US1404633A - Process for tanning leathers and skins - Google Patents

Description

UNITED STATES PATENT OFFICE.

HENRI MORIN, 0E ST.I)ENIS, FRANCE, AssrGNoR TO LA socIETE GENTY, nouen & CIE. (socIETE EN NoM COLLIECTIF ET EN COMMANDI'IE SIMPLE), or PARIS,

FRANCE.

PROCESS FOR TANNING LEATHERS AND SKINS.

No Drawing.

Patented Jan. 24, 1922.

Serial No. 135,368.

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

To all whom. it may concern.

Be it known that I, HENRI MORIN, a citizen of the Republic of France, residing at St.-Denis, Seine Department, 14 Rue Catnlienne, in the Republic of France, have in-- rented a certain new and useful Process for Tanning Leathers and Skins, (for which I have obtained French Patent No. 479,908, filed Oct. 22, 1914, delivr date Feb. 29, 1916,) of which the following is a specification.

This invention relates to a process for white tanning leathers and skins. The process consists in the incorporation with the cells of the skins, whatever may be their origin and their nature, of silica or oxide of silicon which, combining with the con stituent elements of the skin, forms with them an insoluble imputrescible composition.

This insoluble composition is above all formed in the layers of the fibres of the skin and prevents them from adhering together. which allows them to slide upon one another, and thus gives the skin very great suppleness.

In order to incorporate the silica into the skin, and to compel it to be combined with the elements which constitute the latter, any substance containing silica, in a state of combination, can be employed, but it is preferable to use either silicate of soda or silicate of potash. and afterward a substance. such as an acid or metallic salt for instance, capable of being combined with the soda or the potash of said silicate in such a way is to liberate silica and to allow its combination with the organic matter. Nevertheless, the use of a silicate is not absolutely necessary because the tanning can also be oh tained by dipping the skin in a bath containing gelatinous silica in suspension or dissolution. In a word, the tanning results from the direct combination of the silica with the skin.

For tanning skins or leathers according to this process the following method of operation may be adopted 1-Tl16 skins coming from a steeping vat, that is to say, when shaved and after having been well rinsed, are immersed in a bath of water containing per cent to 10 per cent, according to the firmness or suppleness which it is desired to obtain, of silicate of soda or of potash. These silicates should be of the concentrat on usual in commerce and it will be sufficient, for a skin of 800 grammes to 1 kg, to take 3 litres of one of the solutions above mentioned, particularly if operating in a vat or the like, to obtain a perfect tanning. The duration of the immersion and the concentration of the solutions of the silicates should. be according to the nature of the skins. their thickness, their out, etc., it is for the operator to fix these elements by re peated trials. Take as an example the impregnation of a dozen sheep skins of any origin and of medium out. In operating in a vat, 36 litres of solution of silicate at 2?; per cent will be sufiicient and the impregnation should not last more than 48 hours. It is understood that when dealing with skins which are thick or of a very firm nature, very close as in the case of leather, the tanning period will be rather longer and the quantity of silicate somewhat larger. If split skins, grain or flesh, are to be treated instead of whole skins, the duration of impregnation will be shorter and the strength of the silicate solution lower. Indeed all skins and hides designed for all uses can be tanned by the present process.

After having, as above stated, immersed the skins in a solution containing silica and left them therein for several hours, they will be seen to swell considerably. It will then only be necessary to provide a suitable means for separatingthe silica from its combinations and to permit it to be combined with the fibres of the skin, This combination should take place relatively slowly. 1t can be effected by means of any substances capable of displacing the silica from its combinations without injury to the skin such as most mineral or organic acids and a large number of metallic salts, for example, chloride of zinc, etc. Amongst the substances capable of being used for this action acetic acid gives excellent results, and, up to the present, appears preferable.

The quantity of acid employed should be strictly proportioned to the quantity of silicate contained in the solution; for example, if 100 litres of water be employed charged with 5 per cent of silicate, which represents 108 5 kg. of this product, it would be necessary I to add 5 kg. of acetic acid at 7 Baum.

porosity of the skins.

This acid can be added all at once or progressively, as'the operator may choose, and

that without removing the skins from the vat.

hen the acid has been added the combination of. the silica will commence to take place into the cells of the skin, and in order that the tanning may be complete it will be necessary to leave the skins for several days according to the thickness and degree of If sheep skins, for example, are to be treated it will only be necessary to allow the action of the acid bath to last for a few days.

Moreover, during the tanning, samples should be taken which should be rapidly stove-dried and the edge examined after having cut them atseveral places. If, on the cut edges, a brown streak is perceived the skin is not thoroughly tanned, and it will be necessary to continue the tanning until this streak disappears, that is to say, the tanning will be completed when the white colour of the skin shall have spread uniformly to the interior starting from the outer part of the flesh side to the outer part of the grain side.

lVhen once the tanning is finished the skins are suitably rinsed so as to free them from any trace of non-combined materials without letting them dry but allowing them to thoroughly drain.

They are then impregnated with a suitable nutriment or improver until the desired degree of suppleness is attained. The question of the nutriment is not here dealt with as the special object of this invention is the tanning. Moreover nutriments are very numerous and can easily be chosen. That which seems preferable is the nutriment usually employed for chrome tanning and composed of soap, oil and yolk of eggs; the

recipe can be found in any treatise on tan- 11 tanned skins are not to be treated with nutriment at once, and they are to be kept white either for subsequent dyeing or to reserve them for a. mixed tanning, they can, after having been rinsed, be impregnated with brine and left to dry in the air. This method of procedure will allow of keeping the skins with all their supploness as long as may be desired.

Instead of brine a slightly glycerinat'ed water can'be employed. Brine is, however,

preferable to glycerine as a slight excess of the latter substance has the effect of attracting the moisture of'the air which tends to produce mouldiness upon the skins when they are a-llowed to remain a long time before being used.

lVhen it is required to make use of the skins thus prepared it is only necessary to rinse them and feed them if it is required to sell them as white skins or to dye them and feed them after the dyeing, or, again to feed them whilst dyeing them, if the nutriment agrees with the dyeing, or, again a mixed tanning may be resorted to, according to the requirements of the work to which the skins are to be subjected, or according to the will of the operator.

It is to be observed that this tanning properly carried out is suitable for all the working requirements of the skin; it compares favourably with chrome tanning as regards suppleness and firmness of the grain and flesh; itcosts less, requires'less dressings and.

combinations of mixed tanning of vegetable or mineral nature whatever they may be and is thus suitable for all manufacture, whilst effecting an important economy in the materials employed especially when these materials are expensive like for example, sumach employed in morocco leather dressing.

In any case these mixed tannings are only referred to as examples, the object of the present invention consisting essentially in the process of tanning according to which silica is incorporated by a suitable means with the constituent elements of the skins of animals.

'l'laving now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

'l. process oftanning skins wherein the skin is steepedin an alkaline silicate solution and'afterwards treated by a solution of acetic acid.

2. A process oftanni'ng skins wherein the skin is steeped in an alkaline silicate solution, afterwards treated by a silicate decomposing agent and then impregnated with brine and rinsed and, dried.

In testimony, that I claim the foregoing The leather treated is supple, if.