GB654842A - Improvements in or relating to the production of mixed esters of dicarboxylic acids - Google Patents

Abstract

Mixed alkyl esters of di-carboxylic acids are made by reacting a fully esterified ester of the carboxylic acid with the lower boiling of the desired alcohols for ester formation with the higher boiling alcohol at not above 90 DEG C. in the absence of moisture and in the presence of an esterification catalyst, the lower boiling alcohol liberated being continuously removed. In a modification an ester of an alcohol boiling lower than either of the desired alcohols for esterification may be used as starting material in which case it is first reacted with the lower boiling of the two alcohols to effect partial alcoholysis and then with the higher boiling alcohol until the alcohol of the starting ester is completely replaced by the desired alcohols the lower boiling point alcohols being removed during the course of the reaction in which the above conditions of temperature and absence of moisture apply. Acid or alkaline catalysts may be used the latter being preferred since by their use reaction is more rapid. Alkaline catalysts are particularly effective with secondary alcohols and when the carbon atom adjacent the carboxyl group carries no hydrogen atom, e.g. phthalic acid. They should be avoided when a CO group other than that of the carboxylic acid is present since alcohol condensations result. The following phthalates are specified: methyl, n-octyl, butyl-ethyl-hexanyl, and ethylsec. octyl. Similar esters derived from dibasic acids obtained by the oxidation of benzenes or naphthalenes or more complex hydrocarbons may also be made. Higher boiling alcohols specified are hydration products of C8-C18 olefines, alcohols obtained by the oxo synthesis in particular the mixture of nonyl alcohols (trimethyl-hexanol) obtained from di-isobutylene and the mixture obtained from di- or tri-propylenes and similar alcohols obtained by the action of formaldehyde on the olefines, straight chain alcohols C8-C18 obtained by reduction of naturally occurring fatty acids, or similar alcohols from Fischer-Tropsch "Gotsch," alkoxy-ethanols, e.g. butoxy-ethanol and secondary alcohols obtained by the reduction of oxidation products of hydrocarbons. In examples (1) and (2) sodium in nonyl alcohol is heated to 120 DEG C., dimethyl phthalate added and methanol removed at 70-90 DEG C. and reduced pressure and the reaction mixture is washed and vacuum distilled to yield mainly methyl nonyl and (1) dimethyl and (2) dinonyl phthalates. The latter symmetrical esters may be worked up by normal ester interchange processes to yield further quantities of mixed esters and in an illustration dimethyl phthalate is reacted with dilauryl phthalate at 80 DEG C. in the presence of sodium in methanol to yield methyl lauryl phthalate, it being stated that symmetrical lower esters and higher esters, e.g. divinyl phthalate, obtained as by-products may be worked up in a similar way. The Provisional Specification refers to the use as alcohols of phenyl methyl carbinol and cyclo-hexanols obtained by the hydrogenation of phenols. Specifications 612,311 and 654,841 are referred to.