| 摘要 |
A process for preparing pure alkyl 1-hydroxy-2-naphthoates of the formula <IMAGE> (1) in which R denotes lower alkyl, by adjusting, with mineral acid, to pH 5.5-6.5 an aqueous solution of monoalkali and/or dialkali metal salts of 1-hydroxy-2-naphthoic acid, then adding a surface-active compound (1) of the formula <IMAGE> (II) in which R, R1, R2 and R3 denote aliphatic radicals of 1-30 carbon atoms which are substituted and which can contain, in the terminal positions, ionic substituents, or hydroaromatic carbocyclic or cycloaliphatic radicals of 4-8 carbon atoms, and in which X(-) represents one equivalent of an inorganic or organic acid, or (2) of the formula <IMAGE> (III) in which R, R1, R2 and X(-) have the abovementioned meanings, the total number of the carbon atoms of R, R1 and R2 being at least 6 and 2 of the aliphatic radicals R, R1 and R2 being able to form, together with the sulfur atom, a heterocyclic ring, or (3) of the formula <IMAGE> (IV) in which R, R1, R2, R3 and X(-) have the meanings given in the definition of the formula (II), the total number of the carbon atoms of R, R1, R2 and R3 being at least 8 and 2 or 3 of the aliphatic radicals R, R1, R2 and R3 being able to form, together with the phosphorus atom, a heterocyclic ring, in an amount of 0.5 to 5% by weight, relative to 1-hydroxy-2-naphthoic acid, separating off the precipitates at 50 DEG C.-100 DEG C., and esterifying the pure monoalkali metal 1-hydroxy-2-naphthoate present in aqueous solution with dialkyl sulfate at pH 5.5-6.5 between 30 DEG C. and 80 DEG C.
|
