Preparation method of modified insoluble sulfur, obtained product and application

Abstract

The invention discloses a preparation method of modified insoluble sulfur, an obtained product and application, the method is characterized in that insoluble sulfur powder and a modifier react to obtain the modified insoluble sulfur, and the modifier is 4, 4 '-(perfluoropropane-2, 2-diyl) bis (2-((4-aminopyridine-2-yl) amino) phenol). The high-temperature reversion resistance and thermal stability of the insoluble sulfur are improved, when the modified insoluble sulfur is used in rubber products such as tires, the vulcanization speed, the mechanical property and the bonding capacity of rubber materials can be improved, and the modified insoluble sulfur is suitable for high-performance tires and the field with higher requirements.

Description

Technical Field

[0001] This invention relates to a method for preparing modified insoluble sulfur, the resulting product, and its applications, belonging to the field of insoluble sulfur modification technology. Background Technology

[0002] Insoluble sulfur, also known as elastic sulfur or polymeric sulfur, is a highly polymerized allotrope and a modified variety of ordinary sulfur. As an important vulcanizing agent in the rubber industry, insoluble sulfur possesses excellent vulcanizing properties, improving the bonding strength between rubber compounds and reinforcing materials. Therefore, it is widely used in tire components and rubber products, such as tire carcasses, buffer layers, sidewalls, hoses, and belts, where high bonding strength with reinforcing materials is required. It can also be used in rubber compounds for cables, rubber rollers, rubber shoes, oil seals, and other light-colored rubber products with high sulfur content. With the improvement of road traffic and the development of the automotive industry, the ever-increasing vehicle speeds place higher demands on tires. Radial tires will replace ordinary bias-ply tires, becoming an inevitable trend in the tire industry. As the preferred rubber vulcanizing agent for radial tires, the demand for insoluble sulfur is increasing year by year. Although my country's insoluble sulfur technology has made significant progress through years of research and improvement, with production scale gradually expanding and product performance gradually improving, it still lacks competitiveness compared to high-performance foreign products. The performance of insoluble sulfur plays a crucial role in the application of products, significantly impacting the performance and lifespan of rubber products such as tires and wheels. Therefore, improving the performance of insoluble sulfur and narrowing the gap with superior products is of great importance. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing modified insoluble sulfur and the resulting product. This invention modifies insoluble sulfur with a modifier, thereby improving its resistance to reversion and thermal stability. Furthermore, the groups introduced in the modifier can also improve the sulfurization rate and mechanical properties of the rubber compound when applied to it, thus enhancing the overall performance of the rubber product. This allows insoluble sulfur to meet the requirements of high-performance tires and other fields with higher requirements.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing modified insoluble sulfur, characterized by comprising the step of reacting insoluble sulfur powder with a modifier to obtain modified insoluble sulfur, wherein the modifier is 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol); the structural formula of 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol is as follows: .

[0005] Furthermore, the preparation method of the modifier 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol) includes: A1. 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 2-bromo-4-nitropyridine were reacted in a strongly polar aprotic organic solvent to give 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-nitropyridine-2-yl)amino)phenol; A2. 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-nitropyridin-2-yl)amino)phenol was reduced under the action of hydrogen and a catalyst to obtain 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol). Furthermore, in step A1, the strongly polar aprotic organic solvent is N-methylpyrrolidone (NMP) or the like.

[0006] Further, in step A1, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 2-bromo-4-nitropyridine are respectively prepared into solutions using strongly polar aprotic organic solvents. Then, the 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane solution is added dropwise to the 2-bromo-4-nitropyridine solution to carry out the reaction. The temperature during the addition and reaction is less than or equal to 30°C, for example, 30°C, 25°C, 20°C, etc., and the addition time is 0.5-1 h. After the addition is complete, the reaction continues for 2-4 h.

[0007] Furthermore, in step A1, the molar ratio of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane to 2-bromo-4-nitropyridine is 1:2.03-2.10.

[0008] Furthermore, in step A1, the mass ratio of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane to a strongly polar aprotic organic solvent in the 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane solution is 1:2.0-3.0.

[0009] Furthermore, in step A1, the mass ratio of 2-bromo-4-nitropyridine to a strongly polar aprotic organic solvent in the 2-bromo-4-nitropyridine solution is 1:1.0-1.5.

[0010] Further, in step A1, after the reaction is complete, the reaction solution is added dropwise to the precipitate, causing precipitation. The precipitate is then separated, washed, and dried to obtain the intermediate 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-nitropyridin-2-yl)amino)phenol. The precipitate used is an aqueous ethanol solution with a concentration of 55-65 wt%, and the mass ratio of the precipitate to the reaction solution is 2-3:1. Drying is preferably vacuum drying at a temperature of 60-100℃ and a pressure of -0.090 to -0.095 MPa.

[0011] Further, in step A2, 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-nitropyridin-2-yl)amino)phenol is reacted in a strongly polar aprotic organic solvent. Preferably, the strongly polar aprotic organic solvent is at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-ethylpyrrolidone, and N-methylpyrrolidone. The amount of the strongly polar aprotic organic solvent used as the reaction medium is not particularly important.

[0012] Furthermore, the catalyst used in step A2 can be a commonly used catalyst for hydrogenation reactions, such as palladium-on-carbon or platinum-on-carbon catalysts. However, these precious metal catalysts are expensive, have long catalytic times, and their catalytic efficiency decreases significantly after repeated recycling, increasing production costs. This invention preferably provides a transition metal catalyst that is low in cost, highly selective, highly active, and exhibits excellent cycle stability. Its preparation method is as follows: a. Fluoride carbon nanofibers in a xenon difluoride (XeF2) atmosphere for 6-7 hours to obtain fluorinated carbon nanofiber (F-CNF) carriers; b. Dissolve nickel nitrate hexahydrate and ammonium molybdate tetrahydrate in water, then add fluorinated carbon nanofiber support to the resulting solution, impregnate and stir for 12-14 hours, then heat and stir to evaporate to dryness to obtain catalyst precursor; c. The catalyst precursor is first heated to 300-400℃ in an inert atmosphere and held for 1-2 hours, and then heated to 500-600℃ in an ammonia atmosphere and held for 2-4 hours to obtain the catalyst.

[0013] Furthermore, in step a, the carbon nanofibers can be prepared using existing technologies or purchased directly. The carbon nanofibers have a diameter of 50-200 nanometers and a length of 5-50 micrometers.

[0014] Furthermore, in step b, the molar ratio of molybdenum (Mo) to nickel (Ni) is 1:10 to 1:50, for example, 1:10, 1:20, 1:30, 1:40, or 1:50.

[0015] Furthermore, in step b, the mass ratio of nickel nitrate hexahydrate to fluorinated carbon nanofiber carrier is 0.9-1:1.

[0016] Furthermore, in step b, the temperature is raised to 70-90℃ and stirred to allow the solvent water to evaporate to dryness.

[0017] Furthermore, in step c, the inert atmosphere is provided by an inert gas such as argon.

[0018] Furthermore, in step c, the final catalyst consists of an active component and a support, wherein the active component is molybdenum-doped nickel nitride (Mo-Ni3N) nanosheets.

[0019] Furthermore, in step A2, the amount of catalyst used is 1-5 wt% of the mass of 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-nitropyridin-2-yl)amino)phenol.

[0020] Furthermore, in step A2, the reaction temperature is 60-80℃ and the hydrogen pressure is 0.5-1.5 MPa. When the hydrogen pressure is lower than 0.3 MPa, hydrogen is introduced again until the pressure is 0.5-1.5 MPa, and the reaction continues until the hydrogen pressure no longer changes.

[0021] Further, in step A2, after the reaction is complete, the reaction solution is cooled to room temperature and discharged, the catalyst is recovered, and the reaction solution is added dropwise to the precipitate to precipitate. The precipitate is separated, washed, and dried to obtain 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol). The precipitate used is a mixture of water, ethanol, and acetic acid, with a mass ratio of ethanol, acetic acid, and water of 28-32: 6-10: 60-65. The mass ratio of the precipitate to the reaction solution is 2-3:1. Drying is preferably performed under vacuum at a temperature of 60-100℃ and a pressure of -0.090 to -0.095 MPa.

[0022] Furthermore, the mass ratio of the modifier to the insoluble sulfur is 0.5-2:10, for example, 0.5:10, 1:10, 1.5:10, or 2:10.

[0023] Furthermore, the reaction between the modifier and the insoluble sulfur is carried out in a dispersion medium, preferably a mixture of toluene and n-butanol, which has high dispersion efficiency, good environmental friendliness, and is easy to recycle. Preferably, the volume ratio of toluene to n-butanol is 3-5:1.

[0024] Furthermore, the mass ratio of the dispersion medium to the insoluble sulfur powder is 1-7:1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1.

[0025] Furthermore, the reaction temperature between the modifier and the insoluble sulfur is 130-150℃, for example, 130℃, 135℃, 140℃, 145℃, 150℃.

[0026] Furthermore, the reaction time between the modifier and the insoluble sulfur powder is 15-30 minutes, for example, 15 minutes, 20 minutes, 25 minutes, or 30 minutes.

[0027] Furthermore, the modification reaction is preferably carried out under stirring, with the stirring speed preferably being 300-400 r / min.

[0028] Furthermore, after the modification reaction, the solvent is recovered by fractional vacuum distillation, and then the product is washed with water until neutral (to remove acidic byproducts) and then dried to obtain modified insoluble sulfur.

[0029] This invention uses 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol) to modify insoluble sulfur. The amino group (-NH2) in the modifier reacts with the surface of the insoluble sulfur to form sulfur-nitrogen crosslinks, enhancing the interfacial bonding. The modifier introduces a perfluoro-aminopyridinium hybrid structure, which improves the reversion resistance and thermal stability of the insoluble sulfur, and also increases the sulfurization rate of the rubber compound when added, thus improving the mechanical properties of the rubber product. This invention also protects the modified insoluble sulfur prepared according to the above method.

[0030] Furthermore, the present invention also provides the application of the above-mentioned modified insoluble sulfur in the preparation of rubber products, wherein the rubber products are products in which the raw materials contain rubber, such as tire carcasses, buffer layers, tire sidewalls, rubber hoses, etc.

[0031] This invention uses a modifier to modify insoluble sulfur powder, resulting in a comprehensive improvement in the application of the modified insoluble sulfur in rubber. Improvements are seen in vulcanization, physical and mechanical properties, and adhesion, solving problems such as low tensile strength, low retention after aging, and slow vulcanization speed associated with insoluble sulfur in rubber. This invention systematically enhances the overall performance of insoluble sulfur, making it suitable for high-performance tires and other demanding applications.

[0032] This invention has the following advantages: 1. This invention uses 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol) as a modifier to modify insoluble sulfur. This is the first time that the perfluoro-aminopyridine hybrid structure has been applied to the modification of insoluble sulfur, which solves the technical contradiction of synergistic improvement in vulcanization, physical and mechanical properties, and adhesion of rubber compounds. Its amino group (-NH2) reacts with the surface of insoluble sulfur to form sulfur-nitrogen crosslinks, which enhances the interfacial bonding force. The perfluoropropane structure has hydrophobicity and high temperature resistance (>200℃), which inhibits the high temperature reversion of insoluble sulfur and improves the high temperature reversion resistance and thermal stability of insoluble sulfur.

[0033] 2. The insoluble sulfur modification of this invention only requires the reaction of insoluble sulfur and modifier at a certain temperature. The operation is simple, the reaction is mild and not harsh, no high pressure is required, the equipment requirements are low, and the cost is low.

[0034] 3. When the modified insoluble sulfur obtained by this invention is used in rubber products such as tires, the pyridine group therein can synergistically activate the vulcanization reaction with zinc oxide in the rubber compound through coordination, thereby increasing the vulcanization rate of the rubber compound; through the synergistic effect of the fluoroaromatic structure and amino group in the modifier, the high temperature resistance and crosslinking density of the sulfur-rubber interface can be optimized, thereby improving the mechanical properties of the rubber products. Attached Figure Description

[0035] Figure 1 The NMR spectrum of 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol) is shown. Detailed Implementation

[0036] The technical solution of the present invention will be described in detail below through specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various modifications or alterations to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0037] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available products.

[0038] Preparation Example 1 A method for preparing 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol) includes the following steps: 1. Preparation of fluorinated carbon nanofibers (F-CNF): 1 g of polyacrylonitrile (PAN, Mw=150,000) was dissolved in 10 g of DMF and stirred until completely dissolved to obtain an electrospinning solution. PAN nanofiber membranes were obtained by electrospinning (voltage 15 kV, feed rate 0.5 mL / h, receiving distance 15 cm). The PAN nanofiber membranes were pre-oxidized in air at 250 °C for 2 hours. The pre-oxidized fiber membranes were transferred to a tube furnace and heated to 1000 °C at a rate of 5 °C / min under an argon atmosphere for 1 hour to obtain carbon nanofibers (CNF). After cooling to room temperature, CNF was fluorinated in a xenon difluoride (XeF2) atmosphere at room temperature for 6 hours to obtain fluorinated carbon nanofiber (F-CNF) carriers.

[0039] 2. Preparation of catalyst precursors: Weigh 0.95 g of nickel nitrate hexahydrate and 0.044 g of ammonium molybdate tetrahydrate, dissolve them in 50 mL of deionized water, and stir magnetically until completely dissolved; weigh 1.0 g of the F-CNF support prepared in step 1, disperse it in the above mixed metal salt solution, and impregnate and stir at room temperature for 12 hours; stir and evaporate the above mixture in an 80 °C water bath until dry to obtain the catalyst precursor.

[0040] 3. Heat treatment and nitriding: The catalyst precursor was placed in a tube furnace and heated to 350°C at a rate of 3°C / min under an argon atmosphere, and held at this temperature for 1 hour to remove residual water of crystallization and nitrate ions. Subsequently, the atmosphere was switched to high-purity ammonia (NH3), and the temperature was increased to 550°C at the same rate, and held at this temperature for 3 hours to carry out the nitriding reaction. After the reaction was completed, the product was naturally cooled to room temperature under an ammonia atmosphere. The resulting black solid product was taken out, ground, and the final catalyst Mo-Ni3N / F-CNF was obtained, with Mo-Ni3N loading in the catalyst being 18.9%.

[0041] 4. Add 100g (0.27mol) of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane to a beaker containing 230g NMP and stir until completely dissolved to obtain a 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane solution. 5. Add 113.48 g (0.559 mol) of 2-bromo-4-nitropyridine to a three-necked flask containing 113.48 g of NMP, stir well, and then cool to 20 °C to obtain a 2-bromo-4-nitropyridine solution. 6. A solution of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane was added dropwise to a three-necked flask using a peristaltic pump through a latex tube over a period of 0.5 h. The temperature was kept below 30 °C during the reaction. After the addition was complete, the temperature was adjusted to 25 °C, and the reaction continued for 4 h. Once the reaction was complete, the reaction solution was added dropwise to 2.5 times its mass of the precipitate (60 wt% ethanol solution). After the addition was complete, the mixture was stirred for 0.5 h, filtered, washed with pure water until neutral, and dried under vacuum at 85 °C and -0.095 MPa to obtain 161.1 g of pure 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-nitropyridin-2-yl)amino)phenol. The yield, based on 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, was 97.8%, and the product purity (HPLC) was 98.72%.

[0042] 7. Add 161.1 g of the substrate 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-nitropyridin-2-yl)amino)phenol to a beaker containing 1300 g of DMF, mix thoroughly until the solid is completely dissolved. Weigh 4.69 g of the Mo-Ni3N / F-CNF catalyst prepared in Example 1, and use the above small amount of substrate solution to adjust the catalyst into a slurry. Transfer the slurry to a hydrogenation reactor, and then transfer the remaining substrate solution to the reactor. Seal the reactor, replace the air in the reactor with hydrogen, start stirring, and purge with hydrogen to a pressure of 1.0 MPa. Raise the temperature to 70°C to start the reaction. Monitor the reaction pressure. When the hydrogen pressure drops below 0.5 MPa, purge with hydrogen again to 1.0 MPa. React for 13 minutes. After 0 min, the reaction pressure no longer decreased significantly. Heating and stirring were stopped, and the mixture was cooled to room temperature and depressurized. The reaction solution was drained, and the catalyst was separated and recovered by filtration. This catalyst could be used for the next batch of reaction. The mother liquor was added dropwise to 2.5 times its mass of the precipitate (ethanol:acetic acid:pure water mass ratio 30:8:62) using a peristaltic pump. After precipitation, the mixture was stirred for 0.5-1 h, filtered, washed with pure water, and dried at 85 °C under vacuum at -0.095 MPa to obtain 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol). The yield was 98.8% based on 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-nitropyridin-2-yl)amino)phenol, and the purity (HPLC) was 99.87%.

[0043] Preparation Example 2 A method for preparing 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol) includes the following steps: 1. Preparation of 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-nitropyridin-2-yl)amino)phenol intermediate: Same as in Preparation Example 1; 2. Add 161.1 g of the substrate 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-nitropyridin-2-yl)amino)phenol to a beaker containing 1300 g of DMF, mix thoroughly until the solid is completely dissolved. Weigh 4.69 g of palladium catalyst on carbon (5% palladium loading), and use the above small amount of substrate solution to prepare the catalyst into a slurry. Transfer the slurry to a hydrogenation reactor, and then transfer the remaining substrate solution to the reactor. Seal the reactor, purge the air inside with hydrogen, start stirring, and purge with hydrogen to a pressure of 1.0 MPa. Raise the temperature to 70°C to start the reaction. Monitor the reaction pressure; when the hydrogen pressure drops below 0.5 MPa, purge with hydrogen again to 1.0 MPa. After 6 hours of reaction, the reaction proceeds. Once the pressure no longer decreased significantly, heating and stirring were stopped, and the mixture was cooled to room temperature and depressurized. The reaction solution was drained, and the catalyst was separated and recovered by filtration. This catalyst could be used in the next batch of reaction. The mother liquor was added dropwise to 2.5 times its mass of the precipitate (ethanol:acetic acid:pure water mass ratio 30:8:62) using a peristaltic pump. After precipitation, the mixture was stirred for 0.5-1 h, filtered, washed with pure water, and dried at 85 °C under vacuum at -0.095 MPa to obtain 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol). The yield, based on 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-nitropyridin-2-yl)amino)phenol, was 98.4%, and the purity (HPLC) was 99.77%.

[0044] Example 1 A method for preparing modified insoluble sulfur includes the following steps: 1. Add 100g of insoluble sulfur powder and 15g of 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol) to a mixture of 500g toluene and n-butanol (volume ratio 3:1), stir and mix evenly, then heat to 140℃ and stir for 30min at a stirring speed of 300r / min; 2. The reaction solution from step 1 was subjected to vacuum distillation at a pressure of 50 kPa and a temperature of 60 °C to recover the solvent toluene. The reaction solution from step 1 was subjected to vacuum distillation at a pressure of 10 kPa and a temperature of 70 °C to recover n-butanol. After the solvent was recovered, deionized water was added to wash the sample until it was neutral. Then it was filtered and dried at 80 °C to obtain modified insoluble sulfur powder.

[0045] Example 2 A method for preparing modified insoluble sulfur includes the following steps: 1. Add 100g of insoluble sulfur powder and 10g of 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol) to a mixture of 500g toluene and n-butanol (volume ratio 3:1), stir and mix evenly, then heat to 140℃ and stir for 30min at a stirring speed of 300r / min; 2. Same as Example 1.

[0046] Example 3 A method for preparing modified insoluble sulfur includes the following steps: 1. Add 100g of insoluble sulfur powder and 5g of 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol) to a mixture of 500g toluene and n-butanol (volume ratio 3:1), stir and mix evenly, then heat to 140℃ and stir for 30min at a stirring speed of 300r / min; 2. Same as Example 1.

[0047] Example 4 A method for preparing modified insoluble sulfur includes the following steps: 1. Add 100g of insoluble sulfur powder and 15g of 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol) to a mixture of 500g toluene and n-butanol (volume ratio 3:1), stir and mix evenly, then heat to 130℃ and stir for 30min at a stirring speed of 400r / min; 2. Same as Example 1.

[0048] Comparative Example 1 Modified insoluble sulfur was prepared according to the method of Example 1, except that the modifier 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol) was replaced with an equal mass of p-aminoacetanilide.

[0049] Comparative Example 2 100g of insoluble sulfur powder and 15g of 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol) were mixed evenly to obtain a mixture of insoluble sulfur and modifier.

[0050] Application Example 1 The thermal stability of insoluble sulfur in the products of the above examples and comparative examples was tested according to the method described in GB / T18952. The results are shown in Table 1 below.

[0051] Table 1 Application Example 2 The modified insoluble sulfur obtained from the above examples and comparative examples were applied to the rubber compound, while unmodified insoluble sulfur powder was used as a control.

[0052] 1. The compound rubber formula is as follows: In the table above, the test samples are the modified insoluble sulfur samples and the unmodified insoluble sulfur powder samples prepared in each embodiment and comparative example.

[0053] 2. The preparation process of the compound rubber is as follows: First stage of intensive mixing: initial temperature 80℃, rotation speed 50rpm, add NR glue after 20s, mix with a roller for 60s, lift the roller for 10s and add ZnO-80, cobalt borate, antioxidant 4020, antioxidant RD, adhesive resin AR1005, carbon black N326, mix with a roller for 90s, clean in the middle for 10s, mix with a roller for 50s, repeat 3 times, and discharge the glue (total 390s).

[0054] Two-stage open mill: Adjust the roller gap of the open mill so that there is an appropriate amount of accumulated rubber above the open mill, then roll and mix for about 1 minute. Add HMMM-55 resin, accelerator DZ, and test sample. After the material is fully absorbed, cut the blades three times on each side and then produce the sheet. Adjust the roller gap of the open mill to the appropriate value, make 3 triangular wraps and 5 rolls, then adjust the roller gap and produce the sheet for testing.

[0055] 3. Performance Testing The vulcanization properties, mechanical properties, and adhesive properties of the obtained rubber compound were tested. Vulcanization properties were tested according to the methods described in GB / T16584-1996 using a rotorless vulcanizer at 151℃. Mechanical properties were tested according to the methods described in GB / T528-1998 and GB / T529-1999, with a tensile speed of 500 mm / min. Hardness was tested according to the methods described in GB / T531-1999. Adhesive properties were tested according to the methods described in GB / T 16586-1996.

[0056] 4. Experimental Results The performance test results of different rubber compounds are shown in Table 2-4 below.

[0057] 4.1 Vulcanization performance test results Table 2 As shown in Table 2, the modified insoluble sulfur compound prepared according to the embodiments of the present invention exhibits better vulcanization efficiency and crosslinking density than the comparative examples. This is because the modified insoluble sulfur samples incorporate amino, pyridine, and perfluoropropane groups through a modifier. The catalytic system formed by the amino and pyridine groups of the modifier lowers the activation energy of the vulcanization reaction. The synergistic effect of phenolic hydroxyl groups and aminopyridines allows for more uniform dispersion of the modified sulfur in the rubber, avoiding local over-vulcanization and significantly increasing the vulcanization rate. The perfluoropropane group possesses excellent thermal stability and reduces the surface tension of insoluble sulfur particles, greatly optimizing the crosslinking density of the rubber molecular chains. Among these, the tread rubber of Example 1 exhibits the best vulcanization effect.

[0058] 4.2 Mechanical property test results Table 3 As shown in Table 3, the tread rubber in each embodiment exhibits high tensile strength, good mechanical properties after aging, and high retention rate. The perfluorinated groups in the modifier reduce molecular chain slippage and inhibit free radical diffusion. The modified insoluble sulfur significantly improves the initial tensile strength, tensile strength after aging, and tensile strength retention rate of the tread rubber. The aminopyridine groups in the modifier can be balanced through hydrogen bonding, which is very helpful in controlling the elongation at break.

[0059] 4.3 Adhesion performance test results Table 4 As can be seen from Table 4, the initial adhesion, adhesion after thermo-oxidative aging, and adhesion retention rate of the tread rubber in each embodiment are all better than those in the comparative examples. The phenolic hydroxyl and amino groups in the modifier can form hydrogen bonds with the rubber matrix, which can greatly improve the peel strength between the rubber compound and the steel wire. The compatibility of the perfluoropropane segments can greatly improve the adhesion strength of the rubber compound.

[0060] The above tests show that using the modifier of this invention to modify insoluble sulfur can not only improve the resistance to reversion and thermal stability of insoluble sulfur, but also improve the vulcanization performance, mechanical properties and adhesion to metals such as steel wire of the rubber compound. It is suitable for high-performance tires, seals and fields with high requirements for aging resistance and adhesion performance.

Claims

1. A method for preparing modified insoluble sulfur, characterized in that: The process includes a step of reacting insoluble sulfur powder with a modifier to obtain modified insoluble sulfur, wherein the modifier is 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol).

2. The preparation method according to claim 1, characterized in that: The preparation methods of 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol) include: A1. 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 2-bromo-4-nitropyridine were reacted in a strongly polar aprotic organic solvent to give 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-nitropyridine-2-yl)amino)phenol; A2. 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-nitropyridin-2-yl)amino)phenol was reduced in the presence of hydrogen and a catalyst to obtain 4,4'-(perfluoropropane-2,2-diyl)bis(2-((4-aminopyridin-2-yl)amino)phenol).

3. The preparation method according to claim 1, characterized in that: The mass ratio of modifier to insoluble sulfur is 0.5-2:

10.

4. The preparation method according to claim 1, characterized in that: The reaction between the insoluble sulfur powder and the modifier is carried out in a dispersion medium, preferably a mixture of toluene and n-butanol, more preferably, the volume ratio of toluene to n-butanol is 3-5:

1.

5. The preparation method according to claim 4, characterized in that: The mass ratio of the dispersion medium to the insoluble sulfur powder is 1-7:

1.

6. The modified insoluble sulfur according to claim 1, characterized in that: The reaction temperature between the modifier and insoluble sulfur is 130-150℃.

7. The modified insoluble sulfur according to claim 1 or 6, characterized in that: The reaction time between the modifier and insoluble sulfur is 15-30 minutes.

8. The modified insoluble sulfur according to claim 1, characterized in that: The modification reaction is carried out under stirring, with the preferred stirring speed being 300-400 r / min.

9. Modified insoluble sulfur prepared according to the method for preparing modified insoluble sulfur according to any one of claims 1-8.

10. The use of the modified insoluble sulfur of claim 9 in the preparation of rubber products, wherein the rubber preparation includes tires.

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