IMPROVEMENTS IN PROCESSES FOR DYEING OR COLOURING PAPER PULP
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by Benjamin Nickels, junior, at the Office
of the Commissioners of Patents on the 15th November 1879.
BENJAMIN NICKELS, junior, of Bolton, in the County of Lancaster, Analytical
Chemist. "IMPROVEMENTS IN PROCESSES FOR DYEING OR COLOURING PAPER PULP."
This Invention relates to improvements in the processes employed for dyeing or
colouring paper while in the form of pulp, with logwood, the colour produced being
of a blue or purple shade.
In colouring paper pulp with logwood as now practised by paper makers, the
material to produce the paper having been brought to the condition of pulp, is
either sized and "loaded" and then dyed, or it is dyed first and sized and "loaded"
afterwards.
The operation of dyeing is thus conducted :-
The pulp having been brought to a suitable condition, logwood in the form of a
thick paste is emptied into the engine containing the pulp until a sufficient depth
of colour is obtained, the whole is then allowed to revolve for some time and when
thoroughly dissolved and disintegrated a small quantity of alum is put in to “strike”
or "spring" the colour.
"
According to the amount of alum put in so is a blue" or "red" shade formed;
to the whole is sometimes added a little copperas, and after a further digestion the
mass is suitably diluted with water, and run on to the paper machine.
By this process is formed the ordinary and well known purple paper, which is
known in the trade as "purple shop."
My improved process of dyeing the pulp is as follows:-
Having brought the materials into the condition of pulp as aforesaid, I proceed
to size and "load" and then colour it, or I may colour it first and size and "load"
it afterwards. Into the pulp I put a small quantity of logwood either in the
condition of paste or otherwise, and having allowed this to become thoroughly
dissolved and the pulp intimately saturated with it, 1 add a small quantity of alum
over and above the quantity required for the sizing process. According to the
amount of alum added depends the shade of the ultimate colour.
I now add a small quantity of nitrate of iron, either the per-nitrate or the pro-
nitrate or a mixture of both according to the shade of colour I wish to produce.
A deep purple colour is immediately produced and after the lapse of a short time
the pulp can as usual be converted into paper.

page_text: My improvements consist in the use of nitrate of iron, or all salts formed by the
action on or union of iron and nitric acid in conjunction with logwood, the nitrate of
iron serving as a mordant to the pulp, and I may or may not use alum as part of the
dyeing process, which may or may not require the aid of heat either dry or from
steam as occasion should require, and the nitrate of iron, if desired may be mixed
with the logwood and the alum, and be introduced into the pulp all at the same
time.
By means of my improved process a very superior paper as regards colour is
produced at a very much less cost, the action as compared with the old process
being as follows:-
The purple colour now made results from the presence in the paper of an enormous
quantity of logwood, which by reason of its minute state of division imparts its own
colour to the paper, the brown colour of the logwood being simply changed to purple
by the addition of a small quantity of alum which acts as a weak mordant, the
whole being slightly darkened by the addition of copperas. Now in my improved
process the nitrate of iron which is added either before or after the logwood, acts as
a powerful mordant, liberating or "striking" all the colour which is contained in the
logwood, which where my improved process is not followed remains locked up in
the dye, an enormous percentage being consequently lost.
My improvements in the dyeing of. paper pulp as above described has also the
advantage that in place of the liquor running from the wire of the paper machine
highly coloured and thus becoming a source of pollution and a nuisance it is when
my plan is followed perfectly or nearly colourless.