Reaction products which are suitable as demulsifiers for crude oil emulsions, comprise olefinically unsaturated carboxylic acids and polyetherols and are obtainable byA) condensation of one or more unsaturated C.sub.3 -C.sub.10 -carboxylic acids or their derivatives of the general formula I ##STR1## where R.sup.1 and R.sup.2 are each hydrogen, C.sub.1 -C.sub.4 -alkyl or carboxyl, R.sup.3 is hydrogen or methyl and R.sup.1 together with the carboxyl group may form a 5-membered or 6-membered anhydride ring, with a polyetherol of the general formula II ##STR2## where R.sup.4 is a radical of a monohydric or polyhydric alcohol or of a phenol or of an alkylphenol of 7 to 30 carbon atoms or a radical of an alkylphenol/formaldehyde or alkylphenol/acetaldehyde condensate, R.sup.5 is a branched or straight-chain C.sub.2 -C.sub.4 -alkylene group, where different units [R.sup.5 -O] may be present within a polyalkylene oxide chain, and X is an integer of from 5 to 120, in a molar ratio of compounds II to I of from 2:1 to 10:1 and in a weight ratio of from 25:1 to 1,000:1,B) polymerization of the resulting condensate with one or more unsaturated carboxylic acids I and, if required, further olefinically unsaturated monomers copolymerizable with the carboxylic acids I, the amount of the carboxylic acids I being from 50 to 100 mol %, based on the amount of the olefinically unsaturated monomers, and the molar ratio of the polyetherol II to the sum of the olefinically unsaturated monomers used in process steps A) and B) being from 1:5 to 1:200, and subsequentC) condensation of the resulting reaction mixture, with the proviso that not all hydroxyl groups are converted,and a process for their preparation, mixtures of the reaction products with organic solvents and the use of the reaction products and of the mixtures as demulsifiers for crude oil emulsions.