| 摘要 |
975,355. Terephthalic acid esters. BADISCHE ANILIN- & SODA-FABRIK A.G. March 19, 1963 [March 23, 1962], No. 10743/63. Heading C2C. Neutral esters of terephthalic acid are produced by a process in which a neutral salt of terephthalic acid is converted in aqueous solution into an acid salt and the said salt is reacted with an alkanol, an alkanediol or a 1, 2-epoxide to yield a neutral terephthalic ester and a neutral terephthalate, which may be re-used in the process. The starting material is preferably an alkali or alkaline-earth terephthalate, e.g. disodium or dipotassium terephthalate or calcium terephthalate, but other terephthalates may also be used, e.g. cadmium terephthalate or diammonium terephthalate. The conversion of the initial neutral salt into an acid salt may be effected by treating the neutral salt with an acid of higher acidity than terephthalic acid or with the corresponding anhydride. Specified reagents for this purpose are hydrochloric, sulphuric and phosphoric acids, carbonic acid or carbon dioxide, formic, acetic, benzoic and p-toluenesulphonic acids, phthalic acid or its anhydride, acetic anhydride and succinic anhydride. Specified esterifying agents with which the acid terephthalate may be reacted are methanol, ethanol, propanol, butanol, ethylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexanediol, ethylene oxide and propylene oxide. The esterification may be effected in the presence of a catalyst, e.g. zinc borate, silica gel, aluminium oxide or a cobalt sinter catalyst. In Example 1, an aqueous solution of dipotassium terephthalate is treated with phthalic anhydride to yield a precipitate of potassium hydrogen terephthalate, which is filtered off and then heated to 320‹C. with methanol to yield a precipitate of dimethyl terephthalate and dipotassium terephthalate, which is separated by dissolving the salt in water; the phthalic anhydride used for treating the original solution may be replaced by a mixture of benzenecarboxylic acids obtainable by the oxidation of crude xylene, or the original precipitation may be carried out with carbonic acid, as described in Specification 816,248. Example 2 describes a similar process in which the original precipitation is effected with benzoic acid and the esterification is effected with methanol at 310‹C. in the presence of zinc borates. Example 3 describes the esterification of monopotassium terephthalate with ethylene oxide to yield bis-#-hydroxyethylterephthalate, and in Example 4 a continuous method of effecting this esterification is described. |
