US1977226A - Method of tanning hides and skins - Google Patents

Description

Patented Oct. 16, 1934 METHOD OF TANNING-RIDES AND SKINS Kenneth E. Bell, Marblehead, and Milton 0. McDonald, Salem, Mass., assigiiors to A. C. Lawrence Leather Company, Boston, Mass, a

corporation of Maine No Drawing. Application March 29, 1933, Serial No. 663,374

8 Claims. (01. 149-5) The present invention relates to the method of tanning hides and skins.

In the usual method of tanning with compounds of chromium or chrome tanning as it is usually called, the hides or skins are previously treated for the removal of hair and prepared for the tanning operation by pickling in an acid and salt solution.

The actual tanning is usually done by drume W ming the pickled skins in a solution of basic chromium sulfate until the skin is thoroughly impregnated. After this, the addition of sodium bicarbonate solution serves to neutralize the acid present in the skins and allowsthe basic M chromium compound thus present to react with the hide fibres, to tan them.

In such a process the hide decreases in area and fat wrinkles tend to become exaggerated. The present invention provides a method of chrome tanning that will overcome these difficulties and give not. only a uniformly smooth surface, but an even greater area than that of the original hide, at the same time reducing thetime required.

These objects are accomplished, generally speaking, by extending the untanned skins to remove all wrinkles and folds and to stretch the skins, and holding them so extended while the fibres are being set by the tanning action.

Preferably, the skins will be pickled in the usual manner and drummed with the basic chrome sulfate solution until the latter has penetrated throughout the body of the skin.

a The skins are then removed from the wheel and slicked onto a plate with the grain face of the skin in contact with the surface of the plate.

This slicking process serves not only to remove any wrinkles or creases and to extend the skin to or even beyond its original size, but removes to more or less of the surplus watery content of the skin.

To the flesh side of the skins thus slicked out upon the plate is applied the alkaline solution in any suitable manner and amount.

The skins may be left upon the plate until the tanning'process has been completed, or if desired, they may be removed after the tanning has proceeded sufiiicientlyfar to set the skin or hide in its flat and extended condition, and the tanning completed off the plate without any substantial change in the shape or area of the hide.

As an example of one. way of practising the improved method of tanning, the skins which have been pickled with the salt and sulphuric acid solution are placed in a wheel or drum with enough water so that the skins may be able to move and slip freely over one another and the interior of the drum, and with suflicient common salt to repress the swelling of the skins. To thedrum is now added through the hollow shaft or gudgeon a solution equal to seven or eight per cent. of the weight of the drained pickled stock. The basis of this solution is basic chromium sulfate CR(OH')SO4 and is commonly mixed in the proportions of 1.8 to 2.5 pounds of the basic chromium sulfate per gallon of water.

A common and convenient method of preparing this solution is by the use of tanolin-R, so called, a satisfactory solution being secured by mixing three and one-half to five pounds of 'tanolin per gallon of water, giving a basicity in the neighborhood of 34, which facilitates and hastens the penetration and distribution of this solution into and through the hide substance.

The tanning solution is added over a period of one-half hour, during which time the wheel is in continuous motion and the skins are being drummed. This is for the purpose of uniformly distributing the tanning solution throughout so the hide substance preparatory to the actual tanning thereof.

The wheel is now stopped and the skins, which are still soft, flexible, and extensible, are removed and are slicked, grain side down, onto 8 a' fibre board or other smooth surface plate. This slicking operation smooths out and stretches the skins, the degree or amount of stretch beingcontrolled to a considerable extentby the operator. Where the maximum 0 footage is desired, the operator will work the skin out to the greatest area, reducing the thickness in so doing. If, on the other hand, a maximum footage is' not desired, but rather uniformity of thickness, the operator will endeavor 5 g to work down the thicker parts of the skin to the same thickness as the originally thinner parts.

This slicking operation also removes a great deal of the watery content of the skin which would tend to dilute and retard the action of the alkaline solution.

With the skin slicked out and extended upon the plate, a solution of a second tanning agent, viz. sodium bicarbonate, is applied to the flesh or exposed side, to render the tanning solution effective to fix or precipitate chrome 'on or in the fibres and thus to tan the skin. This solution is preferably of A to of 1% strength and is applied with a swab or sponge, usually three applications being made at intervals of one-half hour. Preferably the skin will be left on the plate for a short time after the last application inorder to secure the best results, but if desired, it may be removed after the first application with satisfactory results, as the setting of the skin or hide occurs principally in the earlier portions of the tanning operation.

Due to the fact that the skins so slicked out and extended have their entire surface ex ed to the second solution, a much quicker tanning 'action is secured than where, as previously was wise exposed to the action of'the alkaline solulimited to the use. of the specific reagents hereinbefore described, as in its broader aspects it contemplates the use of two or more reagents applied successively to the skin to set the fibres and effect the tanning thereof, while the latter is extended in smooth condition without wrinkles or creases, or is even stretched beyond its original size.

Having thus described the invention, what is claimed is:

L'That improvement in the method of tanning hides and skins which comprises subjecting 'is maintained in such extended condition with sodium bicarbonate to effect the tanning of the hide or skin.

2. That improvement in methods of tanning hides and skins which comprises subjecting the hide or skin to treatment by a tanning agent in the presence of a material for rendering such' $1011 or a o i thereof, and then immediately'\ agent ineffective and until such agent has fully slicked before the tanning has had time to proceed suflici'ently to set or fix the hide.

Instead of swabbing the alkaline solution upon the exposed face ofthe skin it may be sprayed on it or flushed or flowed onto the hide while it is being slicked or' squeegeed, thus causing a sort of pumping action to take place in and between the fibres of the skin, and thus speeding up the absorption of the tanningmaterial and hastening the tanning'operation.

Where the skins are removed from the boards before the completion of ,the tanning operation, but after the hide has been sufficiently set to permit such removal, the tamiing may be com-.

pleted by drumming the skins in the wheel with the alkaline solution.

. If" desired, instead of applying the basic chromium-sulfate to the hide by drumming, 'as above described, the pickled skin may be slicked directly onto the plate and the basic chromium sulfate applied to the exposed surface of the skin as by swabbing or spraying, the application being repeated until theliquor has penetrated throughout the body of the skin after which the alkaline solutionis applied.

In order to hasten the action of the reagents and the tanning of the hide, the tanning process may be carried out at temperatures considerably above the ordinary room temperature, but below those at which the hide would dry and shrink or "curl excessively. To avoid such drying at elevated temperatures, a relatively high humidity may be maintained. Satisfactory results have been secured by retaining :the hides between successive applications of the tanning solution in closed chambers at temperatures of 120 with 100% relative humidity.

may be applied to the plate if desired. Splits will ordinarily be slicked with the split face against the plate, although not necessarily so.

While the tanning reagents will ordinarily be applied in the form of solutions, they are not necessarily so applied but may be used in solid or semi-solid form insofar as their action permits.

* -Nor is the present invention necessarily penetrated the hideor skin, then before tanning has taken place slicking out the hide or skin upon a supporting surface, and treating the hide or skin while it is maintained on such surface with a substance to render said material inefiective inorder to permit the tanning agent -to effect tanning of the hide or skin.

3. That improvement in methods of tanning hides and skins which comprises subjecting the hide or skin to treatment in solution of a tanning agent in the presence of a retarding material for retarding the action of such agent und until the hide or skin has been fully permeated with such tanning agent, then, before tanning has 3 taken place, slicking the hide or skin out upon a supporting surface and rendering the retarding material ineffective in order to permit the tanning agent to efiect tanning of the hide or skin.

4. That improvement in methods of tanning hides and skins which comprises subjecting the hide or skin to treatment by a tanning agent duration of time sumcient, but for the acid condition of the skin, to efiect tanning thereof, and until such agent has fully permeated the hide or skin, thenstretching the untanned hide or skin upon a supporting surface, and applying to the hide or skin an alkaline solution to counteract the acid condition and cause tanning of the hide or skin while the latter i'smaintained.

on said supporting surface.

6. That improvementpin methods of tanning hides and skins which comprises drumming the hides or skins in mass in a solution of chromium salt in the presence of an acid, stretching each untanned hide or skin in extended condition and simultaneously therewith removing a large proportion of the watery content "of each hide or skin, and applying to the hide or skin an alkaline solution in a qpantity suflicient to cause the chromium salt to combine with the fibres of the hide or skin to set or tan the latter while it is maintained in its extended condition.

7. That improvement in methods of tanning hides and skins which comprises subjecting the hide or skin to treatment by a taming agent in the presence of a material for rendering such agent inefiective, stretching the untamed hide or skin, and while maintaining such hide or skin in extended condition rendering said tanning agent eflective to cause tanning action 0 the hide or skin.

8. That improvement in methods of tanning hides and skins which comprises subjecting the hide or skin to treatment by a tanning agent in the presence of an acid, then before tanning has taken place, stretching the hide or skin and thereafter rendering the hide or skin less acid to cause the tanning agent to eflect tanning thereof.

KENNETH E. BELL.

MHJTON C. MCDONALD.