Process of Mordanting and Dyeing Animal Fibre.
Year: 1897

page_text: Date of Application, 18th Dec., 1897-Accepted, 29th Jan., 1898
COMPLETE SPECIFICATION.
Process of Mordanting and Dyeing Animal Fibre.
I, OTTO PAUL AMEND, of 205, Third Avenue; in the City and State of New York,
United States of America, Chemist, 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:-
My invention relates to the art of dyeing animal fibre, whether wool fibre, silk
fibre, hair, or other animal fibre. It consists in producing a mordant upon the
fibre at comparatively low temperature, and without the boiling of the fibre here-
tofore employed, by treating it in a free chromic acid bath in the absence of a
non-oxidizing acid and thereafter reducing the chromic acid on the fibre by suitable
means. It also consists in producing a mordant on such fibre by treating
it in a free chromic acid bath in the absence of a non-oxidizing acid and without
the boiling of the fibre, whereby, without separate treatment by a special reducing
agent, the fibre is made ready for the reception of dyes which of themselves
operate to reduce the chromic acid on the fibre. It, furthermore, consists in mor-
danting, the fibre with the free chromic acid in the manner last stated and then
dyeing with a substance of such character as will of itself reduce the chromic acid
compound on the fibre. The aromatic amines or their salts are substances of such
character as will of themselves reduce the chromic acid on the fibre and may be
fixed on the fibre without previously treating the fibre with a separate reducing
agent.
In carrying out the process the fibre is first treated, as by immersion, in a
bath containing free chromic acid and which does not contain a non-oxidizing
acid. The strength of this chromic acid bath may considerably vary. I have
used successfully a 5 per cent. (0.05) solution, and have also used successfully a
very weak solution, as low as one-thirtieth of one per cent. (0.00033). "In
general where the subsequent reduction is performed in the chromic acid
bath, I prefer a weaker solution; but if the subsequent reduction is performed
in a separate bath I should prefer a stronger solution. The fibre may remain in
the bath from half an hour to an hour. In preparing this chromic acid bath I may
dissolve free chromic acid as found in the market, or may liberate the chromic acid
from a chromate solution, thus obtaining the free chromic acid in the solution form-
ing the bath, or may obtain the chromic acid solution in any other suitable way.
In this step of the process it is my purpose to obtain a chemical union of the fibre
and free chromic acid, that is, a chromic-acid-fibre-compound, and it is important
and essential to my process that the fibre be not oxidized by the chromic acid.
Heretofore, in all cases, so far as known, where chromic acid has been used or
proposed in mordanting or treating animal fibre for dyeing purposes, the fibre was
oxidized in the presence of the chromic acid, and such oxidation was dermed
essential to the production of the results sought. Moreover, in the practical art
it has been customary to boil the fibre in the presence of the chromic acid. This
oxidation of the fire and this boiling are purposely avoided in my process and the
attending results are unquestionably highly advantageous.

page_text: I do not therefore boil the bath in the presence of the fibre, and I am careful
also not to raise the temperature of the bath to a maximum point such that the fibre
would be oxidized. So long as this maximum temperature is not reached the
temperature of the bath while the fibre is being treated may vary greatly without
departure from the process. The maximum allowable temperature will of course
vary with the different characteristics of different fibres under treatment.
Ordinary temperature, that is, ordinary dye-house temperature, although it may
vary greatly in different dye-houses and at different times, will be generally found
the most advantageous, as the carrying out of the process will not of itself require
any extra expenditure of fuel or steam. About 160° Fahrenheit. I have found to be
generally the maximum allowable temperature of the chromic acid treatment,
temperature above this point causing generally the injurious oxidation which I
seek to avoid.
In preparing the fibre for treatment in a dye bath of wood dyes, dyes of the
alizarine series, and such other dyes- which of themselves do not operate to effectu-
ally reduce the chromic acid on the fibre, I complete the mordant by subjecting the
fibre to the action of a suitable reducing agent. This reducing agent may be acid,
alkaline, or neutral in character, and may vary considerably in strength. I have
used reducing baths successfully which varied in strength from one half of one per
cent. (0.005) to one fifth of one per cent. (0.002) of the bath, and have satisfactorily
used an aqueous solution of sulphurous acid as a reducing agent. Sulphuretted
hydrogen, ferrous sulphate, cuprous chloride, formic acid, lactic acid or other
reducing agent may be employed. In practice the reducing agent is preferably added
to the chromic acid bath containing the fibre, which then remains in the reducing
bath long enough to fully produce the reducing effect desired, that is to say, the
chromic-acid-fibre compound is reduced to a chrome-oxide-fibre compound. This
result will generally be produced advantageously in from half an hour to an hour,
the fibre turning from a yellowish to a greenish tinge in the case of white or grey
material.
It will be found that the fibre mordanted as above described will be prepared
for the reception of any of the dyes which produce lakes with metallic compounds.
Such dyes may be applied to the mordanted fibre by any process. The mordant
thus produced is especially valuable in dyeing wool.
In cases where it is desired to treat the fibre in a dye bath which of itself
effects the reduction of the chromic-acid on the fibre, such for example as dye baths
of the aromatic amines or their salts, the mordanting process is completed by
means of the chromic acid treatment, above described, and without subjecting the
fibre to a treatment by a separate reducing agent.
The mordants produced by my process, as above described, are.
of great
value, and are produced, moreover, at a much less cost than that of the mordants
heretofore in general use, all of which require boiling, with its attendant deleterious
results.
I will now describe the treatment of the fibre by means of a substance adapted
to generate a color on the fibre, and which does not require the previous treat-
ment of the fibre with a separate reducing agent, referring to the aromatic amines
or their salts, by way of example, and in particular to an aniline salt. The fibre,
after being treated as above described with the chromic acid, is taken out of this
bath and the excess of the chromic acid solution removed by pressing, winding,
washing or in any other suitable way. The fibre is then subjected, as by immer-
sion, to the aniline dye bath, of which a one per cent. (0.01) solution has been
found satisfactory. The fibre remains in this dye bath till it takes a deep black
color, generally about three hours, and is then taken out, and the excess of the
dye solution removed. The color may then be developed in the usual way at any
suitable temperature. I have found a temperature of 80° centigrade satisfactory:
An oxidizing agent is not required in the dye bath to oxidize the aniline salt, but
the use of such an agent would not be a departure from my invention. In this way,

page_text: hair or fur especially may be dyed black with great advantage, although of course
other colors may be fixed on hair and other animal fibres.
Of course, various changes may be made in the strength, duration and tempera-
ture of the baths of the different steps and I wish it to be understood that my
invention is not limited in these respects to any precise formula. The precise
formula most advantageous in any particular case must be left largely to the
judgment of the dyer, and such formula will depend, for the most part, upon the
character and physical condition of the particular fibre under treatment. In
general, it will be found that a stronger bath will not require so long a treatment of
the fibre in that bath; and that the maximum allowable temperature of the first
bath must be lower, to prevent oxidation of the fibre, when stronger chromic acid
solutions are employed.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. In the production of a mordant on animal fibre for dyeing, the process of
treating the fibre with a solution of free chromic acid, in the absence of a non-
oxidizing acid the treatment taking place at such temperature as will not of itself
substantially produce an oxidation of the fibre under treatment.
2. The process of producing a mordant on animal fibre for dyeing, which consists
in first treating the fibre with a solution of free chromic acid, in the absence
of a non-oxidizing acid, and, second, in thereafter treating the fibre with a suitable
reducing agent, the treatment taking place at such temperature as will not of
itself substantially oxidize the fibre under treatment.
3. The process of dyeing animal fibre which consists in treating the fibre with
a solution of free chromic acid, in the absence of a non-oxidizing acid, the treat-
ment taking place at such temperature as will not of itself substantially produce.
an oxidation of the fibre under treatment, and then treating the thus prepared fibre
with a substance adapted to generate a color on the fibre of a character such as
will reduce the chromic-acid on the fibre, as for example, aromatic amines or their
salts, whereby a durable color is fixed on the fibre.
ated this touth day of December 1897
OTTO PAUL AMEND.
Signed in presence of
NICHOLAS M. GOODLETT, JR.,
Lawyer, 150, Nassau Street, New York.
Haseltine, Lake & Co.,
45. Southampton Buildings, London, W.C., Agents for the Applicant.