CS225517B1 - Cleaning of the 2-hydroxyethoxyethylester of metacrylic acid - Google Patents

Description

The invention 3e relates to a process for purifying methacrylic acid 2-hydroxyethoxyethyl ester of the formula I / i / t

0¾ O · O000¾ 0¾ 00¾ 0¾ OH, for the sake of brevity called diglykolmetha Jeryl *, the basic monomer that is polymerized into hydrophilic polymers used in medical protetioids, for example, to produce contact lenses, body tissue replacements and, more recently, to prepare pharmaceutical forms that allow controlled release of active substances ·

On an industrial scale, the diglycol methacrylate of formula 1 is prepared by re-esterification of alkyl esters, in particular methyl or ethyl methacrylic acid 2- (2-hydroxyethoxy) ethanolam, further for brevity of diethylene glycol ^and catalytic action of alkali metal alcoholates, especially sodium methylate or quaternary ammonium however, this advantage is undermined by the formation of other undesirable reacoe products, in particular the product resulting from the double re-esterification of diethylene glycol with methacrylic acid esters of 1,5-bie- (methacryloyloxy) -3-oxapentane of formula II (so-called diester). ³ / IV.

0¾ = 0 © 00000 ^ 0¾ 00¾ 0¾ ooc · 0 0¾

- 2 *

225 517

As verified by practical testing, the diester of formula II is formed in relatively high amounts of 3 to 5% by weight and cannot be effectively separated by fractional distillation. Repeated redistillation resulting in a diglycol methacrylate of formula I containing diester of formula II 2% by weight · not suitable because longer thermal exposure causes polymerization even when depolymerisation catalysts and / or · polymerization inhibitors have been added · Diglycol methacrylate and so high undesired diester content is completely unsuitable for medical orthotics use · For the production of contact lenses diglycol methacrylate is not suitable even if it contains 1% by weight of diester. Sake for acute purposes, for example for the manufacture of polymers regulating the release of active substances from pharmaceutical forms, such a contaminated substance is not usable as it reduces the concentration of the monomer mixture for the solution radical polymer ·

These drawbacks are overcome by a simple but highly effective method of purifying 2-hydroxyethoxyethyl methacrylic acid ester prepared by reesterification of methyl or ethyl methacrylic acid diethylene glycol under the catalytic action of alkali metal alcoholates, in particular sodium methylate or quaternary ammonium bases, after dilution with water and separation unreacted starting methacrylic ester, wherein the reaction mixture so treated is first extracted at least twice in a ratio of 10 parts of the mixture to 1 to 2 parts of an organic, water-immiscible alkane type solvent having a boiling point of 40 to 120 ° 0, for example petroleum ether; the aqueous phase is saturated with sodium chloride and repeatedly extracted with diethyl ether in a ratio of 10 parts of the mixture to 1 to 2 parts of the solvent ·

In carrying out the process according to the invention, the undesired methacrylic acid ester ester is converted from the unreacted starting methacrylic ester into the petroleum ether extracts almost quantitatively, while the desired diglycol methacrylate of formula 1 remains in the aqueous phase, from which it is obtained by a known method.

225 517 by extraction with ether after salting out with sodium chloride * If the preparation of highly pure substances is desired, it is advisable to repeat this process several times. · Vaccine is purified by distillation under reduced pressure *

The process according to the invention has been verified both laboratory and operational and has consistently yielded high purity products having a dieater content of formula 11 ranging from 0.1 to 0.3 wt%. For the above purposes, this degree of purity is conditional. chromatographic columns and the like, the product purified by the process of the invention without distillation could only be completely used after filtration and activated carbon.

Further details of the method according to the invention are given in the following examples which illustrate the method without limiting it in any way.

Example 1 ^:

Raw materials (in kg) methacrylic acid methyl ester / 1 mol / 10,000 diethylene glycol / 1.27 mol / 12,700 phenothiazine 0.005 petroleum ether 13.000 sodium chloride 8.000 ethyl ether 22.000 cupric chloride 0.012 tetramethylammonium hydroxide / 0.01 mol / 0.450

Drawbar methanolic solution

Procedure ^

After an 80 liter glass kettle, diethylene glycol, methacrylic acid methyl ester, quaternary base and phenothiazine are placed and the reaction mixture slowly warms to an internal temperature of 50 ° C with stirring. After clarifying the solution, the temperature is raised to 60-65 ° C and maintained for 1-2 h. It is then cooled to 20 DEG C., diluted with 10 liters of water and allowed to stand for 2 hours. The upper layer containing unreacted methacrylic acid acid ester is separated and put aside for possible regeneraol. The aqueous layer is diluted with an additional 30 liters of water and extracted thoroughly with at least 3 times petroleum ether * Then saturated with sodium chloride and extracted with ethyl ether, again at least 3 times the ether extracts are added cuprous chloride and the ether is distilled off. The crude diglycol methacrylate residue is purified by distillation under reduced pressure; t * v »70 to 80 ° 0/67 to 70 Pa.

Yield 8 kg of diglycol methacrylate with diestex content of formula II up to 3% by weight.

Example 2

The procedure was the same as in Example 1, but an adequate amount of ethyl methacrylate was used.

Yield 7.8 kg of diglycol methacrylate containing diester of formula II up to 3 wt. 72 to 81 ° C / 69 to 72 Pa ·

Example 3

The feedstocks, reaction, product work-up and yield are the same as in Example 1, but sodium methylate, prepared by dissolving 0.025 g of sodium metal in 250 ml of methanol, was used as the re-esterification catalyst.

Claims (1)

SUBJECT VISION 11 OF D 225 517 Process for purification of 2-hydroxyethoxyethyl methacrylic acid ester prepared by reoaterification of methyl or ethyl methacrylic acid ester with diethylene glycol under the catalytic action of alkali metal alcoholates, in particular sodium methylate or quaternary ammonium bases, after diluting the reaction mixture with water and separating the unreacted ester in that the reaction mixture thus treated is first extracted at least twice in a ratio of 10 parts of the mixture to 1 to 2 parts of an organic, water-insoluble alkane-type solvent having a boiling point of 40 to 120 ° 0, for example pstrolether; repeatedly extracted with diethyl ether, in a ratio of 10 parts of the mixture to 1 to 2 parts of the solvent ·