An environmentally friendly p-phenylenediamine antioxidant and its preparation method and application

Abstract

The present invention discloses an environmentally friendly p-phenylenediamine antioxidant, its preparation method, and application. The environmentally friendly p-phenylenediamine antioxidant has a structure represented by formula (I). The p-phenylenediamine antioxidant with the structure represented by formula (I) exhibits excellent anti-aging properties and does not produce highly toxic quinone products, providing protection against ozone, heat, and oxygen aging. Rubber vulcanizates using the environmentally friendly p-phenylenediamine antioxidant of the present invention exhibit excellent physical properties and aging resistance. Toxicity testing of rubber residues revealed no highly toxic quinone products, demonstrating environmental friendliness and non-toxicity. #imgabs0#

Description

Technical Field

[0001] The present invention relates to a p-phenylenediamine antioxidant, in particular to an environmentally friendly p-phenylenediamine antioxidant and a preparation method and application thereof. Background Art

[0002] Rubber ages due to structural changes caused by exposure to oxygen, ozone, acids, alkalis, water, and other substances in the air, as well as heat, ultraviolet rays, and mechanical forces. The most effective way to prevent rubber from fatigue aging is to add antioxidants, which work by increasing the stability of structural changes during the fatigue process.

[0003] Currently, the most widely used antioxidant is p-phenylenediamine. For example, rubber antioxidant 4020, chemically known as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, belongs to the same p-phenylenediamine family as antioxidants 4010NA and 4010. These highly effective rubber antioxidants are used in transportation tires, cables, and rubber products used in waterproofing projects. They offer excellent protection against ozone, flexural aging, oxygen, heat, and other common aging factors. They also offer excellent protection against harmful metals such as copper and manganese.

[0004] 3.1 billion new tires are produced worldwide each year, and when combined with the existing tire stock, the global tire population is enormous. The massive debris generated by the friction between tires and the ground poses a threat to the environment and human health, and its impact can even be compared to that of microplastics in the ocean. Even more frightening is that the antioxidants in these tire debris will become more toxic through "mutation" in the natural environment. According to a 2020 report in Science magazine, the products of the reaction of paraphenylenediamine antioxidants with ozone in the natural environment may be deadly toxins. The team of Professor Edward P. Kolodziej of the University of Washington (Science, 2020-12-3.DOI:10.1126 / science.abd6951) studied the LC50 of 6PPD-quinone, a highly toxic quinone transformation product of the antioxidant 6PPD. 50 The median lethal concentration of p-phenylenediamine antioxidants is only 0.79±0.16μg / L, while the median lethal concentration of tire filtrate is 0.82±0.27μg / L. Quinones produced by ozone aging of p-phenylenediamine antioxidants are the most toxic substances in tires. Therefore, there is an urgent need to develop environmentally friendly antioxidants that can prevent ozone aging and generate quinones, thereby reducing the harm of tire rubber residues to the environment and human health. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides an environmentally friendly p-phenylenediamine antioxidant and its preparation method and application. The p-phenylenediamine antioxidant provided by the present invention does not produce highly toxic quinone products, has the function of protecting against ozone, heat and oxygen aging, and is environmentally friendly and non-toxic.

[0006] The technical solution adopted in the present invention is:

[0007] An environmentally friendly p-phenylenediamine antioxidant having the structure shown in formula (I):

[0008]

[0009] In the formula (I), R 1 、R 1’ Selected from C1-C 18 chain hydrocarbon group or alicyclic hydrocarbon group or H, R 2 、R 3 Selected from C1-C 18 Chain hydrocarbon group or R 2 With R 3 Forming a fat ring, R 4 、R 5 Selected from C1-C 18 Chain hydrocarbon group or R 4 With R 5 Forming an aliphatic ring; x = 0 or 1, y = 0 or 1, z = 0 or 1, w = 0 or 1, and at least one of x and w is 1, and at least one of y and z is 1.

[0010] Preferably, the structure of formula (I) is

[0011]

[0012] Among them, R 1 、R 1’ Selected from C1-C 18 chain hydrocarbon group or alicyclic hydrocarbon group or H, R 2 、R 3 Selected from C1-C 18 Chain hydrocarbon group or R 2 With R 3 Formation of a fat ring.

[0013] Preferably, the structure of formula (I) is

[0014]

[0015] Among them, R 1 、R 1’ Selected from C1-C 18 Chain hydrocarbon or alicyclic hydrocarbon or H, R 3 、R 5 Selected from C1-C18 chain hydrocarbon group.

[0016] Preferably, the structure of formula (I) is

[0017]

[0018] Among them, R 1 、R 1’ Selected from C1-C 18 chain hydrocarbon group or alicyclic hydrocarbon group or H, R 2 、R 3 Selected from C1-C 18 Chain hydrocarbon group or R 2 With R 3 Forming a fat ring, R 4 、R 5 Selected from C1-C 18 chain hydrocarbon group.

[0019] Preferably, the structure of formula (I) is:

[0020]

[0021] Among them, R 1 、R 1’ Selected from C1-C 18 chain hydrocarbon group or alicyclic hydrocarbon group or H, R 2 、R 3 Selected from C1-C 18 Chain hydrocarbon group or R 2 With R 3 Forming a fat ring, R 4 、R 5 Selected from C1-C 18 Chain hydrocarbon group or R 4 With R 5 Formation of a fat ring.

[0022] Existing p-phenylenediamine antioxidants tend to form p-benzoquinone on the p-phenylenediamine benzene ring when reacting with ozone. This is because the four remaining positions on the p-phenylenediamine benzene ring after the p-amino group is substituted are in a relatively electron-rich, activated state, making them easily oxidized by atmospheric ozone or oxygen to p-benzoquinone, a highly toxic substance. The present invention provides an environmentally friendly p-phenylenediamine antioxidant that, by capping the p-phenylenediamine benzene ring with substitution, eliminates simultaneous exposure of the p-position, thereby preventing the p-phenylenediamine antioxidant from oxidizing to form the highly toxic p-benzoquinone. Therefore, rubber tires using the present environmentally friendly p-phenylenediamine antioxidant are environmentally and human-safe, producing rubber residue during use or after aging.

[0023] The present invention also provides a method for preparing an environmentally friendly p-phenylenediamine antioxidant as shown in formula (I), comprising the steps of: subjecting aniline to a CN coupling reaction with p-bromonitrobenzene having corresponding substituents; subjecting the obtained coupling product to a reduction reaction in a hydrogen atmosphere under catalytic conditions to obtain a reaction intermediate; and subjecting the reaction intermediate to a reductive amination reaction with an aldehyde or ketone under catalytic conditions to obtain the p-phenylenediamine antioxidant.

[0024] Preferably, the CN coupling reaction is carried out in an inert atmosphere, and the molar ratio of the aniline to the p-bromonitrobenzene having the corresponding substituent is 1:1.0-1.2; the catalyst for the CN coupling reaction is a palladium catalyst, and the palladium catalyst is selected from Pd2(dba)3(tris(dibenzylideneacetone)dipalladium), Pd(OAc)2(palladium acetate), Pd(PPh3)4(tetrakis(triphenylphosphine)palladium) or Pd(acac)2(bis(acetylacetonate)palladium(II)); the ligand of the palladium catalyst is selected from the phosphine ligand XPhos(2-dicyclohexyl Phosphine-2',4',6'-triisopropylbiphenyl), phosphine ligand SPhos (2-dicyclohexylphosphine-2',6'-dimethoxy-1,1'-biphenyl) or phosphine ligand BINAP (2,2'-bisdiphenylphosphino-1,1'-binaphthyl); the base added in the CN coupling reaction is selected from K2CO3, Cs2CO3, t-BuOK or t-BuONa; the reaction solvent of the CN coupling reaction is selected from isopropanol, methanol, tert-butanol or 1,4-dioxane; the reaction temperature of the CN coupling reaction is 70-120°C;

[0025] Preferably, the catalyst for the reduction reaction is a platinum-carbon catalyst, wherein the amount of platinum-carbon is 5-20% of the mass of the p-bromonitrobenzene having the corresponding substituent; the hydrogen pressure of the reduction reaction is 0.05-1 MPa, the reaction temperature is 50-100 o C;

[0026] The molar ratio of the reaction intermediate to the aldehyde or ketone is 1:1.5-2, and the reaction temperature of the reductive amination reaction is 130-170 o C. The reaction pressure is 2-5 MPa and the catalyst is a platinum-carbon catalyst.

[0027] The catalyst for the reduction reaction and the reductive amination reaction can be not only a platinum-carbon catalyst, but also a metal catalyst selected from Group VIII of the periodic table, such as Ni, Pd, Ru, etc.; or a copper-based catalyst.

[0028] Preferably, the molar ratio of the aniline to the p-bromonitrobenzene having the corresponding substituent is 1:1.1, the palladium catalyst is Pd2(dba)3, the ligand of the palladium catalyst is XPhos, the base added in the CN coupling reaction is K2CO3, the reaction solvent of the CN coupling reaction is isopropanol, and the reaction temperature of the CN coupling reaction is 110°C.

[0029] The amount of the platinum-carbon catalyst used in the reduction reaction is 10% of the mass of the p-bromonitrobenzene having the corresponding substituents. The hydrogen pressure of the reduction reaction is 0.2 MPa and the reaction temperature is 80°C.

[0030] The general reaction formula is:

[0031]

[0032] The present invention also provides an application of an environmentally friendly p-phenylenediamine antioxidant as shown in formula (I) in rubber mixing or vulcanization. The antioxidant is applied to natural rubber or synthetic rubber, mixed using a conventional mixing method, and vulcanized rubber is obtained after vulcanization.

[0033] Compared with existing p-phenylenediamine antioxidants, the environmentally friendly p-phenylenediamine antioxidant provided by the present invention has good anti-aging performance and does not produce highly toxic quinone products, and has the function of protecting against ozone, heat and oxygen aging; the rubber vulcanizate using the environmentally friendly p-phenylenediamine antioxidant of the present invention has excellent physical properties and aging resistance, and toxicity testing of rubber residues shows no highly toxic quinone products are detected, indicating that the rubber is environmentally friendly and non-toxic. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with specific embodiments.

[0035] Comparative Example 1

[0036] Under an inert gas nitrogen atmosphere, 15.2 g (0.066 mol, 1.1 eq) of 2,5-dimethyl-4-nitrobromobenzene, 0.552 g (0.0006 mol, 1%) of Pd2(dba)3, 1.416 g (0.003 mol, 5%) of XPhos, 16.58 g (0.12 mol, 2 eq) of K2CO3 and 5.58 g (0.06 mol) of aniline were added to a 500 mL three-necked flask and dispersed in 250 mL of isopropanol. The mixture was then refluxed at 110 ° C for 24 h. The reaction system was filtered, the liquid was extracted, the organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain a crude intermediate. In a hydrogen atmosphere, the obtained crude intermediate was added to 1 L of ethanol, 1.52 g of platinum-carbon catalyst (containing 0.076 g of platinum) was added, the hydrogen pressure was 0.2 MPa, and the reaction was carried out at 80° C. for 24 h. After the reaction was completed, it was cooled to room temperature, filtered, and the filter cake was washed with hot ethanol. The solvent was removed by rotary evaporation, and then column chromatography was performed using 400 mesh silica gel powder. The eluent system was petroleum ether and ethyl acetate, and the gradient elution polarity selection range was petroleum ether: ethyl acetate (volume ratio) 10:1 to 3:1 to obtain 9.32 g of the reaction intermediate 2,5-dimethyl-4-amino-p-phenylenediamine.

[0037] 9.29 g (0.038 mol) of the reaction intermediate 2,5-dimethyl-4-amino-p-phenylenediamine, 7.53 g (0.075 mol) of methyl isobutyl ketone, and 0.96 g of a platinum-carbon catalyst (containing 0.048 g of platinum) were reacted under a hydrogen atmosphere. The reaction system was heated from room temperature to 150° C. within 1 hour, and then the hydrogen was pressurized to about 2.94 MPa, while maintaining the temperature and pressure stable. After reacting for 2 hours, the hydrogen was discharged from the autoclave and the pressure was restored to normal. At the same time, the reaction system was cooled to room temperature, and the catalyst and activated carbon in the reaction solution were filtered out. The crude product was separated by high performance liquid chromatography to obtain 12 g of a new compound, which was characterized by nuclear magnetic resonance spectroscopy as compound (antioxidant D-1). The data are as follows: 1 H NMR (600MHz, CDCl3) δ7.23(t,J=7.9Hz,2H),6.88(d,J=7.9Hz,2H),6.82(t ,J=7.2Hz,1H),6.75(s,1H),6.28(s,1H),5.40(s,1H),3.60-3.50(m,1H),3 .32(s,1H),2.16(s,6H),1.88-1.78(m,1H),1.57-1.48(m,1H),1.36-1.26( m,1H),1.22(d,J=6.2Hz,3H),1.01(d,J=6.6Hz,3H),0.99(d,J=6.6Hz,3H). 13C NMR (150MHz, CDCl3) δ146.48,144.16,132.17,129.28,122.63,119.70,118.67,114.78,47.15,47.06,25.21,23.12,22.69,21.21,18.53.

[0038] The structural formula of the compound (antioxidant D-1) is as follows:

[0039]

[0040] The reaction formula of the above reaction is as follows:

[0041]

[0042] Example 1

[0043] Under an inert gas nitrogen atmosphere, 15.2 g (0.066 mol, 1.1 eq) of 3,5-dimethyl-4-nitrobromobenzene, 0.552 g (0.0006 mol, 1%) of Pd2(dba)3, 1.416 g (0.003 mol, 5%) of XPhos, 16.58 g (0.12 mol, 2 eq) of K2CO3 and 5.58 g (0.06 mol) of aniline were added to a 500 mL three-necked flask and dispersed in 250 mL of isopropanol. The mixture was then refluxed at 110 ° C for 24 h. The reaction system was filtered, the liquid was extracted, the organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain a crude intermediate. In a hydrogen atmosphere, the obtained crude intermediate was added to 1 L of ethanol, 1.52 g of platinum-carbon catalyst (containing 0.076 g of platinum) was added, the hydrogen pressure was 0.2 MPa, and the reaction was carried out at 80° C. for 24 h. After the reaction was completed, it was cooled to room temperature, filtered, and the filter cake was washed with hot ethanol. The solvent was removed by rotary evaporation, and then column chromatography was performed using 400 mesh silica gel powder. The eluent system was petroleum ether and ethyl acetate, and the gradient elution polarity selection range was petroleum ether: ethyl acetate (volume ratio) 10:1 to 3:1 to obtain 9.45 g of the reaction intermediate 3,5-dimethyl-4-amino-p-phenylenediamine.

[0044] 9.29 g (0.038 mol) of the reaction intermediate 3,5-dimethyl-4-amino-p-phenylenediamine, 7.53 g (0.075 mol) of methyl isobutyl ketone, and 0.96 g of a platinum-carbon catalyst (containing 0.048 g of platinum) were reacted under a hydrogen atmosphere. The reaction system was heated from room temperature to 150° C. within 1 hour, and then the hydrogen was pressurized to about 2.94 MPa, while maintaining the temperature and pressure stable. After reacting for 2 hours, the hydrogen was discharged from the autoclave and the pressure was restored to normal. At the same time, the reaction system was cooled to room temperature, and the catalyst and activated carbon in the reaction solution were filtered out. The crude product was separated by high performance liquid chromatography to obtain 12.5 g of a new compound, which was characterized as the target compound (antioxidant O-1) by nuclear magnetic resonance spectroscopy. The data are as follows: 1 H NMR (600MHz, CDCl3) δ7.23(t,J=7.9Hz,2H),6.88(d,J=7.9Hz,2H),6.82(t,J=7.2Hz,1H),6.75(s,2H),5.40(s,1H),3.61-3.49(m,1H),3.32(s, 1H),2.16(s,6H),1.87-1.78(m,1H),1.57-1.50(m,1H),1.36-1.28(m,1 H), 1.22 (d, J = 6.2Hz, 3H), 1.01 (d, J = 6.6Hz, 3H), 0.99 (d, J = 6.6Hz, 3H). 13 C NMR (150MHz, CDCl3) δ146.49,144.18,132.17,129.29,122.51,119.71,118.69,114.82,47.15,47.06,25.21,23.12,22.69,21.21,18.53.

[0045] The structural formula of the target compound (antioxidant O-1) is as follows:

[0046]

[0047] The reaction formula of the above reaction is as follows:

[0048]

[0049] Example 2

[0050] Under an inert gas nitrogen atmosphere, 15.2 g (0.066 mol, 1.1 eq) of 2,3-dimethyl-4-nitrobromobenzene, 0.552 g (0.0006 mol, 1%) of Pd2(dba)3, 1.416 g (0.003 mol, 5%) of XPhos, 16.58 g (0.12 mol, 2 eq) of K2CO3 and 5.58 g (0.06 mol) of aniline were added to a 500 mL three-necked flask and dispersed in 250 mL of isopropanol. The mixture was then refluxed at 110 ° C for 24 h. The reaction system was filtered, the liquid was extracted, and the organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain a crude intermediate. In a hydrogen atmosphere, the obtained crude intermediate was added to 1 L of ethanol, 1.52 g of platinum-carbon catalyst (containing 0.076 g of platinum) was added, the hydrogen pressure was 0.2 MPa, and the reaction was carried out at 80° C. for 24 h. After the reaction was completed, it was cooled to room temperature, filtered, and the filter cake was washed with hot ethanol. After removing the solvent with a rotary evaporator, column chromatography was performed using 400 mesh silica gel powder. The eluent system was petroleum ether and ethyl acetate, and the gradient elution polarity selection range was petroleum ether: ethyl acetate (volume ratio) 10:1 to 3:1 to obtain 9.4 g of the reaction intermediate 2,3-dimethyl-4-amino-p-phenylenediamine.

[0051] 9.29 g (0.038 mol) of the reaction intermediate 2,3-dimethyl-4-amino-p-phenylenediamine, 7.53 g (0.075 mol) of methyl isobutyl ketone, and 0.96 g of a platinum-on-carbon catalyst (containing 0.048 g of platinum) were reacted under a hydrogen atmosphere. The reaction system was heated from room temperature to 150°C over 1 hour, and then the hydrogen pressure was increased to approximately 2.94 MPa, maintaining the temperature and pressure stable. After 2 hours of reaction, the hydrogen was discharged from the autoclave, and the pressure was restored to normal. The reaction system was cooled to room temperature, and the catalyst and activated carbon in the reaction solution were filtered out. The crude product was separated by high-performance liquid chromatography to obtain 12 g of a new compound, which was characterized by nuclear magnetic resonance spectroscopy as the target compound (antioxidant O-2). The data are as follows: 1 H NMR (600MHz, CDCl3) δ7.22(t,J=7.9Hz,2H),6.87(d,J=7.9Hz,2H),6.82(t,J=7 .2Hz,1H),6.70(d,J=8.2Hz,1H),6.28(d,J=8.2Hz,1H),5.40(s,1H),3.60-3.50 (m,1H),3.32(s,1H),2.16(s,6H),1.86-1.77(m,1H),1.56-1.50(m,1H),1.35-1 .28(m,1H),1.22(d,J=6.2Hz,3H),1.01(d,J=6.6Hz,3H),0.99(d,J=6.6Hz,3H). 13C NMR (150MHz, CDCl3) δ146.49,144.17,132.17,129.41,129.29,119.92,118.69,1 16.30,114.82,106.83,47.15,47.06,25.21,23.12,22.69,21.21,18.52,18.50.

[0052] The target compound (antioxidant O-2) has the following structural formula:

[0053]

[0054] The reaction formula of the above reaction is as follows:

[0055]

[0056] Example 3

[0057] Under an inert gas nitrogen atmosphere, 16.11 g (0.066 mol, 1.1 eq) of 2,3,5-trimethyl-4-nitrobromobenzene, 0.552 g (0.0006 mol, 1%) of Pd2(dba)3, 1.416 g (0.003 mol, 5%) of XPhos, 16.58 g (0.12 mol, 2 eq) of K2CO3 and 5.58 g (0.06 mol) of aniline were added to a 500 mL three-necked flask and dispersed in 250 mL of isopropanol. The mixture was then refluxed at 110 ° C for 24 h. The reaction system was filtered, the extracts were separated, the organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain a crude intermediate. The obtained crude intermediate was added to 1 L of ethanol, and 1.52 g of platinum-carbon catalyst (containing 0.076 g of platinum) was added. The hydrogen pressure was 0.2 MPa, and the reaction was carried out at 80° C. for 24 h. After the reaction was completed, it was cooled to room temperature, filtered, and the filter cake was washed with hot ethanol. After removing the solvent with a rotary evaporator, column chromatography was performed using 400 mesh silica gel powder. The eluent system was petroleum ether and ethyl acetate, and the gradient elution polarity selection range was petroleum ether: ethyl acetate (volume ratio) 10:1 to 3:1 to obtain 6.8 g of 2,3,5-trimethyl-4-amino-p-phenylenediamine.

[0058] 6.6 g (0.026 mol) of 2,3,5-trimethyl-4-amino-p-phenylenediamine, 5.21 g (0.050 mol) of methyl isobutyl ketone, and 0.66 g of platinum-carbon catalyst (including 0.033 g of platinum) were reacted under a hydrogen atmosphere. The reaction system was heated from room temperature to 150 °C within 1 h. oC, then hydrogen was pressurized to approximately 2.94 MPa, maintaining the temperature and pressure stable. After 2 hours of reaction, the hydrogen was discharged from the autoclave, the pressure was restored to normal, and the reaction system was cooled to room temperature. The catalyst and activated carbon in the reaction solution were filtered out, and the crude product was separated by high-performance liquid chromatography to obtain 8.5 g of a new compound, which was characterized by nuclear magnetic resonance spectroscopy as the target compound (antioxidant O-3). The data are as follows: 1 H NMR (600MHz, CDCl3) δ7.21(t,J=7.9Hz,2H),6.86(d,J=7.9Hz,2H),6.82(t,J=7.2Hz,1H),6.63(s,1H),5.40(s,1H),3.60-3.50(m,1H),3.32(s, 1H),2.16(s,9H),1.85-1.77(m,1H),1.55-1.48(m,1H),1.34-1.25(m,1 H), 1.22 (d, J = 6.2Hz, 3H), 1.01 (d, J = 6.6Hz, 3H), 0.99 (d, J = 6.6Hz, 3H). 13 C NMR (150MHz, CDCl3) δ146.48,144.16,132.16,129.27,126.41,119.62,119.53,118. 68,116.24,114.81,47.15,47.06,25.21,23.12,22.69,21.21,18.52,18.49,18.48.

[0059] The target compound (antioxidant O-3) has the following structural formula:

[0060]

[0061] The reaction formula of the above reaction is as follows:

[0062]

[0063] Example 4

[0064] Under an inert gas nitrogen atmosphere, 17.1 g (0.066 mol, 1.1 eq) of 2,3,5,6-tetramethyl-4-nitrobromobenzene, 0.552 g (0.0006 mol, 1%) of Pd2(dba)3, 1.416 g (0.003 mol, 5%) of XPhos, 16.58 g (0.12 mol, 2 eq) of K2CO3 and 5.58 g (0.06 mol) of aniline were added to a 500 mL three-necked flask and dispersed in 250 mL of isopropanol. The mixture was then refluxed at 110 ° C for 24 h. The reaction system was filtered, the extracts were separated, the organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the crude intermediate. The obtained crude intermediate was added to 1 L of ethanol, and 1.52 g of platinum-carbon catalyst (containing 0.076 g of platinum) was added. The hydrogen pressure was 0.2 MPa, and the reaction was carried out at 80 ° C for 24 hours. After the reaction was completed, it was cooled to room temperature, filtered, and the filter cake was washed with hot ethanol. After removing the solvent with a rotary evaporator, it was separated by column chromatography using 400 mesh silica gel powder. The eluent system was petroleum ether and ethyl acetate. The gradient elution polarity selection range was petroleum ether: ethyl acetate (volume ratio) 10:1 to 3:1 to obtain 8.65 g of 2,3,5,6-tetramethyl-4-amino-p-phenylenediamine.

[0065] 7.88 g (0.029 mol) of 2,3,5,6-tetramethyl-4-amino-p-phenylenediamine, 5.81 g (0.058 mol) of methyl isobutyl ketone, and 0.79 g of a platinum-on-carbon catalyst (containing 0.04 g of platinum) were reacted under a hydrogen atmosphere. The reaction system was heated from room temperature to 150°C over 1 hour, and then the hydrogen pressure was increased to approximately 2.94 MPa, maintaining the temperature and pressure stable. After 2 hours of reaction, the hydrogen was discharged from the autoclave, and the pressure was restored to normal. The reaction system was cooled to room temperature, and the catalyst and activated carbon in the reaction solution were filtered out. The crude product was separated by high-performance liquid chromatography to obtain 10 g of a new compound (O-4), which was characterized by nuclear magnetic resonance spectroscopy as the target compound (antioxidant O-4). The data are as follows: 1 H NMR (600MHz, CDCl3) δ7.20(t,J=7.9Hz,2H),6.85(d,J=7.9Hz,2H),6.80(t,J=7.2Hz,1H),5.40(s,1H),3.60-3.50(m,1H),3.32(s,1H),2. 16(s,12H),1.85-1.75(m,1H),1.56-1.48(m,1H),1.34-1.26(m,1H),1.22(d,J=6.2Hz,3H),1.01(d,J=6.6Hz,3H),0.99(d,J=6.6Hz,3H). 13C NMR (150MHz, CDCl3) δ146.44,144.13,132.11,129.27,126.33,118.66,114.79,113.25,47.15,47.06,25.21,23.12,22.69,21.21,18.48.

[0066] The target compound (antioxidant O-4) has the following structural formula:

[0067]

[0068] The reaction formula of the above reaction is as follows:

[0069]

[0070] Example 5

[0071] Under an inert gas nitrogen atmosphere, 16.11 g (0.066 mol, 1.1 eq) of 2,3,6-trimethyl-4-nitrobromobenzene, 0.552 g (0.0006 mol, 1%) of Pd2(dba)3, 1.416 g (0.003 mol, 5%) of XPhos, 16.58 g (0.12 mol, 2 eq) of K2CO3 and 5.58 g (0.06 mol) of aniline were added to a 500 mL three-necked flask and dispersed in 250 mL of isopropanol. The mixture was then refluxed at 110 ° C for 24 h. The reaction system was filtered, the extracts were separated, the organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the crude intermediate. The obtained crude intermediate was added to 1 L of ethanol, and 1.52 g of platinum-carbon catalyst (containing 0.076 g of platinum) was added. The hydrogen pressure was 0.2 MPa, and the reaction was carried out at 80 ° C for 24 hours. After the reaction was completed, it was cooled to room temperature, filtered, and the filter cake was washed with hot ethanol. After removing the solvent with a rotary evaporator, column chromatography was performed using 400 mesh silica gel powder. The eluent system was petroleum ether and ethyl acetate, and the gradient elution polarity selection range was petroleum ether: ethyl acetate (volume ratio) 10:1 to 3:1 to obtain 6.75 g of 2,3,5-trimethyl-4-amino-p-phenylenediamine.

[0072] 6.6 g (0.026 mol) of 2,3,6-trimethyl-4-amino-p-phenylenediamine, 5.21 g (0.050 mol) of methyl isobutyl ketone, and 0.66 g of platinum-carbon catalyst (including 0.033 g of platinum) were reacted under a hydrogen atmosphere. The reaction system was heated from room temperature to 150 °C within 1 h. oC, then hydrogen was pressurized to approximately 2.94 MPa, maintaining the temperature and pressure stable. After 2 hours of reaction, the hydrogen was discharged from the autoclave, the pressure was restored to normal, and the reaction system was cooled to room temperature. The catalyst and activated carbon in the reaction solution were filtered out, and the crude product was separated by high-performance liquid chromatography to obtain 8 g of a new compound, which was characterized by nuclear magnetic resonance spectroscopy as the target compound (antioxidant O-5). The data are as follows: 1 H NMR (600MHz, CDCl3) δ7.21(t,J=7.9Hz,2H),6.86(d,J=7.9Hz,2H),6.82(t,J=7.2Hz,1H),6.58(s,1H),5.40(s,1H),3.60-3.50(m,1H),3.32(s, 1H),2.16(s,9H),1.85-1.77(m,1H),1.55-1.48(m,1H),1.34-1.25(m,1 H), 1.22 (d, J = 6.2Hz, 3H), 1.01 (d, J = 6.6Hz, 3H), 0.99 (d, J = 6.6Hz, 3H). 13 C NMR (150MHz, CDCl3) δ146.49,144.18,132.17,129.28,126.46,119.62,119.54,118. 68,116.26,114.76,47.15,47.06,25.21,23.12,22.69,21.21,18.52,18.49,18.48.

[0073] The structural formula of the target compound (antioxidant O-5) is as follows:

[0074]

[0075] The reaction formula of the above reaction is as follows:

[0076]

[0077] Example 6

[0078] Under an inert gas nitrogen atmosphere, 15.2 g (0.066 mol, 1.1 eq) of 3,5-dimethyl-4-nitrobromobenzene, 0.183 g (0.0006 mol, 1%) of Pd(acac)2, 1.231 g (0.003 mol, 5%) of SPhos, 11.53 g (0.12 mol, 2 eq) of t-BuONa and 5.58 g (0.06 mol) of aniline were added to a 500 mL three-necked flask and dispersed in 250 mL of tert-butanol. The mixture was then refluxed at 120 ° C for 24 h. The reaction system was filtered, the liquid was extracted, the organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain a crude intermediate. In a hydrogen atmosphere, the obtained crude intermediate was added to 1 L of ethanol, 3.04 g of platinum-carbon catalyst (containing 0.152 g of platinum) was added, the hydrogen pressure was 1 MPa, and the reaction was carried out at 50° C. for 24 h. After the reaction was completed, it was cooled to room temperature, filtered, and the filter cake was washed with hot ethanol. The solvent was removed by rotary evaporation, and then column chromatography was performed using 400 mesh silica gel powder. The eluent system was petroleum ether and ethyl acetate, and the gradient elution polarity selection range was petroleum ether: ethyl acetate (volume ratio) 10:1 to 3:1 to obtain 8.95 g of the reaction intermediate 3,5-dimethyl-4-amino-p-phenylenediamine.

[0079] 8.80 g (0.036 mol) of the reaction intermediate 3,5-dimethyl-4-amino-p-phenylenediamine, 5.42 g (0.054 mol) of methyl isobutyl ketone, and 0.88 g of a platinum-carbon catalyst (containing 0.044 g of platinum) were reacted under a hydrogen atmosphere. The reaction system was heated from room temperature to 130°C within 1 hour, and then the hydrogen was pressurized to about 5 MPa, keeping the temperature and pressure stable. After reacting for 2 hours, the hydrogen was discharged from the autoclave and the pressure was restored to normal. At the same time, the reaction system was cooled to room temperature, the catalyst and activated carbon in the reaction solution were filtered out, and the crude product was separated by high performance liquid chromatography to obtain 10.5 g of a new compound, which was characterized as the target compound (antiaging agent O-1) by nuclear magnetic resonance spectroscopy.

[0080] Example 7

[0081] Under an inert gas nitrogen atmosphere, 13.82g (0.06mol, 1eq) 3,5-dimethyl-4-nitrobromobenzene, 0.135g (0.0006mol, 1%) Pd(OAc)2, 1.868g (0.003mol, 5%) BINAP, 39.1g (0.12mol, 2eq) Cs2CO3 and 5.58g (0.06mol) aniline were added to a 500mL three-necked flask and dispersed in 250mL 1,4-dioxane. The mixture was then placed at 90°C for 24h. The reaction system was filtered, the liquid was extracted, the organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain a crude intermediate. In a hydrogen atmosphere, the obtained crude intermediate was added to 1 L of ethanol, 0.7 g of platinum-carbon catalyst (containing 0.035 g of platinum) was added, the hydrogen pressure was 0.2 MPa, and the reaction was carried out at 100° C. for 24 h. After the reaction was completed, it was cooled to room temperature, filtered, and the filter cake was washed with hot ethanol. After removing the solvent with a rotary evaporator, column chromatography was performed using 400 mesh silica gel powder. The eluent system was petroleum ether and ethyl acetate, and the gradient elution polarity selection range was petroleum ether: ethyl acetate (volume ratio) 10:1 to 3:1 to obtain 7.6 g of the reaction intermediate 3,5-dimethyl-4-amino-p-phenylenediamine.

[0082] 7.33 g (0.03 mol) of the reaction intermediate 3,5-dimethyl-4-amino-p-phenylenediamine, 5.42 g (0.054 mol) of methyl isobutyl ketone, and 0.74 g of a platinum-carbon catalyst (containing 0.037 g of platinum) were reacted under a hydrogen atmosphere. The reaction system was heated from room temperature to 170°C within 1 hour, and then the hydrogen was pressurized to about 2 MPa, while maintaining the temperature and pressure stable. After reacting for 2 hours, the hydrogen was discharged from the autoclave and the pressure was restored to normal. At the same time, the reaction system was cooled to room temperature, the catalyst and activated carbon in the reaction solution were filtered out, and the crude product was separated by high-performance liquid chromatography to obtain 9.1 g of a new compound, which was characterized as the target compound (antioxidant O-1) by nuclear magnetic resonance spectroscopy.

[0083] Example 8

[0084] Under an inert gas nitrogen atmosphere, 16.58 g (0.072 mol, 1.2 eq) of 3,5-dimethyl-4-nitrobromobenzene, 0.693 g (0.0006 mol, 1%) of Pd(PPh3)4, 1.416 g (0.003 mol, 5%) of XPhos, 13.47 g (0.12 mol, 2 eq) of t-BuOK and 5.58 g (0.06 mol) of aniline were added to a 500 mL three-necked flask and dispersed in 250 mL of methanol. The mixture was then refluxed at 70 ° C for 24 h. The reaction system was filtered, the liquid was extracted, the organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain a crude intermediate. In a hydrogen atmosphere, the obtained crude intermediate was added to 1 L of ethanol, 1.66 g of platinum-carbon catalyst (containing 0.083 g of platinum) was added, the hydrogen pressure was 0.05 MPa, and the reaction was carried out at 80° C. for 24 h. After the reaction was completed, it was cooled to room temperature, filtered, and the filter cake was washed with hot ethanol. The solvent was removed by rotary evaporation, and then column chromatography was performed using 400 mesh silica gel powder. The eluent system was petroleum ether and ethyl acetate, and the gradient elution polarity selection range was petroleum ether: ethyl acetate (volume ratio) 10:1 to 3:1 to obtain 5.6 g of the reaction intermediate 3,5-dimethyl-4-amino-p-phenylenediamine.

[0085] 4.89 g (0.02 mol) of the reaction intermediate 3,5-dimethyl-4-amino-p-phenylenediamine, 4.02 g (0.04 mol) of methyl isobutyl ketone, and 0.49 g of a platinum-carbon catalyst (containing 0.025 g of platinum) were reacted under a hydrogen atmosphere. The reaction system was heated from room temperature to 140°C within 1 hour, and then the hydrogen was pressurized to about 4 MPa, while maintaining the temperature and pressure stable. After reacting for 2 hours, the hydrogen was discharged from the autoclave and the pressure was restored to normal. At the same time, the reaction system was cooled to room temperature, the catalyst and activated carbon in the reaction solution were filtered out, and the crude product was separated by high-performance liquid chromatography to obtain 6.2 g of a new compound, which was characterized as the target compound (antiaging agent O-1) by nuclear magnetic resonance spectroscopy.

[0086] Example 9

[0087] The existing antioxidant 4020 and the antioxidants D-1, O-1, O-2, O-3, and O-4 prepared above were respectively applied to raw isoprene rubber, and mixed and vulcanized using conventional mixing methods and formulas (see Table 1 for details). The performance of the corresponding rubber materials obtained was tested, and the test results are shown in Table 2.

[0088] The commonly used mixing process adopts two-stage mixing. During the first mixing, the speed is set to 80rpm, the isoprene rubber is put into the internal mixer for breaking the glue for 30s, and then 2 / 3 of the carbon black N234 is added and mixed for 1min, and then the remaining 1 / 3 of the carbon black N234 is added, mixed for 30s and then cleaned, and then stearic acid, zinc oxide and antioxidant are added after mixing for another 1min, and then cleaned, and then mixed for another 1min and then discharged at 150℃; the first masterbatch is parked for more than 4h before the second mixing; during the second mixing, the speed is set to 50rpm, the first masterbatch is put into the internal mixer, and the accelerator and sulfur are added after breaking the glue for 30s, and then cleaned after mixing for 30s. After mixing for 1min, the glue is discharged, and the discharge temperature does not exceed 100℃ to obtain the final rubber.

[0089] The final rubber mix is ​​vulcanized on a flat vulcanizer at a vulcanization temperature of 150° C. The vulcanization time for the tensile, tearing and dynamic performance test samples is (tc90+5) min; the vulcanization time for the elasticity, hardness, density and compression heat generation test samples is (tc90+10) min.

[0090] Table 1 Mixing formula of rubber compound with different antioxidants

[0091] Comparative rubber 1 Comparative rubber 2 M-1 M-2 M-3 M-4 Isoamyl gum 100 100 100 100 100 100 Carbon black N234 50 50 50 50 50 50 zinc oxide 4 4 4 4 4 4 stearic acid 2 2 2 2 2 2 Antioxidant 4020 1 Antioxidant D-1 1 Antioxidant O-1 1 Antioxidant O-2 1 Antioxidant O-3 1 Antioxidant O-4 1 Accelerator TBBS 1.2 1.2 1.2 1.2 1.2 1.2 Sulfur 1 1 1 1 1 1 total 159.2 159.2 159.2 159.2 159.2 159.2

[0092] Among them, comparative rubber material 1 and comparative rubber material 2 are rubber material formulas to which antioxidant 4020 and antioxidant D-1 prepared in comparative example 1 are added, respectively, and M-1, M-2, M-3, and M-4 are rubber material formulas to which antioxidants O-1, O-2, O-3, and O-4 prepared in examples 1-4 are added, respectively.

[0093] Table 2 Properties of rubber compounds / vulcanizates

[0094]

[0095]

[0096] As can be seen from Table 2, the p-phenylenediamine antioxidant provided by the present invention can achieve physical properties equivalent to or even better than those of the existing antioxidant 4020 when applied to isoprene rubber.

[0097] The vulcanized rubber materials M-1, M-2, M-3, and M-4 were extracted after aging, and the extracts were detected using ultra-high performance liquid chromatography-high resolution tandem mass spectrometry (UPLC-HRMS / MS), and no quinone compounds were detected. However, quinone compounds were detected in the vulcanized rubber materials of comparative rubber materials 1 and comparative rubber materials 2 after aging. This shows that the environmentally friendly para-aniline antioxidant provided by the present invention does not produce highly toxic quinone conversion products in the rubber residue, and is an environmentally friendly rubber additive.

[0098] The preparation methods of Examples 10-18 are the same as those of Example 1, and the structural formulas of the obtained antioxidants are shown in the following table:

[0099]

[0100] The above describes in detail the environmentally friendly p-phenylenediamine antioxidant provided by the present invention, its preparation method, and its application. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The above examples are merely intended to facilitate understanding of the methods and central concepts of the present invention. It should be noted that those skilled in the art may make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications fall within the scope of protection of the claims.

Claims

1. An environmentally friendly p-phenylenediamine antioxidant, characterized in that: It has the structure shown in formula (I): In the formula (I), R 1 、R 1’ Selected from C1-C 18 chain hydrocarbon group or alicyclic hydrocarbon group or H, R 2 、R 3 Selected from C1-C 18 Chain hydrocarbon group or R 2 With R 3 Forming a fat ring, R 4 、R 5 Selected from C1-C 18 Chain hydrocarbon group or R 4 With R 5 Forming an aliphatic ring; x = 0 or 1, y = 0 or 1, z = 0 or 1, w = 0 or 1, and at least one of x and w is 1, and at least one of y and z is 1, wherein when x and z are 1 at the same time, y and w are not 0 at the same time.

2. An environmentally friendly p-phenylenediamine antioxidant according to claim 1, characterized in that, The structure of formula (I) is Among them, R 1 、R 1’ Selected from C1-C 18 chain hydrocarbon group or alicyclic hydrocarbon group or H, R 2 、R 3 Selected from C1-C 18 Chain hydrocarbon group or R 2 With R 3 Formation of a fat ring.

3. An environmentally friendly p-phenylenediamine antioxidant according to claim 1, characterized in that, The structure of formula (I) is Among them, R 1 、R 1’ Selected from C1-C 18 Chain hydrocarbon or alicyclic hydrocarbon or H, R 3 、R 5 Selected from C1-C 18 chain hydrocarbon group.

4. An environmentally friendly p-phenylenediamine antioxidant according to claim 1, characterized in that, The structure of formula (I) is Among them, R 1 、R 1’ Selected from C1-C 18 chain hydrocarbon group or alicyclic hydrocarbon group or H, R 2 、R 3 Selected from C1-C 18 Chain hydrocarbon group or R 2 With R 3 Forming a fat ring, R 4 、R 5 Selected from C1-C 18 chain hydrocarbon group.

5. An environmentally friendly p-phenylenediamine antioxidant according to claim 1, characterized in that, The structure of formula (I) is: Among them, R 1 、R 1’ Selected from C1-C 18 chain hydrocarbon group or alicyclic hydrocarbon group or H, R 2 、R 3 Selected from C1-C 18 Chain hydrocarbon group or R 2 With R 3 Forming a fat ring, R 4 、R 5 Selected from C1-C 18 Chain hydrocarbon group or R 4 With R 5 Formation of a fat ring.

6. A method for preparing an environmentally friendly p-phenylenediamine antioxidant according to any one of claims 1 to 5, characterized in that: Aniline is subjected to a CN coupling reaction with p-bromonitrobenzene having a corresponding substituent, and the obtained coupling product is subjected to a reduction reaction in a hydrogen atmosphere under catalytic conditions to obtain a reaction intermediate, and the reaction intermediate is subjected to a reductive amination reaction with an aldehyde or a ketone under catalytic conditions to obtain the p-phenylenediamine antioxidant.

7. The method for preparing an environmentally friendly p-phenylenediamine antioxidant according to claim 6, wherein: The CN coupling reaction is carried out in an inert atmosphere, and the molar ratio of the aniline to the p-bromonitrobenzene having the corresponding substituent is 1:1.0-1.2; the catalyst of the CN coupling reaction is a palladium catalyst, and the palladium catalyst is selected from Pd2(dba)3, Pd(OAc)2, Pd(PPh3)4 or Pd(acac)2; the ligand of the palladium catalyst is selected from phosphine ligand XPhos, phosphine ligand SPhos or phosphine ligand BINAP; the base added in the CN coupling reaction is selected from K2CO3, Cs2CO3, t-BuOK or t-BuONa; the reaction solvent of the CN coupling reaction is selected from isopropanol, methanol, tert-butanol or 1,4-dioxane; the reaction temperature of the CN coupling reaction is 70-120°C.

8. The method for preparing an environmentally friendly p-phenylenediamine antioxidant according to claim 6, wherein: The catalyst for the reduction reaction is a platinum-carbon catalyst, and the amount of the platinum-carbon catalyst is 5-20% of the mass of the p-bromonitrobenzene having the corresponding substituents; the hydrogen pressure of the reduction reaction is 0.05-1 MPa, and the reaction temperature is 50-100° C.; The molar ratio of the reaction intermediate to the aldehyde or ketone is 1:1.5-2, the reaction temperature of the reductive amination reaction is 130-170° C., the reaction pressure is 2-5 MPa, and the catalyst is a platinum-carbon catalyst.

9. The method for preparing an environmentally friendly p-phenylenediamine antioxidant according to claim 7 or 8, characterized in that: The molar ratio of the aniline to the p-bromonitrobenzene having the corresponding substituent is 1:1.1, the palladium catalyst is Pd2(dba)3, the ligand of the palladium catalyst is XPhos, the base added in the CN coupling reaction is K2CO3, the reaction solvent of the CN coupling reaction is isopropanol, and the reaction temperature of the CN coupling reaction is 110°C; The amount of the platinum-carbon catalyst used in the reduction reaction is 10% of the mass of the p-bromonitrobenzene having the corresponding substituents. The hydrogen pressure of the reduction reaction is 0.2 MPa and the reaction temperature is 80°C.

10. Use of an environmentally friendly p-phenylenediamine antioxidant according to any one of claims 1 to 5 in rubber mixing or vulcanization, characterized in that: The antioxidant is applied to natural rubber or synthetic rubber, mixed, and vulcanized to obtain vulcanized rubber.

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