Continuous preparation of alkyl esters of (meth) acrylic acid

A process for the continuous preparation of alkyl esters of (meth)acrylic acid by reacting (meth)acrylic acid with alkanols of 4 to 8 carbon atoms in a phase free of solvents, at elevated temperatures and in the presence of a strongly acidic esterification catalyst, comprising feeding the (meth)acrylic acid, the alkanol and the esterification catalyst into a reaction zone in which water is formed during a residence time of the reactants in the reaction zone and being part of a mixture comprising starting alkanol which is separated from the reaction mixture in a first rectification unit rI attached to the reaction zone, separating the distillate obtained into an organic phase containing a starting alkanol and into an aqueous phase containing water, recycling the organic phase to the rectification unit RI, and feeding the reaction mixture containing the desired ester, which is removed from the reaction zone, to a prepurification process comprising:

• 1. in a first prepurification stage, extracting the reaction mixture obtained by washing with water, thereby removing most of said esterification catalyst from the reaction mixture, and
• 2. in a second prepurification stage, neutralizing and extracting the strongly acidic components with an aqueous alkali solution by reactive extraction of the reaction mixture from stage I;
• passing the remaining reaction mixture as reaction mixture I into a further separation zone comprising rectification units and isolating the resulting alkyl ester of (meth)acrylic acid therein, wherein the prepurification comprises a third stage of:
• 3. extracting residual salts and aqueous foreign-phase fractions with water from the organic reaction mixture I remaining after the second prepurification stage, before passing the remaining organic reaction mixture I to the separation zone comprising further rectification units.