US1273662A - Process of tanning. - Google Patents

Description

W. PETRIE'.

PROCESS OF TANNING.

APPLICATION FILED APR.2. 191

Patented July 23, 1918.

WALTER PETRIE, 0F ENIDICOTT, NEW YORK, ASSIGNOR TO PETRIE PROCESS COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PROCESS OF TANNING.

Specification of Letters Patent.

Patented July 23, 1918.

Application filed April 2, 1917. Serial No. 159,226.

- To all whom it may concern:

Be it known that I, WALTER Pn'rmn, a subject of the King of Great Britain and Ireland, residing at Endicott, in the county of Broome and State of New York, have invented certain new and useful Improvements in Processes of Tanning, of which the following is a specification.

This invention relates to processes of tanning; and it comprises a method of producing a quick tanning operation wherein hide, which is advantageously first set, that is treated with tanning solution enough to prevent pebbling or rainin in the subsequent operation, is wor ed wit a small quantity of a strong tanning solution, such strong tanning solution being progressively added thereto in small successive portions and the working being advantageously in a drum or the like, the amount of such tanning solution supplied being that which suflices for complete tanning and the strength being such that no substantial excess of liquor or solution remains after the operation, the whole operation being conducted under such conditions as will give suflicient ventilation for cooling and evaporating purposes; all as more fully hereinafter set forth and as claimed.

In tanning hides to make leather, all sorts of materials are employed to make the tanning liquors, a tanning action being by no means restricted to what are chemically known as the tannins. Thesetanning solutions contain materials which have a marked aflinity for the hide substance and which may be here called tans and bodies which have not this marked affinity and may be called non-tans. The latter substances however are useful in the leather. In the customary methods of tanning, the hides are treated with a large volume of the tanning liquor, whatever it may be the bath being replenished with new extract from time to time. Fromthis large volume the hides selectively absorb the tans in preference to the non-tans and the non-tans consequently accumulate as the liquor grows older. In the course of time the character of the liquor therefore is apt to change materially. In the tanning, for'the sake of quickeningthe action, agitation of. one kind or another is very common. Very frequently the hides are placed in a rotating drum containing a large body of liquor. he agitation due to rotation materially accelerates the absorption. In view of the large volume of liquor usually employed it is not customary to have it very concentrated; it is, relatively speaking, usually rather dilute. Tanning processes now customary are generally relatively slow. It is the object of the present invention to provide a quicker tanning more or less wet, adding new concentrated liqu'or as thelhides require it. In so doing I use a type of drum somewhat different from those heretofore employed for tannin pur: poses, providing means for free venti ation. The ventilation may be that due to natural circulation of air through openings in the drum or it may be a forced ventilation made by passing air through by means of a fan or the like. This free ventilation keeps the material from heating up or becoming warm and also has a useful effect in removing water as vapor, keeping the liquor concentrated. Ordinarily I use merely the amount of strong liquor which will suflice for a complete tanning; using the liquor of such strength that after my operation is completed there is substantially no excess. If there should chance to be a little excess it does no harm since it can be reused; but ordinarily I use just about the amount of liquor which will be absorbed by the hides, allowing for loss due to evaporation. In this method of'operation, since I am causing the hide to absorb substantially all the liquor, the liquor I employ must be sufliciently concentrated to afford all the tans and nontans which it is desired to have taken up by the hide. By the use of strong tan liquors I much accelerate the absorption, while the cooling given by the free ventilation and incident evaporation prevents development of heat and injury to the hides. The evaporation also operates to concentrate the liquor further and insure complete absorption. Since the present method puts substantially all the solubles of the extract into the hide, preventing the stated differential absorption f t n a the exp f o I also seabout 24 to.36 hours.

cure a better utilization of my extract, a greater weight of leather and a uniform product, my product not varying from week to week as is the case in tanning with baths of changing composition.

In the present invention the hides are ordinarily first set in a tanning solution, the object of this preliminary treatment not being to tan the hides to any extent but merely to set them enough to prevent graining, etc., in'the tanning operation proper; 2'. 6., prevent the surface from becoming puckery or coarse grained. I may take the hides from the beam house and tan them. The hides coming from the setting process which are wet and 1 contain dilute tanning solution are put into a drum together with a little strong tanning solution, say for a 7-foot. drum containing 1,500 pounds (wet weight, or what is known as white weight among tanners) I add first about 15 to 25 gallons, say 20 gallons of a strong tanning solution, say 220 barkometer or about 30 B6. The drum is provided with means causing or allowing free ventilation. The drum is rotated and the liquor is taken up by the hides, Evaporation takes place, strengthening the liquor, this evaporation being aided by the free ventilation. As the liquor is absorbed, new strong liquor is added, the time when additions are necessary being judged by the appearance of the leather and liquor. Ordinarily, additions of liquor in small portions are continued at intervals of about 18 to 24:.hours, this depending upon the thickness, etc., of the hides; a final period of about 6 to 10 hours rotation being given during which no additions are made. This results in a completely tanned leather with substantially complete absor tion of theliquor or extract used. The comp ete drumming operation takes from At no time is there more than enough liquor in the drum than will suffice to keep the leather wet and furnish a little free .liquid. The. hides are not submerged; neither is a great excess of liquor ever prefint. Under the conditions, in order toprevent heating there must be, as stated, free ventilation or other methods of cooling.

In the described operation it is better that the materials besomewhat acid; but theamount of acid needed is not great. I do not ordinarily acidify during the tanning operation proper but rely on the presence of enough acid in the hide from the preliminary operation hereinafter described.

The acidity may be that due to any mineral or organic acid.

While a wide variety of tanning materlals may be employed in the described process, I find that I can operate it very advantageously with various tanning materials comprising or consisting of preparations from waste sulfite liquor; and particularly that known in the trade as spruce extract. Spruce extract is a somewhat acidified concentrated waste sulfite liquor. Instead of, or in addition to, spruce extract, however, I may use quebracho, oak, cutch, hemlock, chestnut extracts, etc., or any other well known tanning material. Blends of the various tanning extracts may also be employed.

In an advantageous embodiment of the present invention I take the wet hides com ing from the beam house and first color them. This may be done by any of the usual methods. A good way of doing it is to treat the hides with spruce extract with which may or may not be mingled other tanning materials. Ordinarily I next treat with an acid bath. Any of the ordinary organic or inorganic acids may be em-' ployed. A bath of water containing about.- 02 per cent. sulfuric acid will serve, In this bath the hides may be hung for 24: hours or thereabouts. The hides are next treated in a setting bath which advantageously contains more or less spruce extract. An advantageous strength or solution in the setting operation, using spruce extract, is about 65 barkometer, or, around 9 Be. It is advantageous to leave the hides in the setting bath for at least two or three days. If desired, the setting bath and the acid bath may be combined, the setting bath being simply acidified with any convenient acid. From the setting bath the material 100 next goes to a rotary drum provided with ventilating means of some type wherein it is-treated with successive small additions of concentrated tanning liquor; this concentration being advantageously as high as 220 barkometer. So to speak, the hide is fed with very strong liquor at about the rate the liquor disappears. The total amount .of this liquor employed may be about equal to the white weight of the hides. After the drumming operation is complete the leather may be finished in any of the well known ways The present process gives a'good yield of good leather in about six days from beam house to bleach. While not in any way restricted to sole leather making, it is particularly advantageous therein. In acid sole leather making, it may be applied to the stock from either the first lay-aways or the I larged scale showing the ventilating opening and the splash plate.

In this showing 1 indicates an imperforate drum mounted in bearings 2 and 3 and provided with trunnions 4 and 5. Pulley (i is keyed to one trunnion. The ends of the drum are provided with openings as at 7 and with dams or splash plates 8 mounted inside the drum by means of bolts 9 and nuts 10 and washers 11. The splash plates are spaced a slight distance from the openings and practically overlap them to some extent. The liquor is introduced into the drum through pipe 12 leading from the source of supply. The interior of the drum is provided with a plurality of pins 13 which serve to catch the hides and assist the tumbling action, the hides being diagranv matically represented in the drum by reference character 14; The operation of this drum is obvious from the foregoing description.

lVhat I claim is 1. The process of tanning hides which comprises treating a hide with a small quan tity of strong liquor under conditions promoting free evaporation and cooling thereby, and successively supplying fresh small portions of liquor as previous additions tend to disappear by absorption and evaporation until the full quantity of liquor has been supplied and the hide is tanned.

2. The process of tanning hides which comprises agitating the hides in the presence of a small quantity of strong liquor in an apparatus permitting circulation of air thcrethrough and supplying fresh quantities of liquor as the liquor is absorbed.

In the tanning of hides the process which comprises substantially completely absorbing an amount of strong liquor less than that necessary to completely tan the hide and subsequently subjecting the hide to a further quantity of strong liquor, and during the process agitating and cooling the hide.

l. The process of tanning hides \VlllCll comprises agitating the same in a rotary drum in the presence of an amount of highly concentrated tanning liquor less than that necessary to completely tan the hide, ad- 1nitting-air to the hides during the rotation of the drum to evapo ate moisture and cool the hide, and adding further amounts of strong tanning liquor.

5. The process of tanning hides which comprises agitating hides with a small constantly renewedquantity of strong tanning liquor, the amount of such liquor present at any one time being insullicient to prevent free access of air to said hides.

In testimony whereof I ailix my signature hereto.

' WALTER PETRIE.

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