New or Improved Leather and Process and Apparatus for Manufacturing the same.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
A New or Improved Leather and Process and Apparatus for
Manufacturing the same.
I, EMILE MAERTENS, of 49, Westminster Street, Providence, Rhode Island,
United States of America, Manufacturer, do hereby declare the nature of this
invention to be as follows:-
My invention relates more essentially to a process of treating hides, skins
or other animal substances suitable to be made into leather, with a liquor
containing one or more oxide or oxides of a metal and carbonic acid.
The
invention also embraces a new article and a novel bath.
It is well known that the carbonates of metals which have tawing or leather
forming properties, such as manganese, iron, chromium etc., are insoluble or
sparingly soluble in water and that freshly precipitated metal carbonates are
more soluble in the presence of soluble bi-carbonates or in the presence of car-
bonic acid also that the solubility of metal carbonates in water, not only
exists, but is increased when the water is saturated with carbonic acid, and
especially with carbonic acid under pressure.
In carrying out the process, the material to be treated is placed in a recep-
tacle of suitable construction and therein brought in contact with a solution
of metal oxide or oxides, metal carbonate or carbonates (or a mixture of these)
and carbonic acid.
By preference, the solution is saturated and in the presence of an excess
of the metal compound or compounds referred to above, and saturated with
carbonic acid under pressure (so as to increase its solubility) and thus as fast
as the metal carbonate or carbonates is or are being absorbed by the material
under treatment, an equivalent quantity is being dissolved by the liquid, from
the precipitated reserve.
Having an excess of metal oxide and carbonic acid present and the solution
being in continuous contact with the material being treated, any desirable
degree of metal oxide in combination with animal substance is obtainable.
The following example only illustrates a process and style of apparatus which
may be used in carrying out this invention:
The various elements of the apparatus are provided wherever necessary,
with suitable valved inlet and outlet pipes, as well as with gauges, sight glasses.
thermometers, drain or pet cocks, etc. and the method of operating it is as
follows:-
The hides or skins being in suitable condition to be treated are suitably
nacked in a receptacle or vat which has been hermetically closed by screwing
down its cover and a reservoir is suitably filled with water containing carbonic
acid and chromium hydroxide or other tawing agents in solution, and a suitable
quantity of the undissolved or precipitated tawing material or agent is left
resting on its bottom. A pump is made to draw CO₂ gas from a holder through
pipes and valves and discharges the same into the top of reservoir through

page_text: further pipes and valves. Valves are now opened so that the liquid from
the tank can pass into the vat driving before it the air which it contains and
which escapes through the valve into the atmosphere. When the vat is full
its air relief valve is closed and other valves are opened to cause the liquid to
flow back into the tank and when it has dropped to a level in the rat just
below that of the pipe through which it is drawn off, pressure is allowed to
accumulate in both tanks to the required degree when the aforesaid pump is
slowed down and another pump is started drawing the liquid from the tank
and injecting it into the vat by other pipes. The valves are then so mani-
pulated as to allow the liquid from the vat to flow back to the tank and enter
the latter at the bottom below the line where the undissolved chromium
hydroxide is stored and whence it flows back to the second pump and vat. This
circulation is kept up until the hides or skins are sufficiently treated but the
first pump is stopped as soon as the liquid is saturated with carbonic acid and
the required pressure has been obtained.
When the hides or skins have been sufficiently treated communication is
established between the top vat and tank. The second pump is now made to
re-transfer all the liquid contained in the vat back into the tank and when this
is accomplished, the pump is stopped and all valves previously opened are
closed, except one. Now by opening a valve the pressure is relieved from
the vat and the gas contained therein under pressure returns to the holder,
the balance being pumped out if desired by the first pump. When this is
finished the first pump is stopped, all valves previously opened are closed and
the valve on the cover of the vat is opened for the admission of air, then the
cover is lifted from the vat and the hides or skins therein contained are then
withdrawn to be subjected to the finishing operation.
This process can, of course, he carried on in the open, with a clear liquor
or with a liquor carrying some metal compound or compounds is suspension,
but on account of the less degree of saturation obtainable and the greater
loss of CO, it is slower and more costly.
In some instances I find it advantageous to first impregnate the material
being treated, with the tawing solution in vacuo, in which case a vacuum is
made in the vat or means of a pump before the introduction of the liquid,
the air exhausted being discharged in the atmosphere.
The leather produced by my process is composed essentially of animal matter
combined with a metal oxide or oxides, or metal hydrate or hydrates or metal
carbonate or metal carbonates and is free from any acid corrosive to the animal
substance in contradistinction to leather produced by other processes hereto-
fore in use.
One of the most objectionable features in processes where metal compounds
are used in the production of leather is the presence of acids combined with
the metal. To overcome the objectionable and injurious effects of such acids
during the process of manufacture or in the finished product, is a matter of
considerable concern to the tanner. The present process completely overcomes
the obnoxious action of such acids by replacing them by carbonic acid which,
it is known, has no injurious action upon animal substance.
It will be observed that in my process none of the tawing agent is used
except that taken up by the hides. Furthermore, my process is a
one bath
process " in contradistinction to the two bath process ordinarily used in tawing
and hence the process is not only extremely simple but there is a minimum of
labour expended in handling the hides. It will be obvious that various advan-
ages results from using a bath of constant or uniform strength.
Dated this 28th day of August 1899.
HERBERT HADDAN & Co..
Agents to Applicant.

page_text: COMPLETE SPECIFICATION.
A New or Improved Leather and Process and Apparatus for
Manufacturing the same.
I, EMILE MAERTENS, of 49, Westminster Street, Providence, Rhode Island,
Tnited States of America, Manufacturer, 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: -
My invention relates more essentially to a process of treating hides, skins
or other animal substances suitable to be made into leather, with a liquor con-
taining one or more oxide or oxides of a metal and carbonic acid. The inven-
tion also embraces a new article and a novel bath.
It is well known that the carbonates of metals which have tawing or leather
forming properties, such as manganese, iron, chromium, etc. are insoluble or
sparingly soluble in water and that freshly precipitated metal carbonates are
more soluble in the presence of soluble bi-carbonates or in the presence of
carbonic acid: also that the solubility of metal carbonates in water, not only
exists, but is increased when the water is saturated with carbonic acid, and
especially with carbonic acid under pressure.
In carrying out the process, the material to be treated is placed in a recep-
tacle of suitable construction and therein brought in contact with a solution
of metal oxide or oxides, metal carbonate or carbonates (or a mixture of these)
and carbonic acid.
By preference, the solution is saturated and in the presence of an excess of
the metal compound or compounds referred to above, and saturated with car-
bonic acid under pressure (so as to increase its solubility) and thus as fast as
the metal carbonate or carbonates is or are being absorbed by the material
under treatment, an equivalent quantity is being dissolved by the liquid, from
the precipitated reserve.
Having an excess of metal oxide and carbonic acid present and the solution
being in continuous contact with the material being treated, any desirable
degree of metal oxide in combination with animal substance is obtainable.
The following example only illustrates a process and style of apparatus which
may be used in carrying out this invention and referring to the accompanying
drawing, which shows a general elevation of said apparatus:
A is an ordinary gas holder for storing CO₂ gas, and capable of vertical
motion in the tank a.
Bis a reservoir used for storing and compounding the treating or tawing
solution.
C is the closed receptacle or tank in which the hides skins or other material
are treated.
D-is a pump for pumping or compressing gas.
E is a pump for pumping and circulating the liquor.
The various elements of the apparatus are provided wherever necessary. with
suitable valved inlet and outlet pipes, as well as with gauges, sight glasses,
thermometers, drain or pet cocks, etc., and the method of onerating it is as
follows:-
:-
The hides or skins being in suitable condition to he treated and having been
suitably packed in the receptacle or tank (which has been hermetically closed

page_text: by screwing down cover c and the reservoir B being suitably full of water
containing carbonic acid and chromium hydroxide or other tawing agents in
solution, and having a suitable quantity of the undissolved or precipitated
tawing material or agent resting on its bottom just below the line b, the pump D
is started and is made to draw CO₂ gas from the holder A through pipe 100
valve 1 and pipe 101, and to discharge the same into the top of reservoir B
through pipe 102, valve 2 pipes 103, 104 and valve 3. Valves 4 and 5 on
pipe 105 are now opened as well as valve 6 on top of the cover c of the tank C
and the liquid from tank B passes into tank C driving before it the air which
it contains and which escapes through valve into the atmosphere. When
tank C is full valve 6 is closed and valves 8, 9 and 10 on pipe 106 are opened,
this causes the liquid in C to flow back into B and when it has dropped to a
level in C just below that of pipe 106, valve 5 on pipe 105 is closed and the
pressure is allowed to accumulate in both tanks, to the required degree, when
pump D is slowed down and pump E is started drawing liquid from tank B
by way of valve 4, pipes 105 and 107 and injecting it into tank C by way
of pipes 108 and 109, valve 11, pipe 110 and pipe 105 to the right of valve 5.
Valve 10 on pipe 106 is now closed and valve 12 on pipe 111 is opened. thus
allowing the liquid from tank C to flow back to tank B and enter the latter
at the bottom, below line 6 where the undissolved chromium hydroxide is
stored and from whence it flows back to pump E and tank C through valve 4
on pipe 105 pipes 108, 107, 109, valve 11 pipe 110 etc. This circulation is
kept up until the hides or skins are sufficiently treated, but the pump D is
stopped as soon as the liquid is saturated with carbonic acid and the required
pressure has been obtained.
When the hides or skins contained in C have been sufficiently treated valve 10
on pipe 106, valve 13 on pipe 109 and valve 5 on pipe 105 are opened whereas
valve 12 on pipe 111 valve 11 on pipe 109 and valve 4 on pipe 105 are closed.
Communication is thus established between the top of B and C through valves 8,
9 and 10 on pipe 106 and between the bottoms of B & C through valve 5,
pipes 105 & 107 pump E, pipes 108 and 109, valve 13 and pipe 111. The
pump E is now made to re-transfer all the liquid contained in C, back into B
and when this is accomplished, the pump E is stopped and all valves previously
opened are closed, except valve 8 on pipe 106. Now by opening valve 14 on
pipe 112 the pressure is relieved from tank and the gas contained therein
under pressure returns to holder A via pipe 112, 113, 114 and 115, the balance
being pumped out if desired, by pump D by opening valve 15 on pipe 116 &
valve 16 on pipe 118 the said pump drawing the gas from tank C through
valve 8, pipe 106. valve 14, pipes 112, 113, 103, 117. 116, valve 15 and pipe 101
and discharging it into holder A through pipe 102. valve 16 pipes 118 114
and 115. When this is finished pump 1) is stopped, all valves previously opened
are closed and valve 6 on cover c of tank C is opened for the admission of air.
then the cover c is lifted from tank C and the hides or skins therein contained
are then withdrawn to be subjected to the finishing operation.
This process can, of course, be carried on in the open, with a clear liquor
or with a liquor carrying some metal compound or compounds in suspension,
but on account of the less degree of saturation obtainable and the greater loss
of CO₂ it is slower and more costly.
In some instances I find it advantageous to first impregnate the material being
treated. with the tawing solution in vacuo, in which case a vacuum is made in
the tank by means of pump E before the introduction of the liquid from B.,
the air exhausted being discharged in the atmosphere through valve 17 on
pine 118.
The leather produced by my process is composed essentially of animal matter
combined with a metal oxide or oxides, or metal hydrate or hydrates or metal
rabonate or metal carbonates and is free from any acid corrosive to the

page_text: animal substance in contradistinction to leather produced by other processes
heretofore in use.
One of the most objectionable features in processes where metal compounds
are used in the production of leather is the presence of acids combined with
the metal. To overcome the objectionable and injurious effects of such acids
during the process of manufacture or in the finished product, is a matter of
considerable concern to the tanner. The present process completely overcomes
the obnoxious action of such acids by replacing them by carbonic acid which,
it is known, has no injurious action upon animal substance, is non corrosive
and soluble in water.
It will be observed that in my process none of the tawing agent is used
except that taken up by the hides. Furthermore, my process is a
one bath
process" in contradistinction to the two bath process ordinarily used in tawing
and hence the process is not only extremely simple but there is a minimum of
labor expended in handling the hides. It will be obvious that various advan-
tages result from using a bath of constant or uniform strength.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
1. The process of converting hides, skins and other animal substance into
leather which consists in subjecting them to the action of a tawing agent or
tawing agents held in solution by carbonic acid, substantially as described.
2. The process of converting hides, skins and other animal substance into
leather which consists in subjecting them to the action of a lawing agent or
tawing agents held in solution by carbonic acid under pressure, substantially
as described.
3. The process of converting hides, skins and other animal substances into
leather which consists in subjecting them to the action of chromic hydroxide or
carbonate held in solution by carbonic acid, substantially as described.
4. The process of converting hides, skins and other animal substances into
leather which consists in subjecting them to the action of chromic hydroxide
or carbonate held in solution by carbonic acid under pressure, substantially
as described.
5. A tawing bath consisting of suitable tawing agents as the oxides, car-
bonates or bi-carbonates of metals dissolved in carbonic acid, substantially as
described.
6. A tawing bath consisting of suitable tawing agents as the oxides, car-
bonates or bi-carbonates of metals dissolved in carbonic acid under pressure,
substantially as described.
7. A tawing bath consisting of chromic hydroxide or carbonate dissolved
in carbonic acid, substantially as described.
8. A tawing bath consisting of chromic hydroxide or carbonate dissolved in
carbonic acid under pressure, substantially as described.
9. The improved process of converting hides and skins into leather which
consists in subjecting them to the action of a tawing bath the strength of which
remains constant throughout the process, substantially as described.
10. The improved process of converting hides and skins into leather which
consists in subjecting them to the action of a tawing bath which remains
saturated with the tawing agent or agents throughout the entire process.
.11. As an article of manufacture the new leather herein described.
12. As an article of manufacture the new leather made by the process herein
described.
13. As an article of manufacture the leather produced from hides, skins or
other animal substance, by the incorporation therewith of a metal compound or of
metal compounds dissolved in a solution of carbonic acid and characterised by
the combination of the animal substance with a metal oxide or oxides; metal

page_text: hydrate or hydrates, metal carbonate or carbonates or mixtures of these, and
its freedom from any acid corrosive to the animal substance, substantially as
described.
Dated this 24th day of May 1900
HERBERT HADDAN & Co.,
Agents to Applicant, 18, Buckingham Street, Durand, London.