Nitrogen heterocyclic ring-containing compound and preparation method and application thereof

Abstract

The invention discloses a nitrogen heterocyclic ring-containing compound and a preparation method and application thereof, and the preparation method of the compound comprises the following steps: carrying out condensation reaction on 2, 5-diaminopyrimidine and 2, 6-dimethyl-4-nitrochlorobenzene under the action of alkali to obtain an intermediate 1; and introducing hydrogen into the intermediate 1 and 5-methyl-2-hexanone under the action of a catalyst to carry out reductive condensation reaction to obtain a product. The compound has a special structure, contains pyrimidine and benzene ring groups, has a good ozone protection effect when being used in rubber products, has different substituent groups on benzene rings, does not generate p-benzoquinone or o-benzoquinone toxic substances, is higher in environmental protection property and large in molecular weight, is not easy to discolor and emigrate when being used in the rubber products, and has a good application prospect. And the anti-aging agent has high application value in the aspect of aging resistance of rubber materials.

Description

Technical Field

[0001] The invention relates to a nitrogen-containing heterocyclic compound and a preparation method thereof, and also relates to application of the compound as a novel green rubber antioxidant, belonging to the technical field of antioxidants. Background Art

[0002] Antioxidants are essential additives in the rubber industry because they effectively prevent aging and degradation of rubber products, thereby improving their reliability and service life. Generally, aniline antioxidants have the strongest antioxidant properties of all antioxidant types due to their active antioxidant groups. However, due to the presence of the aniline group, they are generally darker in color, making them suitable only for products insensitive to color contamination, such as those used in the tire industry and automotive gaskets. This type of antioxidant specifically includes dialkyl-p-phenylenediamines, alkylaryl-p-phenylenediamines, and diaryl-p-phenylenediamines. The most widely used antioxidant is 6PPD (N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine). 6PPD has a relatively small molecular weight, and antioxidants in rubber products or tires migrate quickly to the surface during use, leading to surface staining and discoloration. A 6PPD derivative, 6PPD-quinone (6PPDQ), has recently been identified as a ubiquitous oxidation product of 6PPD. Previous studies have suggested that 6PPDQ is primarily formed through ozone oxidation, but other pathways, such as photochemical processes, may also lead to its formation in the natural environment. A potential photoreaction pathway for 6PPD has been proposed: 6PPD is first irradiated to generate a high-energy excited state, *6PPD. The irradiated *6PPD may undergo the following reactions: 1) cleavage of the C-N bond between the imino nitrogen and the secondary carbon, leading to the formation of 4-aminodiphenylamine and aniline; 2) generation of *O2 by energy transfer from *6PPD to an O2 molecule; and 3) photoexcited dehydrogenation or H abstraction of *O2 to produce a conjugated quinone imine product (6PPDQI). Subsequently, two *O2 oxidations of 6PPDQI lead to the formation of 6PPDQ. The structural formula of 6PPD is shown in Formula 1 below, and the structural formula of 6PPDQ is shown in Formula 2 below.

[0003]

[0004] 6PPDQ, recently reported by the U.S. Tire Manufacturers Association as having a high acute mortality rate in aquatic cod, has garnered significant attention from the rubber chemical industry worldwide. Consequently, there is an urgent need for an environmentally friendly antioxidant with longer-lasting aging protection compared to existing products. Summary of the Invention

[0005] The object of the present invention is to provide a nitrogen-containing heterocyclic compound, which contains pyrimidine and benzene ring groups, has different substituents on the benzene ring, does not produce toxic substances such as p-benzoquinone or o-benzoquinone, and is more environmentally friendly. In addition, the compound of the present invention has a large molecular weight, is not easy to discolor and migrate out, and has a good rubber anti-aging effect, and can be applied to more rubber products.

[0006] The present invention is achieved through the following technical solutions:

[0007] A nitrogen-containing heterocyclic compound having the structural formula shown in the following formula A:

[0008]

[0009] Furthermore, the preparation method of the nitrogen-containing heterocyclic compound represented by formula A comprises the following steps:

[0010] 1. 2,5-diaminopyrimidine and 2,6-dimethyl-4-nitrochlorobenzene are subjected to a condensation reaction under the action of a base to obtain intermediate 1 - N2,N5-bis(2,6-dimethyl-4-nitrophenyl)pyrimidine-2,5-diamine;

[0011]

[0012] 2. The intermediate 1 obtained in step 1 and 5-methyl-2-hexanone are reacted with hydrogen in the presence of a catalyst to carry out a reduction condensation reaction to obtain a nitrogen-containing heterocyclic compound represented by formula A;

[0013]

[0014] Furthermore, in step 1, the molar ratio of 2,5-diaminopyrimidine to 2,6-dimethyl-4-nitrochlorobenzene is 1:2.0-2.2, preferably 1:2.1.

[0015] Furthermore, in step 1, the base is an alkaline substance, such as at least one of sodium carbonate, sodium hydroxide, sodium methoxide, and aqueous solutions thereof, preferably sodium hydroxide solution. When the base is added in the form of an aqueous solution, the concentration of the aqueous solution is generally 30%-32%.

[0016] Furthermore, in step 1, the molar ratio of the base to 2,6-dimethyl-4-nitrochlorobenzene is 1 to 1.10:1.

[0017] Furthermore, in step 1, the reaction for preparing the intermediate is carried out in an organic solvent, which may be at least one of toluene, xylene, dimethyl sulfoxide, etc. When the organic solvent is dimethyl sulfoxide, the reaction yield is higher.

[0018] Furthermore, in step 1, preferably, when the base is added in solid form, the organic solvent, 2,5-diaminopyrimidine, and the base are first mixed evenly, and then the solution of 2,6-dimethyl-4-nitrochlorobenzene is added dropwise; when the base is added in the form of an aqueous solution, the organic solvent and 2,5-diaminopyrimidine are first mixed evenly, and then the solution of 2,6-dimethyl-4-nitrochlorobenzene and the aqueous solution of the base are added simultaneously in the form of drops.

[0019] Furthermore, in step 1, the addition time of the 2,6-dimethyl-4-nitrochlorobenzene solution and the alkaline aqueous solution is the same, that is, 20 min to 40 min. The 2,6-dimethyl-4-nitrochlorobenzene solution is a mixture of 2,6-dimethyl-4-nitrochlorobenzene and an organic solvent.

[0020] Furthermore, in step 1, the reaction temperature is 80-110° C., for example, 80° C., 90° C., 100° C., 110° C., and preferably 100° C. The 2,6-dimethyl-4-nitrochlorobenzene solution and the alkaline aqueous solution are both added dropwise at this temperature. After all the raw materials are added, the reaction is continued at this temperature for 5-8 hours, for example, 5 hours, 6 hours, 7 hours, 8 hours, and preferably 6 hours.

[0021] Furthermore, in step 1, after the reaction is completed, water is added to the reaction solution. The addition of water serves to firstly reduce the temperature, secondly dilute the concentration of the reaction mother liquor, making the subsequent acid-base neutralization step simpler and easier to control, and thirdly facilitate the precipitation of intermediate 1. After the addition of water, the temperature is lowered to 40-50°C, and then acid is added to neutralize excess base and unreacted 2,5-diaminopyridine until the product precipitates. After complete crystallization, the product is filtered, washed, and dried to obtain a light yellow intermediate 1.

[0022] Furthermore, in step 1, acid is added to adjust the pH to 8-9. The acid used can be a common inorganic acid such as hydrochloric acid and sulfuric acid. The concentration of the acid solution can be 10-35 wt%.

[0023] Furthermore, in step 2, the molar ratio of intermediate 1 to 5-methyl-2-hexanone is 1:12-18, for example, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, or 1:18.

[0024] Furthermore, in step 2, the catalyst added to the reaction is a catalyst commonly used in hydrogenation reactions, such as skeleton nickel, carbon-based palladium, carbon-based nickel, and mixtures thereof. Preferably, the catalyst is a carbon-based palladium catalyst, i.e., a palladium-carbon catalyst, and the palladium loading in the catalyst is 3-5 wt%.

[0025] Furthermore, in step 2, the amount of catalyst added is 2-6% of the mass of the intermediate 1, for example, 2%, 3%, 4%, 5%, or 6%.

[0026] Furthermore, in step 2, the reaction temperature is 70-90°C, for example, 70°C, 75°C, 80°C, 85°C, 90°C.

[0027] Furthermore, in step 2, the hydrogen pressure is maintained in the range of 1.5-2.0 MPa during the reaction, and the reaction is continued until the hydrogen pressure no longer decreases and the intermediate content is less than or equal to 0.2 wt%.

[0028] Furthermore, in step 2, after the reaction is completed, the catalyst is filtered out of the mother liquor, and the excess ketone and the generated by-products such as alcohol and water are removed by vacuum distillation to obtain the final product.

[0029] Furthermore, the nitrogen-containing heterocyclic compound of the present invention has a good ozone protection effect when used in rubber tire products, is not easy to migrate out or "bloom", and will not oxidize to produce toxic structures. It is a good rubber antioxidant and can be used in various rubber products.

[0030] The present invention has the following beneficial effects:

[0031] 1. The nitrogen-containing heterocyclic compound of the present invention has a unique structure, containing pyrimidine and benzene ring groups. It exhibits excellent ozone protection in rubber products, comparable to that of traditional arylalkyl-p-phenylenediamine antioxidants (such as antioxidant 4020). The presence of different substituents on the benzene ring prevents the production of toxic p-benzoquinone or o-benzoquinone compounds, making it more environmentally friendly and highly valuable in the anti-aging of rubber materials.

[0032] 2. The nitrogen-containing heterocyclic compound of the present invention has a large molecular weight and is not easy to discolor and migrate out when used in rubber products. It can significantly improve the tire side discoloration phenomenon caused by traditional p-phenylenediamine antioxidants, and can better ensure the good stability, low migration rate and good late anti-aging performance of the antioxidant, thereby extending the service life of rubber products and avoiding environmental pollution.

[0033] 3. The antioxidant of the present invention has a simple preparation process, high product yield and stable product quality, and is a promising alternative antioxidant to antioxidant 4020. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The product of Example 1 of the present invention 1 H NMR spectrum.

[0035] Figure 2 The product of Example 1 of the present invention 13 C NMR spectrum.

[0036] Figure 3 The results of the static ozone aging test for 72 hours for different rubber compounds are shown in the figure.

[0037] Figure 4The results of the dynamic ozone aging test for 72 hours for different rubber compounds are shown in the figure. DETAILED DESCRIPTION

[0038] The following description of exemplary embodiments of the present invention includes various details to facilitate understanding, which should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for the sake of clarity and conciseness, descriptions of well-known functions, operations, and structures are omitted from the following description.

[0039] Unless otherwise defined, technical and scientific terms used in this specification have the same meanings as commonly understood by those skilled in the art. Although methods and materials similar or equivalent to those described herein can be used in experiments or applications, the present invention describes the materials and methods below. In the event of conflict, the present specification, including definitions, will control.

[0040] In the following examples, unless otherwise specified, the concentrations are all expressed in mass percentage.

[0041] Example 1

[0042] Step 1: Preparation of intermediate nitrate:

[0043] In a 2L three-necked flask, 312 g of toluene solvent, 55.1 g (0.5 mol) of 2,5-diaminopyrimidine, and 111.3 g (1.05 mol) of solid base sodium carbonate were added, stirred, and heated to 80°C. A toluene solution of 556.09 g of 2,6-dimethyl-4-nitrochlorobenzene was added dropwise using a feed pump, wherein the mass of 2,6-dimethyl-4-nitrochlorobenzene was 185.61 g (1 mol). The addition time was 30 min. After the addition was completed, stirring was continued. The residual amount of 2,5-diaminopyrimidine was detected to be less than 0.2% (HPLC), and the reaction was considered complete. The reaction time was about 8 h. 751 g of water was added to the reaction solution, and the temperature was kept at 50°C. 31% hydrochloric acid was slowly added dropwise to adjust the pH to 8-9. The solution was cooled to room temperature to allow the product to precipitate completely. The product was filtered to obtain a light yellow intermediate 200.57 g in a yield of 98.22% based on 2,5-diaminopyrimidine.

[0044] The same steps as above were repeated to obtain the desired amount of the intermediate.

[0045] Step 2: Synthesis of antioxidant:

[0046] 204.2 g (0.5 mol) of the intermediate nitrate, 856.43 g (7.5 mol) of 5-methyl-2-hexanone, and 4.08 g of a 3% palladium-supported carbon-based palladium catalyst were transferred to a 2L reactor. After complete gas replacement and ensuring safety, the temperature was raised to 80°C and filled with hydrogen at 1.5-2.0 MPa. The reaction was maintained until the reaction no longer consumed hydrogen and the intermediate content was less than 0.2% (HPGC), indicating completion. After the reaction was complete, the hydrogenation mother liquor was filtered at 50°C and the remaining ketone, alcohol, and water were removed by vacuum distillation to obtain 265.31 g of product, with a yield of 97.39% based on the intermediate.

[0047] Example 2

[0048] Step 1: Preparation of intermediate nitrate:

[0049] In a 2L three-necked flask, 312 g of toluene solvent, 55.1 g (0.5 mol) of 2,5-diaminopyrimidine, and 42 g (1.05 mol) of granular sodium hydroxide were added, stirred, and heated to 110°C. A toluene solution of 556.09 g of 2,6-dimethyl-4-nitrochlorobenzene was added dropwise using a feed pump, wherein the mass of 2,6-dimethyl-4-nitrochlorobenzene was 194.63 g (1.05 mol). The addition time was 30 min. After the addition was completed, stirring was continued. The residual amount of 2,5-diaminopyrimidine was detected to be less than 0.2% (HPLC), and the reaction was considered complete. The reaction time was about 7 h. 751 g of water was added to the reaction solution, which was kept warm at 50°C. 31% hydrochloric acid was slowly added dropwise to adjust the pH to 8-9. The solution was cooled to room temperature to allow the product to precipitate completely. The product was filtered to obtain 202.74 g of a light yellow intermediate with a yield of 99.28% based on 2,5-diaminopyrimidine.

[0050] The same steps as above were repeated to obtain the desired amount of the intermediate.

[0051] Step 2: Synthesis of antioxidant:

[0052] 204.2 g (0.5 mol) of the intermediate nitrate, 685.08 g (6 mol) of 5-methyl-2-hexanone, and 4.08 g of a skeletal nickel catalyst were transferred to a 2 L reactor. After complete gas replacement and ensuring safety, the temperature was raised to 70° C. and hydrogen was introduced at 1.5-2.0 MPa and maintained until the reaction no longer consumed hydrogen and the intermediate content was less than 0.2% (HPGC), indicating completion. After the reaction was complete, the hydrogenation mother liquor was filtered at 50° C. and the remaining ketone, alcohol, and water were removed by vacuum distillation to obtain 267.65 g of the product of the present invention, with a yield of 98.25% based on the intermediate.

[0053] Example 3

[0054] Step 1: Preparation of intermediate nitrate:

[0055] 312 g of dimethyl sulfoxide solvent was added to a 2L three-necked flask, 55.10 g (0.5 mol) of 2,5-diaminopyrimidine was added, stirred, and heated to 100 ° C. 131.25 g of 32% sodium hydroxide solution (1.05 mol as sodium hydroxide) and 556.09 g of 2,6-dimethyl-4-nitrochlorobenzene in toluene solution, wherein the mass of 2,6-dimethyl-4-nitrochlorobenzene was 194.63 g (1.05 mol), were added dropwise simultaneously using a feed pump, and the addition time was 30 min. After the addition was completed, stirring was continued. The remaining amount of 2,5-diaminopyrimidine was detected to be less than 0.2% (HPLC), and the reaction was considered complete. The reaction time was about 6 h. Add 661.75 g of water to the reaction solution, keep warm at 50°C, slowly add 31% hydrochloric acid dropwise to adjust the pH to 8-9, cool to room temperature to allow the product to fully precipitate, and filter to obtain 203.13 g of a light yellow intermediate with a yield of 99.47% based on 2,5-diaminopyrimidine.

[0056] The same steps as above were repeated to obtain the desired amount of the intermediate.

[0057] Step 2: Synthesis of antioxidant:

[0058] 204.2 g (0.5 mol) of the intermediate nitrate, 856.43 g (7.5 mol) of 5-methyl-2-hexanone, and 4.08 g of a skeletal nickel catalyst were transferred to a 2 L reactor. After complete gas replacement and ensuring safety, the temperature was raised to 90° C. and hydrogen was introduced at 1.5-2.0 MPa and maintained until the reaction no longer consumed hydrogen and the intermediate content was less than 0.2% (HPGC), indicating completion. After the reaction was complete, the hydrogenation mother liquor was filtered at 50° C. and the remaining ketone and the generated alcohol and water were removed by vacuum distillation to obtain 268.65 g of the product of the present invention, with a yield of 98.62% based on the intermediate.

[0059] Comparative Example 1

[0060] Step 1: Preparation of intermediate nitrate:

[0061] 312 g of toluene solvent was added to a 2L three-necked flask, 55.10 g (0.5 mol) of 2,5-diaminopyrimidine was added, stirred, and heated to 60°C. 131.25 g of 32% sodium hydroxide solution (1.05 mol as sodium hydroxide) and 556.09 g of 2,6-dimethyl-4-nitrochlorobenzene in toluene solution, wherein the mass of 2,6-dimethyl-4-nitrochlorobenzene was 194.63 g (1.05 mol), were added dropwise simultaneously using a feed pump, and the addition time was 30 min. After the addition was completed, stirring was continued. The residual amount of 2,5-diaminopyrimidine was detected to be less than 0.2% (HPLC), and the reaction was considered complete. The reaction time was about 13 h. Add 661.75 g of water to the reaction solution, keep warm at 50°C, slowly add 31% hydrochloric acid dropwise to adjust the pH to 8-9, cool to room temperature to allow the product to fully precipitate, and filter to obtain 159.65 g of a light yellow intermediate. The yield is 78.18% based on 2,5-diaminopyrimidine.

[0062] Comparative Example 2

[0063] To a 2L three-necked flask, 312g of 1,4-dioxane solvent and 55.10g (0.5 mol) of 2,5-diaminopyrimidine were added, stirred, and heated to 60°C. 131.25g of 32% sodium hydroxide solution (1.05 mol as sodium hydroxide) and 556.09g of a toluene solution of 2,6-dimethyl-4-nitrochlorobenzene (194.63g (1.05 mol) of 2,6-dimethyl-4-nitrochlorobenzene) were added dropwise simultaneously using a feed pump over 30 minutes. After the addition was complete, stirring was continued, and the reaction lasted approximately 13 hours. Testing revealed that approximately 80% of the 2,5-diaminopyrimidine remained unreacted.

[0064] Performance Verification

[0065] 1. Compound formulation and preparation

[0066] Rubber formula (parts by weight): 45 parts natural rubber (NR), 55 parts butadiene rubber (BR), 45 parts carbon black (N330), 4.375 parts zinc oxide (ZnO-80), 2 parts SA stearate, 1.8 parts H3241 protective wax, 1.875 parts S-80 vulcanizing agent, 1 part NS-80 accelerator, 3 parts antioxidant (the product of the present invention in Example 3). Meanwhile, the product of the present invention in Example 3 was replaced with antioxidant 4020 for comparison, and a blank control was used without the antioxidant.

[0067] The preparation of the rubber compound is divided into a one-stage mixing process and a two-stage mixing process. The specific one-stage mixing process is as follows: weigh the raw materials according to the formula ratio, and mix 45 parts of natural rubber NR, 55 parts of butadiene rubber BR, 45 parts of carbon black N330, 4.375 parts of zinc oxide ZnO-80, 2 parts of stearic acid SA, and protective wax H3241. 1.8 parts of propylene glycol and 3 parts of antioxidant are added to an internal mixer, the rotor speed is 60-70 rpm, the pressure is 19-20 MPa, the temperature is increased at a rate of 5-10°C / 10 minutes, the temperature is increased to 100-120°C, the temperature is kept at this temperature for 5-10 minutes, the temperature is further increased to 180°C, and the rubber is discharged to obtain a first-stage rubber mix; the second-stage mixing process is specifically as follows: the first-stage rubber mix is ​​added to the internal mixer, the vulcanizing agent S-80 and the accelerator NS-80 are added, and the mixture is mixed at a pressure of 8-10 MPa and a temperature of 70-80°C for 1-2 minutes at a speed of 10-15 rpm. After completion, the rubber compound can be obtained.

[0068] 2. Test methods for various performance parameters of rubber compounds

[0069] Processing performance test: Using a Mooney viscometer, a scorch test was conducted in accordance with the national standard GB / T 1233-92.

[0070] Vulcanization characteristics: The test was conducted using a P3555 B2 disc vulcanizer produced by Beijing Huanfeng Rubber and Plastic Machinery Manufacturing Plant in accordance with GB / T98691997. The test temperature was 160°C and the test time was 60 minutes.

[0071] Mechanical Properties: The tensile properties of the vulcanized rubber were measured using a CMT 4104 electronic tensile testing machine produced by Shenzhen Xinsansi Material Testing Co., Ltd. in accordance with GB / T 528-2009. The compression set was measured at 100°C for 72 h using a 29.0 mm × 12.5 mm cylindrical specimen in accordance with GB / T 7759-1996, with a pre-compression ratio of 25%.

[0072] Ozone resistance: Ozone resistance test is carried out according to GB / T 11206-2009 "Rubber aging test - surface cracking method".

[0073] 3. Experimental Results

[0074] 1. The processing characteristics of each rubber compound are shown in Table 1 below:

[0075] Table 1 Processing characteristics of rubber compounds

[0076] Compound name t5 / min Mn / Mv Blank control 30.84 63.85 4020 28.27 46.83 Example 1 28.28 46.87

[0077] As can be seen from Table 1, compared with the blank control, the addition of the product of the present invention shortens the scorch time of the rubber mix, reduces the Mooney viscosity, and improves the processing performance; compared with the antioxidant 4020 product, the product of the present invention has similar processing performance and equivalent processing safety to 4020.

[0078] 2. The vulcanization characteristics of the rubber compound are shown in Table 2 below:

[0079] Table 2 Vulcanization characteristics of rubber compounds

[0080] Compound name MH / dN-M ML / dN-M (MH-ML) / dN-M tc10 / s tc90 / s Blank control 6.01 0.74 5.31 337 832 4020 6.20 0.58 5.62 301 698 Example 1 6.58 0.69 5.99 288 679

[0081] As can be seen from Table 2, compared with the blank sample, the addition of the product of the embodiment of the present invention improves the vulcanization rate and the degree of vulcanization crosslinking of the rubber mix.

[0082] 3. The mechanical properties of the rubber are shown in Table 3 and Table 4 below:

[0083] Table 3 Mechanical properties before aging test

[0084] Blank control 4020 Example 1 Tensile strength / MPa 18.43 21.24 20.58 M100 / MPa 1.68 1.98 2.16 M300 / MPa 6.86 7.56 7.79 Elongation at break / % 619 618 621

[0085] Table 4 Mechanical properties after aging test

[0086] Blank control 4020 Example 1 Tensile strength / MPa 11.57 13.11 14.19 Tensile strength retention / % 62.8 61.72 68.95 M100 / MPa 4.57 5.23 5.36 M300 / MPa - 22.20 22.31 Elongation at break / % 139 212 229 Retention rate of elongation at break / % 22.46 34.30 36.88

[0087] From Tables 3 and 4, it can be seen that before the aging experiment, compared with the blank control, the addition of antioxidant 4020 or the product of the present invention to the rubber material improved the tensile strength and modulus of the vulcanized rubber. After the aging experiment, the product of the present invention still has good resistance to thermal oxidative aging, and the performance pattern after thermal oxidative aging remains consistent with that before aging.

[0088] 4. Ozone resistance of rubber Figure 3 and Figure 4 As shown, Figure 3 This is the result of the static ozone aging test for 72 hours for the blank control, antioxidant 4020, and the rubber compound obtained from the product of the present invention. Figure 4 The figure is a 72h dynamic ozone aging test result of blank control, antioxidant 4020 and the rubber compound obtained by the product of the present invention. Figure 3 and Figure 4 As can be seen, the dynamic ozone performance of the rubber compound containing the product of the present invention is comparable to that of the rubber compound containing 4020. However, the addition of the product of the present invention improves the rubber compound's discoloration resistance, making it less prone to blooming and maintaining surface discoloration over long-term use. In summary, the high-molecular-weight novel antioxidant provided by the present invention not only has excellent ozone protection but also effectively solves the problem of organic antioxidants easily migrating and discoloring, demonstrating superior anti-aging effects on rubber materials.

[0089] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been presented as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to the technical contents disclosed above without departing from the scope of the technical solution of the present invention. Any simple modification, equivalent change and modification of the above embodiments based on the technical essence of the present invention that does not depart from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A nitrogen-containing heterocyclic compound, characterized in that It has the structural formula shown in the following formula A:

2. A method for preparing the nitrogen-containing heterocyclic compound according to claim 1, characterized in that: The following steps are involved: (1) 2,5-diaminopyrimidine and 2,6-dimethyl-4-nitrochlorobenzene are subjected to a condensation reaction in the presence of a base to obtain intermediate 1; (2) The intermediate 1 obtained in step (1) is reacted with 5-methyl-2-hexanone by introducing hydrogen gas in the presence of a catalyst to carry out a reduction condensation reaction to obtain a nitrogen-containing heterocyclic compound represented by formula A.

3. The preparation method according to claim 2, characterized in that In step (1), the molar ratio of 2,5-diaminopyrimidine to 2,6-dimethyl-4-nitrochlorobenzene is 1:2.0-2.2; preferably, in step (1), the molar ratio of the base to 2,6-dimethyl-4-nitrochlorobenzene is 1-1.10:

1.

4. The preparation method according to claim 2 or 3, characterized in that In step (1), the base is an alkaline substance, and the alkaline substance is selected from at least one of sodium carbonate, sodium hydroxide, sodium methoxide and their aqueous solutions.

5. The preparation method according to claim 4, characterized in that In step (1), when the base is added in solid form, the organic solvent, 2,5-diaminopyrimidine, and the base are first mixed uniformly, and then the solution of 2,6-dimethyl-4-nitrochlorobenzene is added dropwise; when the base is added in the form of an aqueous solution, the organic solvent and 2,5-diaminopyrimidine are first mixed uniformly, and then the solution of 2,6-dimethyl-4-nitrochlorobenzene and the aqueous solution of the base are added dropwise; Preferably, in step (1), the 2,6-dimethyl-4-nitrochlorobenzene solution and the alkaline aqueous solution are added dropwise for the same time, that is, for 20 min to 40 min; Preferably, in step (1), the organic solvent is preferably at least one of toluene, xylene, and dimethyl sulfoxide.

6. The preparation method according to claim 2, characterized in that In step (1), the reaction temperature is 80-110°C.

7. The preparation method according to claim 2, characterized in that In step (2), the molar ratio of intermediate 1 to 5-methyl-2-hexanone is 1:12-18.

8. The preparation method according to claim 2, characterized in that In step (2), the catalyst is at least one of skeleton nickel, skeleton copper, carbon-based palladium, and carbon-based nickel, preferably carbon-based palladium; preferably, the amount of catalyst added is 2-6% of the mass of the intermediate 1.

9. The preparation method according to claim 2, characterized in that In step (2), the reaction temperature is 70-90° C.; preferably, in step (2), the hydrogen pressure is maintained in the range of 1.5-2.0 MPa during the reaction, and the reaction is continued until the hydrogen pressure no longer decreases and the intermediate content is less than or equal to 0.2 wt%.

10. Use of the nitrogen-containing heterocyclic compound according to claim 1 in rubber products, preferably, the nitrogen-containing heterocyclic compound is used as a rubber antioxidant.

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