| 摘要 |
<p>Bis - (beta - hydroxyethyl) - terephthalate obtained from terephthalic acid made by the nitric acid oxidation of a substituted aromatic compound is purified by treating an aqueous solution thereof with sodium hyposulphite and isolating the bis - (beta - hydroxyethyl) - terephthalate from the solution. The process is preferably carried out at or near pH7, and it is usually necessary to add an alkaline substance to the aqueous soultion of the bis-(beta-hydroxyethyl) - terephthalate, e.g. hydroxides, carbonates, bicarbonates, salts of weak acids and preferably a sparingly soluble carbonate, e.g. calcium carbonate. The amount of sodium hyposulphite required may be determined by using aqueous methylene blue as an external indicator. In examples: bis-(beta-hydroxyethyl)-terephthalate in aqueous solution is treated with sodium hyposulphate after addition of calcium carbonate (1); and after addition of ammonium hydroxide (2); after a similar treatment in (1) the aqueous solution is treated with decolorizing charcoal (3). Specification 623,669 is referred to.</p> |
