PROCESS FOR PREPARING POLYGLYCEROL ESTER OF FATTY ACIDS

Abstract

A process is described for the preparation of polyglycerol fatty acid esters from a reaction mixture to which a metallic catalyst is added, as well as to a method for the purification of an intermediate synthesis product which contains excess fatty acid in addition to polyglycerol fatty acid esters. Compared with the prior art, a significantly improved yield and a higher process speed is obtained along with more economic use of raw materials, auxiliary materials, solvents and energy.

Claims

1. A process which comprises a synthesis method, for the preparation of polyglycerol fatty acid esters from a reaction mixture, characterized in that a catalyst is added to the reaction mixture containing fatty acid and polyglycerol which has at least one metallic compound containing at least manganese, zinc, cobalt or titanium.

2. The process as claimed in claim 1, characterized in that the catalyst comprises tetrabutyl titanate.

3. A method for the purification of polyglycerol fatty acid esters from an intermediate product which contains excess fatty acid in addition to polyglycerol fatty acid esters and which can be obtained by using a method which preferably reacts polyglycerol and fatty acid, characterized in that the intermediate product undergoes a refining step with a basic solution until fatty acid salt and a fatty phase are formed and in the fatty phase, an acid value of less than 1.0 mg KOH/g is obtained.

4. The purification method as claimed in claim 3, characterized in that solvent extraction is carried out after the refining step.

5. The purification method as claimed in claim 4, characterized in that the solvent extraction is carried out at 90° C. to 110° C. and at a pressure of less than 30 mbar, preferably at a pressure of less than 20 mbar and at 100° C.

6. The purification method as claimed in claim 3, characterized in that in a separation step, a separation of the fatty acid salts from the polyglycerol fatty acid esters is carried out, preferably by means of centrifuging.

7. The purification method as clammed in claim 3, characterized in that the upstream reaction method comprises a liquefaction step in which polyglycerol and fatty acid are melted to form a two-phase reaction mixture.

8. The purification method as claimed in claim 3, characterized in that the upstream reaction method comprises a drying step in which drying of the reaction mixture is carried out under vacuum.

9. The purification method as claimed in claim 3, characterized in that the upstream reaction method comprises a heating step in which the reaction mixture is heated at a pressure of 400 mbar to 20° C. to 240° C., preferably to 220° C. to 240° C. and particularly preferably to 230° C. to 235° C.

10. The purification method as claimed in claim 3, characterized in that the upstream reaction method comprises a pressure reduction in which the pressure on the reaction mixture is reduced from 400 mbar in steps to less than 50 mbar.

11. The purification method as claimed in claim 3, characterized in that prior to the refining step, the intermediate product has a hydroxyl value of less than 20 mg KOH/g, preferably of less than 10 mg KOH/g and particularly preferably of less than 4 mg KOH/g, and an acid value of less than 15 mg KOH/g, preferably less than 10 mg KOH/g and particularly preferably less than 6 mg KOH/g.

12. The purification method as claimed in claim 3, characterized by the following steps being carried out the given sequence including the reaction method for the intermediate product: i) liquefaction step, ii) drying step, iii) heating step, iv) pressure reduction, v) refining step, vi) solvent extraction, vii) separation step.

13. The process as claimed in claim 1, characterized in that the synthesis method by means of the quantity of fatty acid or fatty acid derivatives employed in the reaction is orientated towards the preparation of polyglycerol fatty acid full esters and comprises the reaction method.

14. The process as claimed in claim 13, characterized in that the purification method follows the synthesis method.

15. The process as claimed in claim 13, characterized by wherein after step ii) and prior to step iii), in a step ii-a), the catalyst is added and the sequence of steps otherwise remains unchanged.

16. The process as claimed in claim 1, characterized in that the synthesis method is orientated towards the preparation of polyglycerol fatty acid partial esters by means of the quantity of fatty acids or fatty acid derivatives employed in the reaction mixture and comprises a liquefaction, a drying step, a heating step and a pressure reduction.

17. The process as claimed in claim 16, characterized by the steps below, carried out in the given sequence: i) the liquefaction step, ii) the drying step, iii) the addition of the catalyst, iv) the heating step, v) the pressure reduction.

18. The process as claimed in claim 16, characterized in that the purification method follows the method for synthesizing the intermediate product.

Description

EXAMPLE 1

PG(3)-C16/C18 Partial Ester

[0031] 2700 g of PG(3), 2390 g of palmitic acid and 5590 g of stearic acid were placed in a reactor and melted at 80° C. After drying under vacuum (<20 mbar), 3.3 g of tetrabutyl titanate was added as the catalyst. The reaction mixture was heated up to 235° C. under a 400 mbar vacuum. The reaction was initiated beyond ˜200° C. After reaching 400 mbar, the reaction pressure was reduced in steps to <50 mbar. Esterification was continued until an acid value of <1.0 mg KOH/g was obtained. The reaction time was 4 to 6 hours. The reaction time, which was shorter compared with the procedure without a catalyst, resulted in a significantly improved colour of the product. The single-phase PG(3)-C16/C18 partial ester obtained in this mariner was then filtered through a 1 μm filter and decanted. The catalyst here was almost completely removed, however the respective metal was still able to be detected in trace quantities.

EXAMPLE 2

PG(2)-C18 Full Ester

[0032] 1580 g of PG(2) and 10700 g of stearic acid were placed in a reactor and melted at 80° C. After drying at less than 20 mbar pressure, 3 g of tetrabutyl titanate was added to the two-phase mixture which was obtained, as the catalyst. Next, the reaction mixture was heated up to 235° C. at a pressure of 400 mbar, whereupon the reaction was initiated at approximately 200° C. Next, the reaction pressure was reduced in steps to less than 50 mbar. Esterification was continued until a hydroxyl value of less than 4 mg KOH/g was obtained. At the same time, the acid value was usually 4 to mg KOH/g, but could reach up to 15 mg KOH/g. The polyglycerol fatty acid full ester-containing intermediate product was then refined at 80° C. to 90° C. with aqueous 10.5% NaOH solution until an acid value of less than 1.0 mg KOH/g was obtained, and so fatty acid salts had been formed. Next, for the purposes of drying, starting from a pressure of 800 mbar, a stepwise reduction in pressure was carried out to less than 20 mbar at 100° C. The soap which was obtained was separated by centrifuging, or alternatively could be filtered off. The yield of single-phase PG full ester was now more than 90%. Prior to decanting, the PG full ester could be filtered off over a 1 μm filter. This almost completely eliminated the catalyst, however the respective metal was still able to be detected in trace quantities.