PURPOSE: In preparing a xylene resin using sulfuric acid as a catalyst, to use a sulfuric acid-containing waste liquor repeatedly without discharging it, and to carry out the treatment of waste liquid easily, by effecting the reaction while only water in the reaction system being eliminated, and keeping the concentration and the amount of sulfuric acid in the waste liquor constant.
CONSTITUTION: For example, 110pts.wt. of 37wt% formalin and 60 pts.wt. waste liquor corresponding to 45wt% sulfuric acid are added to 100pts.wt. xylol, and the reaction is carried out at reflux temperature for 8hr. At the beginning of the reaction, the concentration of sulfuric acid is maintained in 45wt% and in order to keep the amount of sulfuric acid, the reaction is carried out in such a way that only water is removed by adjusting the degree of reduced pressure, and 70pts.wt. waste liquior containing no acid is eliminated. 60pts.wt. Waste liquor corresponding to 45wt% sulfuric acid is separated to give a precondensate of xylene. The sulfuric acid-containing waste liquor is repeatedly used in the following reaction.
TAKEOKA SHIYUUICHI
SAMEJIMA TERUO
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