Improvement in the Development of Colours by Chromium Compounds on Wool Fibre.
Year: 1899

page_text: Date of Application, 16th June, 1899
Complete Specification Left, 26th Feb., 1900-Accepted, 7th Apr., 1900
PROVISIONAL SPECIFICATION.
Improvement in the Development of Colours by Chromium
Compounds on Wool Fibre.
I, OLIVER IMRAY, of Birkbeck Bank Chambers, Southampton Buildings, in
the County of London, Chartered Patent Agent, do hereby declare the nature of
this invention (as communicated to me from abroad by Die Farbwerke vormals
Meister Lucius & Brüning, of Hoechst a/Main, in the Empire of Germany,
Chemical Manufacturers,) to be as follows:-
In the method for producing fast colours developed by chromium compounds
on wool fibre, forming part of the German Patents Nos. 66,838 and 67,240 and
the English Patent No. 9371 of 1893 my foreign correspondents have made an
important improvement and have thus opened a new field to colours developed
by chromium compounds in fast wool dyeing.
The process which takes place in producing such colours on the fibre is such
that the respective azo-dyestuffs are first dyed in an acid bath on the wool fibre,
then oxidised by the action of chromic acid, while being transformed simul-
taneously into the chromium oxide lakes of the oxidation products thus formed.
With the present mode of working (also described in the above cited patents),
the transformation into the oxidation products as well as the formation of their
chromium oxide lakes is by no means complete.
A part of the dyestuff, though small, is fixed on the fibre in an unchanged
condition, as shewn, when the fibre is milled and washed, by bleeding on raw
white material.
My correspondents have made the surprising observation which could not have
been foreseen that a simultaneous addition of reducing agents, such as lactic
acid, lactates, tartaric acid, citric acid and its salts, bisulphite etc., to the
chromium fluid avoids this drawback.
If woollen yarns, for instance, be dyed with 4 per cent. of chrome brown R O,
15 per cent. of Glauber's salt and 3 per cent. of sulphuric acid in the usual
manner and boiled for 1 hour, then on adding 5 per cent. of potassium bichro-
mate, 2 per cent. of sulphuric acid and 3 per cent. of lactic acid and boiling for
another hour, a deep brown is obtained, exceedingly fast to milling and not
liable to bleed. If, however, there is no addition of lactic acid, a brown is
obtained, which bleeds on the white when the fibre is strongly milled with
soap and still more so when milled with soda; it is consequently useless for
dyeing loose wool, slubbing or yarns, which, besides white or light colours, are
employed for milled goods.
An effect similar to that obtained with lactic acid is obtained with tartar,
oxalic acid, tartaric acid, citric acid, bisulphite etc., which, like lactic acid,
reduce chromic acid.
In obtaining colours developed by chromium compounds, fast to milling, it is
also of importance, that the dye-bath at the time of the oxidising action of the
chromate should give a decidedly acid reaction, a simultaneous addition of

page_text: mineral acids with the chromate liberating the chromic acid, is therefore indis-
pensable.
It is preferable in some cases, as stated in the second claim of the German
Patent No. 66,838, to prepare the bath at the beginning together with the dye-
stuff, acid, Glauber's salt and chromate. In this case the above mentioned
reducing agents together with an excess of lactic acid are only added after the.
formation of the lake on the fibre is fairly completed by boiling for about 1 hour.
The action of the reducing agents upon the fastness of the colours to milling
is a remarkable one and may be observed with all colours developed by
chromium.
The process may be illustrated by the following examples:
EXAMPLE I.
Dark brown fast to milling on 50 kilos. loose wool.
The bath is prepared with about 150 litres of water, 75 kilos. of Glauber's
salt 15 kilos. of sulphuric acid' and 2 kilos. of chrome brown RO, the wool is
introduced at 40° C., brought to boil within half an hour and boiled for 1 hour.
Then the bath is somewhat cooled, the solution of 25 kilos. of potassium bichro-
mate, 1 kilos. of sulphuric and 125 of lactic acid is added and the brown is
developed by boiling for about 1 hour.
EXAMPLE II.
Black upon 50 kilos. of cheviot yarn.
The bath is prepared with about 200 litres of water, 10 kilos. of Glauber's salt,
2 kilos. of sulphuric acid and 2,750 kilos. of chromotrope S., the yarn is intro-
duced at 40° C., brought to boil in about 1 hour, and after boiling one hour,
125 kilos. of tartar and 15 kilos. of sulphuric acid are added and the whole is
further boiled for about half an hour.
ד
ABEL & IMRAY,
Agents for the Applicant.
Improvements in the Development of Colours by Chromium
Compounds on Wool Fibre.
I, OLIVER IMRAY, of Birkbeck Bank Chambers, Southampton Buildings, in
the County of London, Chartered Patent Agent, do hereby declare the nature of
this invention (as communicated to me from abroad by Die Farbwerke vormals
Meister Lucius & Brüning, of Hoechst a/Main, in the Empire of Germany,
Chemical Manufacturers,) and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement:-
In the method for producing fast colours developed by chromium compounds
on wool fibre, forming part of the German Patents Nos. 66,838 and 67,240 and
the English Patent No. 9371 of 1893, my foreign correspondents have made an
important improvement and have thus opened a new field to colours developed
by chromium compounds in fast wool dyeing.
The process which takes place in producing such colours on the fibre is such
that the respective azo-dyestuffs are first dyed in an acid bath on the wool fibre,
then oxidised by the action of chromic acid, while being transformed simul-
taneously into the chromium oxide lakes of the oxidation products thus formed.
With the present mode of working (also described in the above cited patents),

page_text: the transformation into the oxidation products as well as the formation of their
chromium oxide lakes is by no means complete.
A part of the dyestuff, though small, is fixed on the fibre in an unchanged
condition, as shewn, when the fibre is milled and washed, by bleeding on white
material treated simultaneously.
My correspondents have made the surprising observation which could not have
been foreseen, that a simultaneous addition of reducing agents, such as lactic
acid, lactates, tartaric acid, citric acid and its salts, bisulphite etc., to the
chromium fluid avoids this drawback.
If woollen yarns, for instance, be dyed with 4 per cent. of chrome brown R O,
15 per cent. of Glauber's salt and 3 per cent. of sulphuric acid in the usual
manner and boiled for 1 hour, then on adding 5 per cent. of potassium bichro-
mate, 2 per cent. of sulphuric acid and 3 per cent. of lactic acid and boiling for
another hour, a deep brown is obtained, exceedingly fast to milling and not
liable to bleed. If, however, there is no addition of lactic acid, a brown is
obtained, which bleeds on the white when the fibre is strongly milled with
soap and still more so when milled with soda; it is consequently useless for
dyeing loose wool, slubbing or yarns, which, besides white or light colours, are
employed for milled goods.
An effect similar to that obtained with lactic acid is obtained with tartar,
oxalic acid, tartaric acid, citric acid, bisulphite etc., which, like lactic acid,
reduce chromic acid.
In obtaining colours developed by chromium compounds fast to milling, it is
also of importance, that the dye-bath at the time of the oxidising action of the
chromate should give a decidedly acid reaction, a simultaneous addition of
mineral acids with the chromate, liberating the chromic acid, is therefore indis-
pensable.
To obtain greater uniformity of the dye, it is preferable sometimes, for
instance, with yarns, when developing, to add first the requisite quantity of
bichromate and then about 15 minutes later the reducing agent and sulphuric
acid.
It is preferable in some cases, as stated in the second claim of the German
Patent No. 66,838, to prepare the bath at the beginning together with the dye- .
stuff, acid, Glauber's salt and chromate. In this case the above mentioned
reducing agents together with an excess of mineral acid are only added after the
formation of the lake on the fibre is fairly completed by boiling for about 1 hour.
The action of the reducing agents upon the fastness of the colours to milling
is a remarkable one and may be observed with all colours developed by
chromium.
The process may be illustrated by the following examples:-
EXAMPLE I.
Dark brown fast to milling on 50 kilos. loose wool.
The bath is prepared with about 150 litres of water, 75 kilos. of Glauber's
salt, 15 kilos. of sulphuric acid and 2 kilos. of chrome brown RO, the wool is
introduced at 40° C., brought to boil within half an hour and boiled for 1 hour.
Then the bath is somewhat cooled, the solution of 25 kilos. of potassium bichro-
mate, 1 kilo. of sulphuric and 125 kilos. of lactic acid is added and the brown
is developed by boiling for about 1 hour.

page_text: 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
The herein described improvements in the development of colours by chromium
compounds on wool fibre by treating the colour to be developed with reducing
agents in addition to the oxidising chromic acid.
1000
ABEL & IMRAY,
Agents for the Applicant.