US1938388A - Tanning process - Google Patents

Description

Patented Dec. 1933 1,938,388 TANNING rnoosss Alphons 0. Jaeger, Mount Lebanon, Pa., assignor to The Selden Company, Pittsburgh, Pa., a corporation of Delaware No Drawing.

Application February 27, 1931 Serial No. 518,900

4 Claims. (01. 149-5) This invention relates to the tanning of hides, skins and the like, using a new class of tanning materials.

According to the invention, leather is produced 5 by the tanning of hides and skins in the presence of a new class of tanning agents, which may be used alone or in admixture with other vegetable or artificial tanning materials. The new tanning agents of the present invention are alkali metal salts of the sulfonated products resulting from the condensation of carbohydrates with sulfuric acid and polymerized residues from the vaporization of crude aromatic hydrocarbons such as crude anthracene, crude naphthalene and the like, by selective sublimation or distillation.

In these processes the crude hydrocarbons containing, in the case of crude anthracene, a mixture of anthracene, phenanthrene, carbazole, dead oils and other high boiling constituents, are subjected to elevated temperatures in the presence of solvent gases for long periods of time,

during which the more volatile portions are removed. As aresult, the heavier constituents that remain in the still are highlypolymerized, as pointed out in my prior Patent No. 1,892,770, and to a large extent lose their original identity and become transformed into tarry masses of high molecular weight and unknown constitution. By the present invention these tars, which have hitherto served no useful purpose, are converted into valuable condensation products which are useful for the tanning of hides into leather. These substances are new chemical products but are not claimed as such in the present application, this forming the subject matter of my copending application Serial No. 512,752, filed J anuary 31, 1931.

As is brought out in the application just referred to, these tanning materials can be readily prepared from very cheap materials, and are characterized by a good light color and excellent tanning properties. They possess rapid penetrating qualities as compared with the vegetable tans and are thus not only valuable tanning agents when used alone but are also well suited for mixture and use with the ordinary vegetable 'tans. Being alkali metal compounds, and having a fairly high pH value, they exert a stabilizing action on the ordinary vegetable tanning extracts and prevent them from precipitation by oxidation on exposure to the air, and they are thus valuable, not only for use as an aid in tanning, but also for admixture with the vegetable tans before shipment.

While the stabilizing action and rapid penetration of the novel tanning agents of the present invention make them valuable aids when used in conjunction with the less astringent tanning extracts, such as those of gambier, oak, chestnut and sumac, these condensation products are of even greater value when used in conjunction with the more astringent tans such as quebracho, hemlock, and the like. In the process of vegetable tanning it is well known that the rate of diffusion, and consequently the rate of tannage is inversely proportional to the astringency of the tan used. Such extracts as those of quebracho, hemlock, larch, etc. therefore require considerably longer time to completely ten the hides than do the less astringent tans such as gambier, probably because the more astringent tans immediately effect such a complete tannage at the surface that rapid penetration is retarded. The addition of the tanning materials of the present invention to the liquors of an astringent vat aids in the penetration, not only by acting as a less astringent diluent, but also by the fact that its more rapid penetration efiects a partial tannage in advance of the vegetable extract, thus preventing imperviousness of the outer portions of the hide.

.The invention is not limited however to the use of the novel tanning agents in conjunction with more astringent tans but on the contrary their properties are such that they may be used alone or in conjunction with any material having tanning or non-tanning properties.

As has been stated, the tanning agents of the present invention are for the most part slightly alkaline and usually require the addition of acids, such asacetic, phosphoric, lactic, etc. to bring the tanning liquors to a value pH=2-5 or thereabouts in order to exert the most favorable tanning action. Of course where the tanning agents are used in conjunction with other and more acid materials allowance for this fact will be made 95 and the hydrogen ion concentration will be adjusted accordingly.

The invention will be further illustrated in con junction with the following examples to which, however, the invention is not limited. The parts are by weight.

Example 1 50 parts of cellulose in the form of old sulflte paper are introduced into 750 parts of concentrated sulfuric acid, thorough agitation and cooling being provided. Thereupon 134 parts of the residue from the vaporization of crude anthracene in the catalytic anthraquinone process are stirred in and the stirring continued until all of the resi- 110 due dissolves up. The mass is then poured into 10,000 parts of water, the excess acidneutralized with lime, fitered, and the calcium salt transformed into the sodium salt by means of sodium carbonate. 6n evaporating the filtered solution, a brown mass is obtained which is the salt or" the condensation product. The yield amounts to 173% by weight or the cellulose and anthracene residue.

The hides, delimed and hated, are introduced into a tanning bath containing 40 grams per liter of the above described condensation product together with suitable amounts of oak bark tanning extract. being allowed to remain with suitable agitation after the tanning action is well started, until complete tannage is efiected. The leather obtained after washing and the usual further treatments, is of good appearance and of excellent strength.

Eacmple 2 50 parts of cellulose in the form of old sulfite paper are introduced into 750 parts of concentrated sulfuric acid, thorough agitation and cooling being provided. Thereupon 134 parts of the residue from the sublimation of crude naphthalene in the catalytic phthalic anhydride process are stirred in and the stirring continued until all of the residue dissolves up. The mass is then poured into 10,000 parts of water, the excess acid neutralized with lime, filtered, and the calcium salt transformed into the sodium salt by means of sodium carbonate. On evaporating the filtered solution, a light brown mass is obtained which is the sodium salt of the condensation prodnot. The yield amounts to ISO-170% by weight of the cellulose and naphthalene residue.

Hides, properly prepared, are tanned in baths oi the above condensation product, the baths increasing in strength as the period oi. tannage proceeds. The pH of the tanning bath is adjusted by the addition of acetic acid, sodium phosphate being added as a buffer if necessary.

Example 3 50 parts of starch or sugar are introduced into 750 parts of concentrated sulfuric acid, thorough agitation and cooling being provided. 'I'hereupon 134 parts 01' a residue from the vaporization of nasaaes semi-purified 60-70% anthracene are stirred in and the stirring continued until all of the residue dissolves up. The mass is then poured into 10,000 parts of water, the excess acid neutralized with lime, filtered, and the calcium salt transformed the sodium salt by means of sodium carbonate. On evaporating the filtered solution, a brown mass is obtained which is the sodium or" the condensation product. The yield amounts to 175% by weight of the starch and anthracene residue.

The above condensation product is admixed with an equal weight of fresh quebracho, cats or gambler extract as comes -from the leaching vat, and the mixture is evaporated to the usual commercial strengths (10-30% moisture content) for sale on the market. The material so produced forms an excellent tanning agent, and precipitation of the vegetable tan by exposure to air, hoth during evaporation and in the preparatien of the tanning liquors, is reduced by the presence or" alkali metal compound.

What is claimed as new is:

l. A process of tanning hides, which comprises treating the hides with an aqueous solution containing at least one salt of a condensation product of a carbohydrate, sulfuric acid and the polymerization residue from the vaporization of a crude aromatic hydrocarbon.

A process of tanning hides, which comprises treating the hides with an aqueous solution containing at least one alkali metal salt of a condensation product of cellulose, sulfuric acid and the polymerization residue from the vaporization of a crude aromatic hydrocarbon.

3. A process of tanning hides, which comprises treating the hides with an aqueous solution containing at least one alkali metal salt of a condensation product of a carbohydrate, sulfuric acid and the polymerization residue from the vaporization of crude anthracene.

4. A process of tanning hides, which comprises treating the hides with an aqueous solution containing at least one alkali metal salt of a condensation product of cellulose, sulfuric acid and the polymerization residue from the vaporization of crude anthracene.

ALPHQNS O. JAEGER.