US799246A - Process of making tanning extracts. - Google Patents

Description

ROBERTO LEPETIT AND ERNESTO TAGLIANL OF SUSA, ITALY.

PROCESS OF MAKING TANNING EXTRACTS.

Specification of Letters Patent.

Patented Sept. 12, 1905.

Original application filed July 16, 1896, Serial No. 599,718. Divided and this application filed March 18,1902. Serial No. 98,828. (Specimens) To (LU whom it Hm/, cancer/1 Be it known that we, ROBERTO Luru'rrr, chemical manufacturer, of Susa, in the Kingdom of Italy, and ERNESTO TAGLIANI, technical chemist, of Lugano, Confederation of Switzerlanchboth residing in Susa, Italy, have invented an Improved Tanning Material and Process of Producing the Same, of which the following is a specification.

This application is a division of our application Serial No. 599,718, filed July 16, 1896.

Our invention consistsin the production of a tanning extract containing the tanning principles of tan-woods and which extracts are readily soluble in cold water, forming clear solutions.

It is well known that certain extracts produced from tan-woods such, for instance, as from quebracho-wood, hemlock, and similar woods-contain the tanning principles in a difficultly-soluble resinous condition which renders their application in the tanning industry disadvantageous.

It is the object of the present invention to produce such tanning extracts in a condition readily soluble even in cold water, and thereby to render the valuable and important tanning principles contained therein available in the tanning art.

It has been known for a considerable period of time that woods of the character mentioned, particularly quebracho-wood, contain valuable tanning principles and have been employed in tanningon that account. \Vhere the wood itself has been used by the tanner, extracts have been obtained therefromin the ordinary manner generally followed in the tanning industry; but these extracts have resulted only in obtaining the more soluble principles, and the most valuable of the tanning constituents being of a resinous glutinous insoluble character have either not been extracted at all or only to a very small extent. It has been known that the entire tanning constituents of such woods may extracted by boiling under pressure; but extracts so obtained are of a glutinous or resinous character at ordinary temperatures and are only very difticultly soluble in cold water, such solutions being generally of a turbid or cloudy character.

It is the object of our invention to convert such extracts into extracts containing all the valuable constituents of the wood in a condition in which they are readily soluble in cold water, giving clear solutions.

While our invention as herein described is applied to the extracts themselves, it will be readily understood that the invention may also be applied,with more or less satisfactory results, to the wood from which the extracts are obtained.

Our invention consists in treating either the extracts themselves or the woods from which they are obtained with a salt of sulfurous acid. The particular salts which we prefer to employ are the sullites, bisullites, or hydrosullites of the alkali metals, such as sodium suliite, sodium bisulfitc, or sodium hydrosullite. Any of the corresponding sulfurous acid salts of potassium or ammonium may be employed, if desired. \Vhen acid salts, such as the bisullites, are employed, the reaction requires a temperature of 100 centigrade and above, and hence requires to be conducted in a closed vessel under pressure. \Vhen, however, neutral salts, such as the sullites, are employed, the heat required does not exceed 100 centigrade, and hence the process may be performed in an open vessel without pressure.

In order to make a complete disclosure of our invention and to enable others skilled in the art to perform the same, we give below specific examples.

Example I: For the manufacture of a quebracho extract readily soluble in cold water from the ordinary difiicultly-soluble quebracho extract:

a. Three hundred kilograms of quebracho extract of Baume are mixed with eighty kilograms of bisullitc of soda of 35 Baum and heated in a closed vessel at 130 to 145 Centigrade during eight hours.

The product obtained differs from the usual quebracho extracts by its perfect solubility even in cold water and by its property of giving a softer pale nicely-pink-colored leather very similar to hides tanned with mimosa bark. An important property of our soluble extract is that it penetrates more rapidly into the pores of hide than usually less soluble quebracho extract.

6. Five hundred kilograms of quebracho extract, one hundred. and twenty kilograms of bisnllite of soda at 115* Baunu': or of a solution of sullite of soda of 30 Baume or one hundred and eighty kilograms of hydrosullite of soda of Baum are treated for from eight to ten hours in an open copper vessel with a double bottom heated by steam and provided with an agitator until a sample taken from the mass is easily soluble in cold water.

0. Soluble qucbracho extracts may also be obtained by extracting the quebracho-wood in presence of bisulfite or sultite of soda for instance, by boiling under or without pressure one thousand kilograms of quebracho-wood with water to which has been added one hundred and ten to one hundred and thirty kilograms of bisulfite of soda (35 Baum) or crystallized neutral sultite of soda and evaporating the decoction until it tests 25 to 30 Bauni.

In every case, working as at ab 0, the extract is perfectly soluble in cold water and tans quicker than the quebracho extracts generally known. The leather becomes softer and of a much paler color of a pleasant pink shade. The palest product is obtained as described at a.

Example II: For the manufacture of a hemlock extract readily soluble in cold water from usual hemlock extract:

The ordinary hemlock extracts (which are difricultly soluble in cold water) are changed into soluble extracts by the same processes as used for quebracho extractsthat is to say, working as described at a and b of Example I. The hemlock extract thus treated dissolves readily in cold water and has to usual hemlock extracts comparatively the same advantages as soluble quebracho has to usual quebracho.

The weights and temperatures mentioned in our description may be altered, of course, to some extent, and sulfites, bisulfites, and hydrosulfites of potash and of ammonia may be used instead of the sodium salts.

The reaction by which the diificultly-soluble extracts are converted into a readily-soluble condition is dependent upon the amount of sulfite and bisulfite employed and the heat under which the reaction is conductedthat is to say, that with equal additions of bisulfite the extent of the reaction increases on an average with the temperature and that at equal temperatures the extent of the reaction increases as the amounts of sulfite or bisulfite employed and also that the extent of the reaction is dependent to a certain extent upon the time of duration of the same. For instance, after a period of, say, six hours duration there is very little further change noted after a period of eight hours duration.

By the above-described treatment with a salt of sulfurous acid under heat and pressure resinous and comparatively insoluble tanning extracts are converted into soluble extracts containing resinates of the soda or other base used.

Leather tanned with our improved extracts is characterized by its clearer color and greater pliability than that obtained with the ordinary extracts, while at the same time its pores are not filled with foreign matter and impurities present in the ordinary extracts.

The great solubility imparted as a result of our process appears, according to investigations made upon the extracts, to be due to the presence of chemically-combined sulfur as a sulfonic group, (SOSPL) which is not eliminated by heating the extract with sulfurous acid.

Having thus described our invention, the following is what we claim as new therein and desire to secure by Letters Patent:

1. The process of treating tan-wood extracts of the character described which consists in heating said extracts with a salt of sulfurous acid in a manner and to an extent to cause the tanning principles of the extracts to combine with the acid constituent of the salt to produce an extract readily soluble in water.

2. The process of treating extract of quebracho-wood to produce a tanning'extract which consists in heating said extract with a salt of sulfurous acid in a manner and to an extent to cause the tanning principles of the extract to combine with the acid constituent of the salt to produce an extract readily soluble in water.

3. The process of treating extracts of quebracho-wood to produce a tanning extract soluble in water, said process consisting in heating said extracts with a salt of sulfurous acid at a temperature of 100 centigrade and above for the period of from six to eight hours.

L. A tanning extract readily soluble in cold water and giving a clear solution therewith and containing chemically-combined sulfur.

5. An extract of quebracho for tanning, said extract containing the normally resinous and diflicultly-soluble constituents in a condition soluble in cold water. I

6. A tanning extract containing the tanning constituents of quebracho-wood, said extract readily soluble in cold water giving a clear solution therewith and containing chemically-combined sulfur.

7. A tanning extract consisting in the product of the reaction of a sulfite or bisulfite upon a normally resinous and difficultly-soluble tan-wood extract said product being readily soluble in cold water and containing chemically-combined sulfur.

ROBERTO LEPETIT. ERNESTO TAGLIANI.

Witnesses:

HENRY OPYZoTE, CLEMENTE GINEZETTL