GB666499A - Separation of diallyl phthalate by distillation - Google Patents

Abstract

Monomeric diallyl phthalate is separated from a mixture containing the same by reduced pressure distillation in a fractionating column comprising the following sections one above the other (1) a stripping section into which steam is introduced and from which higher boiling components are withdrawn; (2) a heating section into an upper part of which a diallyl phthalate mixture preheated to below its decomposition temperature is introduced and from a lower part of which some of the mixture not vaporized is heated and recycled to the heating section; (3) a rectification section; and (4) a condensation section from which lower boiling components are withdrawn, at least part of them cooled, and <PICT:0666499/III/1> part of them recycled to the column. Diallyl phthalate mixture from line 8 and water from line 9 are heated to 150-200 DEG C in a thermostatically controlled heater 5 and fed to a fractionating column operating at 25-100 mm. of Hg. pressure. Purified monomeric diallyl phthate is removed via line 12, part being returned to the column via line 24 and the rest taken to a cooler 6. Part of the product from cooler 6 is recycled to the column via line 26 and part withdrawn via line 20, the amount withdrawn being controlled by a level controller 21 which is adjusted so that a liquid level is maintained on a tray 22. Conduit 13 carries off steam and some diallyl phthalate vapours which are recovered in an entrainment separator 14 and returned to the column via line 27 or withdrawn via line 28. Part of the diallyl phthalate mixture not vaporized is collected by a catch tray in the bottom of the heating section 2 and is recycled to the column via line 25 and the heater 5. Liquid not collected descends into stripping section 1 into which steam, preferably at 10-25 DEG C above the preheated diallyl phthalate mixture, is introduced via line 18 and from which low boiling impurities are withdrawn via line 23. Preferably the distillation and preheating is carried out in the absence of oxygen. The apparatus may also be used to separate diallyl phthalate from lower boiling point impurities in which case the diallyl phthalate is obtained as a bottoms product. The Specification as open to inspection under Sect. 91 states that the invention is applicable to heat-sensitive materials generally, of which the following are exemplified: (1) unsaturated esters of polycarboxylic acids and monohydric or polyhydric alcohols, of which a large number are specified; (2) dicarboxylic acids having corrosion resisting properties (many specified); and (3) waxes obtained by the distillation under reduced pressure of crude oil fractions. In an example, short residue petrolatum is mixed with water, preheated to 200-250 DEG C and distilled in a fractionating column as described above. This subject-matter does not appear in the Specification as accepted.