Patent GB-184955-A (GB)
Title: Improvements in the tanning of hides and skins
IPC: C14C3/28
Filed: 1921-06-30
Abstract: 184,955. Margotton, P. J. C. June 30, 1921. Treating hides and skins with liquids and vapours; rotary-drum machines; combination tanning processes; oil-tanning.-Unhaired hides are tanned, especially for the production of gloveleather, by treating in a fulling-apparatus with chromic acid, sulphuric acid, and water, then draining, treating first with acid reducing-gases or vapours and then with alkaline gases or vapours, washing, subjecting to a chamoising treatment, degreasing, wringing, and finally drying. The amount of chromic and sulphuric acids in the mixture is proportional to the weight of the hide, but the amount of water is constant. The hides are treated with the acid mixture in a polygonal drum 1, Fig. 2, rotatable on its axis x, y and provided with an oblique grating 2 and a partition 3. An aerating-tube 4 enters the compartment formed by the partition 3, and water. tight doors 5 are provided on each side of the grating 2. The drum is rotated, and the larger and smaller surfaces of the compartments formed by the grating 2 are alternately brought to the bottom, so that the space occupied by, and, consequently, the pressure on, the hides is varied, thus producing a fulling action. When thoroughly penetrated, the hides are removed and drained and nailed to frames a, a<1> which are carried by a conveyer 11 to a chamber 10, Fig. 1. The frames are transferred to ledges 12 in the chamber 10, which is then rendered gastight. Cocks between a reservoir S of sulphur dioxide and the chamber are opened and the chamber is filled with gas. When the chamber is full, the cocks are closed and the fan v started to agitate the gas and surround the hides therewith. The hides are left until the chromic acid is reduced, which is ascertained by means of a check chamber T provided with glass panes and adapted to be isolated by cocks t<1>, t<2>. When reduction is complete, air is forced through from the fan X to drive the sulphur dioxide into a recovery chamber G, where it is brought into contact with a fine spray of water charged with lime. When the chamber 10 is thoroughly aerated, the cocks are closed, and the chamber H, through which the air passes from the fan X, is heated, and air is then passed from the heater through a vessel A, containing a solution of ammonia, into the chamber 10, excess ammonia being absorbed by water in a vessel M. When completely neutralized, the hides are removed from the chamber, washed in a prismatic fulling-vat, wrung, and then replaced in the chamber 10. Heated air is then passed through a vessel K containing alcohol into the chamber, the alcohol being absorbed by the water in the skins and the excess recovered in a condenser L. A radiator Y is provided in the chamber 10 to prevent condensation of the alcohol. When saturated, the hides are removed and treated with oil, which is absorbed by the alcohol. When penetrated by the oil, the vat, which comprises a rectangular basin, is tilted to throw the hides on to a draining-board. They are then wrung to remove the excess oil, replaced in the chamber 10 which is rendered gastight and heated to evaporate the alcohol and water. The oil which remains is oxidized by the chromium sulphate and effects a chamoising of the leather. The hides are then removed, transferred to an oil press, degreased scraped, wrung, and finally nailed to a drying-floor.