CS233166B1 - Process for making phthalic acid esters - Google Patents

Abstract

The invention solves a method of producing phthalic acid esters with alcohols with six to ten carbon atoms, catalyzed by a titanate catalyst of the TiOg . HgO type, in which the esterification is carried out up to a certain value of the acid number of the esterification mixture and the excess esterification component is removed by vacuum distillation with subsequent stripping with steam and isolation of the ester from the catalyst. Its essence is that when using a catalyst based on TiOg . x HgO, the actual esterification process is carried out only up to an acid number of 1.5 mg KOH/g of the esterification mixture. The aforementioned phthalic acid esters are, as plasticizers, an important component in the production of plastics.

Description

The present invention provides a process for the preparation of phthalic acid esters of six to ten carbon atoms catalysed by a TiOg type titanate catalyst. ^{Η 2θ x} * ⁿ EMZ esterification is carried out in a acid value of the esterification mixture and the excess esterifying component is removed by vacuum distillation, followed by stripping with steam and isolating the ester from the catalyst.

Phthalic acid esters with alcohols of six to ten carbon atoms are, as plasticizers, an important component in the plastics industry. They are low volatile liquid substances which provide the organic polymers with flexibility, ductility and increase their thermoplasticity by reducing the melt viscosity, the glazing temperature and the elastic modulus of the product. Organic titanium compounds, their halogenated derivatives or their hydrolysis products are often used as catalysts in the production of phthalic acid esters. One of the most widespread types of titanate catalyst is Ti (OR) wherein R is either an alkyl or vanadium compound (U.S. Patent No. 3,209,021). The most widely used catalysts of this type are tetra (2-ethylhexyl) titanate and tetra (n-butyl) titanate. The technology of treating the crude ester with these catalysts is based on the perfect removal of catalyst residues by multiple scrubbing to prevent subsequent product clouding and deterioration of its electrical properties. The solution of this process is the subject of DE Patent No. 2,612,365 and its principle is to form an emulsion with an aqueous solution of NaOH after cooling the crude ester below 100 ° C. The elimination of the neutralization and washing operation allows the use of an Al2 / SO4 / 3 + + NaOH-based aluminate catalyst, but at the cost of extending the esterification time and correspondingly increasing energy requirements. More preferred is a process for producing organic esters using a TiOg catalyst. x HgO, in which the esterification is carried out to an acid number of not more than

233 166

0.30 mg of KOH / g of esterification mixture was then vacuum distilled off excess alcohol, the residue of which was still stripped off with steam, and the catalyst was separated from the ester by filtration to be used in the following production cylinders. Despite these improvements, this manufacturing process is also quite lengthy and energy intensive.

A further improvement is the use of the process for preparing phthalic acid esters according to the invention. In essence, when using a TiOg · ^x catalyst, the esterification process itself ^leads to an acid number of only 1.5 mg KOH / g esterification mixture.

Based on knowledge of the mechanism of esterification and effects on the reaction rate in the final phase of esterification, it has been proven in laboratory and operational terms that the conditions for removal of excess esterification component by distillation are such / absolute pressure around 0.01 MPa, temperature above 200 ° C that the completion of the reaction associated with the decrease of the acid number to the desired value, i.e. at least 0.10 mg KOH / g ester, will proceed spontaneously and faster due to more intensive and improved removal of the reaction water. The benefit of the process for the production of phthalic acid esters according to the invention is therefore a shortening of the production cycle, resulting in a reduction in the energy consumption of the ester production and an increase in the capacity of the production equipment.

The following examples illustrate the practice of the present invention and its comparison with the present process.

Example 1

To the esterification flask was charged 943.3 g of 2-ethylhexanol, 370.0 g of phthalic anhydride, 21 g of TiO ₂ -based catalyst suspension. x H ₂ 0 with 1 g carboraffin and 1 g kieselguhr. The esterification with a final temperature of 220 ° C was carried out in 3 hours to an acid number of 0.08 mg KOH / g esterification mixture. After removal of heat input, unreacted 2-ethylhexanol was removed by vacuum distillation at a pressure gradually reduced from 0.1 MPa to 0.02 MPa followed by steam stripping at 180 ° C. The total vacuum distillation and stripping time was 2.5 hours. After drying the ester at

A vacuum of 0.03 MPa and a filter of the catalyst had a finished ester having an acid number of 0.06 mg KOH / g ester. The ester yield was 890.1 g.

Example 2

In the batches of Example 1, the esterification was terminated by shutting off the heat input after 2.5 hours at an acid number of 1.23 mg KOH / g esterification mixture. Removal of excess 2-ethylhexanol by vacuum distillation at a pressure gradually reduced from 0.1 MPa to 0.02 MPa followed by steam stripping was carried out for 2.5 hours. After drying under vacuum at 0.02 MPa and separating the catalyst by filtration, pure di (2-ethylhexyl) phtha was produced in a yield of 890.5 g and having an acid value of 0.08 mg KOH / g ester.

Example 3

The esterification bottom flask were weighed 910.7 g mixture of linear alcohols to C _Q1, 370.0 g of phthalic anhydride, 20.9 g of a suspension catalyst Ti0 _second x H ₂ 0 with 1 g carboraffin and 1 g kieselguhr. The esterification with a final temperature of 220 ° C took place in 3 hours. The acidity of the crude ester was 0.10 mg KOH / g. The unreacted excess alcohol mixture was then vacuum distilled off at a pressure gradually reduced from 0.1 MPa to 0.02 MPa and the residues were removed by steam stripping at 180 ° C for up to 2.5 hours. After drying under vacuum at 0.02 MPa and filtering off the catalyst, the acid number was 0.08 mg KOH / g ester. The yield of the ester was 927.3 g.

Example 4

The esterification presented flask a mixture of linear alcohols 0θ to C _lo, phthalic anhydride and catalyst Ti0 _second x H ₂ 0 of dumps in Example 3, and esterification was conducted for 2.5 hours to 220 DEG C. _The acid number at which 1.38 g of KOH / g, the esterification mixture was weaned heat energy input. Excess alcohols were removed by vacuum distillation at a pressure gradually reduced from 0.1 MPa to 0.02 MPa followed by steam stripping for 2.5 hours, after which the ester was dried under vacuum at 0.02 MPa and separated by filtration from the catalyst. . A total of 927.1 g of ester with an acid value of 0.09 mg KOH / g was obtained.

Claims (1)

SUBJECT OF THE INVENTION 233 166 A process for the preparation of phthalic acid esters of six to ten carbon atoms, catalysed by a TiOg-type titanate catalyst. x H ₂ 0, in which the esterification is carried out to a certain acid value of the esterification mixture and the excess esterification component is removed by vacuum distillation followed by steam vapor ceiling and isolation of the ester from the catalyst, characterized in that 1.5 mg KOH / g esterification mixture.