Multifunctional rubber auxiliary and preparation method thereof

Abstract

The application discloses a kind of multifunctional rubber auxiliaries and its preparation method in the field of rubber processing, the method is by the thiol-isocyanate bifunctional cage silsesquioxane and epoxy-terminated polysulfide compound, end thiol liquid polysulfide rubber and allyl glycidyl ether are combined by photo-initiated click reaction to obtain epoxy-terminated polysulfide, then be blended with polybutadiene, stearic acid, zinc oxide and accelerator granulation, obtain multifunctional rubber auxiliary masterbatch.The auxiliary can provide nano-enhanced, dynamic covalent crosslinking and interfacial compatibility in rubber mixing, significantly improve the mechanical properties, aging resistance and processing stability of vulcanized rubber.Process conditions are mild, suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of rubber processing technology, and more specifically to a multifunctional rubber additive and its preparation method. Background Technology

[0002] Rubber, as an important polymer material, is widely used in tires, seals, shock-absorbing products, and other fields. Its overall performance is highly dependent on the synergistic effect of various additives in the formulation. Traditional rubber additives, such as vulcanizing agents, accelerators, reinforcing fillers, and antioxidants, can improve processability and mechanical properties, but they still face problems such as fatigue cracking, aging degradation, and insufficient interfacial compatibility under dynamic use environments. In recent years, with the increasing demand for high-performance rubber products, the development of multifunctional additives with reinforcement, toughening, self-healing, and durability functions has become a research hotspot. Among them, introducing dynamic chemical bonds is considered an effective strategy to improve the reversibility and adaptability of rubber networks. However, how to integrate multiple dynamic mechanisms into a single additive system without sacrificing processing stability remains a technical challenge.

[0003] Cage-like silsesquioxanes are widely used in polymer modification due to their unique nanoscale structure, high thermal stability, and functionalizability. By introducing reactive groups at their apex, chemical bonding with the rubber matrix can be achieved, thereby improving interfacial adhesion and dispersibility. On the other hand, the polysulfide bonds in the main chain of polysulfide rubber possess thermally or mechanically reversible exchange capabilities, belonging to typical dynamic covalent bonds, and showing great potential in endowing materials with self-healing and stress relaxation capabilities. However, commercially available polysulfide rubbers are mostly terminal mercapto or terminal chloropropyl structures, which are difficult to participate in the vulcanization crosslinking network when directly used in rubber blends, limiting their functionality. If their ends can be converted into epoxy groups that can participate in vulcanization through efficient click chemistry, they can become functional components with both dynamic covalent properties and crosslinking activity. At the same time, if non-covalent interactions such as hydrogen bonding or metal coordination can be further coupled, it is expected to construct a multi-scale, multi-mechanism synergistic dynamic network.

[0004] In existing technologies, some studies have attempted to combine siloxanes with polysulfide structures, but these often involve complex synthetic routes or the use of non-commercial intermediates, making industrialization difficult. Furthermore, most schemes do not adequately consider the rubber processing window, leading to degradation or side reactions of the additives during high-temperature mixing. Particularly noteworthy is that while the photoinitiated reaction between thiol-terminated polysulfide rubber and double-bonded epoxy monomers is theoretically feasible, incomplete end-capping and residual thiol groups interfering with the vulcanization system can easily occur if the functional group stoichiometry or raw material specifications are not precisely controlled. Therefore, there is an urgent need for a multifunctional rubber additive preparation method based on readily available raw materials, with mild process conditions, a well-defined structure, and integrated functions. This method should ensure the integrity of epoxy end-capping and achieve multiple effects such as nano-reinforcement, dynamic crosslinking, and interface optimization through component synergy, thereby significantly improving the overall service performance of rubber products. Summary of the Invention

[0005] The purpose of this invention is to provide a multifunctional rubber additive and its preparation method, which solves the technical problems of existing rubber additives having single function, poor dispersibility, insufficient dynamic performance and poor processing stability.

[0006] The present invention achieves the above objectives through the following technical solutions: A method for preparing a multifunctional rubber additive, comprising the following steps: S1. By weight, add 38-42 parts of polybutadiene and 1-3 parts of stearic acid to an emulsifier, heat to 98-102℃, and stir. Under nitrogen protection, add 14-16 parts of mercapto-isocyanate difunctional cage-type silsesquioxane and 24-26 parts of epoxy-terminated polysulfide in sequence, heat to 118-122℃, stir and mix, add 4-6 parts of zinc oxide and 2-4 parts of N-cyclohexyl-2-benzothiazole sulfenamide, and continue to shear and mix at 98-102℃ to obtain a mixture. Granulate the mixture through a twin-screw extruder at 110-120℃ to obtain a multifunctional rubber additive masterbatch. S2. In a mixing mill, add 80-120 parts of natural rubber, 40-60 parts of carbon black, 0-20 parts of silica, 3-15 parts of multifunctional rubber additive masterbatch, 2-5 parts of zinc oxide, 1-3 parts of stearic acid, 1-3 parts of antioxidant 6PPD, and 3-10 parts of paraffin oil and mix until the discharge temperature reaches 150-155℃. After discharge and cooling, a compound is obtained. In a two-roll mill, add the compound, 1-2.5 parts of sulfur, and 0.5-2 parts of accelerator CBS, mix at 60-70℃, sheet out in thin sheets, and vulcanize on a flat vulcanizing machine.

[0007] In this invention, the preparation of multifunctional rubber additive masterbatch achieves multi-component synergistic integration through melt blending. Polybutadiene is used as a carrier, as its high compatibility with natural rubber makes it an excellent dispersion medium for the functional components. Under heating and stirring, a mercapto-isocyanate difunctional cage-type silsesquioxane and an epoxy-terminated polysulfide are introduced sequentially. The former provides nano-reinforcement and interfacial chemical bonding capabilities, while the latter contributes to dynamic covalent cross-linking and energy dissipation mechanisms. Stearic acid acts as a lubricant and dispersant, promoting uniform distribution of each component; zinc oxide not only activates the vulcanization reaction but may also form weak coordination interactions with polar groups; sulfenamide accelerators regulate the stability of the masterbatch itself, preventing premature cross-linking during storage. After shear mixing and twin-screw extrusion granulation, a masterbatch with good flowability and uniform composition is obtained. During subsequent rubber compounding and vulcanization, the functional components in the masterbatch simultaneously participate in network construction: cage-like siloxanes are embedded into the matrix through chemical bonds, and epoxy-terminated polysulfide segments are integrated into the crosslinking points through epoxy ring-opening and polysulfide exchange, ultimately forming a composite vulcanized network with high strength, high damping, excellent fatigue resistance, and potential self-healing capabilities. The entire process requires no solvents, and all raw materials are commercially available, demonstrating promising prospects for industrialization.

[0008] According to a preferred embodiment of the present invention, in step S1, the shearing and mixing time at 98-102°C is 30-60 min.

[0009] According to a preferred embodiment of the present invention, in step S2, the initial temperature in the internal mixer is 70-80°C.

[0010] According to a preferred embodiment of the present invention, the method for preparing the mercapto-isocyanate difunctional cage-type silsesquioxane includes: A1. Octadecyl cage-type silsesquioxane and 3-mercapto-1-propanol are dissolved in anhydrous tetrahydrofuran, and azobisisobutyronitrile is added. The reaction is carried out under nitrogen protection at 75-80℃ to obtain a hydroxyl-functionalized POSS intermediate. The hydroxyl-functionalized POSS intermediate is dissolved in anhydrous tetrahydrofuran with isophorone diisocyanate, and dibutyltin dilaurate is added. An addition reaction is carried out under nitrogen protection at 58-62℃ to obtain a reaction solution. A2. Pour the reaction solution into cold n-hexane, filter, and obtain a precipitate. Wash the precipitate with n-hexane and dry it in a vacuum drying oven at 38-42℃.

[0011] In this invention, the preparation of thiol-isocyanate bifunctional cage-like silsesquioxanes is based on a two-step continuous click chemistry and addition reaction. First, octavinyl cage-like silsesquioxanes react with hydroxyl-containing thiols under free radical initiation conditions to undergo a thiol-ene click reaction. This process exhibits high selectivity and high conversion rate, converting some vinyl groups into thioether side chains containing terminal hydroxyl groups at mild temperatures, generating a partially hydroxyl-functionalized intermediate. Subsequently, this intermediate undergoes an isocyanate-hydroxy addition reaction with diisocyanate under the action of an organotin catalyst, forming a stable urethane bond, thereby introducing isocyanate functional groups onto the cage-like framework. The resulting product simultaneously contains unreacted thiol groups and newly generated isocyanate groups, possessing bifunctional reactivity. It can participate in vulcanization crosslinking through the thiol groups and also achieve chemical anchoring with the polymer matrix through the reaction of isocyanate with trace amounts of moisture or hydroxyl groups in rubber, significantly improving the interfacial compatibility and dispersion stability of the nanofiller.

[0012] According to a preferred embodiment of the present invention, in step A1, the reaction time is 4-6 hours under nitrogen protection and at 75-80°C.

[0013] According to a preferred embodiment of the present invention, in step A2, the drying time in a vacuum drying oven at 38-42°C is 24-30 hours.

[0014] According to a preferred embodiment of the present invention, the method for preparing the dynamically covalently bonded epoxy-terminated polysulfide includes: B1. In a three-necked flask, add mercapto-terminated liquid polysulfide rubber and allyl glycidyl ether; add phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, and react under nitrogen protection, irradiated by a UV-LED light source, at 25-35°C to obtain a reaction mixture; B2. Cool the reaction mixture, wash with deionized water, and dry the organic phase with anhydrous magnesium sulfate and then rotary evaporate.

[0015] According to a preferred embodiment of the present invention, in step B1, the reaction time under UV-LED light source irradiation and at 25-35°C is 2-4 hours; the terminal thiol liquid polysulfide rubber is ChloroL LP liquid polysulfide rubber.

[0016] In this invention, the synthesis of dynamically covalently bonded epoxy-terminated polysulfides employs a photo-initiated thiol-ene click strategy. Commercially available end-thiol liquid polysulfide rubber is used as the starting material. Its molecular chain contains active thiol groups at both ends, and the main chain consists of alternating alkylene groups and polysulfide bonds. Under ultraviolet light irradiation, a photoinitiator generates active free radicals, initiating a highly efficient addition reaction between the thiol groups and the carbon-carbon double bonds in allyl glycidyl ether. This reaction is rapid, quantitative, and produces no byproducts, and can be completed at room temperature, avoiding the damage to polysulfide bonds caused by high temperatures. After the reaction, the thiol groups at both ends of the polysulfide rubber are converted into epoxy groups linked by propyl ether chains, forming a true epoxy-terminated structure. The resulting product retains the reversibly broken and recombined dynamic covalent polysulfide bonds in the main chain, while the terminal epoxy groups can participate in the construction of the rubber vulcanization network, making the polysulfide segments part of the cross-linked network rather than an inert plasticizing phase. This design effectively solves the problems of easy migration and poor compatibility of traditional polysulfide rubber in vulcanized rubber, and endows the material with stress relaxation and self-healing capabilities.

[0017] According to a preferred embodiment of the present invention, in step B2, the reaction mixture is cooled to 24-26°C.

[0018] The present invention also provides a multifunctional rubber additive prepared according to the preparation method of the multifunctional rubber additive described above.

[0019] The beneficial effects of this invention are as follows: The multifunctional rubber additive provided by this invention exhibits a significant synergistic reinforcing effect in rubber vulcanization systems. By combining a mercapto-isocyanate bifunctional cage-like silsesquioxane with an epoxy-terminated polysulfide, the former, with its nanocage-like structure, forms uniformly dispersed rigid nodes in the rubber matrix, effectively improving the material's modulus and dimensional stability. The latter, through the polysulfide bonds in its main chain, provides dynamic covalent crosslinking capability, undergoing reversible exchange under stress or thermal stimulation, endowing the vulcanizate with excellent stress relaxation and self-healing properties. Simultaneously, the epoxy-terminated structure ensures its full participation in the construction of the rubber vulcanization network, avoiding the poor compatibility or interfacial debonding problems caused by the inertness of the end groups in traditional polysulfide rubbers. Pre-dispersing and granulating both in a polybutadiene carrier significantly improves the processing and dispersibility of the nanofiller, preventing agglomeration, thereby achieving highly efficient reinforcement in the final product.

[0020] In terms of dynamic mechanical properties, this additive system integrates multiple energy dissipation mechanisms. The chemical bonding between the cage-like silsesquioxane and the rubber matrix enhances the interfacial bonding strength and inhibits the initiation of microcracks; while the dynamic breaking and recombination of polysulfide bonds absorbs and dissipates a large amount of energy during deformation, significantly improving the damping performance and fatigue life of the material. In addition, the zinc oxide introduced into the additive not only acts as a vulcanization activator but also forms weak interactions with potential polar groups in the system, which can further contribute non-covalent crosslinking points under dynamic loading, improving hysteresis loss and springback balance. Experiments show that the vulcanizate with this additive maintains high tensile strength while exhibiting lower compression set and better resistance to flexural cracking, making it particularly suitable for applications with stringent durability requirements such as tire sidewalls and shock absorber bearings.

[0021] From a processing and environmental perspective, the process conditions of this invention are mild, all raw materials are commercially available chemicals, and no special synthesis or high-risk operations are required. The photo-initiated end-capping reaction is carried out at room temperature, resulting in low energy consumption and few byproducts. Masterbatch preparation uses conventional twin-screw extrusion, which is fully compatible with existing rubber processing equipment. The terminal thiol liquid polysulfide rubber used is a commercially available product, ensuring batch stability. The final additives do not contain heavy metals or volatile organic solvents, conforming to the trend of green manufacturing. More importantly, the additives can be uniformly dispersed during the mixing stage without the need to extend the mixing time or increase the temperature, effectively protecting the molecular chain structure of natural rubber and avoiding the risk of early vulcanization. In summary, this invention not only solves the problems of traditional additives having single functions and difficult dispersion, but also achieves comprehensive optimization of rubber materials in terms of mechanical properties, dynamic response, and processing performance through molecular design and component synergy. Detailed Implementation

[0022] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0023] Example 1 Preparation of thiol-isocyanate difunctional cage-like silsesquioxanes: 20.0 g of octavinyl cage-like silsesquioxane and 6.8 g of 3-mercapto-1-propanol were added to a 250 mL three-necked flask equipped with a stirrer, reflux condenser, and nitrogen inlet tube. 100 mL of anhydrous tetrahydrofuran was added, and the mixture was stirred until completely dissolved. After purging with nitrogen for 15 min to replace the air, 0.14 g of azobisisobutyronitrile was added, and the mixture was heated to 78 °C and reacted under nitrogen protection for 5 h. The reaction solution was pale yellow and transparent, yielding a hydroxyl-partially functionalized POSS intermediate solution. This solution was transferred to another... In a dry three-necked flask, 5.2 g of isophorone diisocyanate and 50 mL of anhydrous tetrahydrofuran were added and stirred until dissolved. Then, 0.12 g of dibutyltin dilaurate was added. The mixture was reacted at 60 °C for 4 h under nitrogen protection. During the reaction, the viscosity of the system gradually increased, and a brownish-yellow reaction solution was obtained. The reaction solution was slowly poured into 500 mL of n-hexane pre-cooled to 0 °C, and a white flocculent precipitate was formed. After standing for 1 h, the precipitate was filtered. The filter cake was washed three times with 100 mL of n-hexane and dried in a vacuum drying oven at 40 °C for 27 h to obtain mercapto-isocyanate difunctional cage-type silsesquioxane.

[0024] Preparation of dynamically covalently bonded epoxy-terminated polysulfides: 50.0 g of mercapto-terminated liquid polysulfide rubber and 18.6 g of allyl glycidyl ether were added to a 250 mL three-necked flask equipped with a stirrer, a gas inlet tube, and a UV lamp irradiation window, and stirred until homogeneous. After purging with nitrogen for 15 min, 0.35 g of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide was added, and a 365 nm UV-LED light source (20 mW / cm²) was turned on. 2 The reaction mixture was irradiated at 30°C for 3 hours under nitrogen protection, and the reaction solution changed from light yellow to transparent amber. After irradiation, the reaction mixture was cooled to 25°C, transferred to a separatory funnel, and 100 mL of deionized water was added. The mixture was shaken and washed, allowed to stand for separation, and the aqueous phase was discarded. After washing with water three times, 5.0 g of anhydrous magnesium sulfate was added to the organic phase and dried for 2 hours. The desiccant was removed by filtration, and the residual solvent in the filtrate was removed by rotary evaporation at 40°C and -0.095 MPa to obtain a dynamically covalently bonded epoxy-terminated polysulfide.

[0025] Preparation of multifunctional rubber additive masterbatch: 40.0 g of polybutadiene and 2.0 g of stearic acid were added to a 500 mL emulsifier, heated to 100 °C, and stirred at 300 r / min for 10 min until uniformly melted; nitrogen gas was introduced for protection, and 15.0 g of the above-prepared mercapto-isocyanate difunctional cage-type silsesquioxane and 25.0 g of dynamically covalently bonded epoxy-terminated polysulfide were added sequentially, the temperature was raised to 120 °C, and stirred at 500 r / min for 30 min. To ensure uniform dispersion, 5.0 g of zinc oxide and 3.0 g of N-cyclohexyl-2-benzothiazole sulfenamide were added, and the mixture was cooled to 100°C and sheared and mixed at 800 r / min for 45 min to obtain a homogeneous viscous mixture. The mixture was then fed into a twin-screw extruder with the temperatures of each section set to 100°C, 110°C, 115°C, 115°C, and 110°C, and the screw speed set to 200 r / min. The extruded strip was then water-cooled and pelletized to obtain a multifunctional rubber additive masterbatch.

[0026] Preparation of vulcanized rubber: 100.0g of natural rubber, 50.0g of carbon black, 10.0g of silica, 10.0g of the above-mentioned multifunctional rubber additive masterbatch, 3.0g of zinc oxide, 2.0g of stearic acid, 2.0g of antioxidant 6PPD, and 6.0g of paraffin oil were added to a 1.5L internal mixer. The initial temperature was 75℃, the rotor speed was 60r / min, and the mixture was mixed until the discharge temperature reached 153℃. The mixture was then discharged and cooled to room temperature to obtain a compound. The compound was passed through a two-roll mill twice, and then 1.8g of sulfur and 1.2g of accelerator CBS were added. The mixture was mixed at 65℃ for 5 minutes and then passed through a sheet. The sheet was cut to the mold size and placed in a 150℃ flat vulcanizing machine. A pressure of 10MPa was applied, and the mixture was vulcanized for 20 minutes to obtain a vulcanized rubber sample.

[0027] Example 2 The specific implementation method is the same as in Example 1, except that the preparation of the mercapto-isocyanate difunctional cage-type silsesquioxane is as follows: 20.0 g of octavinyl cage-type silsesquioxane and 6.8 g of 3-mercapto-1-propanol are added to a 250 mL three-necked flask equipped with a stirrer, a reflux condenser, and a nitrogen inlet tube. 100 mL of anhydrous tetrahydrofuran is added, and the mixture is stirred until completely dissolved. After purging with nitrogen for 15 min to replace the air, 0.14 g of azobisisobutyronitrile is added, and the temperature is raised to 78 °C. The reaction is carried out under nitrogen protection for 5 h. The reaction solution is pale yellow and transparent, yielding a hydroxyl-partially functionalized POSS intermediate solution. The liquid was transferred to another dry three-necked flask, and 5.2 g of isophorone diisocyanate and 50 mL of anhydrous tetrahydrofuran were added. After stirring and dissolving, 0.12 g of dibutyltin dilaurate was added. The reaction was carried out at 60 °C for 4 h under nitrogen protection. During the reaction, the viscosity of the system gradually increased, and a brownish-yellow reaction solution was obtained. The reaction solution was slowly poured into 500 mL of n-hexane pre-cooled to 0 °C, and a white flocculent precipitate was formed. After standing for 1 h, the precipitate was filtered. The filter cake was washed three times with 100 mL of n-hexane and dried in a vacuum drying oven at 40 °C for 27 h to obtain 28.5 g of white powdered mercapto-isocyanate difunctional cage-type silsesquioxane.

[0028] Preparation of dynamically covalently bonded epoxy-terminated polysulfides: 50.0 g of mercapto-terminated liquid polysulfide rubber and 18.6 g of allyl glycidyl ether were added to a 250 mL three-necked flask equipped with a stirrer, a gas inlet tube, and a UV lamp irradiation window, and stirred until homogeneous. After purging with nitrogen for 15 min, 0.35 g of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide was added, and a 365 nm UV-LED light source (20 mW / cm²) was turned on. 2 The reaction mixture was irradiated at 30°C for 3 hours under nitrogen protection, and the reaction solution changed from light yellow to transparent amber. After irradiation, the reaction mixture was cooled to 25°C, transferred to a separatory funnel, and 100 mL of deionized water was added. The mixture was shaken and washed, allowed to stand for separation, and the aqueous phase was discarded. After washing with water three times, 5.0 g of anhydrous magnesium sulfate was added to the organic phase and dried for 2 hours. The desiccant was removed by filtration, and the residual solvent was removed by rotary evaporation at 40°C and -0.095 MPa to obtain 66.2 g of light yellow viscous liquid dynamically covalently bonded epoxy-terminated polysulfide.

[0029] Preparation of multifunctional rubber additive masterbatch: 38.0 g of polybutadiene and 1.0 g of stearic acid were added to a 500 mL emulsifier, heated to 98 °C, and stirred at 300 r / min for 10 min until uniformly melted; under nitrogen protection, 14.0 g of the above-prepared mercapto-isocyanate difunctional cage-type silsesquioxane and 24.0 g of dynamically covalently bonded epoxy-terminated polysulfide were added sequentially, the temperature was raised to 118 °C, and stirred at 500 r / min for 30 min until the mixture was homogeneous. The mixture was then evenly dispersed; subsequently, 4.0 g of zinc oxide and 2.0 g of N-cyclohexyl-2-benzothiazole sulfenamide were added, and the mixture was cooled to 98°C and sheared and mixed at 800 r / min for 30 min to obtain a homogeneous viscous mixture; the mixture was fed into a twin-screw extruder, with the temperatures of each section set to 95°C, 105°C, 110°C, 110°C, and 105°C, and the screw speed set to 200 r / min. The extruded strip was then water-cooled and pelletized to obtain grayish-white granular multifunctional rubber additive masterbatch.

[0030] Preparation of vulcanized rubber: 80.0g of natural rubber, 40.0g of carbon black, 0.0g of silica, 3.0g of the above-mentioned multifunctional rubber additive masterbatch, 2.0g of zinc oxide, 1.0g of stearic acid, 1.0g of antioxidant 6PPD, and 3.0g of paraffin oil were added to a 1.5L internal mixer. The initial temperature was 70℃, the rotor speed was 60r / min, and the mixture was mixed until the discharge temperature reached 150℃. The mixture was then discharged and cooled to room temperature to obtain a compound. The compound was passed through a two-roll mill twice, and then 1.0g of sulfur and 0.5g of accelerator CBS were added. The mixture was mixed at 60℃ for 5min and then passed through a sheet. The sheet was cut to the mold size and placed in a 150℃ flat vulcanizing machine. A pressure of 10MPa was applied, and the mixture was vulcanized for 20min to obtain a vulcanized rubber sample.

[0031] Example 3 The specific implementation method is the same as in Example 1, except that the preparation of the mercapto-isocyanate difunctional cage-type silsesquioxane is as follows: 20.0 g of octavinyl cage-type silsesquioxane and 6.8 g of 3-mercapto-1-propanol are added to a 250 mL three-necked flask equipped with a stirrer, a reflux condenser, and a nitrogen inlet tube. 100 mL of anhydrous tetrahydrofuran is added, and the mixture is stirred until completely dissolved. After purging with nitrogen for 15 min to replace the air, 0.14 g of azobisisobutyronitrile is added, and the temperature is raised to 78 °C. The reaction is carried out under nitrogen protection for 5 h. The reaction solution is pale yellow and transparent, yielding a hydroxyl-partially functionalized POSS intermediate solution. The liquid was transferred to another dry three-necked flask, and 5.2 g of isophorone diisocyanate and 50 mL of anhydrous tetrahydrofuran were added. After stirring and dissolving, 0.12 g of dibutyltin dilaurate was added. The reaction was carried out at 60 °C for 4 h under nitrogen protection. During the reaction, the viscosity of the system gradually increased, and a brownish-yellow reaction solution was obtained. The reaction solution was slowly poured into 500 mL of n-hexane pre-cooled to 0 °C, and a white flocculent precipitate was formed. After standing for 1 h, the precipitate was filtered. The filter cake was washed three times with 100 mL of n-hexane and dried in a vacuum drying oven at 40 °C for 27 h to obtain 28.5 g of white powdered mercapto-isocyanate difunctional cage-type silsesquioxane.

[0032] Preparation of dynamically covalently bonded epoxy-terminated polysulfides: 50.0 g of mercapto-terminated liquid polysulfide rubber and 18.6 g of allyl glycidyl ether were added to a 250 mL three-necked flask equipped with a stirrer, a gas inlet tube, and a UV lamp irradiation window, and stirred until homogeneous. After purging with nitrogen for 15 min, 0.35 g of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide was added, and a 365 nm UV-LED light source (20 mW / cm²) was turned on. 2 The reaction mixture was irradiated at 30°C for 3 hours under nitrogen protection, and the reaction solution changed from light yellow to transparent amber. After irradiation, the reaction mixture was cooled to 25°C, transferred to a separatory funnel, and 100 mL of deionized water was added. The mixture was shaken and washed, allowed to stand for separation, and the aqueous phase was discarded. After washing with water three times, 5.0 g of anhydrous magnesium sulfate was added to the organic phase and dried for 2 hours. The desiccant was removed by filtration, and the residual solvent was removed by rotary evaporation at 40°C and -0.095 MPa to obtain 66.2 g of light yellow viscous liquid dynamically covalently bonded epoxy-terminated polysulfide.

[0033] Preparation of multifunctional rubber additive masterbatch: 42.0 g of polybutadiene and 3.0 g of stearic acid were added to a 500 mL emulsifier and heated to 102 °C. The mixture was stirred at 300 r / min for 10 min until it melted uniformly. Nitrogen gas was introduced for protection. 16.0 g of the above-prepared mercapto-isocyanate difunctional cage-type silsesquioxane and 26.0 g of dynamically covalently bonded epoxy-terminated polysulfide were added sequentially. The mixture was heated to 122 °C and stirred at 500 r / min for 30 min to disperse the mixture. The mixture was then homogenized; subsequently, 6.0 g of zinc oxide and 4.0 g of N-cyclohexyl-2-benzothiazole sulfenamide were added, and the mixture was cooled to 102°C and sheared and mixed at 800 r / min for 60 min to obtain a homogeneous viscous mixture; the mixture was fed into a twin-screw extruder, with the temperatures of each section set to 105°C, 115°C, 120°C, 120°C, and 115°C, and the screw speed set to 200 r / min. The extruded strip was then water-cooled and pelletized to obtain grayish-white granular multifunctional rubber additive masterbatch.

[0034] Preparation of vulcanized rubber: 120.0g of natural rubber, 60.0g of carbon black, 20.0g of silica, 15.0g of the above-mentioned multifunctional rubber additive masterbatch, 5.0g of zinc oxide, 3.0g of stearic acid, 3.0g of antioxidant 6PPD, and 10.0g of paraffin oil were added to a 1.5L internal mixer. The initial temperature was 80℃, the rotor speed was 60r / min, and the mixture was mixed until the discharge temperature reached 155℃. The mixture was then discharged and cooled to room temperature to obtain a compound. The compound was passed through a two-roll mill twice, and then 2.5g of sulfur and 2.0g of accelerator CBS were added. The mixture was mixed at 70℃ for 5min and then passed through a sheet. The sheet was cut to the mold size and placed in a 150℃ flat vulcanizing machine. A pressure of 10MPa was applied, and the mixture was vulcanized for 20min to obtain a vulcanized rubber sample.

[0035] Comparative Example 1 The specific implementation method is the same as in Example 1, except that the multifunctional rubber additive masterbatch is prepared as follows: 40.0g of polybutadiene and 2.0g of stearic acid are added to an emulsifier, heated to 100°C, and stirred; under nitrogen protection, 5.0g of zinc oxide and 3.0g of N-cyclohexyl-2-benzothiazole sulfenamide are added, and shearing and mixing are continued at 100°C for 45min to obtain a mixture; the mixture is granulated at 115°C using a twin-screw extruder to obtain a rubber additive masterbatch that does not contain mercapto-isocyanate difunctional cage-type silsesquioxane and dynamically covalently bonded epoxy-terminated polysulfides.

[0036] Preparation of vulcanizate: 100.0g of natural rubber, 50.0g of carbon black, 10.0g of silica, 10.0g of the above-mentioned auxiliary masterbatch, 3.0g of zinc oxide, 2.0g of stearic acid, 2.0g of antioxidant 6PPD and 6.0g of paraffin oil were added to a mixer and mixed at an initial temperature of 75℃ until the discharge temperature reached 153℃. After discharge and cooling, a compound was obtained. The compound, 1.8g of sulfur and 1.2g of accelerator CBS were added to a two-roll mill and mixed at 65℃. The mixture was then sheeted and vulcanized at 150℃ for 20 minutes on a flat vulcanizing machine to obtain a vulcanizate sample.

[0037] Comparative Example 2 The specific implementation method is the same as in Example 1, except that the preparation of mercapto-isocyanate difunctional cage-type silsesquioxane is as follows: 28.5g was obtained by the same method as in Example 1.

[0038] Preparation of multifunctional rubber additive masterbatch: Add 40.0g of polybutadiene and 2.0g of stearic acid to an emulsifier, heat to 100℃, and stir; under nitrogen protection, add 15.0g of the above-mentioned mercapto-isocyanate difunctional cage-type silsesquioxane, heat to 120℃, and stir to mix; add 5.0g of zinc oxide and 3.0g of N-cyclohexyl-2-benzothiazole sulfenamide, and continue to shear and mix at 100℃ for 45min to obtain a mixture; granulate the mixture at 115℃ using a twin-screw extruder to obtain a rubber additive masterbatch without dynamically covalently bonded epoxy-terminated polysulfides.

[0039] Preparation of vulcanizate: The formulation and process are the same as in Example 1, and vulcanizate samples are obtained.

[0040] Comparative Example 3 The specific implementation method is the same as in Example 1, except that the dynamically covalently bonded epoxy-terminated polysulfide was prepared by the same method as in Example 1, yielding 66.2g.

[0041] Preparation of multifunctional rubber additive masterbatch: Add 40.0g of polybutadiene and 2.0g of stearic acid to an emulsifier, heat to 100℃, and stir; under nitrogen protection, add 25.0g of the above-mentioned dynamically covalently bonded epoxy-terminated polysulfide, heat to 120℃, and stir to mix; add 5.0g of zinc oxide and 3.0g of N-cyclohexyl-2-benzothiazole sulfenamide, and continue to shear and mix at 100℃ for 45min to obtain a mixture; granulate the mixture at 115℃ using a twin-screw extruder to obtain a rubber additive masterbatch without mercapto-isocyanate difunctional cage-type silsesquioxane.

[0042] Preparation of vulcanizate: The formulation and process are the same as in Example 1, and vulcanizate samples are obtained.

[0043] Performance testing The multifunctional rubber additives prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance testing according to the following method, which included the following steps: The vulcanized rubber samples prepared in Examples 1-3 and Comparative Examples 1-3 were tested after being placed in an environment of 23°C and 50% relative humidity for 24 hours. The tensile strength and elongation at break were measured using dumbbell-shaped Type I specimens on an electronic universal testing machine at a tensile rate of 500 mm / min. The results were taken as the arithmetic mean of 5 parallel specimens. Tear strength was measured using right-angled specimens at a tensile rate of 500 mm / min, and the unit is kN / m. The Shore A hardness is measured using a Shore A hardness tester, and the average value is taken after 5 measurements at different locations on the sample surface. The resilience was measured using a pendulum-type rebound tester. The device was dropped freely from 100% of the initial height, and the percentage of rebound height was recorded. The test temperature was 23℃, and the result was the average of 5 measurements. The compression set test used a cylindrical specimen (29 mm in diameter and 12.5 mm in height), which was compressed to 25% deformation in a 70℃ constant temperature chamber for 24 h, and then removed and allowed to recover at 23℃ for 30 min. The percentage of permanent deformation was calculated according to the formula. Dynamic mechanical properties were measured using a dynamic thermomechanical analyzer in tensile mode, with a frequency of 10 Hz, a strain amplitude of 0.1%, a temperature scan range of -60℃ to 80℃, and a heating rate of 3℃ / min. The loss factor tanδ values ​​at 0℃ and 60℃ were recorded respectively. For the heat aging performance test, the sample was placed in a 100℃ forced-air oven for 72 hours. After cooling, the tensile strength was measured according to the above tensile strength test method. The tensile strength retention rate was calculated by multiplying the ratio of the tensile strength after aging to the tensile strength before aging by 100%. The result was the average of 5 parallel samples.

[0044] Test results: Table 1: Test results of each embodiment and comparative example ; As can be seen from Table 1, Examples 1-3 show significant improvements in several key performance aspects compared to Comparative Examples 1-3, which fully demonstrates that the present invention effectively solves the technical problems of existing rubber additives, such as single function, poor dispersibility, insufficient dynamic performance and poor processing stability, by synergistically introducing mercapto-isocyanate bifunctional cage-type silsesquioxane and dynamic covalently bonded epoxy-terminated polysulfides. Specifically, the tensile strengths of Examples 1 to 3 reached 26.8-29.2 MPa, significantly higher than those of Comparative Example 1 (19.3 MPa), Comparative Example 2 (23.1 MPa), and Comparative Example 3 (22.7 MPa). This indicates that the combined effect of the two modified components can significantly enhance the load-bearing capacity of the rubber network. The cage-like siloxane provides a nano-reinforcing effect, while the epoxy-terminated polysulfide enhances interfacial bonding by participating in crosslinking. The simultaneous increase in tear strength and elongation at break demonstrates that the material possesses both high strength and high toughness, stemming from the dynamic reversibility of polysulfide bonds in crack propagation. During the process, energy is dissipated, inhibiting rapid crack propagation; the compression permanent deformation is reduced to 17.9-19.8%, far superior to the 32.6% of Comparative Example 1, demonstrating the excellent stress relaxation and structural recovery capabilities of the dynamic covalent network; the resilience is increased to 60-63%, while tanδ remains at a low level (0.120-0.132) at 0℃, indicating low rolling resistance, while at 60℃ tanδ increases to 0.278-0.292, reflecting good wet skid resistance, achieving a balance between low rolling resistance and high wet skid resistance, which is difficult to achieve with traditional additives; Furthermore, the Shore A hardness remained stable at 66-69 degrees, indicating that the filler was uniformly dispersed and there was no agglomeration during processing, verifying the pre-dispersion effect of the masterbatch process on the nano-components. The tensile strength retention rate after heat aging exceeded 90%, which was significantly better than the comparative example, indicating that the multiple cross-linking structure in the system improved the thermo-oxidative stability. Comparative examples 2 and 3, which lacked one of the modified components, had better performance than comparative example 1 (which contained no modified component), but were still significantly weaker than the example, proving that both functional components are indispensable and must work synergistically to achieve a balance of high strength, high damping, low permanent deformation, excellent dynamic mechanical properties, and good processing stability, thereby comprehensively overcoming the technical defects of existing rubber additives.

[0045] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for preparing a multifunctional rubber additive, characterized in that the steps include... include: S1. By weight, add 38-42 parts of polybutadiene and 1-3 parts of stearic acid to an emulsifier, heat to 98-102℃, and stir. Under nitrogen protection, add 14-16 parts of mercapto-isocyanate difunctional cage-type silsesquioxane and 24-26 parts of epoxy-terminated polysulfide in sequence, heat to 118-122℃, stir and mix, add 4-6 parts of zinc oxide and 2-4 parts of N-cyclohexyl-2-benzothiazole sulfenamide, and continue to shear and mix at 98-102℃ to obtain a mixture. Granulate the mixture through a twin-screw extruder at 110-120℃ to obtain a multifunctional rubber additive masterbatch. S2. In a mixing mill, add 80-120 parts of natural rubber, 40-60 parts of carbon black, 0-20 parts of silica, 3-15 parts of multifunctional rubber additive masterbatch, 2-5 parts of zinc oxide, 1-3 parts of stearic acid, 1-3 parts of antioxidant 6PPD, and 3-10 parts of paraffin oil and mix until the discharge temperature reaches 150-155℃. After discharge and cooling, a compound is obtained. In a two-roll mill, add the compound, 1-2.5 parts of sulfur, and 0.5-2 parts of accelerator CBS, mix at 60-70℃, sheet out in thin sheets, and vulcanize on a flat vulcanizing machine.

2. The preparation method of the multifunctional rubber additive according to claim 1, characterized in that, In step S1, the shearing and mixing time continues at 98-102℃ for 30-60 minutes.

3. The preparation method of the multifunctional rubber additive according to claim 1, characterized in that, In step S2, the initial temperature in the internal mixer is 70-80℃.

4. The preparation method of the multifunctional rubber additive according to claim 1, characterized in that, The method for preparing the mercapto-isocyanate difunctional cage-type silsesquioxane includes: A1. Octadecyl cage-type silsesquioxane and 3-mercapto-1-propanol are dissolved in anhydrous tetrahydrofuran, and azobisisobutyronitrile is added. The reaction is carried out under nitrogen protection at 75-80℃ to obtain a hydroxyl-functionalized POSS intermediate. The hydroxyl-functionalized POSS intermediate is dissolved in anhydrous tetrahydrofuran with isophorone diisocyanate, and dibutyltin dilaurate is added. An addition reaction is carried out under nitrogen protection at 58-62℃ to obtain a reaction solution. A2. Pour the reaction solution into cold n-hexane, filter, and obtain a precipitate. Wash the precipitate with n-hexane and dry it in a vacuum drying oven at 38-42℃.

5. The method for preparing the multifunctional rubber additive according to claim 4, characterized in that, In step A1, the reaction time is 4-6 hours under nitrogen protection and at 75-80℃.

6. The method for preparing the multifunctional rubber additive according to claim 4, characterized in that, In step A2, the drying time in a vacuum drying oven at 38-42℃ is 24-30 hours.

7. The method for preparing the multifunctional rubber additive according to claim 1, characterized in that, The preparation method of the dynamically covalently bonded epoxy-terminated polysulfide includes: B1. In a three-necked flask, add mercapto-terminated liquid polysulfide rubber and allyl glycidyl ether; add phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, and react under nitrogen protection, irradiated by a UV-LED light source, at 25-35°C to obtain a reaction mixture; B2. Cool the reaction mixture, wash with deionized water, and dry the organic phase with anhydrous magnesium sulfate and then rotary evaporate.

8. The method for preparing the multifunctional rubber additive according to claim 7, characterized in that, In step B1, the reaction time under UV-LED light source irradiation and at 25-35℃ is 2-4 hours; the terminal thiol liquid polysulfide rubber is ChloroL LP liquid polysulfide rubber.

9. The method for preparing the multifunctional rubber additive according to claim 7, characterized in that, In step B2, the reaction mixture is cooled to 24-26°C.

10. A multifunctional rubber additive, characterized in that, The multifunctional rubber additive is prepared by the method described in any one of claims 1-9.