US642519A - Process of treating hides - Google Patents

Description

UNITED STATES PATENT OFFICE.

CHARLES S. DOLLEY AND ALBERT F. CRANK, OF PHILADELPHIA, PENNSYLVANIA.

PROCESS OF TREATING HIDES, SKINS, OR- LEATHER.

SPECIFICATION forming part of Letters Patent No. 642,519, dated January 30, 1900.

Application filed November 9, 1898. Serial No. 695,967. (No specimens.)

To aZZ whom it may concern:

Be it known that We, CHARLES S. DOLLEY and ALBERT F. CRANK, citizens of the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Processes of Treating Hides, Skins, or Leather; and we do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to certain new and useful improvements in processes for treating hides, skins, and leather; and the objects of the invention are to provide a process by means of whicha superior leather can be produced either from raw hides or skins or from such hides or skins as have been previously tawed or from such as have been partly but imperfectly tanned and which do not meet the Various tests which are commonly employed to determine perfectly-tanned leather and which are therefore susceptible to improvement.

Certain varieties of skins (as is the case with East India kips and goatskins, basils, and white leather) are for convenience of shipment or for other reasons placed upon the market in a tawed or an imperfectly-tanned condition. Such skins in many cases do not respond favorably to the usual tests for perfoot leather, and hence require subsequent treatment.

Certain methods of tanning throw upon the market a considerable amount of imperfect leather which is susceptible to improvementas, for instance, that treated with cutch or terra japonica, dividivi, &c., which, if properly tanned, would command higher prices.

It is one of the objects of the present invention to take such tawed and poorly-tanned leather and by proper treatment to convert the same into more nearly perfect leather, thusgreatly enhancing its value.

The invention has for a further object to fix in the skins or hides such substancesfor example, extractives, coloring-matter, fillers, natural and artificial tannins, &c.-as may be employed with the purpose of feeding the leather and of providing it with certain desired physical characters, such as plumpness,

weight, color, softness, impermeability to moisture, 850.

Our invention consists, essentially, of two steps, the first of which is concerned with the introduction into the hide or skin of some material or materials which will render the skin sensitive to the fixing or tanning agent employed in the second step by overcoming the agglutinatiug action of the interfibrillar ground substance (mucin, coriin, 8m.) and effect a splitting up of the connective-tissue fiber-bundles,with an accompanying swelling and separation of the fibers and fibrils, pr0- ducing thereby a fulling or plumping effect, clearing the grain and at the same time feeding the leatheri. a, impregnating the skin with materials the presence of which is desirable for the production of the physical qualities noted above. This first step has the same purpose as that commonlyattained by the employment of old and sour liquors and weak solutions of extractives and which precedes the actual tanning process. The second step of the process consists in treating the hide or skin to the action of formicaldehyd, (01120,) a material possessing the property of fixing the connective-tissue fibers and fibrils on the swelled and plumped, tawed, or partiallytanned condition produced by the first treatment and at the same time of fixing in, upon, or between the fibers and fibrils of the connective-tissue materials which have been supplied by the first step of the process to contribute special physical qualities-such as body, color, suppleness, weight, &c.-essential to a solid well-nourished leather. The use of the formicaldehyd in this second step is not a mere aggregation of elements or materials, as it is in its nature and effects entirely different from the materials employed in the first' step and could not be substituted for them to produce the effects of the first step, while itpossesses distinctive and positive characters by which it acts upon both the skin and the materials with which it has been impregnated by the first step in a manner peculiar to itself, as will be hereinafter more fully set forth.

In carrying out our invention we take ad vantage of the property possessed by various tawing and tanning agents such as alum, salt, argol, eggs, fiour,vegetable extractives, gambier, and cutch and the artificial and natural tannins used in making leather, many of which have none or only feeble tanning propertiesof causing a swelling up or separation of the fibers and fibrils of the skin-connective tissue and the deposition in, upon, and between the same of materials which prevent them from again becoming agglutinated, thereby allowing the interlacing fibers to move readily upon each other and which at the same time add material to the skin, which is of ad vantage in respect to weight, body, color, the, whereby a plump, soft, pliable, tough, and elastic leather may be produced. Owing to the manifold qualities and varieties of leather required in the various industries it is impossible for us to specify any one of the agentssuch as alum, salt, eggs, flour, extractives, reds, gambier, tannins, &c.as being capable of meeting all requirements, and in the first step of our process we hold ourselves free to use any or all materials which will produce the effect or effects desired-win, the separation and swelling of the fibers and fibrils and the clearing and raising of the grain, together with the plumping, filling, coloring, weighting, and rendering supple the skinin short, the operation preparatory to the subsequent fixing action of formicaldehyd as employed in our second step-an action in some respects analogous to that ordinarily secured by means of those tannins which are capable of rendering gelatin insoluble, but in many respects peculiar to itself.

The ultimate object of the invention in usi ug thematerials designated in the first step of our process is to secure desirable states and qualities in the hides or skins treated, which may be fixed or supplemental therein by the action of formicaldehyd subsequently applied in the second step, as hereinafter described. The following particular case will serve to illustrate the steps involved in our process.

Commercial sheepor goat skins or hides having been previously prepared for treatment by softening, unhairing, or other necessary and ordinary steps, usually referred to as beam-house treatment, are placed in a drum or reel, in which they maybe agitated by the revolving of the receptacle, by paddles, or by any other suitable means, the particular method or mechanism employed constituting no part of the present invention. We hold ourselves free to employ any form of receptacle or method of agitation whatsoever. Together with the hides or skins in the receptacle is placed a solution of gambier extract sufficiently diluted to present the extract to the entire mass of the skins, containing, approximately, four pounds of gambier .to each one hundred pounds of wet hides or skins, the exact amount of gambier being based upon the weight of the skins or hides to be treated and also upon their acidity or alkalinity, according to well-known gambier desired, in a'special receptacle.

tents agitated-factors which do not concern the principle involved in the process. When the gambier has struck through or thoroughly permeated the skins, (which may be ascertained by cutting into the thickest edge and examining the exposed interior,) the skins are rinsed in clean water; but this Washing or rinsing may, if preferred, be dispensed with, and the second step proceeded withat once, and we do not wish to be held to washing the skins as a feature essential to our process.

I live wish it clearly understood that the object of the first step of our process is, as has been previously stated, to bring the skins into a desired physical condition, characterized by such a separation and swelling of "the tissue fibers and fibrils and such plum pness, weight, color, and suppleness as will, when fixed by the chemical action of formicaldehyd, constitute a superior leather of the particular character desired. Thus we are able to develop the desired physical characters by means of alum, salt, argol, eggs, flour, the tannins, gambier, and other vegetable extracts. In the first step, therefore, it is not so much a question of the materials employed, as there is a wide choice in this respect, but rather the securing of physical qualities in the skin, which we proceed to supplement, fix, and render permanent by the second step. The use of saline and sour liquors serves to swell the tissues and fibers of the skin and to render it more readily affected by the tanning or fixing agent subsequently employed, while the vegetable extractives or their equivalents add color, weight, &c.

I The second step of our process consists in subjecting the skins or hides to the action of formicaldehyd, preferably in solution, al-

though it may be employed in the state of gas,

either in the same receptacle in which they were given the preliminary treatment, or, if The amount of the solution employed various somewhat, but is based upon the weight of the skins or hides to be treated, and we have found in practice that three pounds of commercial forty percent. (40 formicaldeh yd solution to each onehundred pounds of wet hides or skins is sufficient for ordinary sheep or goat skins. The amount of water with which the formicaldehyd is diluted is based upon the bulk of skins, being just sufficient to keep them well wetled and to present the formicaldehyd to the entire mass of the skins, but not so much as to prevent the pounding action of the skins when revolving in the drum. The skins or hides are subjected to the action of TIO formicaldehyd until permeated through and through and until they respond to the usual tests for good leather. In the particular case which is cited herein as an illustration namely, sheep or goat skins we have found that the time required is approximately three hours. The time, however, depends to avery considerable extent, as in the treatment by the first step of our process, upon the number of skins in the receptacle, and the rate and mode of agitation to which they have been subjected. It is advisable to maintain the bath in the second step at a temperature of not less than 80 Fahrenheit and not above 120 Fahrenheit, in order to secure the greatest efiiciency from the formicaldehyd, which under these conditions has greater penetratio n and less liability to polymerize than at low temperatures. After the skins are found to have been thoroughly fixed by the formicaldehyd they are washed and are then ready for the usual treatment employed in finishing.

In case the forinicaldehyd is employed in the state of a gas we prefer the following method: The skins having been brought to the desired state by the first step, as hereinbefore described, an amount of commercial formicaldehyd (forty per cent.) solution, representing, approximately, three pounds to each one hundred pounds of wet hides or skins to be treated, is placed in a suitable generator, a Variety of which are upon the market, and

. the gas generated is allowed to pass by suitable connections into the chamber containing the skins. The temperature of this chamber is preferably maintained at from 100 Fahrenheit to 120 Fahrenheit, and the atmosphere of the chamber should also be kept moist, both of which conditions are readily secured by the admission from time to time of a small quantity of warm aqueous vapor by means of a suitable steam connection. The chamber employed should be a closed one and no larger than necessary to allow the skins to be fully exposed to the action of the gas. If desired, the gas may be admitted to the drum in which the preliminary treatment took place or into a similar drum and the skins agitated therein, or the skins may be stretched on suitable frames and inclosed within a stationary chamber, in either case being exposed to the action of the gas until they respond to the usual tests for good leathersay for a period of six hours-the time depending, however, on the thickness and character of the skins under treatment.

The market supplies certain tawed or imperfectly-tanned skins and hides which have been already subjected to the action of salt and alum, fiour, eggs, vegetable extractives, gambier,cutch,tannins,orother materials and which do not constitute high-grade leather, but which are susceptible of improvement. The effects produced on these skins are analogous to those produced by the first step of our process, and we find it both possible and advantageous to take such skins and after softening them in water proceed to treat them as described in the example cited for treating raw skins, whereby we are able to secure the results of. the first step with less time and material than would be required in treating green or raw hides or skins, and in certain cases where the tawed or imperfectly-tanned skins or hides have the plumpness, color, weight, &c., desired and which we would have secured by means of our first step we may proceed at once to the second step of the process, which consists, essentially, in the fixation of the natural or added constituents of the skin, substantially as described.

\Ve have found bya large number of practical tests that the actual tanning efiect of the natural tannins as introduced into the skin by the first step of our process may be greatly hastened and augmented by the employment of .formicaldehyd in conjunction therewith as accomplished by the second step of our process. Thus with the pyrogallol tannins, a considerable proportion of which possesses little or no tanning power, a compound is formed whereby all the tannin is rendered available, and consequently a greater action secured from a given amount of-extracta matter of importance in point of economy. Again, we find that by means of formicaldehydused in conjunction with, but subsequent to, the use of those natural (catechol) tannins containing phlobophanes or reds, as introduced into the hides by the first step of our process, these substances, which in:many instances are insoluble and not directly available for tanning, can be fixed in the leather; and, again, with other (pyrogallol) tannins the deposit of whites or bloom is prevented, the ellagic acid or catechin being in some way altered and in.- dissolubly bound in combination with the skin substance, as are also certain extractives (e. g., gambier) by the action of the formicaldehyd upon the impregnated collagen of the skin, whereby an occlusion of the introduced material is brought about, and also by its direct action upon the catechus themselves, whereby they are rendered insoluble and precipitated as a filling and coloring material upon and between the fibers and fibrils of the skin-connective tissue, thus effecting what is technically known as feedthey are when subjected to its action, and we have found that it is highly advantageous in using formicaldehyd in the manufacture of leather to prepare the skins or hides by some preliminary treatment, as by our first step, whereby the fibers and fibrils of the connective tissue are properly separated and swelled or plumped, colored or filled, as seems desirable in the particular case in hand, when they, together with the other gelatigenous constituents of the skin, may be fixed in the particular state desired, by the use of formicaldehyd as has been previously described, and which constitutes the second step of our process. Our invention therefore'proposes the application of formicaldehyd to hides and skins, the collagen of which is either not at all or but partially combined into insoluble compounds either, first, from a lack of suitable quality in the agents used in the preliminary treatment, such agents being, for example, salt, eggs, flour, alum, argol, vegetable extractives, gambier, cutch, and such other tannin-containing materials possessing little or no tanning properties, or, second, from lack of sufficient combination with an agent, such as oak or hemlock tannin, which is potentially capable of saturating the collagen and forming therewith an insoluble and imputrescible compound, but which in the skins we propose to treat has de facto not fully saturated the collagen. In other words, We propose to apply formicaldehyd to hides or skins containing a soluble ..collagen compound or unsaturated collagen. We therefore employ formicaldehyd to fix the collagen of the skins after the skins have been prepared by such processes as produce the qualities peculiar to ordinary salt and alum tawed skins, chamois-leather, oil -tawed leather, Wash-leather, Knapps leather, &c., or the peculiar leather resulting from the employ-- ment of gambier and similar vegetableextracts or where the fixation of the tissue constituents has been imperfectly accomplished by the ordinary tannin g processes. The skins may be specially prepared, or tawed skins, chamois-leather, &c., .may be taken ready prepared and submitted to the fixing action of formicaldehyd.

Much of the leather commonly regarded as well tanned is open to great improvement, and our invention proposes the employment of the ordinary processes of tanning as our first step or the taking of commercial leather already prepared by others and submitting it to the fixing and supplemental action of formicaldehyd as a second or final step in the production of perfectly-tanned leather. Our invention therefore involves the use of formicaldehyd subsequent to the use of tawing or tanning materials, and inasmuch as these materials give varying degrees of plumpness, weight, density, and color to hides and skins our invention necessarily involves the use of formicaldehyd in conjunction with all materials producing these eifects in accordance with our process as hereinbefore described.

(e do not confine ourselves to the use of any one tawing or tanning, plumping, feeding, or coloring material in conjunction with formicaldehyd, as our process is not limited to the production of any one kind of leather, but is applicable to the production of either light or heavy leather, white or colored, as desired-in fact, to all varieties of leather, and its employment as herein described results in a very material saving in time, labor, and materials. I

We desire to have it understood that in the use of the word tanning in this specification we use the word in its broad or generic sense.

Having thus described our invention, What We claim to be new, and desire to secure by Letters Patent, is-- 1. The process for the production of leather, which consists in the application of formicaldehyd to hides or skins which have previously been treated with tanning or tawing materials to such an extent that only a mechanical or loose chemical combination with the collagen has been effected.

2. The process for the production of leather, which consists in submitting to formicaldehyd, skins which have been tanned as far as possible by the ordinary tanning agents.

The process for the production of leather, which consists in treating hides or skins with tanning materials incapable of rendering the gelatigenous constituents of the skins insolu ble, and then submitting the skins or hides to the action of formicaldehyd.

4. The process of producing leather, which consists in submitting to the action of formicaldehyd, skins or hides in which the fixation of the gelatigenous constituents has been imperfectly accomplished by the ordinary tanning processes. I

5. The process of producing leather, consist-in g in subjecting hides or skins to tanning materials to such an extent that the hides or skins are converted into completely-tanned leather, the tanning material being of sucha character that the leather so produced when immersed in water becomes hard byreason of a partial breaking up of the compounds between the tanning material and the collagenous matter of the skins, and then subjecting the leather to formicaldehyd, whereby the leather is rendered waterproof, the compound of collagen and the tanning material being rendered incapable of being broken up by water and the leather remaining soft after soaking in water.

In testimony whereof we affix our signatures in presence of two witnesses.

CHARLES'S. DOLLEY. ALBERT F. CRANK.

Witnesses:

CHAS. I-I. BANNARD, WALTER T. STOKES.

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