Quinoline anti-aging agent and preparation method thereof

Abstract

The invention provides a quinoline anti-aging agent and a preparation method thereof, and belongs to the technical field of fine chemical engineering. The preparation method of the quinoline anti-aging agent comprises the following steps: enabling 2, 4-dimethyl-3-pentene-2-amine to react with 4-bromophenylaniline or bis (4-bromophenyl) amine of which the amino group is protected, so as to obtain a quaternary amine anti-aging agent; methylating the quaternary amine anti-aging agent, and removing an amino protecting group to obtain the quinoline anti-aging agent. The quinoline anti-aging agent prepared by the preparation method disclosed by the invention is used in the field of rubber, not only has a better ozone protection effect, but also can improve the phenomenon that the anti-aging agent is easy to migrate out and discolor in a rubber product.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, specifically to a quinoline-based antioxidant and its preparation method. Background Technology

[0002] Many materials, such as plastics, elastomers, elastomer products (tires, belts, hoses, bushings, supports, shock absorbers, etc.), lubricants, and petroleum products (such as hydraulic fluids, oils, fuels, and oil / fuel additives for automotive and aviation applications), are prone to aging when exposed to light, heat, oxygen, ozone, and repeated mechanical action over a long period of time. Anti-aging agents can prevent or delay the aging of these products.

[0003] The addition of antioxidants must not adversely affect the properties of rubber products, such as reducing their mechanical properties, which would affect their service life. Furthermore, existing antioxidants often exhibit poor ozone protection and are prone to migration and discoloration. Additionally, the existing antioxidant RD, when applied to rubber products, suffers from excessively long scorch times, impacting processing efficiency and requiring further reduction.

[0004] Patent document CN104017122B discloses a high-efficiency quinoline antioxidant and its preparation. This antioxidant retains the excellent resistance to thermo-oxidative aging under dynamic and static conditions of antioxidant RD with high dimer content, while also mitigating the problem of dimer migration loss and extending the service life of rubber products. However, compared with antioxidant RD, the tensile strength of the rubber compound prepared with this quinoline antioxidant is slightly reduced. Summary of the Invention

[0005] In view of this, the present invention provides a quinoline antioxidant, its preparation method and application, which not only has a better ozone protection effect in the rubber field, but also improves the phenomenon of antioxidants migrating out and discoloring in rubber products.

[0006] To achieve the above objectives, the present invention provides a quinoline antioxidant, wherein the structural formula of the quinoline antioxidant is as follows: or .

[0007] A method for preparing a quinoline antioxidant includes the following steps: reacting 2,4-dimethyl-3-penten-2-amine with amino-protected 4-bromophenylaniline or bis(4-bromophenyl)amine to obtain a quaternary ammonium antioxidant; methylating the quaternary ammonium antioxidant and removing the amino protecting group to obtain a quinoline antioxidant.

[0008] Furthermore, the specific preparation method of quinoline antioxidants is as follows: (1) Mix 4-bromophenylaniline or bis(4-bromophenyl)amine with a solvent, heat to 40-50°C, and then add ditert-butyl dicarbonate ((BOC)2O) dropwise to react. After the reaction is complete, solution A is obtained. (2) Add solid alkali and polymerization inhibitor to solution A, heat to 70-100℃, and then add 2,4-dimethyl-3-penten-2-amine (CAS: 64760-62-9). After the reaction is complete, solution B containing quaternary ammonium antioxidant is obtained. (3) Methyl bromide is continuously introduced into solution B to carry out methylation of quaternary ammonium antioxidants. After the reaction is completed, acid is added to neutralize and remove the amino protecting group. Then water is added to precipitate, filtered, and washed to obtain quinoline antioxidants.

[0009] Further, in step (1), the solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide (DMSO), and 1,4-dioxane; preferably, the solvent is dimethyl sulfoxide (DMSO).

[0010] Further, in step (1), the mass ratio of 4-bromophenylaniline or bis(4-bromophenyl)amine to solvent is 1:2 to 10, for example 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10; preferably, the mass ratio of 4-bromophenylaniline or bis(4-bromophenyl)amine to solvent is 1:3 to 4.

[0011] Further, in step (1), the molar ratio of 4-bromophenylaniline or bis(4-bromophenyl)amine to (BOC)2O is 1:0.5~0.6, for example 1:0.5, 1:0.52, 1:0.54, 1:0.56, 1:0.58, 1:0.6. Preferably, the molar ratio of 4-bromophenylaniline or bis(4-bromophenyl)amine to (BOC)2O is 1:0.5.

[0012] Further, in step (1), the dropping time of (BOC)₂O is 30~90 min, for example 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min. Preferably, the dropping time of (BOC)₂O is 50~60 min.

[0013] Further, in step (1), the temperature is heated to 40-50°C, for example, 40°C, 45°C, 50°C, preferably to 45°C.

[0014] Furthermore, in step (2), the solid alkali is one of caustic soda flakes, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate; preferably, the solid alkali is caustic soda flakes.

[0015] Further, in step (2), the molar ratio of the solid base to 4-bromophenylaniline or bis(4-bromophenyl)amine is 2 to 5:1, for example 2:1, 3:1, 4:1, 5:1; preferably, the molar ratio of the solid base to 4-bromophenylaniline or bis(4-bromophenyl)amine is 3:1.

[0016] Furthermore, in step (2), the polymerization inhibitor is one of p-benzoquinone, hydroquinone, p-hydroxyanisole, and 2-tert-butylhydroquinone; preferably, the polymerization inhibitor is 2-tert-butylhydroquinone.

[0017] Furthermore, in step (2), the polymerization inhibitor is added at a mass of 0.5% to 2% of the mass of 4-bromophenylaniline or bis(4-bromophenyl)amine, for example, 0.5%, 1%, 1.5%, 2%, preferably, at a mass of 1% of the mass of 4-bromophenylaniline or bis(4-bromophenyl)amine.

[0018] Further, in step (2), the temperature is raised to 70-100°C, for example 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C. Preferably, a solid alkali and a polymerization inhibitor are added, and the temperature is raised to 90°C.

[0019] Furthermore, in step (2), the molar ratio of 2,4-dimethyl-3-penten-2-amine to 4-bromophenylaniline is 1 to 1.2:1, for example 1:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1. Preferably, the molar ratio of 2,4-dimethyl-3-penten-2-amine to 4-bromophenylaniline is 1 to 1.1:1.

[0020] Furthermore, in step (2), the dropping rate of 2,4-dimethyl-3-penten-2-amine is controlled at 1~10 g / min, for example 1 g / min, 2 g / min, 3 g / min, 4 g / min, 5 g / min, 6 g / min, 7 g / min, 8 g / min, 9 g / min, 10 g / min, preferably, the dropping rate is controlled at 3~5 g / min.

[0021] Furthermore, in step (3), the molar ratio of the introduced methyl bromide to 4-bromophenylaniline is 1.1 to 1.5:1, for example 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.35:1, 1.4:1, 1.45:1, 1.5:1. Preferably, the molar ratio of methyl bromide to 4-bromophenylaniline is 1.2 to 1.4:1.

[0022] Furthermore, in step (3), the rate at which methyl bromide is introduced is 3~10 ml / min, for example 3 ml / min, 4 ml / min, 5 ml / min, 6 ml / min, 7 ml / min, 8 ml / min, 9 ml / min, 10 ml / min.

[0023] Furthermore, in step (3), a dilute acid is added to neutralize and remove the amino protecting group. The dilute acid is one of hydrochloric acid with a mass fraction of 10%, sulfuric acid with a mass fraction of 30%, formic acid, and acetic acid. Preferably, the dilute acid is hydrochloric acid with a mass fraction of 10%.

[0024] Furthermore, in step (3), dilute acid is added to neutralize and remove the amino protecting group. Dilute acid is added until the pH is kept ≤1 and remains unchanged for no less than 30 minutes to achieve the purpose of acid-base neutralization and removal of amino protecting groups.

[0025] Furthermore, in step (3), the mass of water added and precipitated is the same as the total mass of the mother liquor.

[0026] Further, in step (2), the molar ratio of 2,4-dimethyl-3-penten-2-amine to bis(4-bromophenyl)amine is 2~2.2:1, for example 2:1, 2.05:1, 2.1:1, 2.15:1, 2.2:1, preferably 2.05~2.1:1; in step (3), the molar ratio of the introduced methyl bromide to bis(4-bromophenyl)amine is 2.1~2.5:1, for example 2.1:1, 2.15:1, 2.2:1, 2.25:1, 2.3:1, 2.35:1, 2.4:1, 2.45:1, 2.5:1, preferably 2.2~2.4:1.

[0027] The above-described technical solution of the present invention has at least the following beneficial effects: The quinoline antioxidant obtained by the method of this invention is in solid form. Solid antioxidants are more convenient to store and transport, and have lower costs. When used as an antioxidant in the rubber industry, the quinoline antioxidant of this invention not only shortens scorch time and improves the tensile strength of rubber compounds, but also provides better ozone protection and mitigates the phenomenon of antioxidants migrating and discoloring in rubber products.

[0028] This invention effectively shortens the reaction time by changing the way raw materials are added, such as changing the addition of (BOC)2O from a single addition to a dropwise addition. This reduces the reaction time by half, making the reaction of raw materials more complete and thorough, improving the conversion rate and yield of raw materials, saving raw material costs, and enhancing economic benefits.

[0029] The preparation method of this invention uses 4-bromophenylaniline or bis(4-bromophenyl)amine as raw materials, combined with the dropwise addition of (BOC)2O and the use of methyl bromide in subsequent reactions, resulting in fewer reaction impurities, simpler post-processing, and higher product purity reaching over 88%. This makes it more effective as an antioxidant in the rubber industry.

[0030] This invention uses methyl bromide to methylate quaternary ammonium antioxidants. Because methyl bromide is easy to control in the reaction system of this application, and bromine is removed during the reaction process, corresponding to the 4-bromophenylaniline or bis(4-bromophenyl)amine mentioned earlier, no other new element impurities are introduced. If other halogenated 4-halogenated phenylaniline is used, other new elements will be introduced, increasing the difficulty of subsequent processing. Other methyl halides are not easy to control in the reaction system, making the reaction of this application difficult to carry out. Attached Figure Description

[0031] Figure 1 Figure 1 shows the results of a 72-hour static ozone aging test on different rubber compounds. Figure 2 The results of a 72-hour dynamic ozone aging test for different rubber compounds are shown in the figure. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0033] Example 1 A method for preparing a quinoline-based antioxidant includes the following steps: (1) In a 5L jacketed reactor, 248g of 4-bromophenylaniline and 744g of DMSO solvent were added. The mixture was stirred thoroughly and kept in a constant state to ensure that the two were dissolved and mixed evenly. The mixture was heated to 45°C and then 118g of (BOC)2O was added dropwise to carry out the reaction. The dropwise addition time of (BOC)2O was controlled to be 60min. The reaction was considered to be complete when the content of 4-bromophenylaniline was less than 0.2% (high performance liquid chromatography). Solution A was obtained after the reaction was completed. (2) Add 120g of caustic soda flakes and 2.5g of 2-tert-butylhydroquinone to solution A, and heat to 90℃; add 118.8g of 2,4-dimethyl-3-penten-2-amine dropwise at a rate of about 4g / min for about 30min to obtain solution B containing quaternary ammonium antioxidants. (3) After the reaction was complete, 122.2 g of methyl bromide was slowly introduced into solution B for methylation over a period of about 10 min. After the reaction was confirmed to be complete by liquid chromatography, 10% hydrochloric acid was added for neutralization and the pH was adjusted to 1. The pH was then maintained at a constant level for 30 min. Then, an equal amount of water was added to precipitate the product. The solution was filtered, washed, and quinoline antioxidant was obtained with a yield of 85.42% based on 4-bromophenylaniline and a liquid chromatography purity of 90.72%.

[0034] The specific reaction equation for this embodiment is as follows:

[0035] Example 2 A method for preparing a quinoline-based antioxidant includes the following steps: (1) In a 5L jacketed reactor, 327g of bis(4-bromophenyl)amine and 981g of DMSO solvent were added. The mixture was stirred thoroughly and kept in a constant temperature to ensure that the two substances were dissolved and mixed evenly. The temperature was then heated to 45°C. Then, 118g of di-tert-butyl dicarbonate ((BOC)₂O) was added dropwise to carry out the reaction. The dropwise addition time of di-tert-butyl dicarbonate ((BOC)₂O) was controlled to be 60min. The reaction was considered complete when the content of 4-bromophenylaniline was less than 0.2% (HPLC). Solution A was obtained after the reaction was completed. (2) After the reaction is complete, add 120g of caustic soda flakes and 2.5g of 2-tert-butylhydroquinone to solution A and heat to 90℃; add 232g of 2,4-dimethyl-3-penten-2-amine dropwise at a rate of about 4g / min for about 58min, and then add solution B containing quaternary ammonium antioxidants. (3) After the reaction was complete, 218.4 g of methyl bromide was slowly introduced into solution B for methylation over a period of about 20 min. After the reaction was confirmed to be complete by liquid chromatography, 10% hydrochloric acid was added to neutralize the reaction and the pH was adjusted to 1. The pH was then maintained at 1 for 30 min. Then, water of equal mass to the mother liquor was added to precipitate the precipitate. The solution was filtered, washed, and a quinoline antioxidant was obtained with a yield of 82.76% based on bis(4-bromophenyl)amine and a liquid chromatography purity of 88.61%.

[0036] The specific reaction equation for Example 2 is as follows:

[0037] Comparative Example 1 (1) In a 5L jacketed reactor, 248g of 4-bromophenylaniline and 744g of DMSO solvent were added. The mixture was stirred thoroughly and kept in the reactor until it was dissolved and mixed evenly. The reactor was heated to 45°C, and then 118g of (BOC)2O was added at once to carry out the reaction. Compared with Example 1, the reaction time was extended by two times. The content of 4-bromophenylaniline was still higher than 10% by detection. The raw materials were not completely reacted, so the experiment was not carried out further.

[0038] Performance verification 1. Rubber compound formulation and preparation Table 1 Rubber compound formulation

[0039] The preparation of the rubber compound consists of a single-stage mixing process and a two-stage mixing process. The single-stage mixing process is as follows: Weigh the raw materials according to the formula ratio in Table 1. Add 45 parts of natural rubber NR, 55 parts of butadiene rubber BR, 45 parts of carbon black N330, 4.375 parts of zinc oxide ZnO-80, 1.8 parts of protective wax H3241, 2 parts of stearic acid, and 2 parts of antioxidant to a mixer. The rotor speed is 70 rpm, the pressure is 20 MPa, the heating rate is 10℃ / 10 minutes, the temperature is raised to 120℃, held for 5 minutes, and then further heated to 180℃. Discharge the rubber to obtain the primary compound. The two-stage mixing process is as follows: Add the primary compound to the mixer, add 1.5 parts of sulfur and 1 part of accelerator NS, and mix for 1 minute at a pressure of 10 MPa and a temperature of 80℃, with a rotation speed of 15 rpm. After completion, the rubber compound is obtained.

[0040] 2. Test methods for various performance parameters of rubber compounds Processing performance test: A scorch test was conducted using a Mooney viscometer in accordance with the national standard GB / T 1233-92.

[0041] Vulcanization characteristics: The P3555 B2 disc vulcanizer manufactured by Beijing Huanfeng Rubber & Plastics Machinery Manufacturing Plant was used for testing according to GB / T9869-1997. The test temperature was 160℃ and the test time was 60 min.

[0042] Mechanical properties: The tensile properties of the vulcanizate were determined using a CMT 4104 electronic tensile testing machine manufactured by Shenzhen Xin Sansi Materials Testing Co., Ltd., in accordance with GB / T 528-2009. The compression set was determined according to GB / T 7759-1996 using cylindrical specimens of 29.0 mm × 12.5 mm. The aging conditions were: compression set at 100 ℃ for 72 h, with a pre-compression rate of 25%.

[0043] Ozone resistance performance: The evaluation standard for ozone protection effect test results is based on GB / T 11206-2009 "Rubber Aging Test - Surface Cracking Method" to test ozone resistance performance.

[0044] 3. Experimental Results 1. The processing characteristics of each rubber compound are shown in Table 2 below: Table 2 Processing characteristics of the rubber compound

[0045] As can be seen from Table 2, compared with antioxidant 4020 and antioxidant RD, the addition of the product in the embodiment of the present invention shortens the scorch time t5 of the compound at 100°C, reduces the Mooney viscosity Mn / Mv, and improves the processing performance.

[0046] 2. The vulcanization characteristics of the rubber compound are shown in Table 3 below: Table 3. Vulcanization characteristics of rubber compounds

[0047] Note: tc10 is the initial vulcanization time, tc90 is the positive vulcanization time, MH is the maximum torque, and ML is the minimum torque.

[0048] As can be seen from Table 3, compared with antioxidant 4020 and antioxidant RD, the addition of the products in each embodiment of the present invention improves the vulcanization rate and vulcanization crosslinking degree of the compound.

[0049] 3. The mechanical properties of the rubber compound are shown in Tables 4 and 5 below: Table 4 Mechanical properties before aging test

[0050] Note: M100 is the stress when the rubber compound is stretched to 100% of its original length; M300 is the stress when the rubber compound is stretched to 100% of its original length.

[0051] Table 5 Mechanical properties after aging test

[0052] As can be seen from Tables 4 and 5, before the aging test, compared with antioxidants 4020 and RD, the addition of antioxidants to the rubber compound improved the tensile strength and stress at a given elongation of the vulcanizate. After the aging test, the products of each embodiment of the present invention still exhibited good mechanical properties, while the mechanical properties of antioxidants 4020 and RD were slightly inferior to those of the product embodiments.

[0053] 4. The ozone resistance of the rubber compound, such as Figure 1 and Figure 2 As shown, Figure 1This is a graph showing the static ozone aging test results of the obtained rubber compound after 72 hours. Figure 2 This is a graph showing the results of a 72-hour dynamic ozone aging test on the obtained rubber compound. From... Figure 1 and Figure 2 It can be seen that the rubber compound containing the product of this invention exhibits better ozone resistance and colorfastness compared to the rubber compound containing antioxidants 4020 and RD. It is less prone to blooming and maintains its surface color even after long-term use. In summary, the antioxidant prepared by the method of this invention not only has excellent ozone protection but also effectively solves the problem of easy migration and color change in organic antioxidants, demonstrating superior performance in the anti-aging of rubber materials.

[0054] Example 3 A method for preparing a quinoline-based antioxidant includes the following steps: (1) In a 5L jacketed reactor, 248g of 4-bromophenylaniline and 992g of DMSO solvent were added. The mixture was stirred thoroughly and kept in a constant state to ensure that the two were dissolved and mixed evenly. The mixture was heated to 50°C and then 110g of (BOC)2O was added dropwise to carry out the reaction. The dropwise addition time of (BOC)2O was controlled to be 30min. The reaction was considered to be complete when the content of 4-bromophenylaniline was less than 0.2% (high performance liquid chromatography). Solution A was obtained after the reaction was completed. (2) Add 212g of sodium carbonate and 1.24g of p-benzoquinone to solution A, and heat to 100℃; add 118.8g of 2,4-dimethyl-3-penten-2-amine dropwise at a rate of about 3g / min for about 40min to obtain solution B containing quaternary ammonium antioxidants. (3) After the reaction is complete, 114g of methyl bromide is slowly introduced into solution B for methylation over a period of about 8 minutes. After the reaction is complete as detected by liquid chromatography, 30% sulfuric acid is added for neutralization and the pH is adjusted to 1. The pH is then maintained at 1 for 30 minutes. Then, an equal amount of water is added to precipitate the solution, which is then filtered, washed, and the quinoline antioxidant is obtained.

[0055] Example 4 A method for preparing a quinoline-based antioxidant includes the following steps: (1) In a 5L jacketed reactor, 248g of 4-bromophenylaniline and 2480g of DMSO solvent were added. The mixture was stirred thoroughly and kept in the reactor until it was dissolved and mixed evenly. The reactor was heated to 50°C and then 130.9g of (BOC)2O was added dropwise to carry out the reaction. The dropwise addition time of (BOC)2O was controlled to be 90min. The reaction was considered to be complete when the content of 4-bromophenylaniline was less than 0.2% (high performance liquid chromatography). Solution A was obtained after the reaction was completed. (2) Add 200g of caustic soda flakes and 3.72g of hydroquinone to solution A, and heat to 80℃; add 135.8g of 2,4-dimethyl-3-penten-2-amine dropwise at a rate of about 10g / min for about 14min to obtain solution B containing quaternary ammonium antioxidants. (3) After the reaction is complete, 132.9 g of methyl bromide is slowly introduced into solution B for methylation. The introduction time is about 5 min. After the reaction is complete as detected by liquid chromatography, formic acid is added for neutralization and the pH is adjusted to 1. The pH is maintained unchanged for 30 min. Then, water of the same mass as the above mother liquor is added to precipitate the product. The product is filtered, washed, and quinoline antioxidant is obtained.

[0056] Example 5 A method for preparing a quinoline-based antioxidant includes the following steps: (1) In a 5L jacketed reactor, 248g of 4-bromophenylaniline and 496g of DMSO solvent were added. The mixture was stirred thoroughly and kept in the reactor until it was dissolved and mixed evenly. The reactor was heated to 40°C and then 118g of (BOC)2O was added dropwise to carry out the reaction. The dropwise addition time of (BOC)2O was controlled to be 50min. The reaction was considered to be complete when the content of 4-bromophenylaniline was less than 0.2% (high performance liquid chromatography). Solution A was obtained after the reaction was completed. (2) Add 252g of sodium bicarbonate and 4.96g of p-hydroxyanisole to solution A and heat to 70℃; add 124.5g of 2,4-dimethyl-3-penten-2-amine dropwise at a rate of about 5g / min for about 24min to obtain solution B containing quaternary ammonium antioxidants. (3) After the reaction was complete, 142.4 g of methyl bromide was slowly introduced into solution B for methylation over a period of about 7 minutes. After the reaction was confirmed to be complete by liquid chromatography, acetic acid was added for neutralization and the pH was adjusted to 1. The pH was then maintained at 1 for 30 minutes. Then, water of equal mass to the mother liquor was added to precipitate the product. The solution was filtered, washed, and the quinoline antioxidant was obtained.

[0057] Example 6 This embodiment is basically the same as Example 2, except that the amount of 2,4-dimethyl-3-penten-2-amine used is 226.4g and the amount of methyl bromide used is 199.4g.

[0058] Example 7 This embodiment is basically the same as Example 2, except that the amount of 2,4-dimethyl-3-penten-2-amine used is 237.7g and the amount of methyl bromide used is 227.8g.

[0059] Example 8 This embodiment is basically the same as Example 2, except that the amount of 2,4-dimethyl-3-penten-2-amine used is 249g and the amount of methyl bromide used is 237.3g.

Claims

1. A quinoline-based antioxidant, characterized in that: The structural formula of the quinoline-based antioxidant is as follows: or .

2. The method for preparing the quinoline antioxidant according to claim 1, characterized in that, Includes the following steps: 2,4-Dimethyl-3-penten-2-amine is reacted with amino-protected 4-bromophenylaniline or bis(4-bromophenyl)amine to obtain quaternary ammonium antioxidants; the quaternary ammonium antioxidants are then methylated and the amino protecting group is removed to obtain quinoline antioxidants.

3. The preparation method according to claim 2, characterized in that, The specific preparation method of quinoline-based antioxidants is as follows: (1) Mix 4-bromophenylaniline or bis(4-bromophenyl)amine with a solvent, heat to 40-50℃, and then add (BOC)2O dropwise to react. After the reaction is complete, solution A is obtained. (2) Add solid alkali and polymerization inhibitor to solution A, heat to 70-100℃, and then add 2,4-dimethyl-3-penten-2-amine dropwise. After the reaction is complete, solution B containing quaternary ammonium antioxidant is obtained. (3) Methyl bromide is continuously introduced into solution B to carry out methylation of quaternary ammonium antioxidants. After the reaction is completed, acid is added to neutralize and remove the amino protecting group. Then water is added to precipitate, filtered, and washed to obtain quinoline antioxidants.

4. The preparation method according to claim 3, characterized in that, In step (1), the solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and 1,4-dioxane; In step (1), the mass ratio of 4-bromophenylaniline or bis(4-bromophenyl)amine to solvent is 1:2~10.

5. The preparation method according to claim 3, characterized in that, In step (1), the molar ratio of 4-bromophenylaniline or bis(4-bromophenyl)amine to (BOC)₂O is 1:0.5~0.6; The dropping time for (BOC)2O is 30~90 min.

6. The preparation method according to claim 3, characterized in that, In step (2), the solid alkali is one of caustic soda flakes, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate; the molar ratio of the solid alkali to 4-bromophenylaniline or bis(4-bromophenyl)amine is 2~5:1; The polymerization inhibitor is one of p-benzoquinone, hydroquinone, p-hydroxyanisole, and 2-tert-butylhydroquinone; the polymerization inhibitor is added at a mass of 0.5% to 2% of the mass of 4-bromophenylaniline or bis(4-bromophenyl)amine.

7. The preparation method according to claim 3, characterized in that, In step (2), the molar ratio of 2,4-dimethyl-3-penten-2-amine to 4-bromophenylaniline is 1~1.2:1, and the dropping rate of 2,4-dimethyl-3-penten-2-amine is controlled at 1~10 g / min; in step (3), the molar ratio of the introduced methyl bromide to 4-bromophenylaniline is 1.1~1.5:1; Alternatively, in step (2), the molar ratio of 2,4-dimethyl-3-penten-2-amine to bis(4-bromophenyl)amine is 2~2.2:1; in step (3), the molar ratio of the introduced methyl bromide to bis(4-bromophenyl)amine is 2.1~2.5:

1.

8. The preparation method according to claim 3 or 7, characterized in that, The infusion rate of methyl bromide is 3~10 ml / min.

9. The preparation method according to claim 3, characterized in that, In step (3), a dilute acid is added to neutralize and remove the amino protecting group. The dilute acid is one of hydrochloric acid with a mass fraction of 10%, sulfuric acid with a mass fraction of 30%, formic acid, and acetic acid.

10. The preparation method according to claim 3, characterized in that, In step (3), dilute acid is added to neutralize and remove the amino protecting group. Dilute acid is added until the pH is kept ≤1 and kept unchanged for no less than 30 minutes.

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