Pyridyl anti-aging agent as well as synthesis method and application thereof

Abstract

The invention discloses a pyridyl anti-aging agent as well as a synthesis method and application thereof, the anti-aging agent is obtained by taking 5-nitro-N-phenylpyridine-2-amine synthesized by 2-chloro-5-nitropyridine and aniline and iodide synthesized by alcohol and iodine as raw materials, and reacting in the presence of a hydrogen source and a catalyst. The anti-aging agent provided by the invention can effectively slow down the emigration speed of the anti-aging agent in rubber and greatly improve the phenomenon that the appearance of a tire becomes red, has one more N heteroatom than other anti-aging agents in the structure, has good oxidation resistance and flex cracking resistance, and is high in anti-ozone activity, environment-friendly and small in pollution.

Description

Technical Field

[0001] The invention relates to a pyridine-based antioxidant, and also relates to a synthesis method and application of the pyridine-based antioxidant, belonging to the technical field of antioxidant synthesis. Background Art

[0002] At present, the main anti-ozone antioxidants used in rubber tire products at home and abroad are p-phenylenediamine antioxidants, which mainly include antioxidant 3100, antioxidant 4020, antioxidant 4030, etc.

[0003] Antioxidants 4020 and 4030 are mainly used as anti-ozonants for natural rubber and general synthetic rubber. They also have protective effects against heat aging and flex cracking, and have excellent chemical corrosion resistance. However, their biggest drawbacks are serious discoloration and high pollution, as well as migration and migration pollution. Antioxidant 3100 has one or two solubilizing groups introduced into the benzene rings on both sides of the molecular structure, so its solubility in rubber is greatly improved, thereby slowing down the migration speed of the antioxidant in rubber products, providing a certain long-term protective effect, and to a certain extent improving the phenomenon of tires turning red when using antioxidants 4020 and 4030. However, due to the conjugated effect of the benzene ring, the electron cloud density of the amino group in the antioxidant 3100 decreases, and the ability of the amino group to capture ozone decreases. Therefore, the ozone protection effect of antioxidant 3100 is far inferior to that of antioxidants 4020 and 4030.

[0004] Therefore, it is urgent to develop a new antioxidant that has anti-oxidative aging, migration resistance and environmental friendliness. Summary of the invention

[0005] In view of the problems of poor migration resistance, serious discoloration and poor anti-ozone activity of existing antioxidants, the present invention provides a pyridine-based antioxidant named N 5 -(R-radical)-N 2 -phenylpyridine-2,5-diamine, having the structural formula shown in the following formula (1):

[0006]

[0007] In the formula (1), R is cyclohexyl, cyclooctyl, isopropyl, 3-methylbutanyl, 4-methylpentanyl, 5-methylhexanyl, 1,3-dimethylbutyl or benzyl.

[0008] The present invention also provides a method for synthesizing the above-mentioned pyridine-based antioxidant, wherein 5-nitro-N-phenylpyridine-2-amine synthesized from 2-chloro-5-nitropyridine and aniline is reacted with an iodide synthesized from an alcohol and iodine, and a hydrogen source and a catalyst are added to react under certain conditions to obtain a final antioxidant product, and the reaction formula is as follows:

[0009]

[0010] Furthermore, the synthesis method of the above pyridine-based antioxidant comprises the following steps:

[0011] (1) reacting 2-chloro-5-nitropyridine with aniline in the presence of an acid binding agent and a catalyst to obtain 5-nitro-N-phenylpyridine-2-amine;

[0012] (2) subjecting the alcohol represented by formula a to a reflux reaction with iodine under a catalyst and gas protection to obtain an iodide represented by formula b;

[0013] (3) 5-nitro-N-phenylpyridine-2-amine, the iodide shown in formula b, and a hydrogen source are reacted in the presence of a catalyst and gas protection to obtain a pyridine-based antioxidant shown in formula (1).

[0014] Further, in step (1), the acid binding agent is an alkaline substance such as sodium carbonate, potassium carbonate, sodium hydroxide, etc., and the role of the acid binding agent is to remove the hydrogen chloride by-product produced by the reaction. The acid binding agent is added according to the theoretical molar amount or slightly added in excess. For example, when the acid binding agent is sodium carbonate or potassium carbonate, the molar ratio of 2-chloro-5-nitropyridine to the acid binding agent is 1:0.5-1.0, such as 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0; when the acid binding agent is sodium hydroxide, the molar ratio of 2-chloro-5-nitropyridine to the acid binding agent is 1:1.0-2.5, such as 1:1, 1:1.5, 1:2, 1:2.5.

[0015] Furthermore, in step (1), the catalyst is cupric oxide, cuprous oxide, zinc powder, etc. The amount of the catalyst is 2% to 8% of the mass of 2-chloro-5-nitropyridine, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, preferably 3% to 5%.

[0016] Furthermore, in step (1), the molar ratio of 2-chloro-5-nitropyridine to aniline is 1:10 to 30, for example, 1:10, 1:15, 1:20, 1:25, 1:30.

[0017] Furthermore, in step (1), the reaction temperature is 150-200° C., for example, 150° C., 160° C., 170° C., 180° C., 190° C., 200° C. At this reaction temperature, the reaction time is generally 1-8 h, for example, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h.

[0018] Further, in step (1), after the reaction is completed, the reaction solution is post-treated to obtain 5-nitro-N-phenylpyridine-2-amine. The post-treatment step is: after the reaction is completed, the catalyst is filtered out, then the temperature is lowered to room temperature for crystallization, and the precipitated crystals are filtered, washed, and dried to obtain 5-nitro-N-phenylpyridine-2-amine.

[0019] Furthermore, in step (2), the alcohol used is ROH, wherein the definition of R is consistent with that in formula (1), and examples of the alcohol include methyl isobutyl carbinol, isopropanol, phenylethyl alcohol, cyclohexanol, and the like.

[0020] Furthermore, in step (2), the catalyst is triphenylphosphine. The molar ratio of alcohol to catalyst is 1:1.2 to 2.0, such as 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, preferably 1:1.5 to 2.0.

[0021] Furthermore, in step (2), the molar ratio of alcohol to iodine is 1:1.2 to 2.0, for example 1:1.2,

[0022] 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, preferably 1:1.3-1.5.

[0023] Furthermore, in step (2), the reaction is carried out in the presence of a solvent, and the solvent is a halogenated hydrocarbon, such as dichloromethane.

[0024] Furthermore, in step (2), the reaction is carried out under gas protection, and the gas is an inert gas such as nitrogen and argon.

[0025] Furthermore, in step (2), the reaction temperature is 40-50° C., for example, 40° C., 45° C., 50° C. At this reaction temperature, the reaction time is generally 8-12 hours.

[0026] Furthermore, in step (2), the reaction solution is post-treated after the reaction to obtain iodide, and the post-treatment steps are: the reaction solution is washed with saturated sodium thiosulfate until the color of iodine disappears, a saturated calcium bromide solution is added and stirred for 3 hours, and then filtered and extracted with dichloromethane / water, and the obtained organic phase is distilled under reduced pressure to obtain iodide.

[0027] Further, in step (3), the catalyst is ferrous chloride tetrahydrate and zinc powder, wherein the molar ratio of ferrous chloride tetrahydrate to 5-nitro-N-phenylpyridine-2-amine is 1:2 to 1:5, for example, 1:2, 1:3, 1:4, 1:5, preferably 1:3 to 1:5. The molar ratio of zinc powder to 5-nitro-N-phenylpyridine-2-amine is 1:2 to 1:5, for example, 1:2, 1:3, 1:4, 1:5, preferably 1:3 to 1:5.

[0028] Furthermore, in step (3), the hydrogen source is trimethylsilyl trifluoromethanesulfonate, and the molar ratio of trimethylsilyl trifluoromethanesulfonate to 5-nitro-N-phenylpyridin-2-amine is 1:2 to 1:5, for example, 1:2, 1:3, 1:4, 1:5, preferably 1:3 to 1:5.

[0029] Furthermore, in step (3), the molar ratio of 5-nitro-N-phenylpyridin-2-amine to iodide is 1:1.5 to 3.0, preferably 1:2.0 to 3.0.

[0030] Furthermore, in step (3), the reaction is carried out in a solvent, and the solvent is NMP, DMSO, DMF, etc.

[0031] Furthermore, in step (3), the reaction temperature is 80-150° C., for example, 80° C., 90° C., 100° C., 110° C., 120° C., 130° C., 140° C., 150° C., preferably 100-120° C. The reaction time is generally 8-12 h, for example, 8 h, 9 h, 10 h, 11 h, 12 h.

[0032] Furthermore, in step (3), the reaction is carried out under gas protection, and the gas is an inert gas such as nitrogen and argon.

[0033] Furthermore, in step (3), the reaction solution is post-treated after the reaction to obtain a final antioxidant product, and the post-treatment steps are: after the reaction is completed, the catalyst is filtered out, then cooled and crystallized, and the precipitated crystals are filtered, washed, and dried to obtain the final antioxidant product.

[0034] The present invention also provides the use of the above-mentioned pyridine-based antioxidant in rubber products. The pyridine-based antioxidant can be used as a rubber antioxidant in rubber products such as tires, can improve the antioxidant capacity of rubber products, and can also slow down migration on the tire surface.

[0035] The present invention has the following beneficial effects:

[0036] 1. The antioxidant of the present invention exerts its effect through the adsorption of N heteroatoms on the rubber surface and the conjugated double bond structure in its molecular structure, which can effectively slow down the migration speed of the antioxidant in the rubber and greatly improve the phenomenon of tire appearance turning red. In addition, the antioxidant has one more N heteroatom in its structure than other antioxidants, and at the same time has good antioxidant performance and anti-flex cracking performance, high anti-ozone activity, is environmentally friendly, and has little pollution.

[0037] 2. Common antioxidants such as antioxidant 4020 and antioxidant 4030 need to be subjected to ketoamine reaction under high pressure, and the reaction conditions are relatively harsh and dangerous. The present invention converts the ketoamine reaction into an amino-substituted halogen reaction, and does not require the use of hydrogen and an autoclave, thereby reducing the risk of the reaction. The preparation method is simple, the risk is low, the product yield is high, the purity is high, and no side reactions occur. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 N prepared in Example 13 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 1 H-NMR spectrum.

[0039] Figure 2 N prepared in Example 13 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 13 C-NMR spectrum.

[0040] Figure 3 N prepared in Example 14 5 -(Phenylethyl)-N 2 -phenylpyridine-2,5-diamine 1 H-NMR spectrum.

[0041] Figure 4 N prepared in Example 14 5 -(Phenylethyl)-N 2 -phenylpyridine-2,5-diamine 13 C-NMR spectrum. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited thereto.

[0043] Unless otherwise specified, all raw materials used in the following examples are commercially available products.

[0044] In the following examples, the calculation formula for yield is: yield = target product (actual) production amount / target product theoretical production amount × 100%.

[0045] Synthesis of 5-Nitro-N-phenylpyridin-2-amine

[0046] Example 1

[0047] 15.85g 2-chloro-5-nitropyridine and 186.26g aniline were added to a flask, 6.36g sodium carbonate and 0.32g copper oxide were added, and the temperature was raised to 190°C for reaction. After 8 hours of reaction, the copper oxide catalyst in the reaction solution was filtered out while hot, and the filtered reaction solution was cooled to room temperature to precipitate solids. The solids were filtered, washed, and dried to obtain 17.73g 5-nitro-N-phenylpyridine-2-amine, and the product purity (HPLC) was 95.56%. The theoretical mass of 5-nitro-N-phenylpyridine-2-amine was 21.52g, and the product yield was 82.4%.

[0048] Example 2

[0049] 15.85g 2-chloro-5-nitropyridine and 186.26g aniline were added to a flask, 10.6g sodium carbonate and 0.48g copper oxide were added, and the temperature was raised to 190°C for reaction. After 2h of reaction, the copper oxide catalyst in the reaction solution was filtered out while hot, and the filtered reaction solution was cooled to room temperature to precipitate solids. The solids were filtered, washed, and dried to obtain 20.58g 5-nitro-N-phenylpyridine-2-amine, and the product purity (HPLC) was 99.00%. The theoretical mass of 5-nitro-N-phenylpyridine-2-amine was 21.52g, and the product yield was 95.6%.

[0050] Example 3

[0051] 15.85g 2-chloro-5-nitropyridine and 186.26g aniline were added to a flask, 10.6g sodium carbonate and 0.48g copper oxide were added, and the temperature was raised to 160°C for reaction. After 4h of reaction, the copper oxide catalyst in the reaction solution was filtered out while hot, and the filtered reaction solution was cooled to room temperature to precipitate solids. The solids were filtered, washed, and dried to obtain 20.71g 5-nitro-N-phenylpyridine-2-amine, and the product purity (HPLC) was 98.87%. The theoretical mass of 5-nitro-N-phenylpyridine-2-amine was 21.52g, and the product yield was 96.2%.

[0052] Synthesis of iodides

[0053] Example 4

[0054] Dissolve 10.22g of methyl isobutyl carbinol and 30.46g of iodine in 200ml of dichloromethane and add to a flask. After adding 31.48g of triphenylphosphine, the reaction system is refluxed with nitrogen. The reflux temperature is about 40-45°C. The reaction is terminated after 8 hours. The reaction solution is washed with saturated sodium thiosulfate until the color of iodine disappears. Add saturated calcium bromide solution and stir for 3 hours. After suction filtration, dichloromethane and water (mass ratio 1:1) are added again for extraction and separation. The organic phase obtained by separation is distilled under reduced pressure to obtain 13.8g of iodide solid, and the product purity (HPLC) is 89.72%. The theoretical iodide mass is 21.21g, and the product yield is 65.1%.

[0055]

[0056] Example 5

[0057] Dissolve 10.22g of methyl isobutyl carbinol and 30.46g of iodine in 200ml of dichloromethane and add to a flask. After adding 39.35g of triphenylphosphine, the reaction system is refluxed with nitrogen. The reflux temperature is about 40-45°C. The reaction is terminated after 8 hours. The reaction solution is washed with saturated sodium thiosulfate until the color of iodine disappears. Add saturated calcium bromide solution and stir for 3 hours. After suction filtration, dichloromethane and water (mass ratio 1:1) are added again for extraction and separation. The organic phase obtained by separation is distilled under reduced pressure to obtain 15.89g of iodide solid, and the product purity (HPLC) is 92.55%. The theoretical iodide mass is 21.21g, and the product yield is 74.9%.

[0058] Example 6

[0059] Dissolve 10.22g of methyl isobutyl carbinol and 38.07g of iodine in 200ml of dichloromethane and add to a flask. After adding 39.35g of triphenylphosphine, the reaction system is refluxed with nitrogen. The reflux temperature is about 40-45°C. The reaction is terminated after 8 hours. The reaction solution is washed with saturated sodium thiosulfate until the color of iodine disappears. Add saturated calcium bromide solution and stir for 3 hours. After suction filtration, dichloromethane and water (mass ratio 1:1) are added again for extraction and separation. The organic phase obtained by separation is distilled under reduced pressure to obtain 15.97g of iodide solid, and the product purity (HPLC) is 97.09%. The theoretical iodide mass is 21.21g, and the product yield is 75.3%.

[0060] Example 7

[0061] Dissolve 10.22g of methyl isobutyl carbinol and 33.00g of iodine in 200ml of dichloromethane and add to a flask. After adding 39.35g of triphenylphosphine, the reaction system is refluxed with nitrogen. The reflux temperature is about 40-45°C. The reaction is terminated after 10 hours. The reaction solution is washed with saturated sodium thiosulfate until the color of iodine disappears. Add saturated calcium bromide solution and stir for 3 hours. After suction filtration, dichloromethane and water (mass ratio 1:1) are added again for extraction and separation. The organic phase obtained by separation is distilled under reduced pressure to obtain 16.81g of iodide solid, and the product purity (HPLC) is 98.14%. The theoretical iodide mass is 21.21g, and the product yield is 79.3%.

[0062] Example 8

[0063] Dissolve 12.22g of phenylethanol and 33.00g of iodine in 200ml of dichloromethane and add to a flask. After adding 39.35g of triphenylphosphine, the reaction system is refluxed with nitrogen. The reflux temperature is about 40-45°C. The reaction is terminated after 10 hours. The reaction solution is washed with saturated sodium thiosulfate until the color of iodine disappears. Add saturated calcium bromide solution and stir for 3 hours. After suction filtration, dichloromethane and water (mass ratio 1:1) are added again for extraction and separation. The organic phase obtained by separation is distilled under reduced pressure to obtain 18.19g of iodide solid, and the product purity (HPLC) is 98.65%. The theoretical iodide mass is 23.21g, and the product yield is 78.4%.

[0064]

[0065] Example 9

[0066] Dissolve 6.01g isopropanol and 33.00g iodine in 200ml dichloromethane and add to a flask. After adding 39.35g triphenylphosphine, the reaction system is refluxed with nitrogen. The reflux temperature is about 40-45°C. The reaction is terminated after 10 hours. The reaction solution is washed with saturated sodium thiosulfate until the color of iodine disappears. A saturated solution of calcium bromide is added and stirred for 3 hours. After suction filtration, dichloromethane and water (mass ratio 1:1) are added again for extraction and separation. The organic phase obtained by separation is distilled under reduced pressure to obtain 13.25g of iodide solid, and the product purity (HPLC) is 98.22%. The theoretical iodide mass is 17.00g, and the product yield is 77.9%.

[0067]

[0068] Synthesis of Antiaging Agent The antioxidant was synthesized using the 5-nitro-N-phenylpyridine-2-amine synthesized in Example 2 and the iodides synthesized in Examples 7, 8 and 9 as raw materials.

[0069] Example 10

[0070] Dissolve 21.52g 5-nitro-N-phenylpyridine-2-amine and 31.81g iodide (synthesized from methyl isobutyl carbinol and iodine) in 200ml NMP, add 39.76g ferrous chloride tetrahydrate and 13g zinc powder, and add 44.45g trimethylsilyl trifluoromethanesulfonate, the reaction temperature is 80°C, and the reaction is about 10h. After the reaction is completed, the solid catalyst is filtered out, then cooled and crystallized, the precipitated crystals are filtered, washed, and dried to obtain the final antioxidant product N 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 19.53 g, product purity (HPLC) is 77.62%. Theoretical N 5 -(1,3-dimethylbutyl)-N 2-phenylpyridine-2,5-diamine 26.94 g, product yield 72.5%.

[0071]

[0072] Embodiment 11

[0073] Dissolve 21.52g 5-nitro-N-phenylpyridine-2-amine and 31.81g iodide (synthesized from methyl isobutyl carbinol and iodine) in 200ml NMP, add 59.64g ferrous chloride tetrahydrate and 19.5g zinc powder, and add 88.90g trimethylsilyl trifluoromethanesulfonate, the reaction temperature is 80°C, and the reaction is about 10h. After the reaction is completed, the solid catalyst is filtered out, then cooled and crystallized, the precipitated crystals are filtered, washed, and dried to obtain the final antioxidant product N 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 20.81 g, product purity (HPLC) is 81.59%. Theoretical N 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 26.94 g, product yield 77.2%.

[0074] Example 12

[0075] Dissolve 21.52g 5-nitro-N-phenylpyridine-2-amine and 46.65g iodide (synthesized from methyl isobutyl carbinol and iodine) in 200ml NMP, add 59.64g ferrous chloride tetrahydrate and 19.5g zinc powder, and add 66.68g trimethylsilyl trifluoromethanesulfonate, the reaction temperature is 80°C, and the reaction is about 10h. After the reaction is completed, the solid catalyst is filtered out, then cooled and crystallized, the precipitated crystals are filtered, washed, and dried to obtain the final antioxidant product N 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 22.51 g, product purity (HPLC) is 95.13%. Theoretical N 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 26.94 g, product yield 83.6%.

[0076] Example 13

[0077] Dissolve 21.52g 5-nitro-N-phenylpyridine-2-amine and 46.65g iodide (synthesized from methyl isobutyl carbinol and iodine) in 200ml NMP, add 59.64g ferrous chloride tetrahydrate and 19.5g zinc powder, and add 66.68g trimethylsilyl trifluoromethanesulfonate, the reaction temperature is 100°C, and the reaction is about 10h. After the reaction is completed, the solid catalyst is filtered out, then cooled and crystallized, the precipitated crystals are filtered, washed, and dried to obtain the final antioxidant product N 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 24.10 g, product purity (HPLC) is 97.75%. Theoretical N 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 26.94 g, product yield 89.5%.

[0078] Embodiment 14

[0079] Dissolve 21.52g 5-nitro-N-phenylpyridine-2-amine and 51.05g iodide (synthesized from phenylethanol and iodine) in 200ml NMP, add 59.64g ferrous chloride tetrahydrate and 19.5g zinc powder, and add 66.68g trimethylsilyl trifluoromethanesulfonate, the reaction temperature is 120°C, and the reaction is about 10h. After the reaction is completed, filter out the solid catalyst, cool and crystallize, filter, wash and dry the precipitated crystals to obtain the final antioxidant product N 5 -(Phenylethyl)-N 2 -phenylpyridine-2,5-diamine 25.25 g, product purity (HPLC) is 98.01%. Theoretical N 5 -(1,4-phenylethyl)-N 2 -phenylpyridine-2,5-diamine 28.94 g, product yield 87.2%.

[0080] Embodiment 15

[0081] Dissolve 21.52g 5-nitro-N-phenylpyridine-2-amine and 37.40g iodide (synthesized by isopropanol and iodine) in 200ml NMP, add 59.64g ferrous chloride tetrahydrate and 19.5g zinc powder, and add 66.68g trimethylsilyl trifluoromethanesulfonate, the reaction temperature is 100℃, and the reaction is about 10h. After the reaction is completed, the solid catalyst is filtered out, then cooled and crystallized, the precipitated crystals are filtered, washed and dried to obtain the final antioxidant product N 5 -(isopropyl)-N 2 -phenylpyridine-2,5-diamine 20.10 g, product purity (HPLC) is 97.72%. Theoretical N 5 -(isopropyl)-N2 -phenylpyridine-2,5-diamine 22.73 g, product yield 88.4%.

[0082] Comparative Example 1

[0083] 21.52g 5-nitro-N-phenylpyridine-2-amine and 46.65g iodide (Methyl isobutyl carbinol and iodine synthesis) were dissolved in 200ml NMP, 19.5g zinc powder and 66.68g trifluoromethanesulfonic acid trimethylsilyl ester were added, the reaction temperature was 80°C, and the reaction was carried out for about 10h. After the reaction was completed, the solid catalyst was filtered out, and then cooled and crystallized. The precipitated crystals were filtered, washed, and dried to obtain the final antioxidant product N 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 17.14 g, product purity (HPLC) is 85.13%. Theoretical N 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 26.94 g, product yield 63.6%.

[0084] Comparative Example 2

[0085] 21.52g 5-nitro-N-phenylpyridine-2-amine and 46.65g iodide (Methyl isobutyl carbinol and iodine synthesis) were dissolved in 200ml NMP, 59.64g ferrous chloride tetrahydrate and 6g palladium carbon catalyst were added, and 66.68g trifluoromethanesulfonic acid trimethylsilyl ester was added, the reaction temperature was 80°C, and the reaction was carried out for about 10h. After the reaction was completed, the solid catalyst was filtered out, and then cooled and crystallized. The precipitated crystals were filtered, washed, and dried to obtain the final antioxidant product N 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 20.91 g, product purity (HPLC) is 62.97%. Theoretical N 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 26.94 g, product yield 77.6%.

[0086] Comparative Example 3

[0087] 21.52g 5-nitro-N-phenylpyridine-2-amine and 46.65g iodide (Methyl isobutyl carbinol and iodine synthesis) were dissolved in 200ml NMP, 59.64g ferrous chloride tetrahydrate and 66.68g trifluoromethanesulfonic acid trimethylsilyl ester were added, the reaction temperature was 80°C, and the reaction was carried out for about 10h. After the reaction was completed, the solid catalyst was filtered out, and then cooled and crystallized. The precipitated crystals were filtered, washed and dried to obtain the final antioxidant product N 5-(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 15.25 g, product purity (HPLC) is 73.13%. Theoretical N 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine 26.94 g, product yield 56.6%.

[0088] Performance Verification

[0089] The N synthesized in Example 13 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine (new antioxidant 1), N 5 -(1,4-phenylethyl)-N 2 -phenylpyridine-2,5-diamine (new antioxidant 2), N synthesized in Example 15 5 -(isopropyl)-N 2 -phenylpyridine-2,5-diamine (new antioxidant 3) and antioxidant 4030 were used for application comparison experiments.

[0090] 1. Vulcanized rubber sample formula (parts by weight): 100 parts of natural rubber NR, 50 parts of carbon black N220, 3.5 parts of pine tar, 5.0 parts of zinc oxide, 3.0 parts of stearic acid, 0.6 parts of accelerator M, 0.6 parts of sulfur, and 3.0 parts of antioxidant. The antioxidants are the above-mentioned new antioxidant 1, new antioxidant 2, new antioxidant 3, and antioxidant 4030. At the same time, the sample without antioxidant is used as a blank control.

[0091] 2. Rubber processing technology: The rotor speed of the first stage mixing is 40r·min -1 NR was first plasticized for 1 min, then carbon black N220, pine tar, zinc oxide, stearic acid, and antioxidant were added, the pressing roller was pressed for 35 s, the pressing roller was raised for 10 s, the pressing roller was pressed for 45 s, the pressing roller was raised for 10 s, and the rubber was discharged (145 ℃). The rotor speed of the second stage mixing was 48 r·min-1, and the rubber, sulfur, and accelerator M were mixed in the first stage, the pressing roller was pressed for 80 s, the pressing roller was raised for 10 s, the pressing roller was pressed for 55 s, and the rubber was discharged (110 ℃).

[0092] 3. Performance comparison

[0093] 3.1 Mooney viscosity

[0094] The hot air aging test method is used to measure the efficiency of the antioxidant. The Mooney viscosity of the sample after the aging test is used to characterize the anti-aging performance of the antioxidant. The smaller the change in Mooney viscosity, the better the anti-thermal oxidative aging performance. Conversely, the greater the change in Mooney viscosity, the worse the anti-thermal oxidative aging performance. Mooney viscosity is tested according to GB / T 1232-2000 standard.

[0095] The five samples were placed in an aging box for hot air aging, and the Mooney viscosity (M) of the samples at 100°C was measured at different aging times. 100℃ 1+4 ), the test results are shown in Table 1.

[0096] Table 1 Mooney viscosity at different aging times

[0097]

[0098]

[0099] As can be seen from Table 1, in the four formulations, after all the vulcanizates were oxidized by hot air for the same time, the increase in Mooney viscosity gradually decreased, and the increase in Mooney viscosity of the vulcanizates with the three new antioxidants was smaller than that of the vulcanizates with antioxidant 4030 added and without any antioxidant added, indicating that the new antioxidant of the present invention has stronger resistance to thermal oxidative aging, among which the new antioxidant 1 has the best resistance to thermal oxidative aging.

[0100] 3.2 Flex cracking effect under different formulations

[0101] The five samples were subjected to the vulcanized rubber flex cracking resistance test according to GB13934-1992 standard. The test results are shown in Table 2.

[0102] Table 2 Flex cracking effect under different formulations

[0103]

[0104]

[0105] It can be seen from Table 2 that in terms of crack test, the three new multifunctional antioxidants of the present invention have better anti-flex cracking effect than antioxidant 4030, among which the new antioxidant 1 has the best anti-flex cracking performance.

[0106] In summary, the N synthesized by the present invention 5 -(R-radical)-N 2 -phenylpyridine-2,5-diamine also has strong resistance to thermal oxidation aging, among which N 5 -(1,3-dimethylbutyl)-N 2 -phenylpyridine-2,5-diamine has the best effect.

Claims

1. A pyridine-based antioxidant, characterized in that: It has the structural formula described in the following formula (1): Among them, R is cyclohexyl, cyclooctyl, isopropyl, 3-methylbutanyl, 4-methylpentanyl, 5-methylhexanyl, 1,3-dimethylbutyl, or benzyl.

2. A method for synthesizing a pyridine-based antioxidant, characterized in that The following steps are involved: (1) reacting 2-chloro-5-nitropyridine with aniline in the presence of an acid binding agent and a catalyst to obtain 5-nitro-N-phenylpyridine-2-amine; (2) The alcohol represented by formula a is subjected to reflux reaction with iodine under a catalyst and gas protection to obtain an iodide represented by formula b. The reaction formula is as follows: (3) reacting 5-nitro-N-phenylpyridine-2-amine, the iodide represented by formula (b), and a hydrogen source in the presence of a catalyst and gas protection to obtain a pyridine-based antioxidant represented by formula (1); 3. The synthesis method according to claim 2, characterized in that: R is cyclohexyl, cyclooctyl, isopropyl, 3-methylbutanyl, 4-methylpentanyl, 5-methylhexanyl, 1,3-dimethylbutyl, or benzyl.

4. The synthesis method according to claim 2, characterized in that: In step (1), the acid-binding agent is an alkaline substance; and the catalyst is cupric oxide, cuprous oxide, or zinc powder.

5. The synthesis method according to any one of claims 2 to 4, characterized in that: In step (1), at least one of the following conditions is included: Condition 1: The amount of catalyst used is 2% to 8% of the mass of 2-chloro-5-nitropyridine; Condition 2: The molar ratio of 2-chloro-5-nitropyridine to aniline is 1:10-30; Condition 3: reaction temperature is 150-200°C; Condition 4: Reaction time is 1 to 8 hours.

6. The synthesis method according to claim 2, characterized in that: In step (2), the catalyst is triphenylphosphine.

7. The synthesis method according to claim 2 or 6, characterized in that: In step (2), at least one of the following conditions is included: Condition 1: The molar ratio of alcohol to catalyst is 1:1.2-2.0; Condition 2: The molar ratio of alcohol to iodine is 1:1.2-2.0; Condition 3: reaction temperature is 40-50°C; Condition 4: reaction time is 8 to 12 hours; Condition 5: The gas is an inert gas; Condition 6: The reaction is carried out in the presence of a solvent, which is a halogenated hydrocarbon.

8. The synthesis method according to claim 2, characterized in that: In step (3), at least one of the following conditions is included: Condition 1: The catalyst is ferrous chloride tetrahydrate and zinc powder; Condition 2: The hydrogen source is trimethylsilyl trifluoromethanesulfonate; Condition 3: The molar ratio of 5-nitro-N-phenylpyridin-2-amine to iodide is 1:1.5-3.0; Condition 4: The reaction is carried out under solvent and gas protection; Condition 5: reaction temperature is 80-150°C; Condition 6: The reaction time is 8 to 12 hours.

9. The synthesis method according to claim 8, characterized in that: In step (3), the molar ratio of ferrous chloride tetrahydrate to 5-nitro-N-phenylpyridine-2-amine is 1:2 to 1:5, the molar ratio of zinc powder to 5-nitro-N-phenylpyridine-2-amine is 1:2 to 1:5; and the molar ratio of hydrogen source to 5-nitro-N-phenylpyridine-2-amine is 1:2 to 1:

5.

10. Use of the pyridine antioxidant according to claim 1 in rubber products.

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