blue in the present invention the mole ratio of the alkyl ester of the unsaturated carboxylic acid to the alcohol is 1 0 to 10 1 preferably 1 1 to 5 0 1 needless to say any other ratio may be used but there is no advantage in doing so from the viewpoint of economy all of the catalyst may be used from the first or the catalyst may be added in increments over regular intervals or it may be continuously added to the reaction mixture however during normal operations all of the catalyst is preferably present from the start of the reaction the amount of catalyst used can vary considerably however it is generally used in amounts of 0 0001 to 1 0 mole per mole of the starting material alcohol preferably 0 0002 to 0 5 mole in case of zirconium catalyst and 0 0002 to 0 05 mole in case of calcium catalyst the temperature usually employed for the ester exchange reaction ranges from 30 u00b0 to 150 u00b0 c preferably 60 u00b0 to 140 u00b0 c the reaction can also be conducted under a reduced pressure having generally described the invention a more complete understanding can be obtained by reference to certain.