Improvements in Bleaching.
Year: 1890

page_text: Date of Application, 18th Aug., 1890-Accepted, 20th Sept., 1890
COME LEIE
DILCIPATION.
Improvements in Bleaching.
We, HEINRICH THIES of Laaken near Barmen-Rittershausen, and EMIL HERZIG, of
Reutlingen, both in the Empire of Germany, Chemists, 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 :-
This invention relates to an improved process for scouring and bleaching cotton,
linen and other textile or fibrous material of vegetable origin and has for its purpose
to effect economy in time, working power, steam and chemicals and thereby cause
the waste waters to be quantitatively reduced and their noxious properties to he
mitigated, while at the same time prejudicial effects on the structure of the filament
are obviated.
To accomplish the purposes above referred to the materials to be scoured and
bleached are prepared with alkaline earths for their treatment in the scalding vessel.
Subsequently they are steamed and raised to a high temperature, whereby any free
oxygen is eliminated therefrom while the vegetable impurities and colouring matters
are reduced. The materials are then, while at a high temperature, impregnated with
caustic alkalis, which owing to the absence of oxygen and to the presence of bases
of alkaline earths, may be employed in a very strong concentration without destroying
the fibre or causing the fabrics to shrink.
Through the high concentration of the caustic alkalis an energetic action on the
fibrous material takes place. This action being maintained by compensating the
incipient saponification, that is to say, the weakening of the solution by continuous
concentration by evaporating the solution, while, for the purpose of producing a
uniform reaction, the liquid is subjected to a circulation accelerated by difference of
pressure.
Prior to treating the materials in the above manner they are caused to undergo a
successive impregnation with acid and alkali, for instance first with sulphuric acid
and subsequently with soda lye. This however, as is to be understood-is a process
well known and employed in bleaching. In order to increase the effect when treating
the material with acid, we use fluor-acid as an addition to the acid (sulphuric or
muriatic acid). Moreover for the purpose of effecting economy in acid at all, the
acidulated fibrous materials are steamed immediately before washing. Subsequently
the fibrous materials, freed by ablution from the acid, receive the alkaline
impregnation. After the action of the alkalis, whether they be a potash-soda,
or ammonia-compound, we utilize the alkaline condition of these fibrous materials
for simultaneously precipitating alkaline earths on the fibre during the ablution of
the alkalis.
After the described preliminary treatment the fibrous materials are subjected to the
first mentioned chief process, which consists in heating the fibrous materials alkalified
by the alkaline earths and adding thereto, while at a high temperature, the caustic
alkalis. Subsequently the scalding liquid is evaporated.
As mentioned above, the improved process does not entail any prejudicial effect
on the filament, which, when being treated with caustic alkalis, is rolled up in its
spiral twist, whereby the fabric assumes an inferior appearance; the preliminary
preparation with alkaline earths however completely neutralizes the noxious influence
of the caustic alkalis on the structure.
The improved process admits of the application of caustic alkalis in high
concentration without any risk of shrinking; it results moreover in a cellulose
of perfect chemical purity which as such can be employed not only for garments but
also for sanitary purposes and chemical products (for instance gun cotton)..
The improved process is conducted as follows:

page_text: The material to be scoured and bleached, is, according to its condition, first soured
or saturated directly with an alkali compound. This souring acidulation or
saturation with alkalis is performed in the manner usual with scalding processes and
serves for the known purpose. To enhance the effect of the acid, a slight addition of
fluor-acid is employed; thereby also especially silica compounds and such accessory
products that are not cellulose, for instance the cuticle, the lumen containing
proteine, liquefied membranes, gimming rinds, bast and cortical elements, are rendered
accessible for better solution.
In order to effect saving of acid and improve the action of the acid, the fibrous
material impregnated therewith is continually steamed after having been exposed to
cooling action. The steaming is effected by means of the usual machines, whereby
the fibrous materials are delivered of the property of allowing basic compounds to be
re-deposited thereon from weak inorganic solutions of salts.
The above preparatory treatment of the fibrous material with acid is repeated at the
finish as the last phase in the bleaching process after having subjected the material
to the usual chloric operation. In the case of fibrous materials which contain only
traces of inorganic compounds, souring in the last operation only is sufficient, the
treatment, with acid at the commencement of the process being dispensed with, while
thèse materials receive direct that first described treatment with alkali which is
otherwise subsequent on that with acid.
The initiatory treatment with alkali has for its purpose to soak or remove, prior to
the scalding operation, loosely adhering constituents, for instance size, pectine bodies
and dried-in vegetable juices.
In ordinary cases, the preparation with alkaline hearths is not effected in the
scalding vessel, but, when washing the fibrous materials treated with alkalis, certain
quantities of any solution of alkaline earths are added to the water. The otherwise
obstinately resistant contents of alkali in the fibre are thus casily exchanged
or converted into alkaline earths, and this small quantity of alkaline earths,
which is thus chemically precipitated on the fibre cannot be removed by steam or
water owing to its minimal solubility but remains in the fibre notwithstanding the
following operations.
The fibre therefore retains a weak and uniform alkalinity, and these alkaline earths
cause, when heating the material, the reduction of the vegetable impurities of the
colouring matters that is to say, of the fibre. The action of the earth-alkalified fibre
is energetically reductive and it not only completely absorbs, at the commencement
of boiling heat, the remainder of the oxygen of the air, but is also capable, for
instance, of converting indigo blue and azo colours into the known colourless
compounds. Thus it is possible to more casily dissolve the natural or incidentally
occurring colouring matters and to partly combine the same with the base of alkaline
earth. The fibre thus earth-alkalified is heated to above 100 degrees Centigrade and
subsequently saturated with caustic lye at a temperature of above 100° Centigrade.
By this saturation with hot alkalis of above 100 degrees, the contraction of the fibres
which takes place in the cold and is termed "mercerising" is obviated.
In the method hitherto known of scalding with caustic alkalis the latter are either
brought into contact with the fibre, while atmospheric air was still present in the
scalding vessel, in the fibre itself, or in the steam employed. In order to avoid an
oxydation of the fibre with such presence of air, the bleaching material had to be
covered or surrounded with a liquid, or the oxydation was prevented by the addition
of reductive bodies for instance bisulphite.
It was however hitherto unknown, that for this reductive action by bisulphite
preliminary treatment with caustic alkaline earths and subsequently the application of
boiling caustic alkalis was required to accomplish the bleaching described in the
present specification.
The commonly used large quantity of liquid, which was necessary to cover the
material to be bleached, amounted to the double or treble in weight of the bleaching
material; consequently a strong concentration of the alkali lye could not be
advantageously resorted to in factory work by pecuniary considerations.

page_text: The Ebrous material saturated with hot alkali lye is boiled at a high temperature
and for the purpose of accelerating the circulation and of concentrating at the same
time the quantity of alkaline liquid, a receptacle is provided below the scalding vessel,
which is continually emptied by a pump.
In order to make our invention more clear, we refer to the accompanying drawing,
in which similar letters denote similar parts throughout the different figures and of
which:
Fig. 1 is a side elevation,
Fig. 2 a top view of the apparatus used for the improved process.
A is the scalding vessel, the receptacle provided below the same and D the pump,
which may be of any suitable construction. The receptacle C contains a perforated
pipe a through the apertures of which steam can escape into the pipe leading into
the atmosphere or to the condenser. Through this pipe a steam continually escapes ;
the scalding liquid accumulating at the bottom of the receptacle C is drawn from the
latter by the pump D; the pressure in the receptacle C and in the lower portion of
the scalding vessel A is constantly varied by receiving or discharging steam, whereby
the circulating caustic liquid passes at a higher rate of speed through the brous
material. With this accelerated circulation moreover the lye is evaporated by constant
discharge of steam or water by means of the pipe a b. The pump D passes the
scalding lye through the tube boiler B, which is heated for about 40° Centigrade more
than the scalding liquid. During the continuous heating, circulation and action on
the fibrous material, the saponification takes place. According as the alkalis are
neutralized by saponification and consequently are weakened in action, this weaker
action is corrected by the concentration (evaporisation) of the scalding lye and the
saponification proceeds with uniform rapidity.
To more clearly illustrate the improved process in its manipulations, it will be
hereafter described as applied as an example to calico.
The dry cotton-cloth or calico, which is intended for calico printing is impregnated
with a quantity equal to its own weight of acid solution. To each litre of this solution
is employed:
10 grammes of sulphuric acid of 60 per cent. water-free acid, or
16 grammes of muriatic acid of 30 per cent. hydrochloric acid gas, and
0.5 grammes of fluor-acid of 75 per cent. is added.
The cloth is allowed to lie for about 4 hours in the acid solution, and after having
been made to pass for half a minute through steam, the pieces are passed through the
washing machine and then through an alkaline bath of about per cent. soda and
having a temperature of 50° Centigrade. We allow this bath to act for up to 12 hours,
generally during the night and we usually employ the saponified residues, containing
soda, from the scalding vessel for producing the said alkaline bath.
When the textiles are very impure, for instance through size, or when large
quantities of pectine-like bodies adhere to the raw material, the said manipulation is
wholly or partially repeated.
The calico, after having been lying in warm alkaline solution, is washed on the
washing machine; to every 1000 litres of water entering the washing machine we add
50 grammes of chloride of magnesium of 25° or of another alkaline earth compound.
In the case of ablution-waters which possess already a high degree of hardness
through alkaline earths, the addition of alkaline earths may be diminished or entirely
dispensed with, as by such waters the preparation of the fibre with caustic earth
alkalis is already effected. The excess of ablution water is pressed off and con-
sequently the material for the scalding vessel is brought in with about its own weight
in ablution water.
After the scalding vessel A is closed, the fibrous materials are steamed by the tube
system contained in the tubular boiler B. This steaming of the fibrous materials,
whereby the latter are raised, to a temperature of above 100° Centigrade, lasts,
according to the size of the boiler, up to 14 hours. In the receptacle C accumulate
water and air, which are let off from time to time. Into the scalding vessel prepared
in the said manner is brought boiling caustic lye whereby the textile thus prepared

page_text: receives uniformly the caustic solution.
To 1000 kilogrammes of calico we use
50 kilogrammes of ammoniac soda, which is made with slack lime into 600 litres of
caustic lye. In this solution we saponify prior to using it, about 10 kilogrammes of
resin; subsequently the solution, while in boiling heat, is pumped into the scalding-
vessel. Then we heat the scalding vessel liquid by means of the tubular boiler B,
while the liquid constantly circulates through A D B, to about 125° Centigrade.
The circulation and heating lasts for about hours, while the liquid is more and more
concentrated by continuous discharge through pipes a b. Subsequently the calico is
washed out in the scalding vessel with boiling water and then the usual chloric treat-
ment or chemicking takes place; but we use but one third of the quantity of chloride
of calcium that was hitherto required. Finally the souring is performed as described
at the beginning of the specification.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is:
In bleaching and scouring cotton, linen or other textile or fibrous material:
1. The process consisting in precipitating caustic alkaline earths on the fabric or
material, then deoxydating it by heating, air-pump, or reductive agent and sub-
sequently saturating it with boiling caustic alkali lye for the purpose of protecting
the fibre through the caustic alkaline earths from the structurally deforming action of
the caustic lye and from oxydation, substantially as set forth.
2. In the process forming the subject of claim 1, the method of concentrating the
scalding liquid by heating and discharge of steam below the scalding vessel with
simultaneous circulation of the liquid for the purpose of maintaining by concentration
a powerful saponification, while by the discharge of steam said circulation of the
liquid is accelerated substantially as set forth.
3. The process in bleaching cotton or other textile or fibrous material, of souring
the fibrous material prior to the scalding process by the addition of fluor-acid, and
subsequently steaming the fibrous material, for the combined purpose of rendering
the silica and other compounds capable of better solution and increasing the effect
of the acid, substantially as set forth.
Dated this 18th day of August 1890
HEINRICH THIES.
EMIL HERZIG.
By Huelser & Co.,
Their Agents.