P-phenylenediamine compound as well as preparation method and application thereof

Abstract

The invention discloses a p-phenylenediamine compound as well as a preparation method and application thereof, and the compound is obtained by carrying out hydrogenation reaction on 2, 4-diaminodiphenylamine and ketone in the presence of a catalyst. Compared with the current mainstream anti-aging agent 6PPD, the compound provided by the invention has good anti-dynamic / static ozone protection performance, good anti-dynamic fatigue performance and anti-emigration discoloration performance; the tire added with the compound provided by the invention does not generate toxic residues of p-benzoquinone structural substances in the use process, is more green and environment-friendly, is an ideal substitute of the anti-aging agent 6PPD, and has good economic and social benefits and wide market prospects.

Description

Technical Field

[0001] The invention relates to a p-phenylenediamine compound, in particular to a p-phenylenediamine compound capable of replacing an antioxidant 6PPD, and also to a preparation method of the p-phenylenediamine compound and application of the p-phenylenediamine compound as a rubber antioxidant, belonging to the technical field of fine chemicals. Background Art

[0002] The p-phenylenediamine antioxidant 6PPD is the best product currently in use, but in 2023 the tire industry received a report from the University of Washington and the Washington Stormwater Center, which claimed that a 6PPD conversion byproduct called 6PPD-Q is toxic to cod and may cause urban runoff mortality syndrome for the species. The EU and the US have expressed concerns about 6PPD products, which may be banned in the near future. Rubber additive industry companies are seeking alternatives to 6PPD. The mechanism of the antioxidant 6PPD producing p-phenylenediamine structural substances 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 now, and it will also 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. Experimental verification shows that the 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 the compound will not produce toxic p-phenylenediamine structural substance residues during use, is more green and environmentally friendly, and is an ideal substitute for the antioxidant 6PPD.

[0006] In order to achieve the above object, 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 may be the same as R2 or different from each other, 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] For example, the p-phenylenediamine compound of the present invention may be one of the structures shown in Table 1 below:

[0011]

[0012]

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

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

[0015] Furthermore, the structure of the ketone varies depending on the structure of the final 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 ketone is 1:(10-15), for example, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15.

[0016] Furthermore, the catalyst for the reaction of 2,4-diaminodiphenylamine and ketone is a catalyst commonly used in catalytic hydrogenation reactions, such as a metal catalyst, which may be palladium carbon, platinum, rhodium, Raney nickel, copper alloy, and the like.

[0017] Furthermore, the amount of the catalyst is 1%-5% by mass of 2,4-diaminodiphenylamine, for example, 1%, 2%, 3%, 4%, 5%.

[0018] Furthermore, the reaction temperature of 2,4-diaminodiphenylamine and ketone is 70-180°C, for example, 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, ketone and catalyst are mixed, and then hydrogen is introduced for reaction. The pressure of the introduced hydrogen is 2 to 4 MPa. During the reaction, when the hydrogen pressure drops to 1 MPa, hydrogen is added to 2 to 4 MPa. When the pressure is maintained at 1 MPa and no longer changes, the reaction is considered to be completed.

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

[0021] Furthermore, 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, for example, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C. The pressure of the hydrogen introduced is 2-4Mpa. During the reaction, when the hydrogen pressure drops to 1Mpa, hydrogen is refilled to 2-4Mpa. When the pressure is maintained at 1MPa and no longer changes, the reaction is considered to be complete. The catalyst used is a catalyst commonly used in catalytic hydrogenation reactions, such as a metal catalyst, which can be listed as palladium carbon, platinum, rhodium, Raney nickel, copper alloy, etc. The amount of the catalyst used is 3%-5% of the mass of the raw material 2,4-dinitrodiphenylamine, for example, 3%, 4%, 5%.

[0022] Furthermore, the 2,4-dinitrodiphenylamine can be purchased directly or prepared by itself, 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, for example, 120°C, 130°C, 140°C, 150°C, 160°C. The molar ratio of aniline to 2,4-dinitrochlorobenzene is (1-1.5):1, for example, 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, for example, at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate, preferably potassium carbonate. The amount of the acid binding agent is 30-40% of the mass of 2,4-dinitrochlorobenzene, for example, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%. The reaction is carried out in the presence of an organic solvent, which may be toluene or the like. The water formed is continuously separated during the reaction.

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

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

[0026]

[0027] b. Catalytic hydrogenation of 2,4-dinitrodiphenylamine to obtain 2,4-diaminodiphenylamine, the reaction formula is as follows:

[0028]

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

[0030]

[0031] The p-phenylenediamine compounds of the present invention can not only play a good ozone protection effect, but also do not produce toxic and harmful p-phenylenediamine substances, and are good substitutes for 6PPD. Therefore, the application of the p-phenylenediamine compounds as rubber antioxidants 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 the antioxidant 6PPD, the compound of the present invention has an additional amino alkyl group on the benzene ring at one end of the alkane, and the ozone protection effect is better;

[0034] 2. Compared with the antioxidant 6PPD, the compound of the present invention has an additional aminoalkyl group on the benzene ring at one end of the alkane, so no toxic or harmful benzodiquinone residues will be produced in the rubber, and it is green, non-toxic and more environmentally friendly.

[0035] 3. The present invention can better enhance the anti-aging effect of rubber by optimizing and screening the aminoalkyl substituents.

[0036] 4. The compound of the present invention is a good substitute for 6PPD and has broad market prospects. DETAILED DESCRIPTION

[0037] The present invention is described in detail below through specific examples, but the use and purpose of these exemplary implementation modes are only used to illustrate the present invention, and do not constitute any form of limitation on the actual protection scope of the present invention, nor limit the protection scope of the present invention to them.

[0038] Example 1

[0039] Step 1: Synthesis of the intermediate 2,4-dinitrodiphenylamine

[0040] Weigh 32.6 g (0.35 mol) of aniline, 60.8 g (0.3 mol) of 2,4-dinitrochlorobenzene, 380 g of toluene, and 21.3 g of acid-binding agent potassium carbonate, and put them into a 1000 ml reaction device with a water separator, and keep the temperature at 120-140°C for reflux reaction. When no water droplets are generated in the fractionation column, the reaction is considered to be over. Then, decompress the toluene and excess aniline to evaporate, pour the remaining material into cold water and stir to precipitate solids, filter and wash with 300 ml of hot water for 3-4 times, and vacuum dry the filter cake at 70-80°C to obtain 76.2 g of 2,4-dinitrodiphenylamine, with a yield of 98% based on 2,4-dinitrochlorobenzene.

[0041] Step 2: Synthesis of the 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 2L autoclave, weigh 3.2 g of palladium carbon and add it to the autoclave, first replace the air in the autoclave with nitrogen for 3 times, then replace it with nitrogen for another 3 times, heat it to 80°C, introduce hydrogen to 3 MPa, and when the pressure in the autoclave drops to 1 MPa, refill it with hydrogen to 3 MPa. When the pressure in the autoclave is maintained at 1 MPa and no longer changes, the reaction is considered complete, then cool and release the pressure to release the reaction liquid, filter out the catalyst (can be recycled 2-3 times), remove the solvent methanol by rotary evaporation of the filtrate, pour it out and cool it to obtain 49.1 g of 2,4-diaminodiphenylamine, 98.6% based on 2,4-dinitrodiphenylamine.

[0043] The third step is the synthesis of new p-phenylenediamine antioxidant

[0044] 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) were weighed and added to a 1L autoclave. The air in the autoclave was replaced 3 times with nitrogen first, and then replaced 3 times with nitrogen. When the temperature was raised to 80°C, hydrogen was introduced to 3 MPa. When the pressure in the autoclave was reduced to 1 MPa, hydrogen was added to 3 MPa. When the pressure in the autoclave was maintained at 1 MPa and did not change, the reaction was considered to be complete. Then the temperature was lowered and the pressure was released to release the reaction liquid. The catalyst was filtered out (it can be recycled 2-3 times). The filtrate was rotary evaporated to remove the excess 4-methyl-2-pentanone and the by-product 4-methyl-2-pentanol, and 52.5 g of the novel antioxidant product of the present invention was obtained, 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 first and second steps are the same as in Example 1, or purchased from the market.

[0048] The third step, the synthesis method of the new 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) into a 1L autoclave, replace the air in the autoclave with nitrogen 3 times, then replace it with nitrogen 3 times, heat to 90°C, introduce hydrogen to 4 MPa, and when the pressure in the autoclave drops to 1 MPa, add hydrogen to 4 MPa. When the pressure in the autoclave is maintained at 1 MPa and does not change, the reaction is considered complete, then cool and release the pressure to release the reaction liquid, filter and remove the catalyst (can be recycled 2-3 times), and remove the excess 5-methyl-2-hexanone and the by-product 5-methyl-2-hexanol by rotary evaporation of the filtrate to obtain 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 first and second steps are the same as in Example 1, or purchased from the market.

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

[0054] Weigh 29.9 grams (0.15 moles) of 2,4-diaminodiphenylamine, 1.4 grams of platinum and 130.7 grams of acetone (2.25 moles) and add them to a 1L autoclave. First, replace the air in the autoclave with nitrogen for 3 times, and then replace it with nitrogen for another 3 times. When the temperature is raised to 80°C, introduce hydrogen to 3.5MPa. When the pressure in the autoclave is reduced to 1MPa, add hydrogen to 3.5MPa. When the pressure in the autoclave is maintained at 1MPa and does not change, the reaction is considered to be complete. Then, cool and release the pressure to release the reaction liquid, filter and filter out the catalyst (which can be recycled 2-3 times), and remove the excess acetone and by-product isopropanol by rotary evaporation of the filtrate to obtain 41.9 grams 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 first and second steps are the same as in Example 1, or purchased from the market.

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

[0059] Weigh 29.9 grams (0.15 moles) of 2,4-diaminodiphenylamine, 1.4 grams of copper-zinc alloy and 186.4 grams of cyclohexanone (1.9 moles) into a 1L autoclave, replace the air in the autoclave with nitrogen three times, and then replace it with nitrogen three more times, and introduce hydrogen to 4MPa when the temperature is raised to 180°C. When the pressure in the autoclave is reduced to 1MPa, hydrogen is added to 4MPa again. When the pressure in the autoclave is maintained at 1MPa and does not change, the reaction is considered to be complete, and then the temperature is lowered and the pressure is released to release the reaction liquid, and the catalyst is filtered out (it can be recycled 2-3 times). The filtrate is rotary evaporated to remove excess cyclohexanone and by-product cyclohexanol, and 50.7 grams of the new antioxidant product of the present invention is obtained, and the yield is 96.8% based on 2,4-diaminodiphenylamine. The structural formula is as follows:

[0060]

[0061] In order to verify the application effect of the present invention, the new antioxidant synthesized in the above Examples 1-4 was compared with the antioxidant 6PPD, as follows:

[0062] 1. Experiment

[0063] 1.1 Main experimental raw materials

[0064] Natural rubber NR, brand SVR20, is a product of Vietnam; butadiene rubber BR, brand 9000, is a product of China Yueyang Petrochemical General Plant Co., Ltd.; carbon black N330, is a product of Tianjin Yiborui Chemical Co., Ltd.; accelerator NS, insoluble sulfur HD0T20 and rubber protective wax H7075, are 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 butadiene rubber BR, 50 parts of carbon black N330, 8 parts of naphthenic oil, 1.5 parts of rubber protective 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 test antioxidant (variant, respectively using the antioxidant prepared by the embodiment of the present invention and antioxidant 6PPD), 1 part of antioxidant RD. At the same time, the rubber material without test antioxidant was used as a blank control.

[0067] 1.3 Main experimental equipment

[0068] XK-160 open mixing mill, a product of Dalian Chengxin Rubber & Plastic Machinery Co., Ltd.; HS-100T-RTMO flat plate vulcanizer, a product of Jiaxin Electronic Equipment Technology (Shenzhen) Co., Ltd.; X(S)M-1.5 laboratory internal mixer, a product of Qingdao Kegao Rubber & 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 mixing stage is 40r·min-1. The raw rubber is first plasticized for 1 min, then stearic acid, zinc oxide, rubber protective wax, antioxidant, cyclopentane oil and carbon black are added, the pressing roller is pressed for 35s and raised for 10s, the pressing roller is pressed for 45s, the pressing roller is raised for 10s, and the rubber is discharged (145℃).

[0071] The second-stage mixing rotor speed is 48r·min-1, and the first-stage mixing rubber, insoluble sulfur and accelerator are mixed. The pressing roller is pressed for 80s, the pressing roller is lifted for 10s, the pressing roller is pressed for 55s, and the rubber is discharged (110℃).

[0072] 1.5 Ozone resistance test

[0073] The ozone resistance is tested in accordance with GBT7762-2003 static tensile test for ozone cracking resistance of vulcanized rubber or thermoplastic rubber and GB / T13642-2015 dynamic tensile test for ozone cracking resistance of vulcanized rubber or thermoplastic rubber.

[0074] The sample grade is evaluated according to the following Tables 1 and 2:

[0075]

[0076]

[0077] The crack grade is evaluated according to the grades listed in Table 1 and Table 2, and the combined results are used as the results. The evaluation of the crack grade is mainly based on the crack width, supplemented by the crack density, and the width grade and density grade are combined to indicate the test results. Note: If the crack width is grade 2 and the crack density is grade c, the crack grade of the sample is grade 2c.

[0078] 1.6 Mechanical properties test of vulcanized rubber

[0079] The mechanical properties of vulcanized rubber are tested in accordance with GB / T3512-2014 hot air accelerated aging and heat resistance test for vulcanized rubber or thermoplastic rubber.

[0080] 1.7 Anti-discoloration performance of vulcanized rubber

[0081] The anti-discoloration performance of vulcanized rubber is tested in accordance with GB / T 528-2009.

[0082] 2. Test results

[0083] 2.1. Dynamic / static ozone aging test data of vulcanized rubber

[0084] Table 3 Test data of dynamic / static ozone resistance of rubber

[0085]

[0086]

[0087] 2.2 Mechanical properties of vulcanized rubber

[0088] Table 4 Test data of thermal oxidation aging and fatigue resistance of rubber

[0089]

[0090]

[0091] 2.3. Anti-discoloration performance of vulcanized rubber

[0092] Table 5 Vulcanized rubber discoloration detection

[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 over the mainstream antioxidant 6PPD in the market:

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

[0096] 2. It has better resistance to thermal oxidation aging and dynamic fatigue, among which the new antioxidant in Example 1 has the best performance;

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

[0098] In addition, the novel antioxidant of the present invention does not produce any toxic benzodiquinone residues and is green and environmentally friendly, and is therefore a good substitute for 6PPD.

[0099] Finally, it should be noted that the above is only a preferred part of the novel antioxidant synthesized from 2,4-diaminodiphenylamine (or a mixture obtained by reducing 2,4-dinitrodiphenylamine obtained by condensing aniline and 2,4-nitrochlorobenzene) and ketone of the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical schemes recorded in the aforementioned embodiments, or to perform equivalent replacement of some of the technical features therein, or to simply use the technology of the present invention to perform continuous engineering. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A p-phenylenediamine compound, characterized in that: It has the structural formula shown in the following formula (1): In formula (1), R1 and R2 are each independently selected from hydrogen, cyclohexyl, cyclooctyl, 2-cyclohexylethyl, 2-phenylethyl, benzyl, isopropyl, 1,3-dimethylbutyl, 1,4-dimethylpentyl; preferably, R1 and R2 are both 1,3-dimethylbutyl.

2. A method for preparing the p-phenylenediamine compound according to claim 1, characterized in that: The 2,4-diaminodiphenylamine and ketone are subjected to hydrogenation reaction in the presence of a catalyst to obtain p-phenylenediamine compounds.

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

4. The preparation method according to claim 2, characterized in that: The catalyst is a metal catalyst, preferably palladium carbon, platinum, rhodium, Raney nickel, or copper alloy; preferably, the amount of the catalyst is 1%-5% of the mass of 2,4-diaminodiphenylamine.

5. The preparation method according to claim 2, characterized in that: The reaction temperature is 70-180°C; preferably, hydrogen is introduced for reaction, and the pressure of the introduced hydrogen is 2-4Mpa. During the reaction, when the hydrogen pressure drops to 1Mpa, hydrogen is added to 2-4Mpa. When the pressure is maintained at 1MPa and no longer changes, the reaction is considered to be complete.

6. The preparation method according to any one of claims 2 to 5, characterized in that: The 2,4-diaminodiphenylamine is obtained by catalytic hydrogenation of 2,4-dinitrodiphenylamine.

7. The preparation method according to claim 6, characterized in that: When preparing 2,4-diaminodiphenylamine, the reaction temperature is 70-120°C; preferably, the pressure of the hydrogen introduced is 2-4Mpa, and when the hydrogen pressure drops to 1Mpa during the reaction, hydrogen is refilled to 2-4Mpa, and the reaction is considered to be complete when the pressure is maintained at 1MPa and does not change; preferably, the catalyst is a metal catalyst; preferably, the catalyst is palladium carbon, platinum, rhodium, Raney nickel, or copper alloy; preferably, the amount of the catalyst is 3%-5% of the mass of 2,4-dinitrodiphenylamine.

8. The preparation method according to claim 6, characterized in that: The 2,4-dinitrodiphenylamine is obtained by reacting aniline and 2,4-dinitrochlorobenzene in the presence of an acid-binding agent.

9. The preparation method according to claim 8, characterized in that: When preparing 2,4-dinitrodiphenylamine, the reaction temperature is 120-160°C; preferably, the molar ratio of aniline to 2,4-dinitrochlorobenzene is (1- 1.5):1; Preferably, the acid binding agent is an inorganic base; Preferably, the inorganic base is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate; Preferably, the amount of the acid binding agent is 30-40% of the mass of 2,4-dinitrochlorobenzene.

10. Use of the p-phenylenediamine compound according to claim 1 as a rubber antioxidant.

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