US1429851A

US1429851A - Tanning process

Info

Publication number: US1429851A
Application number: US456198A
Authority: US
Inventors: Dufour Lorenzo; Dufour Gustavo
Original assignee: Individual
Current assignee: Individual
Priority date: 1921-03-28
Filing date: 1921-03-28
Publication date: 1922-09-19
Anticipated expiration: 1939-09-19

Description

i atezniteril @ept. 19, 1922.

FATENT LORENZO DUFOUR AND GUSTAVO DUFOUR, OF GENOA, ITALY.

TANNING PROCESS.

N0 Drawing.

Application filed March 28, 1921. Serial no. 456,198.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. In, 1313.) I

To all whom it may concern:

Be it known that we; Lorenzo DUroUR and Giis'invo DUroUn, both subjects of the King of Italy, and residents of Genoa, in the Kingdom of Italy, have invented certain new and useful Improvements in Tanning Processes (for which applications for patent have been filed as follows: in Italy April 6, 1918, Patent No. 165,824, dated July 18, 1919; France, filed January 31, 1919, Ser. No. 108,210; Spain, filed February 17, 1919; and Great Britain, filed Mlarch 1, 1919, No. 5,124); and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

It is well known that sulphurous an hydride (sulphur dioxide) and its salts have a very useful effect as energetic reducing agents and are therefore very eflicacious in preventing the oxidation of tanning liquors and consequently keeping those liquors clear, with the avoidance of loss of tanning matters.

That beneficial action is all the more nec essary when the tanning is done in open vessels, with the result that the tanning liquors are more exposed to oxidation and become muddy.

Although the above mentioned action of sulphurous anhydride in the tanning of skins has been known for a long time past, as is said above, there is no evidence that sulphurous anhydride has been employed in. the gaseous state; and its use in that state forms the subject of the presentinvention. As a matter of fact, up to the present, sulphurous anhydride has been used for the treatment of tanning extracts and of skins, in the form of bisulphite of soda, with the object both of decolorizing the extract and of preparing the skins for tanning.

The new system that forms the subject of this application, and with which very good results are obtained, consists in the direct use of sulphurous gas (S0 produced by the combustion of sulphur or by any other method of preparation. The gas is caused to enter the water in the vats in which the skins are suspended, the liquid in those vats being maintained in rapid circulation, in the known manner. Otherwise the gas is introduced into and released in the water in the tubs, by a tube following the axial line of the tubs.

In order to prepare the skins for tanning and to eliminate the lime completely, instead of employing organic acids or mineral acids, which are difficult to use and which are very often injurious to the skins, the hides are suspended in vats containing water at a temperature of 30 to 35 degrees C. The water is caused to circulate rapidly and there is introduced into it by means of an air compressor a current of sulphurous gas produced in a furnace in which sulphur is burned.

At the same time one may add to those vats some tanning liquors, taken from the excess in the tanningvats in order to utilize those liquors fully at the same time as the lime is eliminated from the skins. In that way we secure a complete utilization of the tanning extract and a partial renewal of the tanning liquor, and also make room for further quantities of tanning extracts in the tan vats.

After a certain time, when the skins have absorbed the tanning solution and show-no trace of lime on the inside, they are taken out and suspended in the tanning vats which contain a concentrated tanning solution. In those vats the liquor is made to circulate rapidly and sulphurous anhydride is introduced from time to time, the temperature being maintained at 35 degrees C. It is of advantage to have a temperature of 30-35 degrees 0., but the operation can be carried on with liquors at ordinary temperature.

When the tanning is done in tubs one proceeds in a similar fashion, introducing the sulphurous gases through a tube opening at the bottom of the liquor contained in the cleaning tub or the tanning tub.

In all cases the current of sulphurous gas (S0 is kept in action until the water will not absorb any more of the gas and the smell of it becomes perceptible.

The advantages of this process are as follows:

1. The lime is eliminated from the skins in a perfect way and at the same time the tanning liquors are fully utilized.

2. A moderate plumping or swelling of and protect them from oxidation.

the skins is produced, and likewise a very fine rain.

3. lhe tanning liquors are protected from oxidation and are kept always clear and limpid, one of the defects at present being that the tanning liquors used gradually turn duller and become almost muddy. ,Thus leather of very fine colour and perfectly tanned is obtained. 1

4:. The composition of the tanning liquors do not alter while they generally do when bisulphite of soda is added to clarify them The bisulphite of soda becomes oxidized and converted into sulphate of soda, which accumulates in the tanning liquors, giving rise to an excessive quantity of soluble non-tanning matters, with a consequent increase of the percentage of ash in the tanned product.

What we claim is: p p 1. A process oftanmng which comprises.

.first cleaningthe hides in a solution im-