US2639967A - Deliming hides with citric acid fermentation liquor - Google Patents

Description

Patented May 26, 1953 DELIMING HIDES WITH CITRIC ACID FERMENTATION LIQUOR Hermann Rudy, Heidelberg, Germany, assignor to Job. A. Benckiser, G. in. b

. H., Chemische Fabrik, Ludwigshafen (Rhine), Germany No Drawing. Application September 19, 1951, Se-

rial No. 247,370. In Germany April 6, 1950 4 Claims.

This invention relates to a process for removing lime and other alkalies, such as sodium sulfide, and to deliming baths and deliming compositions useful therein. More particularly the application relates to deliming processes, deliming baths and deliming compositions utilizing unrefined citric acid.

Up to the present time it has been the customary practice to delime hides or skins which have had their hair removed and their epidermal system separated from the true skin by using alkalies, such as lime and the like, in deliming baths containing acidic deliming agents, for example, inorganic acids, such as hydrochloric acid, sulfuric acid, boric acid, and the like; or organic acids, such as formic acid, acetic acid, lactic acid, 'butyric acid, and the like. This method, however, has the disadvantage that under the action of the acid ions, especially when more deliming agent is present than required, the pelts are greatly swollen whereby the quality of the leather made from the hides is considerably impaired. Such an undesirable effect may be diminished by partially neutralizing the acids with ammonia, but then a comparatively larger quantity of the partially neutralized acid will be necessary to separate the lime.

Ammonium salt deliming agents have also been suggested for deliming hides and skins including ammonium salts of inorganic and organic acids, such for example, as ammonium sulfate, ammo nium lactate, ammonium tartrate, ammonium citrate, and the like. The relatively small deliming effect and the high price of such salts restricts their general use.

Thus, it has been a long standing problem to find a suitable deliming agent which will have a good deliming effect without deteriorating the pelts and which, at the same time, is sufficiently low in price to warrant widespread use.

It is an object of this invention to provide a deliming process, deliming baths and deliming compositions which overcome or greatly alleviate the above mentioned disadvantages. Other objects and advantages of the invention will be apparent from the more detailed following description.

In accordance with this invention it has been found that an unrefined citric acid obtained by the fermentation of carbohydrate compounds with microorganisms, such as molds, show an excellent deliming effect without causing the animal hides to swell and can be produced at relatively low costs. For the purposes of this invention unrefined citric acid produced by fermentation of carbohydrates is to be understood to mean the fermentation liquor produced in the Well known citric acid fermentation process or compositions containing the active ingredients of such liquor. This liquor is also identified by the term citric acid fermentation liquor. It consists of the unrefined citric acid produced by the well known fermentation process and the liquid medium, or citric acid waste fermentation liquor in which the citric acid has been produced by such a process. The process of producing it is described, for instance, in Chemical Activities of Fungi by Jackson W. Foster (Academic Press, New York, 1949) on pages 385 to 386. It is the product of the culturing of a citric acid ferment, such as Asperyillus niger, for a period of days in an acidic molasses medium containing nitrogenous matter and inorganicnutrient salts, and it generally contains about 10 to 15% of citric acid.

While we do not wish to be limited by any theory, it is believed that the advantages of the present invention are due, in part at least, to the fact that the citric acid fermentation liquor has a combined deliming and antiswelling effect. In view of the fact that it is not necessary to neutralize the citric acid content of the citric acid fermentation liquor, only a very small quantity of the liquor per unit of dry material is required. Normally a deliming bath will require only about 1.5% of the citric acid fermentation liquor although concentrations of the order of 0.3% to 2. may be used in such baths. It will also be understood that equivalent quantities of concentrated citric acid fermentation liquor may be used instead of the citric acid fermentation liquor produced in the fermentation process.

In accordance with one embodiment of the invention the citric acid fermentation liquor is mixed with additional Waste fermentation liquors remaining after the citric acid content has been removed from the unrefined fermentation liquor. The added waste fermentation liquors serve not only to dilute the citric acid fermentation liquor but to exert a further complementary action when used in deliming baths. Such waste liquors. may be obtained advantageously by precipitating the citric acid content of a citric acid fermentation liquor as calcium citrate, and then separating the precipitate from the mother liquor thereby leaving the waste fermentation liquor. The fermentation liquor present with produced citric acid, or remaining after the separation of the citric acid content or compositions containing the active ingredients thereof, are referred to herein as citric acid waste fermentation liquor. If desired, the deliming baths having appropriate strength of unrefined citric acid for deliming purposes may be obtained by diluting the unrefined acid entirely with Waste fermentation liquors or by diluting it partially with waste fermentation liquors and partially with conventional" dil'u-nts such as water. The waste fermentation liquors left after the separation of citric acid produced by the fermentation of molasses, such as molasses separated in sugar refining, has proven especially advantageous.

Of course, it will be understood that in the practice of this invention instead of using "unrefined citric acid produced. by thefermentation of carbohydrates corresponding quantities of refined citric acid may be used together with quantitles of citric acid waste fermentation liquors normally present in the unrefined citric acid.

It has also been found advantageous to. produce deliming compositions by diluting and complementing the unrefined citric acid with liquors obtained after the separation of tartaric acid or salts of tartaric acid from their unrefined solutions during the refining process. Tartaric acid may be separated from wine lees, for example, by converting tartaric acid or salts thereof to calcium tartrate, dissociating the calcium tartrate into tartaric acid, and recovering the tartaric acid by crystallization. Such liquors left after the recovery of tartaric acid or compositions containing the active ingredients thereof are called herein tartaric acid waste liquors. The unrefined citric acid may bediluted to a strength suitable for deliming purposes by adding citric acid waste fermentation liquors in combination with citric or tartaric acid waste liquors. When the deliming bath is diluted with either of these waste liquors, and especially when mixed with both types of waste liquors, the deliming composition exerts both a delir'ning'and bating effect.

It is possibIe also to add the unrefined citric acid of this invention to known bating baths, particularly to synthetic leather bates, whereby both a deliming and hating take place.

The unrefined citric acid of this invention may be used, if desired, conjointly with other organic acid deliming agents, for example, lactic acid, acetic acid, tartaric acid, or with deliming ammonium salts, such as ammonium sulfate, ammonium tartrate, ammonium lactate, and ammonium citrate, or with deliming polymeric polyphosphates and the like.

The great economic advantage of using unrefined fermentation liquors compared with the utilization. of known organic acid or organic salt deliming agents produced by fermentation is apparent, as the expense involved in the separation of the active deliming components of such fermentation masses is avoided. The separation of the active deliming components, in accordance with prior art practice, may involve, for example, (1) the production of the calcium salt (2) the decomposition of the calcium salt by sulfuric acid and (3) crystallization and separation of the pure acid. When the unrefined citric acid is used, as in this invention, all such additional expenses are avoided.

It is surprising that the fermentation liquors, including the citric acid, can be used without further refinement as deliming agents, for it is known that calcium citrate is a very slightly soluble salt. Thus it would be expected that the reaction of the unrefined citric acid with calcium compoundsas in deliming, would result in the formation of a very slightly soluble precipitate '4 which would be formed in the hide, resulting in leather damage, as is true when such salts are formed in tanning operations. This surprising result may be attributed to unknown attributes of the fermentation liquors associated with the citric acid.

In accordance with the present invention, therefore, very satisfactory deliming agents are provided at an acceptably low price while agents heretofore known were either too costly or unsatisfactory.

The following examples further illustrate the practice of-the invention.

Example 1 Goat skins were soaked and washed in a cask for ashort time after liming. The goat skins were then introduced into a deliming bath containing1.5% of an unrefined citric acid. The unrefined citric acid constituted a fermented liquor containing 15% citric acid. Deliming took place very quickly. The pelts had an especially smooth feel, and the glazed kid made therefrom had an especially fine grain.

Example 2 A calf skin limed and washed as usual was introduced into a solution containing 10 grams of unrefined citric acid and 3 grams of ammonium sulfate per liter and it was delimed in the solution until a sample of the pelt was free of lime. The process took nearly an hour. Then the skin was bated and worked up to box calf in the usual manner. The resulting leather showed an especially fine and smooth grain.

Example 3 An unrefined citric acid was produced by fermenting a carbohydrate with Aspergillus niger and 10 parts thereof were diluted with parts of citric acid waste fermentation liquors obtained in the production of refined citric acid. The resulting solution formed a superior deliming bath for cow hides being processed for sole leather. During the deliming operation additional unrefined citric acid was added to maintain its concentration in the bath at about 2%.

While the practice of the invention has been exemplified hereinbefore by reference to various details and examples, it will be understood that these may be varied widely and substituted by equivalents without departing from the substance of the invention as herein disclosed and claimed.

What is claimed is:

1. A process for deliming hides and skins which comprises contacting the hides in the limed condition with a solution containing approximately 0.3% to 2.0% of citric acid fermentation liquor.

2. A process for deliming hides and skins which comprises contacting the hides in the limed condition with a solution containing approximately 0.3% to 2.0% of citric acid fermentation liquor for a period of the order of one hour.

3. A process for deliming hides and skins which comprises contacting the hides in the limed condition with a solution containing approximately 0.3% to 2.0% of citric acid fermentation liquor produced by the fermentation of molasses, said liquor containing about 15% of citric acid.

4. A process for deliming hides and skins which comprises contacting the hides in the limed condition with a solution containing approximately 0.3% to 2.0%01? a commercial citricacid fermen 6 tation liquor and a lesser quantity of ammonium Number Name Date sulfate. 1,772,258 Le Petit Aug. 5, 1930 HERMANN RUDY. 2,132,579 Rohm Oct. 11, 1938 References Cited in the file of this patent 5 N b EOREIGl: PATENTS t um er Coun ry Da. e UNITED STATES PATENTS 1,049 Great Britain 1852 Number Name Date 5,620 Great Britain of 1893 y g 59% 12;: 266,414 Great Britain of 1926 e mer *e 873,074 Nowak Dec. 10, 1907 OTHER REFERENCES 996,509 Nowak June 27, 1911 Basu et ails-abstract in Journal Int. Soc. Lea. 1,570,383 McCandish Jan. 19, 1926 Trades Chem. March 1948, page 109.

1,679,186 Szucs July 31, 1928

Claims (1)

1. A PROCESS FOR DELIMING HIDES AND SKINS WHICH COMPRISES CONTACTING THE HIDES IN THE LIMED CONDITION WITH A SOLUTION CONTAINING APPROXIMATELY 0.3% TO 2.0% OF CITRIC ACID FERMENTATION LIQUOR.