RU2789155C2 - Method for obtaining high-purity tetraisobutyrates and tetrapivalates of pentaerythritol - Google Patents

Abstract

FIELD: organic synthesis.

SUBSTANCE: invention relates to a method for obtaining high-purity esters of pentaerythritol and saturated monocarboxylic acid: pivalic acid, characterized by the fact that the isolation of the target product after synthesis is carried out by crystallization of ether, and the post-purification of the target product from acid residues, products of incomplete substitution of pentaerythritol and other impurities is carried out by recrystallization from an acetonitrile solution to obtain pentaerythritol tetrapivalate from a mixture of tetrapivalate in acetonitrile in a mass ratio of 1 to 15-20, for 10-12 hours at a temperature of -25 to -30°C.

EFFECT: method for obtaining effective isolation and purification of pentaerythritol esters used as plasticizing compositions and fixed phases for gas-liquid chromatography and making it possible to remove, in addition to the products of incomplete substitution of hydroxyl groups, residues of unreacted carboxylic acids.

1 cl, 2 ex

Description

The present invention relates to a process for the preparation of esters of pentaerythritol and saturated monocarboxylic acids (normal and iso) that can be used as high-purity plasticizing compositions, as well as promising stationary phases for gas-liquid chromatography.

In recent decades, despite the change in industry trends, there has been a steady demand and growth in the production of polymeric structural materials, which are based on various thermoplastic polymers [1, 2]. Plasticizing compositions based on esters of organic acids are integral components of such systems. But the available and widespread plasticizers based on phthalates are toxic, belong to the second hazard class, and their use throughout the world has significantly decreased, especially in the EU countries [3-5].

Non-toxic plasticizers based on aliphatic polybasic acids (adipinates, sebacates), having hazard class 4 and showing higher performance characteristics than phthalates, are practically not produced in the Russian Federation due to the lack of a raw material base.

A second field of application of the esters of pentaerythritol and saturated monocarboxylic acids according to the invention is analytical chemistry, in terms of chromatographic analysis. In chromatography, the stationary phase is the “basis” that determines the interaction between the components of the analyzed sample and the carrier material of the chromatographic column, i.e. the substance of the phase used essentially determines the sequence of exit from the column and the ratio of the retention times of the analyzed components and therefore the choice of the stationary phase is the most an important step to obtain the required chromatographic data, especially for high-boiling components.

They are also of interest as promising synthetic lubricants for various purposes. These compounds have excellent thermal and oxidative stability and good lubricating properties. [6, 7], which at the same time have low corrosion activity.

The objective of the invention is to develop a method for obtaining, effectively isolating and purifying pentaerythritol esters, proposed for use as plasticizing compositions and stationary phases for gas-liquid chromatography, and allowing to remove, in addition to the products of incomplete substitution of hydroxyl groups, the remains of unreacted carboxylic acids.

The prototype of the invention can be considered a method for obtaining pentaerythritol tetraisobutyrate [8], carried out as follows: 2 mol of monopentaerythritol and 8 mol of isobutyric acid are loaded into a glass reactor with a stirrer, refrigerator and thermometer in a stream of nitrogen. Xylene is used as an azeotropic solvent - 4% by weight. The mixture is heated to 220°C with stirring. The water formed during the esterification process is evaporated, and after separating 80% of its theoretical amount, the reaction mixture is cooled to 150°C, and 0.1 wt.% titanium (IV) isopropoxide (Tyzor TPT) (catalyst) is added. Next, the mixture is again heated to 220°C and maintained until the desired value of the acid number is reached; after which the reaction mixture is cooled, the solvent and unreacted isobutyric acid are removed by slowly raising the temperature to 180°C. After cooling, the reaction mass is neutralized with a solution of calcium hydroxide, followed by vacuum distillation at 140°C and filtration of the finished product at room temperature. The resulting product is pentaerythritol isobutyrate with a purity of 94%. [8].

The disadvantages of this method are:

- multi-stage, a large number of operations to isolate the finished product and involve an aqueous solution of calcium hydroxide in the washing process, which will undoubtedly entail product losses and an increase in the amount of wastewater;

- the finished product is an insufficiently purified substance (94% wt.), which limits its use as a highly effective plasticizer for polymer compositions;

- the use of a homogeneous catalyst (titanium (IV) isopropoxide) in the synthesis, as a result of which its isolation from the reaction mass is not provided, which in the future may adversely affect the quality of the resulting plasticizer, especially color.

The proposed method makes it possible to carry out the process at the boiling point of isobutyric acid (163°C) in the absence of a catalyst and an azeotrope-forming agent, which makes it possible to reduce the yield of by-products, incl. into resins, thereby increasing the selectivity of the process. Purification of the product by recrystallization makes it possible to obtain products of high purity (at least 99 wt.%), as well as to completely remove the remains of unreacted acid and by-products (mono-, di-, tri-isobutyrates). The separation of acids by filtration from the substrate allows the unreacted acid to be returned to the esterification process.

Synthesis proceeds according to the following reaction equations:

Pentaerythritol tetraisobutyrate:

Pentaerythritol tetrapivalate:

Example 1:

Pentaerythritol tetraisobutyrate

. Выпавшие кристаллы отфильтровывали и сушили при комнатной температуре около 10 часов. Выход очищенного тетраизобутирата пентаэритрита (чистотой >99% масс.) 40,2 г (65,7% от теоритического). С целью повышения выхода, маточный раствор подвергался частичной отгонке растворителя (до 15% масс.) и дальнейшей перекристаллизации (чистота продукта >98%, масс.), с помощью чего, удается повысить выход до готового эфира до 91% от теоретического.A 250 ml three-necked flask equipped with a Dean-Stark tube was charged with 20 g of pentaerythritol and 105 g of isobutyric acid. The resulting reaction mass was heated until complete dissolution of pentaerythritol and kept boiling for 30 hours. Further, the substrate was left to cool for 10-12 hours at room temperature, as a result of which the target pentaerythritol tetraisobutyrate crystallized out of the reaction mass. The contents of the flask were filtered from excess isobutyric acid, dissolved in methanol in a ratio of 1 ÷ 20.5 (mass) and left for 10–12 hours at a temperature of -25 - (-30

. The precipitated crystals were filtered off and dried at room temperature for about 10 hours. Yield of purified pentaerythritol tetraisobutyrate (purity >99 wt %) 40.2 g (65.7% of theory). In order to increase the yield, the mother liquor was subjected to partial distillation of the solvent (up to 15% wt.) and further recrystallization (product purity> 98%, wt.), with the help of which it was possible to increase the yield to the finished ester up to 91% of theoretical.

Example 2:

Pentaerythritol tetrapivalate

Выпавшие кристаллы отфильтровывали и высушивали при комнатной температуре около 10 часов. Выход очищенного тетрапивалата пентаэритрита (чистотой >99% масс.) 51,4 г. (74,06% от теоретического). С целью повышения выхода, маточный раствор подвергался частичной отгонке растворителя (до 15% масс.) и дальнейшей перекристаллизации, в результате чего, удается повысить выход до 94% от теоретического.A 250 ml three-necked flask equipped with a Dinn-Stark tube was charged with 20 g of pentaerythritol and 120 g of pivalic acid. The resulting reaction mass was heated until complete dissolution of pentaerythritol and kept boiling for 35 hours. Further, the substrate was left to cool for 10-12 hours at room temperature, as a result of which the target pentaerythritol tetrapivalate crystallized out of the reaction mass. The contents of the flask were filtered from excess pivalic acid and dissolved in acetonitrile in a ratio of 1 ÷ 20 (wt.), cooled to a temperature of -25 - (-30) ^° C for 10-12 hours.

The precipitated crystals were filtered off and dried at room temperature for about 10 hours. Yield of purified pentaerythritol tetrapivalate (purity >99 wt %) 51.4 g (74.06% of theory). In order to increase the yield, the mother liquor was subjected to partial distillation of the solvent (up to 15% wt.) and further recrystallization, as a result of which it was possible to increase the yield to 94% of the theoretical one.

Identification and quantitative composition of the obtained compounds was carried out by chromatography-mass spectrometry.

The implementation of this idea will allow:

To create a domestic technology for producing a highly efficient environmentally friendly plasticizing component for use in engineering and construction thermoplastic plastics and composites based on them.

To create a domestic technology for obtaining a highly efficient stationary liquid phase for selective gas chromatographic analysis.

To create a domestic technology for obtaining high-purity components of synthetic base oils for gas turbine engines.

Get products that are in demand on the domestic market, comparable in price and quality to domestic and foreign counterparts and with minimal toxicity.

List of cited literature:

1. Kablov E.N. Modern materials - the basis of innovative modernization of Russia // Metals of Eurasia. 2012. №3. pp. 10–15.

2. L. V. Nozdrina, V. I. Korotkova, and E. Ya. Thermoplastic polymers for structural materials. Overview //Technology. Ser. "Constructions from composite materials". 1991. No. 1. pp. 3–10.

3. Barshtein R.S., Plasticizers for polymers / Barshtein R.S., Kirillovich V.I., Nosovsky Yu.E. - M.: Chemistry, 1982. - 200 p.

4. Wypych A. Plasticizers Databook / A. Wypych. – Toronto: ChemTecPublishing, 2013.

5. Mustafizur Rahman, Christopher S. Brazel. The plasticizer market: an assessment of traditional plasticizers and research trends to meet new challenges / MustafizurRahman, Christofer S. Brazel / Progress in polymer science. – 2004. –

V.29. – p. 1223-1248.

6. Gromova V.A., Mamarasulova Z.V. // Izv. SPbGTI (TU). 2013. No. 20(46). S. 64.

7. Kazimova N.S. // HTTM. 2008. No. 3 (547). S. 29.

8. Non-phthalate plasticizer // Patent PERSTORP AB (SE) No. 0002559449. 2015 SE)., SÖRENSEN Kent (SE).

Claims (1)

A method for obtaining high-purity esters of pentaerythritol and a saturated monocarboxylic acid - pivalic acid, characterized in that the target product after synthesis is isolated by crystallization of the ester, and the target product is further purified from acid residues, products of incomplete replacement of pentaerythritol and other impurities by recrystallization from an acetonitrile solution, to obtain tetrapivalate pentaerythritol from a mixture of tetrapivalate in acetonitrile in a mass ratio of 1 to 15-20, for 10-12 hours at a temperature of -25 ... -30 ° C.