Improved Process of Producing a Fast Black Colour on Fibrous Substances.
Year: 1893

page_text: COMPLETE SPECIFICATION.
Improved Process of Producing a Fast Black Colour on Fibrous
Substances.
I, OTTO PAUL AMEND, Chemist, of 205 Third Avenue, New York City, United
States of America, do hereby declare the nature of this invention and in what
manuer the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
Heretofore processes of printing or dyeing in black upon vegetable fibres, as
cotton, linen and mixed fibres, with aniline, toluidine and other aromatic amines
and their salts, have produced fairly satisfactory results, but all attempts to produce
a fast black with such amines and salts upon animal fibres, especially wool and silk,
have proved unsuccessful. Various processes have been tried, but none has
produced a fast black. These failures have been attributed by some to a peculiar
reducing action of the fibres during the dyeing or developing of the black, and as
the processes have depended upon oxidation of the dyeing material to produce the
color this contemplated oxidizing effect has been counteracted by the reducing
action of the animal fibres. Others attribute these failures to the peculiar action
of the fibres due to the sulphur contained in them, and various processes have
been devised for a partial or complete elimination of this sulphur, but all such
processes have so far proved unsuccessful.
I have found that an aqueous solution of chromic acid in presence of another
acid that will not produce a secondary oxidizing re-action on the fibre, preferably
hydrochloric or acetic acid, produces upon animal fibres a peculiar and very
intimate union and combination, whereby the fibre is partially oxidized and part of
the chromic acid is taken up by it and apparently combines with it, forming a
chromic compound with the fibres. It is necessary that the quantity of chromic
acid in the solution be such that after a part is reduced to chromic oxide, a
sufficient amount remains to combine with the fibre. The presence of the second
acid is necessary to keep in solution all of the chromic oxide formed and thus
prevent its being deposited on the fibre. The acids which cannot be used in the
solution with the chromic acid are such acids as sulphuric and nitric, which would
oxidize or destroy the fibre.
The treatment of the animal fibre with the above mentioned solution of chromic
acid in presence of other acids is the first step or re-action in my process of
producing a fast black color. The second step or re-action of the process consists
in treating the fibre with any of the aromatic amines or their salts in presence of a
salt of metallic oxide, whereby a fast black color is developed first in the cold and
the development is finally completed at a heat of about 800 centigrade.
My new process is applicable to wool, silk and other animal fibres and also to
vegetable fibres, and may be applied to such fibres in any of their usual forms, as
when in a separated state, or when twisted into yarns or threads or when woven
into cloths or other fabrics.
I will now fully and particularly describe my complete process.
I prepare au aqueous solution of chromic acid and hydrochloric acid and immerse

page_text: the wool or other fabric therein. The proportions of acid for each one half
kilogramme of wool, are about twenty grammes of anhydrous chromic acid and
about thirty grammes of hydrochloric acid. Sufficient water is employed to permit
complete immersion of the fibre therein. The solution is used at ordinary room
temperature, from 20° to 30° centigrade.
After the above described treatment the excess of the solution is removed
from the fibre by suitable mechanical means, such as wringing or pressing through
rollers.
The second solution is composed of aniline, toluidine or other aromatic amine or
its salts which will produce black and of metallic oxide salt, in the proportion for
every one half kilogramine of wool or other fibre, of about fifty grammes of the
aromatic amine or salt and proportionate amount of the metallic oxide salt. Of
the latter substance I have found that ferric sulphate produces very good results.
used
Sufficient water is employed to completely immerse the fibre. The solution
at ordinary room temperature.
After immersion in this second solution, the color begins to develop at the
ordinary room temperature. After a certain shade has been produced, the excess
of the solution is mechanically removed, and the material is subjected to a
temperature of about 800 centigrade. This may be accomplished by placing the
substance within a so-called Mather & Platt steam box or other heating device.
It will of course be understood that my invention is not limited to the exact
proportions above specified. For instance, the amounts of chromic acid and of
hydrochloric acid above specified may be considerably exceeded without other
result than a waste of such acids. So also some fibrous substances may require
slightly different proportions of the various aromatic amines, salts and acids. Nor
are the exact temperatures above described always essential to my invention.
A beautiful deep black color is produced. The material as thus colored will be
found to withstand all the tests required of the best and most expensive blacks
known. The fibre will be found to have lost none of its original physical properties,
but on the contrary to have gained increased strength.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
:-
1. The process of producing a fast black color on fibrous substances, which
consists in treating such substances with a solution of chromic acid in presence of
other acid that will not produce a secondary oxidizing effect on the fibres, and then
treating such substances with a solution containing an aromatic amine or its salt,
substantially as set forth.
2. The process of producing a fast black color on fibrous substances, which
consists in treating such substances with a solution of chromic acid in presence of
other acid that will not produce a secondary oxidizing effect on the fibres, and then
treating such substances with a solution of an aromatic amine or salt with a salt of
metallic oxide, substantially as set forth.
3. The process of producing a fast black color on fibrous substances, which
consists in treating such substances with a solution of chromic acid in presence of
another acid or acids that will not produce a secondary oxidizing effect. on the
fibres, then removing excess of said solution, then treating such substances with a
solution of an aromatic amine or salt with a salt of metallic oxide, then permitting
the black to partly develop at ordinary room temperature, then removing excess of
said solution, then subjecting said substances to a higher temperature whereby such
color is completely developed, substantially as set forth.
Dated this 5th day of May 10,
OTTO PAUL AMEND.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, Agents for the Applicant.