US1938389A - Tanning process - Google Patents

Description

' used.

Patented Dec. 5, 1933 oNiTED STATES TANNING PROCESS Alphons O. Jaeger,Mount Lebanon, Pa., assignor to The Selden Company, Pittsburgh, Pa., a corporation of Delaware N0 Drawing.

Application February 27, 1931 1 Serial No. 518,901

12 Claims.

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 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, phthalic anhydride and substituted or unsubstituted aromatic hydrocarbons in the presence of sulfuric acid, either pure or crude materials being These substances are new chemical products but are not claimed as such in the present application, this forming the subject matter of my co-pending application Serial No. 512,753, filed January 31, 1931. One of their outstanding features is the presence of phthalic anhydride in combination with the cellulose and aromatic hydrocarbon which acts as an improved loading agent, serving to increase the weight and fullness of the leather without materially altering the solubility in water of the preparation.

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 alsofor admixture with the vegetable tans beforeshipment.

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 ofgambier, 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-thje astringency of the tan used. Such extracts'as't-hose of quebracho, hemlock, larch, etc. therefore require considerably longer time to completelytah the hides than do the less astringent tans such as gambler, 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 penetration, not only by acting as a less astringent diluent, but also by the fact that its more rapid penetration effects 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 as acetic, phosphoric, lactic, etc. to bring the tanning liquors to a value pI-I=25 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 and the hydrogen ion concentration will be adjusted accordingly.

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

Example 1 1500 parts of 100% sulfuric acid are cooled to 20 C. and 70 parts pure phthalic anhydride are slowly added. After addition is complete, 100 parts cellulose in the form of waste paper or the like are added with stirring during two hours, and the mixture is further stirred with cooling for a period of three to six hours.

After the reaction is complete, 268 parts of a residue from the vaporization of semi-purified anthracene with air in the catalytic oxidation of anthracene to anthraquinone are added with constant stirring, the temperature being maintained below 25 C. and the stirring is continued until the reaction is completed. The product is then poured into a mixture of 4,000 parts ice and water and stirring continued for one hour, after which milk of lime made from 700 parts CaO is added, followed by sufficient calcium carbonate to complete neutralization. The product is filtered and converted into the sodium salt by treatment with sodium carbonate in the usual manner.

The hides, delimed and bated, 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 effected.

The leather obtained after washing and the usual further treatments, is of good appearance and of excellent strength.

Example 2 '750 parts of 107.3% sulfuric acid are cooled to 20 C. and 34.3 parts pure phthalic anhydride, or the equivalent quantity of impure phthalic anhydride, are added. The mixture is further cooled to 16 C. and 50 parts of cellulose in the form of old sulfite paper, cotton linters or the like areadded during four hours. The mixture is stirred during a further period of eight hours and is then a blackish liquid smelling somewhat 0f S02.

To this liquid are added 134 parts of residue from the purification of crude anthracene, the addition being made very slowly during a period of five hours and the temperature being kept at all times below 20 C. Stirring is continued until the reaction is complete, the resulting mass being a deep black, viscous liquid.

The above mixture is poured, with stirring, into 2,000 parts of water maintained as cold as possible, and milk of lime prepared from 360 parts of CaO is added, after which neutralization is completed with CaCOa. After filtering, the liquid may be evaporated to produce a solid product, or the calcium may be exchanged for sodium by treatment with sodium carbonate.

Hides, properly prepared, are tanned in baths of the above condensation product, the baths increasing in strength as the period of 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 cellulosic material in the form of waste paper are stirred into 750 parts 100% sulfuric acid maintained at 15-18 C., after which '70 parts phthalic anhydride are added and stirring is continued for ten to twenty hours until reaction is completed. 130-140 parts residue from the vaporization of impure naphthalene in the catalytic phthalic anhydride process are slowly added with stirring during five to eight hours and the mixture is maintained at 35 C. for fifty to seventy hours until reaction is completed.

The reaction product is slowly poured into a mixture of 1,000 parts ice and 1500 parts water and stirred for one-half hour, after which neutralization is effected with 300 parts CaO and further amounts of CaCOa in the usual manner. The product is stirred for one-half hour, filtered, washed, and the calcium replaced by sodium as in previous examples.

The above condensation product is admixed with an equal weight of fresh quebracho, oak or gambler extract as it comes from the leaching vat, and the mixture is evaporated to the usual commercial strengths (IO-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, both during evaporation and in the preparation of the tanning liquors, is reduced by thepresence of alkali metal compound.

What is claimed as new is:

l. A process of tanning hides, which comprises treating the hides with an aqueous solution conaining at least one salt of a condensation product of a carbohydrate, a phthalic anhydride substance, at least one aromatic hydrocarbon, and sulfuric acid.

2. 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, a phthalic anhydride substance, at least one aromatic hydrocarbon, and sulfuric acid.

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, phthalic anhydride, at least one aromatic hydrocarbon, and sulfuric acid.

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, phthalic anhydride, at least one aromatic hydrocarbon, and sulfuric acid.

5. 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, a phthalic anhydride substance, the residue from the purification of a crude aromatic hydrocarbon, and sulfuric acid.

6. A process of tanning hides, which comprises treating the hides with an aqueous solution containing at least one alkali metal salt of a con-' densation product of cellulose, a phthalic anhydride substance, the residue from the purification of a crude aromatic hydrocarbon, and sulfuric acid.

7. 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, phthalic anhydride, the residue from a solvent purification of anthracene with a solvent for phenanthrene and carbazole, and sulfuric acid.

8. 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, phthalic anhydride, the residue from solvent purification of crude anthracene, and sulfuric acid. 7

9. 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, phthalic anhydride, the residue from the vaporization purification of semi-purified anthracene, and sulfuric acid.

10. 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, phthalic anhydride, the residue from the vaporization purification of crude naphthalene, and sulfuric acid.

11. 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, crude phthalic anhydride, at least one aromatic hydrocarbon, and sulfuric acid.

12. 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, crude phthalic anhydride, the residue from the purification -of at least one crude aromatic hydrocarbon, and sulfuric acid.

ALPHONS O. JAEGER.