Improvements relating to the Manufacture of Nitro-substitution Compounds of Cellulose.
Year: 1891

page_text: Date of Application, 7th Mar. 1891
Complete Specification Left, 7th Dec., 1891-Accepted, 6th Feb., 1892
PROVISIONAL SPECIFICATION.
Improvements relating to the Manufacture of Nitro-substitution
Compounds of Cellulose.
I, HUDSON MAXIM, Chemist, at present residing at Stonyhurst, Crayford, in
the County of Kent, do hereby declare the nature of this invention to be as
follows:
My invention relates to the manufacture of nitro-substitution compounds of
cellulose, such as pyroxylin or gun-cotton, and is chiefly designed to provide in a
more simple and efficient manner than heretofore for the production of tri-nitro-
cellulose.
According to the methods of manufacture heretofore employed, the cellulose has
been first immersed in a bath containing a large excess of a mixture of highly
concentrated nitric and sulphuric acids. After remaining in this bath for about
five or six minutes, the partially converted cellulose is taken out and put into
earthen pots, each holding, say, about 14 lbs. of cellulose, and containing about
14 lbs. of the nixed acids from the immersion bath, or about 11 lbs. of acids for
each pound of cellulose. The cellulose is allowed to remain in the earthen pots for,
say, twenty-four hours, to digest or finish the process of nitration. As the re-action
going on generates heat, and, as the quantity of acids is small, not being enough to
fully cover the cellulose, the pots are placed in a vat of cold water and the water
is made to circulate about them, to prevent fuming off of the contents.
twenty-four hours, the converted cellulose is placed in a centrifugal machine to
remove the excess of acids, and the remainder of the acids is removed by copious
washings and boilings with water.
After about
The quantity of the acids consumed per lb. of cellulose is, therefore, about 11 lbs.
of the mixed acids, which are usually mixed in the proportions of one part of nitric
acid to three parts of sulphuric acid, this quantity being supplied to the immersion
bath for each lb. of cellulose dipped in it, for the purpose of replacing the acids
carried in the cellulose and removed therewith to the above mentioned digest pots.
The object of my invention is to produce pyroxylin of various degrees of
nitration, such as di-nitro-cellulose and tri-nitro-cellulose, but more especially
the highest nitrated compound, that is to say, tri-nitro-cellulose or gun-cotion
proper with the consumption or expenditure of a less quantity of acids than has
been heretofore required, and consequently at a correspondingly lower cost per lb.
for the gun-cotton produced, and at a saving of labour.
In carrying my said invention into practice, I prefer to employ two immersion
baths of the mixed acids, each bath being of different strength and the proportions
of the nitric and sulphuric acids being slightly different in each bath.
Each bath should contain from 50 to 100 times as much of the mixed acids
as of the cellulose to be immersed therein. The cellulose is dipped in the first
bath in much the same manner as has been practiced heretofore,-namely, for
about 5 or 6 minutes, during which time the cellulose has become thoroughly
saturated with the acids and about from one-half to two-thirds of the conversion
of the cellulose into gun-cotton or tri-nitro-cellulose has taken place. The
cellulose is then removed from the first bath and all but from 7 to 9 lbs. of the
acids, or thereabouts, is removed or squeezed out of it, and these acids thus
removed are allowed to run back into the first bath.
The partially converted cellulose thus removed from the first bath, is then placed
in the second and last bath, which term the digest bath, where it is allowed to
remain from 16 to 48 hours to become thoroughly converted into tri-nitro-
cellulose.

page_text: The strength of acids employed for the first bath are the strongest obtainable in
commerce, riz.: nitric acid, 152, specific gravity, and sulphuric acid of
1.84 speci ic gravity. After the immersion of the cellulose in the first bath, the
acids become slightly diluted with water evolved by the action of the acids upon
the cellulose. The acids in the first bath, which at first should be about 1 part
nitric acid, to 3 parts sulphuric acid become slightly altered in their relative
proportions, part of the nitric acid being taken up in the conversion of the cellulose
into nitro-cellulose, I therefore add to this bath, after the removal of the cellulose
therefrom, a quantity of the strongest mixed acids in the above proportions, or
thereabouts, viz.: 1 part nitric acid to 3 parts sulphuric acid, to restore, or partially
restore, the somewhat weakened acids.
A great advantage of my said invention is that in the last or digest bath a large
excess of acids is employed, therefore, the cellulose material is fully immersed and
flooded with the acids so as to preclude any possibility of fuming off from the heat
evolved from the reaction which, at this stage of the process, is yet necessary to
complete the nitration.
By the potting out method, hereinbefore described, which has heretofore been
practiced, it has been found necessary to employ, or to allow to remain in the
cellulose material, from 10 to 12 lbs. of acid, usually about 11 lbs. of acid for
each pound of cellulose in order that the cellulose material shall be sufficiently
Whereas
saturated with the acids to complete or finish the process of nitration.
As the
by my process herein described, in consequence of employing a large excess of
acids in a large digest bath, in which all the cellulose material of a day's batch
may be immersed, I am enabled to complete the conversion of the nitro-cellulose
taken from bath 1, into tri-nitro-cellulose in the said digest bath with a less
expenditure of acids, that is, with a less quantity of acids added to the first bath,
and a less quantity removed from the said bath in the cellulose material.
cellulose material is about one-half to two-thirds converted in the first bath, and as
only one-half to one-third more conversion is possible in the second bath, there is
no extra expenditure or consumption of the acids in consequence of employing a
large excess thereof. After the cellulose has become fully converted into tri-nitro-
cellulose in the digest bath, it is removed and the excess of acids squeezed out, or
extracted with a centrifugal machine in the usual way, after which it is washed,
boiled, treated and dried in the usual way. The acids extracted from the nitro-
cellulose are allowed to return to bath No. 2, but after all of the gun-cotton has
been taken out of bath No. 2 a quantity of the weakened acids sufficient to make
room for those which come over and into it with the cellulose material from the
first bath in a day's batch, is removed.
The acids which are carried along with the cellulose material, from the first to
the second bath, as herein before described, will be of the strength and character of
the acids of the first bath, or practically so, and will tend to restore the strength
of the acids of the second bath. After the completion of the conversion of the
cellulose material into gun-cotton in the second bath, the acids therein will become
altered one-third to one-half more in strength and in the proportions of the nitric
to the sulphuric acid, than the acids of the first bath, in consequence of the con-
version of the partially converted cellulose brought from the first bath into
tri-nitro-cellulose in the second bath.
By employing a large digest bath, or a digest bath with a large excess of acids,
as I do, much saving of labour is effected, and the temperature of the digest bath
can be controlled with great accuracy, and a more uniformly nitrated product
obtained. Whereas by the potting out method, hereinbefore mentioned, the
cellulose material not being fully immersed, or covered by the acids, and there
being a large number of small pots, the temperature of these various pots, cannot
well be regulated with uniformity, consequently the conversion takes place at a
different temperature in some of them than in others, and a lower nitrated product
is frequently obtained, in some of the pots, and the contents of some of the pots
often becomes heated so much as to fume off.

page_text: I am aware that heretofore gun-cotton has been manufactured by the employ-
ment of two baths, or more, one for the first immersion, and one for a second
immersion, and wherein the cellulose material has been allowed to remain to finish
its conversion into gun-cotton, but in each case the strength of acids in the second
bath has been equal to, or greater, than the strength of the acids of the first
immersion bath, the object having been to partially convert the cellulose in the
first bath, and to finish the nitration in a second and stronger bath, the only object
of a second bath being to attain a higher and more thorough degree of nitration by
immersion in a second bath of the strongest acids, after an immersion in a
preliminary bath wherein and whereby the strength of acids have become somewhat
weakened.
When a digest bath, as above described, is employed, a great loss of acids, or
a loss of acids of great strength, is had in what is removed in the gun-cotton;
whereas by my process, the acids which are removed from the second bath after
the conversion therein of the cellulose material into tri-nitro-cellulose, are of a
minimum strength compatible with the manufacture of a tri-nitrate, the acids being
renewed and restored therein again to working strength as herein before described,
by the acids which are brought into it in the cellulose material from the
first bath.
I have herein described my process as employing two baths only, one an
immersion bath, the other a digest bath, but of course two or three or more first
immersion baths might be employed together with one large digest bath to receive
the partially converted cellulose after it has been immersed in the said first baths,
and all to attain the same result hereinbefore described. Also, of course, two or
more digest baths might be employed to attain the same end, so long as the digest
bath, or the digest baths employed, contain an acid mixture of the character herein-
before specified for my second bath, as compared with the herein-described first
immersion bath of my process, and so long as the acids in the second or digest bath,
or baths, shall be in large excess sufficient to thoroughly immerse and cover the
cellulose material to be placed therein.
In the production of di-nitro-cellulose or pyroxylin of the lower grades of
nitration by my process, I employ suitable proportions of weaker acids in the baths
above mentioned.
Dated this 7th day of March 1891
HUDSON MAXIM.
COMPLETE SPECIFICATION.
Improvements relating to the Manufacture of Nitro-substitution
Compounds of Cellulose.
I, HUDSON MAXIM, of No. 57 West 24th Street in the City, County and State
of New York, United States of America, formerly temporarily residing at
Stonyhurst, Crayford, in the County of Kent, England, 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:-
My invention relates to the manufacture of nitro-substitution compounds of
cellulose, such as pyroxylin or gun-cotton and is chiefly designed to provide in
a more simple and efficient manner than heretofore for the production of tri-nitro-
cellulose
According to the methods of manufacture heretofore employed, the cellulose has
been first immersed in a bath containing a large excess of a mixture of highly
concentrated nitric and sulphuric acids. After remaining in this bath for about
five or six minutes, the partially converted cellulose is taken out and put into
earthern pots, each holding, say, about, 1 lbs., of cellulose, and containing about
14 lbs, of the mixed acids from the immersion bath, or about 11 lbs. of acids for

page_text: As the
each pound of cellulose. The cellulose is allowed to remain in the earthern pots
for, say, twenty-four hours, to digest or finish the process of nitration.
re-action going on generates heat, and, as the quantity of acids is small, in most
factories not being enough to fully cover the cellulose, the pots are placed in a rat
of cold water, and the water is made to circulate about them, to prevent fuming off
of the contents. After about twenty-four hours, the converted cellulose is placed
in a centrifugal machine to remove the excess of acids, and the remainder of the
acids is removed by copious washings and boilings with water.
The quantity of the acids consumed per lb. of cellulose is, therefore, about
11 lbs. of the mixed acids, which are usually mixed in the proportion of one part
of nitric acid to three parts of sulphuric acid, this quantity being supplied to the
immersion bath for each lb. of cellulose dipped in it, for the purpose of replacing
the acids carried in the cellulose and removed therewith to the above mentioned
digest pots.
The object of my invention is to produce pyroxylin of various degrees of
nitration, such as di-nitro-cellulose and tri-nitro-cellulose, but more especially the
highest nitrated compound, that is to say, tri-nitro-cellulose or gun-cotton proper
with the consumption or expenditure of a less quantity of acids than has been
heretofore required, and consequently at a correspondingly lower cost per lb. for
the gun-cotton produced, at a saving of labor.
In carrying my invention into practice, I prefer to employ two immersion baths
of the mixed acids, each.bath being of different strength and the proportions of the
nitric and sulphuric acids being slightly different in each bath.
Each bath should contain from 50 to 100 times as much of the mixed acids as of
the cellulose to be immersed therein. The cellulose is dipped in the first bath in
much the same manner as has been practiced heretofore namely, from about
5 to 6 minutes, during which time the cellulose has become thoroughly saturated
with the acids, and about, from one-half to two-thirds of the conversion of the
cellulose into the gun-cotton, or tri-nitro-cellulose has taken place. The cellulose
is then removed from the first bath and all but from 6 to 9 lbs. of the acids, to each
pound of cellulose, or thereabouts, is removed or squeezed out of it, and these acids
thus removed are allowed to run back into the first bath. The preferred method is
to pass the cellulose through a centrifugal machine between baths Nos. 1 and 2, to
remove the excess of acids. The partially converted cellulose thus removed from
the first bath, is then placed in the second and last bath, which I term the digest
bath, where it is allowed to remain from 16 to 48 hours to become thoroughly
converted into tri-nitro-cellulose.
The strength of the acids employed for the first bath are the strongest obtainable
in commerce, viz. nitric acid of 1.52, specific gravity, 1 part, and sulphuric acid
of 1-84, specific gravity, 3 parts. After the immersion of the cellulose in the first
bath, the acids become slightly diluted with water evolved by the action of the
acids upon the cellulose. The acids in the first bath, which at first should be about
1 part nitric acid, to 3 parts sulphuric acid become slightly altered in their relative
proportions, part of the nitric acid being taken up in the conversion of the cellulose
into the nitro-cellulose; I therefore add to this bath, after the removal of the
cellulose therefrom, a quantity of the strongest mixed acids in the above proportions,
or thereabouts, v.: 1 part nitric acid to 3 parts sulphuric acid, to restore, or
partially restore, the somewhat weakened acids.
A great advantage of my invention is that in the last or digest bath a large
excess of acids is employed, therefore, the cellulose material is fully immersed and
flooded with the acids so as to preclude any possibility of fuming off from the heat
evolved from the reaction which, at this stage of the process, is yet necessary to
complete the nitration.
By the potting out method, herein before described, which has heretofore been
practiced, it has been found necessary to employ, or to allow to remain in the
cellulose material, from 10 to 12 lbs. (usually about 11 lbs.) of acids for each
pound of cellulose, in order that the cellulose material shall be sufficiently saturated

page_text: with the acids to complete or finish the process of nitration.
Whereas by my
process herein described, in consequence of employing a large excess of acids in a
large digest bath, in which all the cellulose material of a day's batch may be
immersed, I am enabled to complete the conversion of the nitro-cellulose taken
from bath No. 1, into tri-nitro-cellulose in the digest bath, with a less expenditure
of the acids, that is, with a less quantity of acids added to the first bath, and a less
quantity removed from the said bath in the cellulose material. As the cellulose
material is about one-half to two-thirds converted in the first bath, and as only
one-half to one-third more conversion is possible in the second bath, there is no
extra expenditure or consumption of the acids in consequence of employing a large
excess thereof. After the cellulose has become fully converted into tri-nitro-
cellulose in the digest bith, it is removed and the excess of acids squeezed out, or
extracted with a centrifugal machine in the usual way, after which it is washed,
boiled, treated and dried in the usual way. The acids extracted from the nitro-
cellulose are allowed to return to bath No. 2 but after all of the gun-cotton has
been taken out of bath No. 2, a quantity of the weakened acids, is removed from
bath No. 2, sufficient to make room for those which come over and into it with
the cellulose material from the first bath, in a day's batch.
The acids which are carried along with the cellulose material, from the first
to the second bath, as hereinbefore described, will be of the strength and character
of the acids of the first bath, or practically so, and will tend to restore the
strength of the acids of the second bath. After the completion of the conversion
of the cellulose material into gun-cotton in the second bath, the acids therein will
become altered in strength and in the proportion of the nitric to the sulphuric acid,
from the acids of the first bath, in consequence of the conversion of the partially
converted cellulose brought from the first bath into tri-nitro-cellulose in the second
bath, which is accomplished by the absorption of the nitric acid by the cellulose,
and the production of water which is taken up by the sulphuric acid.
By employing a large digest bath, or a digest bath with a large excess of acids,
as I do, much saving of labour is effected, and the temperature of the digest bath
can be controlled with great accuracy, and a more uniformly nitrated product
obtained. Whereas by the "potting out" method, hereinbefore mentioned, the
cellulose material not being fully immersed, or covered by the acids, and there being
a large number of small pots, the temperature of these various pots cannot well be
regulated with uniformity, consequently the conversion takes place at a different
temperature in some of them than others, and a lower nitrated product is frequently
obtained, in some of the pots, and the contents of some of the pots become heated
so much as to fume off.
I am aware that heretofore gun-cotton had been manufactured by the employment
of two baths, or more, one for the first immersion, and one for a second immersion,
and wherein the cellulose material has been allowed to remain to finish its con-
version into gun-cotton, but in such case, the strength of acids in the second bath
has been equal to, or greater, than the strength of the acids of the first immersion
bath, the object having been to partially convert the cellulose in the first bath, the
only object of a second bath being to attain a higher and more thorough degree of
nitration by immersion in a second bath of the strongest acids, after an immersion
in a preliminary bath, wherein, and whereby, the strength of acids has become
somewhat weakened.
When a digest bath as above described, has been employed, a great loss of acids,
or a loss of acids of great strength, has resulted; whereas, by my process, the
acids which are removed from the second bath after the conversion therein of the
cellulose material into tri-nitro-cellulose, are of a minimum strength compatible
with the manufacture of a tri-nitrate, the acids being renewed and restored therein
again to working strength, as herein before described, by the acids which are brought
into it in the cellulose material from the first bath.
I have herein described my process as employing two baths only, one an
immersion bath, the other a digest bath, but of course two or more first immersion

page_text: baths might be employed together with one large digest bath to receive the partially
converted cellulose after it has been immersed in the said first baths, and all to
attain the same result hereinbefore described. Also, of course, two or more digest
baths might be employed to attain the same end, so long as the digest bath or the
digest baths employed, contain an acid mixture of the character hereinbefore
specified for my second bath, as compared with the herein-described first immersion
bath of my process, and so long as the acids in the second or digest bath, or baths,
shall be in large excess sufficient to thoroughly immerse and cover the cellulose
material to be placed therein.
While I have termed the acids mixture of the second bath a weaker acids bath,
it must be understood that it is still a very strong mixture, probably about
one per cent. weaker than the strongest acids bath. By reason of the great excess
of quantity and by addition of the strong acids contained in each batch of nitro-
cellulose added to the second bath, the acids mixture contained in said bath remains
of uniform character, and the product has a uniformity not obtainable by the
"potting out" method.
In the production of di-nitro-cellulose or pyroxylin of the lower grades of
nitration by my process, I employ suitable proportions of weaker acids in the baths
above mentioned.
It is obvious that one large bath might be employed, containing a large excess of
acids over the weight of the cellulose to be immersed therein, the cellulose being
allowed to remain in said bath until thoroughly converted. The advantages of
mine over such a method is chiefly that I am enabled to secure most of the con-
version of the cellulose in the first bath where small quantities of the material may
be handled, as in the usual manner, thus avoiding danger from heating of large
masses of the material. These small quantities being then placed together in one
large bath where the material being already nearly converted, all danger of fuming
off is avoided. Furthermore, the strength of the acids in my first bath being
greater than that of the second, the acids penetrate more readily the fibres of the
cellulose when immersed therein, which is a factor of considerable importance in
obtaining a product of a uniform nitration, with a minimum expenditure of acids.
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-
1. The method herein described of producing nitro-cellulose or pyroxylin of a
high grade, which consists in immersing the cellulose for a short time in a bath of
strong acids mixture, then conveying said cellulose with contained acids (amounting
to say, 6 or more times the weight of cellulose) to a second bath containing many
times the weight of the cellulose of a weaker acids mixture, and there completing
the conversion by digesting for a considerable time, substantially as described.
2. The process of manufacturing pyroxylin of a high degree of nitration which
consists in immersing the material to be nitrated successively in two baths each
containing a large excess of mixed nitric and sulphuric acids, in the first and
stronger bath of which the cellulose is placed until partially converted or converted
into a lower nitro compound, and in the second or weaker of which baths the
completion of the conversion into a higher nitro-compound takes place, and the
acids mixture in the second of last bath being maintained at a suitable working
strength by the stronger acids of the first bath, adhering to the cellulose material.
Dated this 7th day of December 1891.
FELL & WILDING,
1, Queen Victoria Street, London, E.C., Agents for the Applicant.