Partial esters of a polyglycerol with at least one carboxylic acid and one polyfunctional carboxylic acid, their preparation and use

1. A (poly-)glycerol partial ester having, on average, from 0.75 to 2.25 acid radicals of one or more carboxylic acids having 10 to 24 carbon atoms and having, on average, from 0.005 to 0.5 radicals of a polyfunctional carboxylic acid comprising polyfunctional carboxylic acid ester (poly-)glycerol partial ester with the proviso that, following complete hydrolysis of the (poly-)glycerol partial ester, a (poly-)glycerol is obtained which has a homologue distribution with:

glycerol: 0.01% by weight to 20% by weight,

diglycerols: 0.01% by weight to 60% by weight,

triglycerols: 0.01% by weight to 60% by weight,

tetraglycerols: 0.01% by weight to 30% by weight,

pentaglycerols: 0.01% by weight to 20% by weight, and

oligoglycerols: ad 100% by weight.

2. The (poly-)glycerol partial ester according to claim 1 , wherein the polyfunctional carboxylic acid is citric acid and comprises citric acid ester (poly-)glycerol partial ester of the general formula (I):

where R 1 , R 2 , R 3 and R 4 , independently of one another, are identical or different and are selected from

H or

a radical of the general formula (II)

where m is greater than or equal to 1 and R 5 and R 6 , independently of one another, are identical or different and are selected from

H or

an acyl radical having 10 to 24 carbon atoms,

where the acyl radical is determined by the acyl radical of the carboxylic acid

esterified with the (poly-)glycerol

and on average at least one of the radicals R 5 or R 6 ═H,

with the proviso that on average at least one radical R 1 , R 2 or R 3 is not H.

3. The (poly-)glycerol partial ester according to claim 2 , wherein following complete hydrolysis of the partial ester, the molar ratio of the resulting carboxylic acids derived from R 5 and R 6 to (poly-)glycerol is between 2:3 and 4:1.

4. The (poly-)glycerol partial ester according to claim 1 , wherein said (poly-)glycerol partial ester has a ratio of saponification value to hydroxyl value between 1:1.3 and 1:2.6.

5. The (poly-)glycerol partial ester according claim 1 , wherein the acid value is less than 50.

6. The (poly-)glycerol partial ester according to claim 1 , wherein the (poly-)glycerol partial ester has a melting point greater than 35° C.

7. The (poly-)glycerol partial ester according to claim 2 , wherein the acyl radical determining R 5 and R 6 arises from a mixture of stearic acid and palmitic acid in a weight ratio from 30:70 to 95:5.

8. A process for the preparation of a (poly-)glycerol partial ester comprising:

providing a (poly-)glycerol having a homologue distribution with

glycerol: 0.01 to 20% by weight

diglycerols: 0.01 to 60% by weight

triglycerols: 0.01 to 60% by weight

tetraglycerols: 0.01 to 30% by weight

pentaglycerols: 0.01 to 20% by weight, and

oligoglycerols: ad 100% by weight;

first esterifying some of the (poly-)glycerol with one or more carboxylic acid having 10 to 24 carbon atoms; and

second esterifying with a polyfunctional carboxylic acid, where the molar ratio of the polyfunctional carboxylic acid used in the second esterifying step to (poly-)glycerol used in said providing step is 1:2 to 1:200, to provide a (poly-)glycerol partial ester having, on average, from 0.75 to 2.25 acid radicals of said one or more carboxylic acids having 10 to 24 carbon atoms and having, on average, from 0.005 to 0.5 radicals of said polyfunctional carboxylic acid.

9. The process according to claim 8 , wherein the one or more carboxylic acids to (poly-)glycerol used have a molar ratio of 2:3 to 4:1.

10. The process according to claim 8 , wherein the polyfunctional carboxylic acid is citric acid and the carboxylic acid is a mixture of stearic acid and palmitic acid in a weight ratio from 30:70 to 95:5.

11. An emulsifier comprising the (poly-)glycerol partial ester according to claim 1 .

12. A formulation comprising the (poly-)glycerol partial ester according to claim 1 .

13. The formulation according to claim 12 , wherein the (poly-)glycerol partial ester is present in an amount from 0.01 to 10% by weight.

14. The formulation according to claim 12 , further comprising from 0.01 to 1.0% by weight of at least one organic acid preservative.

15. The formulation according to claim 12 , wherein said formulation has a pH of from 3.5 to 5.5.