The use and preparation method of antioxidant 4020_Kain Industrial Additive

Background and overview^[1]

There are many factors that cause rubber to age. Research shows that the main factors include oxygen, ozone, trace amounts of variable metals, sunlight, ultraviolet rays, and mold corrosion. Flexural fatigue mainly increases the contact area between rubber molecules and oxygen, thereby accelerating its aging. At present, p-phenylenediamine antioxidants are the most widely used antioxidants in the rubber industry. They can inhibit ozone aging, fatigue aging, thermal oxygen aging and catalytic oxidation of metal ions in rubber products. Anti-aging agent 4020 is a gray-black solid or scaly substance with a molecular weight of 268.41, an ash content of less than 0.1%, a relative density of 0.986 to 1.000 (60°C), and a melting point of 40 to 50°C. Soluble in acetone, ethyl acetate, dichloroethane, benzene and toluene, insoluble in water. Storage stable. It has good protective effect against ozone and flex fatigue aging, and also has good protective effect against oxygen, thermal aging and harmful metals such as copper and manganese. Mainly used as pollution-type antioxidant for natural rubber and synthetic rubber. Used in the manufacture of tires, tapes and other industrial rubber products, the general dosage is 0.5 to 1.5 parts, with a maximum of 3 parts. Major foreign manufacturers include Monsanto, UOP, Uniroyal, Vanderbilt, Goodyear and other companies in the United States, Bayer Company in Germany, and I.C.I. Company in the United Kingdom. China is mainly produced by Nanjing Chemical Plant.

Purpose^[2]

Anti-aging agent 4020 is mainly used as a rubber antioxidant. In addition to its good antioxidant properties, it also has the effects of resisting ozone, resisting flex cracking, and inhibiting harmful metals such as copper and manganese. Its performance is similar to the antioxidant 4010NA, but its toxicity and skin irritation are less than 4010NA, and its solubility in water is better than 4010NA (washing loss rate: 4010NA is 50%, while 4020 is only 15% to 20%) . It is suitable for natural, cis-butadiene, isopentyl, nitrile and chloroprene rubber. It can be used in the preparation of tires, tapes and many other industrial rubber products. The general dosage is 0.5% to 1.5%. This product is not suitable for making light-colored products due to serious pollution. In the plastics industry, this product can be used as a thermal oxygen stabilizer for polyethylene, polypropylene and acrylic resins. In the toxicity test of this product, the oral LD₅₀ for mice was 2500mg/kg.

Preparation^[3-5]

Method 1: The synthesis process of rubber antioxidant 4020 includes the following steps:

1) Pretreatment of the catalyst: Add the catalyst and methyl isobutyl ketone to the reaction kettle, pass in hydrogen 1.0~4.0MPa, the reaction time is 1 hour, the reaction temperature is 110 degrees, filter to obtain the pretreated catalyst;

2) Add p-aminodiphenylamine and methyl isobutyl ketone to the reaction kettle at a molar ratio of 1:2.5~4.5, and add the catalyst pretreated in step 1 with a mass percentage of p-aminodiphenylamine of 20~25%. Pour in hydrogen gas at 1.0~4.0MPa, the reaction temperature is 100~130 degrees, and the reaction time is 3~6 hours. After the reaction is completed, the temperature is cooled to room temperature, the pressure is released and the material is discharged to obtain the hydrogenation reaction liquid;

3) Filter the hydrogenation reaction liquid obtained in step 2 with a sand-core funnel, recover the catalyst and use it. The filtrate is distilled under normal pressure to evaporate methyl isobutyl ketone and use it for recovery, and continue to switch to vacuum distillation with a vacuum degree of 0.099MPa. When no more fractions evaporate, pour out the residue after cooling down and leave it for 24 hours to obtain antioxidant 4020 solid;

4) Directly put the catalyst recovered in step 3 into step 2, add 2% by weight of the catalyst pretreated in step 1, and repeat steps 2 and 3 for the rest.

Method 2: A method for preparing rubber antioxidant 4020, which is characterized in that it is synthesized according to the following steps:

(1) Add methyl isobutyl ketone and p-aminophenol with a molar ratio of 2~3:1 into the reaction kettle, heat and stir to 120℃~140℃, boil and water will come out, and the condensation reaction After the generated water is removed, heating is stopped after the reaction is completed, and a large amount of crystals are formed in the reactor;

(2) Add formic acid to the condensation liquid, and after full reaction, distill out the unreacted methyl isobutyl ketone under normal pressure, and perform a reflux reaction, keeping the temperature at 130°C~140°C;

(3) Cool the product of reaction step (2), lower the temperature to 60℃~80℃, add aniline and catalyst, raise the temperature to 118℃~122℃, boil and water will come out, keep it at 120℃, and judge the end point of the reaction ;

(4) Reduce the reaction temperature to 55℃~65℃, add sodium hydroxide, stir to neutralize unreacted formic acid, add a certain amount of adsorbent, stir for 3-5 hours, vacuum filter, discard the residue and keep the liquid , the filtrate is vacuum distilled, leaving the bottom product, which is cooled to obtain product 4020.

Method 3: A safe and low-cost preparation method for rubber antioxidant 4020, including the following steps:

The first step involves the reaction of p-aminophenol and methyl isobutyl ketone to produce p-1,3-dimethylbutylene aminophenol. The molar ratio of methyl isobutyl ketone to p-aminophenol is 2.5/1 , the reaction temperature is controlled at 133°C and the time is 15h;

The second step is to react p-1,3-dimethylbutylene phenol, the product of the first reaction, with formic acid to generate N-(1,3-dimethylbutyl) p-aminophenol, and formic acid and The molar ratio of p-aminophenol is 1.1/1, the reaction temperature is controlled at 108°C, and the time is 5h;

The third step is to react the product N-(1,3-dimethylbutyl) p-aminophenol with aniline under the action of a catalyst to form 4020. The molar ratio of aniline to p-aminophenol is 1.5/1, the reaction temperature is controlled at 120°C, and the reaction time is 10h.