DD268938B1 - PROCESS FOR THE PREPARATION OF THIODIPROPIONIC ACID ESTERS - Google Patents

Abstract

The invention relates to a process based on the reaction of thiodipropionitrile, hydrochloric acid and long-chain alcohols in the presence of catalysts for the preparation of Thiodipropionsäureestem, which are used as antioxidants for the stabilization of polyolefins. Goal and task of the invention are to enable the production of Thiodipropionsäureestem in high product quality and low HCI emission by changing technological parameters. According to the invention, the objective is met when the synthesis is divided into two reaction steps and each reaction step is carried out in reaction apparatuses adapted in each case to the reaction conditions. In the first stage, the metered addition of hydrochloric acid in dependence on the reaction rate while maintaining a constant Reaktiunstemperatur.

Description

If the reaction temperature falls below the set point, hydrogen chloride accumulates and, if the temperature increases, the reaction proceeds more vigorously than desired. The consequence is the formation of a Thiodipropionsäureesters with high acid number and stronger coloring in the final stage. Therefore, the set target temperature should be maintained with an accuracy of ± 1K.

If the deviation exceeds the setpoint, the HCI supply is interrupted by a control.

After addition of the hydrochloric acid, an after-reaction takes place at temperatures around 70 ° C. There is then a mixture of aqueous thiodipropionic acid, dissolved ammonium chloride and solid ammonium chloride. This mixture is transferred as short as possible to a second larger reaction apparatus. In the second reactor, the reaction is carried out with the desired long-chain alcohol in the presence of thioglycolic acid as a catalyst. The reaction temperature is 70-12O ⁰ C. Escaping vapors are condensed in an associated condenser and returned to the reactor. After completion of the reaction, the ester is separated from the mother liquor and washed several times.

Exemplary embodiments

1. 427 kg of thiodipropionitrile are introduced into the stirring machine 1 via line 2 and 8.3 kg of tin (II) chloride are added as catalyst. Within 25 to 40 minutes, 753 kg of 37% strength hydrochloric acid are added via line 3 at a nominal temperature of 32 ° C.

If the setpoint temperature deviates by ± Γ, HCI dosing is interrupted in order to prevent unwanted accumulation of HCI or formation of undesired by-products.

The removal of the heat of reaction is carried out by indirect cooling with K Ohlwasser. A shortfall of the setpoint temperature must be avoided. Via line 6 escaping vapors with a total of 0.54 kg of HCl are condensed in the condenser 7, the condensed liquid passes back via line 6 in the agitator 1.

Subsequently, steam is heated to 70 ° C. and stirred for 1 hour at this temperature. The reaction mixture now passes via line 8 into the mixing machine 9.

This line is laid without sharp bends and with a steep gradient to prevent the formation of solid ammonium chloride. The stirring machine 9 is steam-heated, but can also be cooled if necessary to maintain the optimum temperature regime. After 10 9kg of thioglycolic acid was added as catalyst via line 10, 1615kg of octadercyl alcohol are introduced via line 11. It is then heated to 110 ⁰ C and esterified for 2 hours at this temperature. Resulting vapors arrive via line 14 in the condenser 15, the condensate passes back via line 14 in the agitator 9. * Nit 700kg water via line 2. Of 9O ⁰ C dilutes the aqueous phase in order to achieve a better separating effect. After draining the hydrochloric acid ammonium chloride solution via line 13 is washed several times with warm water of 90 ° C and fed the finished crude ester via line 13 for further processing. The yield of crude ester is 97.7%.

The finished ester has an iodine color number of 1.8mg J ₂ / 100ml. The acid number is 8-10 mg KOH / g.

2. If, under otherwise identical conditions as in Example 1, the setpoint temperature is maintained at 20 ° C. during the addition of HCl, the dosing time increases to 90 min and the HCi emission in the vapors to 1.5 kg of HCl. The iodine color number improves despite the more expensive cooling only 1.6mg J ₂ / 100ml.

The yield remains unchanged.

Claims (1)

A process for the preparation of Thiodipropionsäureestern higher alcohols by reacting Thiodipropionsäuredinitril with hydrochloric acid in the presence of stannous chloride and subsequent further reaction of the intermediate formed with the higher alcohol in the presence of thioglycolic acid, characterized in that the reactions in two successive, adapted to the reaction volume Reactants are carried out, wherein in the first reactor, the HCI dosage while maintaining a lying at 20 to 40 ⁰ C, preferably at 30 to 35 ⁰ C reaction temperature, maintained at a tolerance of ± 1 °, takes place, the resulting reaction mixture to 7O ⁰ C is heated and then their reaction with the higher alcohol in the presence of thioglycolic acid at a temperature of 70 to 120 ⁰ C is carried out in the second reactor. For this 1 page drawing Field of application of the invention The invention relates to a process for the technical preparation vr η Thindipropionsäureestern from Thiodipropionsäuredinitril, hydrochloric acid and long-chain alcohols in the presence of catalysts. The thiodipropionic acid esters prepared thereafter can be used as antioxidants for the stabilization of polyolefins due to their quality. Characteristic of the known technical solutions The reaction of nitriles with alcohol, in the presence of mineral acids, especially hydrochloric acid, has long been known and has been described several times (Houben-Weyl, Vol. VII, p. 536 ff.). Thus, acrylic acid esters of acrylonitrile are produced industrially by this process. This reaction can also be carried out with thiodipropionitrile. Thus, DE-OS 1935759 describes that Thiodipropionsäuredinitril in an inert organic solvent with, based on da t Dinitril, 3.5 to 5.5 times the molar amount of hydrogen chloride and the approximately molar amount of higher-chain alcohol at reaction temperatures below 5O ⁰ C. can be reacted, wherein the reaction product is decomposed with boiling water or steam. Although this method gives quality Thiodipropionsäureester, but has due to the long reaction times at low reaction temperature and the use of a solvent one poor space-time yield. Added to this is the additional expense of separating a solvent. The DD-PS 150054, however, describes a process which works without solvent and at higher ar esterification temperature, but uses catalysts. The reaction is carried out in the presence of tin or its salts and an organic acid having a dissociation constant k | ⁵ > 8 · 10 ~ ⁶ , whereupon preferably tin (II) chloride is used as the tin compound and thioglycolic acid as the organic acid. The embodiments set forth there obviously prefer the one-pot process, which in principle has the advantage of low equipment costs, on the other hand are known in one-pot process an exact process control, especially the temperature control, limits set, whereby both product quality and the HCI emission are adversely affected. A negligible control of the HCI dosage over the reaction temperature is not possible because it can cause unwanted HCI accumulations, which lead to a subsequent warming to a run of the reaction. Object of the invention The aim of the invention is to eliminate the disadvantages which result from a not always exact process control in the one-pot process. remedy. Explanation of the essence of the invention The invention is based on the object of developing an ancestor for the production of thiodipropionic esters by changing technological parameters, which corresponds to the aforementioned objective. According to the invention, thiodipropionic acid esters of thiodipropionodinitrile, hydrochloric acid and higher alcohols in the presence of stannous chloride and thioglycolic acid are obtained in good product quality with low HCl emission, if the reaction of the thiodipropionodinitrile to the thiodipropionic acid ester is carried out in two reaction apparatuses connected in series and adapted to the reaction volume. he follows. In the first stage, the reaction of the thiodipropionodinitrile with hydrochloric acid takes place in the presence of tin (II) chloride as the catalyst. The reaction temperature is maintained at a set point between 20 and 40 ° C, preferably between 30 and 35 ° C. Since it is an exothermic reaction, must be cooled. The dosage of hydrochloric acid is adjusted so that it corresponds to the measured reaction rate at the selected target temperature. The preferably selected setpoint temperature between 30 and 35 ⁰ C allows the use of a simple cooling system. A condenser associated with the reactor ensures that the still escaping minimum vapor volume is returned and there is always a defined HCl concentration. It is important that the hydrogen chloride reacts at the same rate as it is supplied.