Low-temperature activated wax powder for sealant or adhesive as well as preparation method and application of low-temperature activated wax powder

Abstract

The invention relates to the field of coating rheological additives, in particular to low-temperature activated wax powder for sealants or adhesives as well as a preparation method and application of the low-temperature activated wax powder, the wax powder comprises an aromatic unit with an aromatic core structure and a gradient hydrogen bond unit which can be formed among molecules and / or in molecules and at least comprises a weak hydrogen bond and a strong hydrogen bond; the aromatic core structure and the gradient hydrogen bond unit are cooperatively assembled to form a three-dimensional network structure through a pi-pi accumulation effect. By constructing a three-dimensional network structure based on the synergistic effect of gradient hydrogen bonds and pi-pi stacking, good consideration of low-temperature activation and storage stability is successfully achieved, and it is ensured that efficient activation and rapid thixotropic recovery can be achieved within the low-temperature interval of 40-60 DEG C through weak hydrogen bonds; and the strong hydrogen bond and the aromatic core skeleton provide a firm structural support for the system in storage and use states, so that performance degradation is effectively prevented.

Description

Technical Field

[0001] This invention relates to the field of rheology modifiers for coatings, and more particularly to a low-temperature activated wax powder for sealants or adhesives, its preparation method, and its application. Background Technology

[0002] In the industrial fields of sealants, adhesives, and coatings, wax powder, as an important rheology modifier and thixotropic agent, directly affects the application experience and reliability of the final product. For a long time, to achieve the activation of wax powder at lower temperatures, and even under relatively mild heating or shear conditions to rapidly reduce the system viscosity for easier stirring, pumping, and extrusion, technological improvements in the industry have mainly followed a clear path: intervening in the crystallization process of wax molecules themselves through chemical or physical means. A common practice is to introduce short-chain alkyl groups or polar groups such as hydroxyl and carboxyl groups into the wax molecule backbone. The introduction of these groups can indeed effectively disrupt the regular, compact packing of long-chain alkane molecules, reducing their overall crystallinity, thereby shifting the melting temperature range of the wax powder towards lower temperatures. This approach has alleviated the difficulties of construction in low-temperature environments to some extent, and has shown certain application value, especially in cold seasons or energy-sensitive production processes.

[0003] However, in pursuit of lower activation temperatures, the regularity of molecular chains is excessively disrupted, resulting in a fragile three-dimensional network structure of the wax powder. The direct consequence is that while the modified wax powder may exhibit good flowability at 40-50 degrees Celsius, its high-temperature stability is significantly reduced. In high-temperature environments during summer or in certain specific applications, when the temperature rises above 60 degrees Celsius, this weakened network structure is highly susceptible to overall relaxation or even collapse. This leads to a sharp decrease in the viscosity of the sealant or adhesive system, resulting in problems such as sagging, deformation, and even penetration, severely impacting the long-term safety and durability of the product.

[0004] On the other hand, even for the low-temperature activation performance itself, traditional modification methods have limitations. Because the modification methods are relatively simple, they usually only focus on chemical modification at the molecular level, lacking fine-tuning at the supramolecular structure level of the wax powder. This results in a thixotropic network that is often coarse, uneven, and unstable. The strength and density of the network structure can vary significantly between different batches of products, and even between different parts of the same batch. This directly manifests as large fluctuations in product performance, inconsistent extrusion feel during application, and poor predictability of anti-sagging effects, posing a significant challenge to quality control. More importantly, this coarse network often recovers unsatisfactorily in terms of recovery speed and degree after being subjected to shear forces, making it difficult to achieve the ideal thixotropic cycle of rapid and precise "shear thinning" and "static thickening."

[0005] Furthermore, existing technologies often fall short of meeting the stability requirements of wax powder during storage. An ideal wax powder additive not only needs to perform well during application but also needs to maintain stable physicochemical properties throughout the entire storage period from production to actual use. However, many low-temperature activated wax powders obtained through traditional methods have a metastable structure. Under normal temperature storage, especially in accelerated aging experiments simulating summer storage conditions (such as 50°C heat storage), their network structure slowly evolves over time, leading to phenomena such as decreased viscosity, filler sedimentation, or oil precipitation in the added sealant system, directly affecting the product's shelf life and can-opening performance.

[0006] Therefore, those skilled in the art have long faced a prominent technical challenge: how to break through the existing technological framework and develop a novel wax powder material that can achieve rapid and uniform activation under low-temperature conditions, providing excellent ease of application, while simultaneously possessing outstanding high-temperature stability and long-term storage stability, and whose thixotropic behavior should exhibit high repeatability and rapid responsiveness. However, no successful precedent has yet been found in the existing technology that can effectively reconcile these contradictions, leaving a clear and urgent need for innovation in this field. Summary of the Invention

[0007] This application aims to overcome the shortcomings of existing technologies that rely on single-dimensional molecular modification and thus cannot simultaneously achieve both low-temperature activation performance and long-term storage stability of wax powder materials. Therefore, it provides a low-temperature activated wax powder for sealants or adhesives, its preparation method, and its application to overcome the above-mentioned deficiencies.

[0008] To achieve the above-mentioned objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a low-temperature activated wax powder for sealants or adhesives. The wax powder contains aromatic units with an aromatic core structure and units capable of forming at least two different strengths of gradient hydrogen bonds between molecules and / or within molecules. The aromatic core structure is assembled with gradient hydrogen bond units through π-π stacking to form a three-dimensional network structure; The gradient hydrogen bond network includes weak hydrogen bonds and strong hydrogen bonds; wherein... The weak hydrogen bonds can be reversibly broken and rebuilt within a first temperature range of 30°C to 70°C to provide low-temperature activation and thixotropy; The strong hydrogen bonds remain stable within the first temperature range of 30°C to 70°C to ensure storage stability.

[0009] As described in the background section, in order to reduce the activation temperature of wax powder, existing technologies usually adopt methods such as introducing short chains or polar groups to weaken intermolecular forces. Although this improves the low-temperature construction performance to a certain extent, it inevitably sacrifices the high-temperature stability and storage stability of the material, making it difficult to balance the product performance.

[0010] Based on the above understanding, this invention abandons the simple molecular chain disassembly strategy and instead adopts a construction concept of "molecular assembly engineering". The core concept of this application lies in actively constructing a dynamic and stable three-dimensional network with intelligent response characteristics, rather than passively weakening the internal structure of the wax powder. The realization of this concept relies on the synergy of two key designs: the gradient hydrogen bond network and the π-π stacking interaction of aromatic cores.

[0011] Specifically, this application incorporates carefully designed hydrogen bond types of varying strengths: weak and strong hydrogen bonds. The weak hydrogen bonds are endowed with the property of reversible breakage and reconstruction within a specific low-temperature range (e.g., 30-70℃). They function like a sensitive "switch," rapidly opening under construction shear forces to reduce viscosity and facilitate easy extrusion, and quickly closing again after stress removal to instantly restore the structure and prevent sagging. Meanwhile, the strong hydrogen bonds remain stable throughout this low-temperature range. Together with the equally stable aromatic nucleus π-π stacking interactions, they form the rigid "skeleton" of the entire three-dimensional network. This skeleton is crucial, ensuring that even during the dynamic process of temporary failure of weak hydrogen bonds, the entire system does not collapse, providing a template and support for rapid and orderly structural recovery.

[0012] The strategy employed in this application, combining dynamic gradient hydrogen bonds with a static rigid framework (π-π stacking and strong hydrogen bonds), allows for precise, on-demand control of material properties rather than simply weakening or enhancing a single force. This is achieved through the functional differentiation and synergistic interaction of different forces. In low-temperature construction scenarios, the dynamic characteristics dominated by weak hydrogen bonds facilitate activation; while in static storage conditions, the stable framework dominated by strong hydrogen bonds and π-π stacking plays a decisive role. Together, they lock the entire network structure, enabling it to resist creep and relaxation under ambient and even higher thermal storage conditions. This significantly improves the storage stability of the wax powder and its added sealant products, effectively preventing viscosity changes and sedimentation during storage.

[0013] Therefore, in summary, this invention, through an ingenious "dynamically stable network" architecture, allows the previously contradictory low-temperature activation and storage stability to coexist within the same material. Compared to the compromise solutions in existing technologies that sacrifice one for the other, this invention provides a more fundamental solution, enabling the wax powder in this application to not only exhibit excellent low-temperature activation performance but also rapid thixotropic recovery. More importantly, it achieves long-term storage stability that was previously difficult to attain, providing new possibilities for the application of sealants and adhesives in more demanding environments.

[0014] Preferably, the first temperature range is 40°C to 60°C.

[0015] Preferably, the weak hydrogen bond is selected from hydrogen bonds formed by one or more of aliphatic amide bonds, ester bonds, hydroxyl groups, or carboxyl groups.

[0016] Preferably, the strong hydrogen bond is selected from one or more of aromatic amide bonds, urea groups, or sulfonamide groups to form hydrogen bonds.

[0017] The weak hydrogen bond sources selected in this application (aliphatic amide bonds, ester bonds, etc.) have relatively low bond energies and good molecular chain segment flexibility. This allows them to preferentially undergo reversible breakage when external energy (such as heat or shear force) increases slightly, thereby efficiently achieving the low-temperature activation and instantaneous thixotropic response sought in the main claim. Conversely, the selected strong hydrogen bond sources (aromatic amide bonds, urea groups, etc.) have inherent structural rigidity and high bond energies, enabling them to firmly combine with the π-π stacking of aromatic nuclei, jointly forming a rigid framework that remains stable even at low-temperature activation temperatures. This rigid framework not only ensures that the system structure does not collapse when weak hydrogen bonds break, providing a template for rapid recovery, but more importantly, it greatly enhances the mechanical strength and thermal stability of the entire three-dimensional network under static storage conditions, thereby directly supporting and strengthening the key technical effect of "ensuring storage stability" in the main claim.

[0018] Preferably, the aromatic nucleus is selected from one or more of benzene ring, naphthalene ring, biphenyl or anthracene ring.

[0019] Secondly, the present invention also provides a method for preparing the low-temperature activated wax powder for the sealant or adhesive, the method comprising the following steps: (a) Provide monomers containing aromatic nuclei, as well as monomers that can provide weak and strong hydrogen bonds; (b) During the synthesis process, by controlling the reaction sequence and conditions, the monomers are reacted to generate polymer molecules with rigid aromatic units and flexible segments; (c) After or simultaneously with step (b), under conditions of induced molecular self-assembly, the polymer molecules form the three-dimensional network structure through the synergistic effect of π-π stacking of aromatic nuclei and gradient hydrogen bonds.

[0020] The selection of aromatic core monomers and monomers with specific strong and weak hydrogen bonds in step (a) of this application is the basis for constructing functionalized molecules. This step ensures that the final polymer molecule has the "innate ability" to self-assemble.

[0021] Step (b) employs a "stepwise polycondensation" method, which involves first synthesizing a flexible segment prepolymer rich in weak hydrogen-bonded groups and then copolymerizing it with a monomer carrying an aromatic core and strong hydrogen-bonded groups. This effectively achieves modular and controllable connection between "rigid aromatic units" and "flexible segments" from the source of molecular chain synthesis, thus laying a precise chemical structural foundation for the subsequent formation of a gradient-distributed hydrogen bond network and regular π-π stacking.

[0022] However, simply synthesizing potential polymer molecules through step (b) is far from sufficient; a specific external environment must be created to guide these molecules into an ordered and targeted assembly. "Programmed cooling" is the core method for achieving this induction. By cooling the reaction system from the dissolution high temperature to room temperature at a slow, controllable rate (e.g., decreasing by 0.1°C to 2°C per minute), a tranquil environment is provided for the self-assembly of the molecules. In this process, the aromatic nuclei, with the greatest structural rigidity and strongest interactions, preferentially align face-to-face through π-π stacking interactions, forming a stable skeletal framework. Subsequently, strong hydrogen-bonded groups seek optimal positions within the framework for anchoring, further strengthening the framework. Finally, weak hydrogen bonds on the flexible segments fill and connect within the established stable framework, ultimately forming the ideal three-dimensional network structure composed of a stable framework and dynamic switching.

[0023] Therefore, in summary, the method in this application can effectively avoid the disorder and defects of the microstructure by precisely controlling the reaction sequence and assembly conditions, so that each batch of wax powder has highly repeatable and excellent performance, thereby greatly improving the consistency and reliability of product performance. Secondly, this method is "tailor-made" to achieve a specific microstructure, thus enabling the efficient and stable preparation of products with the aforementioned unique properties, namely, wax powder with good low-temperature activation, rapid thixotropic recovery, and outstanding storage stability.

[0024] Preferably, the controlled reaction sequence in step (b) is a stepwise polycondensation reaction, specifically including: (b1) First, the monomer that provides the weak hydrogen bond is reacted to form a first prepolymer; (b2) Then, the first prepolymer is copolymerized with a monomer containing an aromatic core that can provide the strong hydrogen bond to generate the polymer molecule.

[0025] Existing copolymerization technologies often prioritize simplicity and efficiency, tending to randomly copolymerize monomers with different functions. This inevitably results in a random distribution of functional groups on the molecular chain, failing to form functionally defined regional structures. This invention, however, takes the opposite approach, actively and purposefully editing the structure during the molecular chain synthesis stage through a specific "weak-to-strong" reaction sequence.

[0026] In this application, step (b1) first synthesizes a first prepolymer rich in weakly hydrogen-bonded groups, which essentially preferentially constructs the "dynamic unit" responsible for low-temperature activation and thixotropic response at the molecular level. Step (b2) then introduces a monomer containing an aromatic core and strong hydrogen bonds to copolymerize with it, which precisely installs the "rigid unit" that constitutes a stable framework on this basis. This specific sequence of steps (b1) and (b2) ensures that the final polymer molecule has a clear "block" or "gradient" characteristic, that is, the flexible chain segments (weakly hydrogen-bonded regions) and rigid aromatic units (strong hydrogen bonds and π-π stacking regions) achieve a certain degree of separation and orderly arrangement on the molecular chain.

[0027] Polymer molecules with clearly defined functional partitions can more accurately and efficiently align themselves through intermolecular forces under induced conditions such as programmed cooling: rigid units preferentially form a stable backbone through π-π stacking, while flexible units form a reversibly cross-linked network around the backbone. If random copolymerization is used, the molecular chain structure is disordered, self-assembly will lack directionality, and it will be difficult to form a highly ordered, functionally synergistic three-dimensional network.

[0028] Preferably, the conditions for inducing molecular self-assembly in step (c) include programmed cooling. The cooling rate of the program is controlled within the range of 0.1°C to 2°C per minute.

[0029] In existing technologies, the cooling process after wax powder synthesis is usually regarded as a simple physical change, and rapid cooling methods are often adopted with production efficiency as the guiding principle. This method causes the molecular chains to not have time to arrange themselves in an orderly manner, and can only passively and randomly solidify into metastable structures with higher energy. This is one of the root causes of the coarse network and uneven performance of traditional wax powder.

[0030] This invention precisely controls the cooling rate within the range of 0.1°C to 2°C per minute, thereby providing sufficient time and energy to the molecular chains through this sufficiently slow cooling rate, enabling them to assemble in a "stepwise" and "orderly" manner based on their respective chemical properties (the rigidity of the aromatic nucleus and the difference in the strength of hydrogen bonds).

[0031] At this rate, the most strongly interacting aromatic nuclei are the first to arrange themselves in an orderly manner through π-π stacking interactions, forming a stable basic framework. Subsequently, strong hydrogen-bonded groups combine in an orderly manner on the already formed framework, further reinforcing the network. Finally, the weak hydrogen bonds on the flexible segments complete the construction of dynamic cross-linking points within the stable framework. If the cooling is too rapid, various intermolecular forces will act almost simultaneously and disorderly, leading to chaotic assembly and an inability to form a finely defined structure; while if the cooling is too slow, the production efficiency is too low, making it unsuitable for industrial use.

[0032] Preferably, steps (b) and / or (c) are carried out in an organic solvent system; The organic solvent is a solvent that can dissolve the polymer molecules and induce their orderly assembly during the programmed cooling process.

[0033] Preferably, the organic solvent is one or more of toluene, xylene, or N-methylpyrrolidone.

[0034] Preferably, steps (b) and / or (c) are carried out in an organic solvent system; The organic solvent is a solvent that can dissolve the polymer molecules and induce their orderly assembly during the programmed cooling process.

[0035] Thirdly, the present invention also provides a sealant or adhesive composition. It contains low-temperature activated wax powder for sealant or adhesive as described above; The content of the low-temperature flexible activated wax powder is 1 wt% to 10 wt% based on the total weight of the composition.

[0036] Therefore, this application has the following beneficial effects: First, by constructing a three-dimensional network structure based on the synergistic effect of gradient hydrogen bonds and π-π stacking, a good balance between low-temperature activation and storage stability was successfully achieved. The weak hydrogen bonds ensured efficient activation and rapid thixotropic recovery in the low-temperature range of 40-60℃, while the strong hydrogen bonds and aromatic core framework provided solid structural support for the system in storage and use, effectively preventing performance degradation. Secondly, the unique molecular assembly structure endows the product with excellent workability, exhibiting obvious shear thinning behavior and immediate recovery ability, effectively overcoming the sagging problem while ensuring smooth application. Finally, the stepwise synthesis and programmed cooling controllable assembly process described above can stably and repeatedly produce products with the above-mentioned fine microstructure, which not only significantly improves the consistency and reliability of product performance, but also provides a solid guarantee for expanding its application as a sealant and adhesive in harsh environments. Attached Figure Description

[0037] Figure 1 This is a comparative graph showing the rheological properties of solvent-free epoxy coatings, including the low-temperature activated wax powder in Example 1 of this application and the foreign competitor in Comparative Example 5.

[0038] Figure 2 This is a comparison chart of the sagging test results of the low-temperature activated wax powder in Example 1 of this application and the solvent-free epoxy coating of the foreign competitor in Comparative Example 5. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0040] Example 1 A method for preparing a low-temperature activated wax powder for sealants or adhesives includes the following steps: (1) Synthesis of the first prepolymer (containing weak hydrogen bonds): 100 g of lauric acid and 18 g of ethylenediamine (molar ratio 1:1) were added to a four-necked flask equipped with a stirrer, thermometer, and nitrogen inlet tube. Under nitrogen protection, the temperature was slowly increased to 160 °C and the reaction was carried out for 2 hours. The reaction progress was monitored by measuring the acid value of the system. When the acid value dropped below 5 mg KOH / g, the aliphatic polyamide prepolymer with terminal amino groups (the first prepolymer) was obtained.

[0041] (2) Introduction of aromatic nuclei and strong hydrogen bonds: 33 g of terephthalic acid and 29 g of 1,6-hexanediamine (molar ratio of 1:1 with terephthalic acid) were added to the above reaction system. At the same time, 300 g of toluene was added as a solvent. The reaction system was heated to 180 °C and refluxed at this temperature for 3 hours to generate polymer molecules containing rigid aromatic units and flexible segments.

[0042] (3) Temperature-programmed self-assembly: After the reaction is completed, heating is stopped and the temperature-programmed control system is started to slowly cool the reaction system from 180°C to 30°C at a rate of 0.5°C per minute. During this process, polymer molecules form a three-dimensional network structure through the synergistic effect of π-π stacking of aromatic cores and gradient hydrogen bonds (weak hydrogen bonds of aliphatic amides and strong hydrogen bonds of aromatic amides), and the system gradually changes from solution to gel.

[0043] (4) Post-processing: The obtained gel-like product was dried in a vacuum drying oven at 60°C for 12 hours to completely remove the solvent. Subsequently, the dried solid was pulverized and sieved using a pulverizer to obtain white wax powder with a particle size distribution of 10-25 micrometers, which was denoted as sample W-1.

[0044] Example 2 A method for preparing a low-temperature activated wax powder for sealants or adhesives includes the following steps: (1) Synthesis of the first prepolymer (containing weak hydrogen bonds): The operation was exactly the same as in Example 1. Under nitrogen protection, 100 g of lauric acid and 18 g of ethylenediamine (molar ratio 1:1) were reacted at 160 °C for 2 hours to obtain an aliphatic polyamide prepolymer with terminal amino groups.

[0045] (2) Introduction of aromatic nuclei and strong hydrogen bonds: The procedure is exactly the same as in Example 1. 33 g of terephthalic acid, 29 g of 1,6-hexanediamine and 300 g of toluene solvent were added to the reaction system. The reaction system was heated to 180 °C and refluxed for 3 hours to generate polymer molecules.

[0046] (3) Temperature-programmed self-assembly: After the reaction is completed, heating is stopped and the temperature-programmed control system is started, with the cooling rate set to 1.8℃ per minute. The reaction system is slowly cooled from 180℃ to 30℃ at this rate, allowing the polymer molecules to complete the orderly assembly.

[0047] (4) Post-processing: The subsequent drying and pulverizing steps are exactly the same as in Example 1, and white wax powder is obtained, which is recorded as sample W-2.

[0048] Example 3 Except for the cooling rate in step 3, the other steps in Example 3 are basically the same as those in Example 1.

[0049] Step 3 is modified to: the cooling rate of the program is controlled to decrease by 0.1℃ per minute.

[0050] The post-processing steps were the same as in Example 1, resulting in wax powder sample W-3.

[0051] Example 4 A method for preparing a low-temperature activated wax powder for sealants or adhesives includes the following steps: (1) Synthesis of the first prepolymer (containing ester bonds and weak hydrogen bonds): In a reaction flask, 100 g of polyethylene glycol (PEG-1000) and 29 g of adipic acid (molar ratio 1:1.1, acid in excess) and 0.1 g of p-toluenesulfonic acid were added as catalysts. The reaction was carried out at 140 °C under nitrogen protection for 4 hours until the acid value reached the theoretical value, and a polyester prepolymer with carboxyl-terminated groups was obtained.

[0052] (2) Introduction of aromatic cores and strong hydrogen bonds (urea groups): The system was cooled to 80°C, and 200 g of NMP solvent was added to dissolve the prepolymer. Then, 17.4 g of toluene-2,4-diisocyanate (TDI, with a molar ratio of 1:1 to the prepolymer terminal carboxyl group) was added dropwise, and the reaction was maintained at this temperature for 1 hour to obtain a prepolymer containing isocyanate terminal groups. Finally, 5.4 g of p-phenylenediamine (PPDA, with a molar ratio of 1:1 to TDI) was added for chain extension, and the reaction was continued at 80°C for 2 hours to generate a polymer containing urea group strong hydrogen bonds. In this step, the aromatic cores of TDI and PPDA together constitute rigid units.

[0053] (3) Programmed cooling to induce self-assembly: After the reaction is completed, programmed cooling is started, and the temperature is reduced from 80°C to 30°C at a rate of 1.0°C per minute to induce molecular self-assembly.

[0054] (4) Post-processing: The subsequent drying and pulverizing steps are the same as in Example 1, and wax powder sample W-4 is obtained.

[0055] Example 5 A method for preparing a low-temperature activated wax powder for sealants or adhesives includes the following steps: (1) Synthesis of the first prepolymer (containing a carboxyl group with a weak hydrogen bond): In a dry reaction flask equipped with a stirrer and a thermometer, add 100 g of dimer acid (approximately 0.18 mol, based on carboxyl groups) and 200 g of DMF solvent. Under an ice-water bath cooling and nitrogen atmosphere, slowly add 25 g (approximately 0.09 mol) of biphenyl-4,4'-disulfonyl chloride (BDSC) dissolved in 50 g of DMF. After the addition is complete, remove the ice bath and react at room temperature for 6 hours. This step involves a partial reaction between the carboxyl group of the dimer acid and the sulfonyl chloride group of BDSC to generate a flexible prepolymer with a sulfonyl chloride end cap and carboxyl groups on the side chains.

[0056] (2) Introduction of aromatic nuclei and strong hydrogen bonds (sulfonamide groups): 32 g (approximately 0.13 mol) of 4,4'-diaminodiphenyl sulfone (DDS) and 15 g of pyridine (as an acid absorber) were added in batches to the above reaction system. The reaction system was slowly heated to 80 °C and the reaction was continued at this temperature for 8 hours. In this step, the sulfonyl chloride groups at the end of the prepolymer react with the amino groups of DDS to generate strong hydrogen bonds of sulfonamide groups (-SO2NH-), while introducing more aromatic nuclei (from DDS and BDSC), ultimately generating an amide polymer molecule with rigid biphenyl / DDS aromatic units and flexible dimer acid segments.

[0057] (3) Temperature-programmed self-assembly: After the reaction is complete, stop heating. Start the temperature-programmed control system and slowly cool the reaction system from 80°C to 25°C at a rate of 1.2°C per minute. During this process, polymer molecules self-assemble into a three-dimensional network structure through the π-π stacking of aromatic cores (biphenyl, diphenyl sulfone groups) and the gradient hydrogen bond network composed of carboxyl groups (weak hydrogen bonds) and sulfonamide groups (strong hydrogen bonds).

[0058] (4) Post-treatment: The obtained gel-like product was washed three times with ethanol to remove pyridine hydrochloride and residual solvent. Then it was dried in a vacuum drying oven at 60°C for 12 hours. Finally, the dried solid was crushed and sieved to obtain a light yellow wax powder with a particle size distribution of 15-40 micrometers, which was designated as sample W-5.

[0059] Example 6 A method for preparing a low-temperature activated wax powder for sealants or adhesives includes the following steps: (1) Referring to Example 1, 100 g of sebacic acid and 22 g of ethylenediamine were reacted to generate an aliphatic polyamide prepolymer.

[0060] (2) Introducing naphthalene ring and strong hydrogen bond: Add 43 g of 2,6-naphthalenedicarboxylic acid (NDA, providing naphthalene ring) and 16 g of p-phenylenediamine (PPDA) to the prepolymer in a molar ratio of 1:1. Add 300 g of xylene and heat to 190 °C for 3 hours.

[0061] (3) Programmed cooling-induced self-assembly: The programmed cooling rate is controlled at 0.8℃ per minute, cooling from 190℃ to 40℃.

[0062] (4) Post-processing: Same as in Example 1, to obtain wax powder sample W-6.

[0063] Comparative Example 1 A method for preparing a low-temperature activated wax powder for sealants or adhesives includes the following steps: (1) Referring to step 1 of Example 1, an aliphatic polyamide prepolymer with terminal amino groups was synthesized.

[0064] (2) After the synthesis is completed, step 2 of Example 1 is not performed (i.e., terephthalic acid and 1,6-hexanediamine are not added). 300 g of toluene is added directly to the prepolymer and stirred at 160 °C until it is dissolved evenly.

[0065] (3) Subsequently, the temperature was cooled to 30°C using the same programmed cooling process as in Example 1 (reducing by 0.5°C per minute).

[0066] (4) The post-processing is the same as in Example 1, and the product is obtained, which is denoted as sample C-1.

[0067] Comparative Example 2 A method for preparing a low-temperature activated wax powder for sealants or adhesives includes the following steps: (1) Step 1 of Example 1 is omitted. 33 g of terephthalic acid, 29 g of 1,6-hexanediamine and 300 g of toluene are added directly to the reaction flask.

[0068] (2) The reaction system is heated to 180°C and refluxed for 3 hours to directly generate a highly rigid aromatic polyamide.

[0069] (3) Cooling is performed using the same programmed cooling process as in Example 1.

[0070] (4) The post-processing is the same as in Example 1, and a hard solid is obtained. After being crushed, it is recorded as sample C-2.

[0071] Comparative Example 3 A method for preparing a low-temperature activated wax powder for sealants or adhesives includes the following steps: (1) The stepwise reaction in Example 1 was changed to random copolymerization. All monomers (100 g lauric acid, 18 g ethylenediamine, 33 g terephthalic acid, 29 g 1,6-hexanediamine) were added to the reaction flask at once, along with 300 g toluene.

[0072] (2) Heat the reaction system to 180°C and reflux for 5 hours to allow all monomers to react randomly to form a polymer.

[0073] (3) Cooling is performed using the same programmed cooling process as in Example 1.

[0074] (4) The post-processing is the same as in Example 1, and the product is obtained, which is denoted as sample C-3.

[0075] Comparative Example 4 A method for preparing a low-temperature activated wax powder for sealants or adhesives includes the following steps: The raw materials and steps 1 and 2 are exactly the same as in Example 1, and a polymer solution is synthesized.

[0076] (3) After the reaction is complete, the reaction solution at 180°C is quickly poured into a large amount of ethanol at room temperature and stirred at high speed, so that it is instantly precipitated and cooled by solvent displacement. The cooling rate of this process is extremely fast, much higher than 2°C per minute.

[0077] (4) The precipitate was collected by filtration, dried and pulverized to obtain sample C-4.

[0078] Comparative Example 5 This comparative example uses commercially available polyamide waxes commonly used in this field (foreign competitors).

[0079] Comparative Example 6 In this comparative example, 1,10-sebacic acid was used instead of terephthalic acid in Example 1, and 1,12-dodecanediamine was used instead of 1,6-hexanediamine. Other raw materials remained unchanged, and the step-by-step polycondensation and programmed cooling were performed exactly as described in Example 1.

[0080] The wax powder sample prepared in Example 1 and the foreign competitor in Comparative Example 5 were applied to a solvent-free epoxy coating. The formulation and process of the solvent-free epoxy coating are shown in Table 1 below: Table 1 .

[0081] Figure 1 A comparison of the rheological properties of solvent-free epoxy coatings, including Example 1 of this application (trade name PA-7100) and the foreign competitor in Comparative Example 5, shows from the figure that the low-temperature activated wax powder in this application exhibits superior rheological properties. Sagging tests were performed on the foreign competitor coatings, including Examples 1 of this application and Comparative Example 5, and the test results are as follows. Figure 2 As shown in the figure, the sample containing the low-temperature activated wax powder (trade name PA-7100) of Example 1 of this application has a significantly higher anti-sagging effect than the sample containing foreign competing products.

[0082] In addition, the wax powder samples prepared in the above embodiments were also applied to the sealant system. The sealant formulation and process are shown in Table 1 below: Table 2 .

[0083] To comprehensively evaluate the overall performance of wax powder in sealant systems, this application conducted specific tests on it, and the test results are shown in Table 3 below: .

[0084] As can be seen from the data in the table above, the high shear viscosity of all embodiments (W-1 to W-6) of this application is significantly lower than that of comparative examples C-2 (difficult to extrude) and C-5 (conventional product), with extrudability values ​​between 115-130 g / min, exhibiting a smooth and easy application experience. In contrast, comparative example C-2, due to its strong hydrogen bonds, has a viscosity as high as 620 Pa·s and an extrudability of only 28 g / min, making it clearly unsuitable for application. This indicates that weak hydrogen bonds, acting as a "switch," are crucial for the low-temperature activation of this invention.

[0085] Furthermore, a higher thixotropic index (low shear viscosity / high shear viscosity) indicates faster network recovery after the shear force disappears, and stronger anti-sagging ability. The thixotropic indices of the examples (such as W-3 and W-6) are as high as 2.86 or higher, significantly higher than the conventional product C-5 (1.89) and all defective comparative examples (all below 2.3). In contrast, the thixotropic indices of comparative examples C-3 (random copolymer) and C-4 (rapid cooling) are only 1.48 and 1.44, respectively, demonstrating the lack of an ordered "gradient hydrogen bond network" and "molecular self-assembly" process, which prevents the formation of an efficient thixotropic structure.

[0086] The smaller the change in viscosity (2 rpm) after heat storage, the more stable the product's performance during storage. The embodiments in this application (such as W-1 and W-6) show high viscosity retention and gradual change after heat storage. In contrast, the viscosities of comparative examples C-1 (weak hydrogen bonds only) and C-6 (no π-π stacking) decreased significantly from 180 to 95 and from 320 to 250 after heat storage, respectively. The data from comparative example C-6 demonstrates that even with hydrogen bonds, the lack of a rigid framework provided by "π-π stacking" results in insufficient thermal stability of the network.

[0087] Therefore, in summary, this application successfully resolves the contradiction between low-temperature activation and long-term stability through the synergistic effect of gradient hydrogen bonds (weak hydrogen bond switching + strong hydrogen bond framework) and aromatic nucleus π-π stacking (stabilizing framework). The stepwise polycondensation and programmed cooling process during preparation is key to achieving the aforementioned ideal microstructure, while random copolymerization (C-3) or rapid cooling (C-4) both lead to significant performance degradation.

[0088] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A low-temperature activated wax powder for sealant or adhesive, characterized in that, the wax powder comprises aromatic units with aromatic core structure and units capable of forming at least two different strength gradient hydrogen bonds intermolecularly and / or intramolecularly; the aromatic core structure cooperatively assembles with the gradient hydrogen bond units to form a three-dimensional network structure through π-π stacking interaction; the gradient hydrogen bond network comprises weak hydrogen bonds and strong hydrogen bonds; wherein, the weak hydrogen bonds can reversibly break and rebuild in a first temperature range of 30-70℃, to provide low-temperature activation and thixotropy; the strong hydrogen bonds remain stable in the first temperature range of 30-70℃, to ensure storage stability. 2.The low-temperature activated wax powder for sealant or adhesive according to claim 1, characterized in that, the first temperature range is 40-60℃. 3.The low-temperature activated wax powder for sealant or adhesive according to claim 1, characterized in that, the weak hydrogen bonds are selected from one or more of aliphatic amide bonds, ester bonds, hydroxyl groups or carboxyl groups. 4.The low-temperature activated wax powder for sealant or adhesive according to any one of claims 1-3, characterized in that, the strong hydrogen bonds are selected from one or more of aromatic amide bonds, urea groups or sulfonamide groups. 5.The low-temperature activated wax powder for sealant or adhesive according to claim 1, characterized in that, the aromatic core is selected from one or more of benzene rings, naphthalene rings, biphenyl groups or anthracene rings. 6.A method for preparing the low-temperature activated wax powder for sealant or adhesive according to any one of claims 1-5, characterized in that, the method comprises the following steps: (a) providing monomers containing aromatic core and monomers capable of providing weak hydrogen bonds and strong hydrogen bonds; (b) in the synthesis process, by controlling the reaction sequence and conditions, the monomers are reacted to generate polymer molecules with rigid aromatic units and flexible chain segments; (c) after or simultaneously with step (b), under conditions inducing molecular self-assembly, the polymer molecules form the three-dimensional network structure through the synergistic effect of π-π stacking of the aromatic core and the gradient hydrogen bonds. 7.The method according to claim 6, characterized in that, in step (b), the control of the reaction sequence is a step-by-step polycondensation reaction, specifically comprising: (b1) first, the monomers capable of providing the weak hydrogen bonds are reacted to form a first prepolymer; (b2) then, the first prepolymer is copolymerized with monomers containing aromatic core and capable of providing the strong hydrogen bonds to generate the polymer molecules. 8.The method according to claim 6, characterized in that, in step (c), the conditions inducing molecular self-assembly include programmed cooling treatment; the rate of the programmed cooling is controlled in the range of 0.1-2℃ per minute. 9.The method according to claim 6, characterized in that, steps (b) and / or (c) are carried out in an organic solvent system; the organic solvent is a solvent capable of dissolving the polymer molecules and inducing their ordered assembly during the programmed cooling process; the organic solvent is one or more of toluene, xylene or N-methyl pyrrolidone.

10. A sealant or adhesive composition, characterized by, a low temperature activated wax powder for sealant or adhesive as claimed in any one of claims 1 to 5; a content of the low temperature flexible activated wax powder is 1 wt% to 10 wt% based on the total weight of the composition.

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