US1763368A - Method of accelerating and improving tanning processes - Google Patents

Description

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atented lune lmi lfl FRIEDRICH JPOSPIECH, OF DRESDEN, GERMANY, ASSIGNOR T0 CHIIEMJESCHE FABRIK IOT'JL d6 (30., OF DRIIE$DEN, GERMANY METHOD OF ACCELERATING AND IMPRUVING TAN'NING PROGESSES No Drawing. Application filed August 26, 1927, Serial No. 215,761, and in Germany August 21, 1926.

The hitherto employed tanning processes in which vegetable tanning principles are used are in general, very imperfect, because a very long time is needed for carrying out such processes and the coloring of leather produced in the known tanning processes is not always satisfactory. Normally, the tan ning of upper leather, which. has been pre liminary tanned in the usual ooze of M -2% Be. and has been finished in an ooze of (5 lie, lasts for at least 12 to 16 days. Several proposals have been madefor shortening the duration of the process but the quick-tanning methods hitherto proposed will not however give entirely satisfactory results, because the grains 'aretanned before the inner parts of the unhaired hides are tanned, whereby the grains are damaged and the surface of the leather assumes an unattractive look.

According to one quick-tanning method, the hides are treated in tanning liquors, which have been enriched by means of nontanning substances (tannin, gallic acid, resorcin and the like) and are thereupon brought into strong tanning liquors, which are supposed to effect a thorough tanning of the hides in a short time.

According to another proposal, the hides, that is, the grained parts of the same are treated with inorganic salts adapted to make the grains non-sensitive to the astringent effects of strong tanning liquors (alumen, Glaubers salt, kitchen salt, bitter salt in combination with bichromate, boric acid, oxalic acid, chloride of calcium, hydrochloric aniline).

The first of the processes mentioned is expensive, and on account of the sensitivenessof the employed substances to iron, is not to be depended upon. Further the tanning lasts for at least 3 to 4 days, because the liquor at the first stages of treatment must not be stronger than 3 to 3 156. in order that the grains are not damaged.

The initial treatment with inorganic salts, in accordance with the second of the above mentioned proposals, is always risky, because conversion with the vegetable tanning agents may take place, whereby the coloring properties, the softness, the flexibility and the touch of the grains are ali'ccted in an unfavorable manner. When chronilum salts and alumh num salts are used also the character of the leather is changed, so that a product is obtained, which resembles the so-called semichrome-leather.

l have now found, that the above mentioned drawbacks are avoided and the duraqualities superior to the leather hitherto obtained.

Especially suited for the purpose are sul phonic acids which are obtained by condensing naphthalene or ring substitution productsof naphthalene, or the corresponding sulphonic acids, in the presence of condensation or oxidationv agents with alcohols of the aliphatic series, having more than two carbon atoms.

Such substances may, for instance, be produced by converting one molecule of naphthulene into a mixture of alpha and beta. sulphonic acids and bringing the same into reaction with 2.1 molecules of isopropyl-alcohol and 221 molecules of concentrated sul 'ihurie acid at temperatures below 100 C. and in the presence of a large quantity ofconcentratcd sulphuric acid. The sodium salt, obtained in the usual Way by treating with lime water and boiling the thus obtained sulphonic acid of the condensation product of naphthalene and iso-propyl alcbhol, forms directly a suitable addition for the tanning process to be described.

Instead of naphthalene, other polynuelear aromatic hydrocarbons and substitution products of such substances, as for instance, halogen or hydroxy substituted compounds, may be used. Instead of iso-propyl alcohol also higher alcohols especially such of the secondary series may be employed. Further aliphatic and cyclic oletines, such as tetradissolved in concentrated sulphuric acid, are well suited for the purpose in question. The condensation products are amorphous substances which very easily dissolve in water and which as free acids and also as alkali salts possess a considerable moistening and frothing ability.

hydrobeii zol Example 1 kg. of unhaired hides, which are designed for tanned upper leather and which, therefore, have been accordingly treated in the lime pit, are unlimed and eventually soaked. These hides are not as usual brought into a diluted color solution (tanning liquor of 0.5 to 1.5 136.) but are treated with a solution of 2 kg. of one of the above named substances in 300 liters of water for 3 to 4 hours, whereupon the hides are directly brought into a tanning liquor of 4 to 6 B., which is sufficiently strong to effect the final tannin The tanning may be performed in drums or rats. As a tanning agent any vegetable extract or mixture of different extracts may be used. The entire tanning process lasts for 2a to 36 hours.

Ewa-mple 2 100 kg. of unhaired hides, which are designed for bottom leather and have been accordingly treated, are unlimed as possible by means of an organic acid (lactic acid, formic-acid, butyric acid or the like) Thereupon 2 kg. of one of the above named substances are added to the same bath (or to a fresh bath) and are allowed to act upon the hides. For this purpose small amounts of organic acids may be added anew in order that the unhaired hides may be raised sufficiently. After 3 to L hours the hides can be put into the tanning bath. Any vegetable extract may be used. The extract is chosen in accordance with the purpose for which the finished product is intended to be used.

Example 3 The tr atment of unhaired hides canalso ire performed in a weak tanning liquor to which 2 kg. of one of the above named substances are added for each 100 kg. of hides.

I claim 1. A method of accelerating and improving the tanning processes when working with vegetable tanning agents, which comprises adding to the tanning liquor, condensation products of naphthalene sulfonic acids and alcohols of the alipathic series having more than two carbon atoms in the presence of condensation mediums.

2. A method of accelerating and improving the tanning processes when working with vegetable tanning agents, which comprises adding to the tanning liquor sulphonic acids of propylated naphthalene.

FRI EUR [(H POSPIECH.

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