Anti-caking composite rubber antioxidant 6PPD and preparation method thereof

Abstract

The invention belongs to the technical field of rubber anti-aging agents, and particularly relates to an anti-caking composite rubber anti-aging agent 6PPD and a preparation method thereof. The invention relates to an anti-caking composite rubber anti-aging agent 6PPD, which is prepared by the following steps: reacting 3-amino adipic acid with 4-pentenyl isothiocyanate, grafting to silicon dioxide through a silane coupling agent, complexing with lanthanum ions to obtain a functional anti-aging agent, and reacting the functional anti-aging agent with a basic anti-aging agent N-(1, 2, 4-trimethyl-1, 3-pentenyl)-1, 2, 4-trimethyl-1, 3-pentenyl isothiocyanate to obtain the anti The anti-caking composite rubber anti-aging agent 6PPD is prepared by compounding 2, 3-dimethylbutyl)-N '-phenyl p-phenylenediamine, microcrystalline wax and an antioxidant. The prepared anti-caking composite rubber anti-aging agent 6PPD has the characteristics of multiple protection of chemical protection, physical barrier and multi-mechanism synergy, excellent aging resistance, good processability, caking prevention and easiness in storage.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber antioxidants, and in particular relates to an anti-caking composite rubber antioxidant 6PPD and a preparation method thereof. Background Art

[0002] Rubber is a highly elastic polymer material with reversible deformation. Its low glass transition temperature and excellent elasticity at room temperature make it widely used in transportation, aerospace, defense, and everyday life. However, the numerous isolated unsaturated double bonds and reactive allylic hydrogen groups found in most rubber molecular chains make rubber products highly susceptible to attack by heat, oxygen, ozone, light, and stress, leading to performance degradation, or aging. Adding antioxidants is the most convenient and effective way to prevent rubber aging. Among them, the aromatic amine antioxidant 6PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) dominates the market due to its excellent aging protection. However, due to its small molecular weight, 6PPD still presents volatilization and migration issues. Its poor thermal stability, extraction resistance, and migration resistance significantly reduce its aging protection capabilities. Furthermore, due to its small molecular weight, low melting point, and the presence of polar groups, 6PPD is prone to agglomeration during production, transportation, and use.

[0003] Chinese patent CN114044897A discloses a method for preparing the antioxidant 6PPD. Cashew nut shell liquid is used as a raw material, and high-temperature decarboxylation and distillation are performed to obtain cardanol. Cardanol and a haloalkyl are then synthesized to obtain a corresponding ether product. The ether product reacts with the antioxidant 6PPD to produce a macromolecular antioxidant containing a cardanol structure. This overcomes the shortcomings of existing antioxidants such as easy migration in rubber products, easy extraction in water and solvents, and easy agglomeration at high temperatures. By making the antioxidant 6PPD macromolecular and multifunctional, it effectively improves the antioxidant's resistance to migration and extraction, low toxicity, and compatibility. The antioxidant is safe, stable, and long-lasting, with good application prospects. Chinese patent CN112143026A discloses a modified rubber antioxidant, a composition containing the same, and its preparation and application. The long-chain epoxy compound raw material is grafted with a compound with the structure of a traditional p-phenylenediamine antioxidant to obtain a high-molecular-weight antioxidant with better protective effects and better migration resistance. However, using only a single-ingredient antioxidant can easily lead to problems such as poor protective performance, short protective time, and high cost. Summary of the Invention

[0004] In view of the above problems, the present invention proposes an anti-caking composite rubber antioxidant 6PPD and a preparation method thereof, which effectively solves the problem of poor performance of a single antioxidant.

[0005] In the first aspect, the present invention provides an anti-caking composite rubber antioxidant 6PPD, the scheme is as follows:

[0006] The invention discloses an anti-caking composite rubber antioxidant 6PPD, which comprises the following raw materials in parts by weight: 20-30 parts of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 80-100 parts of a functional antioxidant, 15-20 parts of microcrystalline wax, and 2-4 parts of an antioxidant.

[0007] Furthermore, the antioxidant is a thioester antioxidant.

[0008] Furthermore, the functional antioxidant is prepared by the following steps: S1, reacting 3-aminoadipic acid with a sodium hydroxide solution to prepare a 3-aminoadipic acid salt solution; S2, dropping an ethanol solution of 4-pentenyl isothiocyanate into the 3-aminoadipic acid salt solution, heating and stirring to react, and purifying to obtain an intermediate 1; S3, dissolving the intermediate 1 and a silane coupling agent in DMF, adding triethylamine, heating and stirring to react, and obtaining an intermediate 2 solution; S4, dispersing silicon dioxide in an ethanol aqueous solution, adjusting the pH to 10-11, ultrasonically dispersing the silicon dioxide, dropping the intermediate 2 solution under an inert gas atmosphere, heating to react, and purifying to obtain an intermediate 3; S5, dropping an aqueous solution of lanthanum chloride into the dispersion of the intermediate 3 under heating, stirring to react, and purifying to obtain a functional antioxidant.

[0009] Furthermore, the molar ratio of 3-aminoadipic acid to sodium hydroxide is 1:(2.1-2.3).

[0010] Furthermore, the molar ratio of 3-aminoadipate to 4-pentenyl isothiocyanate is 1:(1-1.2).

[0011] Furthermore, the silane coupling agent is one of KH-590, KH-580, KH-581, and KH-582.

[0012] Furthermore, the molar ratio of the intermediate 1, the silane coupling agent, and the triethylamine is 1:(1.2-1.5):(0.3-0.5).

[0013] Furthermore, the mass ratio of silicon dioxide to intermediate 1 is 100:(10-20).

[0014] Furthermore, the molar ratio of lanthanum chloride to intermediate 3 is (1.5-2):1.

[0015] In a second aspect, the present invention provides a method for preparing an anti-caking composite rubber antioxidant 6PPD, comprising the following steps: (1) heating and melting microcrystalline wax to liquefy it; (2) adding N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, a functional antioxidant, and an antioxidant in batches, and stirring and mixing until the system has no agglomerated particles; (3) transferring to a high-shear emulsifier to further form a uniformly dispersed system; and (4) extruding through a twin-screw extruder, water-cooling, and pelletizing to obtain the anti-caking composite rubber antioxidant 6PPD.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention compounds a functional antioxidant with a basic antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, microcrystalline wax and an antioxidant to prepare an anti-caking composite rubber antioxidant 6PPD. The anti-caking composite rubber antioxidant 6PPD has multiple protections of "chemical protection-physical barrier-multi-mechanism synergy", has excellent anti-aging performance, good processability, anti-caking and easy storage.

[0018] The functional antioxidant prepared by the present invention possesses multiple functional groups, including a thiourea structure, a lanthanum ion complex, and coupled grafted silica. The thiourea structure effectively decomposes the macromolecular hydroperoxide ROOH generated in the styrene-butadiene rubber (SBR) molecular chain due to thermo-oxidative aging in the form of thiols. Sulfur-containing free radicals terminate active free radicals such as R· and ROO·, and sulfur oxides further decompose ROOH. The lanthanum ion can passivate and terminate active oxygen-containing free radicals ROO·, RO·, and HO·, thereby terminating the SBR thermo-oxidative aging reaction. Grafting a silane coupling agent onto silica enhances its dispersibility, migration resistance, and extraction resistance. N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine reacts with free radicals generated by rubber oxidation, consuming initial oxidation products. However, these products are prone to loss over time due to migration and volatilization. The functional antioxidant can reduce the loss of 6PPD and extend its duration of action. Microcrystalline wax forms a physical barrier to form a wax film on the rubber surface. Antioxidants can form a eutectic structure with the wax, thereby improving the density of the wax film and isolating oxygen and ozone from contacting the rubber. When the wax film is damaged, the protection gap can be filled by the chemical protection of functional antioxidants, together forming a multi-level protection system of "free radical scavenging-peroxide decomposition-metal ion passivation". BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a preparation roadmap for functional antioxidants.

[0020] Figure 2 This is the infrared spectrum of the functional antioxidant.

[0021] Figure 3 The vulcanization curve of the rubber compound containing different antioxidants.

[0022] Figure 4 The aging performance test diagram of vulcanized rubber containing different antioxidants, where (a) is the tensile strength retention rate, (b) is the elongation at break retention rate, and (c) is the aging coefficient.

[0023] Figure 5 These are cross-sectional SEM images of vulcanized rubber containing different antioxidants, where (a) is the blank group, (b) is comparative example 1, (c) is comparative example 3, (d) is comparative example 2, and (e) is embodiment 1. DETAILED DESCRIPTION

[0024] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] Example 1

[0026] The invention discloses an anti-caking composite rubber antioxidant 6PPD, which comprises the following raw materials in parts by weight: 20 kg of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 80 kg of a functional antioxidant, 15 kg of microcrystalline wax, and 2 kg of an antioxidant.

[0027] The antioxidant in this embodiment is dilauryl thiodipropionate.

[0028] The functional antioxidant of this embodiment is prepared by the following steps ( Figure 1 shown):

[0029] S1. Mix 1 mol of 3-aminoadipic acid with a sodium hydroxide solution, raise the temperature to 50° C., and react for 30 minutes to prepare a 3-aminoadipate solution; the molar ratio of 3-aminoadipic acid to sodium hydroxide is 1:2.1; and the concentration of the sodium hydroxide solution is 2.5 mol / L.

[0030] S2. Add the ethanol solution of 4-pentenyl isothiocyanate dropwise to 100 mL of 3-aminoadipate solution, stir and react at 50°C for 5 h, cool to room temperature, extract with ether, collect the lower layer solution, add about 0.5 g of hydroquinone to the lower layer solution, and then remove the solvent by rotary evaporation under reduced pressure. The crude product is centrifuged and washed with anhydrous ethanol, and then dried in vacuo at 55°C to obtain intermediate 1; the molar ratio of 3-aminoadipate to 4-pentenyl isothiocyanate is 1:1, and the concentration of the ethanol solution of 4-pentenyl isothiocyanate is 6.5 mol / L.

[0031] S3, under nitrogen protection, 15 g of intermediate 1 and a silane coupling agent were dissolved in 1.5 L of DMF, triethylamine was added, and the mixture was heated to 45° C. and stirred for 4 h to obtain an intermediate 2 solution; the molar ratio of intermediate 1, silane coupling agent, and triethylamine was 1:1.2:0.3; the silane coupling agent was KH-590.

[0032] S4, 100 g of silica was dispersed in 1 L of ethanol aqueous solution, ammonia was added dropwise to adjust the pH to 10, ultrasonic treatment was performed for 2 h, and the intermediate 2 solution was added dropwise at 45°C under an inert gas atmosphere. The mixture was stirred and reacted for 4 h, cooled to room temperature, and the solvent was removed by centrifugation. The unreacted silane coupling agent was washed with tetrahydrofuran and then vacuum dried at 45°C to obtain intermediate 3; the mass ratio of silica to intermediate 1 was 100:10; the volume ratio of alcohol to water in the ethanol aqueous solution was 4:1.

[0033] S5, at 50°C, add the aqueous solution of lanthanum chloride dropwise to the dispersion of intermediate 3, stir and react for 6 hours, cool to room temperature, filter, wash the filter residue with water, and vacuum dry at 50°C to obtain a functional antioxidant; the molar ratio of lanthanum chloride to intermediate 3 is 1.5:1; the concentration of the aqueous solution of lanthanum chloride is 0.5 mol / L; the dispersion of intermediate 3 is obtained by ultrasonically dispersing intermediate 3 and water at a ratio of 1 g:10 mL.

[0034] The prepared functional antioxidant was tested by infrared spectrometer. The results are as follows: Figure 2 As shown. Figure 2 It can be seen that: 468cm -1 , 780cm -1 and 1042cm -1 The asymmetric absorption peak of Si-O-Si group appeared at 1550cm -1 、1480cm -1 The characteristic absorption peaks of thiourea of NCN and NC=S appeared at 1742 cm -1 、1428cm -1 Carboxylates C=O and COO appear -1 The symmetrical contraction vibration absorption peak is due to the existence of monodentate coordination and bidentate chelation between the carboxyl group and the metal lanthanum, so there is still some C=O; 3341cm -1 A large peak appeared at , which may be due to the mixing of the stretching vibration absorption peaks of NH on thiourea and bound water OH. The above characteristic peaks prove that the target product was successfully prepared.

[0035] Example 2

[0036] The invention discloses an anti-caking composite rubber antioxidant 6PPD, which comprises the following raw materials in parts by weight: 25 kg of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 90 kg of a functional antioxidant, 18 kg of microcrystalline wax, and 3 kg of an antioxidant.

[0037] The antioxidant in this embodiment is distearyl thiodipropionate.

[0038] The functional antioxidant of this embodiment is prepared by the following steps:

[0039] S1. Mix 1 mol of 3-aminoadipic acid with a sodium hydroxide solution, raise the temperature to 525° C., and react for 35 minutes to prepare a 3-aminoadipate solution; the molar ratio of 3-aminoadipic acid to sodium hydroxide is 1:2.2; and the concentration of the sodium hydroxide solution is 2.5 mol / L.

[0040] S2, adding the ethanol solution of 4-pentenyl isothiocyanate dropwise to 100 mL of 3-aminoadipate solution, stirring and reacting at 55°C for 6 h, cooling to room temperature, extracting with ether, collecting the lower layer solution, adding about 0.5 g of hydroquinone to the lower layer solution, and then removing the solvent by rotary evaporation under reduced pressure. The crude product was centrifuged and washed with anhydrous ethanol, and then dried in vacuo at 55°C to obtain intermediate 1; the molar ratio of 3-aminoadipate to 4-pentenyl isothiocyanate was 1:1.1, and the concentration of the ethanol solution of 4-pentenyl isothiocyanate was 6.5 mol / L.

[0041] S3, under nitrogen protection, 20 g of intermediate 1 and a silane coupling agent were dissolved in 1.5 L of DMF, triethylamine was added, and the mixture was heated to 48° C. and stirred for 4.5 h to obtain an intermediate 2 solution; the molar ratio of intermediate 1, silane coupling agent, and triethylamine was 1:1.3:0.4; the silane coupling agent was KH-580.

[0042] S4, 100 g of silica was dispersed in 1 L of ethanol aqueous solution, ammonia was added dropwise to adjust the pH to 11, ultrasonic treatment was performed for 2.5 h, and the intermediate 2 solution was added dropwise at 48° C. under an inert gas atmosphere. The mixture was stirred and reacted for 4.5 h. The mixture was cooled to room temperature and the solvent was removed by centrifugation. The unreacted silane coupling agent was washed with tetrahydrofuran and then vacuum dried at 45° C. to obtain intermediate 3; the mass ratio of silica to intermediate 1 was 100:15; the volume ratio of alcohol to water in the ethanol aqueous solution was 4:1.

[0043] S5, at 55°C, add the aqueous solution of lanthanum chloride dropwise to the dispersion of intermediate 3, stir and react for 7 hours, cool to room temperature, filter, wash the filter residue with water, and vacuum dry at 50°C to obtain a functional antioxidant; the molar ratio of lanthanum chloride to intermediate 3 is 1.8:1; the concentration of the aqueous solution of lanthanum chloride is 0.5 mol / L; the dispersion of intermediate 3 is obtained by ultrasonically dispersing intermediate 3 and water at a ratio of 1 g:10 mL.

[0044] Example 3

[0045] The invention discloses an anti-caking composite rubber antioxidant 6PPD, which comprises the following raw materials in parts by weight: 30 kg of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 100 kg of a functional antioxidant, 20 kg of microcrystalline wax, and 4 kg of an antioxidant.

[0046] In this embodiment, the antioxidant is 2,2'-thiobis(4-methyl-6-tert-butylphenol).

[0047] The functional antioxidant of this embodiment is prepared by the following steps:

[0048] S1. Mix 1 mol of 3-aminoadipic acid with a sodium hydroxide solution, raise the temperature to 55° C., and react for 40 minutes to prepare a 3-aminoadipate solution; the molar ratio of 3-aminoadipic acid to sodium hydroxide is 1:2.2; and the concentration of the sodium hydroxide solution is 2.5 mol / L.

[0049] S2, adding the ethanol solution of 4-pentenyl isothiocyanate dropwise to 100 mL of 3-aminoadipate solution, stirring and reacting at 60°C for 7 h, cooling to room temperature, extracting with ether, collecting the lower layer solution, adding about 0.5 g of hydroquinone to the lower layer solution, and then removing the solvent by rotary evaporation under reduced pressure. The crude product was centrifuged and washed with anhydrous ethanol, and then dried in vacuo at 55°C to obtain intermediate 1; the molar ratio of 3-aminoadipate to 4-pentenyl isothiocyanate was 1:1.2, and the concentration of the ethanol solution of 4-pentenyl isothiocyanate was 6.5 mol / L.

[0050] S3, under nitrogen protection, 25 g of intermediate 1 and a silane coupling agent were dissolved in 1.5 L of DMF, triethylamine was added, and the mixture was heated to 50° C. and stirred for 5 h to obtain an intermediate 2 solution; the molar ratio of intermediate 1, silane coupling agent, and triethylamine was 1:1.5:0.5; the silane coupling agent was KH-581.

[0051] S4, 100 g of silica was dispersed in 1 L of ethanol aqueous solution, ammonia was added dropwise to adjust the pH to 11, and ultrasonic treatment was performed for 3 h. Under an inert gas atmosphere, the intermediate 2 solution was added dropwise at 50° C., and the mixture was stirred and reacted for 5 h. The mixture was cooled to room temperature, and the solvent was removed by centrifugation. The unreacted silane coupling agent was washed with tetrahydrofuran, and then vacuum dried at 45° C. to obtain intermediate 3; the mass ratio of silica to intermediate 1 was 100:20; the volume ratio of alcohol to water in the ethanol aqueous solution was 4:1.

[0052] S5, at 60°C, add the aqueous solution of lanthanum chloride dropwise to the dispersion of intermediate 3, stir and react for 8 hours, cool to room temperature, filter, wash the filter residue with water, and vacuum dry at 50°C to obtain a functional antioxidant; the molar ratio of lanthanum chloride to intermediate 3 is 2:1; the concentration of the aqueous solution of lanthanum chloride is 0.5 mol / L; the dispersion of intermediate 3 is obtained by ultrasonically dispersing intermediate 3 and water at a ratio of 1 g:10 mL.

[0053] A method for preparing an anti-caking composite rubber antioxidant 6PPD comprises the following steps: (1) heating and melting microcrystalline wax to liquefy it; (2) adding N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, a functional antioxidant and an antioxidant in batches, and stirring and mixing until the system has no agglomerated particles; (3) transferring the mixture to a high-shear emulsifier to further form a uniformly dispersed system; and (4) extruding the mixture through a twin-screw extruder, water-cooling and pelletizing the mixture to obtain the anti-caking composite rubber antioxidant 6PPD.

[0054] Comparative Example 1

[0055] The same as Example 1, except that no functional antioxidant is added in the preparation of the anti-caking composite rubber antioxidant 6PPD.

[0056] Comparative Example 2

[0057] The same as Example 1, except that intermediate 3 is directly used instead of the functional antioxidant to participate in the preparation of the anti-caking composite rubber antioxidant 6PPD.

[0058] Comparative Example 3

[0059] The same as Example 1, except that: the functional antioxidant is prepared by the following steps: S1, mixing 1 mol of 3-aminoadipic acid with a sodium hydroxide solution, heating to 50° C., and reacting for 30 minutes to prepare a 3-aminoadipate solution; the molar ratio of 3-aminoadipic acid to sodium hydroxide is 1:2.1; and the concentration of the sodium hydroxide solution is 2.5 mol / L.

[0060] S2. Add the ethanol solution of 4-pentenyl isothiocyanate dropwise to 100 mL of 3-aminoadipate solution, stir and react at 50°C for 5 h, cool to room temperature, extract with ether, collect the lower layer solution, add about 0.5 g of hydroquinone to the lower layer solution, and then remove the solvent by rotary evaporation under reduced pressure. The crude product is centrifuged and washed with anhydrous ethanol, and then dried in vacuo at 55°C to obtain intermediate 1; the molar ratio of 3-aminoadipate to 4-pentenyl isothiocyanate is 1:1, and the concentration of the ethanol solution of 4-pentenyl isothiocyanate is 6.5 mol / L.

[0061] S3, at 50°C, add the aqueous solution of lanthanum chloride dropwise to the dispersion of intermediate 1, stir and react for 6 hours, cool to room temperature, filter, wash the filter residue with water, and vacuum dry at 50°C to obtain a functional antioxidant; the molar ratio of lanthanum chloride to intermediate 1 is 1.5:1; the concentration of the aqueous solution of lanthanum chloride is 0.5 mol / L; the dispersion of intermediate 1 is obtained by ultrasonically dispersing intermediate 1 and water at a ratio of 1 g:10 mL.

[0062] 1. Referring to the standard GB / T16584-1996, a rotorless vulcanizer was used to test the vulcanization performance of the blank group and the styrene-butadiene rubber compound containing the antioxidant prepared in Example 1 and Comparative Examples 1 to 3. The test temperature was 158°C, the frequency was 1.66Hz, and the swing angle was ±1°. The components and weight amounts of each group are shown in Table 1 (“-” means no addition, SA is stearic acid, NS is N-tert-butyl-2-benzothiazole sulfonamide, DM is 2,2'benzothiazole disulfide, and S is sulfur). The preparation method of the styrene-butadiene rubber compound is as follows: first, the styrene-butadiene rubber is plasticized on a two-roll mill, and then SiO2, ZnO / SA, NS / DM, antioxidant and sulfur are added in sequence and mixed for 15 minutes to obtain the styrene-butadiene rubber compound. The measured vulcanization curve is as follows: Figure 3 shown.

[0063] Table 1. Components and dosage of each group of styrene-butadiene rubber compound

[0064] Styrene-butadiene rubber <![CDATA[SiO2]]> ZnO / SA NS / DM S Antioxidants Example 1 100 - 5 / 2 2 / 0.6 2 35 Comparative Example 1 100 32 5 / 2 2 / 0.6 2 3 Comparative Example 2 100 - 5 / 2 2 / 0.6 2 35 Comparative Example 3 100 32 5 / 2 2 / 0.6 2 3 Blank group 100 32 5 / 2 2 / 0.6 2 -

[0065] from Figure 3 As can be seen, compared to the blank control rubber mix without antioxidant, the addition of antioxidants prepared in Example 1 and Comparative Examples 1 to 3 significantly shortens the vulcanization time of the rubber mix, increases the maximum torque and torque difference, and promotes the vulcanization effect. Among them, Example 1 has the best improvement in the vulcanization effect, followed by Comparative Example 3 > Comparative Example 2 > Comparative Example 1 > Blank control.

[0066] Preparation of rubber vulcanizate: According to the preparation method and the amount of components of styrene-butadiene rubber compound (the amount of components of styrene-butadiene rubber compound in Example 2 and Example 3 is the same as that in Example 1), a blank group and styrene-butadiene rubber compound containing the antioxidant prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were prepared, and then the styrene-butadiene rubber compound was vulcanized on a flat vulcanizer at 158°C, 12 MPa, t 90 The rubber vulcanizate was vulcanized at 400 °C for 2 min and then used for the following tests.

[0067] 2. In accordance with standard ASTM D412-15a, the blank group and the rubber vulcanizates containing the antioxidants prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were cut into dumbbell-shaped rubber vulcanizate specimens. The mechanical properties of the rubber vulcanizate specimens were tested using a universal testing machine at a tensile rate of 300 mm / min. Five specimens were used for each test, and the average value was taken as the final test result.

[0068] 3. Withdrawal resistance

[0069] The blank group and the rubber vulcanizates containing the antioxidants prepared in Examples 1-3 and Comparative Examples 1-3 were cut into dumbbell-shaped rubber vulcanizate strips. The rubber vulcanizate strips were extracted in a Soxhlet extractor using methanol as the solvent. After 48 hours of extraction, the strips were removed and dried in a vacuum drying oven at 65°C to constant weight. The antioxidant's resistance to methanol extraction was evaluated based on the mass loss of the strips before and after extraction. The mass loss rate (%) = (m1-m2) / m1×100%, where m1 and m2 are the masses of the strips before and after extraction, respectively. The results are shown in Table 2:

[0070] Table 2. Performance test results

[0071] Tensile strength (MPa) Stress at 100% strain (MPa) Stress at 300% strain (MPa) Elongation at break (%) Mass loss rate (%) Example 1 20.8 2.13 12.13 415 2.83 Example 2 20.6 2.13 12.12 418 2.85 Example 3 20.5 2.14 12.15 419 2.86 Comparative Example 1 17.8 1.93 8.38 381 3.76 Comparative Example 2 19.7 2.10 11.68 410 3.03 Comparative Example 3 18.9 2.04 10.31 387 3.42 Blank group 15.8 2.01 8.72 402 2.70

[0072] As can be seen from Table 2, compared with the blank group and comparative examples 1 to 3, the rubber vulcanized rubber strips to which the antioxidant prepared in the present application is added have the best mechanical properties and strong extraction resistance.

[0073] 4. With reference to ASTMD573-04 (2015), an accelerated thermal oxidative aging test chamber was used to conduct thermal oxidative accelerated aging experiments. The blank group and the rubber vulcanizates containing the antioxidants prepared in Example 1 and Comparative Examples 1 to 3 were cut into dumbbell-shaped rubber tensile specimens, and hung at intervals on the rotating rack of the thermal oxidative aging chamber. The aging temperature was 100°C. The specimens were taken out according to the set aging time, and their mechanical properties were tested according to the standard ASTMD412-15a. The tensile strength retention rate Rt was calculated, Rt=Ta / Tu×100%, where Tu and Ta were the tensile strength before and after aging, respectively; the elongation at break retention rate Rg, Rg=Ea / Eu×100%, where Eu and Ea were the elongation at break before and after aging, respectively; the anti-aging coefficient k, f=T×E, k=fa×fu, f is the tensile product, T is the tensile strength, E is the elongation at break, and fu and fa are the tensile products before and after aging, respectively. The results are as follows. Figure 4 shown.

[0074] from Figure 4 As can be seen from the results, during 9 days of thermal oxidative aging at 100°C, the mechanical property retention of almost all rubber vulcanizates decreased with increasing aging time. The aging coefficient showed a similar trend to the tensile strength retention rate. The blank group, which did not contain an antioxidant, had the lowest aging coefficient. This was primarily due to the lack of antioxidant protection during the aging process, leading to a decline in rubber vulcanizate performance. Example 1 exhibited the best anti-aging effect, with the order from strongest to weakest being Example 1 > Comparative Example 3 > Comparative Example 2 > Comparative Example 1 > Blank group.

[0075] 5. Scanning electron microscopy was used to observe the cross-section of the blank group and the rubber vulcanizates containing the antioxidants of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3. The results are as follows: Figure 5 shown.

[0076] from Figure 5 It can be seen that in the blank group without adding antioxidant, the silicon dioxide is unevenly dispersed and agglomerated in a large area; in Comparative Example 1, the silicon dioxide is still unevenly dispersed and the agglomeration phenomenon is serious; in Comparative Example 3, the silicon dioxide agglomerates in a small area and is evenly dispersed; Comparative Example 2 and Example 1 are the most evenly dispersed.

[0077] 6. Anti-caking test

[0078] The antioxidants prepared in Examples 1 to 3 and the commercially available antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine were placed in an environment at 30°C and 75% humidity for 10 days and observed for caking. It was found that the commercially available antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine exhibited severe caking, while the antioxidants prepared in Examples 1 to 3 exhibited no caking.

[0079] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An anti-caking composite rubber antioxidant 6PPD, characterized by: The raw materials include the following components in parts by weight: 20-30 parts of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 80-100 parts of functional antioxidant, 15-20 parts of microcrystalline wax, and 2-4 parts of antioxidant; the functional antioxidant is prepared by the following steps: S1, reacting 3-aminoadipic acid with sodium hydroxide solution to prepare 3-aminoadipate solution; S2, adding 4-pentenyl isothiocyanate ethanol solution dropwise to 3-aminoadipate solution, heating and stirring to react, and purifying. After treatment, intermediate 1 is obtained; S3, intermediate 1 and a silane coupling agent are dissolved in DMF, triethylamine is added, and the mixture is heated and stirred to react to obtain an intermediate 2 solution; S4, silicon dioxide is dispersed in an ethanol aqueous solution, the pH is adjusted to 10-11, ultrasonically dispersed uniformly, and under an inert gas atmosphere, the intermediate 2 solution is added dropwise, heated to react, and after purification treatment, intermediate 3 is obtained; S5, under heating, the aqueous solution of lanthanum chloride is added dropwise to the dispersion of intermediate 3, stirred to react, and after purification treatment, a functional antioxidant is obtained.

2. The anti-caking composite rubber antioxidant 6PPD according to claim 1, characterized in that: The antioxidant is a thioester antioxidant.

3. The anti-caking composite rubber antioxidant 6PPD according to claim 1, characterized in that: The molar ratio of 3-aminoadipic acid and sodium hydroxide is 1:(2.1-2.3).

4. The anti-caking composite rubber antioxidant 6PPD according to claim 1, characterized in that: The molar ratio of 3-aminoadipate to 4-pentenyl isothiocyanate is 1:(1-1.2).

5. The anti-caking composite rubber antioxidant 6PPD according to claim 1, characterized in that: The silane coupling agent is one of KH-590, KH-580, KH-581 and KH-582.

6. The anti-caking composite rubber antioxidant 6PPD according to claim 1, characterized in that: The molar ratio of the intermediate 1, the silane coupling agent and the triethylamine is 1:(1.2-1.5):(0.3-0.5).

7. The anti-caking composite rubber antioxidant 6PPD according to claim 1, characterized in that: The mass ratio of silicon dioxide to intermediate 1 is 100:(10-20).

8. The anti-caking composite rubber antioxidant 6PPD according to claim 2, characterized in that: The molar ratio of lanthanum chloride to intermediate 3 is (1.5-2):

1.

9. The method for preparing the anti-caking composite rubber antioxidant 6PPD according to any one of claims 1 to 8, wherein: The following steps are involved: (1) Melt and liquefy the microcrystalline wax by heating; (2) Add N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, functional antioxidant and antioxidant in batches and stir until the system has no agglomerated particles; (3) Transfer to a high shear emulsifier to further form a uniform dispersion system; (4) Extrude through a twin-screw extruder, water-cool and pelletize to obtain the anti-caking composite rubber antioxidant 6PPD.

Images