Improvements in Black Dyeing.
Year: 1899

page_text: Date of Application, 15th Sept., 1899-Accepted, 23rd Dec., 1899
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COMPLETE SPECIFICATION.
Improvements in Black Dyeing.
I, EWALD HÖLKEN, of No. 18, Bredderstrasse, Barmen, Germany, Manufacturer,
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:
This invention relates to improvements in the process in dyeing with what is
known as "Vidal black" and equivalent sulphurous colouring matters. It is
known that the substantive sulphurous dyeing materials known as black vidal
(noir vidal), sulphur black, cachou lavalle, and others require after they have gone
through the dyeing bath a treatment with oxydizing means in a more or less hot
bath, some inventors prescribe baths of 400 to 50 degrees Celsius (104-122
Fahrenheit) containing 5 to 10%, chromate of potash and 5 to 10% sulphuric acid
of 60° Beaumé of the weight of the dyed goods.
Others again recommend treating with 3% vitriol of copper and 3% acetic acid
or with 2% chromate of potash and 3% acetic acid or with 2% chromate of
potash and 2% vitriol of copper and 3% acetic acid.
The goods dyed black by sulphurous colouring matters and such of the same
group and treated afterwards with acids and chromate of potash are not durable in
washing, for when treated with soap the white fibres of goods treated at the same
time get blue, and especially so, when the stuffs thus treated are exposed to hot
steam.
Goods treated with vitriol of copper, chromate of potash and acetic acid, or
with vitriol of copper and acetic acid combined, give only little colour to white
fibres combined with them-(they "bleed" only little, as the technical term
is) but they are subject to this disadvantage, when stuffs or yarns dyed black by
this means, are mixed with white wool, as is the case in piece goods.
*
Now it is known that cotton yarns dyed black are very much used together
with half woollen and half silk goods and it is required that in such goods, when
dyed in pieces, the wool or the silk shall in no way be influenced by the cotton,
and as the best durable black in this respect was considered hitherto the so called
oxydation black" and " one bath aniline black," though they do not by far
answer the requirements in the desired degree. These two black dyes give to the
wool in the sulphuric bath a nasty violet tint, which shows itself the more, the
longer the stuff is exposed to the hot bath. They get greenish gradually and both
qualities make it difficult to produce tints coinciding exactly with the sample
pieces of wool or silk. Besides this; small particles of black dye precipitate from
the black cotton, which soil the wool and spoil its brilliancy.
The colours produced by sulphurous black dyes are excellently qualified to super-
sede the aniline black nearly exclusively used hitherto. Now though yarns treated
with chromate of potash, vitriol of copper and acetic acid afterwards or with
vitrol of copper and acetic acid alone do not spoil the woollen fibres, they have
the other disadvantage, that when the goods are steamed the copper salt contained
in those black yarns combines itself with the sulphur contained therein and

page_text: forms cuprous sulphide, settling as a yellow brownish colour in the wool, which can
not be destroyed and makes it impossible to dye the wool in light brillant colours.
The effect of the salts of other metals is similar, the combinations of sulphur in
which show themselves in the form of black precipitations.
Now the newness in our process consists in this, that for the aftertreatment of
black dyed by sulphuric means, we use instead of copper salts such metallic salts,
the combinations of which with sulphur are white and which therefore can not in
an injurious manner influence the wool.
Experiments have proved that we attain this object in a most satisfactory degree
by using for the aftertreatment of sulphurous blacks, salts of zinc, and as such
are especially fit sulphuric, hydrochloric and acetic salts of zinc.
The manner how we proceed is shown in the following example.
The yarns dyed black are placed in a bath of 40 to 500° C. to which are added
4 to 6 % vitriol of zinc
2-3 % chromate of potash
2-3 % sulphuric acid (60° Beaumé)
of the weight
of the goods.
Other organic and inorganic acids that is acids free of carbon may be used.
The effect of this bath upon the colour, which up to this treatment had a greenish
-appearance is as follows;
The vitriol of zinc fixes the colour in the moment of the plunging of the goods
into the bath, so that the yellow colour of the bath is not altered in the least and
therefore the bath is held free of any impurity, whereas in other baths, where no
vitriol of zinc is used, the liquid takes a nasty greenish colour. At the same time
with the fixing of the dye a certain reaction of the chromic acid through the
vitriol of zine shows itself, and by gradually raising the temperature of the bath
the oxydation becomes more energetic and it is competed at the boiling heat. This
is shown by the fact that the bath has now got quite clear, without any yellowish
or greenish tint.
Chromic acid can not be traced any more in the bath by the usual agencies.
When chromic acid alone is used, nearly half of it remains in the bath.
The more chromic acid is used, which must be regulated by the shade of the
colour required, the more full and effective is the colour.
I always give muriate of zinc in excess in order to attain the most perfect
brilliancy. This excess of muriate of zinc can be easily washed out in the water
bath.
With light black I only fix the colour in a warmed bath of muriate of zinc and
I wash out afterwards. I add to the muriate of zinc so much sulphuric acid that
alkalies, which may have remained in the goods will be neutralized.
Cotton yarn dyed black with substantive sulphurous dyes, treated afterwards in
this manner is excellently fit for being used with half woollen goods, which are
to be dyed in pieces in various colours as well as for black goods.
The colour of the cotton will stand the most severe treatment, as hot washing,
washing out the weavers glue in the hot soap bath, cleaning the wool in the
ammoniacal bath, treating in high pressure steam, the singeing and the finishing,
dyeing in the sulphuric bath, without in the least influencing the wool and without
loosing itself of its fulness. The wool remains quite white.
Muriate of zinc has not been used hitherto in combination with chromate of
potash and acids for the aftertreatment of goods or vegetable fibres, yarns or woven
goods dyed with substantive sulphurous dyes.
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 dyeing vegetable fibres, -(whether in form of spinnings (yarn) or woven
together with other fibres)-by means of so called "Vidal black" and similar
sulphurous substantive dyeing materials, the process, which consists in the use, for

page_text: the aftertreatment after the dyeing, of such metal salts, the combinations of
which with sulphur are white and which therefore do not stain the animal fibre.
2. The process of treating goods dyed in black by Vidal black and similar
sulphurous substantive dyes, which consists in the treatment of said goods after
dyeing, with muriate of zinc and acid alone or with muriate of zinc, acid and
chromate of potash combined, substantially as described.
Barmen the 18th day of September 1899.
EWALD HOLKEN,
Per Karl J. Mayer,
Agent.