Improvements in the Preparation of Cellulose for use in the Manufacture of Paper and for other Purposes.
Year: 1898

page_text: Date of Application, 18th Mar., 1898-Accepted; 30th July, 1898
Improvements in the Preparation of Cellulose for use in the
Manufacture of Paper and for other Purposes.
I, FRIEDRICH BUHLER, of 78, Hohenzollern Strasse, in the City of Cassel, in the
Kingdom of Prussia, and German Empire, Civil Engineer, do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:-
-
Alkaline or acid lyes have hitherto been exclusively employed for making cellu-
lose or wood pulp from wood but these methods of manufacture exhibit
many draw-
backs. In the manufacture of cellulose by means of alkaline lyes, in which cut
up pieces of wood are boiled in closed vessels at a high temperature always with
soda lye, the wood pulp obtained must always be bleached before it can be used
for the manufacture of paper. The lye employed is also expensive, and expensive
apparatus is necessary for obtaining the woody fibre from wood by this method of
treatment.
In more recent times this alkaline lye has been replaced by an acid lye, and in
fact a solution of sulphite of lime or sulphite of magnesia in sulphurous acid is
mainly employed. This method (the so-called sulphite process) in which the dis-
integrated wood is boiled under pressure in lead lined vessels, enables the material
obtained to be made into ordinary paper without previous bleaching, but this
method of manufacture shows other defects. Thus for instance fumes, which have
a deleterious action on the workpeople and the vegetation in the neighbourhood of
the factory, always escape from the apparatuses and pipes employed, owing to
leakages, because sulphurous acid always exerts a deleterious influence on the
human organism and the vegetable kingdom. Further at each boiling of a certain
quantity of wood with sulphite lye, there always remains a certain quantity of
concentrated waste spent lye, and also during the washing of the manufactured
cellulose not inconsiderable quantities of waste or wash water result which are
impregnated with a decreasing quantity of sulphite lye, which all together are
ultimately discharged into streams and produce thereby serious evils. Such waste
lyes always containing sulphurous acid, destroy all fish when discharged into rivers,
and render the water incapable of being used for irrigating meadows, as it destroys
any plant life.
Both methods are also found to be somewhat impractical as each boiling re-
quires a very considerable time (16 to 50 hours), and further it is found that woods
rich in resin cannot at all be treated with sulphite lye because the resinous parts
surrounding the wood cells, the so called incrusting matter, cannot be entirely
removed.
All these drawbacks are removed by the present invention by an improved method
of treatment, in which the disintegrated wood is boiled during a period of 3 to
12 hours with a given quantity of tar oil, phenol or ethers of the phenols, and
thus the wood cells are perfectly freed but the cellular tissue is not in the least
attacked but is on the contrary converted into a condition which allows of the fibre
being directly converted into paper or the like. The boiling may in this process
take place in an open boiler as there is only a strongly pronounced tar odour evident
and the gases given off are absolutely non-deleterious to mankind and the neigh-
bourhood, and are quite inoperative as regards metals.

page_text: The boiling of the wood with the above mentioned liquid may of course take place
under pressure or in vacuo, which are both equally possible.
The liquid employed for boiling the wood is a product of wood or coal distillation
and is preferably obtained from the tar produced by this dry distillation. In order
to obtain it wood or coal tar is distilled and the benzole, naphtha and water are
first driven off which takes place at about 1600-180°. The so-called tar oils which
become apparent from 180 to 320° C. are then distilled off, which tar oils consist
mainly of phenols and their allied substances, that is to say a group of organic
substances having the general formula CHO and the derivatives CH, (OH),
CH(OH), CH, (OH) and so forth. These are mainly phenol, tricresyl, guaiacol,
creosol and other like phenols.
The boiling of the disintegrated wood in the boiler may take place by direct
firing or by heating by means of superheated steam at a temperature of about
150° C., any volatilised products of condensation being caught and recovered in a
condenser in order to be again employed directly or later on.
When the boiling has lasted for the necessary time, which according to the kind
of wood is from 3 to 12 hours, the liquid is discharged from the boiler and the
boiled material also drops out at the end of the boiler as soon as the door provided
there is opened. The boiled material is then conveyed to a pressing apparatus such
as squeezing rollers which loosen the still outwardly hard wood particles and
expel any tar oil still adherent. The cellulose or wood pulp thus obtained is con-
veyed by an elevator or other suitable apparatus to an extractor of any known
form of construction with the object of extracting all the remaining oil, and here
it is entirely freed from tar oil by means of a suitable solvent. The material is then
ready for further treatment into paper or the like paper product.
The present improved process is characterized by any cheap wood such as pine,
fir or pitch pine being capable of being utilized. The time required for boiling is
also short and no deleterious gases or waste water are discharged which exert a
deleterious action on human health or plant life.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:-
A process for the preparation of cellulose, consisting in treating the raw material
with tar-oils, the phenols or ethers of the phenols at high temperature, substan-
tially as described.