US2973240A - Tanning with alkylbenzene sulfonate in combination with chrome tanning - Google Patents

Description

TANNING WITH ALKYLBENZENE SULFONATE 1N CGMBINATION WITH CHROME TANNING Friedrich Schmitt, deceased, late of Dusseldorf, Germany, by Alice Schmitt, geb. Neukirchner, heir, Dusseldorf, Germany, assiguor to Boehme Fettchemie G.m.b.H., Dusseldorf, Germany No Drawing. Filed Dec. 5, 1956, Ser. No. 626,547 Claims priority, application Germany June 21, 1951 2 Claims. (Cl. 8-94.33)

' mal collagen fiber and can be smoothly Worked into the skins. They may be combined with the ordinary mineral, vegetable, or synthetic tanning agents or with tanning agents used in oil tanning.

The hydrocarbon radicals introduced into the sulfonic acids determine to a certain extent the properties and efiect of the sulfonic acids. With an increasing chain length of the aliphatic hydrocarbon radicals, preferably from 12 to 18 carbon atoms, the tanning agent will assume the character of a tanning agent used in oil tanning or the character may become more pronounced in that respect. By using the tanning agents according to the present invention, the tanning process may be carried out much more rapidly than with the use of the conventional agents for oil tanning, such as fish oils.

The tanning agents according to the invention may be used for tanning hides and furs of all types, more particularly hides of calves, sheep, goat, deer, does, or cows. The hides are treated by known methods by soaking in Water, liming, and/or pickling, if necessary.

The salts of sulfonic acids substituted by higher molecular hydrocarbon radicals to be used for the tanning method according to the invention are for instance as follows: alkylsulfonic acids, alkylarylsulfonic acids, alkylcycloalkylsulfonic acids, and the like. The aliphatic hydrocarbon radicals can be branched or straight .and may contain 12-18 carbon atoms or more. The

sulfonic acids may, furthermore, contain in the hydrocarbon radicals heteroatoms or heteroatom groups, or substituents; as such are named more particularly carbonarnide or sulfonamide groups; as heteroatoms, sulphur and oxygen. As substituents, are mentioned oxy groups. The sulfonic acids may also contain several sulfonic acid radicals.

The following examples are given for sulfonic acids to be used according to the invention: Alkylcyclohexylsulfonic acids (alkyl radicals about C C naphthenylsulfonic acids, alkylbenzenesulfonic acids, or mixtures of the same (alkyl radicals about C C higher molecular a1kylnaphthalenemonosulfonic acids or their mixtures, acyloxy, or acylaminoalkanesulfonic acids, and the like.

The sulfonic acids are used in the form of their Watersolnble salts with inorganic or organic bases, for instance in the form of their alkali metal or ammonium salts or in form of their organic amino compounds,

In operation, they are kneaded into the hides, either 2,973,240 Patented Feb. 28, 1961 directly or in the form of their aqueous solutions or emulsions in as high a concentration as feasible; as to the amount of tanning agents used, it should be about 5 to 8% with reference to the weight of the hides. After or before the agents have been worked into the hides, the leather is processed and finished according to conventional methods. In the combination process which is used, the salts of the sulfonic acids used according to the invention may be applied in a step by themselves before or after treatment of the hides with the known tanning agents.

As mentioned before, the tanning agents may be used in oil tanning and may, in that case, be combined with fish oils or sulfonates of aliphatic alcohols.

The invention will now be illustrated by a number of examples, but it should be understood that these are given by Way of illustration and not of limitation, and that many modifications of the amounts and substances mentioned can be made without departing from the spirit of the invention.

In the following examples the percentage of tanning agents given refers to the weight of the hides.

Example 1 a solution containing of water, 0.5 alkylbenzene sodium sulfonate (alkyl radicals C -C 1 to 2% formic acid, and 6 to 8% sodium chloride. After the pickling operation the hides should have a pH-value of 3.2 to 3.8 in the cut surface.

After having been allowed to drip, the hides are kneaded for 4 hours at a temperature of about 20 C. with a 5% solution of alkylbenzenesulfonate (alkyl radicals C C which has been diluted with the double or triple amount of water. Subsequently, the hides are treated with 0.3-0.7% chromium oxide in form of a concentrated solution of a commercial chromium salt in alkaline solution adjusted to 4:126:12. The tanning treatment is terminated after 2 hours and the leather is allowed to remain lying covered on the block for 4 to 5 days. Subsequently, rinsing with lukewarm water takes place for 15 to 20 minutes and finishing treatment is effected in the known manner. The leather is full and soft to the touch and has high resistance to tear. The grain is smooth and closed.

Example 2 Well unlimed and pickled split cowhides are pretanned with 1 to 1.5% formaldehyde, sodium bicarbonate being added in half the amount of the added formaldehyde. The split hides remain overnight on the block, whereafter they are sammied and pared. Then, an emulsion consisting of 5-6% alkylbenzene sodium sulfonate (alkyl radicals C -C 6% of fish oil (iodine No. over and 0.5% of formic acid or 1.5% of a mixture of low molecular fatty acids obtained in the oxidation of parafiin, are kneaded in a conventional kneading vat or a hot air vat for 3-4 hours.

The leather remains overnight on the block and is then hung up for 3-4 days in a warm room, whereafter it is kept for 14 days in a pile. The leather may also be immediately put in a pile, similar to the tanning of suede leather, and may be subsequently dried. Thereafter, the leather is washed with calcined soda in an amount of 0.3 to 0.5 in order to remove excess of fish oil, Whereupon it is dried and finished as usual.

The split leather has a suede-like character and is distinguished by a very high tear resistance. As compared to chromium tanned split leather, it has a much better heat-insulating property.

Example 3 Split cowhides which have preferably been ashed, unlimed and pickled, are pre-tanned with 0.5 to 1.5% of formaldehyde, which in a conventional manner has been de-acidified with sodium bicarbonate. The hides remain overnight in the de-acidified formaldehyde, then they are allowed to drip on the block and are sammied and pared.

Thereupon, a. mixture consisting of 2 to 3% alkylbenzene sodium sulfonate (alkyl radicals C12C18) with 23% alkyl sodium or ammonium sulfonate (alkyl radicals C -C and 6% of fish oil (iodine No. over 140) is worked into the leather in a tanning vat at 20-30 C. The operation takes 3-4 hours. Instead of saturated alkyl sulfonates, unsaturated ones may also be used.

The hides remain overnight on the block and are then hung up in a warm room. They are thereafter allowed to age for some time on bark. The split leather may be piled up for a few days before drying. After drying, the leather is washed with 03-05% calcined soda, in a manner used in suede tanning.

Example 4 Cowhides pickled as usual are kneaded for 4-5 hours with an emulsion of 6% fish oil (iodine N0. over 140), 4% alkylbenzene sodium sulfonate (alkyl radicals C C and then treated as in Example 2. Leather obtained is distinguished by a specially supple touch, high tear resistance and a smooth, adherent grain.

Example Pickled cowhides having a pH-value of 3.2 to 3.6 are kneaded in a tanning vat for 3-4 hours at a temperature between 20 and 30 C. with 2% alkylbenzene sodium su1 fonate (alkyl radicals C C 2% alkyl sodium sulfate (alkyl radicals C C especially also the oleyl radical) and with 2% alkyl sodium sulfonate (obtained by treatment of an aliphatic hydrocarbon fraction C -C with sulfur dioxide and chlorine, and subsequent saponification with caustic soda) with addition of 5% fish oil (iodine No. over 140).

Further treatment as in Example 2. The single components as well as the mixture of oil-tanning agents are rapidly taken up by the hides.

As compared to chromium tanned leather, the leather has a softer, more flexible touch. It has a very high tear resistance and is well permeable -to air without increase in moisture absorption.

Example 6 Pickled doe hides are treated in a mixture of water, 0.5% alkylnaphthalene sodium sulfonate (alkyl radicals C 43 1-2% formic acid and 2-4% of an aqueous organic acid mixture obtained in the paratfin oxidation and 610% sodium chloride, the whole being adjusted to a pH-value of 3.5. After dripping, the hides are kneaded for 4 hours with 6% alkylnaphthalene sodium sulfonate (alkyl radicals C -C diluted with the same or double amount of water. Subsequently, I treat with a weak commercial chromium salt 0.30.7% by weight in alkaline solution adjusted to 4:12-6:12. Subsequent treatment and finishing operations are conventional. Leather so obtained is soft and Warm to the touch and is particularly suitable for the manufacture of gloves, wearing apparel and leather pants.

What is claimed is:

1. A method of tanning unhaired, pickled animal skins having a pH of approximately 3.2 to 3.8 comprising kneading said skins with a 5 percent aqueous solution of an alkylbenzene sulfonate having from 12 to 18 carbon atoms in its alkyl radical for 3 to 4 hours at 20 to 30 C. and in the presence of water in an amount of approximately 2 to 3 times the volume of said solution, thereafter tanning the leather thus obtained from said skins with an alkaline, water-soluble chromium salt tanning solution containing approximately 4 to 6 parts of said salt in 12 parts of water, and washing said leather to obtain a full soft surface having high tear resistance.

2. Amethod as claimed in claim 1 wherein said skin is kneaded with fish oil after pickling and before kneading with said sulfonate.

References Cited in the file of this patent UNITED STATES PATENTS 1,715,410 Daimier et al. June 4, 1929 1,927,910 Balle Sept. 26, 1933 2,249,757 Flett July 22, 1941 2,692,180 Schmitt et al. Oct. 19, 1954

Claims (1)

1. A METHOD OF TANNING UNHAIRED, PICKLED ANIMAL SKINS HAVING A PH OF APPROXIMATELY 3.2 TO 3.8 COMPRISING KNEADING SAID SKINS WITH A 5 PERCENT AQUEOUS SOLUTION OF AN ALKYLBENZENE SULFONATE HAVING FROM 12 TO 18 CARBON ATOMS IN ITS ALKYL RADICAL FOR 3 TO 4 HOURS AT 20 TO 30*C. AND IN THE PRESENCE OF WATER IN AN AMOUNT OF APPROXIMATELY 2 TO 3 TIMES THE VOLUME OF SAID SOLUTION, THEREAFTER TANNING THE LEATHER THUS OBTAINED FROM SAID SKINS WITH AN ALKALINE WATER-SOLUBLE CHROMIUM SALT TANNING SOLUTION CONTAINING APPROXIMATELY 4 TO 6 PARTS OF SAID SALT IN 12 PARTS OF WATER, AND WASHING SAID LEATHER TO OBTAIN A FULL SOFT SURFACE HAVING HIGH TEAR RESISTANCE.