CA1207107A - Method for reversibly preserving hides - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A process for reversibly preserving hides or skins by treating said hides or skins with an aqueous solution of aluminum ions and thereafter adjusting the pH of said contacted hides or skins and solution to from about 3 to about 5.

Description

~;~()7~07 ~ESCRIPTION
METHOD FOR REVERSIBLY PRESERVING HIDES
BACKGROUND OF THE INVENTION
1. Field o~ Art This invention relates to a process for reversibly pr2serving hides for tanning or retanning at some sub-sequent period of time. More particularly, this inven-tion relates to such process in which the hides are reversibly preserved through use oE aluminum salts.

2. Background of the Prior Art:
The problems of preserving hides and skins for transportation and storage have been the subject of study for a very long time, and various processes have been developed. Generally, conventional processes or preserving hides and skins utilize s~me readily available local resource. For instance, in North America the hides and skins, ater flaying are most commonly preserved by impregnating them with salt (sodium chloride~ which is readily available. In tropical countries, the hides or skins may be dried or impregnated with some low grade tanning material, such as myrabolans and avaram bark, materials which are also locally available. After such preservation, the hides or skins may be transported or stored for commercial purposes and are usually further processed by tanners and/or leather dressers into leather suitable for such articles as for example shoes, garments, bags, cases, straps and the like.
There are several disadvantages associated with the : `:

" :120~0~7 presently used methods for preserving hides and skins.
For example, salted hides are subject to putrification in moist, warm conditions and often arrive at their des-tination in poor condition. Accurate weight, value and quali~y determinations are difficult because o~ their varying water, fat, flesh and hair content, and in pres-ent times, this is a significant commercial disadvantage which has contributed to the growth of the blue side industry. The disadvantayes of dried raw stock are well documented and the difficulty of restoring the hide or skin to its original condition has been the subject o-f much study. Similarly rough tanned or partially tanned skins as well as chrome tanned blued hides and skins have limited reversibility and, therefore, suffer in their use and product characteristics. Other disadvan-tages which are catalogue~ in Shuttleworth, S.G. in the Atkins Memorial Lecture, September 1972 delivered to the Annual Conference of the Society of Leather Trades Chemists r entitled "Future Developments in heather Manu-facture", "are that in the present systems waste, as forexample hair and flesh, is transpor~ed along with the hide which increases transportation cost, and that environmental problems, as for example salt contamina-tion, are associated with these currently used p~eserva-tive t~chniques. In addition, the tanner who buys thesehides has a very poor idea oE the quality oE the useable surface that will become his piece of leather, because it is masked by the attached hair and flesh, which results in an inability to accurately grad~ raw material in order to exercise more specialization and more accu-rate cost production".
Several e~forts have been made to improve hide and skin preservation both from the technical and commercial perspective. For example, in Barlow, J.R. and Leach, I., "The Use of Alum to Preserve Partially Processed Hides and Skins", TropicaI Science, Vol. 22(1), pp.
69-76, (1980) discloses a proeess intended to obviate one or more of these disadvantages. In this process, ; ,;

~ZCi~07 . .
--3~
the brined, lime split hides are contacted with 10% dry potassium alum or aqueous potassium alum, aEter which the pH of the hides are adj~sted to between 2.8 and 3Ø The publication indicates that after this treat-S ment, the hides are dried and stored or transported toother locations, the potassium alum can be washed out prior to later processing, having no adverse effects on the properties of the leather. There are several disad-vantages which are inherent in this process. For exam-ple, the amount of potassium alum used in processing thehides is less than 1.0 weight percent (expressed as A12O3 by weight) which is too low to properly preserve the hides for wet storage and transportation.
Consequently, the hides must be dried to provide adequate preservation which results in increased processing cost, steps and time. Furthermore, the low potassiu~l alum content coupled with the ~ide pH at the end of the hide processing results in hides having too little substance to withstand the rigors of splitting, shaving and like mechanical treatments~
~ hrome is the preferred commercial tanning agent, but there are several disadvantages relat~d to its use. In a typical chrome-tanning processl the raw, pickled hide is treated mechanically and chemically to prepare it for tanning, such treatments include dehair-ing and defleshing. A~ter trea~men~ the hide is tanned with a chrome tanning a~ent, usually basic chromic sulfate. The tanning operation is inefficient and from 20% to 30% of the offered chrome is unused at the end of the tanning process. After tanning, the hide is graded for its end use, leveled to a uniform caliper and ~he undesirable parts trimmed. In this leveling and trimming operation, from 20 to 30% of the offered chrome may be discarded as solid waste. Thus, in some commercial chrome tanning operations, between 40~ and 60% of the offered chrome is wasted. This inefEicient use of chrome is extremely disadvantageous in that the cost of chromium is high, and we are completely 7~07 dependent on foreign sources for chromium ore. The large amount o~ chrome containing wastes that are generated also present a substantial environmental problem to the industry.
The entire leather industry is quite alert today to the inef~iciency problems associated with leather tan-ning, and the added cost of operations which must neces-sarily result, as well as to the effluent problems and to the consequences of disposing of chrome containing liquid and solid waste products. Chromium recovery or recycling has been offered as a solution, however, such recovery or recycling of the spent chrome is not always as effective as desired. It involves large investments and requires thorough technical supervision and process control in order to guarantee uniform leather quality from pack to pack.
In recent years, tanneries, leather institutes and the like have been engaged in intensive research programs to ~ind a new, practical method of tanning leather in which the use of chrome in tanning is minimized, and chrome uptake during tanning is maximized, while at the same time not affecting the character of the leather which is achieved by conventional chro~e tanning. One process in which the use of chrome is minimi~ed is disclosed in U.S. Patent No. 4,060,384. In that process, raw hides and skins are pre-tanned with a chromium free tan, as ~or example organic syntans, to adjust the shrinkage temperature to from 170F to 185F, after which the hide and skin can 3n be subjected to the various mechanical operations, as Eor example splitting and shaving, followed by t~nning with ~arious tanning agents, such as chrome, into leather. The patent teaches that the hide can be pickled or salted before, during or after pre-tanning, that such pickling with or without the pre-tanning places the hides in condition ~or shipment to remote geographic locations requiring man~ weeks in route without damage of material deterioration.

7~07 Many studies ~ave examined the use of aluminum salts as tanning materials and pickling salts. Such aluminum salts have found applications in such areas as fur dresslng, and baseball leathers where the character-istics imparted by aluminum salts offer some specificbenefits.
The major disadvantages of aluminum salts in tanning are the ease of reversibility of the tannage, and the problems of fat-liquoring the tanned pelt.
These problems are very well described by McLauyhlin, G.D.I and Th~is, F.R. in "The Chemistry of Leather Manufacture", Reinhold Publishing Corporation, Chapter 20, and in Great Britain Patent No. 1,471,747 in which basic aluminum chloride is used as a pre-tannage to be followed by chrome or vegetable tanning to enhance certain leather charac~eristics and to achieve high chromium utilization.
In all of these previously described processes, there has been overlooked the opportunity to process hides and skins in a manner substantially similar to the production of chrome tanned hides and skins, and having substantially all the benefits oE blue sides and yet not withstanding the ease and simplicity of the process offering the benefits of ease of handling, transporta-tion, gradation, machinability, etc. and yet oEferingthe benefits of reversibility.
SUMMARY OF THE INVENTION
In accordance with this invention there is provided a method of reversibly preserving hides Eor preservation purposes, which method comprises the steps of:
(a) contacting said hides with a reversible pre-servative comprising an aqueous solution of at least about 1.0 weight percent aluminum ions (Al+3) ~expressed as percent A12O3 by weight) based on the raw weight of the hide for a time sufficient for said hides to absorb a reversible preserving effectiv2 amount of said ions and to distribute said ions throughout said hide in a substantially uniform fashion; and ~ ~2~7~07 (b) adjusting the pH o~ said contacted composition and hides to a value of from about 3 to about 5.
After subjection to the process of this invention, the hide can be graded, leveled, trimmed and dried without generating chrome containing waste or substan~
tially small amounts thereof as compared to prior art processes. A-fterwhich, the hide can be either tanned with a conventional tanning agent, such as chrome, wast-ing less than 5% of the chrome, or can be stored for long periods of time, or shipped long distances without deterioration, and thereafter subjected to mechanical processing and/or tanning.
Several advantages flow from the process of this invention, which are as follows:
(a) Improved selectivity of hides prior to the tannage, thus providing greater flexibility in the production of leather.
(b) Reduced transportation cost of untanned hides because oE removal of unuseable portions of the hide, such as hair, flesh, salt and water.
(c) Optimum use of conventional tanning agents, such as chrome, in the tanning process, reducing the ~uantity of such agents required to provide an accept-able product, thereby reducing the cost of tanning, and the quantity of wastes generated.
(d) Gen~ration of useable b~-products such as protein for glue, gelatin, fertilizer, and like products, DESCRIPTION OF THE PREFERRED EMB~DIMENTS
In the first step of the m~thod of this invention, the raw hide or a hide which has been preferably bated and/or delimed in accordance with conventional techni-ques is contacted with a reversible preservative com-prising an aqueous solution containing at least about 1 weight percent aluminum ions (Al+3) ( expressed as percent A12O3 by weight~ based on the raw weight of the hide. As used herein, the term "hide" refers to the pelt of both large animals such as cows, deer, buffalo, ~ ~IZ~'7~07 horses, and the like, and the pelts of smaller animals such as sheep, goats, seals, pigs, reptiles, and calves, and "raw weight" as used herein is the weight of the hide after removal from the animal's back and soaking in water. In the preferred embodiments of the invention, the amount of aluminum ions (Al+3) in the composition is from about 1 to about 4 weight percent (expressed as %
A12O3) based on the raw weight of the hide, and in the particularly preferred embodiments of the invention the amount of aluminum ions (Al+3) in the composition is from about 1.5 to about 2.5 weight percent on the same basis. Most preferred are those embodiments of the invention in which the amount of aluminum ions (Al+3) in the composition is from about 2 to about 2.25 weight percent on the aforementioned basis.
The aluminum ion (Al+3) content of t~e reversible preserving composition can be derived from such sources of aluminum ions known to those of skill in the tanning art. Aluminum chloride and aluminum sulfate, Al2(SO4)3, or its various hydrated forms, such as Al2(SO~)3'~ H~O
(wherein "X" is a whole or fractional number) or basic forms as for example Al(OH)(SO4) are the preferred sources of aluminum ion ~Al+3) for use in the process of this invention, and alumi~um sulfate in its various forms is particularly preferred for use. Aluminum sulfate is water soluble and is usually in the form of white lustrous crystals, granules or powder. The specific gravity of A12(SO4)3-l8 H2O is 1.62 and the specific gravity of Al2(SO4)3 is ~.672, each measured at 22.5C. Aluminum sulfate can be obtained from commer-cial sources, as for example Allied Corporation, or prepared in accordance with conventional preparative techniques. For example, aluminum sulfate can be con-veniently prepared by treating aluminum hydroxide with sulphuric acid and crystallizing out the aluminum sul-fate. Similarly, aluminum sulfate can be prepared by treating kaolin a natural clay with sulphuric acid.
Silicic acid is precipitated and filtered, and aluminum ~2~07 sulfate crystallized out of the filtrate. Aluminum chloride can be prepared by contacting molten aluminum metal with chlorine gas.
The reversible preservative may optionally include other ingredients. For example, in the preferred embodiments of the invention, the tannage will include one or more water soluble monobasic or polybasic aliphatic or aromatic carboxylic or sulfonic acids, or salts thereof. Illustrative of such acids are formic acid, acetic acid, adipic acid, naphthalene sulphonic acid, benzoic acid, phthalic acid and the likeO
Substituted acids and their salts, as for example dichlorophthalic acids, tetrachlorophthalic acids, 2,4-dichlorobenzoic acid, 5-chloro-2-hydroxybenzoic acid can be used in the process of this invention. Particularly preferred for use in the practice of the invention are lower molecular weight fatty acids as for example formic, gluconic, acetic, citric and propanoic acids, as well as aromatic polycarboxylic acids as for example, phthalic acid, and halo substituted phthalic acid. The reversible preservative may also include other ingredients which indicate the extent and the uniformity to which the preservative is absorbed throughout the hide. Illustrative of the preferred ingredients for performing this function are ferric salts, such as the sulfate and ferric chloride.
In general, the temperature at which the hides and the reversible preservative are contacted is not criti-cal. The temperature must not be so high as to damage the hides, and must be low enough for all essential ingredients to remain in solution so that they may be absorbed by the hide. Usually the temperature will range from about 0C to about 75C. In the preferred embodiments~ the contacting temperature will range from about 10C to about 50C, and in the particularly preferred embodiments of the invention the contacting will be carried out essentially at ambient or ~oom temperature, i.e. from about 2~C to about 30C.
:

-- ~26)~1~7 The hides and reversible tannage preservatives are contacted for a time sufficient for the hide to absorb a "reversible preserving amount" of the aluminum ions (Al+3) and to distribute such ions throughout the hide in a substantially uniform fashion. As used herein, a "reversible preserving amount" of the hide preservative is an amount sufficient to increase the preservation of the raw hide to any extent. The amount of aluminum ions (A1~3) absorbed in the hide is usually at least about 2 weight percent (expressed as % A12O3 by weight) based on the weight of the hide dried to a constant weight. In the preferred embodiments of the invention, the amount of aluminum ions (Al+3) is from about 2 to about 6 weight percent on the aforementioned basis, and in the particularly preferred embodiments is from about 3 to about 5 weight percent on the same basis. Amongst these particularly preferred embodiments, most preferred are those em~odiments in which the amount of aluminum ions (Al+3) absorbed ~y the hide is from about 3.5 to about 4.5 weight percent on the aforementioned basis. Contact times are not critical and can be varied widely depending on the degree of preserving desired. In gen-eral, the longer ~he contact times, the greater the amount of aluminum ions (Al+3) absorbed by the hide and ~he greater the degree of preservation. Converselyl the shorter the duration of the contact times, the lesser the amount of aluminunl ions ~Al+3) absorbed by the hide and the lesser the degree of preservation. Usually, contact times of fro~ about 30 minutes to about 8 or g hours will be employed, depending of course on such fac~ors as the calipher of the hide, temperature and the concentration of aluminum ions in the reversible pre-servative. In the preferred embodiments of the inven-tion, contact times will vary frorn about 1 hour to about 5 hours, and in the particularly preferred embodiments will vary from about 2 hours to about 4 hours.
~ n the second essential step of the process of this invention, the pH of the contacted hide and reversible ~2~7~07 " ~.~

preservative combination is adjusted to from about 3 to about 5. It has been discovered that the final p~I of the hide as it emerges from the adjusting step is critical for attainment of the advantages of this invention. In the preferred embodiments of this invention, the pH is adjusted to from about 3.5 to about 5, and in the particularly pre~erred embodiments the pH
is adjusted to from about 3.7 to about 4.5.
The pH can be adjusted by any conventional means which does not adversely affect the hide, or the leather prepared therefrom. During contact, the pH of the reversible preservation and hide is usually lower than about 3, and the pH can be increased most conveniently by addition of one or more basic materials, as for example, sodium formate, sodium acetate, magnesium oxide, sodium hydroxide, sodium carbonate, sodium sesquicarbonate, sodiu~ bicarbonate, lime or the like in an amount suf~icient to raise the pH to the desired level.
After treatment of the hide in accordance with the two essential steps of the process of this invention, the treated hide is reversibly preserved and is resistant to deterioration~ For e~ample, the hide can be dried and stored as is for e~tended periods of time, or transported long distances without danger of material deterioration. Alternatively, the treated hides can be shaved and/o~ split in accordance with well known techniques and these shaved and/or split hides can be either stored for long periods of time or transported long distances in a relatively preserved state~ These shaved and/or split hides can be tanned as is without removal of the reversible preservative, or can be treated to remove the aluminum ions thereby restoring the hide to its previous state. Thereafter the hide can be tanned in accordance with conventional tanning techniques. In the preferred embodiments of this invention, hides preserved in accordance with the process of this invention are chrome tanned, because of - ~2~7~07 beneficial effects on chrome uptake by the hide during the tanning step~
The following specific examples are presented to more particularly illustrate the invention.
Example 1 Various experiments were conducted to illustrate the advantages of this invention. The experimental details and results are as follows:
Step 1 - Pickling Bated hides are washed thoroughly in running water to rid the hides of any residual substances. In pickl-ing, the hides are readied for the penetration of the alum-based curing agent by acidifying with sulfuric acid in the presence of 8 Baume salt solution (8.25~ sodium chloride~. At the end of the pickling operation, the salt concentration is 6 9 Baume and the pH is less than

3.
Step II - Aluminum Sulfate Reversible Preservation The hides are impregnated with selected amounts o~
the aluminum sulfate-based preserving agent by floating the hides in a tanning drum containing the hides and an aqueous aluminum sulfate solution. The agent is allowed to penetrate for two to four hours.
After drumming, the pH is slowly increased to from

4.0 to 4.5 by addition of sodium bicarbonate. Ater addition of the sodium bicarbonate, the hides are rotated in the drum Eor abou~ 90 minutes. The hides are then removed from the drum and used in the following Step III.
Step II~ - Wringing E~cess moisture is removed from the hide for proper handling on a splitting machine. The excess moisture is removed by passing the hide through a conventional wringer.
Step IV - Splitting and Shaving The hides are then mechanically split to yield a "grain" portion and the flesh layer which may be used for sueded leathers.

12C~7~L07 Step V - Chrome Tanning The split, shaved and aluminum sulEate preserved hides are now chrome tanned. In the tanning step, the hides are 1Oated in the tanning d-rum in water and impregnated with a chrome tanning agent (2% Cr2O3 offering based on the weight of the split/shaved hide). The chrome tanning agent is allowed to penetrate the hide for from 30 to 90 minutes. The pH is then increased slowly from 3.5 to above 4.5 by addition of sodium sesquicarbonate. The hides are now tanned and ready to be dyed, fat liquored, dried and conditioned according to standard practices.
Step VI - Hide and Process of Preservation Process efficiency and hide characteristics were evaluated. Chromium content (expressed as % Cr2O3 by weight) was determined by ASTM Designation D2807-69T.
Chromium uptake was determined by analysis ~f the solution remaining in the tanning bath by ALCA
Provisional C-l June 1965. Tensile strength of the tanned hide was measured by ASTM Designation D2209-64.
Stitch Tear of the hide was measured by the ALCA
Provisional method E-13, April 1953.
All shrinkage temperatures were measured at difer-ent stages of tanning with a Theis apparatus. The shrinkage temperature is a convenient measure oE the cohesive forces of the hide collagen fibers, or of the degree of tannage. It is the temperature at which nota-ble shrinkage occurs when a sample o hide is heated gradually in an aqueous medium.
The results of the hide and process evaluation are set forth in the following Table I.

:

~2~7~07 Table I
Cr203 Content (%)........... ~.. .o........ ~ . 3.4 Cr O
Up~a~e %~O~ O~ 96.3

5 Shrinkage Temperature (C),.............................. 98 Tensile Strength (psi)............ ~........................... 1507 Stitch Tear (lbs)........................................ 21 Example 2 Several experiments were conducted to illustrate the criticality of the amount of aluminum (expressed as % A12O3 by weight) in the reversible preservative for optimization of shrinkage temperature and weight gain in the preserved hide. The procedures employed in these experiments are as follo~ed in Example 1, and the results are set forth in the following Table II.
Table II
A12O3 Offering (% Basis Hide Wt) 1 2 2.5 3 4 Shrinkage Temperature ~C) 74 75 ~6 74 74 Weight Gain After Reversible Preservation (% Basis Hide Wt)0 10 20 15 13 Exàmple 3 Employing the procedure of Example 1, a bated hide was reversibly preserved with an aqueous solution of 2.5~ Aluminum Sulfate ~expres.sed as % A12O3 by weight) on a raw hide weight basis, followed by tanning with a tanning agent containing 2~ Chromium (expressed as %
Cr2O3 by weight) on a shaved hide weight basis. The physical chara~teristics of the hide after treatment are set forth in the following Table III.

12~7~07 TABLE III
Cr203 Content %..................................... 3.26 Tensile Strength.............................. 1724 Stitch Tear 5 (lbs~.......................................... 24 Shrinkage Temperature ~C~.......................................... 100+
Example 4 Employing the procedure of Example 3, a bated hide was reversibly preserved with an aqeuous solution con-taining 2.5% aluminum sulfate (expressed as % A12O3, by weight) on a raw hide weight basis and sodium acetate (0.125 moles per mole A12Q3), followed by tanning with a chrome tanning agent (2~ Cr2Q3 by weight on a raw hide basis~. The physical characteristics of the hide are set forth in the following Table IV.
TABLE I~
Experimental Leather Cr2O3 Content (%)..................... ~............. 3.1 Tensile Strength (psi~......................................... 2990 Shrinkage Temperature (C).......................................... 100 Example 5 A series of expe~iments were carried out to eval-uate the relative effectiveness of the process of this invention and prior art processes. Both the experi-mental and the control processes began with about 3000pounds unsalted raw hides. These hides were prepared for curing and tanning according to a conventional method. One half of the hides were processed according to the experimental hide process as described in the Example 1, and the other half according to the conventional method.
The conventional method was as follows:

~%~ 7 Step I - Pickling Bated hides are washed thoroughly and drained in the tanning vessel. The hides are acidified with 2%
(raw hide weight basis) sulfuric acid in the presence of 8 Baume salt solution. The resulting p~ of the solu-tion will be about 1.7 and the salt concentration 6-8 Baume.
Step II - Chrome Tanning The pickled hides are impregnated with the desired amount of chrome tanning agent l1.4% Cr2O3 raw hide weight basis) which is allowed to penetrate for 3 hours.
The pH of the tanning solution is increased slowly with magnesium oxide to 3.8. The tanning vessel then rotates for 7 hours. A neutral synthetic tanning agent is added to remove any residual greases. The tanned hides are washed, wrung, leveled, dyed, fat liquored, dried and conditioned.
Selected criteria were evaluated and the results set forth in Tables V and VI. The chrome uptake of the experimental process was far more efficient than that of the control process, and more chrome was fixed in the leather. Furthermore, the substance of the experimental leather were greater than that of the control leather.
The experimental leather produced was comparable to the control leather and was within the commercial require-ments of the product in the areas of thermal stability and yield. The experimental leather is n~t quite as strong as the control le~ther, but is well within commerclal requirements.

~7~L07 Table V
Chrome Tanned Control LeatherExperimental Leather % Cr2o3 Uptake 5 in Tanning 74 97 % A12O3 Uptake in Preservation - 67 % Cr20 in ~ea~her 3~56 4.13 % M O3 10 in ~eather 3.56 6O9 Table VI

Control Chrome Tanned Leather Experimental Leather Shrinkage 15 Temperature ( C) 100 99 Tensile S~ Ul (psi) 3378 2563 Stitch Tear (lbs) 53 45 20 S~s~dn~ (OZ) 3 0 Yield - Area (sq ft/side~ 21.7 21.3 Yield - Weight (lbs/side) 4.2 4.5 Example 6 A series of experiments were carried out to evaluate the relative effectiveness oE the process of this invention and a known commercial tanning pr~cess.
Both the experimental and the conventional process began with about 300 pounds of salted raw ~ides. A portion of the hides were processed in accordance with the commer-cial procedure, and portion were processed in accordance with the experimental procedure.
The experimental method was as follows:
Step I - Pickling Rated hides are washed thoroughly and drained in the tanning vessel. The hides are acidified with 1.5~
(raw hide weight basis) sulfuric acid in the presence of 8 Baume salt solution. The resulting pH of the ' .1..

-`" 12~7~07 solution was 1.6 and the salt concentration 8 Baume.
Step II - Preservation The pickled hides were impregnated with the desired amount of aluminum ions by floating the hides in a tanning drum containing the hides and an aqueous solution containing 2.25% aluminum sulfate (expressed as % A12O3 by weight) based on the weight of the raw hide. The aluminum was allowed to penetrate for 3 hours.
The pH of the preservation solution was increased slowly to 4.0 by addition of sodium carbonate, after which the tanning vessel was then rotated for 2 hours.
The preserved hides were wrung, leveled, and tanned, The tanned hides were then dyed, fatliquored and dried.
Selected properties of the hides tanned in accordance with the commercial process, and those tanned in accordance with the experiment process were evaluated, and the results set forth in Table VII and VIII below.
Table VII

Commercial Chrcne Tanned Leather Experimental Leath~r 25 % Cr O3 Uptake in la2nning % A12O3 Uptake - 95 in Preservation % Cr2O
in Leather 3.4 3.5 in Leather 3.4 4.4 , Table VIII

Cbntrol Chrame T~nned Leather Experimental`Leathèr 5 Shrinkage l~mpe- dL~ 00+ 100 (C) Tensile 3421 3299 Strength (psi) Stitch Iear (lbs) 16.5 15.5 10 Substance (kg) 6.5 6.5 .

Claims (10)

WHAT IS CLAIMED IS:

1. A method of reversibly preserving a hide which comprises:
(a) contacting said hide with an aqueous solu-tion comprising at least about 1 weight percent aluminum ions (Al+3) (expressed as percent Al2O3 by weight) based on the raw weight of the hide for a time sufficient for said hide to absorb a reversible preserving effective amount of said ions and to distribute said ions through-out said hide in a substantially uniform manner; and (b) adjusting the pH of said contacted hide and solution to from about 3 to about 5.

2. A method according to claim 1 which further comprises removing said hide from said solution, and leveling said preserved hide to give it a substantially uniformed caliper.

3. A method according to claim 2 wherein said aluminum ions (Al+3) are derived from aluminum sulfate.

4. A method according to claim 2 which further comprises tanning said leveled preserved hide.

5. A process of shipping a hide from one geo-graphical location to another geographical location which comprises contacting said hide with a reversible preservative comprising an aqueous solution of at least about 1 percent of aluminum ions (Al+3) (expressed as %
Al2O3 by weight) based on the raw weight of the hide for a time sufficient for said hide to absorb a reversible preserving effective amount of said ions and to distri-bute said ions throughout said hide in a substantially uniform manner; adjusting the pH of said contacted hide and preservative to from about 3 to about 5; removing said hide from said preservative; and shipping said preserved hide from one geographical location to another.

6. A reversibly preserved hide which is rever-sibly preserved in accordance with the process of claim 1.

7. A hide which is tanned in accordance with the process of claim 4.

8. A method according to claim 1 wherein the weight percent of said aluminum ions (Al+3) in said solution is from about 1 to about 4.

9. A method according to claim 8 wherein said weight percent is from about 1.5 to about 2.5.

10. A method according to claim 1 wherein said pH is adjusted to from about 3 to about 5.