Process for the preparation of educt-free diethylene glycol dimethyl ether by methylation of diethylene glycol monomethyl ether

摘要

In the novel process, diethylene glycol monomethyl ether is methylated with methyl chloride in the presence of alkali metal hydroxide. The methylation is carried out at a temperature of 40 to 80 DEG C without solvent, the methyl chloride and the alkali metal hydroxide being employed in each case in an at least stoichiometric amount. To obtain the desired diethylene glycol dimethyl ether, the entire reaction product is subjected to incipient distillation, and as soon as the distillation is about to stop due to poor heat transfer, the remaining amounts of dimethyl diglycol are distilled off together with the water present in the sodium hydroxide solution using the heat present in the salt which has been produced, whereupon this crude distillate is subjected to purification by fractionation in a second distillation step. The second distillation step can be carried out with an even better result in the presence of boric acid.