Production process of modified p-phenylenediamine rubber antioxidant

Abstract

The invention discloses a production process of a modified p-phenylenediamine rubber anti-aging agent, which comprises the following steps: S1, catalyzing a ring-closure reaction through lipase, and accurately controlling pH by combining a phosphate buffer solution, so that the bonding efficiency of 6PPD and tea polyphenol is remarkably improved, and the release amount of aniline is effectively reduced; s2, carrying out spray drying to obtain EP-TP powder to control the particle morphology; s3, increasing the load rate of the anti-aging agent and effectively inhibiting the migration rate of the anti-aging agent through the pore diameter physical confinement of mesoporous silica and an amination gas phase modification technology, and ensuring uniform dispersion of anti-aging agent particles through the synergistic effect of staged load reaction and a polyethylene glycol dispersant; and S4, the particle morphology is cooperatively controlled through vacuum microwave drying, the dispersion requirement of the rubber mixing technology is met, and the interface bonding strength is improved by combining the staged loading reaction with a polyethylene glycol dispersing agent.

Description

Technical Field

[0001] The present invention relates to the technical field of antioxidant preparation, and specifically relates to a production process of modified p-phenylenediamine rubber antioxidants. Background Art

[0002] As an indispensable polymer material in the national economy and modern industry, the durability of rubber products directly determines the service life of key components such as tires, seals, and conveyor belts. However, during the processing, storage, and use of rubber, affected by factors such as heat, oxygen, mechanical stress, and ultraviolet light, the molecular chains are prone to breakage or cross-linking, resulting in material hardening, cracking, or loss of elasticity.

[0003] As the core additive for inhibiting rubber aging, antioxidants need to continuously function in a complex environment while meeting the dual constraints of environmental protection regulations and industrial costs. Currently, p-phenylenediamine compounds have become the most widely used type of antioxidants in the rubber industry due to their high free radical capture ability and peroxide decomposition activity. However, their molecular structure characteristics and traditional process routes have significant defects, restricting their application in rubber products.

[0004] Traditional p-phenylenediamine antioxidants face multiple performance bottlenecks in practical applications. Traditional antioxidants have a small molecule structure, limited compatibility with the rubber matrix, and are easily migrated to the material surface through molecular diffusion or volatilized by heat, resulting in a sharp decline in the protection efficiency over time and temperature. The migration of antioxidants not only reduces their own effectiveness but also forms a weak bonding area at the interface between rubber and filler, weakening the tear resistance and fatigue durability of the material. Summary of the Invention

[0005] The problems existing in the prior art are: traditional antioxidants have a small molecule structure, limited compatibility with the rubber matrix, are easily migrated to the material surface through molecular diffusion or volatilized by heat, and are prone to form a weak bonding area at the interface between rubber and filler, weakening the tear resistance and fatigue durability of the material. In view of the above technical problems, the present invention provides a production process of modified p-phenylenediamine rubber antioxidants.

[0006] The technical solution of the present invention is: a production process of modified p-phenylenediamine rubber antioxidants, comprising the following steps:

[0007] S1. By mass fraction, take 55 - 65 parts of 6PPD, 35 - 45 parts of tea polyphenols, 20 - 30 parts of epichlorohydrin, 2 - 3 parts of lipase, and 500 - 550 parts of deionized water; dissolve 6PPD and tea polyphenols in the deionized water at 55 - 65 °C, stir for 25 - 35 min, then add epichlorohydrin and lipase, under nitrogen protection, keep the temperature at 73 - 77 °C, and stir and react at a stirring rate of 200 - 250 rpm for 7 - 9 h to obtain a mixed solution, and separate the unreacted small molecule substances in the mixed solution with an ultrafiltration membrane to obtain a filtrate;

[0008] S2. Spray - dry the filtrate obtained in S1 to obtain EP - TP powder;

[0009] S3. By mass fraction, take 100 - 120 parts of the EP - TP powder obtained in S2, 150 - 170 parts of mesoporous silica, 30 - 40 parts of silane coupling agent KH - 550, and 1000 - 1200 parts of deionized water; mix and react mesoporous silica and silane coupling agent KH - 550 to obtain amino - functionalized mesoporous silica; disperse the EP - TP powder and the amino - functionalized mesoporous silica in deionized water, and carry out a loading reaction at a stirring rate of 280 - 320 rpm to obtain a slurry;

[0010] S4. Dehydrate the slurry obtained in S3 at a centrifugation rate of 3000 - 3500 rpm, control the mass moisture content of the slurry to be less than or equal to 15%, and then dry it in a vacuum microwave dryer at a temperature of 50 - 70 °C and a pressure of 0.085 - 0.095 MPa to obtain a composite antioxidant.

[0011] Note: Through molecular structure design and carrier confinement technology, the problem of the formation of a weak binding region at the interface between traditional p - phenylenediamine antioxidants and rubber and fillers is systematically solved; through the lipase - catalyzed ring - closing reaction, the aniline release path is blocked, and combined with the phosphate buffer system to stabilize the reaction conditions, the product purity is improved; the pore size matching and amino - functionalization modification technology of mesoporous silica realize the efficient loading and physical confinement of antioxidants, significantly reducing the migration rate, and the coupled process of spray drying and vacuum microwave drying realizes continuous production with low energy consumption and high powder fluidity.

[0012] Furthermore, the lipase in S1 is immobilized lipase Novozym 435 with a particle size of 0.3 - 0.9 mm.

[0013] Note: The particle size of immobilized lipase Novozym 435 is controlled within the range of 0.3 - 0.9 mm. By optimizing the physical size of the enzyme particles, the active center of the enzyme is fully exposed, while the mass transfer efficiency of the reaction system is improved, the contact resistance between the enzyme and the reactants is reduced, and the catalytic efficiency is enhanced.

[0014] Furthermore, the particle size of the EP-TP powder is 20 - 40 μm; the pore diameter of the mesoporous silica is 7 - 9 nm, and the particle size is 100 - 200 mesh.

[0015] Note: The particle size of the EP-TP powder is controlled within the range of 20 - 40 μm, which is adapted to the dispersion requirements of the rubber mixing process to avoid processing difficulties caused by too large particles; the pore diameter of 7 - 9 nm of the mesoporous silica matches the molecular size of EP-TP, reducing the migration of the antioxidant through physical confinement, and the particle size of 100 - 200 mesh optimizes the slurry fluidity and subsequent drying efficiency.

[0016] Furthermore, during the stirring reaction in S1, the pH of the reaction system is controlled to be 6.8 - 7.2.

[0017] Note: The phosphate buffer solution is used to maintain the stability of the pH of the reaction system, prevent the inactivation of lipase due to acid-base fluctuations, and at the same time inhibit the occurrence of side reactions, ensuring the efficient bonding of 6PPD and tea polyphenols and improving the product purity.

[0018] Furthermore, the cut-off molecular weight of the ultrafiltration membrane in S1 is 10 kDa.

[0019] Note: An ultrafiltration membrane with a cut-off molecular weight of 10 kDa is used to effectively separate unreacted epichlorohydrin and small molecule by-products, reduce the interference of impurities on the subsequent process, and improve the performance stability of the antioxidant.

[0020] Furthermore, in S2, in the spray drying, the inlet temperature is set to 170 - 190 °C, and the outlet temperature is set to 75 - 85 °C.

[0021] Note: The temperature control drying strategy rapidly evaporates water through high inlet temperature, and the low outlet temperature avoids the degradation of heat-sensitive tea polyphenols, ensuring the integrity and fluidity of the particle morphology of the EP-TP powder and adapting to the requirements of industrial production.

[0022] Furthermore, in S3, the method of mixing and reacting mesoporous silica with the silane coupling agent KH-550 to obtain amino-functionalized mesoporous silica is as follows: The mesoporous silica is ultrasonically treated in 5% hydrochloric acid at 40 kHz for 30 min to remove surface impurities; by gas-phase polymerization, the steam of the silane coupling agent KH-550 is permeated into the interior of the mesoporous silica under vacuum conditions, the reaction temperature is 120 - 130 °C, and the reaction time is 1 - 1.5 h to obtain amino-functionalized mesoporous silica.

[0023] Note: Hydrochloric acid ultrasonic cleaning is used to remove the surface impurities of the mesoporous surface, and gas-phase polymerization is used to make the KH-550 steam penetrate deep into the pore channels for reaction, improving the uniformity and density of amino modification and avoiding the influence of solvent residues on the performance of the carrier.

[0024] Further, the load reaction described in S3 is as follows: First, stir and react at 65 - 75 °C for 3.5 - 4.5 h, then add 0.1 - 0.3 parts by mass of polyethylene glycol, and finally stir and react at 75 - 95 °C for 7 - 9 h to obtain a slurry.

[0025] Note: Temperature control in stages combined with polyethylene glycol dispersant promotes the stable loading of EP-TP molecules on the surface of the carrier through dual mechanisms of physical adsorption and chemical bonding, reduces particle agglomeration, and improves the loading efficiency.

[0026] Further, after the centrifugal dehydration described in S4, 1 - 2 wt% of nano-aerosil is uniformly added to the slurry.

[0027] Note: Adding nano-aerosil as a drying aid, utilizing its high specific surface area and dispersibility, prevents particle adhesion, and optimizes the drying efficiency and particle fluidity.

[0028] The beneficial effects of the present invention are as follows:

[0029] The present invention catalyzes the ring-closing reaction through immobilized lipase Novozym 435, combines precise pH control with phosphate buffer solution, significantly improves the bonding efficiency of 6PPD and tea polyphenols, and effectively reduces the aniline release amount; through the physical confinement of the pore size of mesoporous silica and the amino-functionalized gas-phase modification technology, the antioxidant loading rate is improved, and the migration rate of the antioxidant is effectively inhibited. Through the synergistic effect of the staged loading reaction and polyethylene glycol dispersant, it ensures the uniform dispersion of antioxidant particles. By using spray drying and vacuum microwave drying to synergistically control the particle morphology, it adapts to the dispersion requirements of the rubber mixing process. The staged loading reaction combined with polyethylene glycol dispersant inhibits particle agglomeration and improves the interfacial bonding strength. The present invention provides a long-lasting, stable, and environmentally friendly antioxidant solution for rubber products, which is applicable to high-demand fields such as tires and seals. Brief Description of the Drawings

[0030] Figure 1 It is a line graph showing the aniline release amount test of the samples in Examples 1 - 23 of the present invention;

[0031] Figure 2 It is a line graph showing the aniline release amount test of the samples in Comparative Examples 1 - 4 of the present invention;

[0032] Figure 3 It is a line graph showing the antioxidant migration rate test of the samples in Examples 1 - 23 of the present invention at 70 °C for 72 h;

[0033] Figure 4 It is a line graph showing the antioxidant migration rate test of the samples in Comparative Examples 1 - 4 of the present invention at 70 °C for 72 h;

[0034] Figure 5It is a line graph of the tensile strength retention rate test of the samples in Examples 1 to 23 of the present invention at 100 °C for 1000 h.

[0035] Figure 6 It is a line graph of the tensile strength retention rate test of the samples in Comparative Examples 1 to 4 of the present invention at 100 °C for 1000 h. Detailed implementation manners

[0036] To further elaborate on the methods adopted and the effects achieved by the present invention, the technical solutions of the present invention will be clearly and completely described below in combination with experiments.

[0037] Example 1:

[0038] A production process of a modified p-phenylenediamine rubber antioxidant includes the following steps:

[0039] S1. By mass, take 60 parts of 6PPD, 40 parts of tea polyphenols, 25 parts of epichlorohydrin, 2.5 parts of lipase, and 525 parts of deionized water; dissolve 6PPD and tea polyphenols in the deionized water at 60 °C, stir for 30 min, then add epichlorohydrin and lipase, under nitrogen protection, keep the temperature at 75 °C, stir and react at a stirring rate of 225 rpm for 8 h, use phosphate buffer to control the pH of the stirring reaction system to 7 to obtain a mixed solution, and separate the unreacted small molecules in the mixed solution with an ultrafiltration membrane to obtain a filtrate; the lipase is immobilized lipase Novozym 435 with a particle size of 0.5 - 0.6 mm; the cut-off molecular weight of the ultrafiltration membrane is 10 kDa;

[0040] S2. Spray-dry the filtrate obtained in S1, set the inlet temperature to 180 °C and the outlet temperature to 80 °C to obtain EP-TP powder; the particle size of the EP-TP powder is 30 - 32 μm;

[0041] S3. By mass fraction, take 110 parts of the EP-TP powder described in S2, 160 parts of mesoporous silica, 35 parts of silane coupling agent KH-550, and 1100 parts of deionized water; subject the mesoporous silica to ultrasonic treatment at 40 kHz for 30 min in hydrochloric acid with a mass concentration of 5% to remove surface impurities; using gas-phase polymerization method, permeate the vapor of silane coupling agent KH-550 into the interior of the mesoporous silica under vacuum conditions, with a reaction temperature of 125 °C and a reaction time of 1.25 h to obtain amino-functionalized mesoporous silica; disperse the EP-TP powder and the amino-functionalized mesoporous silica in deionized water, and carry out a loading reaction at a stirring rate of 300 rpm. First, stir and react at 70 °C for 4 h, then add 0.2 parts by mass of polyethylene glycol, and finally stir and react at 85 °C for 8 h to obtain a slurry; the pore diameter of the mesoporous silica is 7.2 - 8.5 nm, and the particle size is 150 mesh;

[0042] S4. Dehydrate the slurry described in S3 at a centrifugation rate of 3250 rpm, uniformly add nano-aerosil accounting for 1.5 wt% of the slurry to the slurry, control the mass moisture content of the slurry to be 10%, and then dry it in a vacuum microwave dryer at a temperature of 60 °C and a pressure of 0.09 MPa to obtain a composite antioxidant;

[0043] The application method of the composite antioxidant is as follows:

[0044] By mass fraction, take 5.5 parts of the antioxidant described in S4, 125 parts of natural rubber, 45 parts of white carbon black, 2.5 parts of silane coupling agent Si-69, and 2 parts of sulfur;

[0045] Add natural rubber, white carbon black, and silane coupling agent Si-69 to an internal mixer, and mix at 65 °C and a rotation speed of 60 rpm for 5 min to obtain a uniform pre-dispersion;

[0046] Add the composite particles to the pre-dispersion in three equal portions, with an interval of 1.5 min each time, and then mix at 85 °C for 8.5 min; finally, add sulfur and continue to mix for 3.5 min, then calender the rubber compound into sheets, and fully vulcanize and mold it at a temperature of 160 °C and a pressure of 15 MPa to obtain a vulcanized rubber sheet.

[0047] Example 2: This example is basically the same as Example 1, except that, by mass fraction, take 55 parts of 6PPD, 35 parts of tea polyphenols, 20 parts of epichlorohydrin, 2 parts of lipase, and 500 parts of deionized water.

[0048] Example 3: This example is basically the same as Example 1, except that, by mass fraction, take 65 parts of 6PPD, 45 parts of tea polyphenols, 30 parts of epichlorohydrin, 3 parts of lipase, and 550 parts of deionized water.

[0049] Example 4: This example is basically the same as Example 1, except that 6PPD and tea polyphenols are dissolved in the deionized water at 55 °C, stirred for 25 min, and then epichlorohydrin and lipase are added. Under nitrogen protection, the temperature is maintained at 73 °C, and the mixture is stirred and reacted at a stirring rate of 200 rpm for 7 h to obtain a mixed solution. The unreacted small-molecule substances in the mixed solution are separated by an ultrafiltration membrane to obtain a filtrate.

[0050] Example 5: This example is basically the same as Example 1, except that 6PPD and tea polyphenols are dissolved in the deionized water at 65 °C, stirred for 35 min, and then epichlorohydrin and lipase are added. Under nitrogen protection, the temperature is maintained at 77 °C, and the mixture is stirred and reacted at a stirring rate of 250 rpm for 9 h to obtain a mixed solution. The unreacted small-molecule substances in the mixed solution are separated by an ultrafiltration membrane to obtain a filtrate.

[0051] Example 6: This example is basically the same as Example 1, except that by mass, 100 parts of the EP-TP powder described in S2, 150 parts of mesoporous silica, 30 parts of silane coupling agent KH-550, and 1000 parts of deionized water are taken.

[0052] Example 7: This example is basically the same as Example 1, except that by mass, 120 parts of the EP-TP powder described in S2, 170 parts of mesoporous silica, 40 parts of silane coupling agent KH-550, and 1200 parts of deionized water are taken.

[0053] Example 8: This example is basically the same as Example 1, except that the EP-TP powder and the aminated mesoporous silica are dispersed in deionized water, and a loading reaction is carried out at a stirring rate of 280 rpm to obtain a slurry; the slurry is dehydrated at a centrifugation rate of 3000 rpm, and the mass moisture content of the slurry is controlled to be 8%. Subsequently, it is dried in a vacuum microwave dryer at a temperature of 50 °C and a pressure of 0.085 MPa to obtain a composite antioxidant.

[0054] Example 9: This example is basically the same as Example 1, except that the EP-TP powder and the aminated mesoporous silica are dispersed in deionized water, and a loading reaction is carried out at a stirring rate of 320 rpm to obtain a slurry; the slurry is dehydrated at a centrifugation rate of 3500 rpm, and the mass moisture content of the slurry is controlled to be 15%. Subsequently, it is dried in a vacuum microwave dryer at a temperature of 70 °C and a pressure of 0.095 MPa to obtain a composite antioxidant.

[0055] Example 10: This example is basically the same as Example 1, except that the lipase described in S1 is immobilized lipase Novozym 435 with a particle size of 0.3 - 0.4 mm.

[0056] Example 11: This example is basically the same as Example 1, except that the lipase described in S1 is immobilized lipase Novozym 435 with a particle size of 0.8 - 0.9 mm.

[0057] Example 12: This example is basically the same as Example 1, except that the particle size of the EP-TP powder is 20 - 25 μm; the pore diameter of the mesoporous silica is 7 - 7.5 nm, and the particle size is 100 mesh.

[0058] Example 13: This example is basically the same as Example 1, except that the particle size of the EP-TP powder is 35 - 40 μm; the pore diameter of the mesoporous silica is 8.2 - 9 nm, and the particle size is 200 mesh.

[0059] Example 14: This example is basically the same as Example 1, except that during the stirring reaction in S1, the pH of the reaction system is controlled to be 6.8.

[0060] Example 15: This example is basically the same as Example 1, except that during the stirring reaction in S1, the pH of the reaction system is controlled to be 7.2.

[0061] Example 16: This example is basically the same as Example 1, except that in the spray drying described in S2, the inlet temperature is set to 170 °C and the outlet temperature is set to 75 °C.

[0062] Example 17: This example is basically the same as Example 1, except that in the spray drying described in S2, the inlet temperature is set to 190 °C and the outlet temperature is set to 85 °C.

[0063] Example 18: This example is basically the same as Example 1, except that in S3, the method for mixing and reacting mesoporous silica with silane coupling agent KH-550 to obtain amino-functionalized mesoporous silica is as follows: The mesoporous silica is ultrasonically treated in 5% hydrochloric acid with a frequency of 40 kHz for 30 min to remove surface impurities; by gas phase polymerization method, the vapor of silane coupling agent KH-550 is permeated into the interior of the mesoporous silica under vacuum conditions, the reaction temperature is 120 °C, and the reaction time is 1 h to obtain amino-functionalized mesoporous silica.

[0064] Example 19: This example is basically the same as Example 1, except that in S3, the method of mixing and reacting mesoporous silica with silane coupling agent KH-550 to obtain amino-functionalized mesoporous silica is as follows: Mesoporous silica is ultrasonically treated in 5% hydrochloric acid by mass concentration at 40 kHz for 30 min to remove surface impurities; by gas-phase polymerization method, the vapor of silane coupling agent KH-550 is permeated into the interior of mesoporous silica under vacuum conditions, the reaction temperature is 130 °C, and the reaction time is 1.5 h to obtain amino-functionalized mesoporous silica.

[0065] Example 20: This example is basically the same as Example 1, except that the loading reaction in S3 is as follows: First, stir and react at 65 °C for 3.5 h, then add 0.1 part by mass of polyethylene glycol, and finally stir and react at 75 °C for 7 h to obtain a slurry.

[0066] Example 21: This example is basically the same as Example 1, except that the loading reaction in S3 is as follows: First, stir and react at 75 °C for 4.5 h, then add 0.3 part by mass of polyethylene glycol, and finally stir and react at 95 °C for 9 h to obtain a slurry.

[0067] Example 22: This example is basically the same as Example 1, except that after centrifugal dehydration in S4, 1 wt% of nano-aerosil is uniformly added to the slurry.

[0068] Example 23: This example is basically the same as Example 1, except that after centrifugal dehydration in S4, 2 wt% of nano-aerosil is uniformly added to the slurry.

[0069] Comparative Example 1: Taking Example 1 as a reference, by mass parts, 50 parts of 6PPD, 30 parts of tea polyphenols, 10 parts of epichlorohydrin, 1 part of lipase, and 400 parts of deionized water are taken.

[0070] Comparative Example 2: Taking Example 1 as a reference, by mass parts, 130 parts of the EP-TP powder described in S2, 180 parts of mesoporous silica, 50 parts of silane coupling agent KH-550, and 1300 parts of deionized water are taken.

[0071] Comparative Example 3: Taking Example 1 as a reference, the particle size of the EP-TP powder is 50 - 55 μm; the pore diameter of the mesoporous silica is 6 - 7 nm, and the particle size is 300 mesh.

[0072] Comparative Example 4: Taking Example 1 as a reference, the particle size of the EP-TP powder is 15 - 18 μm; the pore diameter of the mesoporous silica is 9 - 10 nm, and the particle size is 90 mesh.

[0073] To explore the anti-aging agent performance of some embodiments and control examples, the main materials were determined according to the experimental formula and samples were obtained for testing. The results are as Figures 1-6 shown. The specific exploration is as follows:

[0074] 1. Explore the influence of raw material ratio parameters on the performance of the anti-aging agent:

[0075] As Figures 1-6 shown, by comparing Examples 1, 2, 3, 6, and 7, it can be seen that Example 7 has the lowest aniline release amount, the lowest migration rate, and the highest tensile strength retention rate. It can be seen that an EP-TP increment of 20% can enhance the loading efficiency. In Example 6, with a 10% reduction in EP-TP, it led to uneven dispersion of the anti-aging agent and a decline in performance. Example 6 has the highest aniline release amount and migration rate, and the lowest tensile strength retention rate; the aniline release amount and migration rate of Example 3 are lower than those of Example 2 and slightly lower than those of Example 1, and the tensile strength retention rate is higher than that of Example 2 and slightly higher than that of Example 1. It can be seen that increasing the dosages of 6PPD, tea polyphenols, and epichlorohydrin makes the reaction more complete.

[0076] 2. Explore the influence of material particle size matching on the performance of the anti-aging agent

[0077] As Figures 1-6 shown, Example 1 uses a lipase particle size of 0.5 - 0.6 mm, an EP-TP particle size of 30 - 32 μm, and a mesoporous pore diameter of 7.2 - 8.5 nm, with an aniline release amount of 0.018 ppm and a migration rate of 0.07%, and the performance is optimal; after the lipase particle size of Examples 10 and 11 deviates from 0.5 - 0.6 mm, the aniline release amounts increase to 0.028 ppm and 0.030 ppm respectively, indicating that too small or too large particle sizes both reduce the catalytic efficiency. In Example 12, the EP-TP particle size is reduced to 20 - 25 μm and the mesoporous pore diameter is 7 - 7.5 nm, and the migration rate increases to 0.10%; in Example 13, the EP-TP particle size is increased to 35 - 40 μm and the mesoporous pore diameter is 8.2 - 9 nm, and the migration rate increases to 0.09%, proving that size mismatch weakens the confinement effect.

[0078] 3. Explore the influence of reaction temperature and pH on the performance of the anti-aging agent

[0079] As Figures 1-6As shown, in Example 1, the reaction was carried out at 75°C and pH 7.0, the aniline release amount was 0.018 ppm, and the tensile strength retention rate was 89.5%; in Example 4, the temperature was lowered to 73°C and the pH was not controlled, the aniline release amount increased to 0.022 ppm, and the retention rate decreased to 84%; in Example 5, the temperature was raised to 77°C, the aniline release amount further decreased to 0.016 ppm, and the retention rate increased to 91.5%, indicating that a moderate temperature increase can improve the efficiency. After the pH of Example 14 was lowered to 6.8, the aniline release amount increased to 0.025 ppm, and the retention rate decreased to 79%; in Example 15, the pH was raised to 7.2, the aniline release amount remained 0.018 ppm but the retention rate decreased to 86%, indicating that precise pH control is crucial for suppressing side reactions.

[0080] 4. Explore the influence of the loading process on the performance of the antioxidant

[0081] As Figures 1-6 shown, Example 1 adopted a staged loading process of 70°C adsorption + 85°C anchoring and added 0.2 parts of polyethylene glycol, the migration rate was 0.07%, and the tensile strength retention rate was 89.5%; in Example 20, the loading temperature was lowered to 65°C and only 0.1 part of polyethylene glycol was added, the migration rate increased to 0.17%, and the retention rate decreased to 74%, indicating insufficient low-temperature loading; in Example 21, the loading temperature was raised to 95°C and 0.3 parts of polyethylene glycol were added, the migration rate decreased to 0.09% but the retention rate slightly decreased to 87.5%. After adjusting the centrifugation rate in Examples 22 and 23, the migration rates increased to 0.11% and 0.1% respectively, and the retention rates decreased to 81% and 82%, verifying that the centrifugation rate needs to match the loading process.

[0082] 5. Explore the influence of centrifugation and drying parameters on the performance of the antioxidant

[0083] As Figures 1-6 shown, Example 1 was centrifuged at 3250 rpm and dried at 60°C and 0.09 MPa. After testing, the bulk density of the particles was 0.6 g / cm 3 , and the fluidity was 25 s / 50 g; in Example 8, the centrifugation rate was lowered to 3000 rpm and the drying temperature was lowered to 50°C, the moisture content of the particles increased, the aniline release amount was slightly higher than that of Example 1, the migration rate increased to 0.12%, and the retention rate decreased to 80%; in Example 9, the centrifugation rate was increased to 3500 rpm and the drying temperature was raised to 70°C, the particle breakage rate increased, and the retention rate decreased to 88%; after the centrifugation rates of Examples 22 and 23 deviated by ±10%, both the bulk density and the fluidity decreased, indicating that the dehydration efficiency and particle integrity need to be optimized through parameter balance.

Claims

1. A production process of a modified p-phenylenediamine rubber antioxidant, characterized in that: The following steps are involved: S1. Take 55-65 parts of 6PPD, 35-45 parts of tea polyphenols, 20-30 parts of epichlorohydrin, 2-3 parts of lipase, and 500-550 parts of deionized water by mass; dissolve 6PPD and tea polyphenols in the deionized water at 55-65° C., stir for 25-35 minutes, then add epichlorohydrin and lipase, and under nitrogen protection, keep the temperature at 73-77° C., stir at a stirring rate of 200-250 rpm for 7-9 hours to obtain a mixed solution, and separate the unreacted small molecules in the mixed solution with an ultrafiltration membrane to obtain a filtrate; S2, spray drying the filtrate described in S1 to obtain EP-TP powder; S3, taking 100-120 parts of the EP-TP powder described in S2, 150-170 parts of mesoporous silica, 30-40 parts of silane coupling agent KH-550, and 1000-1200 parts of deionized water by mass; mixing the mesoporous silica and the silane coupling agent KH-550 to obtain amino mesoporous silica; dispersing the EP-TP powder and the amino mesoporous silica in deionized water, and carrying out a loading reaction at a stirring rate of 280-320 rpm to obtain a slurry; S4, dehydrating the slurry described in S3 at a centrifugal rate of 3000-3500rpm, controlling the mass moisture content of the slurry to be less than or equal to 15%, and then drying it in a vacuum microwave dryer at a temperature of 50-70°C and a pressure of 0.085-0.095MPa to obtain a composite antioxidant.

2. The production process of a modified p-phenylenediamine rubber antioxidant according to claim 1, characterized in that: The lipase in S1 is immobilized lipase Novozym 435 with a particle size of 0.3-0.9 mm.

3. The production process of a modified p-phenylenediamine rubber antioxidant according to claim 1, characterized in that: The particle size of the EP-TP powder is 20-40 μm; the pore size of the mesoporous silica is 7-9 nm, and the particle size is 100-200 mesh.

4. The production process of a modified p-phenylenediamine rubber antioxidant according to claim 1, characterized in that: During the stirring reaction in S1, the pH of the reaction system is controlled to be 6.8-7.

2.

5. The production process of a modified p-phenylenediamine rubber antioxidant according to claim 1, characterized in that: The molecular weight cut-off of the ultrafiltration membrane described in S1 is 10 kDa.

6. The production process of a modified p-phenylenediamine rubber antioxidant according to claim 1, characterized in that: In the spray drying described in S2, the inlet temperature is set to 170-190°C, and the outlet temperature is set to 75-85°C.

7. The production process of a modified p-phenylenediamine rubber antioxidant according to claim 1, characterized in that: In S3, the method of mixing mesoporous silica with silane coupling agent KH-550 to obtain amino-modified mesoporous silica is as follows: ultrasonically treating the mesoporous silica in 5% hydrochloric acid at 40kHz for 30 minutes to remove surface impurities; and using a gas phase polymerization method to infiltrate the silane coupling agent KH-550 vapor into the interior of the mesoporous silica under vacuum conditions, with a reaction temperature of 120-130°C and a reaction time of 1-1.5 hours to obtain amino-modified mesoporous silica.

8. The production process of a modified p-phenylenediamine rubber antioxidant according to claim 1, characterized in that: The loading reaction described in S3 is: first stirring the reaction at 65-75°C for 3.5-4.5h, then adding 0.1-0.3 mass fraction of polyethylene glycol, and finally stirring the reaction at 75-95°C for 7-9h to obtain a slurry.

9. The production process of a modified p-phenylenediamine rubber antioxidant according to claim 1, characterized in that: After the centrifugal dehydration described in S4, 1-2 wt% of nano-fumed silica is uniformly added to the slurry.

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