carboxylic acid derivative and phenolsulfonate can preferably be reacted together in the molar ratio from 0 9 1 to 2 1 preferably 1 1 to 1 5 1 the reaction media used are aliphatic or aromatic hydrocarbons having boiling points between 80 and 220 u00b0 c in particular 100 to 180 u00b0 c e g toluene xylene paraffins having 8 to 22 carbon atoms such as decane undecane dodecane hexadecane or octadecane or mixtures thereof particularly suitable media are aliphatic hydrocarbon mixtures of de aromatized isoparaffins as are commercially available as shellsols available from shell chemical lp houston tex isopar g and isopar 4 available from exxonmobil chemical houston tex the solubility of the sps in this reaction medium is generally less than 1 prior to starting the reaction a polyglycol ether is added as defined by the general formula above in this formula r and r 3 or r 1 and r 4 may by the same or different preferred are those polyglycol ethers wherein the group cr 1 r 2 cr 1 r 2 is c 2 h 4 or c 3 h 5 polyethyleneglycol ethers are preferred which have a boiling point between 130 u00b0 c and 300 u00b0 c especially preferred are diethyleneglycol dimethylether diethyleneglycol diethylether diethyleneglycol ethyl methylether diethyleneglycol dibutylether and dipropyleneglycol dimethylether the polyglycol ether is used in an amount of 0 5 to 25 by weight preferably 1 to.