US2937068A - Depilating predetermined areas in leather preparation - Google Patents

Description

loosen. After removal ofthewool, the skin is in. detail.

DEPILATING PREDETERMINED AREAS IN LEATHER PREPARATION Frank W. Panepinto, Philadelphia, Pa., assignor to William Amer Company, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Original application March 11, 1958,- Serial No.. 720,538. te nher 2, 1958, Serial No. 758,612

7 Claims. (Cl. 8'--9=4.16)

This invention relates to a process for preparing leather, and more particularly relates to a process for preparing hides and skins for conversion into leather, and to the leather thereby produced.

The conversion of hides and skins into leather by satisfactory in that the hair roots, and/ or hair stubs. which Divided; and this application Sepremain, impart to the leatheran unsightly. appearance. and, a rough surface, and finishing operations, such. as. dyeing are difficult to perform.

An object of the present invention is to provide. a,

process'for preparing leather. Another object is, to provide a process for preparing hides and skins for tanning and, conversion into leather. A particular object is to. provide a process for preparing hides and skins for tanning in which the hair of the hide or skin remain attached thereto on predetermined areas. thereof, and. in.

which all of the hair and hair roots are removed from, the, remaining predetermined areas. A further objest is to provide a process for preparing leather wherein the, leather contains on predetermined areas, the original.

3 hair of the hide or skin from which the leather was.

tanning has long been practiced. As performed heretofore, hides and skins are generally cured as by packing with salt, soaking in a saturated brine solution, or drying, to prevent spoilage thereof before the tanning operation. The cured hides or skins, after sorting according to weight and size and trimming off unwanted areas, are soaked in water to rehydrate the skins, wash away any loose dirt and extraneous materials, and make the hides and skins pliable and ready for subsequent processmg.

Although the preparation of leather with all of the original hair remaining attached to the hideor skin. has been described, most leathers are made with all of the hair removed. Hair removal is usually accomplished by soaking the hide or skin for about 5 days ina lime bath containing, for example, about 12% hydrated lime based on the weight of the soaked and trimmed hide orskin. Sharpening agents such as sulfides or cyanides. may be added to reduce the time required for loosening the hair. The. hairloosened by thev liming operation is removed mechanically by unhairing machines, and if necessary completeremoval is achieved by hand operations. With some skins, such as sheepskins, de-wooling may be performed by. contacting. the flesh side of the skin with an unhairing agent such as a lime-sulfide paste which penetrates through the entire skin and causes the wool to then limted as-above described.

After removal of .hair. from the skinsor hides, any loose fatty. tissue, meat. or muscle is removed by fleshing machines and the resulting hide or skin. is subjected to tanning'operations. These tanning operations generally include bating, pickling, and then chrome tanning bythe one. bath or two. bath method, or tanning with vegetable and/or synthetic tanning agents. These tanning operations, are well known and hence are not described herein Finishing operations are then used, such as shaving the fiesh, splitting, dyeing, oiling, and mechanical softening, which operations are also well known,

As above stated, hair is generally completely removed from skins and hides prior to tanning, but the tanning of skins or'hides having all of theoriginal hair thereon has been described. However, the tanning of skins or hides having a portion ofthe original hair has not heretofore been described. In order to prepare leather having 'a portion only of the original hair thereon, according "to prior teachings, it has heretofore been necessaryto tan-a hide or skin with all of the original hair thereon andto clip or shave the hairfrom the leather to obtain the desired article. Such operations, however, are not prepared. A further specific object is to provide a newarticle of manufacture comprising leather having, on predetermined areas thereof, hair of the original hide or skin,

It has now been found that, by applying an unhairing agent to predetermined areas of a hide or skin for a time sufficient to destroy the roots of the hair of such areas, as; hereinafter fully described, the hair of the so-destroyed roots is readily removed leaving the remainder of the original hair on the remaining predetermined areas, and that the so-treated hide or skin can then be tanned and finished as desired to produce novel articles of manufacr ture.

The term hides generally refers to larger animals, as cowhide and horsehide, and skins generally refers to smaller animals, as goatskin, kidskin, sheepskin, pig;

skin, and calfskin, and the process of the invention can beused with all of such hides and skins. For conveni nee, the term skins is hereinafter used as including both hides and skins as above described. The process of: the invention is especially useful with cowhide, goatskin and calfskin, but the invention is not so limited. Pelts can also be employed in an embodiment of the invention, as hereinafter described.

In, accordance with an embodiment of the process. of the present invention, a skin is prepared for tanning in the usual manner up to the unhairing step. An unhairing; agent is then applied to predetermined areas .onlyof the skin, leaving untreated with the unhairing agent the remaining predetermined areas so that, on completion of the tanning process, a portion of the original hair of the-skin is attached to the leather according :to a predetermined pattern as hereinafter more. fully described. The application of the unhairing agent'to predetermined areas only of the skin can be accomplished by any convenient means. A preferred means is to mask the areas on the hair side of the skin where the original hair is to, remain, or to mask the areas on'the flesh side of the skin opposite which are the areas on which the hair is to remain, and to apply a solution or paste of an unhairing, agent to the remaining areas, which remaining areas are the exposed areas. Conveniently, a template such as asheet metal pattern is pressed against the skin so that only the areas with which the unhairing agent is to be contacted are exposed, and they unhairing; agentis then applied thereto so that the masked areas-of predetermined size, shape and number are unaffected thereby. Other means of applying the unhairing agent can be used, such as by contacting predetermined.v areas with a relativelyv thick paste thereof which does not spreadto the remaining areas to any significant extent. latter means canbe accomplished, for example, by coating the strands of a screen of the desired pattern with the unhairing agent and contactingv same with the skin; the voids a in the screen form the predeterminedyareas within which "the'hair'is notremoved: T

Unhairing agents which can be used are those matecyanides, calcium hydrosulfide, sodium hydro'sulfide, so-

dium hydroxide, potassium hydroxide and organic amines, used individually, as mixtures with each other and/or with lime illustrate preferred unhairing agents which give good results. Mixtures of the described sulfides, cyanides or hydrosulfides with a strong alkali such as lime are preferred. Aqueous solutions of the unhairing agents can be used, but pastes thereof with water give best results in that there is less tendency for the agent to spread laterally through the corium and destroy the hair roots of adjoining areas, and faster destruction of the hair roots are accomplished with the relatively strong concentration of the unhairing agent when used as a paste. For example, a preferred unhairing composition may consist essentially of 1 part by weight of sodium sulfide, 2 parts by weight of calcium hydroxide (lime), and 2 parts by weight of water. Calcium or sodium hydroand contacted with exposed skin. After about 20 minutes: the template and excess paste was removed and the skin was immediately immersed in hydrochloric acid containing dissolved ammonium sulfate, the solution having a pH of about 1. This solution quickly penetrated the skin and killed the efiicacy of the paste for destroying hair roots. The skin was then washed to remove excess acid and salts formed during the reaction of the acid with the alkaline unhairing agents. The so-treated skin was unhaired to remove only the hair on the skin areas which were opposite-the areas contacted by the paste. Hair on the remaining areas of the skin remained strongly to the skin and could not be removed by usual sulfide containing enough lime to give a thick paste also I illustrate the preferred unhairing agents.

The time of contacting the unhairing agent with the predetermined areas of the skin is a critical factor in the process of the invention. Enough time of contacting to effect the desired destruction of the hair roots located within or substantially within the areas of application must be allowed, but longer times are deleterious in that the unhairing agent, especially if applied as a solution, tends to spread laterally a substantial distance through the corium thereby destroying hair roots in blocked-off areas. Hence a time just sufiicien-t to permit destruction of the root hairs must be allowed, but appreciably longer times are deleterious. The time of contacting will vary according to the type of skin being used, the thickness thereof and whether the agent is applied to the hair or flesh side of the skin, the prior treatment of the skin, and the particular unhairing agent being used and the concentration thereof. Simple testing can advantageously be used to determine the optimum time in a given instance. In general, a time of from 15 to 45 minutes will be used when goatskin is being treated using a paste of about equal parts of lime, sodium sulfide and water.

After the unhairing agent has remained in contact with the predetermined areas for the desired time, the skin is contacted preferably by immersion, with an aqueous solution of a material capable of rapidly penetrating the skin and killing the eflicacy of the unhairing agent. Preferably an aqueous solution of an acid such as hydrochloric acid, acetic acid, sulfuric acid, or phosphoric acid, or an aqueous solution of an acid salt such as ammonium sulfate, ammonium chloride, sodium bisulfate or potassium bisulfate, or a mixture of an acid and an acid salt, is used. Such contacting practically immediately stops the unhairing action and prevents the unhairing of areas other than where desired.

In order to illustrate the invention, it Was desired to prepare leather having the original hair of the skin thereon except for round areas of about inch in diameter with the centers thereof spaced about inch apart.

To prepare this leather, in accordance with an embodiment of the invention, a cured kidskin was soaked in water to rehydrate the skin. The soaked skin was pliable and free from loose dirt and extraneous materials. After 'fleshing, a metal template containing holes of about A inch in diameter with the hole centers spaced about inch apart was firmly pressed against the flesh side of the skin, the template being of a size to cover substantially the entire surface of the skin. A paste consisting .of about 1 part by weight of sodium sulfide and 2 parts by'weight of both lime and water was then spread over the template so that the paste entered the holes thereof mechanical unhairing operations. The skin was then con-' tacted with bating materials according to usual practice, and thereafter was picked in an aqueous solution of sodium chloride and sulfuric acid having a pH of about 2, also in accordance with usual practice. The sotreated skin was then chrome tanned by the one bath process according to usual procedures. The resulting leather contained the original hair except on the predetermined round areas opposite the areas contacted with the unhairing agent. The round areas free of hair had a diameter of about inch as compared to the A inch diameter areas treated with the unhairing agent, the slightly larger size being due to slight lateral spreading of the unhairing agent while penetrating the skin to the embedded hair roots. In predetermining the size and shape of the areas to be treated with the unhairing agent, al-

lowance should be made for this lateral spread of the unhairing agent. By contacting the skin with the unhairing agent for a minimum time, i.e., for a time just sufficient to destroy the hair roots,.this lateral spread of the unhairing agent is controlled and maintained at a minimum value which can be readily determined by simple tests. The resulting chrome tanned leather withstood, without curling or shrinking, being immersed for at least 5 minutes in water held at 95 C.

The chrome tanned leather was dyed blue using usual procedures, fatliquored, dried, and subjected to mechanical softening. The hair was then clipped to about inch length. The hair attached to the leather was black and practical effects were obtained in accordance with the present invention.

By operating in accordance with the process of the invention, patterns formed by unhaired areas on leather can take any desired shape, such as triangular or rectangular, or a line or a multiplicity of lines, straight, curved, or the like can be obtained. Generally, to obtain preferred leathers in accordance with the invention, pre' determined areas from which hair is removed will constitute from about 10% to 50% of the total area of the skin, but in some instances such as where special ornamental etfects are desired, the hair may be removed from about 75% of the total area. The novel leathers of the invention, characterized by having the original hair on predetermined areas thereof and being free of hair on the remaining predetermined areas, the areas free of hair being further characterized by the absence of hair roots and hair stubs, have many uses. For example, substantial advantages are obtained by using these leathers as shoe uppers, wearing apparel such as jackets, coats and skirts, and the like, and assessories such as belts, hand- .bags and gloves. Thus, in addition to the highly ornamental effects obtained, which greatly enhance the value of such articles, the remaining original hair gives added protection to the articles formed therefrom, and in some instances to the wearer of articles made therefrom, and the unhaired areas may be predetermined so that various articles such as buttons or other fasteners, or other materials such as cloth or other leathers, can readily be attached thereto for forming useful articles of manufacture.

Numerous variations can be made in the process of preparing leather without departing from the scope of the invention. Thus, the process of unhairing predetermined areas of a skin can be applied at any point in the process of converting skin into leather where all of the hair is normally removed, or where the skin is in a condition such that all of the hair thereon could be removed by known unhairing procedures. A still further variation, which constitutes a preferred embodiment of the invention, is to perform the unhairing of predetermined areas on a dry or cured skin. In this embodiment, the water of the paste or solution of the unhairing agent provides for the penetration of the unhairing agent to the embedded hair roots. This embodiment is especially valuable where sharp demarcation between the unhaired areas and the remaining areas is desired; it appears that where the moisture present is supplied solely by the unhairing composition, there is less tendency for the agent to spread laterally through the corium.

In a still further embodiment of the invention, the unhairing of predetermined areas is applied to a fully tanned skin containing at least a portion of the original hair attached thereto. Thus, as has been found, unhairing in accordance with the invention can be used on tanned skins. This embodiment is especially valuable where it is found that complete unhairing of areas, where such unhairing was desired, was not accomplished in the process, for example because of variations in the thickness of the skin so that uniform penetration of the unhairing agent was not obtained. Such areas can be unhaired by repeating the unhairing operation as above described, such as by using the same template as used in the original unhairing operation, and applying the unhairing agent only to those areas where needed. It has been found that the unhairing of tanned skins, in accordance with the invention, does not weaken or have other deleterious effects on the leather. It is preferred, however, to complete all unhairing operations prior to dyeing the skin.

Considerable variation can be made in finishing operations with the novel leathers of the invention, and highly desirable effects obtained therewith. For example, by performing the unhairing operation in accordance with the invention, and by controlling the remaining tanning operations, such as bating, a substantial portion of the epidermis can be made to remain on the skin within the areas containing the original hair. By

using a mixture of dye colors, such as a mixture of blue and yellow, the epidermis can be selectively dyed by one of the dye components, such as yellow, while the remainder of the leather is dyed by the combination of colors, which in the described instance will be green.

Although the process of the invention is especially applicable to skins, as above-described, the process can be used with pelts of fur-bearing animals such as mink, sable, ermine, fur seal, rabbit, and the like. In this application, the process of the invention is performed substantially as described above. An unhairing agent is contacted with predetermined areas only of a pelt, preferably on the flesh side thereof, and the fur opposite the treated areas is removed. The pelt is then dressed according to usual procedures, and it is intended that pelts be included in the hereinabove definition of skins.

This application is a division of United States Serial Number 720,538, filed March 11, 1958.

The invention claimed is:

1. Process for preparing leather which comprises coritacting predetermined areas of a skin with an unhairing agent for a time sufiicient to destroy the hair roots ernbedded within the contacted areas, removing hair having so-destroyed roots, and tanning the resulting skin whereby leather having the original hair of the skin on predetermined areas is produced, the hair-bearing and unhaired areas constituting the basis for a design pattern over the skin.

2. Process according to claim 1 wherein said unhairing agent iscontacted with predetermined areas of the flesh side of the skin.

3. Process according to claim 1 wherein said unhairing agent is contacted with predetermined areas of the hair side of the skin.

4. Process for preparing leather which comprises rehydrating a cured skin, contacting only predetermined areas of the flesh side of the skin with an unhairing agent for a time sufficient for said unhairing agent to destroy the hair roots embedded within said predetermined areas, removing the hair having the so-destroyed roots from the skin, and thereafter bating, chrome tanning and dyeing the skin, the hair-bearing and unhaired areas constituting the basis for a design pattern over the skin.

5. Process for preparing leather which comprises contacting only predetermined areas of a dry skin with an unhairing agent including water for a time sufficient for said unhairing agent to destroy the hair roots embedded within said predetermined areas, removing the hair having the so-destroyed roots from the skin, and thereafter tanning the skin, the hair-bearing and unhaired areas constituting the basis for a design pattern over the skin.

6. In a process for preparing leather including the steps of removing hair from the skin and thereafter tanning the skin, the improvement which comprises contacting only predetermined areas of the skin with an unhairing agent, whereby hair roots embedded within such contacted areas are destroyed, removing the hairs having so-destroyed roots, and tanning the resulting skin whereby leather having hair 'on predetermined areas thereof is produced, the hair-bearing and unhaired areas constituting the basis for a design pattern over the skin.

7. In a process for preparing leather including the steps of rehydrating a cured skin, removing the hair from the skin, and thereafter bating and tanning the skin, the improvement which comprises contacting only predetermined areas of the flesh side of the skin with an unhairing agent for a time sutficient for said unhairing agent to destroy the hair roots embedded within the contacted predetermined areas, removing the hair having the so-destroyed roots from the skin, and tanning the resulting skin whereby leather having'hair only on predetermined areas thereof is produced, the hair-bearing and unhaired areas constituting the basis for a design pattern over the skin.

References Cited in the file of this patent UNITED STATES PATENTS Re. 11,849 Gibson Aug. 28, 1900 629,526 Scott July 25, 1899 1,977,226 Bell et al. Oct. 16, 1934 2,188,601 Kusikoff Jan. 30, 1940 2,585,610 Wittwer Feb. 12, 1952 2,775,504 Zalcman Dec. 25, 1956

Claims (1)

1. 7. IN A PROCESS FOR PREPARING LEATHER INCLUDING THE STEPS OF REHYDRATING A CURED SKIN, REMOVING THE HAIR FROM THE SKIN, AND THEREAFTER BATING AND TANNING THE SKIN, THE IMPROVEMENT WHICH COMPRISES CONTACTING ONLY PREDETERMINED AREAS OF THE FLESH SIDE OF THE SKIN WITH AN UNHAIRING AGENT FOR A TIME SUFFICIENT FOR SAID UNHAIRING AGENT TO DESTROY THE HAIR ROOTS EMBEDDED WITHIN THE CONTACTED PREDETERMINED AREAS, REMOVING THE HAIR HAVING THE SO-DESTROYED ROOTS FROM THE SKIN, AND TANNING THE RESULTING SKIN WHEREBY LEATHER HAVING HAIR ONLY ON PREDETERMINED AREAS THEREOF IS PRODUCED, THE HAIR-BEARING AND UNHAIRED AREAS CONSTITUTING THE BASIS FOR A DESIGN PATTERN OVER THE SKIN.