IMPROVEMENTS IN TREATING VEGETABLE SUBSTANCES, CHIEFLY APPLICABLE TO THE MANUFACTURE OF PAPER PULP AND FIBRES
Year: 1866

page_text: LETTERS PATENT to William Edward Newton, of the Office for Patents,
66, Chancery Lane, in the County of Middlesex, Civil Engineer, for the
Invention of "IMPROVEMENTS IN TREATING VEGETABLE SUBSTANCES, CHIEFLY
APPLICABLE TO THE MANUFACTURE OF PAPER PULP AND FIBRES."-A commu
nication from abroad by Benjamin Chew Tilghman, of Philadelphia,
Pennsylvania, United States of America.
PROVISIONAL SPECIFICATION left by the said William Edward Newton:
at the Office of the Commissioners of Patents, with his Petition, on the
9th November 1866.
I, WILLIAM EDWARD NEWTON, of the Office for Patents, 66, Chancery
Lane, in the County of Middlesex, Civil Engineer, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN TREATING VEGETABLE
SUBSTANCES, CHIEFLY: APPLICABLE TO THE MANUFACTURE OF PAPER PULP AND
FIBRES to be as follows:-
.
This Invention consists in a process of treating wood, esparto, and other
grasses, flax, hemp, straw, and other vegetable substances which contain
fibres with a solution of sulphurous-acid in water, which is heated under
[Price 8d.1

page_text: pressure in a close and strong vessel until the incrusting or cementing matter
existing between the fibres is dissolved or softened so as to be removeable by
washing and the mechanical processes usually employed, and the fibrous
material is thus rendered suitable for the manufacture of paper pulp or for
other purposes, according to the nature of the substance used. The addition
of a quantity of sulphite or bisulphite of lime or other suitable base to the
solution of sulphurous acid is advantageous. After the acid liquid has been
used on the vegetable substance it is to be run off and boiled, so as to expel
the sulphurous acid gas, which is to be absorbed by cold water and re-used.
The sulphite of lime remaining in the solution will be precipitated during the
boiling, and may be re-used. The fibrous material is to be well washed to
free it from acid and soluble matter, and is then to be treated by the ordinary
processes of manufacture according to its nature and intended use. Many
kinds of fibres are considerably bleached by this process. The soluble extract
containing the starchy, gummy, and saliue constituents of the plants may be
utilized in various ways in the arts and in agriculture.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Edward Newton in the Great Seal Patent Office
on the 9th May 1867.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
EDWARD NEWTON, of the Office for Patents, 66, Chancery Lane, in the County
of Middlesex, Civil Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Ninth day of November, in the year of our Lord
One thousand eight hundred and sixty-six, in the thirtieth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said William Edward Newton, Her special licence that I,the said-William
Edward Newtou, my executors, administrators, and assigns, or such others as
I,the said William Edward Newton,my executors,administrators,and assigns,
should at any time agree with, and no others, from time to time and at:all
times thereafter.during the term therein.expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for "IMPROVE
MENTS IN TREATING VEGETABLE SUBSTANCES, CHIEFLY APPLICABLE TO THE MANU
FACTURE OF PAPER PULP AND FIBRES," being a communication from Benjamin
Chew Tilghman, of Philadelphia, United States, upon the condition (amongst

page_text: others) that I, the said William Edward Newton, my executors or adminis-
trators, by an instrument in writing under my, or their, or one of their hands
and seals, should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and cause
the same to be filed in the Great Seal Patent Office within six calendar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said William Edward Newton, do hereby
declare the nature of the said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by the
following statement (that is to say):-
-
This Invention consists in a process of treating wood, esparto, and other
grasses, flax, hemp, straw, and other vegetable substances which contain
fibres with a solution of sulphurous acid in water, heated in a close vessel
under a pressure sufficient to retain the acid gas until the intercellular or
cementing matter existing between the fibres is disolved, either partially or
wholly, as may be desired, and a fibrous product is obtained suitable for the
manufacture of paper pulp or fibres, or for other uses according to the nature
of the material employed. The addition of sulphite or bisulphite of lime, or
other suitable base to the acid solution, tends to make the fibrous product of
a whiter color and more easily bleached.
The following is a method of carrying the Invention into effect, taking, for
example, the case of hemlock or poplar wood to be used for.paper pulp :-
A solution'of
The whitest parts of the wood are to be selected to make white paper, and it
is to be cut across the grain into slices, about one-eighth to one-quarter of
an inch long. A strong iron vessel of any convenient size and shape lined
with lead and provided with a steam jacket and with the necessary pipes,
cocks and man-holes for filling and emptying the charge, and with gauges,
safety valves, and thermometers to indicate height of liquid pressure and
temperature, is about two-thirds filled with the sliced wood.
sulphurous acid in water of about specific gravity 1.025 to 1.035 at sixty.
degrees Fahrenheit in which a quantity of sulphite of lime has been disolved
sufficient to raise its density to about specific gravity 1.07 to 1.08 is then run
in until the vessel is nearly full, allowing for the absorption of the liquid by
the wood and its expansion by heat, so that the wood may be kept constantly
covered by the liquid during the operation. The vessel is then closed and.
heat is applied by means of the steam jacket, until the temperature of the.
liquid is about two hundred and sixty degrees Fahrenheit, at which; it is
kept during from six to eight hours.. The steam is then shut off from the
steam jacket and fresh water is forced into the top of the vessel, the acid.

page_text: solution being at the same time allowed to escape gradually from below into
a covered lead lined tub where it is boiled by steam until the sulphurous acid
gas is expelled. This gas is conveyed by a pipe to a suitable condenser
where it is absorbed by cold water, so that it may be re-used on another charge
of wood; a quantity of sulphite of lime will be deposited during the boiling
which may be re-used. Instead of driving off the sulphurous acid gas
by boiling, or after part of it has been thus driven off, the acid may be
neutralized by the addition of hydrate of lime, forming sulphite of lime, which
can be re-used; after being washed the woody substance is left to drain, and
then if on examination it is thought necessary in order to complete the
separation and bleaching of the fibres, it is to be again treated with a fresh
charge of sulphurous acid and sulphite at a temperature of from two hundred
and-sixty degrees to two hundred and eighty degrees Fahrenheit during from
'three to five hours; then the acid liquid is to be run off as before, and the
fibrous product is to be washed until all the acid and soluble matters are
extracted'; it is then taken out of the lead lined vessel and beaten into
pulp by the ordinary machines, if not sufficiently white it is to be bleached in
the usual manner. When making pulp for ordinary: paper the treatment
should be repeated as often as necessary with fresh acid solutions until every
thing soluble has been extracted from the wood so as to leave the fibres clean
and separable into pulp by a slight mechanical rubbing, many kinds of
vegetable fibrous substances are considerably bleached by this treatment, the
whiter varieties of sonie woods, hickory and hemlock, for example, become
almost perfectly white. The action of the acid solution in dissolving the
intercellular or cementing matter, appears to be gradual and progressive, first
loosening the substance into coarse fibres, and then reducing these into finer
and still finer constituents, until perfect pulp is produced. Wood or other
vegetable fibrous substance treated so as to dissolve its cementing matter only.
partially will be found capable of being reduced by mechanical beating and
rubbing to a mass of fibres or sort of coarse pulp; applicable to uses where
strength and stiffness are desired, such aswrapping paper,pasteboard, millboard,
papier mâché; &c: The solvent action of the hot acid liquid on the wood may:
be made more rapid by causing it to circulate freely through the pores of the mass
by any of the usual methods, either mechanical; such as pumps, stirrers, or
agitators,orby causing a column of the liquid to be more highlyheated than the
rest so as to rise to the top and diffuse itself, or where the scale of manufacture
is sufficiently large by having several vessels filled with the material throughi
which the hot acid liquid is forced to pass in succession so that fresh acid!
solution. is applied to wood already nearly exhausted of soluble matter

page_text: and the nearly saturated' acid solution is brought into contact with fresh
wood.
These arrangements are familiar to chemical engineers and need not be
further described. When making paper pulp of cane, bamboo or palmetto,
or of esparto or other grasses, or of straw reeds or other annual plants, the
operation is performed as already described, and they are generally more
rapidly acted on than wood. Cotton, linen, and hempen rags, ropes, and
analogous substances, may be advantageously treated in this manner, and will
be rendered more easy to reduce into pulp by the usual mechanical means.
With all kinds of materials it is better to operate at as low a. temperature
and with as weak acid solutions as is compatible with a practical rapidity of
working. When flax, hemp, or other long fibred plants are to be treated to
obtain fibres for spinning, I operate in the manner above described, but to
avoid too much disintegration and weakening of the fibre care must be taken
to graduate the extent of the action according to the nature of the material
used and the effect desired to be produced. The dissolving action of the acid
solution appears to take effect first upon the matter cementing the long
compound fibres to each other and to the stem of the plant, and next attacks
the cementing matter of the long compound fibres themselves, reducing them
into a number of shorter and finer fibres, if the action is still longer continued
these are still further disintegrated, and become at last so short and fine as to
be unfit for spinning and only suitable for paper pulp. If, on the other hand;
the dissolving action be not carried far enough, the long fibres do not separate
readily from each other and from the stem and skin of the plant. The
attention of the operator must therefore be given to arrest the action at the
precise point most suitable for the object he has in view, whether a fibre
as strong as possible, even though somewhat less fine and less easy to
clean, or a finer and' cleaner fibre, but somewhat shorter and weaker.
Different kinds of plants and of different degrees of maturity require different
degrees of action of the solvent liquid to produce a given result:
The progress of the operation must therefore be watched, and when the
desired' degree of disintegration is obtained' should' be ascertained by taking.
samples from time to time by means of a rod ending in a corkscrew, and
working through a stuffing box and stop cock in the side of the vessel as is
well understood by engineers.
In order to render the operation more gradual, comparatively low tem-
peratures; say from two hundred degress to two hundred and twenty degrees
Fahrenheit should be employed, and very weak solutions of sulphurous' acid
of about specific gravity 1002' to 1'004, to which is to be added'a quantity of

page_text: sulphite of lime sufficient to raise its density to about specific gravity 1.005
to 1.008. Under these conditions may be obtained a medium degree of
loosening and separation of the fibre of flax in about four hours. It is
desirable that plants of nearly uniform size and growth should be selected to
be operated on together, and they are to be left of their natural length and
not cut as in the case of wood for paper pulp. When about to treat a new
material it is better to ascertain by preliminary trials on small quantities the
length of time and degree of action best. adapted to the object desired, which
can afterwards be adhered to. When the treatment is finished the acid and
soluble matters are to be thoroughly washed out and the fibres are to be
manufactured in the usual manner.
Straw,grasses,osiers, young woods, and similar vegetable fibrous substances
treated in this manner so as to dissolve only partially the cementing substance
of their fibres will become more flexible and more suitable for making hats,
mats, baskets, and hoops, and for other uses where pliability is required. I
do not confine myself to the kind of apparatus or mode of working above
described, as the Invention can be carried into effect in any convenient appa-
ratus by which the substance which contains the fibre can be digested in a hot
solution of sulphurous acid in a close vessel under pressure as to prevent the
escape of the acid gas.
Many forms of apparatus are in common use or have been described and
published for washing and bleaching fibrous substances, and for making paper
pulp by boiling or digesting rags, wood, straw, &c., in hot alkaline and other
solutions, which can readily be adapted by chemical engineers for working
this Invention. The volatility of the acid and its corrosive action on some
metals must be provided for, and the inside of the apparatus should be lined
with lead or other suitable material. The vessels used when operating with
the acid solutions and the temperatures above described for treating wood for
paper pulp should be about the strength usually allowed for steam boilers
working at a pressure of one hundred pounds per square inch. The density
of acid solution, the degree of heat, and the length of time found useful in
practice has been stated, but I do not confine myself thereto, as these con-
ditions may be greatly varied, and may to some extent be substituted for each
other. The stronger the acid solution the more rapid is the action at a given.
temperature; also the higher the temperature the more rapid is the action
with a given density of acid solution; with weak acid and comparatively low
temperature the effect can be produced by continuing the digestion a suffi-
ciently long time, or by using a solution saturated when cold with acid gas.
at or above common atmospheric pressure the action may be made. more

page_text: rapid; care must be taken, however, that the temperature be not raised high
enough to cause a blackening action on the vegetable substance, which is apt
to take place with some materials at about three hundred degrees Fahrenheit,
and more readily in the treatment with the first charge of acid than with the
succeeding ones. It is more prudent to work the first charge on wood at
not over two hundred and sixty degrees Fahrenheit,and the subsequent charges
at not over two hundred and eighty degrees Fahrenheit. In the second and
subsequent doses of acid solution on a charge of wood, a smaller proportion
of sulphite may be used than in the first dose. Where the first extraction
has very nearly exhausted the soluble matter, a solution of sulphurous acid
may be sometimes used alone without any sulphite for the subsequent doses.
The solution of sulphurous acid in water at the requisite temperature appears
to be the efficient agent in. dissolving the intercellular or cementing matter
of the vegetable fibrous substance, and where the color of the product is.of
no consequence the operation may be performed with the sulphurous acid
solution alone without the addition of sulphite. In this case a reddish brown
color is given to the resulting fibrous product, and the acid solution will be
found to contain a quantity of free sulphuric acid which has been formed
during the operation by the oxidation of a portion of the sulphurous acid.
The presence of a sulphite in the acid solution prevents this reddening effect,
and in case of many substances a considerable bleaching of the fibrous
product takes place. The probable mode of action of the sulphite is to
present a base with which the sulphuric acid combines as soon as it is formed,
and is thus prevented from further action. There are other classes of salts
which operate to some extent in the same way as the sulphites, but are.less
cheap and convenient. The requisites are, first, that the salt should not be
capable of being decomposed by the solution of sulphurous acid at the
temperature and pressure employed; second, that it should be capable of
being decomposed by a weak solution of sulphuric acid at the temperature
and pressure employed; third, that the acid thus set free should not have
the property of coloring the fibre at the temperature and pressure employed.
Many of the salts of the weaker acids (acetates for example) would fulfil
these conditions to a considerable extent, but as they are more expensive
than the sulphites, there is no inducement to use them. Besides its cheap-
ness the sulphite of lime has the advantage of furnishing an equivalent of
sulphurous acid when decomposed by the sulphuric acid, and is also very
readily recoverable from the spent acid solutions. I prefer to use a quantity
of sulphite of lime sufficient to insure that some of the salt shall be present
in the acid solution during the whole operation, and that some shall remain

page_text: undecomposed after the action of the fibrous substance is completed. I
have sometimes used solutions of sulphurous acid saturated with sulphite,
and sometimes have used sulphite in powder mixed among the wood, &c.
to be operated upon. After the sulphurous acid has been driven off or pre-
cipitated the liquid extract containing in a soluble form the products of the
saline and intercellular or cementing constituents of the plants may be
utilized in various ways in the arts or may be used as manure. It contains
a weak organic acid, somewhat resembling ulmic acid, and when boiled
down has some of the properties of gum.
Having now described the Invention which has been communicated to me
by my foreign correspondent as aforesaid, and having explained the manner
of carrying the same into effect, I claim the process herein set forth of
treating vegetable substances which contain fibres with a solution of
sulphurous acid in water, either with or without the addition of sulphites
heated in a close vessel under pressure to a temperature sufficient to cause
it to dissolve the intercellular or cementing constituents of such vegetable
substances, so as to leave the undissolved portion in a fibrous state suitable
for the manufacture of paper pulp, cellulose, or fibres, or for other purposes,
according to the nature of the material employed.
I also claim the use and application of sulphites or other salts of equivalent
chemical properties, as above explained, in combination with a solution of
sulphurous acid in water as an agent in treating vegetable substances which
contain fibres when heated therewith in a close vessel under pressure to a
temperature sufficient to cause the said acid solution to dissolve the inter-
cellular or cementing constituents of the said vegetable substances.
In witness whereof, I, the said William Edward Newton, have here-
unto set my hand and seal, the Eighth day of May, in the year of our
Lord One thousand eight hundred and sixty-seven.
Witness,
J. W. MOFFATT,
66, Chancery Lane.
W. E. NEWTON. (L.B.)