US3298851A

US3298851A - Embossed leather and process for preparing the same

Info

Publication number: US3298851A
Authority: US
Inventors: Fuchs Hermann
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 1963-12-05
Filing date: 1964-11-30
Publication date: 1967-01-17
Anticipated expiration: 1984-01-17
Also published as: BE656622A; DE1435279A1; NL6413570A; GB1049730A

Description

' an- 17,1967 H. FUCHS 3,298,851

EMBOSSED LEATHER AND PROCESS FOR PREPARING THE SAME Filed Nov 'o'o, 1964 INVENTOR HER/MANN FUCHS BY I I 3 M9 w q' rOR 5 United States Patent 3,298,851 EMBOSSED LEATHER AND PROCESS FOR PREPARING THE SAME Hermann Fuchs, Weinheim an der Bergstrasse, Germany,

assignor to Carl Freudenherg, Weinheim an der Bergstrasse, Germany, a corporation of Germany Filed Nov. 30, 1964, Ser. No. 414,813 Claims priority, application Germany, Dec. 5, 1963, F 1,475 17 Claims. (Cl. l1711) The present invention relates to embossed leather and a process for preparing the same, and more particularly to leather having an enduring pattern embossed on the surface without burning or scorching of such surface, and to a process for imparting at elevated temperatures such enduring pattern to the leather,.which isin particular pretreatment condition.

It is known to produce various decorations and designs on leather by searing techniques or branding techniques. This is especially true in the case of burning identifying initials or symbols into leather saddles, and the like, by the use of red hot irons. Actually, the branding with red hot irons is more amatter of identification than decoration of leather articles, as the searing of the leather is actually not intended for the purpose of embellishing the surface of the leather inasmuch as such surface is merely charred by this brutal treatment. Besides detracting from the ornamental aspects of the leather article and from the beauty of the leather itself, a significant amountof searing or burning in effect greatly impairs the strength characteristics of the leather. Leather hides which have been subjected to such searing or burning techniques cannot be used for shoe uppers as the permeability thereof to water vapor and air is too great. Moreover, the penetrating odor which clings to seared leather for months and even years, is also a great disadvantage. For this reason, the decoration of leather with so-called burning styli, which can be operated manually or by machine, has not acquired any great popularity in the leather industry.

Therefore, other more practical processes have been utilized for decorating leather. Bark-tanned skivers have been pressed between engraved plates having a temperature of about 50 C. in order to cause the pattern from such plates to be impressed upon the surface of the leather. Designs impressed in this manner, however, are not particularly long lasting. When leather treated in this way is folded or rubbed, the surface again becomes smooth. In the language of the trade, the design irons itself out. Furthermore, this impressing of designs at 50 C. is limited to bark-tanned leather (see H. Gnamm, Fachbuch fiir die Lederindustrie, 1958, 5th Ed., p. 488). For this reason, a shoe upper leather loses its decorative design rather rapidly when impressed between engraved plates in the foregoing manner. Significantly, since chrome tanning is predominant today in the leather industry, and since the aforesaid impressing technique is limited to bark tanned leathers, such process is of limited worth, as it cannot be utilized on most of the leathers being currently produced.

It should be noted that leather that is initially soft is only hardened upon being subjected to a pressing process as might be used to impart designs to the leather surface. By way of the teaching in German Patent No. 673,234, such disadvantage is said to be eliminated by first providing napa leather, i.e. suede leather, with a grain pressing of any suitable kind, then disposing the leather upon a soft underlayment which permits the leather to move freely on all sides, and finally ironing the leather from the back side with a very hot plate which is made to slide over the leather surface without great pressure.

This ironing is not to be confused with other prior art hot ironing known by such name and which is done for the purpose of producing a bright or smooth surface on the leather. Such other prior art ironing is carried out such that the leather is prevented from shrinking due to its being held fast on all sides by the firm pressing contact therewith of the ironing plate, such other prior art hot ironing avoiding the use of high temperatures as well, so as not to damage the leather. The same is true with respect to hot pressing, in which the leather is also restricted in its expansion by reason of the use of male and female dies for holding the leather. If desired, the ironing in accordance with the teaching of German Patent No. 673,234, wherein the leather is free to move, can be performed repeatedly, and the same is performed gently so as not to work out the embossed pattern pressed into the leather. The hot treatment of the freely movable leather will cause the previously impressed embossed pattern to draw together, and the leather thus undergoes a puckering, which brings about the drawing together of the napa or suede leather in the manner of an embossed pattern, mainly, but also to some extent in the'manner of a natural graining. The leather is fixed in this condition. The hot ironing can be continued until the desired effect is achieved, but, ofcourse, the leather must not be overheated or it will become stiff and brittle (see German Patent No. 673,234).

In practice, however, it appears that the more lastingly the pattern is imprinted, the stiffer and harder the leather unfortunately becomes.

French Patent No. 1,130,538 discloses a process for the treatment of leather which eliminates the use of presses and other costly machines by laying an asbestos plate having openings therein upon the leather and then playing an open flame over the surface thereof and directly against the leather portions exposed through the asbestos plate openings. However, this process has the same disadvantages as that using a stylus for burning designs into a leather surface, namely bad odor and brittleness, reduced tearing strength, etc.

In US. Patent No. 1,744,553, an alternate technique is set forth contemplating the piercing of leather with sharp punches to about /1 of the leather thickness, such that a design imparted in this manner cannot be ironed out, and such that the leather remains waterproof to some extent inasmuch as the leather is not perforated all the Way through by the punching step. Nevertheless, among the disadvantages of this technique is the fact that fibers of leather will project into the partial perforations and present an unsightly appearance. Such stubborn bristles or fibers can only be removed by using heated punches maintained at a temperature at which the leather fibers will sear but not burn, i.e., approximately 250 C. Such process is difficult to perform because of the normal problems which arise with natural leather. Specifically, although a machine may be adjusted to punch holes or depressions of of a mm. in depth in a leather having a thickness of 1 mm., whereby such leather will be pierced only 4 through, it is well known that the thickness of a raw hide or pelt, and hence of the leather made therefrom by tanning, is anything but uniform. Many points are only 0.5 mm. in thickness, for example, while others are more than 0.7 mm. in thickness. Consequently, the punching needles in some places pierce all the way through the leather, and in others, i.e. the thicker portions, the leather is only scratched and not really pierced significantly at all. The pattern, which is actually nothing more than a hole pattern, is therefore neither ornamental nor attractive in accordance with current-day fashion standards.

Accordingly, up to the present there has been no process by means of which a decoration of leather can be carried out mechanically, e.g. using an embossing machine, which is economical yet without disadvantages of some kind.

It is an object of the present invention to overcome the foregoing drawbacks and to provide a leather having an enduring pattern embossed on the surface thereof With out burning and scorching of such surface, and to provide a. process for imparting such enduring pattern into the leather wherein the leather is in a particular pretreatment condition.

It is another object of the present invention to provide a process of the foregoing type in which the leather is heated at elevated temperatures, yet the design of the embossing tool at the temperature used is only impressed in the surface of the leather but in a permanent manner.

It is a further object of the present invention to provide such a leather which is chrome-tanned grain leather, such as aniline-dyed top grain leather.

Other and further objects of the present invention will become apparent from a study of the within specification and accompanying drawing in which:

FIG. 1 is a perspective view of an apparatus for imparting an enduring pattern into the surface of leather by means of a manually operated heated roller, in the manner of the present invention, and

FIG. 2 is a more or less automatically operated apparatus for imparting an enduring pattern into the surface of leather in the manner of the invention.

It has been found in accordance with the present invention that leather having an enduring pattern embossed on the surface thereof without burning and scorching of such surface may be made by the process which comprises hot impressing a pattern onto a paratfin or wax coated surface of the leather at a temperature between about 200-650 C. The leather surface is preferably hot impressed in smooth, fiat condition, free from Wrinkles and folds. The leather may be aniline-dyed top grain leather which has been chrome-tanned. Preferably, the leather is treated while disposed on an elastic underlayment, and

the hot impressing may be carried out by passing an engraved roller heated to the required temperature into pressing contact with the paraffin coated surface. Advantageously, the leather surface, before the paraffin or wax coating is provided thereon, is treated with a leather dressing that gathers mostly in the strata of the leather close to the surface yet below such surface, whereby to prevent the after-applied paraffin or wax from penetrating substantially into the leather. Such dressing may be in the form of an albuminoid substance.

It will be appreciated by the artisan that decoration by searing or burning is actually possible without damage to grain leathers so long as certain minimum requirements are observed. Firstly, the leather to be decorated should be made by chrome tanning as leathers tanned with natural materials shrink by up to 20% and more in the searing decoration carried out in accordance with the present invention. Ideally, the shrinkage should amount to although this is practically impossible to achieve under normal conditions. Where some shrinking of the leather is not detrimental to the purpose for which the same is to be used, then natural tanned leathers may be employed. Secondly, the leather, such as chrometanned leather, is not to be burned or seared in unprotected condition, but instead such leather must be hotembossed in a particular pretreatment condition, i.e., it must first be sprayed with an aqueous emulsion of parafiin or wax, and the excess paraflin or wax must be removed.

The paraffin or wax emulsion is made in the conventional manner by stirring ordinary parafiins or waxes having a melting point between about 5070 C. in water with an emulsifier being present as well. A thin coating of parafiin or wax thus forms on the surface of the chrome leather, which serves to protect the protein material of the leather beneath such coating from burning.

Still better results are achieved if a leather dressing is used before the application of the protective layer of paraffin or wax, as noted above, with such leather dressing preferably not penetrating too deeply into the leather. It will be realized that the parafiin or wax coating itself does not long remain on the surface of the leather and either the hot impressing step must take place soon after such coating has been added or the prior treatment with the leather dressing of albuminoid substance must be carried out and then the paraffin or wax coating added.

In accordance with the present invention, all paraffins and waxes having a melting point substantially between about 50-70 C. may be used for the desired coating, such as parafiin fractions having a melting point range between about 5065 C., tetracosane (M.P. 51 C.), pentacosane (M.P. 54 C.), beeswax (MP. 60.562 C.), tricon tane (MP. 66 C.), hentricontane (MP. 69 C.), and the like. If the melting point of the paraffin or wax is substantially below 50 C., then the paraffin or wax soaks too deeply into the leather surface, whereas if such melting point is substantially above 70 C., the paraffin or wax is difficult to emulsify.

As emulsifiers which may be used in accordance with the present invention, the following commercially obtainable products are particularly useful:

Emulgator PW, Chemische Werke Hiils of Germany.

Emulgator FOX, Chemische Werke Hills of Germany,

Emulgator GFW, Chemische Werke Hills of Germany.

Emulgin 365, Deutsche Hydrierwerke, Dusseldorf, Germany.

Emulgin 535, Deutsche Hydrierwerke, Dusseldorf, Germany.

Ethomid HT/ 15, Armour 2 Company GmbH, Hamburg,

Germany.

Emulsogen P, Anorgana Gendorf of Germany.

Emulsifier, P.W. Bohme Fettchemie of Germany.

The concentration of the paraffin or wax emulsions used in accordance with the present invention should be substantially between about 5l5%, and preferably 10%, by weight, with the remainder being water. If the concentration of the emulsion is below about 5%, then such small quantities of parafiin or wax are deposited on the leather that the desired effect can no longer take place. Where the concentration of the emulsion is above 15%, the leather takes on a waxy or fatty character and the appearance of the ultimate embossed leather is unattractive. In particular, it has been found that a ratio of parafiin or waxzwaterzemulsifier of 10:88.15 :1.2 is particularly useful in accordance with the present invention. On the other hand, as between the emulsifier and the paraffin or wax, generally the emulsifi-erzparaffi-n or wax ratio may be 0.53:10 or 0.05-0.3z1 in parts by weight. It is not advisable to use a higher ratio of emulsifier to paraflin or wax than that indicated, as an excessive amount of emulsifier is not necessary and too high a concentration of emulsifier may be even detrimental inasmuch as it would represent a proportional decrease in the quantity of paraffin or wax necessary for the intended purpose.

Whereas the aqueous dispersion of the albuminoid, preferably non-thermoplastic substance, may be effectively applied in an amount substantially between 330 grams per square meter and preferably between 3-7 grams per square meter, the aqueous emulsion of the paraffin or wax is generally applied in an amount substantially between about 2-20 grams per square meter and preferably between about 2-5 grams per square meter. Lower amounts of the emulsion should not be used since the singeing and burning away of leather fibers cannot be prevented during the embossing under such conditions, whereas if a greater amount than that specified in the range is used, the leather will take on a fatty appearance and the finished product will have an ob jectionable surface appearance and feel.

As aforesaid, such dressing must work into the strata of the leather close to the surface in order to prevent the paraflin or wax from penetrating much beyond the leather surface, although, on the other hand, the dressing must not itself remain on the surface or this may detract from the value of the paraffin or wax coating. More importantly, a dressing that penetrates too little and thus remains on the surface of the leather produces an unnatural cold feel in the leather. The appearance of the leather then would be more like that of oilcloth. The most unpleasant characteristic, perhaps, is that the dressing, if insufi'iciently adapted to the leather, can be peeled away or the same may crack or flake off by itself. g g

It will be appreciated in accordance with the present invention that the paraffin or Wax coating added to the leather prior to embossing protects the surface from too strong a scorching during the hot embossing, as the leather would break and crack if embossed ,wit-hout the paraffin' or wax pretreatment, and would thus beunsuitable for various purposes, such as leather shoe uppers, and the like. Moreover, the raised portions of the hot-impressed'design in the leather would alsobreak and crack. In the same way, the albuminoid dressing which is applied to the leather after tanning and dyeing but before the paraffin or wax coating, serves to retain the paraflin or Wax at or near the surface of the leather, whereas without prior albuminoid substance treatment of the leather, the parafiin or wax applied thereto would immediately diffuse into the leather and would not remain sufliciently at the outer surface of such leather for the intended purpose.

There may be used in accordance with the present invention, therefore, as dressing or finishing substances which gather for the most part in the strata of the leather close to the surface yet below such surface, in order to prevent after-applied paraffin or wax from penetrating substantially into the leather, various albuminoid substances including albumin, such as egg albumin, blood albumin, and casein, for example from milk, typicallyin the form of acid casein. These substances swell in cold water and is between egg albumin and blood albumin, the former is used for light color leather dressing and the latter is used for dark color leather dressing. Generally, these albuminous substances may be used in 0.5-2%, preferably 1%, aqueous dispersions, and egg albumin, blood albumin and casein may be used alone or in admixture with one another.

In particular, an albuminoid non-thermoplastic dressing agent for leather manufactured under the name Luron Binder by BASF A.G., Ludwigshafen, Germany, has been found to be quite suitable as the dressing substance in accordance with the invention. These agents which act as binders and/ or softeners are albuminoid condensation products in colloidal aqueous dispersion slightly alkaline in nature. The pH of a tenfold diluted aqueous dispersion is about 8.

Generally, the aqueous dispersion of the albuminoid substance may be applied in an amount substantially between about 3-30 g./m. to the leather, whereas the paraflin emulsion may be applied in an amount substantially between about 2-20 g./rn. to the leather.

Actually, the searing or burning must be carried out with a heavy, engraved steel roller which is heated to 200-650 C., preferably 250-400 C., and especially about 350 C., and rolled over the leather just once at a given speed, such as about 7.5 meters per minute, the leather preferably, in turn, being situated upon an elastic underlayment as noted above. Although the line pressure of the roller may be generally 5-10 kilopounds per centimeter, especially 7 kp./cm., there is actually no compacting of the leather being embossed, and thus no effective damage in the thickness or cross-section of the leather.

As used herein, i.e., in the specification and claims,

the term parafiin means both paraflins and waxes which have a melting point substantially between about 50-70 C., and especially those substances whose melting points have been specifically enumerated hereinabove.

Referring to the drawing, FIG. 1 shows the simplest embodiment of the making of leather with an enduring pattern embossed on the surface thereof, without burning and scorching, using a manual arrangement. The roller 1 is connected with a framework 2 which can be moved by the operator so that the roller is displaced back and forth over the leather 3 disposed on a flat surface, table, or the like. The framework 2 is provided with a tray for receiving weights of various amounts, depending upon the type of leather, the degree of embossing, etc. The roller 1 may be heated to ZOO-600 C., or even up to 650 C., and then rolled once over the piece of leather 3 lying on the table. Generally, since the weight of the roller itself is not sufficient in order to transfer the pattern to the leather, the additional pressure required is arrived at by adding one or more weights to the tray of the framework 2. The actual weight to be used can be determined only by trial and error experiments within the purview of the artisan, since different patterns of course requiredifierent pressures, and the artisan will select a particular weight depending upon the degree of embossing desired, i.e.slight, moderate, or vivid. In this regard, if the roller has only a few elevated points which are used to press the desired pattern into the leather surface, only' a slight pressure will be required. On the other hand, where there are many elevated points, the pressure with which these elevated points are pressed into the'leather'will be correspondingly greater. Accordingly, additional weights must be added to the tray of the framework 2. A line pressure of substantially between about 5-10 kilopounds/cm. may be used generally in this connection, and preferably 7 kilopounds/cm., with a speed of relative movement between the leather and the pattern, embossing roller of substantially about 7.5 meters/minute.

In FIG. 2, a preferred more or less automatic arrangement is shown in which a roller 4, which has been brought to the desired temperature by electrical heating or other heating method, is situated stationarily upon an underlayment 9, such that the axis of the roller is at a constant position with respect to the underlayment. Nevertheless, the roller 4 is able to rotate about its axis and this is accomplished as the leather 6 is drawn under the roller in the direction of the arrow in the manner shown. In order that the leather will be always stretched smooth beneath the roller, a friction bar or slide bar 7 is situated in front of the roller such that the leather 6 is pulled over bar 7 so as to raise the same from the underlayment 9 and then the leather passes under the rotating roller 4. It will be appreciated that if the rod 7 is omitted, it is possible that wrinkles in the leather 6 will not smooth themselves out before reaching the roller 4. A wrinkle or crease of this sort in the leather, since it is substantially thicker than the rest of the leather, will be exposed to much stronger pressure, while practically no pressure will be brought to bear on the portions adjacent thereto. As a result, due to the excessively great pressure, the leather at the creases will become brittle, and also will be over-burned, while no pattern at all will be transferred at the other areas of the leather adjacent thereto.

In the embodiment of FIG. 2, the Weight of the roller 4 may be provided so great that the required pressure will be produced under all operating conditions. In many cases, however, the pressure may even be too great. To reduce the weight and accordingly the pressure of the roller on the leather, relieving disc rollers 8 may be provided. By their being pushed together and against the shaft 5 of roller 4, the disc rollers 8 cause the weight of the roller 4 on the leather piece 6 to be relieved in the desired way. Nevertheless, as in the case of the embodiment of FIG. 1, a line pressure of substantially between about 5-10 kilopounds/ cm. may be used generally in this connection, and preferably 7 kilopounds/cm., with a speed of relative movement between the leather and the pattern embossing roller of substantially about 7.5 meters/ minute.

As the artisan will appreciate, it is also possible to carry out the impressing in accordance with the previously described procedure such that the leather is maintained in a constant or fixed position with respect to the underlayment 9, while the roller 4 is rolled over the piece of leather 6 lying on the table or other support.

Significantly, the leather 6 does not rest upon an iron or Wooden platen, but rather an elastic underlayrnent, such as one made from foam rubber or a platen which is covered with leather. Tests have shown that where such elastic underlayment is present, the pattern burned into the leather is longer lasting and better looking than otherwise.

The process of the present invention is applicable to all types of leathers, such as calf skin, cowhide, sheepskin and pigskin, with consistently good results. Such leathers may be treated by conventional chrome-tanning, aftertanning and dyeing techniques [see Handbuch der Gerbereichemie und Lede-rfabrikation, W. Grossmann, publisher Springer, Vienna, 1955, p. 373,,Band 3: Das Leder, Teil 2: Die Lederarten und deren Herstellung (Manual of Tanning Chemistry and Leather Manufacture, vol. 3: The Leather, Part 2: Types of Leather and Their Production) prior to dressing, parafiin or wax coating, and embossing, in accordance with the invention.

The period of time during which the leather must be in contact with the elevated points on the engraved or embossed roller is actually on the order of about 1 second duration. If the leather is pulled through too fast, the desired pattern may not be impressed plainly enough, Whereas if the time of contact is too long, damage may be done to the leather. As the artisan will appreciate, the time of hot impressing the pattern into the parafiin coated leather surface depends upon the temperature, the type of leather, and the type of embossing design utilized, but a speed of relative movement between the leather and roller of 7.5 m./min. is generally sufficient.

Advantageously, the process of the invention may be carried out with aniline-tanned grain leather, since where aniline-tanned grain leather is singed, no destruction of the dye takes place and, therefore, this type of tanned leather is compatible with the hot impressing techniques of the present invention using the paraffin protected coating. Nevertheless, as the artisan will appreciate, many dyes are changed as a result of heat, but this does not necessarily detract from the decorative effect desired, and such leathers Which have been treated with heat changeable dyes may also be hot impressed in accordance with the present invention whereby the changes which take place will add to the decorative effect.

The following examples are set forth by way of illustration and not limitation.

Example 1 Calfskin (butt) leather (average thickness 1.7 mm.) which has been chrome-tanned and thereafter treated by mineral resin synthetic after-tanning, and aniline-dyed, in the conventional manner, is prepared for embossing by applying to the grain side 7 g./m. of a 1% aqueous slightly alkaline colloidal dispersion of a non-thermoplastic albuminoid condensation product (i.e., Luron Binder, BASF A.G., Germany) and then 5 g./m. of an 11.3% aqueous emulsion of a paraflin fraction (M.P. 60 C.) and an emulsifier (Emulgator PW, Chemische Werke Hills, Germany), wherein the ratio of paraflinzwaterzemulsifier is :88.15: 1.2. The so-treated leather is then embossed with a roller having an embossing pattern With 0.8 mm. elevations, and heated to 350 C., in accordance with the arrangement depicted in FIG. 1. The roller is drawn over the leather at a speed of 7.5 meters/min. (0.125 m./sec.), using a line pressure of about 7 kilopounds/cm. The hot embossed parafiin coated leather obtained in accordance with the foregoing possesses permanent designs impressed therein by the embossing which cannot be ironed out, yet which do not represent seared or burned designs in the leather as was the case in the past. Instead, due to the presence of the paraffin coating, the heat of the embossing roller is dissipated in the parafiin or wax sufiiciently to prevent scorching or burning. of the leather grain, yet the heat at the pressure used is sufiicient to impart a permanent and attractive design in the leather. Such leather is free from a scorched or burned odor.

Example 2 Calfskin (neck) leather (average thickness 1.3 mm.) which has been chrome-tanned and thereafter treated by vegetable after-tanning, and aniline-dyed, in the conventional manner, is prepared for embossing by applying to the grain side 3 g./m. of a 1% aqueous slightly alkaline colloidal dispersion of a non-thermoplastic albuminoid condensation product of the same type as used in Example 1, and then by applying 2 g./m. of an 11.3% aqueous emulsion of beeswax (solidification point 60.56 2 C.) and an emulsifier (Emulgin 365, Deutsche Hydrierwerke, Germany), wherein the ratio of wax:water:emulsifier is 10:88.15:1.2. The so-treated leather is then embossed with a roller of the type used in Example 1, which is heated in this case to 300 C. The roller is drawn over the leather under the same conditions as those set forth in Example 1, using a line pressure of about 7 kilopounds/cm., and similar results are obtained.

Example 3 The procedure of Example 1 is repeated, using 20 g./m. of emulsion rather than 5 g./m. as in Example 1, the emulsifier in this instance being that produced by P.W. Bohme Fettchemie, Germany, and similar results are obtained to those obtained in Example 1.

Example 4 Example 1 is repeated except that said embossing is done with a roller according to the arrangement depicted in FIG. 2, wherein the leather is pulled along under the roller at a linear speed of 7.5 m./minute, using a line pressure of about 7 kilopounds/cm. Similar results are obtained in this case to those obtained in Example 1.

Example 5 The procedure of Example 2 is repeated, except that the embossing is done with a roller according to the arrangement depicted in FIG. 2, wherein the leather is pulled along under the roller at a linear speed of 7.5 rn./rninute, using a line pressure of about 7 kilopounds/ cm., and similar results to those of Example 2 are obtained.

Example 6 The procedure of Example 1 is'repeated, using in turn tetracosane, pentacosane, tricontane and hentricontane as the paraffin component of the emulsion with calfskin, cowhide, sheepskin and pigskin, respectively, and similar results are obtained in each instance to those of Example 1.

In each of the foregoing examples, the excess aqueous emulsion is removed prior to contact with the roller by wiping lightly the leather surface, for example with a cloth or Wiping blade, suflicient emulsion being deposited in the leather surface portion to provide the desired protective parafiin coating for the hot embossing step.

It will be realized by the artisan that the foregoing specification and examples have been set forth by way of illustration and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention, which is to be limited only by the scope of the appended claims.

What is claimed is:

1. Process for imparting an enduring pattern into the surface of leather which comprises hot impressing by line pressure contact a pattern onto a parafiin coated leather surface at a temperature between about 200- 650 C., the parafiin of said paraffin coated leather surface having a melting point between about 50-70 C. and

being substantially present on the surface of the leather during the hot impressing.

2. Process according to claim 1 wherein the leather surface is hot impressed in smooth, flat conditions free from wrinkles and folds.

3. Process according to claim 1 wherein the leather is aniline-dyed top grain leather.

4. Process according to claim 1 wherein the leather is chrome-tanned grain leather.

5. Process according to claim 1 wherein the hot in pressing is carried out by passing an engraved roller heated to a temperature between about 200650 C. into pressing contact under a pattern embossing line pressure of substantially between about 5-10 ki-lopounds/cm. with said parafiin coated surface.

6. Process according to claim 5 wherein the leather being treated is provided with an elastic under layment.

7. Process according to claim 5 wherein the leather surface, before the paraflin coating is provided thereon, is treated with a leather dressing that gathers mostly in the strata of the leather close to the surface yet below such surface to prevent the after-applied paraffin from penetrating substantially into the leather.

8. Process for imparting an enduring pattern into the surface of leather which comprises hot impressing a pattern onto a paraffin coated leather surface at a temperature between about 200650 C., the paraffin of said paraffin coated leather surface having a melting point substantially between about 5070 C. and being applied as an aqueous emulsion, said leather surface before the paraffin coating is provided thereon being treated with a leather dressing composed of an aqueous dispersion of an albuminoid substance that gathers mostly in the strata of the leather close to the surface yet below such surface to prevent the after-applied paraflin from penetrating substantially into the leather.

9. Process for imparting an enduring pattern into the surface of leather which comprises hot impressing a pattern onto a paraffin coated, chrome-tanned, aniline-dyed top grain leather surface by passing an engraved roller heated to a temperature between about 200650 C. once over the paraffin coated leather surface in pressing contact therewith under a pattern embossing line pressure of substantially between about 5-10 kilopounds/cm. while the leather is maintained in contact with an elastic under layment in smooth, flat condition free from wrinkles and folds, the parafiin of said paraflin coated leather surface having a melting point substantially between about 50- 70" C. and being present on the surface of the leather during the hot impressing.

10. Process according to claim 9 wherein the roller is in contact with the particular portion of the surface being impressed for substantially only about 1 second.

11. Process for imparting an enduring pattern into the surface of leather which comprises hot impressing a pattern onto a parafiin coated, chrome-tanned, anilinedyed top grain leather surface by passing an engraved roller heated to a temperature between about 200- 650.

C. once over the paraffin coated leather surface in pressing contact therewith so that such roller is in contact with the particular portion of the surface being impressed for'substantially only about 1 second while the leather is maintained in contact with an elastic under layment in smooth, flat condition free from wrinkles and folds, the paraffin of said parafiin coated leather surface having a melting point substantially between about 50-70" C. and the leather surface, before the paraffin coating is provided thereon, being in the form of a pretreated surface which has been pretreated with a leather dressing that gathers mostly in the strata of the leather close to the surface yet below such surface to prevent the after-applied paraffin from penetrating substantially into the leather.

12. Process according to claim 11 wherein said dressing is an aqueous dispersion of a non-thermoplastic albuminoid substance.

13. In the process for imparting an enduring pattern into the surface of leather with a pattern embossing means, the improvement which comprises applying be tween about 3-30 gm./m. of an albuminoid leather dressing that gathers mostly in the strata of the leather close to the surface yet below such surface to prevent after-applied paraffin from penetrating substantially into the leather, then applying between about 2-20 gm./m. of an aqueous emulsion of a paraffin having a melting point substantially between about 50-70 C. with an emulsifier, in a ratio of emulsified2paraffin of between about 0.5-3:10, in a concentration of between about 5-15% in water, onto the surface of a chrome-tanned leather on which the pattern is to be imparted, removing excess paraffin to provide a thin paraffin coating on the leather surface which protects the protein material therebeneath from burning, and hot impressing a pattern onto the parafiin coated surface at a temperature between about 200650 C. for substantially about 1 second.

14. Improvement according to claim 13 wherein the leather isaniline-dyed top grain leather, wherein the aqueous emulsion is in the ratio of paraflinzwaterzemulsifier of about 10:-8=8.15:1.2, wherein a speed of relative movement between the leather and the pattern embossing means of substantially about 7.5 meters per minute is used with a pattern embossing line pressure of substantially between about 5-10 kilopounds/cm., and wherein the leather surface, before the paraffin coating is provided thereon, is treated with a leather dressing in the form of an aqueous dispersion of an albuminoid non-thermoplastic substance.

15. Leather having an enduring pattern embossed on the surface thereof without burning and scorching of such surface which is made by the process which comprises hot impressing by line pressure contact a pattern onto a paraffin coated surface of the leather at a temperature between about 200650 C., the paraffin of said paraflin coated leather surface having a melting point substantially between about 50-70 C. and being substantially present on the surface of the leather during the hot impressing.

16. Leather having an enduring pattern embossed on the surface thereof without burning and scorching of such surface, which is made by the process which comprises hot impressing under a pattern embossing line pressure of substantially between about 5-10 kilopounds/cm. a pattern onto a paraffin coated surface of a chrome-tanned, aniline-dye top grain leather, in which the parafiin of such paraffin coated surface has a melting point substantially between about 50-70 C. and is present on the surface of the leather during the hot impressing at a temperature between about 200650 C. while the leather is maintained in contact with an elastic underlayment in smooth, flat condition free from wrinkles and folds.

17. Leather having an enduring pattern embossed on the surface thereof without burning and scorching of such surface, which is made by the process which comprises hot impressing under a pattern embossing line pressure of substantially between about 5-10 kilo- .pound/cm. a pattern onto a paraffin coated surface of a chrome-tanned, aniline-dyed top grain leather, in which the paraffin of such paraffin coated surface has a melting point substantially between about 5070 C. and is present on the surface of the leather during the hot impressing, at a temperature between about 200650 C. while the leather is maintained in contact with an elastic underlayment in smooth, flat condition free from wrinkles and folds, said surface of the leather prior to being parafiin coated having been treated with a leather dressing of an albuminoid substance that gathers mostly in the strata of the leather close to the surface yet below such 11 12 surface toprevent after-applied parafiin from penetrating OTHER REFERENCES substantlany Into the leather Mudd: Leather Finishes, 2nd Ed., 1955, A. Harvey Publisher, 1955, pp. 76, 78, 79, 115. 1 References Clted by the Examiner Sharphouse: The Leatherworkers Handbook, Nov. UNITED STATES PATENTS 5 1963, Leather Products Association for England, Scotland 1,696,815 12/1928 Small 117-442 and Wales, pp. 5, '136, 140, 141, 167, 168 and 169.

1,700,968 2/1929 Ballou et 2111. Wilson: Modern Practice in Leather Manufacture, 1,704,718 3/1929 Torrance 1 X 1941, Reinhold Pub. Corp, p. 574. I

FOREIGN PATENTS ALFRED L. LEAVITT, Primary Examiner. 664,398 9/1938 Germany.

401,414 11/1933 Great Britain. RALPH N

Claims

1. PROCESS FOR IMPARTING AN ENDURING PATTER INTO THE SURFACE OF LEATHER WHICH COMPRISES HOT IMPRESSING BY LINE PRESSURE CONTACTS A PATTERN ONTO A PARAFFIN COATED LEATHER SURFACE AT A TEMPERATURE BETWEEN ABOUT 200*650*C., THE PARAFFIN OF SAID PARAFFIN COATED LEATHER SURFACE HAVING A MELTING POINT BETWEEN ABOUT 50-70*C. AND BEING SUBSTANTIALLY PRESENT ON THE SURFACE OF THE LEATHER DURING THE HOT IMPRESSING.