CS216586B1 - a method for preparing technical methylethylketoxime - Google Patents

Abstract

The method of preparation of technical methyl ethyl ketoxime consists in adding an aqueous solution of hydroxylamine sulfate or hydrochloride and methyl ethyl ketone to a solution of sodium hydroxide in ethanol. The mixture is heated to boiling point and refluxed for as long as unreacted ketone is present in the reaction mixture. Then the ethanol is distilled off and the upper layer of the product is separated after cooling.

Description

The invention relates to a process for the preparation of technical methyl ethyl ketoxime obtained by the reaction of methyl ethyl ketone and sulphate, not hydroxylamine hydrochloride.

Technical Methyl ethyl ketoxime is used as an antioxidant intended to prevent skin formation during storage of airborne paints that dry by oxolyolimeric meohanism.

These are mainly alkyd and oil paints. The effect of MecUaniemus is that during the storage of the paint it adds to the complex the added catalysts to accelerate the drying of dyes, such as cobalt salt, and conversely, when painting from the paint layer can easily flow out and thus release the bound catalyst in the complex. then it can perform its function.

Several methods are known for the preparation of this compound. More commonly, the non-catalysed preparation of oximes, i.e., the reaction of methyl ethyl ketone from a solution of free hydroxylamine without addition of acid or base, is more common. The base ee is most often released from hydroxylamine hydrochloride by the addition of an equivalent amount of alkali metal hydroxide or alcoholate, optionally suspended sodium or potassium carbonate directly in a mixture of methyl ethyl ketone and hydroxylamine salt. Sodium tannate solution was also used to liberate the free base. The laboratory scale also uses a very energetic oximating agent, which is a solution of hydroxylamine hydrochloride in pyridine.

For the catalyzed reacoe, the hydroxylamine salt in alcohol, water or acetic acid alone was used, sometimes with the addition of a mineral acid.

In an acidic environment, the reaction is also carried out using a solution of sodium hydroxylamine disulfonate formed by the reaction of sodium nitrite with sulfur dioxide.

Due to the relatively good reactivity of the methyl ethyl ketoxime, the course of these reactions is relatively good, the only problems being with the homogenization of the reaction mixture during the reaction. Certain technical difficulties arise during product isolation. The methyl ethyl ketoxime is either converted into a suitable solvent from which it is isolated by subsequent fractional distillation or a direct, preferably vacuum, rectification of the oily reaction mixture is carried out. Due to the higher boiling point of methyl ethyl ketoxime compared to the other reactants (alcohol, water), the product is distilled off last, leaving the solution precipitated in the inorganic salt formed, usually an alkali metal dioride or sulphate, to significantly reduce distillation and must be distilled before distillation. largely removed, for example by filtration on a vacuum suction.

It has now been found that the new technology according to the invention makes it possible to prepare methyl ethyl ketoxime much more easily, eliminating the problems of product isolation and obtaining the substance without further purification by distillation suits its use in the manufacture of paints and coatings. The essence of the new technology is that ee to the present 2 to 25 wt. % sodium hydroxide solution in 70 to 100 wt. ethanol at a temperature of 0 to 30 ° C is added successively an aqueous solution of the hydroxylamine salt and methyl ethyl ketone in an amount of 80 to 100% equivalents of the hydroxylamine salt.

The mixture is heated to boiling and then refluxed for the presence of free unreacted ketone in the reaction mixture, which takes about 2 hours. After the reaction has ended, ethanol is distilled off from the reaction mixture and, after cooling to 10 to 40 ° C, the upper product layer formed is separated from the lower waste water layer in a conventional manner.

The present solution of sodium hydroxide in ethanol is usually prepared by mixing an operational and 30% aqueous sodium hydroxide solution with ethanol under cooling. The dissolution of Scaly Hydroxide Scale in dilute ethanol is more laborious and slower. The ethanol used in the production of the first batch is then replaced by the already distilled ethanol obtained during the manufacturing process from the reaction mixture. This distillate also contains small amounts of water, methyl ethyl ketone and methyl ethyl ketoxime. Since ethanol is not consumed in the process of recovery, it is sufficient to replace the slight losses caused by its production losses. In a separate manufacturing process, its presence in the reaction mixture ensures the course of the reaction in a homogeneous phase *

So much faster and without much mixing. The concentration of sodium hydroxide in ethanol is chosen optimally around 10% by weight, in practice it is suitable to use, for example, the addition of 25% by volume, aqueous solution of hydroxide

Stab with a concentration of c, (NaOH) of 10 mol / l.

The hydroxylamine salt is added to the ethanolic liquor, typically in the form of a saturated aqueous solution, although it is also possible to dispense a slurry of undissolved salt in the saturated solution. The total amount of water in the reaction mixture may be selected such that upon removal of ethanol upon completion of the oxime treatment, an almost saturated solution of the resulting inorganic salt, i.e., sulfate or sodium chloride, is formed, which then forms the bottom drop layer in the reaction vessel. If the amount of water in the reaction mixture is too large, dissolution losses occur in the waste water, on the other hand, at a low total water content, crystals of these salts precipitate out of solution, which can cause technical difficulties in separating the two liquid layers.

The example below illustrates an embodiment of the invention.

Exemplary embodiment

200 parts by volume of 10 mol / l sodium hydroxide solution (c) (NaOH) are stirred in 800 parts by volume of ethanol under cooling. A solution of 140 parts by weight of the mixture is added to the mixture at 20 ° C. hydroxylamine hydrochloride in 500 parts by weight of water and immediately added 170 parts by volume of methyl ethyl ketone and the mixture is heated to boiling point over 1 hour. At this temperature, the mixture is refluxed for a further 2 hours and then 830 parts by volume of a distillate containing mainly ethanol is distilled off from the mixture. The distillate is used in another operation instead of the ethanol used. After distillation, the reaction mixture is cooled to 20 [deg.] C., transferred to a separator, the lower layer containing the sodium chloride solution is drained, and the yellowish upper layer consists of practically pure methyl ethyl ketone. The product yield is about 170 parts by weight, i.e. about 98% of theory.

Claims (1)

A process for the preparation of technical methyl ethyl ketoxime from methyl ethyl ketone and a hydroxylamine salt, characterized in that up to 2 to 25 wt. % sodium hydroxide solution in 70 to 100 wt. ethanol at 0 to 30 ° C are added successively an aqueous solution of hydroxylamine sulfate or hydrochloride and methyl ethyl ketone in an amount of 80-100% equivalents of the hydroxylamine salt, heated to reflux and refluxing for the presence of unreacted ketone in the reaction mixture. after cooling to 10 to 40 ° C, the upper product layer is separated.