US1583801A - Artifical tanning substance - Google Patents

Description

Patented May 11 1926.

' i UNITED STATES 1,5 3,801v PATENT-OFFICE. j

OTTO SCHMIDT, OF LUD'WIGSHAFEN-ON-THE-iR-HINE, GERMANY, .ASS IG-NOR TO BADISCHE ANILIN- & SODA-FABRIK,' F LUDWIGSHAFEN-ON THE-RHINE, GER-' MANY, n'conronA'rroN or GERMANY.

ARTIFICIAL TANNING SUBSTANCE. I

1N0 Drawing.

This present invention relates to improvements in the preparation of artificial tanning substances,

It is already known that by treating 5 charred vegetable materials such as charcoal 1 with nitric acid or nitrogen oxids substances possessing tanning properties are obtained.

I have now found that the tanning properties of these substances are. much improved by bringing them into a weakly acid condition. This result may be obtainedby neutralizing them partially or wholly and again slightly acidulfiting them. Preferably, the products are neutralized to about to 40 per cent ;v any other degree of neutralization, however, may also be suitable.

hen tanning substances prepared 'according to this invention are used the advantage that the hides do not swell too much 20 from the commencement of the operation re- 1 suite and the tanning process is thereby accelerated and the hides tanned more thorbnghly. The color of the leather is also better and lighter by reason of the hides not swelling so much as aforesaid. I

I I have furth r found that especially good tanning substances are obtained by oxidizing charcoal containing an unusual quantity of oxygen compounds and then partially-neutralizing the product. Such charcoals as.

contain 9 percent or more of oxygen, calculated on the coaly substance free from ashes, are especially sultable, yielding with amoderate consumption of nitric acid or nitrogen as oxids tanning substances of a remarka ly.

light-color. It is generally sufiicient to neutralize a. small fraction of the acidity of the product.

The said substances can be mixed, before 40 or after reducing their acidity, with other artificial tanning substances, such for ex" 4 ample as formaldehyde-naphthalene-sulfonic acid condensation products on their sal ts, orotherartificial tanning substances containing one or several sulfonic' acid groups, or their salts.' They can also be mixed with ve etable tanning substances such, for e-xamp e, as quebracho and the like. With such a combination, and especially that with ve etable tanning matters, the

grainof the. eather will keepflmuch better than in the case of leather tanned by mix- .tures-with the raw oxidation products pos Application filed August 24, 1925. Serial No. 52,233.,

sessing no reduced acidity," in the lattercasc.

the grain is often brittle.

The nature of this invention is more fully '5 explained by the following examples to which however the invention is not restricted. The parts are by weight.

I Example 1.

20 parts of a dry tanning substance, obtained by oxidizing. charcoal with nitric acid, possessing an acidity equal to about 10 cubic centimetres of normal caustic soda liquor to l'gram of the substance, are dissolved in 80 parts of-water and mixed with 40 parts of normal caustic soda.

280'parts of the tanning solution soprepared are diluted with water to 1000 parts by volume. Into this tanning bath 60 parts of well delimed hide are introduced. The hide is tanned in the course of 8 to 10 days and a full, soft leather of a red-brown color is obtained.

Example 2.

140 parts by weight of the solution prepared as described in the first paragraph of Example 1 are mixed with parts of chestnut-wood extract and then diluted with water to 1000 parts b volume. About 60 parts of carefullyde imed hide are tanned" in this bath in the usual manner in 10 to 14 days. A light-brown full leather with stable grains is obtained. v

The tanning oxidation product ma be prepared as follows: parts of ely powdered charcoal with an oxygen content of 14.8 per cent,-'calculated on ash-free sub.- stance, are stirred'with 160 parts of water. parts ofa 95 per cent nitric acid 'solution are then slowly added whereupon the mass is slowly heated to the boil. After boilingfor 12 hours the greater part of the 95 liquid is-distilled oif and'680 more parts of a.95 per cent nitric acid solution are added while continuing boiling for two days. The mainpartof the aqueous nitric acid left in the vessel is distilled 0s, employing finally 1 a vacuum, and for removin the last traces of nitric acid an addition 0 water is made repeatedly with subsequent evaporation.

The residue is powdered, giving an orange to ellowishpowder which is completely solu le in water and has excellent properties. Instead of nitric acid, nitrogen oxid may be employed.

I claim:

1. As an article of manufacture an oxidation product of charcoal possessing tanning properties and being partly in the form of an acid and partly in the form of a soluble salt. v

2. Asi1n article of manufacture an oxidation product of charcoal possessing tanning properties and being partly in the form of an acid and partly, in the form of a soluble salt in combination with another tanning material.

3. The process of prodncingtanning materials which consists in acting on charcoalwith a nitric acid solution and partly neutraliz ng the oxidation product with a baseforming a soluble salt.

4. The process of producing tanning materials which consists in oxidizing a charcoal containing at least 9 per cent of oxygen, calculated on the coaly substance free from ashes with nitric acid and partly neutralizing the oxidation product with a base forming a soluble salt.

The process of producing tanning ma terials which consists in oxidizing a charcoal containing at. least 9 per cent of oxygen, calculated on the coaly substance free from ashes with nitric acid, partly neutralizing the oxidation product with a baseforming a soluble salt, and mixing the product with 'a natural tanning extract.

In testimony whereof I have hereunto set my hand.

OTTO SCHMIDT.