Process for the preparation of complex oligomeric structures

Abstract

The invention relates to a process to prepare complex oligomeric structures obtained from vegetable oils. The process allows to use a mixture of triglycerides containing dicarboxylic acids produced by the oxidative cleavage of vegetable oils as a starting material, these oils being subjected to a step of heating (condensation) followed by a step of esterification with alcohols at temperatures up to 250 C.

Claims

1. Process comprising the steps of: a) heating for a time of at least 10 minutes a starting mixture of one or more triglycerides containing saturated dicarboxylic acids, obtaining an intermediate mixture comprising said triglycerides in condensed form and one or more free dicarboxylic acids (condensation step); b) esterifying said intermediate mixture with monohydric alcohols, obtaining a reaction product comprising one or more oligomeric structures and one or more diesters of dicarboxylic acids (esterification step); c) separating said diesters of dicarboxylic acids from said reaction product, obtaining a final mixture of triglycerides comprising one or more oligomeric structures (separation step), wherein the said oligomeric structures have the following structure:
R.sub.4[OC(O)R.sub.1C(O)OCH.sub.2CH(OR.sub.2)CH.sub.2].sub.nOR.sub.3 in which R.sub.1 is selected from C.sub.2-C.sub.22 alkylenes, R.sub.2 is selected from one or more of the following groups consisting of C.sub.6-C.sub.24 dicarboxylic acid residues and C.sub.6-C.sub.24 monocarboxylic acid residues, R.sub.3 is selected from one or more of the following groups consisting of H, C.sub.6-C.sub.24 dicarboxylic acid residues and C.sub.6-C.sub.24 monocarboxylic acid residues, R.sub.4 is an alkyl group, n is a whole number equal to or greater than 2, the said C.sub.6-C.sub.24 dicarboxylic acids of R.sub.2 and R.sub.3 being esterified with monoalcohols and the said mixture of triglycerides having a Number Average Molecular Weight (Mn) of between 800 and 10,000 Da.

2. Process according to claim 1 wherein said steps (a)-(c) are performed at temperatures below 250 C.

3. Process according to claim 1 wherein said condensation step (a) occurs at temperatures between 170 C. and 250 C.

4. Process according to claim 1 wherein said esterification step (b) is carried out without added catalyst or in the presence of acid catalysts consisting of one or more phosphorus compounds.

5. Process according to claim 4 wherein the said phosphorus compounds are selected from mineral acids containing phosphorus, their organic derivatives in which the acid is esterified with alcohols or their mixtures.

6. Process according to claim 4 wherein the said phosphorus compounds are selected from phosphoric acid, phosphonic acid, oligo- or polyphosphoric acids, condensation products of phosphoric acid, or their mixtures.

7. Process according to claim 1 wherein said esterification step (b) is carried out in the presence of acid catalysts consisting of one or more phosphorus compounds and at temperatures comprised between 50 and 200 C.

8. Process according to claim 4 wherein said esterification step (b) is carried out without added catalyst and at temperatures comprised between 100 and 250 C.

9. Process according to claim 1 wherein the monohydric alcohols of step b) are selected from aliphatic, linear or branched C.sub.1-C.sub.12 alcohols.

10. Process according to claim 1 wherein the starting mixture of step a) is obtained from oxidative cleavage of vegetable oils.

11. Process according to claim 10 wherein the starting mixture of step a) is obtained from oxidative cleavage of sunflower oil with a high oleic acid content.

12. Process according to claim 1 wherein said final mixture of triglycerides comprises monomeric triglycerides containing one or more C.sub.4-C.sub.24 saturated or unsaturated alkyl residues, linked to the glycerol molecule through ether linkages.

13. Process according to claim 1 wherein said final mixture of triglycerides comprises oligo-glycerols containing one or more C.sub.4-C.sub.24 saturated or unsaturated alkyl residues, linked to the glycerol molecule through ether linkages.

14. Process according to claim 1 wherein said final mixture of triglycerides comprises esters of saturated monocarboxylic acids, which contain one or more keto groups and/or secondary hydroxyl groups, with C.sub.1-C.sub.12 linear or branched monohydric alcohols.

15. Process according to claim 14, wherein said secondary hydroxyl groups are condensed with monocarboxylic acids and/or alkyl groups and/or with dicarboxylic acids esterified with C.sub.1-C.sub.12 linear or branched monohydric alcohols.

16. Process according to claim 1 wherein said separation step (c) is effected by distillation or by evaporation in a falling film evaporator or a thin film evaporator.

17. Process according to claim 2 wherein said condensation step (a) occurs at temperatures between 170 C. and 250 C.

18. Process according to claim 2 wherein said esterification step (b) is carried out without added catalyst or in the presence of acid catalysts consisting of one or more phosphorus compounds.

19. Process according to claim 3 wherein said esterification step (b) is carried out without added catalyst or in the presence of acid catalysts consisting of one or more phosphorus compounds.

20. Process according to claim 18 wherein the said phosphorus compounds are selected from mineral acids containing phosphorus, their organic derivatives in which the acid is esterified with alcohols or their mixtures.

Description

EXAMPLES

(1) Characterisation of the Product

(2) Molecular Masses were determined by Gel Permeation Chromatography (GPC) using an Agilent 1100 liquid chromatograph equipped with three 5 m PL gel columns connected in series having a porosity of 10E4, 10E3 and 500 Angstrom (). Chloroform at a flow rate of 1 mL/min was used as the eluent. The calibration curve was constructed using standard polystyrenes. The temperature of the column was set at 40 C. The samples were dissolved in chloroform (0.15 mg/ml) and filtered through Teflon filters (pore diameter: 0.20 m).

Example 1

(3) The mixture of triglycerides containing dicarboxylic acids obtained during the process of oxidative cleavage of sunflower oil described in patent application WO 2011/080296 after step c) of separating out pelargonic acid was used as the starting mixture. The HPLC-MS analysis of the mixture of triglycerides revealed the presence of 94% (area) of glycerides of formula R.sub.xOCH.sub.2CH(OR).sub.y)CH.sub.2OR.sub.z, according to the invention, wherein at least one of R.sub.x, R.sub.y and/or R.sub.z is azelaic acid. The kinematic viscosity of the triglycerides mixture at 100 C. was 86.8 cSt.

(4) Step (a)-condensation

(5) 1243 g of the mixture of triglycerides containing dicarboxylic acids was placed in a glass reactor heated by means of a heat transfer oil bath and provided with a mechanical stirrer, a tube for inserting a flow of gas, a thermometer and a condenser.

(6) The reaction mixture was heated to 230 C. for 30 minutes under a flow of nitrogen removing the water formed and light monocarboxylic acids present.

(7) Step (b)-esterification

(8) After heating, the reaction mixture was cooled and when it reached an internal temperature of 180 C. the gradual addition of butyl alcohol by means of a peristaltic pump (or drip funnel) was begun.

(9) The esterification reaction was performed by heating the reaction mixture under reflux and removing the water by means of azeotropic distillation. 255 g of butyl alcohol were added.

(10) Step (c)-separation of dibutyl azelate

(11) The excess butyl alcohol and the volatile butyl esters were separated off by evaporation under vacuum (pressure=5 mbar and vapour T between 80 and 250 C.). 1069 g of a mixture of triglycerides containing oligomeric structures was obtained. The weight ratio of the resulting mixture of triglycerides containing oligomeric structures to the evaporated volatile butyl esters fraction was of about 75/25.

(12) The Mn for the mixture of triglycerides containing oligomeric structures prepared by the esterification reaction according to the invention was 1886 Da.

Comparative Example 1

(13) A mixture of triglycerides containing oligomeric structures was prepared according to Example 1 of the patent application WO 2012/085012 by esterification with butyl alcohol.

(14) The HPLC-MS analysis of the mixture of triglycerides after evaporation of the free carboxylic acids in a thin film evaporator (residence time 120 seconds) revealed the presence of 43% (area) of glycerides of formula R.sub.xOCH.sub.2CH(OR)CH.sub.2OR.sub.z, according to the invention, wherein at least one of R.sub.x, R.sub.y and/or R.sub.z is azelaic acid. The kinematic viscosity of the triglycerides mixture at 100 C. was 692 cSt.

(15) After evaporation of the excess butyl alcohol and volatile butyl esters, a triglycerides mixture containing oligomeric structures was obtained with a Mn of about 1900 Da.

(16) The weight ratio of the resulting mixture of triglycerides containing oligomeric structures to the evaporated volatile butyl esters fraction was only of about 50/50. The yield in was notably lower than that obtained with the process of the present invention.