AN IMPROVED METHOD OF TREATING FIBROUS PLANTS IN ORDER TO OBTAIN FIBRE FOR PAPER MAKING, and for Textile and othER PURPOSES."
Year: 1882

page_text: LETTERS PATENT to Carl Daniel Ekman, of Sweden, but now of 571/, Old
Broad Street in the City of London, for an Invention of "AN IMPROVED
METHOD OF TREATING FIBROUS PLANTS IN ORDER TO OBTAIN FIBRE FOR
PAPER MAKING, and for Textile and othER PURPOSES."
PROVISIONAL SPECIFICATION left by the said Carl Daniel Ekman at the
Office of the Commissioners of Patents on the 7th February 1882.
CARL DANIEL EKMAN, of Sweden, but now of 571, Old Broad Street, in the
City of London. "AN IMPROVED METHOD OF TREATING FIBROUS PLANTS IN
ORDER TO OBTAIN FIBRE FOR PAPER MAKING, AND FOR TEXTILE AND OTHER
PURPOSES."
My Invention relates to a method of treating plants, other than wood, by a
process similar in principle or chemical reactions, (but varying in proportions
and conditions) to that described in the Specification of a Patent granted unto me
and bearing date 13th July 1881, No. 3062, as applied only to wood.
The method now to be described differs considerably, not only for different
plants, according to their respective peculiarities and the amount of difficulty
found in dissolving the incrusting matter which they contain, but also according
to the different purposes to which the resulting fibre is intended to be applied.
It will therefore be convenient to divide the description into two main parts: that
is to say, first, with reference to the production of fibrous material suitable for
paper making and similar purposes; and, secondly, to the obtaining of filaments or
long fibre adapted for spinning, weaving, and such like purposes.
Before entering however on such description, it may be as well to state a few.
points of a more general nature with reference to the treatment of fibrous plants
in distinction from that of wood.
When the incrusting matter in plants is required to be completely dissolved, the
treatment is somewhat similar to that of wood, except that in general it is not
necessary to crush the plants before-hand, and they can be cut into pieces or not,
b

page_text: as found convenient. The boiling differs from that of wood, in that neither so
strong chemicals nor so high pressure are essential to obtain good results, and
therefore for the sake of economy both the quantities of chemicals and the pressure
may be considerably diminished.
In proportion as the pressure required is below that used for wood, the total
duration of the whole boiling process will necessarily be shortened, because the
maximum pressure will take less time to reach. But in all cases it will generally
be found advisable to maintain the maximum pressure for about the same length
of time.
I will now, by way of illustration, describe the process for treating straw and
esparto, in order to obtain fibre for paper making. After the raw material has
been suitably cleaned, and, if desired, cut into pieces, it is put into a boiler lined
with lead or other material capable of resisting the action of the chemicals, and in
such quantity that the said fibrous material may be completely covered by liquid
during the whole time of boiling. The solution used may contain only about
0.45 per cent of magnesin or soda, and about 0.85 per cent of sulphurous acid,
although generally a somewhat stronger solution is preferable. Then steam is
turned into the jacket, and the whole is or may be heated so that in three or four
hours the inner boiler has reached a pressure of 50 pounds to the square inch, and
it may remain at this pressure for about three hours. A little steam and gas may
be blown off, but this is not usually necessary unless a higher pressure than
50 pounds be employed.
When the boiling is complete the steam is blown off, and the contents of the
boiler are turned out. The fibre thus obtained is then washed and treated in tho
usual or any other suitable way.
The strength of chemicals, pressure, and duration of boiling, are varied as
required, according to the extent or degree to which the incrusting matter is to be
dissolved. Plants which are compact, woody, or resinous, requiring more vigorous
-treatment-than those which are soft and free from resinous matter.
With reference to the treatment of fibrous plants (such-as-hemp, flax, and jute,)
in order to obtain fibre suitable for textile purposes, the raw material employed
must consist of such plants or parts of plants as contain fibres of sufficient length
and are otherwise suitable for such purposes. In the preparation of fibre for
spinning and weaving, the operation can, with many plants, be conducted in such
a way that the fibres are either practically freed from incrusting and gummy
matter, or only partially so. When only partially freed, the fibres or filaments
more resemble those obtained by the ordinary method, and for this reason it may
be advisable to prepare the fibres ordinarily in this manner or condition, since they
will then be more suitable to be treated by the same machines. And this is to be
effected by diminishing the strength of the chemicals, pressure, and duration of
boiling, to a suitable extent.
On the other hand, if it is desired to prepare fibres wholly freed from incrusting
or gummy matter, greater strength of solution, pressure, and duration of boiling
must be used.
If the plants are compact, woody, or resinous, a more vigorous treatment must
be resorted to in both cases.
When it is desired to subject plants to a comparatively gentle treatment, in
order to obtain long fibres or filaments which retain a part of the incrusting or
gummy matter, this point may be attained by using a more basic solution, or by
adding to it magnesia in a finely divided state.
The stems or plants whether intended to be partially or wholly freed from the
incrusting or gummy matter, are, by preference, bound up in sheaves or bundles,
placed in a suitable boiler, covered with the solution, and held down by perforated
leaden plates, after which the boiler is closed with its cover, and heated by the
admission of steam into the jacket, so as to carry on the process of boiling as
required.
Textile fibre of different colour, appearance, and quality, may be obtained from

page_text: the same raw material, by subjecting it to treatment more or less severe in
respect of the strength and composition of chemicals, degree of pressure, and
duration of boiling.
In treating flax, for example, either fine, white, soft, silky but short fibres can
be obtained, or coarser, darker, stiffer, but longor fibres or filainents, with the
different gradations lying between these extremes, all depending on the treatinent
being varied and adapted in the manner referred to. If the solution used contains
1.4 per cent of magnesia and 4.2 per cent of sulphurous acid, and the boiling is
carried on with about 15 pounds pressure for about two hours and a half, coarser
filaments, of a darker colour, are obtained; but if the boiling is carried on with
30 pounds pressure for about 3 hours, the filaments obtained are finer, more flexible,
of improved appearance, and rather lighter in colour. A good result can even be
obtained by using a solution containing only 0.2 per cent of magnesia and
0.8 per cent of sulphurous acid, and boiling about three hours with 40 pounds
pressure.
Even sulphite of magnesia (the single salt) may be used, but, since this salt is
little soluble in water, a salt is preferred containing so much sulphurous acid that
it dissolves easily in the requisite or a less quantity of water. When this neutral
salt is used it is strewn on the flax as it is placed in the boiler so that it may be
pretty evenly spread, and then the boiler is afterwards filled up with water to the
same height as when a solution is used. Two per cent of single sulphite of
magnesia, and boiling for three hours with 50 pounds pressure, will yield fibre of
a fair quality.
For obtaining filaments that are soft, silky, lustrous, and of pale colour, the
boiling is or may be carried on with 70 pounds pressure for about three hours, with
a solution containing 1.6 per cent of magnesia and 3.8 per cent of sulphurous acid,
and (mixed with the flax) about one per cent of weight of the water of caustic
magnesia finely divided.
When only a small proportion of the incrusting matter is required to be dissolved,
very small quantities of the chemicals may be used. Even 0.3 per cent of the
water's weight of neutral sulphite of magnesia has a perceptible effect, but as a
rule it is preferred to have not less than one per cent of this salt. A solution of
0.03 per cent of magnesia and 0.1 per cent of sulphurous acid can be used, but a
stronger solution is preferred.
Even as small a pressure as three pounds will have some effect, but it is advisable
to fix the minimum at 10 pounds.
The foregoing examples for the treatment of flax will serve as a guide for the
treatment of other plants containing fibre suitable for textile purposes, especially
hemp. In distinction from the preparation of fibre for paper making, it is better
to use too low than too high a pressure, in order to preserve the strength of the
filaments as required. It being generally understood that pressure has a great
effect on the solution of the gummy and incrusting matters of all fibrous materials.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Carl Daniel Ekman in the Great Seal Patent Office on tho
4th August 1882.
CARL DANIEL EKMAN of Sweden but now of 57 Old Broad Street in the
City of London. "AN IMPROVED METHOD OF TREATING FIBROUS PLANTS IN
ORDER TO OBTAIN FIBRE FOR PAPER MAKING AND FOR TEXTILE AND OTHER
PURPOSES."
My Invention relates to a method of treating vegetable fibrous substances (other
than wood) by an improved process based upon that described in the Specification
of a Patent granted unto me and bearing date thirteenth July one thousand
eight hundred and eighty one No. 3062, as applied only to wood; my improved
process being applicable to fibrous plants in general. The method now to be
described will require to be varied in details for different plants according to their
respective peculiarites and the amount of difficulty found in dissolving the matter
incrusting the fibres which they contain, and which it is required to remove, and
also according to the different purposes to which the resulting fibres are intended
to be applied.
26
"
In the following description I use the term ultimate fibres to express the
condition in which the individual fibres are when they cease to be held or bound
together by the natural ngglutinating substance; and "filaments" when the
solution of this agglutinating matter has been so far incomplete that the ultimate
fibres remain more or less glued or cemented together in groups or bundles.
When I state the percentage of chemicals, 1 wish to be understood as referring
to the proportions between their weight and-the-weight-of-tho-water_used_in_
forming the boiling liquid.
Before entering on a precise description of the process as applied to particular
substances, it will be convenient to state a few points of a general nature with
reference to the treatment of fibrous plants in distinction from that of wood.
In general it is not necessary to crush the plants proposed to be treated before
boiling, and they can be cut into pieces or not as may be desirable. The only
necessary conditions in this respect being that the boiling liquid may easily
permeate them, and yet that the circulation of the liquid in the boiler be not
entirely prevented.
It will be generally preferable to remove from the plants the roots and such
other parts as will neither dissolve nor produce fibre of the kind or kinds desired,
as well as dirt and foreign substances.
A very convenient form of boiler is that fully described in the Specification of
iny said former Patent, but any boiler would be suitable which enabled the
following conditions to be complied with, viz', that the boiler is capable of gradual
heating, constructed of or lined with a substance capable of resisting the action of
the chemicals, sufficiently strong to resist the requisite pressure, complete covering
of the fibrous material with the boiling liquid during the whole boiling process,
sufficient room at the highest part to form a steam space, and in this steam space a
valve or other equivalent arrangement for blowing off gas or steam. In treating
raw materials for the production of fibres for textile or similar purposes, the stems
or plants (whether intended to be partially or wholly freed from the incrusting or
agglutinating matter) are, by preference bound up in sheaves or bundles, in order
that the resulting fibre may not become knotted or tangled. The fibrous material
must be held down by perforated leaden plates or other suitable arrangement, in
order that they may not rise above the liquid during the boiling operation.

page_text: The fibrous substance having been placed in the boiler under the conditions
stated, a chemical solution or liquid such as is hereinafter referred to or water is
run or pumped into it to such an extent that it may completely cover the fibrous
materials during the boiling, and yet that sufficient room may be left to form a
steam space, a cover is then bolted on to the boiler and made tight by the usual
means. The boiler is then gradually heated by steam passed into the jacket or by.
other suitable means.
If it be desired to obtain ultimate fibres it will generally be advisable to operate
with solutions containing sulphurous acid and soda or magnesia in proportions
nearly approaching those of the bisulphites, the pressure exceeding seventy pounds
to the square inch, and that found most generally advantageous being eighty pounds
or thereabouts. In these cases it is essential to allow gas (and consequently steam)
to escape during the boiling operation, or the contents of the boiler will be
discolored or burnt.
In all cases when it is seen that the pressure in the inner boiler exceeds that in
the jacket (as shewn by steam gauges fitted for the purpose) it is advisable to allow
gas and steam to escape until the pressure in the inner boiler falls somewhat below
that in the jacket. The object being to allow so much of the sulphurous acid gas
set free during the boiling process to escape that the formation of the free sulphuric
acid may be entirely avoided for unless this be ensured discoloration or burning
will take place.
When it is desired to obtain filaments of good color strength and lustre the
operator can use (when magnesia is employed) either solutions of the bisulphite
with magnesia in powder in suitable proportions strewn among or mixed with the
fibre, or the single salt (ie. the sulphite) may be strewn among or mixed with the
fibre the boiler being charged with water.
The effect of working with the single salt or solutions of the bisulphite with
admixture of the base in powder (as compared with solutions of the bisulphite
alone) is that in this case the operator can work at high pressures so as to discharge
the colouring matter (so as to obtain strong filaments of good colour) without
entirely removing the agglutinating substance whereas when only solutions of the
bisulphite are employed both colouring and agglutinating matters are simulta-
neously dissolved. It is also generally preferable to use the solution of bisulphite in
conjunction with the base strewn on the fibre (as described) in preference to water
and the single salt because although the calculated proportions of acid to base in
the two cases may be really the same, in the one case the action of the bisulphito is
immediate and constant, whereas that of the sulphite (in consequence of its not
being readily soluble) is more slow and uncertain.
When soda is used the effects will be similar, but since both this base and its
salts are readily soluble, it will be easily understood that with this alkali solutions
only may be used.
I have stated above the general rules which should guide the operator, but in
order that I may make my meaning more casily understood, I will describe
here my process as applied to flax stalks when treated in a boiler such as is above
referred to for the purpose of producing different kinds of fibre.
When magnesia is used, about 2 per cent of the single sulphite of magnesia
should be mixed with the flax stalks, the boiler being charged with water to the
extent described and the pressure gradually raised to fifty or sixty pounds and
maintained at this pressure for about three hours, when lustrous filaments of a pale
color are produced.
If the quantity of single salt or sulphite be increased to about 4 per cent., and
the pressure raised to about seventy pounds, and there maintained for about five
hours, finer filaments will be obtained of a still paler colour and good lustre.
If a solution containing about 3-85 per cent of sulphurous acid and 1.6 per cent
of magnesia be used and there be further added to this solution or mixed with the
flax from 8 per cent. to 16 per cent. of magnesia in powder and the pressure be

page_text: gradually raised to about seventy five pounds and there maintained for from three
to four hours very fine filaments will be produced of an exceedingly pale colour
soft and with an excellent lustre.
In the examples above given it will be necessary in order to render the fibres
suitable for spinning and similar purposes to remove the woody matter by some
suitable mechanical method of scutching and heckling.
If the flax stalks be treated with a solution containing about 14 per cent of
magnesia and about 4 per cent of sulphurous acid and the pressure be gradually
raised to about eighty pounds and there maintained for about two hours the
colouring and agglutinating matters will be almost entirely removed so as to leave
ultimate fibres of a white colour. No scutching treatment will be necessary to
remove the woody and other matters from the clean fibre as these will have
become so finely divided that by a suitable washing arrangement they can be easily
removed. Considerable assistance in obtaining this result is given by the treat-
ment (after a preliminary washing of the fibre) with a very dilute solution of
sulphuric acid, which must subsequently be very carefully washed out. The fibres
hereby produced are white, and so far freed from incrusting and agglutinating
matters that they approach more nearly to pure cellulose, than those which
can be produced by one operation by any process hitherto known. They are
without further chemical treatment suitable either for paper making or for textile
purposes. The flax stalks may be treated by my process whether in a. ripo or
unripe state, so that ripe stalks from which the seeds have been removed and
which have been hitherto considered as comparatively waste products are mado
available for my purposes. In many cases when fibrous substances such as flax
and hemp stalks have been treated by my process the waste (consisting principally
of very short fibres or woody matter) removed from the longer fibres by washing
or by some mechanical process may be made available for paper making or similar
purposes.
The following is a good example of the treatment of a raw material for the
production of cellulose for paper making-Esparto (froed_from_roots_and_foreign_
substances) is boiled in a solution containing about 14 per cent. of magnesia and
about 45 per cent. of sulphurous acid. The pressure is gradually raised to from
eighty to eighty five pounds and maintained theroat from two to four hours. The
resulting fibre after being well washed in the usual way, consists of cellulose so
well freed from incrusting matter that it may be considered as practically pure.
It is of so white a colour as to be suitable (without further chemical treatment) for
the manufacture of good ordinary printing papers. It can be further bleached if
necessary by solutions of bleaching powder in the ordinary way, and thus made
available for finer kinds of paper.
Having now described my Invention of "An Improved Method of Treating Fibrous
Plants in order to Obtain Fibre for Paper Making and for Textile and other
Purposes" and explained the manner of carrying the same into effect, 1 hereby
declare that what I claim as of my said Invention is:-
First: The production from flax stalks and other similar fibrous vegetable
substances of ultimate fibres of practically pure cellulose, by one operation of
boiling under pressure in solutions containing sulphurous acid and magnesia or
soda, in about the proportions and under the conditions substantially as described.
Second: The production from alfa esparto and similar fibrous vegetable
substances of paper pulp (of a white colour) consisting of practically pure cellulose
by one operation of boiling under pressure in solutions containing sulphurous acid
and magnesia or soda in about the proportions and under the conditions
substantially as described.
Third: The production from fibrous vegetable substances of fibres or filaments
by boiling under pressure with sulphite of magnesia or soda substantially as
described.
Fourth: The production from fibrous vegetable substances of fibres or filaments

page_text: by boiling under pressure with sulphurous acid and magnesia or soda the base
being in quantity sufficient or more than sufficient to form the sulphite.
In witness whereof I the said Carl Daniel Ekman have hereunto set my
hand and seal the First day of August in the year of our Lord One
thousand eight hundred and eighty two.
Witness
WILLIAM SPENCE
8, Quality Court
Chancery Lane.
C. D. EKMAN. (L.S.)