An Improved Bleaching Process for Yarns, Piece Goods, and other materials.
Year: 1893

page_text: Date of Application, 11th Jan., 1893-Accepted, 13th May, 1893
COMPLETE SPECIFICATION.
[Communicated from abroad by OTTO KEFERSTEIN, Senior, and OTTO
KEFERSTEIN, Junior, both of the firm of Greiffenber Bleich und appretur,
Anstalt, Germany, Manufacturers, and the firm of Siemens and Halske, of
94, Markgrafen Strasse, Berlin, Germany, Manufacturers.]
An Improved Bleaching Process for Yarns, Piece Goods, and other
materials.
I, CHARLES DENTON ABEL, of No. 28 Southampton Buildings, Chancery.
Lane, in the County of London, Chartered Patent Agent, 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:
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This invention relates to an improved bleaching process wherein the known
bleaching actions of ozone and of chloride of lime are so combined that the strength
of the fibre of the material treated is not injuriously affected while a perfect
bleaching action is obtained.
If ozone be allowed to act upon yarns &c. until a perfect bleaching action is
obtained, the yarn will become quite brittle and useless.
If, on the other hand, only chloride of lime (without grass bleaching) be allowed
to act for a length of time on the yarn, the strength of the yarn will not be affected
in the same degree as with ozone, but only about a three-quarters-bleaching, and
therefore imperfect treatment, will be obtained.
In practice, the action of chloride of lime has been combined with that of grass
bleaching, in which operation it has been shown that, in addition to ozone, nitrite
of ammonia and peroxide of hydrogen also enter into action, all three bodies being
present in about equal quantities and in a state of great dilution.
My correspondents have endeavoured to employ ozone obtained from the air in
the most concentrated form obtainable and purified of all by-products, and they..
have found that it has in the first instance a uniform bleaching action upon dry
and moist crude yarns, but that such bleaching action soon decreases, while on the
other hand the destruction of the fibrous structure rapidly increases.
This consequently pointed to the necessity of allowing the artificial ozone only
to act as long as the bleaching action thereof is favorable, and while the
destructive action upon the fibre either does not occur at all, or only to a very
slight degree.
A further fact discovered by experiment by my correspondents led to the
attainment of a perfect bleaching action.
When the yarn, in the treatment with ozone, becomes less sensitive to its
bleaching action, its sensitiveness to such action can be restored if the yarn is
dipped for a short time into a weak chloride of lime solution.
x
In addition, the bleaching action of the weak chloride of lime solution will be
considerably increased by the previous treatment with ozone, so that it bleaches as
effectually as a much stronger chloride of lime solution applied during the same
length of time, while the fibre is much less affected.
Lastly, it has been shewn that if the yarn, prepared in the ordinary manner,
be alternately subjected to the action of ozone and to that of a weak chloride of
lime solution, a complete bleaching action is obtained without the use of grass.
bleaching.
The chemical action appears to be as follows: At the commencement of its
action, the ozone decomposes the coloring matter of the fibre; the decomposition
products however enter into combination with the coloring constituents that have
not yet been attacked, such combination being attacked with much greater difficulty
by the ozone than the fibre material underneath it.

page_text: In consequence hereof, on the further treatment with ozone, its bleaching action
gradually decreases while its destructive action on the fibres increases.
If on the other hand the treatment with ozone be interrupted at the point
where its action begins to be detrimental, and the yarn' be immersed in a weak
chloride of lime solution, the action of the latter appears to be a two fold one :
Firstly the decomposition-products produced by the ozone action on the coloring
matters appear to be more readily dissolved, and secondly, there appear to take
place reactions between the weak chloride of lime solution and the neutral or
acid nitrate or nitrite combinations of ammonia which are always produced on the
fibre under the ozone action, which reactions result in a production of bleaching
oxygen that is added to the yield of oxygen from the chloride of lime.
The previous treatment with ozone consequently increases the bleaching action
of the chloride of lime.
The technical advantages obtained by this process are as follows:
The bleaching action is higher, and the decrease of strength of the fibre
is considerably less than with the simple ozone, or simple chloride of lime
bleaching.
As compared with the ordinary bleaching process consisting of a combination of
the ozone and grass bleaching processes, the degree of bleaching. by the above
described process appears to be the same; on the other hand the grass bleaching is
dispensed with, all manipulations are carried on at the works, the duration of the
bleaching process is reduced to about one fourth, and the strength of the fibres is
maintained of a higher degree.
The technical operations in carrying out the said new process are as follows:
The crude yarn is first prepared in the usual mauner by boiling with lye and
momentarily steeping in strong chloride of lime solution; it is then washed, wrung,
and suspended in a moist condition for some hours (say from 2 to 6 hours) in the
ozonising chamber. The yarn is then steeped for some hours (say from 10 to
20 hours) in a weak chloride of lime solution, again washed, wrung and suspended
in the ozonising chamber, and so the yarn is alternately subjected to the two
bleaching agents with gradual diminishing bleaching action until the bleaching is
completed.
In the above described process, the bleaching gas may for example contain from
2 to 10 per cent. of ozone.
The concentration of the chloride of lime should be about 1-4 grammes of chloride
of lime to 1 litre of liquid.
It has proved to be of advantage, during the ozonising process, to subject all parts
of the yarns uniformly to light.
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It is therefore requisite to effect the turning round and reversing of the yarn in
some suitable manner so that each part may receive the same total amount of light.
As sources of light may be used sun-light, day-light and electric arc light
The ozone chamber must be so arranged that the ozone is equally distributed
throughout the same, and can act uniformly on all parts of the yarn; also, that
the light shall have free access, and shall act consecutively in a uniform manner
upon all parts thereof, and lastly, that the introduction and removal of the yarn
shall be effected in a simple and easy manner.
For satisfying these conditions those walls of the ozone chamber through which
the light can enter, are made of glass; the ozone is introduced simultaneously at
several points, for example by means of perforated pipes, the inner and outer
surfaces of which are provided with a coating that is not attacked by ozone (such
as paraffin &c.) and lastly, mechanical devices must be provided by means of which
the yarns are turned round and reversed during the ozonising process. This latter
object is best attained by constructing the ozone chamber of a long form, and
mounting in the same a horizontal longitudinal shaft that is rotated slowly from
the outside, and which carries a series of wooden drums or radial arms on which the
yarns, stretched over wooden bars, are mounted so as to revolve therewith and thus
have all parts thereof uniformly presented to the ozone and to the light.

page_text: Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
A process for bleaching yarns, piece goods and similar materials consisting in
subjecting the materials to be bleached, after being prepared in the usual manner
by boiling with lye, to the alternate action of chloride of lime solution and of
artificial ozone, both bleaching agents being employed in such a diluted condition or
for so short a time, that each individually would not effect a perfect bleaching and
that the strength of the fibres is not injuriously affected, substantially as described.
Dated this 11th day of January 1893.
ABEL & IMRAY,
Agents for the Applicant.