Improvements in Tanning.
Year: 1890

page_text: Date of Application, 21st July, 1890
Complete Specification Left, 19th Nov., 1890-Accepted, 7th Feb. 1891
PROVISIONAL SPECIFICATION.
Improvements in Tanning.
I, JEAN EMILE PUJOS of 123 Rue de la Tour, Paris, do hereby declare the
nature of this invention to be as follows:-
Numerous investigations have heretofore been made with the object of effecting
improvements in the art of tanning. The great number of methods or processes,
which have been invented and abandoned have shown how difficult it is to effect
tanning in a short time and in an efficient manner and such as has heretofore taken
many mouths to effect.
Now the present invention enables the tanning process to be effected in
extremely short periods and at greatly diminished cost, thereby ensuring rapidity
and economy.
The process consists primarily in an unhairing process which enables the leather
to preserve all the animal fibres.
With this object, I employ lime, one of the alkaline earths, in general use.
Alkaline earths notwithstanding all the operations to which the hide is subjected,
never combine completely with the animal fibres, and the lime subsequently prevents
the tanning from taking place under good conditions; still lime is necessary for
completely removing the grease and hair, and its employment becomes practical
and advantageous in tanning, if another alkaline is brought to act upon the animal
fibre, thereby causing chemical reactions so as to neutralize the action of the lime,
and acting upon and transforming all portions of the fibre that have not entered
into combination; the result being that instead of interfering with the tanning, the
new product obtained imparts a greater amount of resistance and a greater amount
of suppleness to the leather, with a good yield.
After the mhairing operation by the use of lime, 1 subject the hides or skins
(of sheep, calves, cows, bullocks, bulls, horses &c.) to the preparatory operations of
removing the blood, freshening and fulling and softening.
Then, on removal from the lime pit, I rinse the hides or skins with clear water;
I remove the flesh from them, and I give them a working or dressing on the hair
side with the view of removing at the same time as the dirt, the portions of wool or
hair that remain after the unhairing operation.
The hides or skins are then immersed into and allowed to remain in a bath
acidulated with oxalic acid, care being taken that the acidity of the bath remains
the same after the immersion of the hides.
The hides or skins are then removed from the bath, and are worked or dressed on
the hair side and on the flesh side; they are cleansed either by hand or by machinery
from the impurities which they may contain until the cleansing water is clear, and
the acidity has almost disappeared.
The hides are then ready to be subjected to the tanning baths of converted tannin
which constitute an important feature of the present invention.
I will not describe the method of preparing the liquors, of 6, 8 or 10 degrees,
which are to be subsequently converted according to my process; I will take for
example, either liquors of 6 degrees, or extracts of 20 and 25 degrees.
To 100 kilogs. of extracts of 25 degrees, of oak, chestnut or any other kind, are
added 100 kilogs. of clear water, in order to enable the extracts to be more easily
stirred.
15 kilogs. of commercial ammonia are then added and the mixture is stirred until
complete absorption has taken place. Finally, S kilogs. of ordinary sulphuric acid
are added, and the stirring is repeated until complete mingling is effected. The
product thus obtained is what I term the "converted tannin,”

page_text: If the extract of oak, chestnut et. of 20 degrees, be operated with, the proportions
are the following
Extract of oak or chestnut of 20 degrees
Clear water
Commercial ammonia
Commercial sulphuric acid
=
100 kilogs.
100
"
12,100
6,900
"
33
The hides placed in suitable receptacles, are first treated with liquors of tannin
converted, as above, of the weakest degree, then gradually with liquors of higher
degrees, until they are finally operated on with a tanning bath of converted tannin
of 4 or 5 degrees Beaumé. The skins are laid in a pit and are drenched or saturated
with liquor of converted tannin.
This new process has many advantages; it allows of the extracting of the
entire quantity of the active principles contained in the barks, liquors, extracts
and powders usually employed in tanning and of utilizing the tannin to the last
particle, which has not been capable of being done hitherto by any method so far as
I am aware.
Moreover, this process, besides the very great economy in first cost thereby
realized, enables the operation of tamming to be effected very quickly; sheepskins
can be tanned in two to three days; calf skins in twenty to thirty days; and the
skins or hides of cows, bullocks, bulls, &c., according to the quality and size, in a
period of two to three months. Hides thus tamed give the same yield and colour
as the best skins tanned in pits by old processes, and they have the same resistance
and suppleness as hides of superior quality.
It may also be stated that this process of converting tannin with ammonia
and sulphuric acid, is applicable to all tanning substances such for examples as the
oak, chestnut, sumach, scarlet oak, vallonia, the cæsalpina coriaria, the mangrove
or mangle &c.
Dated this 631-4
T.... 1000
J. E. PUJOS,
By L. W., per F. B.
Improvements in Tanning.
I, JEAN EMILE PUJOS, of 123 Rue de la Tour, Paris, France, do hereby declare
the nature of this invention and in what manner the same is to be performed to
be particularly described and ascertained in and by the following statement :-
Numerous investigations have heretofore been made with the object of effecting
improvements in the art of tanning. The great number of methods or processes
that have been devised and abandoned have shown how difficult it is to effect in a
short time and in an efficient manner tanning such as has heretofore taken many.
months to accomplish at comparatively heavy cost.
According to this invention, the tanning process can be effected in an extremely
short period and at greatly diminished cost, thus ensuring rapidity and economy.
The process, which is especially suitable for tanning soft leathers, consists,
primarily, in an unhairing process that enables all the animal fibres of the leather to
be preserved.
With this object employ lime, one of the earthy alkalines in general use.
Alkaline earths, notwithstanding all the operations to which the skin or hide is
subjected, never combine completely with the animal fibres, and the lime subsequently
prevents the tanning from taking place under favourable conditions; still it is
necessary for completely removing the grease and hair, and I have observed that its
use becomes practicable and favourable to the tanning operation if another alkali
(sulphate of ammonia) or oxalic acid is allowed to act upon the animal fibres, so
as to cause chemical reactions that neutralize the action of the lime, and which

page_text: substance acts upon and transforms all portions of the animal fibres that have not
entered into combination with the lime. The result is that instead of interfering
with the tanning, the new product obtained imparts a greater amount of resistance
and a greater amount of suppleness to the leather, and enables a good yield to be
obtained.
Before the unhairing operation by the use of lime, I subject the hides or skins
(of sheep, calves, cows, bullocks, bulls, horses &c.) to the preparatory operations of
removing the blood, freshening and fulling and softening.
On removal from the lime pit, I rinse the hides or skins with clear water; I then
remove the flesh from them, and give them a working or dressing on the hair side
so as to remove, at the same time as the dirt, the portions of wool or hair that may
have remained after the unhairing operation. The hides or skins are then immersed in
and allowed to remain in a solution of oxalic acid containing from 10 to 15 grammes
of oxalic acid to each hide. Care is taken that after each immersion of the hides,
the acidity of the bath remains the same.
The hides or skins are then removed from the bath, and are worked or dressed
on the flesh side and on the hair side; they are then cleansed, either by hand or by
machinery, from any impurities they may contain and until the cleansing water that
leaves then is clear and almost without acidity.
The hides or skins are then ready to be subjected to the tanning baths of converted
tannin which constitute an essential part of my invention.
In the case of heavy hides, I employ the methods of unhairing generally adopted
and then the hides are, on removal from the clear or running water tanks, treated in
baths of converted tanning.
I
I will not describe the known method of preparing the liquors of 4, 6, 8, or
10 degrees which have to be subsequently converted according to my process.
will take for example either liquors of 6 degrees, or extracts of 20 and 25 degrees,
such liquors or extracts being obtained with any suitable tanning substance.
To 100 kilogs. of extracts of 25 degrees, of any kind, such as oak, chestnut, or other
tanning substance, are added 100 litres of clear water, in order to enable the extracts
to be more easily stirred. 15 kilogs, of ammonia of commerce are then added, and
the mixture is stirred until complete absorption has taken place. Finally, 8 kilogs.
of the ordinary sulphuric acid of commerce are added, and stirring is renewed until
complete mixing has been effected.
The product thus obtained is what I term "converted tannin."
In operating with extract of oak, chestnut, or other tanning substance of 20 degrees,
the proportions are the following:
Extract of 20 degrees, oak or chestnut, 100 kilogs.
Clear water -
Commercial ammonia
Commercial sulphuric acid
-
100 "
12,100
6,900
"3
23
When using extracts of other degrees, the proportions of ammonia and sulphuric
acid vary accordingly and in a ratio which can be readily deduced from the
preceding data.
The hides or skins are placed in basins and treated first with liquors of tannin
converted as above, of the lowest strength, then gradually with liquors of higher
degrees until they are finally operated on with a tanning bath of converted tannin

page_text: quickly. Sheep skins can be tanned in two or three days; calf skins in twenty
or thirty days; and the skins or hides of cows, bullocks, bulls &c., according to
their quality and size, in a period of from two or three months.
Hides or skins tanned in this manner have the same yield and colour as the best
hides tanned in pits by old processes, and they have similar resistance and suppleness
to hides of superior quality.
It may also be stated that this process of converting tannin by means of ammonia
and sulphuric acid is suitable for all tanning substances, such for examples as oak,
chestnut, sumach, scarlet oak, vallonia, cæsalpina coriaria, the mangrove or
mangle &c.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what 1
claim is :-
1. The hereinbefore described improved method or process of tanning hides or
skins comprising the following successive operations vi. (a) effecting the removal
of blood, freshening, fulling and softening; (b) effecting the removal of the hair by
means of lime; (c) rinsing with clear water; reinoving the flesh, dirt and portions
of wool or hair that may have remained after the unhairing operation; (d) im-
mersing in a solution of oxalic acid; (e) working or dressing on both sides, and
cleansing by hand or by machinery; and (f) treatment in special tanning baths of
converted tannin, the conversion of the tannin for these baths being effected by
additions of ammonia aud sulphuric acid, in proportions determined by the nature
and the strength of the extracts employed.
2. The use in the process of tanning, of baths of converted tannin made by mixing
a tannin substance with water ammonia and sulphuric acid substantially as herein
described.
10.1
Nanamba 1890
J. E. PUJOS,
By L. W., per F. B.