Loading patent…
AssigneeBayer Aktiengesellschaft
InventorsEike Gabel, Heinz U. Blank, Horst Behre
Estimating the term…
4-Hydroxydiphenyl (mono-OD) and 4,4'-dihydroxydiphenyl (DOD) are obtained simultaneously from a mixture which contains these two substances, if such a mixture is treated with an aqueous alkali, and the resulting solution and the solid phase formed are separated at a temperature from -28.degree. C. to +40.degree. C. and the solution and the solid phase are acidified separately in order to form the free mono-OD and DOD. Mono-OD and DOD can be present in the starting mixture in the free form or in the form of the alkali metal phenolates. After formation of the alkali metal phenolates, where this is required, the aqueous alkali still contains 1-15 mol of alkali metal hydroxide per mol of the diphenyl compounds. The concentration of alkali metal hydroxide should be 4-25% by weight, relative to the amount of water present. In this process, it is also possible to employ industrial mixtures of the alkali melts of the associated diphenyl-sulphonic acids.
A process for simultaneously separating 4-hydroxydiphenyl and 4,4'-dihydroxydiphenyl from a mixture containing an alkali metal salt thereof which comprises adjusting the water and alkali metal content of said mixtures such that it contains a stoichiometric excess of 1-15 mols of alkali metal hydroxide per mol of the combined amount of 4-hydroxydiphenyl or 4,4'-dihydroxydiphenyl or the corresponding phenolate thereof and the alkali metal hydroxide is present in an amount of 4-25% by weight based upon the weight of the water, whereby to form a solid phase which contains a predominant amount of said 4-hydroxydiphenyl or the corresponding phenolate and a solution phase which contains a predominant amount of said 4,4'-dihydroxydiphenyl or the corresponding phenolate, separating said solution phase and said solid phase at -28.degree. C. to +40.degree. C. and acidifying at least one of said phases.
Dependencies are inferred from the claim text.