Paper Making and Analogous Purposes.
Year: 1884

page_text: Paper Making and Analogous Purposes.
I CHARLES WILLIAMS KNOWLES of Windsor, Nova Scotia, temporarily of
N° 3 Red Cross Street, Liverpool in the County of Lancaster Stationer do hereby
declare the nature of my invention for AN IMPROVED PROCESS OF PREPARING
SULPHATE OF LIME FOR USE IN PAPER MAKING, AND ANALOGOUS PURPOSES, to be
as follows:
The object of the present invention is to simplify the process and reduce the
cost of preparing sulphate of lime for use in the manufacture of paper.
Attempts have been made to employ anhydrous gypsum in a powdered state in
the manufacture of paper, but this preparation of lime has been found impracticable,
owing to the difficulty of properly mixing the powder with the paper pulp in the
pulp beating engine.
Preparations of lime in a plastic state have also been obtained by chemical
processes, but although such preparations are suitable for the purpose, they involve
the use of acids, and are more or less costly to manufacture.
By my improved process however I am enabled to produce a plastic preparation
of sulphate of lime suitable in all respects for use in the manufacture of paper
without the use of acids, at far less cost thun heretofore.
In carrying out my invention I take sulphat of lime in any of its various forms
such as crystallized selenite, alabaster, etc., free from any earthy impurities and
reduce it in a suitable machine to a condition proper for grinding. The material is
then ground in a suitable mill to a very fine powder and passed through a screen.
is then subjected to a temperature of heat sufficient to drive off all the artificial
water, and is thereby reduced to an impalpable powder.
It
This anhydrous powder is then placed in an agitating tub or vat and mixed with
8 times its weight of water, the water being free from any vegetable or chemical
impurities, and kept in a continual state of agitation for the space of 30 minutes;
at the end of which time the water will have thoroughly pentrated and combined
with the particles of sulphate of lime and be completely disintegrated.
This mixture while in a state of agitation, is then pumped immediately into
hydraulic filtering presses, and the precipitate is obtained in the form of a solid

page_text: cake that can be easily handled. It is afterwards subjected to a drying process in
a heated room, and from 10 to 20 % more of moisture evaporated therefrom. It is
then in a sufficiently dry state to be conveniently packed and transported to the
paper mills.
The manner in which this plastic preparation of disintegrated sulphate of lime
is used in the manufacture of paper is as follows:-
--
The cakes or lumps of the prepared substance without any further preliminary
treatment whatever are thrown into the beating engine, and immediately dissolve,
readily intermixing with the fibres of the paper pulp. There is no necessity for
the tedious process of mixing and agitating the material with water and starch in &
separate machine, as is the case with clays and all mechanically prepared mineral
substances used in the manufacture of paper and a considerable economy in money
and time results.
An advantage incidental to my process of manufacture is, that the preparation
is brought into the market in a form ready for use, and well adapted for packing
and transport without injury.

page_text: •
ICGOOD Offropating owpate of me for UB8 In
Paper Making and Analogous Purposes.
I CHARLES WILLIAMS KNOWLES of Windsor, Nova Scotia, temporarily of
N° 3 Red Cross Street, Liverpool in the County of Lancaster, Stationer, do hereby
declare the nature of my invention for "AN IMPROVED PROCESS OF PREPARING
SULPHATE OF LIME FOR USE IN PAPER MAKING AND ANALOGOUS PURPOSES," and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
The object of the present invention is to simplify the process and reduce the cost
of preparing sulphate of lime, and to put into the market in a form suitable for
use in the manufacture of paper and analogous purposes such as the filling of cotton
goods.
Attempts have been made to employ anhydrous gypsum in a powdered state in
the manufacture of paper, but this preparation of lime has been found impracticable
owing to the characteristics of this powdered gypsum and the difficulty of properly
mixing it with the paper pulp in the pulp beating machine.
Preparations of lime have also been obtained by chemical processes or by
processes partly mechanical and partly chemical, but although such preparations
are suitable for the purpose, they involve the use of acids and are more or less costly.
to manufacture and injurious to the machinery.
By my improved process however I am enabled to produce a preparation of
sulphate of lime in a form suitable for packing and transport, and of a character
suitable in all respects for use in the manufacture of paper, without the use of acids
or chemical treatment, and at far less cost than heretofore.
In carrying out my invention I take sulphate of lime in any of its various
forms such as crystallized selenite, alabaster, &c., free from any earthy impurities
and reduce it in a suitable crushing mill or machine to a condition proper for
grinding. The material thus reduced or crushed is next ground in a suitable mill
and preferably between a pair of horizontally arranged stones, to a very fine
powder, and is then calcined. An impalpable powder from which all moisture has
been driven off, results from this treatment, and I preferably subject the powder
at this stage to a screening process to remove any impurities which it may contain.
In some cases I screen it both before and after calcination.
This anhydrous powder is then mixed with about ten times its weight, more or
less of water, in an agitating, tub or vat, care being taken that the water is free
from any vegetable or chemical impurities. The beaters are started directly the
powdered sulphate of lime is introduced into the tub or vat, and the mixture is.
kept in a continual state of agitation for the space of from 30 to 45 minutes; at
the end of which time the water will have thoroughly penetrated and combined.
with the particles of sulphate of lime and have effected its complete disintegration.
I preferably mix a considerable quantity of powdered sulphate of lime and water
at a time, taking say half a ton of the anhydrous powdered sulphate of lime, and
throwing it into an agitating vat or tub containing some 1500 gallons of water,

page_text: 'ו'
the agitators or beaters being set in motion before, or so soon as, the sulphate of
lime is thrown in and kept at work until the bydration and consequent disinte-
gration of the lime is completed. The mixture is then immediately run into a
container or receiver, and, before it has had time to set or settle, is forced through
a filter press and the surplus moisture thereby extracted. I preferably conduct
the mixture through or along a trough of some 80 feet in length before running it
into the receiver, as by this means an opportunity is given for the heavier particles
to fall and remain upon the bottom of the trough whence they may be subse-
quently removed by scraping, and I preferably employ air pressure to force the
mixture from the receiver through the filter press. In practice I use an ordinary
air compressor driven by a steam engine on the same bed plate and I connect the
receiver with the said air compressor by an air supply pipe entering near its upper
part and with the filter press by a discharge pipe leading from its lower part;
suitable cocks or valves being fitted to the said supply and discharge pipes
respectively.
This arrangement I find works better and is more easily kept in order than an
ordinary steam pump which passes the mixture direct through its pumping
cylinder.
I would remark that I force the mixture through the filter press before it has
had time to settle, and I thus obtain solid cakes of disintegrated sulphate of lime
in a more or less plastic and binding state and of thoroughly uniform consistency.
In addition to the screening which the powdered sulphate of lime undergoes prior
to being mixed with the water, I pass the mixture of sulphate of lime and water
through a wire screen of the finest gauge before it enters the receiver, and thus
I ensure that nothing in the shape of lumps or gritty, impurities can possibly pass
into the filter press and become incorporated with the resulting cakes of disinte-
grated sulphate of lime.
The solid cakes or slabs of disintegrated sulphate of lime are then removed from
the press and subjected to a drying process in a heated room or kiln, and from
20 to 30% more of moisture evaporated therefrom. They are then in a sufficiently
dry state to be conveniently packed and transported to the paper mills, and are in
a condition and form in which they can be easily and conveniently placed in the
market.
If preferred the cakes may be re-ground in an ordinary flour mill into an
impalpable powder and used in the same way as the lumps or cakes, in the
manufacture of paper or for analogous purposes.
The temperature at which I effect this drying of the prepared sulphate of lime
is about 170° Fahrenheit, and I prefer that only some 15 per cent of moisture
should remain in the cakes at the close of the drying operation.
This improved preparation of sulphate of lime is characterized by its extreme
whiteness, its silkiness to the touch, its freedom from all grit and impurities, and
its binding properties.
It is important that the mixture of powdered lime and water be run off and
pressed while in a thoroughly commingled state, as otherwise the preparation will
lose its binding property and the cakes will crack and crumble and fall to pieces
when removed from the filter press thus presenting difficulties to the completion of
the process, and the bringing of the preparation into the market in a suitable form.
An essential feature of my invention therefore consists in subjecting the liquid
preparation of sulphate of lime above described to pressure for the removal of the
surplus water immediately after the mixing and agitating process is completed,
and thereafter to a further drying operation.
My preparation of sulphate of lime is of better colour than any preparation of
china clay now in the market and requires no screening prior to use.
"
The manner in which this preparation of disintegrated sulphate of lime is used
in the manufacture of paper is as follows:-
The cakes or lumps of the prepared substance, without any further preliminary
treatment whatever, are thrown into the beating engine and immediately dissolve;

page_text: readily intermixing with the fibres of the paper pulp. There is thus no necessity
for the tedious process of mixing and agitating the material with water and starch
in a separate machine, as is the case with clays and all mechanically prepared
mineral substances used in the manufacture of paper, and a considerable economy
in money and time results.
One great advantage of my process of manufacture is, that the preparation is
brought into the market in a form ready for use and well adapted for packing and
transport without injury to itself or damage to other goods, and if necessary can
readily be reduced to powder before or after delivery.
By using sulphate of lime prepared substantially as above described in the
manufacture of paper, a larger proportion of it adheres to the pulp than heretofore
in the use of clays and such substances for similar purposes, and the quality of the
paper is improved, being made harder and whiter; and when calendered the paper
will have a beautiful enamel finish.
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 improved process of preparing sulphate of lime for use in paper making and
analogous purposes the said process consisting in subjecting a fluid mixture of
sulphate of lime, prepared in the manner set forth, and while still in a state of
agitation and thoroughly commingled, to the action of a filter press and to heat,
substantially as and for the purposes set forth.
NEWTON & SON,
Agents for the Applicant.