product iv obtained as the reaction product can be used as starting material without recrystallization it should be noted however that propionic acid ester consistent with the chemical formula iv whatever the procedure by which it has been produced is fit to be used for starting material when step b is carried out making use of the exchange esterification procedure of the invention in view of the invention it is to be recommended that the propionic acid ester iv is produced by an addition reaction between 2 6 dibutylphenol and alkylacrylate iii using alkali catalysts appropriate ones are in that case e g sodium hydroxide potassium hydroxide lithium hydroxide sodium boron hydride lithium aluminium hydride sodium and potassium tertiary butoxide metallic sodium and potassium 0 5 8 alkali catalyst preferably 1 5 calculated on the quantity of 2 6 dibutylphenol are used it is possible in view of the invention that the step a is performed either as a molten state reaction or using a solvent for fluid solvents which are appropriate are then e g dimethylformamide dimethylacetamide or dimethylsulphoxide hexamethylphosphamide acetonitrile propionitrile or sulphonitrile sulpholan dimethylene glycol tetrahydrofurane or tertiary butylalcohol of these particularly tertiary butylalcohol is well suited to be used in the procedure of the invention an appropriate quantity of the solvent is 5 parts by weight or less preferably 0 1 1 parts by weight of the quantity of 2 6 dibutylphenol it is recommendable in view of the invention that the molar proportion of alkylacrylate and 2 6 dibutylphenol in the addition step a is in the range 0 7 1 3 preferably 0 8 1 1 the reaction temperature is 60 u00b0 130 u00b0 c preferably 70 u00b0 100 u00b0 c and the reaction time is 2 12 h preferably 6 8.