Improvements in the Manufacture of Alkali-cellulose.
Year: 1896

page_text: Improvements in the Manufacture of Alkali-cellulose.
I, CHARLES FREDERICK CROSS, of No. 4 New Court, Carey Street, in the
County of London, Consulting Chemist, do hereby declare the nature of this
invention to be as follows:-
The product known as alkali-cellulose has hitherto been manufactured by
mechanically disintegrating cellulose pulp or fibre and then treating this product
with a large proportion of caustic alkali, as much as 40 to 50 parts of caustic soda
to 100 parts of dry cellulose. The mechanical disintegration is troublesome and
expensive, and relatively inefficient; moreover, the quantity of alkali taken up by
the cellulose renders the application of alkali-cellulose, thus manufactured,
unsuitable for many purposes.
The object of my invention is to effect the disintegration by a cheap and simple
chemical process which brings the cellulose mechanically and chemically into a
condition such that it requires a very much smaller proportion of alkali to convert
it into alkali-cellulose suitable for use in other manufactures such, for instance, as
that of the substances now known as "viscose" and " viscoid."
For this purpose; I boil or digest the cellulose pulp or fibre with water acidulated
with about one per cent. of mineral acid such as sulphuric or hydrochloric acid.
If the digesting be carried on in a closed vessel to a pressure of several
atmospheres, the result is produced in considerably less time. Instead of digesting
the material with a considerable quantity of dilute acid, it may be merely
moistened with the acidulated liquor and after the surplus is squeezed out, by
rollers or otherwise, it is dried by heating.
The material treated in one or other of these ways is found to be completely
disintegrated, and after washing, if necessary, and pressing, it is treated with so
much of a solution of from 15 to 20 per cent. strength of sodium hydrate as converts
it iuto alkali-cellulose containing, in addition to water, about one part of sodium
hydrate to about 5 parts of dry cellulose. When the disintegrated cellulose is in
a moist condition the strength of the alkali solution should be greater than when
it is treated dry, by so much as will give with the water contained in the cellulose
a 15 per cent. strength of alkali solution, which is necessary for the production of
alkali-cellulose.
Raw fibrous materials, containing cellulose, may also be usefully treated by the
same process. The treatment with the dilute acid produces a structural dis-
integration and also so changes the chemical condition of the insoluble residue,
that the cellulose obtained is in a condition to be acted on by alkali, producing an
alkali-cellulose. The product in this case is more or less highly coloured, as, for
instance, when straw, jute or other lignified fibres are thus treated; but, after
treatment in the carbon bisulphide it yields a sulphocarbonate which dissolves for
the most part giving a dark coloured solution; which can be used in cases where
colour is of no consequence..
Dated this 2nd day of March 1806
ABEL & IMRAY,
Agents for the Applicant.

page_text: Improvements in the Manufacture of Alkali-cellulose.
I, CHARLES FREDERICK CROSS, of No. 4 New Court, Carey Street, in the
County of London, Consulting Chemist, 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 :-
The product known as alkali-cellulose has hitherto been manufactured by
mechanically disintegrating cellulose pulp or fibre and then treating this product
with a large proportion of caustic alkali, as much as 40 to 50 parts of caustic soda
to 100 parts of dry cellulose. The mechanical disintegration is troublesome and
expensive and relatively inefficient, moreover, the quantity of alkali taken up by
the cellulose renders the application of alkali-cellulose thus manufactured,
unsuitable for many purposes. The object of my invention is to effect the
disintegration by a modification of the well known cheap and simple process of
and treatment which brings the cellulose mechanically and chemically into a
condition such that it requires a very much smaller proportion of alkali to convert
it into alkali-cellulose suitable for use in other manufactures such, for instance, as
that of the substances now known as "viscose" and "viscoid." For this purpose,
according to one treatment, I boil or digest the cellulose pulp or fibre in an open
vessel for several hours with dilute hydrochloric acid, about 1 part HCI to 99 parts
water, or with dilute sulphuric acid, about 2 parts H,SO, to 98 of water. This is
continued until the cellulose is reduced to a brittle condition.
According to a modified treatment, instead of digesting the material with a
considerable quantity of dilute acid, I moisten the cellulose, when it is in the form
of sheets of pulp, or rags or paper, with dilute hydrochloric acid, about 1 part HCI
to 200 parts water. The excess of liquid is removed by squeezing or otherwise, and
the material is then dried as uniformly as possible at a temperature preferably
from 60° to 80° C.
The material may with advantage be treated under pressure in the following
manner. The cellulose, pulp, rags or paper is placed in a digester made of or
lined with acid resisting material and is covered with dilute acid, for example,
with five times its weight of aqueous sulphuric acid, 1 or 2 parts H,SO, to 100 parts
water, and the digester being tightly closed, the temperature is rapidly raised by
steam or otherwise to 130° or 140° C., and maintained for a few minutes. The
supply of heat is then shut off, and the vapour being blown off from the vessel till
the pressure is reduced to that of the atmosphere, the treated material is removed.
By any of these methods of treating the cellulose it is obtained in a brittle or
disintegrated condition. It is then washed to remove acid, and then by means of
a filter press or otherwise it is brought to the condition of having about 50 per cent.
moisture.
The mass is then treated in an edge runner with a solution of caustic soda in such
proportions as to give a product which is alkali-cellulose, containing from 40
to 50 per cent. cellulose, 10 to 12 per cent. alkali NaOH, and 50 to 38 per cent.
water.
This product is in a pulverulent condition favourable for treatment with carbon
disulphide for the preparation of sulphocarbonate.
Although by the acid treatment the cellulose is inade to undergo molecular
changes, the product retains the essential characteristics of normal cellulose, and
the sulpho carbonato obtained from it has properties which cannot be distinguished
from that obtained from cellulose in its original fibrous condition.
The treatment, however, ought to be kopt within limits such as those above

page_text: prescribed, otherwise the resulting sulpho carbonates may have properties which
limit their utility.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I would have it understood
that I make no general claim to the disintegration of cellulose by treatment with
acid, but what I claim is :-
The manufacture of an alkali-cellulose approximately of the composition
CH,,O,NaOH from cellulose previously treated with acid substantially as
described.
ABEL & IMRAY,
Agents for the Applicant.