| 摘要 |
PROBLEM TO BE SOLVED: To efficiently and simultaneously produce the subject highly pure mixture suitable as a raw material for modified polyesters by recystallizing dimethyl esters obtained by Witten-Hercules method, concentrating the obtained mother liquid, and then applying specific treatments to the residues. SOLUTION: This method for producing the mixture of dimethyl terephthalate (hereinafter DMT) with dimethyl isophthalate (hereinafter DMI) comprises distilling an esterification reaction product obtained from a raw material composition containing para-xylene and meta-xylene by a Witten-Hercules method process, recrystallizing a main fraction consisting mainly of the dimethyl esters in a lower alkyl alcohol, removing the lower alkyl alcohol from the obtained recrystallization mother liquid by a concentration operation to obtain the residues containing DMT and DMI as main components, distilling the residues to obtain a fraction containing DMI in a high concentration, subjecting the obtained fraction to a thermal decomposition treatment using a noble metal catalyst, subjecting the obtained fraction to a thermal decomposition treatment in the presence of a heavy metal catalyst, and finally distilling the product. |
