Liquid compositions used as insulating and heat transfer means, electrical devices containing said compositions and preparation method for such compositions

1. A liquid composition that may be used as a dielectric composition, said composition comprising a mixture of at least one natural triglyceride and at least one fatty acid ester different from triglycerides, said fatty acids of the fatty acid ester being derived from at least one vegetable oil, plant, wood treatment derivate, algae, microalgae, animal fat, or sugar, wherein:

(i) the fatty acids present in the at least one natural triglyceride and in the at least one fatty acid ester different from triglycerides comprise, by weight with respect to the total weight of fatty acids in the esters:

at least 70%, and preferably over 85%, of at least one monounsaturated fatty acid,

0 to less than 10% of at least one polyunsaturated fatty acid,

less than 20% and preferably less than 10% of at least one fatty acid having a hydrocarbon chain containing a number of carbon atoms different from 18, and wherein

(ii) the at least one natural triglyceride present in the mixture corresponds to 10to 90% by weight, preferably to 40and 75% by weight compared to the total weight of the mixture;

wherein the at least one fatty acid ester different from triglycerides is a fatty acid ester of an alcohol selected from ethane 1,2diol; propane 1,2 diol; propane 1,3 diol; methyl-2 propane 1,3 diol; dimethyl 2,2 propane 1,3 diol; ethyl 2 propane 1,3 diol; diethyl 2,2 propane 1,3 diol; 2 butyl 2 ethyl propane 1,3 diol; butane 1,4 diol; pentane 1,5 diol; methyl 4 butane 1,4 diol; pentane 2,3 diol; hexane 1,6 diol; octane 1,8 diol; decane 1,10 diol; dodecane 1,12 diol; octadecane 1,12 diol; phtalyl alcohol; isophtalyl alcohol; terepthalyl alcohol; diglycerol (linear and cyclic); dihydroxyacetone; 1,4 cyclohexane dimethanol; bisphenol-A; isosorbide; 2,5 bis (hydroxymethyl) tetrahydrofurane; 2,5 bis (hydroxymethyl) furane; 1,8 terpine; or 1,8 terpineol.

2. The composition of claim 1 , wherein the at least one fatty acid ester different from triglycerides is derived from at least one natural triglyceride by converting the natural triglyceride with an alcohol into the at least one fatty acid ester, wherein said alcohol is different from glycerol.

3. The composition according to claim 1 , wherein the at least one fatty acid ester different from triglycerides is essentially a mono-fatty acid ester.

4. The composition according to any one of claims 1 to 3 , wherein the fatty acids present in the at least one natural triglyceride and in the at least one fatty acid ester different from triglycerides comprise, by weight with respect to the total weight of fatty acids in the esters, 0.01to less than 10% of at least one polyunsaturated fatty acid.

5. The composition according to any one of claims 1 to 3 having a pour point lower than −10° C. and a fire point higher than 180° C.

6. The composition of any one of claims 1 to 3 , wherein the vegetable oil is a UHO canola oil, or HO sunflower oil, or HO soybean oil or palm oil fraction having a content of mono-unsaturated fatty acids having 12to 24carbon atoms in the molecule of greater than or equal to 70%, preferably greater than or equal to 75% by weight.