US1953968A - Method of tanning hides and skins - Google Patents

Description

Patented Apr. 10, 1934 UNITED STATES PATENT OFFICE I METHOD or TANNING RIDES AND SKINS No Drawing. Application January 12, 1931,

. Serial No. 508,375

11 Claims.

This invention relates to the tanning of hides and skins and more particularly to combined tannages involving treatment of the hides and skins with both vegetable and mineral tanning substances.

In accordance with methods heretofore employed in securing combination tannages of hides and skins, the latter were tanned throughout their whole substance when subjected to a mineral tanning material and also when treated with a vegetable tanning material, irrespective of the order of sequence of the mineral and vegetable tanning operations. Furthermore, in the first tanning operation, whether by mineral or by vegetable tanning matter, no special care was taken of the tender grain surface of the hide or skin nor any provision made against shrinkage of the hide or skin during such tanning operation. For instance, it was common, particularly in tanning by mineral substances, to dump a mass of hides or skins into a drum, the inner surface of which was'provided with projecting pegs or shelves, and to begin rotation of the drum at once without in any way protecting the tender grain surface of the hides or skins. Furthermore, in such handling of hides and skins there was sure to be very considerable shrinkage which made it impossible to secure the desired footage, particularly from skins, even though a stretching operation was attempted following the completion of the tanning operation. It is a fact, moreover, that any wrinkled or folded portion of a hide or skin which is tanned in such wrinkled or folded condition cannot subsequently be made to have the appearance of a fine smooth grain surface, since such wrinkles or folds persist, to a great extent at least, in spite of treatment intended to obviate them.

Objects of the invention are to speed up the tanning of hides and skins, to obtain a better product, and, in the case of skins particularly, to secure greater area in the finished leather than has been possible by the methods previously employedin combination tanning.

To these ends, and in accordance with an important characteristic of the invention, a hide or skin is first treated with an inorganic substance such as a mineral tanning material capable of rapid penetration, the application of the tanning material being made while the hide or skin is spread out or stretched in extended condition upon a supporting surface, the hide or skin being maintained in such spread out or stretched out condition for a time substantially just suflicient to insure such a set to the fibers of the hide or skin that the latter will maintain its extended area when later subjected to treatment by tanning substancesin other operations, such as that of drumming, designed to complete the tanning of the hide or skin. By mineral tanning 6O material is meant tanning material of other than vegetable or animal origin. Conveniently a chromium tanning compound is applied to the grain surface of a hide or skin while the latter is in spread out ,or stretched out condition, the advantages being that the chromium compound quickly gives the tender grain surface a protective tanning and also penetrates into the hide or skin with relatively great rapidity so that the latter may be removed from its supporting surface after a relatively short time has elapsed without danger of any substantial amount of shrinkage taking place. In the case of a thin skin the treatment may take only a few minutes while in the case of heavy hides as much as an hour or two may be required. Following the desired set of the fibers of a hide or skin the latter may be subjected to tanning operations with vegetable tanning agents while in extended condition on a supporting surface. Preferably, however, the hide or skin, with many others which have received like preliminary treatment, is thrown into a drum having a strong or concentrated solution of one or more vegetable tanning substances, and the drumming continued until tanning is completed. a 35 In the practice of the method of tanning hides and skins according to this invention, a hide or skin will be spread out in extended condition upon a smooth supporting surface with the grain surface facing upwardly and exposed to the atmosphere. In the case of both hides and skins, a large portion (substantially half, more rather than less) of the watery content of each hide or skin will be removed either manually or by the use of a suitable machine either before spreading the hide or skin out on a work support or simultaneously with the spreading out operation. The stretching out of the skin and the removal of water therefrom is conveniently accomplished at one operation by slicking the skin out on a smooth supporting surface. In the case of skins, as distinguished from hides, each skin will be stretched out in fully extended condition on the work support before the application of any tanning material so that the full area of the skin may be obtained in the finished leather. In the case of hides, it is essential that each hide be spread out to remove all wrinkles and folds but it is not necessary to employ stretching operations since the leather made from hides is relawell-known Martin Dennis solution tively thick and heavy and is sold by the pound and not by the square foot, as is the case with light leathers made from skins. The new and improved method of tanning which involves the spreading or stretching out of the hide or skin upon a supporting surface, and the removal of a large proportion or, in some cases, the larger portion, of the watery content of a hide or skin, prior to any tanning of the hide or skin, and also the maintenance of the hide or skin in spread out or stretched out condition until the hide or skin has set in such extended condition, is described and claimed in my copending application Serial No. 402,319, filed October 24, 1929, and hence will not be claimed herein. In the step of preliminarily tanning this spread out or stretched out hide or skin from which the desired amount of water has been removed, a strong basic chrome tanning liquor, for instance, the (United States Patent No. 511,411, December 26, 1893) is applied to the exposed surface. It is to be understood, however, that the method herein described is not limited to the use of chrome or other mineral salts, since organic substances,

' such as formaldehyde, may be employed. In the case of a relatively light skin one application only is needed, whereas with heavier skins or hides several applications may be required and allowed to act until the hide or skin fibers have been tanned to a sufficient depth to insure that the hide or skin will maintain its smooth grain sur-- face and its extended area upon subsequent treatment. The hide or skin may then be finished, before any substantial drying thereof has taken place, by one or more applications of a strong or concentrated solution of a vegetable tanning material either while it is stationary upon a work supporting surface or by introducing it into a vat or drum. By concentrated solution is meant one of a strength not substantially less than 100 Bkr. and by a strong solution one of a strength less than 100 but not substantially less than Bkr.

In the case of hides intended particularly for soles of boots and shoes, vegetable tanning of the hide secures a better quality of leather for the purpose intended than does mineral tanning, since such leather is firmer and of better appearance, although less resistant to the softening action of water. On the other hand chrome sole leathers are more durable than vegetable ondly, a complete tanning with suitable vegetable extracts. Occasionally this order of mineral and vegetable tanning is reversed but always to meet special requirements in the leather thus produced. The present method involves the application of a mineral tanning compound to one surface or to both surfaces of a hide or skin to tan and thus preserve the tender grain surface thereof, the tanning being continued for such length of time only as will secure setting of the hide or skin in its extended area. Preferably the preliminary tanning will be secured by an application of the tanning material to the grain surface to secure a finely tanned grain surface not subject to injury even when subsequently subjected to the relatively rough tanning operation of drumming. In applying the mineral tanning substance to both surfaces of the hide or skin, the latter must be spread out or slicked out twice upon a work supporting surface with first one surface and then the other exposed for treatment, as disclosed in said prior application.

After the hide or skin has been allowed to remain on the supporting surface with the chrome liquor applied thereto for the desired length of time, the hide or skin is preferably introduced with many others, which have received like treatment, into a drum containing a strong tanning solution of one or more vegetable extracts. The drumming of the hides or skins is continued until thorough penetration of the hide or skin is secured. The hides or skins are then removed and finished in the ordinary manner.

Having described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. That improvement in methods of tanning hides and skins which comprises spreading a hide or skin out in fully extended condition upon a supporting surface, applying a mineral tanning agent to the hide or skin while in extended condition, permitting it to act for a time substantially just suflicient to secure setting of a hide or skin in its spread out condition, and then subjecting the hide or skin to treatment with a tanning agent until it is thoroughly tanned throughout.

2. That improvement in methods of tanning hides and skins which comprises spreading a hide or skin out in fully extended condition upon a work supporting surface, applying a tanning solution of a chromium salt to the hide or skin while in extended condition, permitting the tanning solution to act for a time substantially just sufiicient to secure such a set to the fibers of the hide or skin as will maintain the latter in spread out condition, and while still moist subjecting the hide or skin to treatment with a solution of a vegetable tanning agent to complete the tanning operation.

3. That improvement in methods of tanning hides and skins which comprises applying -a strong solution of a mineral tanning agent to both surfaces of a hide or skin, permitting the mineral tanning agent to operate fora time substantially just sufficient partially to tan the hide or skin to secure setting of the fibers of the hide or skin to an extent sufficient to subsequent shrinkage thereof, and subsequently subjecting the hide or skin to treatment with a solution of a vegetable tanning agent to complete the tanning operation.

4. That improvement in methods of tanning hides and skins which comprises applying a strong solution of a mineral tanning agent to the flesh side of a hide or skin, permitting the mineral tanning agent to operate for a time substantially just sufilcient to secure the minimum setting of the fibers of the hide or skin which will maintain the area thereof, and subsequently drumming the hide or skin in a solution of a vegetable tanning agent to complete the tanning operation.

5. That improvement in methods of tanning hides and skins which comprises applying a strong solution of a mineral tanning agent to the grain side of a hide or skin, permitting the mineral tanning agent to operate for a time sub stantially just suflicient to secure tanning of the grain surface and such setting of the fibers of the hide or skin as will serve to maintain the area thereof, and subsequently drumming the hide or skin in a solution of a vegetable tanning agent.

6. That improvement in. methods of tanning hides and skins which comprises applying a strong solution of a mineral tanning agent to a hide or skin, permitting the mineral tanning agent to operate for a time substantially just sufficient to secure taming of the grain surface and substantially the'minimum setting of the fibers of the hide or skin which will serve to maintain the area thereof, and subsequently drum ming the hide or skin in a solution of a vegetable tanning agent to complete the tanning operation.

7. That improvement in methods of tanning hides and skins which comprises stretching a hide or skin out in fully extended condition upon a supporting surface, applying a mineral taming agent to the hide or skin while in fully extended condition, permitting it to act for a time suflicient to secure setting 01 the hide or skin in its spread out condition, and then subjecting the hide or skin to treatment with a solution of a vegetable tanning agent.

8. That improvement in methods of tanning hides and skins which comprises stretching a hide or skin out, in fully extended condition upon a supporting surface, applying a tanning solution of a chromium salt to the hide or skin while in fully extended condition, permitting the tanning solution to act for a time sufficient to secure tanning of the grain surface of the hide or skin and such a set to the fibers of the hide or skin that they will maintain the latter in spread out condition, and before any substantial drying thereof has taken place drumming the hide or skin in a solution of a vegetable taming agent to complete the tanning operation.

9. That improvement in methods of tanning hides and skins which comprises applying a solution of an inorganic tanning agent to a hide or skin, permitting said tanning agent to operate for a time substantially just suflicient to secure tanning of the grain surface but no more setting of the fibers of the hide or skin than is necessary to maintain the area thereof, and subsequently drumming the hide or skin in a solution of a vegetable tanning extract to complete the tan- .ning operation.

10. That improvement in methods of tanning hides and skins which comprises slicking a hide or skin out in fully extended condition upon a supporting surface, applying a rapidly penetrating mineral tanning agent to the hide or skin while in fully extended condition, permitting it to act for a time sufl'icient to secure setting of a hide or skin in its spread out condition, and then'subjecting the hide or skin to treatment with a strong solution of a vegetable tanning extract.

11. That improvement in methods of tanning hides and skins which comprises slicking a hide or skin out in fully extended condition upon a supporting surface, applying a tanning solution of a chromium salt to the hide or skin while in fully extended condition, permitting the tanning solution to act for a time sufficient to secure tanning of the grain surface of the hide or skin, and such a set to the fibers of the hide or skin that they will maintain the latter in spread out condition, and subsequently drumming the hide or skin in a solution of a vegetable tanning extract to complete the tanning operation.

MATTHEW M. MERRII'I'.