IMPROVEMENTS IN THE MANUFACTURE OF MINERAL WHITE SUBSTANCES SUITABLE FOR DRESSING AND FACING PAPER PROAL
Year: 1881

page_text: LETTERS PATENT to Thomas Henry Cobley, of Dunstable, in the County of
Bedford, for an Invention of "IMPROVEMENTS IN THE MANUFACTURE OF
MINERAL WHITE SUBSTANCES SUITABLE FOR DRESSING AND FACING PAPER
PROVISIONAL SPECIFICATION left by the said Thomas Henry Cobley at
the Office of the Commissioners of Patents on the 25th November 1881.
THOMAS HENRY COBLEY, of Dunstable, in the County of Bedford. "IMPROVE-
MENTS IN THE MANUFACTURE OF MINERAL WHITE SUBSTANCES SUITABLE FOR
DRESSING AND FACING PAPER AND FABRICS."
My Invention relates to the manufacture in a simple and economical manner of
mineral white substances, which can be employed for the purposes for which
analogous substances are often now employed, as, for example, for mixing with
paper pulp to give body to the paper, for coating paper to receive colour printing,
for sizing or dressing fabrics, or for mixing with asbestos or other refractory
material for making firo proof goods. For this purpose I decompose sulphate of
magnesia, which may be native sulphate or kieserite, by means of hydrate of lime,
causing a reaction by which is produced a precipitate of magnesia mixed with
sulphate of lime. Or otherwise I precipitate sulphate of lime from a solution of
chloride of calcium treated with a solution of sulphate of magnesia, thus recovering
chloride of magnesium in solution, which, treated with hydrate of lime, gives a
precipitate of hydrate of magnesia and a solution of chloride of calcium, the latter
solution being available for fresh treatment with sulphato of magnesia. When
chemical impurities, such as compounds of iron, exist in the solutions, I precipitate
them in the first place, and mechanical impurities I remove by filtration. The
precipitates may be separated by filtration or decantation or by means of a filter
press. The sulphate of magnesia precipitate is improved by the addition of a small
percentage of sulphuric acid, or alum, or of both. The hydrate of magnesia
precipitate mixed with alumina is particularly applicable as a paste for cotton
fabrics not susceptible of mildew, or to mix with paper pulp, or to give paper a
surface to receive colour printing. The sulphate of lime precipitate is also
applicable with great advantage for mixing with paper-pulp. In all cases I prefer
to use saturated solutions, and when treating the magnesian solutions to apply
heat. The precipitates before use should be washed and pressed, and when they
have an acid reaction the acid should be removed by hot water or steam.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Thomas Henry Cobley in the Great Seal Patent Office on the
24th May 1882.
"IMPROVE-
THOMAS HENRY COBLEY, of Dunstable, in the County of Bedford.
MENTS IN THE MANUFACTURE OF MINERAL WHITE SUBSTANCES SUITABLE FOR
DRESSING AND FACING PAPER AND FABRICS."
My Invention relates to the manufacture in a simple and economical manner of
mineral white substances, which can be employed for purposes for which analogous
substances are often now employed, for example, for mixing with paper pulp to
give body and finish to the paper, for coating paper to receive colour printing, for
sizing or dressing fabrics, or for mixing with fire clay or other refractory material
for making fireproof goods. For this purpose I take a solution of sulphate of
magnesia, for economy's sake native sulphate of magnesia or kieserite, and to this
I add hydrate of lime (carefully prepared by levigation so as to be entirely free
from gritty particles), and this is continuously added under agitation or stirring
until precipitation censes. The mixture is then allowed to settle and the liquid is
run off, leaving a paste; or while the precipitate is forming the mixture may be
passed through a filter press, by which means the white precipitate can be obtained
in the form of firm cakes. The white thus prepared is a mixture of precipitated
sulphate of lime and hydrate of magnesia. When it is employed for coating the
surface of paper to receive colour printing, as in the manufacture of paperhangings,
the addition of a small quantity of alum solution improves its quality. From 5%
to 10% of alum is what I have found to answer well. Care must be taken that
the materials used are free from iron and other impurities. The iron may be
removed by precipitation, the mechanical impurities by filtration; heat materially
facilitates the operation.
A
To manufacture the second quality of white particularly adapted for the paper-
maker for giving body and finish to the paper, I proceed as follows:-I take as
before a solution of sulphate of magnesia, and add this to a solution of chloride of
calcium. The solutions should be as saturated as possible and used warın.
precipitate of pure flaky sulphate of lime ensues which has the property of drying
up with a pearly lustre, and is an excellent addition to pulp in papermaking. The
precipitate may be rendered more flaky in character by an addition of sulphuric
acid to the precipitant. The precipitate, after being passed through a filter press,
is ready for use.
The liquor from this precipitation consists of chloride of magnesium, which may
be employed to form a paste for use in finishing cotton goods and other textile
fabrics for the prevention of mildew. This paste I make by adding to the chloride
of magnesium liquor pure hydrate or carbonate of lime, thus obtaining a
precipitate, which may be mixed with alumina. But in order to simplify the
process and obtain alumina in a comparatively pure condition I proceed by
preference as follows:-To the chloride of magnesium liquor I add about 10 per
cent. of chloride of aluminium, and then precipitate by the addition of hydrate or
carbonate of lime. The precipitate is separated from the liquor by pressure, and
the liquor, which consists of chloride of calcium, is used for the manufacture of fresh
quantities of the second quality of white, as herein before described, so that the
process can be rendered continuous. In order to concentrate the liquors to the
point necessary for a good flaky precipitate, they should be boiled down, or they
may be strengthened by the addition of fresh chloride of calcium.
When acid is employed the precipitate should be washed with lime water or
steam.

page_text: Having thus described the nature of my Invention, and in what manner the
same is to be performed, I claim,―
First. The manufacture of mineral white by treatment of sulphate of magnesia
with hydrate of lime, substantially as herein described.
Second. The manufacture of mineral white by treatment of chloride of calcium
with sulphate of magnesia, substantially as herein described.
Third. The manufacture of white paste for preventing mildew of fabrics by
treatment of chloride of magnesium with hydrate or carbonate of lime and addition
of alumina, substantially as herein described.
In witness whereof, I, the said Thomas Henry Cobley, have hereunto set
my hand and seal, this Twenty fourth day of May, in the year of our Lord
One thousand eight. hundred and eighty two.
T. H. COBLEY. (L.S.)