Improved Process of Dyeing or Printing in Aniline Black or Analogous Colours.
Year: 1891

page_text: Date of Application, 12th Feb., 1891-Accepted, 21st Mar., 1891
COMPLETE SPECIFICATION.
Improved Process of Dyeing or Printing in Aniline Black or
Analogous Colours.
We, HEINRICH THIES, of Laaken, near Barmen-Rittershausen, Germany,
Manager, and FRIEDRICH CLEFF, of Rauenthal, near Barmen-Rittershausen,
Germany, Dyer, 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 :-
Our said invention relates to an improved process in which we use hydrofluoric
acid or its salts in conjunction with the usual means for the purpose of dyeing or
printing with aniline black and is applicable to the treatment of animal or vegetable
substances whether in the raw, spun, or woven state.
A preliminary drying in of the re-agents is essential to the process as carried out
according to our said invention for only by this method of oxidation is a colour
obtained which will not soil. But as heretofore practised the products brought
about by chemical change attack the fibres and the colour (an insoluble base) turns
more or less green under the action of acids.
In the process as hitherto carried out vegetable fibres in particular fade more or less
not merely from the oxidation itself but also from the acids (and their products of
decomposition) set free by the high temperature which is a material factor in the
production of colours with little liability to turn green.
Heretofore the acids mostly used have been hydrochloric acid, as well as other
acids either alone or mixed such as nitric, phosphoric, acetic, tartaric, oxalic,
ferrocyanic, ferricyanic and hydrobromic acids, and chloric acid, the latter serving
both as acid and oxidiser; but such only partly remedy the before-mentioned defects
in the course of the development besides being too expensive for commercial use.
The acids just mentioned act either with too little or with too much energy in the
course of the reaction or they volatilise too slowly and the reaction becomes too acid
and violent towards the end.
Hydrofluoric acid possesses, as compared with the developing acids hitherto
employed, materially different properties. Its action arises chiefly from thermo-
chemical processes and from the non-liability of hydrofluoric acid to decomposition.
Its avidity as compared with hydrochloric acid is in the proportion of 100:5. On
becoming free and volatilising it absorbs much of the heat which interferes with the
effect of the increasing energy of the heat of oxidation on the fibre (itself a bad
conductor of heat). During the action and decomposition of the alkaline chlorates
hydrofluoric acid does not decompose along with them like other developing salts
even when much in excess. Being a weak and partly volatile acid it plays a
uniform part in the reaction.
The course of the oxidation no longer alternates with the products of substitution
from the acid and with the products of chemical change due to the increasing energy
of free acid on the chlorates. In particular there is no longer such a sufficient
formation of nascent chlorine or chlorine substitutions as according to some opinion
is alone the cause of the colour turning green. To make up for the weak hydro-
fluoric acid we retain a portion of the acids hitherto used but in order to limit the
energy of these acids to the required effect we chiefly use them combined with the
stronger stable metallic bases or in some cases with ammonia and thus by contact
and dissociation hasten the reaction. We satisfy and remove, by using hydrofluoric
acid (for bringing about the oxidation of the aniline) the unbalanced liberated excess
of the acids hitherto employed and thus get rid of their injurious accompanying
effects.
When using hydrofluoric acid at the same time as the acids heretofore employed

page_text: it is possible either to produce or to prevent a source of chlorine by arranging a
calculable relation between the acids and the bases, which latter consist for the
greater part of metals and alkalies and to a lesser extent of the residues and
products of the chemical change of the aniline and thus it is possible to produce
commercially either a black absolutely without liability to take a green shade or a
black with an accurately predetermined green shade with perfect certainty.
The following is an example of a bath for dyeing mixed materials of cotton and
silk according to our said invention :―
2 grammes of carbonate of copper.
4 grammes of bi-carbonate of ammonia are dissolved in
25 grammes of hydrochloric acid 30 %.
To the solution is added
55 grammes of hydrofluoric acid of 60% diluted with
200 grammes of water.
To the mixture is added
140 grammes aniline oil and then
60 grammes chlorate of sodium is added dissolved in as much water as is required
to make up the whole to one litre.
A corresponding quantity of the material to be treated is soaked in this bath, then
dried and oxidised in the usual manner as is well understood, and washed. We do
not in any way limit ourselves to the proportions indicated in the above formula which
may of course be varied' to suit the particular material to be treated or the effect
desired. For instance in treating fibrous woollen materials the proportions of the
ingredients would of course be varied. For printing aniline black the usual
vanadium, cerium, iron, chromium, or copper compounds are used with the
chlorates but a portion of the acids is replaced by hydrofluoric acid. The aniline
black obtained by means of hydrofluoric acids presents physical and chemical
properties materially different from all other products obtained by a similar_treat-
ment. For instance by transmitted light it appears brown while by reflected light
it appears deep black. It is not affected by sulphurous acid nor by acids generally.
It has not the basic properties of ordinary aniline black and therefore combines
more easily with tar colours which can be used to obtain any desired shade.
The most important industrial advantage is however that the fibres retain their
natural properties. For example the lustre of silk is not lowered, wool remains soft
and vegetable fibres scarcely suffer.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what we
claim is :-
In dyeing or printing in aniline black or analogous brown or grey colours derived
from aniline, from its homologues or from naphtylamine the partial substitution of
hydrofluoric acid for the usual acids hitherto employed substantially as and for the
purpose hereinbefore set forth.
Dated this Ninth day of NGUTUSTY LOYI
Dated this Ninth day of
NeuruẞTA
LOX
EDWARD TURNER WHITELOW,
70, Deansgate, Manchester, Agent for the Applicants.
Guru TV
EDWARD TURNER WHITELOW,
70, Deansgate, Manchester, Agent for the Applicants.