CS263803B1 - A method of purifying crude bis-allyldiethylene glycol carbonate - Google Patents

Abstract

A process for the purification of bis-allyldiethylene glycol carbonate prepared by reacting allyl alcohol with diethylene glycol bisulfate in the presence of aqueous concentrated alkali hydroxide solutions by diluting the reaction mixture with water and separating the phases to give a crude product containing unreacted diethylene glycol bis-chloroformate in an amount of up to 1% by weight, based on the weight of the crude product, of an organic or inorganic base in an amount of 0.01% by weight. % to 3% by weight of the crude product.

Description

1 2 263803

BACKGROUND OF THE INVENTION The present invention relates to a process for the purification of crude bis-allyldiethylene glycol carbonate, prepared by reacting allyl alcohol with bis-chloroformate diethylene glycol in the presence of aqueous concentrated alkali hydroxides by base removal.

These substances are used as monomers for the production of lightweight substitutes for optical glass, mainly for the manufacture of children's glasses.

A large number of works are disclosed, including the preparation of said monomers, but only in one case are technically feasible details of treating the reaction mixture. In other cases, the work deals only with their own reaction. Although the processes for purifying crude by low-temperature crystallization or washed with acidic or oxidizing agents or by carborafine absorption are mentioned, these methods serve to purify the monomer obtained by carbonylation of a mixture of allyl chloride and diethylene glycol. (Tokuyama Soda Process, Japan.)

In the above-mentioned work, the reaction mixture is quenched with water and the organic phase is subjected to vacuum stripping after separation, i.e. no chemical purification is performed. It is further noted in the literature that by washing with 15% w / w dilute sodium hydroxide solution, the product yield and yield are increased. It has been found by the process of the invention that the hydrolysis rate under these conditions is high and there is a percentage reduction in yield within 15 minutes.

However, after dilution of the reaction mixture with water, the product contains a certain amount of unreacted bis-chloroformate, which is obviously enclosed in crystals of inorganic particles. While it is possible to achieve its complete aging, it is possible to increase the feed rate of the hydride and thereby reduce the yield. However, it is more preferable not to use such extreme conditions and to leave traces of this substance in the dry product; it is usually about hundreds of ppm. However, this amount would be a problem for further use. However, the aqueous phase, after dilution of the reaction mixture, contains a few percent of carbonate and a small amount of sodium hydroxide, but it cannot hydrolyze these trichloroformates, apparently a large excess of chloride ions, and the overall buffer nature of the solution.

Removal of the chloroformate from the reaction mixture is, in addition to the large excess of hydroxide, also possible by adding nitrogenous organic bases to the reaction mixture prior to dilution, but this is unsuitable with respect to the volume pulsation in the reactor and thus the possibility of recontamination.

Therefore, it was sought to remove chloroformate, i.e. to carry out the hydrolysis alone, but without decomposing the product at the same time as sodium hydroxide.

The above disadvantages are eliminated by the process of purifying the crude bisallyldiethylene glycol carboxy prepared by reacting allyl alcohol with diethylene glycol bisulfate in the presence of aqueous concentrated alkali hydroxide solutions by diluting the reaction mixture with water and separating the phases of the invention. crude product containing unreacted diethyleneglycol bischloroformate up to 1 wt. % by weight of the crude product is treated with an organic or inorganic base in an amount of 0.01 wt. % to 30 wt. %, based on the weight of the crude product. The base used is alkali metal and alkaline earth metal carbonates, hydroxides, bicarbonates, ammonia, pyridine, monoalkyl amine to trialkylamine, wherein the alkyl has 1 to 4 C atoms, or a combination thereof, after which the product is separated by phase separation. and stripped with steam.

The invention is based on the knowledge that after removal of the major portion of chloride ions, a weak base such as sodium bicarbonate solution is sufficient for the solution, and under these conditions the bisallyldiethylene glycol carboxylate does not hydrolyze. In this case, however, the decomposition of chloroformate is very slow. However, with the growing basicity of the medium, the desired product is already hydrolyzed. In this case, sodium carbonate alone does not cause hydrolysis to a concentration of up to 5%, and hydrolysis progressively increases in concentrated solutions. Solid sodium carbonate reacts with the chloroformate relatively slowly, and dilution of the reaction mixture occurs with dissolving hydration heat to localize and overheat, thereby causing significant decomposition. Filtration of the solids caused product losses and problems of handling character. Potassium carbonate has been shown to be too basic, not only to hydrolyze the product but also to impart additional impurities in the product. In the case of a high concentration of starting chloroformate, for example one-fifth of a%, it is not advantageous to use the dilute sodium carbonate solution alone because of the disproportionate time of reaction (tens of hours) because the bicarbonate formed buffering the medium so that it does not have sufficient basicity. It is then advantageous to gradually add sodium hydroxide solution to the diluted sodium carbonate solution, so that the bicarbonate anion is neutralized to the carbonate anion and optionally excess hydroxide is buffered with excess carbonate. Under these conditions, there is only minimal degradation of the product. Hydrolysis can also be minimized by the low hydroxyl concentration alone (below 3%), but this is less appropriate. In terms of kinetics. the decomposition of chloroformate is preferably the use of an amine such as alkylamines and pyridines, the most preferred is unsubstituted ammonia in aqueous media. However, it is not a hydrolysis but a nucleophilic substitution of halogen. If for example

Claims (2)

26 33 100 ppm of chloroformate hydrolyzes the remaining concentration by means of a 2.5% sodium carbonate solution for several hours with ammonia solution, decomposition is completed within one minute. In order to illustrate the invention in greater detail, the following examples are given, but the scope is not exhausted or limited. EXAMPLE 1 3.8 kg of stripping organic phase, 65 kg of allyl alcohol and 97.7 kg of diethylene glycol bis-chloroformate are introduced into a 250 l stirred reactor. The mixture is cooled to 5 ° C and approximately 45% sodium hydroxide solution is metered in with stirring as quickly as the heat of reaction can be removed at 5 ° C for 7 to 7 hours. The amount of hydroxide is dependent on the reaction conditions, in particular the hydroxyl content of the reaction mixture and the temperature, is approximately 89.5 kg, when the chloroformate reacts completely. Upon completion of the reaction, the reaction mixture is discharged to a volume of 400 L where it is diluted with a solution of 1.1 kgcitric acid in 111 L of extraction water. After phase separation, a crude product containing 30 ppm of starting chloroformate is obtained. To the crude product is added a solution of 3.5 kg of sodium carbonate in 130 l of distilled water or extraction water, whereupon the mixture is stirred to a negative reaction with the chloroformate by reaction with 4- (4-nitrobenzyl) pyridine. with pRedmET A process for the purification of crude bis-allyldiethyl lenglycol carbonate, prepared by reacting allyl alcohol with diethylene glycol bichloroformate in the presence of aqueous concentrated alkali hydroxide solutions by diluting the reaction mixture with water and separating it by phase characterized by being added to the crude product containing unreacted diethyl bichloroformate % of the glycol in an amount of up to 1% by weight, based on the weight of the crude product, from 0.01% by weight of organic or inorganic base. up to 30 wt.%, after separation of the aqueous phase, leads to water extraction and stripping. The yield was 83.5% of theory. EXAMPLE 2 The same procedure as in Example 1 was followed except that the starting chloroformate content was 984 ppm. A solution of 3.5 kg of sodium carbonate in 130 l of distilled water was added to the crude product with stirring, and a 10% solution of sodium hydroxide in distilled water was added at 20-l intervals in 3-liter portions. At the end of each periodyse, the chloroformate content is monitored and, if the reaction to the chloroformate is positive, an additional dose of hydroxide is allowed. When the reaction is negative (e.g. 5 doses), the aqueous phase is separated and dilution of the reaction mixture can be used. The product is then passed through further purification by water extraction and stripping. The yield was 82.5% of theory. EXAMPLE 3 The procedure is the same as in Example 1. A crude product containing 42 ppm of starting chloroformate was obtained. To the crude product was added 7% of 7% ammonia with stirring. After half an hour of stirring, the reaction is complete, whereupon the purified product is led to water extraction and stripping. Yield 84%. The invention relates to the weight of the crude product. 2. A process for the purification of crude bis-allyldiehylene glycol carbonate according to claim 1, characterized in that the base used is carbonates, hydroxides, alkali metal and alkaline earth metal hydroxides, ammonium nitrate, pyridine, monoalkylamine to trialkyl. an amine wherein the alkyl has 1 to 4 C atoms or a combination thereof, whereupon the product is separated by phase separation with water and stripped with water vapor.