Improvements in the Process of Liming Furs, Hair Skin, Skins, Hides, Pelts, or parts thereof.
Year: 1898

page_text: Date of Application, 4th Feb., 1898
Complete Specification Left, 5th Dec., 1893-Accepted, 4th Mar.,
1899
Improvements in the Process of Liming Furs, Hair Skin, Skins,
Hides, Pelts, or parts thereof.
We, ERNEST EDWARD MUNRO PAYNE, of Aylesbury, in the County of Buck
ingham, Analytical Chemist; JOHN PULLMAN, Manufacturer, and EDWARD
ENGLAND PULLMAN, Manufacturer, both of 17, Greek Street, Soho Square, in the
County of Middlesex, do hereby declare the nature of this invention to be as
follows;-
-
This invention consists essentially in acting upon raw or partially limed
materials by means of a weak solution of caustic soda (NaHO) or caustic potash
(KHO) or their carbonates, or a mixture of both in any proportion, according
to the ultimate degree of liming required, and the metathesis of this with
chloride of calcium (CaCl) in solution, or other suitable soluble salt of calcium,
so that Ca.2 (HO) (calcium hydrate) and CaCO3 (calcium carbonate) results.
This process may be reversed, that is to say, using the solution of a calcium
salt first, and the caustic or alkaline solution second.
In the case of furs or hair skins, where the lime or caustic alkali in solutions
possesses a deleterious action, we submit the furs to a sufficiently strong solution
of the calcium salt until they are saturated or imbued with it, and we then paint
the caustic or alkaline solution upon the flesh side of the skin, so that by per-
meation a perfect liming results without contact with the hair or fur. These
may then be dressed in any desired manner.
The quantity of deposited lime may be accurately regulated by variations in
the strength of the solution employed.
1000
EDWARDS AND Co.,
65 and 66, Chancery Lane, London, Agents for the Applicants.
Improvements in the Process of Liming Furs, Hair Skin, Skins,
Hides, Pelts, or parts thereof.
We, ERNEST EDWARD MUNRO PAYNE, of Aylesbury, in the County of Buck-
ingham, Analytical Chemist; JOHN PULLMAN, Manufacturer, and EDWARD
ENGLAND PULLMAN, Manufacturer, both of 17, Greek Street, Soho Square, in the
County of Middlesex, do hereby declare the nature of this invention, and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement, that is to say:--
This invention consists essentially in chemically producing calcium hydrate
or calcium carbonate in the substance of the skin itself, (instead of treating the

page_text: skin with these materials externally applied), by acting upon raw or partially
limed furs, hair skin, skins, hides, pelts or parts thereof, by means of a weak
solution of caustic soda (NaHO) or caustic potash (KHO) or their carbonates,
or a mixture of both in any proportion, according to the ultimate degree of lim-
ing required, and the metathesis of this with chloride of calcium (CaCl) in
solution, or other suitable soluble salt of calcium, so that Ca.2 (HO) (calcium
hydrate), or CaCO3 (calcium carbonate) is produced, in the substance of the skin
itself, and intimately combined with it.
It is obvious that, instead of chloride, or other suitable soluble salt of calcium,
a suitable soluble salt of magnesium, or of metals of the alkaline earths such as
barium, may be used, the metathesis which takes place (supposing, for instance,
that such a salt of magnesium is used) producing a magnesium, instead of a
calcium, compound, in the substance of the skin itself. The result is similar to
that obtained when calcium is used, and the "liming" process includes such
equivalent processes in which compounds of other salts of magnesium, or of
metals of the alkaline earths such as barium are obtained instead of those of
calcium.
This process may be reversed, that is to say, the solution of a calcium salt
may be used first, and the caustic or alkaline solution second.
In the case of furs or hair skins, where the lime or caustic, alkali in solutions
possesses a deleterious action, we submit the furs or hair skins to a sufficiently
strong solution of the calcium salt until they are saturated or imbued with it,
and we then paint the caustic or alkaline solution upon the flesh side of the skin,
so that by permeation a perfect liming results, without contact with the hair or
fur. These may then be dressed in any desired manner.
The quantity of deposited lime may be accurately regulated by variations in
the strength of the solutions employed.
The following description is in illustration of the method which we have found
very effective in putting our invention in operation; but it must be understood
that we do not confine ourselves exactly to the proportions of the several ingre-
dients, to the exact time occupied in the different processes, nor to the precise
methods of carrying out the operations:
Take 15 dozen sheep skins, the wool of which has been removed by any
process such as sweating or depilating with sulphide of sodium solution, and place
them in a revolving drum of about 300 gallons capacity, making 20 revolutions
per minute, and containing 120 gallons of distilled water at a temperature of
about 95° Fahrenheit, and holding in solution 10 lbs. of good commercial caustic
soda, sodium hydrate (NaHO).
<
Allow these skins to be revolved in the liquor for three hours, after which
period they will be swollen or plumped," but without the appearance or
characteristics of limed skins, since they do not contain lime, beyond the small
amount naturally present as a constituent of the raw skin.
Draw the skins from the drum and allow them to drain for a few minutes.
Then place the skins in the drum which has previously been emptied of its
former contents, and in which has been placed 14 lbs. of anhydrous chloride of
calcium in solution in 120 gallons of distilled water at a temperature of 95° Fah-
renheit. Allow the drum and its contents to revolve for about half an hour.
The skins will now present a totally different appearance and composition―
identical with fully "limed" goods.
After completion by copious washing with distilled water, the skins upon assay
do not yield sodium hydrate, but calcium hydrate, intimately combined with
skin matter.
It is necessary in the manufacture of certain classes of leather that calcium
carbonate (CaCO3) be present, but, owing to the insolubility of calcium carbonate
the latter cannot be directly introduced into the skin matter. By our process,
however, this is accomplished by the addition of sodium carbonate (Na₂CO₂) to

page_text: the caustic soda solution. Then, upon the metathesis with the calcium chloride
solution, the calcium carbonate is produced, intimately combined with the skin
matter. By similar means, also, we prepare, if required, certain other compara-
tively insoluble salts of calcium, such as sulphate or phosphate, intimately
combined with the skin matter, by adding the acid radicles in combination with
sodium, as neutral or alkaline salts, to the caustic soda solution; and by the
subsequent metathesis, from the addition of the solution of calcium chloride or
other suitable calcium salt, the desired insoluble calcium compounds are formed,
and are retained intimately in the skin matter, the soluble newly-formed sodium
compounds being removed readily by adequate washing.
The above process is identical in the case of deer skins, calf skins, hides, and
the like, but, as is well known, the amount of lime must be varied according to
the desire of the dresser or tanner.
The process first described is especially suitable for the liming of sheepskins,
the wool of which can be for the most part already removed by another process.
The concentration or strength of the materials used must be varied according to
the skins or fells treated.
It is advantageous that, in some cases, the skins should be treated with caustic
soda after (instead of before) their treatment with chloride of calcium solution;;
the "swelling" being reduced as much as possible, whilst to prepare them for
the ordinary tanning process but little of the ordinary treatment is required.
The quantity of lime which it is desired to introduce into the skins can be
increased by carbonate of soda being substituted for part of the caustic soda. As
already explained, by mutual decomposition during the subsequent treatment,
carbonate of lime and chloride of sodium are formed in the substance of the
skin. The latter salt can be easily got rid of by washing.
The following experimental tests of our process show the results obtained,-
the proportions of the ingredients used, and the order in which the different
processes were performed, being varied.
In one series of experiments, portions of skins, which for the unhairing process
were first soaked in water, were first treated in solutions of chloride of calcium
of different strengths (or degrees of concentration), and afterwards immersed in
soda lye, also of different strengths, and were allowed to remain there until the
hair could be easily removed from the skin.
In a second series of experiments, the processes were reversed, and the portions
of skin were first treated with a dilute solution of soda lye, and after they had
remained in it a certain time, they were removed and placed in a solution of
chloride of calcium. In the first series of experiments the following four different
degrees of strength of the chloride of calcium solution were used for soaking the
skins:-
After the different skins had remained for 5 hours in the solution of chloride
of calcium of the above strengths, four of these different samples were placed
in soda lye of 23 % Na₂O, and left there for 12 hours. From all four, the
hair could then be very easily removed.
Four other samples, which had also been treated with calcium chloride solu-
tion of different strengths, were then placed in soda lye of different strengths,
and in such manner that the samples from the less concentrated chloride of
calcium solution, were also placed in the more diluted soda lye.

page_text: After 12 hours' treatment all the samples could be easily unhaired. The
samples, which had been in the concentrated soda lye, were strongly swelled.
This swelling remained, even after 24 hours' washing in water, and the skins
so treated must be prepared for tanning by a macerating process, which removes"
the swelling.
The skins after washing should be tested for lime by treatment with diluted
hydrochloric acid, and show a distinct lime re-action, and thereby show that a
certain quantity of calcium hydrate has been formed by the action of the caustic
soda.
For some reasons, however, this method, by which the skins are treated first
with chloride of calcium and then with caustic soda, is less advisable on practical
grounds than the other method, in which the skins are first treated with caustic
soda and afterwards with chloride of calcium, as in the first. process an excess
of soda remains in the skins which it is very difficult to remove by washing,
whilst in the latter process the swelling of the skins and the excess of caustic soda
are easily removed by washing. In the second series of experiments the portions
of skins were first treated in soda lye and then in a solution of chloride of
calcium.
After remaining 12 hours in these soda lyes, all three specimens were immersed
in a solution of chloride of calcium of 1% CaCl. After 5 hours' immersion the
skins could be easily unhaired. The experiments were conducted at a tempera-
ture of 12° -15° Celsius.
If the skins or the liquid are agitated, as is done in tanneries, where the
solution and the skins are put into revolving drums, the unhairing process is
effected much more quickly.
Also, a quickening of the process is effected, as the temperature, instead of 15°,"
can be raised to 300-35°.
After the skins leave the chloride of calcium solution they are exactly similar
in appearance to similar skins which have been treated only with hydrate of
lime in the usual way. The swelling and the excess of caustic soda, are--as
already clearly explained-partly by the immersion in the calcium chloride
solution, and partly by the subsequent washing, easily got rid of. After thorough
prolonged washing, the presence of a sufficient quantity of lime can still be
proved.
In some cases, we add a small proportion of sulphide of sodium to the chloride
of calcium solution.
Considered from technical standpoints, the advantages attained by our im-
proved process over the ordinary liming in pits, are that we are able:-First,
Thoroughly to lime furs, hair skins, skins, hides, and pelts;
Second, To reduce largely the time occupied in the process of liming, it being
possible to completely perform the operation of liming hides for tanning in four
hours, whereas, by the method heretofore employed, at least ten days are generally
necessary;

page_text: Third, By operating with known weights of hide or skin, definite temperature,
strength of the solutions used, and time, to produce an exact liming result;
Fourth, To regulate the amount of salts remaining in the limed skin,-for
example, calcium carbonate, which for the purpose of tanning is undesirable,
as a hide or skin can be limed by this process and, in the result, be practically
free from this salt, whilst, on the other hand, for certain classes of leather this
salt is essential for the production of good leather, and by this process the desired
amount can be deposited intimately combined with the fibre. By the process
heretofore used the regulation of the amounts of insoluble calcium salts remain-
ing in the fibre, to almost any degree, is impossible.
Fifth, To prevent waste, as the quantity of lime used in the ordinary method
of liming goods is very considerably in excess of that required by the skins,
owing chiefly to the action of the carbonic acid gas of the atmosphere converting
the soluble hydrated oxide of calcium into the carbonate of calcium;
Sixth, To effect a saving in the processes of bateing and puiring, as the
sodium or other salts used in our improved process of liming being soluble, the
greater portion of them can be readily washed away, and consequently a very
much smaller quantity of bate or puir is required;
Seventh, To effect a reduction in cost, since there is little or no waste, and
the salts are recoverable.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is :-
1. In the process of liming furs, hair skins, skins, hides, pelts, or parts
thereof, the treatment of such materials, raw or partially limed, first with a weak
solution of caustic soda (NaHO) or caustic potash (KHO), or their carbonates,
or a mixture of both in any proportions, and the subsequent treatment with a
w to se to nos (CaCl2) or other suitable soluble salt of calcium,
so that calcium hydrate (Ca(HO)2) is formed in the substance of the skin itself,
substantially as described.
2.The process of treating such material, first with a solution of caustic
alkali or alkalis, and subsequently with a solution of a soluble salt of calcium,
so that calcium hydrate (Ca.2(HO)) is produced in the substance of the skin itself,
substantially as described.
3. In the process claimed in Claims 1 and 2, the treatment of the materials.
first with a solution of a salt of calcium, and subsequently with a solution of
caustic soda, or caustic potash, or their carbonates, or a mixture of both in any
proportions, substantially as described.
4. In the process of liming furs or hair skins, the treatment of such materials
with a solution of chloride of calcium, or other suitable soluble salt of calcium,
until they are saturated or imbued with it, and then painting the caustic or
alkaline solution upon the flesh side of the skin, so that by permeation a perfect
liming results, without contact with the hair or fur, substantially as described.
5. In the processes claimed in Claims 1, 2, 3, and 4, the use, instead of a
soluble salt of calcium, of a suitable soluble salt of magnesium or of metals of
the alkaline earths, such as barium. substantially as described.
Doted this 4th day of December 1898
Dated this 4th day of December 1898
EDWARDS AND CO.,
Chartered Patent Agents,
65 and 66, Chancery Lane, London, Agents for the Applicants.