Patent GB-518963-A (GB)
Title: Improvements in the recovery of odourless soap-forming fatty acids
IPC: C07C51/44
Filed: 1938-06-02
Abstract: 518,963. Fatty acids. I.G. FARBENINDUSTRIE AKT.-GES. June 2, 1938, Nos. 16582 and 16585. Convention dates, June 2, 1937, and Dec. 28, 1937. [Classes 32 and 91] Colourless fatty acids suitable for making soap are obtained from the oxidation products of high molecular aliphatic hydrocarbons by separating the unsaponifiable constituents and subjecting the fatty acids to fractional distillation under highly reduced pressure so conducted as to remove as first runnings the fatty acids having an acid value above 330 and then with steam to obtain the soap-forming acids of acid value of about 330-200. The pressure may be 2-25 m.m. ;. preferably it is 2 m.m. and the first runnings are collected to about 130‹C. without steam or 105-110‹C. with steam, and the soapforming fraction up to 260‹C. The distillation may be effected by passing a thin layer of the crude fatty acids through separate distillation vessels for the 2 fractions, different temperatures and pressures being maintained in the vessels ; each fraction may be further fractionated. In an example, lignite paraffin wax is oxidized as described in U.S.A. Specification 2,095,473, and the product saponified by caustic soda solution ; the soap is dissolved in aqueous ethyl alcohol, the undissolved matter withdrawn, and the solution extracted with benzine to remove any unsaponifiables remaining ; the solvents are evaporated off, the soaps decomposed by sulphuric acid, and the crude fatty acids distilled under reduced pressure as described above. The Specification as open to inspection under Sect. 91 comprises fractionally distilling the crude fatty acids to obtain first runnings having acid values greater than 330 and then a fraction of acid value 330-200 ; it includes also : (1) continuing the distillation to obtain a 260-300‹C. fraction, this is freed from unsaponifiables and used in soap-making, preferably after distillation according to the process of the invention. (2) Apparatus (Fig. 1, cancelled) comprising a measuring vessel 1 for the initial material, distillation chambers 2, 3, 4 having steam inlet pipes 5, 6, 7, overflow vessels 8, 9, 10, a column 11 containing filler bodies, e.g., Raschig rings, coolers 12, 13 fitted with water-cooled coils 14, 15, collecting devices 16, 17 and run-off pipes 18, 19 for the condensed fatty acids, a pipe 20 leading to a vacuum pump, and a cooler 21 with outlet pipe 22 for the condensed lower fatty acids. (3) Apparatus (Fig. 2, not shown) comprising a series of 4 distillation chambers connected through intermediate vessels serving to maintain a constant level in each still, and each fitted with a branched steam pipe, and with a cooler connected to a vacuum pump and having collecting plates and outlet pipes for the condensed acids. (.4) Further examples in which :- 1. The crude fatty acid flows through the 4 stills of the second apparatus, the conditions in each being respectively (a) 2 m.m. and 135‹C., 5 m.m. and 170‹C, 5 m,m. and 260‹C., 30 m.m. and 350‹C.; or (b) 5 m.m. throughout and 120, 260, 290, and 320‹C. to yield respectively fatty acids having 5-9, 9-16, 16-20, and more 'than 20 carbon atoms. 2. The crude fatty acid is passed through the apparatus of Fig. 1, the temperature in the stills being respectively 160, 270, and 310‹C. and the pressure 10 m.m. throughout. 3. Crude fatty acids, obtained by oxidizing lignite, paraffin wax with air in presence of potassium permanganate, are distilled in a copper vessel fitted with a long column packed with Raschig rings, the pressure being 12 m.m. and the temperature 144‹C. ; when the fatty acids passing over have an acid value of 330 the acids in the still are deodorized by treatment with steam under such temperature and pressure conditions that no distillation takes place, and are then fractioned up to 250‹C. as described in Example 1 above, or are used direct for making soap. This subject-matter does not appear in the Specification as accepted.