A p-phenylenediamine compound, its preparation method and application

Abstract

The present invention discloses a p-phenylenediamine compound, a preparation method thereof and an application thereof. The compound is obtained by subjecting 2,4-diaminodiphenylamine and a ketone to a hydrogenation reaction in the presence of a catalyst. Compared with the current mainstream antioxidant 6PPD, the compound of the present invention has good anti-dynamic / static ozone protection performance, good anti-dynamic fatigue performance and anti-migration discoloration performance; the tire added with the compound of the present invention will not produce residues of toxic p-benzoquinone structural substances during use, is more environmentally friendly, is an ideal substitute for antioxidant 6PPD, has good economic and social benefits, and has a broad market prospect.

Description

Technical Field

[0001] The present invention relates to a p-phenylenediamine compound, and particularly to a p-phenylenediamine compound that can replace antioxidant 6PPD. It also relates to the preparation method of this p-phenylenediamine compound and its application as a rubber antioxidant, belonging to the field of fine chemical technology. Background Art

[0002] The p-phenylenediamine antioxidant 6PPD is currently the product with the best application effect. However, in 2023, the tire industry received a report published by the University of Washington and the Washington Rainwater Center in the United States. The report claims that a 6PPD conversion by-product called 6PPD-Q is toxic to cod and may cause the urban runoff death syndrome of this species. The EU and the United States have expressed concerns about 6PPD products and may be banned in the near future. Enterprises in the rubber auxiliaries industry are seeking alternative substances to 6PPD. The mechanism of the formation of p-benzoquinone-like substances from antioxidant 6PPD is as follows:

[0003]

[0004] Therefore, researching and developing a new type of environmentally friendly and non-toxic rubber antioxidant has become an urgent task at present, and it will also surely have broad market prospects and economic and social benefits. Summary of the Invention

[0005] The purpose of the present invention is to provide a p-phenylenediamine compound. Through experiments, it is verified that this compound has good anti-dynamic / static ozone protection performance, good anti-dynamic fatigue performance and anti-migration discoloration performance compared with the current mainstream antioxidant 6PPD; and this compound will not produce toxic p-benzoquinone-like structural substance residues during use, is more environmentally friendly and is an ideal substitute for antioxidant 6PPD.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A p-phenylenediamine compound having the structural formula shown in the following formula (1):

[0008]

[0009] In formula (1), R1 can be the same as or different from R2, and R1 and R2 are each independently selected from hydrogen, cyclohexyl, cyclooctyl, 2-cyclohexylethyl, 2-phenylethyl, benzyl, isopropyl, 1,3-dimethylbutyl, 1,4-dimethylpentyl, etc.

[0010] Exemplarily, the p-phenylenediamine compound of the present invention can be one of the structures shown in Table 1 below:

[0011]

[0012]

[0013] Preferably, both R1 and R2 are 1,3-dimethylbutyl.

[0014] Furthermore, the present invention also provides a method for preparing the above-mentioned p-phenylenediamine compound, which includes: subjecting 2,4-diaminodiphenylamine and the corresponding ketone to a hydrogenation reaction in the presence of a catalyst to obtain the p-phenylenediamine compound.

[0015] Furthermore, the structure of the ketone varies according to the structure of the finally obtained p-phenylenediamine compound, and examples thereof include: 4-methyl-2-pentanone, 5-methyl-2-hexanone, acetone, cyclohexanone, etc. The molar ratio of 2,4-diaminodiphenylamine to the ketone is 1:(10 - 15), such as 1:10, 1:11, 1:12, 1:13, 1:14, 1:15.

[0016] Furthermore, the catalyst for the reaction of 2,4-diaminodiphenylamine and the ketone is a catalyst commonly used in catalytic hydrogenation reactions, such as metal catalysts, and examples thereof include palladium on carbon, platinum, rhodium, Raney nickel, copper alloy, etc.

[0017] Furthermore, the dosage of the catalyst is 1% - 5% of the mass of 2,4-diaminodiphenylamine, such as 1%, 2%, 3%, 4%, 5%.

[0018] Furthermore, the reaction temperature of 2,4-diaminodiphenylamine and the ketone is 70 - 180 °C, such as 70 °C, 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C.

[0019] Furthermore, during the reaction, 2,4-diaminodiphenylamine, the ketone and the catalyst are mixed, and then hydrogen is introduced for the reaction. The pressure of the introduced hydrogen is 2 - 4 Mpa. During the reaction process, when the hydrogen pressure drops to 1 Mpa, hydrogen is recharged to 2 - 4 Mpa. When the pressure remains unchanged at 1 MPa, the reaction is considered complete.

[0020] Furthermore, the 2,4-diaminodiphenylamine can be directly purchased or prepared by oneself. 2,4-diaminodiphenylamine can be obtained by the catalytic hydrogenation reaction of 2,4-dinitrodiphenylamine.

[0021] Further, when preparing 2,4-diaminodiphenylamine, 2,4-dinitrodiphenylamine and a catalyst are mixed, and then hydrogen is introduced for reaction. The reaction temperature is 70 - 120°C, such as 70°C, 80°C, 90°C, 100°C, 110°C, 120°C. The pressure of the introduced hydrogen is 2 - 4 Mpa. During the reaction process, when the hydrogen pressure drops to 1 Mpa, hydrogen is recharged to 2 - 4 Mpa. When the pressure remains unchanged at 1 MPa, the reaction is regarded as completed. The catalyst used is a catalyst commonly used in catalytic hydrogenation reactions, such as metal catalysts, and examples include palladium-carbon, platinum, rhodium, Raney nickel, copper alloy, etc. The catalyst dosage is 3% - 5% of the mass of the raw material 2,4-dinitrodiphenylamine, such as 3%, 4%, 5%.

[0022] Further, the 2,4-dinitrodiphenylamine can be directly purchased or prepared by oneself. For example, it can be obtained by reacting aniline and 2,4-dinitrochlorobenzene in the presence of an acid-binding agent.

[0023] Further, when preparing 2,4-dinitrodiphenylamine, the reaction temperature is 120 - 160°C, such as 120°C, 130°C, 140°C, 150°C, 160°C. The molar ratio of aniline to 2,4-dinitrochlorobenzene is (1 - 1.5):1, such as 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1. The acid-binding agent used is an inorganic base, such as at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and preferably potassium carbonate. The amount of the acid-binding agent is 30 - 40% of the mass of 2,4-dinitrochlorobenzene, such as 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%. The reaction is carried out in the presence of an organic solvent, and the organic solvent can be toluene, etc. During the reaction process, the formed water is continuously separated out.

[0024] In a specific embodiment of the present invention, a specific preparation method is disclosed, including the following steps:

[0025] a. React aniline and 2,4-dinitrochlorobenzene in the presence of an acid-binding agent to obtain 2,4-dinitrodiphenylamine. The reaction formula is as follows:

[0026]

[0027] b. Carry out catalytic hydrogenation reaction on 2,4-dinitrodiphenylamine to obtain 2,4-diaminodiphenylamine. The reaction formula is as follows:

[0028]

[0029] c. Carry out hydrogenation reaction on 2,4-diaminodiphenylamine and the corresponding ketone in the presence of a catalyst to obtain a p-phenylenediamine compound. The reaction formula is as follows:

[0030]

[0031] The p-phenylenediamine compound of the present invention can not only achieve a good ozone protection effect, but also does not produce toxic and harmful p-benzoquinone substances. It is a good substitute for 6PPD. Therefore, the application of this p-phenylenediamine compound as a rubber antioxidant is also within the protection scope of the present invention.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. Compared with antioxidant 6PPD, the benzene ring at the alkane end of the compound of the present invention has one more aminoalkyl group, and the ozone protection efficiency is better;

[0034] 2. Compared with antioxidant 6PPD, due to the benzene ring at the alkane end of the compound of the present invention having one more aminoalkyl group, there will be no residue of toxic and harmful p-benzoquinone substances in the rubber compound, which is greener, more environmentally friendly and non-toxic.

[0035] 3. Through the optimization and screening of aminoalkyl substituents, the present invention can better improve the anti-aging effect of rubber.

[0036] 4. The compound of the present invention is a good substitute for 6PPD and has a broad market prospect. Specific Embodiments

[0037] The present invention will be described in detail below through specific examples. However, the uses and purposes of these exemplary embodiments are only used to illustrate the present invention, and do not constitute any form of limitation to the actual protection scope of the present invention, nor will the protection scope of the present invention be limited thereto.

[0038] Example 1

[0039] First step, synthesis of intermediate 2,4-dinitrodiphenylamine

[0040] Weigh 32.6 grams (0.35 moles) of aniline, 60.8 grams (0.3 moles) of 2,4-dinitrochlorobenzene, 380 grams of toluene, and 21.3 g of acid-binding agent potassium carbonate, and put them into a 1000-milliliter reaction device equipped with a water separator. Keep the temperature at 120 - 140 °C for reflux reaction. When no more water droplets are formed in the fractionating column, the reaction is considered complete. Then, toluene and excess aniline are distilled out under reduced pressure. The remaining material is poured into cold water and stirred to precipitate solids. The solid is filtered and washed 3 - 4 times with 300 milliliters of hot water. The filter cake is dried in vacuum at 70 - 80 °C to obtain 76.2 grams of 2,4-dinitrodiphenylamine, and the yield based on 2,4-dinitrochlorobenzene is 98%.

[0041] Second step, synthesis of intermediate 2,4-diaminodiphenylamine

[0042] Weigh 64.8 g (0.25 mol) of 2,4-dinitrodiphenylamine (Intermediate 1), dissolve it in 600 g of methanol and add it to a 2 L autoclave. Weigh 3.2 g of palladium-carbon and add it to the autoclave. First, displace the air in the autoclave with nitrogen three times, and then displace it with nitrogen three more times. When the temperature is raised to 80 °C, introduce hydrogen until the pressure reaches 3 MPa. When the pressure in the autoclave drops to 1 MPa, recharge hydrogen until the pressure reaches 3 MPa. When the pressure in the autoclave remains at 1 MPa and no longer changes, it is considered that the reaction is complete. Then, cool down and release the pressure, and discharge the reaction solution. Filter to remove the catalyst (which can be recycled 2 - 3 times). Rotavaporize the filtrate to remove the solvent methanol, pour it out and cool to obtain 49.1 g of 2,4-diaminodiphenylamine, which is 98.6% based on 2,4-dinitrodiphenylamine.

[0043] The third step, synthesis of the novel p-phenylenediamine antioxidant

[0044] Weigh 29.9 g (0.15 mol) of 2,4-diaminodiphenylamine, 1.3 g of palladium-carbon and 165.3 g of 4-methyl-2-pentanone (1.65 mol) and add them to a 1 L autoclave. First, displace the air in the autoclave with nitrogen three times, and then displace it with nitrogen three more times. When the temperature is raised to 80 °C, introduce hydrogen until the pressure reaches 3 MPa. When the pressure in the autoclave drops to 1 MPa, recharge hydrogen until the pressure reaches 3 MPa. When the pressure in the autoclave remains at 1 MPa and no longer changes, it is considered that the reaction is complete. Then, cool down and release the pressure, and discharge the reaction solution. Filter to remove the catalyst (which can be recycled 2 - 3 times). Rotavaporize the filtrate to remove the excess 4-methyl-2-pentanone and the by-product 4-methyl-2-pentanol to obtain 52.5 g of the novel antioxidant product of the present invention, with a yield of 95.4% based on 2,4-diaminodiphenylamine. The structural formula of the obtained antioxidant is as follows:

[0045]

[0046] Example 2

[0047] The methods of the first and second steps are the same as those in Example 1, or purchased from the market.

[0048] The third step, the synthesis method of the novel p-phenylenediamine antioxidant is as follows:

[0049] Weigh 29.9 g (0.15 mol) of 2,4-diaminodiphenylamine, 1.0 g of nickel and 205.5 g of 5-methyl-2-hexanone (1.8 mol) and add them to a 1 L autoclave. First, displace the air in the autoclave with nitrogen three times, and then displace it with nitrogen three more times. When the temperature is raised to 90 °C, introduce hydrogen until the pressure reaches 4 MPa. When the pressure in the autoclave drops to 1 MPa, recharge hydrogen until the pressure reaches 4 MPa. When the pressure in the autoclave remains at 1 MPa without change, it is considered that the reaction is complete. Then, cool down and release the pressure, and discharge the reaction solution. Filter to remove the catalyst (which can be recycled 2 - 3 times). Rotate evaporate the filtrate to remove the excess 5-methyl-2-hexanone and the by-product 5-methyl-2-hexanol, obtaining 56.4 g of the novel antioxidant product of the present invention, with a yield of 95.2% based on 2,4-diaminodiphenylamine. The structural formula is as follows:

[0050]

[0051] Example 3

[0052] The methods of the first and second steps are the same as those in Example 1, or purchased from the market.

[0053] In the third step, the synthesis method of the novel p-phenylenediamine antioxidant is as follows:

[0054] Weigh 29.9 g (0.15 mol) of 2,4-diaminodiphenylamine, 1.4 g of platinum and 130.7 g of acetone (2.25 mol) and add them to a 1 L autoclave. First, displace the air in the autoclave with nitrogen three times, and then displace it with nitrogen three more times. When the temperature is raised to 80 °C, introduce hydrogen until the pressure reaches 3.5 MPa. When the pressure in the autoclave drops to 1 MPa, recharge hydrogen until the pressure reaches 3.5 MPa. When the pressure in the autoclave remains at 1 MPa without change, it is considered that the reaction is complete. Then, cool down and release the pressure, and discharge the reaction solution. Filter to remove the catalyst (which can be recycled 2 - 3 times). Rotate evaporate the filtrate to remove the excess acetone and the by-product isopropanol, obtaining 41.9 g of the novel antioxidant product of the present invention, with a yield of 98.7% based on 2,4-diaminodiphenylamine. The structural formula is as follows:

[0055]

[0056] Example 4

[0057] The methods of the first and second steps are the same as those in Example 1, or purchased from the market.

[0058] In the third step, the synthesis method of the novel p-phenylenediamine antioxidant is as follows:

[0059] Weigh 29.9 g (0.15 mol) of 2,4-diaminodiphenylamine, 1.4 g of copper-zinc alloy and 186.4 g of cyclohexanone (1.9 mol), and add them into a 1 L autoclave. First, displace the air in the autoclave with nitrogen three times, and then displace it with nitrogen three more times. When the temperature is raised to 180 °C, introduce hydrogen until the pressure reaches 4 MPa. When the pressure in the autoclave drops to 1 MPa, recharge hydrogen until the pressure reaches 4 MPa. When the pressure in the autoclave remains unchanged at 1 MPa, it is regarded as the completion of the reaction. Then, cool down and release the pressure, and discharge the reaction solution. Filter to remove the catalyst (which can be recycled 2-3 times). Evaporate the filtrate by rotary evaporation to remove the excessive cyclohexanone and by-product cyclohexanol, obtaining 50.7 g of the novel antioxidant product of the present invention, with a yield of 96.8% based on 2,4-diaminodiphenylamine. The structural formula is as follows:

[0060]

[0061] To verify the application effect of the present invention, the novel antioxidants synthesized in Examples 1-4 above were compared with antioxidant 6PPD in application, as follows:

[0062] 1. Experiment

[0063] 1.1 Main experimental raw materials

[0064] Natural rubber NR, grade SVR20, domestic product from Vietnam; cis-butadiene rubber BR, grade 9000, product of Yueyang Petrochemical General Factory, China; carbon black N330, product of Tianjin Yiborui Chemical Co., Ltd.; accelerator NS, insoluble sulfur HD0T20 and rubber protection wax H7075, products of Shandong Yanggu Huatai Chemical Co., Ltd.

[0065] 1.2 Formulation

[0066] Parts by weight: 50 parts of natural rubber NR, 50 parts of cis-butadiene rubber BR, 50 parts of carbon black N330, 8 parts of naphthenic oil, 1.5 parts of rubber protection wax H7075, 1.5 parts of insoluble sulfur HD0T20, 2 parts of stearic acid, 3 parts of zinc oxide, 1.5 parts of accelerator NS, 3 parts of antioxidant for testing (varied in variety, using the antioxidant prepared in the examples of the present invention and antioxidant 6PPD respectively), and 1 part of antioxidant RD. At the same time, a rubber compound without the antioxidant for testing was used as a blank control.

[0067] 1.3 Main experimental equipment

[0068] XK-160 Banbury mixer, a product of Dalian Chengxin Rubber and Plastic Machinery Co., Ltd.; HS-100T-RTMO Flat Vulcanizing Machine, a product of Jiaxin Electronic Equipment Technology (Shenzhen) Co., Ltd.; X(S)M-1.5 Laboratory Internal Mixer, a product of Qingdao Kegao Rubber and Plastic Machinery Co., Ltd.; LRHS-101 Ozone Aging Test Chamber, a product of Shanghai Linpin Instrument Co., Ltd.; VHX7000 Digital Microscope, a product of Keyence Corporation of Japan.

[0069] 1.4 Rubber Compound Mixing Process

[0070] The rotor speed of the first-stage mixing is 40 r·min-1. The raw rubber is first plasticized for 1 min, and then stearic acid, zinc oxide, rubber protective wax, anti-aging agent, naphthenic oil and carbon black are added. Press the weight for 35 s, lift the weight for 10 s, press the weight for 45 s, lift the weight for 10 s, and discharge the rubber (145 °C).

[0071] The rotor speed of the second-stage mixing is 48 r·min-1. The first-stage mixed rubber, insoluble sulfur, and accelerator are added. Press the weight for 80 s, lift the weight for 10 s, press the weight for 55 s, and discharge the rubber (110 °C).

[0072] 1.5 Anti-Ozone Performance Test

[0073] The anti-ozone performance is tested according to the standards of GBT7762-2003 Rubber, vulcanized or thermoplastic - Resistance to ozone cracking - Static tensile test and GB / T13642-2015 Rubber, vulcanized or thermoplastic - Resistance to ozone cracking - Dynamic tensile test.

[0074] The grading of the test specimens is carried out according to Tables 1 and 2 below:

[0075]

[0076]

[0077] The cracking grades are evaluated according to the grades listed in Tables 1 and 2 respectively, and the combined result is used. The evaluation of the cracking grade is mainly based on the crack width and supplemented by the crack density. The width grade and the density grade are combined to indicate the test result. Note: If the cracking width is grade 2 and the cracking density is grade c, then the cracking grade of the test specimen is 2c.

[0078] 1.6 Mechanical Properties Test of Vulcanized Rubber

[0079] The mechanical properties of vulcanized rubber are tested according to GB / T3512-2014 Rubber, vulcanized or thermoplastic - Accelerated ageing and heat resistance tests in air.

[0080] 1.7 Color Resistance of Vulcanized Rubber

[0081] The color resistance of vulcanized rubber is detected according to GB / T 528-2009.

[0082] 2. Test Results

[0083] 2.1 Dynamic / Static Ozone Aging Test Data of Vulcanizates

[0084] Table 3 Test Data of the Dynamic / Static Ozone Resistance Performance of the Compounds

[0085]

[0086]

[0087] 2.2 Mechanical Properties of Vulcanizates

[0088] Table 4 Test Data of the Heat-Oxygen Aging Resistance and Fatigue Resistance Performance of the Compounds

[0089]

[0090]

[0091] 2.3 Discoloration Resistance Performance of Vulcanizates

[0092] Table 5 Discoloration Detection of Vulcanizates

[0093] Sample Name Blank 6PPD Example 1 Example 2 Example 3 Example 4 Level Level 1 Level 4 Level 2 Level 3 Level 3 Level 3

[0094] From the data in Table 3, Table 4 and Table 5 above, the novel antioxidant of the present invention has the following advantages compared with the mainstream antioxidant 6PPD in the market:

[0095] 1. It has better dynamic / static ozone protection performance, and the novel antioxidant in Example 1 has the best performance;

[0096] 2. It has better heat-oxygen aging resistance and dynamic fatigue performance, and the novel antioxidant in Example 1 has the best performance;

[0097] 3. It has better migration resistance and discoloration resistance performance, and the novel antioxidant in Example 1 has the best performance.

[0098] In addition, the novel antioxidant of the present invention does not produce residues of toxic substances such as p-benzoquinone, is green and environmentally friendly, and is therefore a good substitute for 6PPD.

[0099] Finally, it should be noted that the above-mentioned is only the preferred novel antioxidant synthesized from part 2,4-diaminodiphenylamine (or the mixture obtained by reducing 2,4-dinitrodiphenylamine condensed from aniline and 2,4-nitrochlorobenzene) and a ketone of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing examples, or perform equivalent substitutions on some of the technical features, or only use the technology of the present invention to carry out a continuous process. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A p-phenylenediamine compound, characterized in that: Having the structural formula shown in the following formula (1): In formula (1), both R1 and R2 are 1,3-dimethylbutyl.

2. A method for preparing the p-phenylenediamine compound according to claim 1, characterized in that: Hydrogenation reaction of 2,4-diaminodiphenylamine and 4-methyl-2-pentanone is carried out in the presence of a catalyst to obtain a p-phenylenediamine compound.

3. The preparation method according to claim 2, characterized in that: The molar ratio of 2,4-diaminodiphenylamine to the ketone is 1:10 - 15.

4. The preparation method according to claim 2, characterized in that: The catalyst is a metal catalyst.

5. The preparation method according to claim 4, characterized in that: The catalyst is palladium-carbon, platinum, rhodium, Raney nickel or copper alloy.

6. The preparation method according to claim 4, characterized in that: The catalyst dosage is 1% - 5% of the mass of 2,4-diaminodiphenylamine.

7. The preparation method according to claim 2, characterized in that: The reaction temperature is 70 - 180 °C.

8. The preparation method according to claim 2, characterized in that: Hydrogen is introduced for the reaction. The pressure of the introduced hydrogen is 2 - 4 Mpa. During the reaction process, when the hydrogen pressure drops to 1 Mpa, hydrogen is refilled to 2 - 4 Mpa. When the pressure remains unchanged at 1 MPa, the reaction is regarded as completed.

9. The preparation method according to any one of claims 2-8, characterized in that: The 2,4-diaminodiphenylamine is obtained by catalytic hydrogenation reaction of 2,4-dinitrodiphenylamine.

10. The preparation method according to claim 9, characterized in that: When preparing 2,4-diaminodiphenylamine, the reaction temperature is 70 - 120 °C.

11. The preparation method according to claim 9, characterized in that: When preparing 2,4-diaminodiphenylamine, the pressure of the introduced hydrogen is 2 - 4 Mpa. During the reaction process, when the hydrogen pressure drops to 1 Mpa, hydrogen is refilled to 2 - 4 Mpa. When the pressure remains unchanged at 1 MPa, the reaction is regarded as completed.

12. The preparation method according to claim 9, characterized in that: When preparing 2,4-diaminodiphenylamine, the catalyst is a metal catalyst.

13. The preparation method according to claim 12, characterized in that: When preparing 2,4-diaminodiphenylamine, the catalyst is palladium-carbon, platinum, rhodium, Raney nickel or copper alloy.

14. The preparation method according to claim 12, characterized in that: When preparing 2,4-diaminodiphenylamine, the catalyst dosage is 3% - 5% of the mass of 2,4-dinitrodiphenylamine.

15. The preparation method according to claim 9, characterized in that: The 2,4-dinitrodiphenylamine is obtained by the reaction of aniline and 2,4-dinitrochlorobenzene in the presence of an acid-binding agent.

16. The preparation method according to claim 15, characterized in that: When preparing 2,4-dinitrodiphenylamine, the reaction temperature is 120 - 160 °C.

17. The preparation method according to claim 15, characterized in that: When preparing 2,4-dinitrodiphenylamine, the molar ratio of aniline to 2,4-dinitrochlorobenzene is (1 - 1.5):

1.

18. The preparation method according to claim 15, characterized in that: When preparing 2,4-dinitrodiphenylamine, the acid-binding agent is an inorganic base.

19. The preparation method according to claim 15, characterized in that: When preparing 2,4-dinitrodiphenylamine, the acid-binding agent is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate.

20. The preparation method according to claim 15, characterized in that: When preparing 2,4-dinitrodiphenylamine, the acid-binding agent dosage is 30 - 40% of the mass of 2,4-dinitrochlorobenzene.

21. Use of the p-phenylenediamine compound according to claim 1 in anti-rubber thermal-oxidative aging and / or anti-rubber fatigue and / or anti-rubber discoloration.

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