RU2259995C1 - Method for preparing $$$-(4-hydroxy-3,5-di-tertiary-butylphenyl)propionic acid esters - Google Patents

Abstract

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to a method for preparing β-(4-hydroxy-3,5-di-tert.-butylphenyl)propionic acid esters that are used in polymeric industry as stabilizing agents. Method is carried out by the re-esterification reaction of β-(4-hydroxy-3,5-di-tert.-butylphenyl)propionic acid methyl ester with polyhydric alcohols at enhanced temperatures (130-190°C) in the inert gas flow in the presence of catalyst comprising the following components, wt.-%: sodium 4-(β-methylcarboxyethyl)-2,6-di-tert.-butylphenolate, 30.0-45.5, and sodium aluminate, 54.5-70.0. Indicated compounds of alkaline metal are used in the amount 0.7-6.0 mole% of the amount of β-hydroxy-3,5-di-tert.-butylphenol)propionic acid methyl ester. Invention provides enhancing yield and improving color index, reducing cost of the process and reducing amount of by-side products formed.

EFFECT: improved preparing method.

2 cl, 1 tbl, 10 ex

Description

The invention relates to organic chemistry, specifically to the production of esters of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid, which are used in the polymer industry as a stabilizer.

A known method of producing esters of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid by transesterification of methyl ester of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid (methylox) polyatomic alcohols at a temperature of 130-190 ° C for 6-12 hours in the presence of dibutyltin dilaurate and dibutyltin oxide catalysts [US Patent No. 4618700 of 10/21/86].

The disadvantages of the known methods is the high cost and high toxicity of the catalyst used.

A known method of producing esters of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid using lithium amide and lithium hydride as catalysts [US Patent No. 4618700 from 10/21/86].

The disadvantage of this method is the use of scarce and explosive fire hazard catalyst, which complicates its use on an industrial scale.

A known method of producing pentaerythryl-tetrakis- [3- (4-hydroxy-3,5-di-tert-butylphenyl) propionate], which consists in the transesterification of methylene pentaerythritol in the presence of dimethylformamide or dimethyl sulfoxide and zinc acetate catalyst as a solvent [Application No. 2002132169 / 04 to the patent of the Russian Federation of December 28, 2002].

The disadvantage of this method is its high cost, due to the use of significant amounts of solvent and the instability of the catalyst, which decomposes at elevated temperatures.

A known method of producing methyl ester of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid by alkylation of 2,6-ditretbutylphenol with methyl acrylate at an elevated temperature using a catalytic complex of the following composition,% wt .:

Sodium 2,6-di-tert-butylphenolate - 1.4-11.0; β- (4-hydroxy-3,5-di-tert-butylphenyl) propionate sodium - 0.4-3.0; 2,6-di-tert-butylphenol - the rest is up to 100

[RF patent No. 2178408, IPC C 07 C 69/732, issued December 20, 2002].

The disadvantages of the above method include the formation of a by-product of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid due to the use of β- (4-hydroxy-3,5-di-tert-butylphenyl in the catalyst ) sodium propionate, which gives a yellow-cream color to the target product and reduces the yield of the target product.

The closest technical solution (prototype) is a method for producing esters of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid in the process of transesterification of methyl ester of β- (4-hydroxy-3,5-di-tert -butylphenyl) propionic acid with polyhydric alcohols at 135-180 ° C in a stream of inert gas in the presence of a catalyst of the following composition,% wt .:

4- (β-methylcarboxyethyl) -2,6-di-tert-butylphenolate sodium - 22.8-12.0; Potassium 2,6-di-tert-butylphenolate - 5.1-1.8; 2,6-di-tert-butylphenol - the rest is up to 100

[A.S. No. 1685920, IPC C 07 C 69/732, 67/02].

These alkali metal compounds are used in an amount of 1.5-10.0 mol% of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid methyl ester.

The disadvantage of this method is the introduction of expensive potassium alkali and a relatively low yield of the target product, which does not exceed 94%.

An object of the invention is to increase the yield and improve the color of the target product, cheaper process and reducing the number of by-products formed.

This problem is solved in that in the method for producing esters of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid by transesterification of methyl ester of β- (4-hydroxy-3,5-di-tert-butylene ) propionic acid with polyhydric alcohols in an inert gas stream and at elevated temperature in the presence of a catalyst containing β- (4-methylcarboxyethyl) -2,6-di-tert-butylphenolate sodium, according to the invention, the catalyst further comprises sodium aluminate in the following ratio,% wt .:

4- (β-methylcarboxyethyl) -2,6-di-tert-butylphenolate sodium - 30.0-45.5; sodium aluminate - 54.5-70.0;

however, these alkali metal compounds are used in an amount of 0.7-6.0 mol% of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid methyl ester, and the transesterification process is carried out at a temperature of 130- 190 ° C. The method is as follows.

Esters of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid are separated from the salts of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid and sodium aluminate, and purified by crystallization.

Then the catalyst is prepared: the calculated amount of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid methyl ester, C ₁ -C ₄ aliphatic alcohol and a predetermined amount of sodium alkali are loaded into the flask. The mixture is stirred at a temperature of 80-120 ° C for 30-40 minutes, then a predetermined amount of hydrated kaolin (Al ₂ O ₃ · nSiO ₂ · mH ₂ O) is introduced into the reaction mixture and stirred for another 20 minutes with distillation of the solvent. The composition of the catalyst is analyzed by potentiometric titration and liquid chromatography.

Next, polyhydric alcohol is introduced into the mixture with constant stirring, the temperature is increased to 130-190 ° C, the synthesis is carried out from 4.5 to 7 hours, after the completion of the synthesis, the reaction mass is cooled to 90-100 ° C, a solvent (heptane) is introduced, cooled to crystals precipitate and recrystallize to obtain β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid ester.

An unexpected effect was the fact that with the introduction of hydrated kaolin during the preparation of the catalytic complex, NaOH interacts with Al ₂ O ₃ , which is part of kaolin, with the formation of sodium aluminate. As shown by experimental studies and kinetic relationships, sodium aluminate contributes to the emergence of a synergistic effect. The water contained in kaolin prevents the further formation of 4- (β-methylcarboxyethyl) -2,6-di-tert-butylphenolate sodium due to hydrolysis, thereby eliminating the possibility of a yellow tint in the target product. In addition, SiO ₂ contained in kaolin adsorbs impurities on its surface that adversely affect the color of the target product.

The starting reagents must meet the following requirements:

- methyl ester of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid - GOST 4348-86; - pentaerythritol - GOST 2168-82; - methanol - GOST 2222-78.

Example 1

116.8 g of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid methyl ester, 50 ml of solvent (C ₁ -C ₄ methyl or other aliphatic alcohol C ₁ -C ₄ ), 2 g of sodium alkali are loaded into the flask. The mixture is stirred at a temperature of 80-120 ° C for 30-40 minutes. Then 1.1 g of kaolin was introduced into the reaction mixture and the mixture was stirred for another 20 minutes with distillation of the solvent. The composition of the catalyst is analyzed by potentiometric titration and liquid chromatography. Then 13.6 g of pentaerythritol are added to the mixture with constant stirring and the temperature is raised to 150 ° C. The synthesis is carried out for 4.5 hours with distillation of methanol released during the reaction. At the end of the synthesis, the reaction mass is slowly cooled to 90-100 ° C and a solvent (heptane) is introduced, cooled until crystals precipitate, and recrystallized. 115.92 g of pentaerythryl-acid-β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid are obtained. Yield 98.9%.

Examples 2-10 are shown in table 1. The syntheses are analogous to example 1.

The table shows that the proposed method will achieve a yield of esters of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid 99.0% compared with the prototype, where the yield reaches 94%, which will ensure widespread use him as stabilizers in the polymer industry.

Claims (2)

1. A method for producing β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid esters by transesterification of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid methyl ester with polyhydric alcohols in a stream of inert gas and at elevated temperature in the presence of a catalyst containing 4- (β-methylcarboxyethyl) -2,6-di-tert-butylphenolate sodium, characterized in that they use a catalyst additionally containing sodium aluminate in the following ratio of components, wt. %: 4- (β-Methylcarboxyethyl) -2,6-di-tert-butylphenolate sodium 30.0-45.5 Sodium Aluminate 54.5-70.0 while these alkali metal compounds are used in an amount of 0.7-6.0 mol% of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid methyl ester. 2. The method according to claim 1, characterized in that the transesterification process is carried out at a temperature of 130-190 ° C.