An Improvement in the Manufacture of Flax Pulp.
Year: 1899

page_text: Date of Application, 14th June, 1899-Accepted, 26th Aug., 1899
COMPLETE SPECIFICATION.
An Improvement in the Manufacture of Flax Pulp.
We, FRANCIS HICкMAN, Gentleman, of Bound Brook, Somerset County, New
Jersey, United States of America, and THE FRENCH-HICKMAN FLAX FIBRE
COMPANY LIMITED, a Corporation organised under Companies Acts, 1862-1890,
of 23, 24, and 25, Billiter Street, London, E.C., do hereby declare the nature of
this invention and in what manner the same is to be performed, to be particu-
larly described and ascertained in and by the following statement:―
This invention relates to the manufacture of paper and the production of new
and improved fibrous pulp derived from the flax plant or from the straw, waste,
tow and the like of flax, comprising substantially all the best fibres and the cellu-
losic tissue of the material treated, practically unweakened and free from
cementitious materials, gums, waxes and lignin.
It is well known that flax straw as a raw material, from which paper pulp
may be produced differs essentially from wood and the straw of other fibrous
plants, such for example as jute and hemp.
These differences may be defined generally as follows:
The fats and waxes of the flax plant are far more difficult to break down and
saponify with a caustic alkali solution than are those of wood, and the percentage
of fats and waxes in flax is much higher than in other fibrous plants. Hence,
it is necessary to provide a solution for flax which will efficiently break down
and eliminate this unusual quantity of fats and waxes, and which can overcome
their peculiarly refractory character without destroying or weakening the fibre.
It is believed that by no process hitherto known or discovered even including
the retting process for reducing flax, straw, to secure its best fibres alone, can
the fats and waxes be completely eliminated without at the same time greatly
weakening and partially destroying the fibres themselves.
In a long course of experiments it has been found that by combining a proper
percentage of sulphur with an aqueous solution of caustic soda the former unites
with or saponifies the more refractory fats and waxes of flax and retards the
oxidising effect of the caustic alkali, and thus the process of saponification is so
far modified and hastened under proper conditions of time, temperature and
pressure, that the fibrous material is protected from injury by oxidation, and
the encrusting matter such as lignin, fats, waxes and gums, is broken down
before the fibrous and cellulosic tissure can be attacked and weakened by the
alkali.
The percentage of fats and waxes in the flax plant varies under different
conditions of soil and maturity, consequently the percentage of sulphur necessary
in the caustic liquor varies accordingly.
While however the proper porportions of ingredients are thus variable within
the range of say ½½ per cent. to 5 per cent. by weight of sulphur with 99%
to 95 per cent. by weight of caustic soda, the proportions which we have generally
found most satisfactory are about 2 per cent. of sulphur to 98 per cent of caustic
soda. It may be said, however, that an excess of sulphur has no deleterious
effect upon the product. The liquor is prepared by boiling the sulphur in the

page_text: caustic soda solution in which it is readily dissolved. In carrying out the process
the material is treated with the liquor in a suitable digester under a pressure
of preferably 70 to 95 pounds per square inch, with a corresponding temperature
for about 4 hours. The conditions of temperature, pressure and time may
however be interchangeably varied without affecting the desired result.
For the purpose of cheapening the liquor sometimes sodium sulphate has been
used as a partial substitute for the caustic soda.
While the flax plant can be utilised in its pristine condition that is to say as
it is gathered from the fields, it is advantageous to "break" it beforehand by
machinery as in the well known process for making upholsterer's tow.
This process can also be employed with complete efficiency for the elimination
of the objectionable matters frequently found in manufactured flax products,
such as yarn, or linen fabrics of the lower qualities, their value and utility being
thus greatly enhanced.
The improved process above described differs from retting which only partially
removes the gum from the fibre, and only a small percentage of its contained
fats and waxes, whilst it destroys all cellulosic tissue other than the bast fibre.
It also differs from the bi-sulphite of lime process in being a saponification
process, which the bisulphite process obviously is not. It also differs from all
other saponification processes by reason of the presence in the reducing liquor
of sulphur in such form as to be available for union with the fatty constituents
distinguishing this pulp the saponification being thus so far promoted as to make
its completion possible before the bast fibres and other cellulosic tissue are
injured, a result not attained by the treatment of this pulp material with any
other liquor.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, we declare that what we
claim is:
1. A paper pulp consisting of the bast fibres and other cellulosic tissue of the
flax plant or straw freed from fats, waxes and other encrusting material.
2. The herein described process for treating flax straw to reduce it to a paper
pulp by dissolving sulphur in a hot solution of caustic soda, and then cooking
the flax straw in the liquor thus prepared, substantially as described.
Dated this 14th day of June 1899.