Process of Completely Decolorizing Dyed Fibrous Materials.
Year: 1899

page_text: COMPLETE SPECIFICATION.
Process of Completely Decolorizing Dyed Fibrous Materials.
I, FRANCIS HERBERT OLDROYD, of Niedergorpe, near Naumburg, o/Bober
(Silesia), in the Empire of Germany, Manufacturer, do hereby declare the nature
of my said 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 a process of completely decolorizing dyed fibrous
materials of vegetable or animal nature i.e. of also removing from the fibre the very
last residue of dye, so that the former is white and can receive any new kind of
dye. The process is carried out in such a manner that the fibre is by no means
affected as is the case when using strong acids--which destroy certain dyes—and
other means.
According to the invention, the decolorization is effected in the following
manner:-
The materials to be treated are, after being suitably reduced, first treated for
from 15 to 20 minutes in a bath, of boiling water rendered alkaline by the addition
of about three per cent. of the weight of the materials of ammonia, soda, soap,
borax or the like, thereby dissolving, a considerable portion of the dye which
remains dissolved in the bath, so that the materials to be taken out of the latter
and to be washed contain only such dye as cannot be removed by dissolving.
For removing this last residue of dye, a bath is used, which is formed by
putting a mixture of bisulphite of soda and powder of zinc or of other substances
forming sulphurous and hyposulphurous acids into water and heating the solution.
The materials previously washed in the above mentioned manner are left in
the said bath maintained if necessary at a boiling temperature, until the very
last residues of the dye adhering to the fibre are removed. The fibrous materials,
after being removed from this bath, are perfectly white and when they have been
thoroughly washed and dried in the usual manner, they can now be further
treated or used.
The composition of the baths according to the proportional quantities of the
materials to be used therefor, depends on the nature of the dyed materials as well
as on the dye and can be readily determined, according to the different propor-
tions, by any practical man on the basis of a previous trial. Even in that case
when the active materials are contained in the second hath in excess, an affecting
or weakening of the fibre need not be feared.
By the aid of this process, the waste of textile materials of different kinds can
be utilized in an economically advantageous manner, since not only a complete
decolorization of the materials is attained, so that these can undergo any desired
further treatment, but also a weakening or an affecting of the fibre does not take
place, which according to experience is the principal reason why the known
bleaching methods with acrid, corrosive materials could not hitherto be made
utilizable with practical success for the purpose in question.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
Improved process of completely decolorizing dyed fibrous materials consisting

page_text: in treating these materials first in a dissolving bath subjected to the action of
heat until the dye adhering to the fibre no longer dissolves, then washing such
materials in a decomposing bath containing bisulphite of soda and powder of
zinc or other substances forming sulphurous and hyposulphurous acids, until
the dye is completely removed and also washing and drying the materials in the
usual manner substantially as described and for the purpose set forth.
Dated the 10th day of August 1899.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.