir at constant temperature for 1 hour, remove air bubbles by vacuuming, discharge, cool to room temperature to obtain base rubber. S22. Add the base adhesive to the kneader, heat to 130℃, and stir to melt; add the polythioctic acid-polyvinylpyrrolidone compound, stir evenly for 30 minutes, then vacuum to remove air bubbles, discharge the material, and cool to room temperature to obtain the hot melt pressure-sensitive adhesive.

[0051] Comparative Example 1 A hot melt pressure-sensitive adhesive was prepared in this comparative example. The components and contents are shown in Table 8. Table 8. Components and content of hot melt pressure-sensitive adhesive in Comparative Example 1

[0052] The preparation steps are as follows: S21. Add naphthenic oil, SIS block copolymer and antioxidant to kneader, heat to 150°C, stir until there are no granular raw materials, add hydrogenated petroleum resin, continue to stir at constant temperature for 1 hour, remove air bubbles by vacuuming, discharge, cool to room temperature to obtain base rubber. S22. Add the base adhesive to the kneader, heat to 130℃, and stir to melt; add polyvinylpyrrolidone, stir evenly for 30 minutes, then remove air bubbles by vacuuming, discharge the material, and cool to room temperature to obtain hot melt pressure-sensitive adhesive.

[0053] Comparative Example 2 A hot melt pressure-sensitive adhesive was prepared in this comparative example. The components and contents are shown in Table 9. Table 9. Components and content of hot melt pressure-sensitive adhesive in Comparative Example 2

[0054] The preparation steps are as follows: S21. Add naphthenic oil, SIS block copolymer and antioxidant to kneader, heat to 150°C, stir until there are no granular raw materials, add hydrogenated petroleum resin, continue to stir at constant temperature for 1 hour, remove air bubbles by vacuuming, discharge, cool to room temperature to obtain base rubber. S22. Add the base adhesive to the kneader, heat to 130℃, and stir to melt; add polyvinylpyrrolidone, stir evenly for 30 minutes, then remove air bubbles by vacuuming, discharge the material, and cool to room temperature to obtain hot melt pressure-sensitive adhesive.

[0055] Comparative Example 3 A hot melt pressure-sensitive adhesive was prepared in this comparative example. The components and contents are shown in Table 10. Table 10. Components and content of hot melt pressure-sensitive adhesive in Comparative Example 3

[0056] The preparation steps are as follows: S21. Add naphthenic oil, SIS block copolymer and antioxidant to kneader, heat to 150°C, stir until there are no granular raw materials, add hydrogenated petroleum resin, continue to stir at constant temperature for 1 hour, remove air bubbles by vacuuming, discharge, cool to room temperature to obtain base rubber. S22. Add the base adhesive to the kneader, heat to 130℃, and stir to melt; add polyvinylpyrrolidone, stir evenly for 30 minutes, then remove air bubbles by vacuuming, discharge the material, and cool to room temperature to obtain hot melt pressure-sensitive adhesive.

[0057] Comparative Example 4 A hot melt pressure-sensitive adhesive was prepared in this comparative example. The components and contents are shown in Table 11. Table 11 Components and content of hot melt pressure-sensitive adhesive in Comparative Example 4

[0058] The preparation steps are as follows: S21. Add naphthenic oil, SIS block copolymer and antioxidant to kneader, heat to 150°C, stir until there are no granular raw materials, add hydrogenated petroleum resin, continue to stir at constant temperature for 1 hour, remove air bubbles by vacuuming, discharge, cool to room temperature to obtain base rubber. S22. Add the base adhesive to the kneader, heat to 130℃, and stir to melt; add polyvinylpyrrolidone, stir evenly for 30 minutes, then remove air bubbles by vacuuming, discharge the material, and cool to room temperature to obtain hot melt pressure-sensitive adhesive.

[0059] Performance testing 1. After the base adhesive and hot melt pressure-sensitive adhesive prepared in Example 1 were left at room temperature for 3 months, the crystallization behavior of the system was tested by differential scanning calorimetry (DSC) to determine whether the polythioctic acid-polyvinylpyrrolidone complex was stably formed, with pure thioctic acid crystals as a control: Figure 1 The DSC curves are for thioctic acid crystals after 3 months of storage. TA-1 is the result of the test immediately after 3 months, and TA-2 is the result of the test repeated immediately after the first test. Figure 1 It can be seen that pure lipoic acid crystals showed obvious endothermic peaks in crystallization melting in both tests, indicating that pure lipoic acid maintains a stable crystal structure after long-term storage, and the crystallization characteristics can be detected stably and repeatedly.

[0060] Figure 2 The figures show the DSC curves of the base adhesive and hot melt pressure-sensitive adhesive in Example 1 after 3 months of storage. BA represents the base adhesive tested immediately after 3 months, BA-(PTA-PVP)-1 represents the hot melt pressure-sensitive adhesive tested immediately after 3 months, and BA-(PTA-PVP)-2 represents the hot melt pressure-sensitive adhesive tested immediately after the first test. Figure 2It can be seen that the pure base adhesive does not have a thioctic acid crystallization melting peak, and the hot melt pressure sensitive adhesive containing compound does not show the crystallization melting peak corresponding to thioctic acid crystals under both immediate testing and immediate repeated testing conditions, and the trends of the two test curves are consistent, indicating that the thermal behavior of the system is stable.

[0061] The above results indicate that thioctic acid and polyvinylpyrrolidone have fully reacted to form a polythioctic acid-polyvinylpyrrolidone complex. Thioctic acid no longer exists in free crystal form. The complex has good compatibility with the base adhesive. After long-term storage, no thioctic acid precipitates or recrystallizes, and the structure is stable and reliable.

[0062] 2. The hot melt pressure-sensitive adhesives prepared in Examples 1-7 and Comparative Examples 1-4 were uniformly coated onto 80g of polyethylene terephthalate (PET) substrate using a direct coating method, with the coating thickness controlled at 0.12mm, to obtain test adhesive tapes. Subsequently, the annular initial tack, underwater adhesive peel strength, and shear force of the hot melt pressure-sensitive adhesives were tested at 26±2℃, as detailed below: 1) Freshwater underwater adhesive peel strength test: The adhesive tape was directly bonded to the steel plate substrate in a fresh water environment; a 2kg standard roller was used to roll back and forth on the bonding surface 3 times to ensure tight adhesion; the bonded sample was immersed in water for 24 hours, and then the surface moisture was wiped off; the 180° peel strength test was carried out in accordance with GB / T 2792-2014 "Test Method for Peel Strength of Adhesive Tape", and the peel strength and detachment were recorded.

[0063] 2) Underwater adhesive shear force test in seawater: Prepare simulated seawater containing 24.5±0.5g sodium chloride, 4.8±0.2g anhydrous magnesium sulfate, and 1.8±0.2g anhydrous calcium chloride per liter of water. Adhesive tape is bonded to a steel plate substrate in the simulated seawater environment, rolled three times with a 2kg roller, and immersed in water for 24 hours. Lap shear test is performed according to GB / T 7124-2008 "Determination of Tensile Shear Strength of Adhesives" (Rigid Material to Rigid Material), and the shear force and detachment are recorded.

[0064] 3) Ring-shaped initial tack test: Refer to GB / T 31125-2014 "Test Method for Initial Tack of Adhesive Tape - Ring Method" to test the ring initial tack of the adhesive tape, and record the initial tack value and the amount of adhesive residue.

[0065] Table 12 Underwater adhesive peel strength of hot melt pressure-sensitive adhesives in Examples 1-4 and Comparative Examples 1-4

[0066] Table 12 shows the underwater adhesive peel strength of the hot melt pressure-sensitive adhesives in Examples 1-4 and Comparative Examples 1-4. As shown in Table 12, the peel strength of the pure adhesive is 35.94 N / inch, with localized detachment, indicating insufficient underwater bonding stability. In Comparative Examples 1-4, only polyvinylpyrrolidone was added, and the peel strength was 0 N / inch, with complete detachment, indicating that polyvinylpyrrolidone alone cannot achieve effective underwater bonding. In Examples 1-4, the introduction of a polythioctic acid-polyvinylpyrrolidone compound significantly improved the underwater bonding performance. Example 2 (thioctic acid: polyvinylpyrrolidone = 2:1, w / w) achieved a peel strength of 53.49 N / inch with no detachment, representing the optimal ratio for the compound. These results indicate that the polythioctic acid-polyvinylpyrrolidone compound is a necessary condition for achieving underwater bonding; the synergistic effect of the two can break the interfacial water film and improve wetting and adhesion.

[0067] Table 13 Underwater adhesive peel strength and ring initial tack of the hot melt pressure-sensitive adhesives in Examples 2 and 5-7

[0068] Table 13 shows the underwater adhesive peel strength and ring tack of the hot melt pressure-sensitive adhesives in Examples 2 and 5-7. As can be seen from Table 13, Examples 2, 5, 6, and 7 all showed no peeling, with peel strengths of 53.49, 53.58, 51.02, and 48.75 N / inch, respectively, and no peeling occurred after 24 hours. The initial tack performance and residue were also good. Among them, Example 5 showed the highest peel strength (53.58 N / inch) and the largest ring tack (47.63 N / inch) when the content of polythioctic acid-polyvinylpyrrolidone compound was 5 wt%, with no peeling. The test showed no residue, indicating that 5 wt% of polythioctic acid-polyvinylpyrrolidone compound was the optimal addition amount, which can balance adhesive strength, initial tack, and cohesive integrity.

[0069] Table 14. Underwater adhesive shear forces of the hot melt pressure-sensitive adhesives in Example 5 and Comparative Example 4

[0070] Table 14 shows the seawater adhesion shear force of the hot melt pressure-sensitive adhesives in Example 5 and Comparative Example 4. As can be seen from Table 14, the pure base adhesive and Comparative Example 4 completely detached after being soaked in seawater for 24 hours, with a shear force of 0. The seawater environment shear force of the hot melt pressure-sensitive adhesive in Example 5 reached 70.86 N, with no detachment. This indicates that the hot melt pressure-sensitive adhesive provided by the present invention can still maintain stable adhesion in the high-salt and high-corrosion environment of seawater and has excellent environmental tolerance.

[0071] Table 15 Performance Comparison of Example 5 Hot Melt Pressure Sensitive Adhesive with Conventional Hot Melt Adhesives of the Same Type

[0072] Table 15 compares the performance of the hot melt pressure-sensitive adhesive of Example 5 with that of conventional hot melt adhesives of the same type. As shown in Table 15, the peel strength of the underwater hot melt pressure-sensitive adhesive of the present invention is 53.58 N / inch, which is significantly higher than that of acrylamide, acrylic, polyurethane and existing thioctic acid-based supramolecular adhesives. It also maintains the inherent advantages of hot melt processing, solvent-free and fast application, and its comprehensive performance far exceeds that of existing underwater bonding systems.

Claims

1. A hot melt pressure sensitive adhesive, characterized in that, By weight percentage, it includes the following components: base rubber 80wt%-95wt%, thioctic acid 3wt%-15wt%, and polyvinylpyrrolidone 1wt%-7wt%.

2. The hot melt pressure-sensitive adhesive according to claim 1, characterized in that, In the hot melt pressure-sensitive adhesive, the mass ratio of thioctic acid to polyvinylpyrrolidone is (1-8):

1.

3. The hot melt pressure-sensitive adhesive according to claim 1, characterized in that, The base adhesive comprises the following components by weight: 22-34 parts of SIS block copolymer, 37-56 parts of hydrogenated petroleum resin, 20-30 parts of naphthenic oil, and 0.1-0.5 parts of antioxidant.

4. The hot melt pressure-sensitive adhesive according to claim 3, characterized in that, The base adhesive is prepared by a method comprising the following steps: mixing naphthenic oil, SIS block copolymer and antioxidant, stirring continuously under heating conditions until the system is completely melted and free of particulate raw materials; adding hydrogenated petroleum resin, continuing to stir at a constant temperature, and performing vacuum degassing on the mixture to obtain the base adhesive.

5. The hot melt pressure-sensitive adhesive according to claim 4, characterized in that, The base adhesive is prepared at a heating temperature of 140-160℃. And / or, the duration of continued constant-temperature stirring is 0.5-1.5 h.

6. The method for preparing the hot melt pressure-sensitive adhesive according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Mix thioctic acid and polyvinylpyrrolidone and heat to react to obtain polythioctic acid-polyvinylpyrrolidone complex; S2. After heating and melting the base adhesive, add the polythioctic acid-polyvinylpyrrolidone compound and mix well. Degas under vacuum to obtain the hot melt pressure-sensitive adhesive.

7. The method for preparing the hot melt pressure-sensitive adhesive according to claim 6, characterized in that, In step S1, the heating reaction is carried out at a temperature of 120-140°C for 0.5-1.5 hours.

8. The method for preparing the hot melt pressure-sensitive adhesive according to claim 6, characterized in that, In step S2, the mixing time is 20-40 minutes.

9. The use of the hot melt pressure-sensitive adhesive according to any one of claims 1-5 in bonding on damp surfaces or in underwater environments.

10. The application according to claim 9, characterized in that, The underwater environment includes both freshwater and seawater environments.

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