Method for preparing hindered phenol antioxygens by ester exchange process

Abstract

The invention discloses a method for preparing hindered phenol antioxygens by an ester exchange process, comprising the following steps of: adding reaction raw materials and toluene or mixed xylenes to a reaction kettle, and introducing N2 for protection; heating the reaction kettle to 130-150 DEG C; removing light components until the tower top temperature reaches the boiling point of the toluene or the boiling range lower limit of the mixed xylenes; adding an ester exchange reaction catalyst; when the temperature in the reaction kettle is 140-190 DEG C, starting regulating a reflux ratio controller to be in a total reflux state; when the tower top temperature reaches 63-635 DEG C, regulating the reflux ratio (quantity of reflux: recovery) to be 15-50:25 to recover carbinol; with the reaction, when the tower top temperature reaches 75-90 DEG C, regulating the reflux ratio (quantity of reflux: recovery) to be 5-50:5; and when the tower top temperature reaches the boiling point of the toluene or the boiling range lower limit of the mixed xylenes and is constant at the boiling point for 0.5-2h, finishing the reaction. The method has the advantages of small equipment investment, low cost and small pollution and is suitable for industrially producing the hindered phenol antioxygens.

Description

technical field [0001] The invention relates to a method for preparing hindered phenolic antioxidants by transesterification, in particular to a new process for preparing high-quality hindered phenolic antioxidants at low cost and high yield by adopting rectification technology to continuously distill methanol. Background technique [0002] Hindered phenolic antioxidants have excellent antioxidant properties and can inhibit the oxidative and thermal degradation of many organic compounds and polymers. They are widely used in polyolefins, polyamides, polyesters, ABS resins, synthetic rubbers, greases, coatings, lubricating oil etc. [0003] Hindered phenolic antioxidants are usually used as the main antioxidant of polymers, and they can exert excellent antioxidant performance when used in conjunction with auxiliary antioxidants such as thioesters and phosphites. Its main varieties are: pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 3-(3,5-di-tert...

AI Technical Summary

Problems solved by technology

[0007] 1. In order to ensure the smooth and rapid completion of the reaction, a higher degree of vacuum is required to completely remove the methanol generated by the reaction as soon as possible. Generally, this type of transesterification reaction is carried out at a relatively high reaction temperature. If there is a trace of air in the process The entry will seriously affect the product quality, so the vacuum method has high requirements on the airtightness of the reaction equipment, resulting in high investment in equipment

[0008] 2. Need to invest in the purchase of vacuum pumps and corresponding supporting equipment

[0009] 3. Removing methanol under high vacuum, due to the low boiling point of methanol, a large amount of methanol will enter the tail gas absorption system or vacuum system due to failure to condense in time, which is not conducive to the recovery and utilization of methanol; at the same time, because the discharged tail gas contains methanol, Increased investment in environmental protection due to the need for additional capture facilities

In order to increase the conversion rate of the reaction and reduce the reaction time, the reaction process needs to be completed continuously in a vacuum state, and the vacuum equipment needs to be continuously operated for a long time, thereby increasing energy consumption

[0011] 5. Processes such as vacuum realization and vacuum switching increase the complexity of process operations

[0013] When methanol is removed by ordinary distillation, it is necessary to add toluene or mixed xylene to remove methanol through the azeotrope formed with methanol, and the reaction temperature is very high. During the ordinary distillation, a large amount of solvent will be removed from the reaction system. In order to ensure that methanol is removed completely so that the reaction is carried out completely, it is necessary to add a large amount of solvent in the reaction process, which not only increases the amount of solvent used, but also greatly reduces the production efficiency of the single reactor; at the same time, in the added reaction solvent It will inevitably contain trace amounts of moisture and oxygen, which will lead to the deterioration of the reaction, the increase of side reactions, and the quality problems of the product

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