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Патент USA US2404887

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«MV 3» §94-
R. E. REEVES Erm.,
' ,
Filed May 5, 1944 `
4.0 -î
STAEILITY (immun-:5)
3&3 .
Patented July 30, 1946
Richard E. Reeves and Joel E. Giddens, New O_r- _l
leans, La., assignors to United States of Amer
ica as represented by Claude R. Wickard, Sec
retary of Agriculture, and his successors in» of-`
Application May 5, 1944, serial No. 534,370.
2 claims. (01260-223)
(Granted under the act of March 3, 1883, as l.
amended April 30, 1928; 370 0. G. 757)
~ This application is made under the act of March
3, 1883, as amended by the act of April 30, 1928,
and the invention herein described, if patented,
may be manufactured and used by or `for the
Government of the United States of America for
governmental purposes without the payment to
us of any royalty thereon.
This invention relates to nitrated cellulose, and
has for its primary objects an improvement in
the process “of stabilizing such cellulose, and such
other objects as will be apparent in considera
tion of the following specification:
Due to the use of sulfuric acid in the prepara
tion of nitrocellulose, it is ordinarily necessary
to remove the retained sulfate to stabilize the
product. This is conventionally accomplished by
repeated boiling in water and beating treatments,
a long and tedious process. It is also known that
addition of a little ammonia to the boiling water
aids in stabilization. However, in this event it
is necessary to control the amount. of ammonia
added very closely, as the addition of , ammonia
little beyond slight alkalinity deleteriously affects
2 o
’ linters, and is also effective with nitrocellulose
derived fromwood pulp.
The process is more specifically exhibited "nf,
following examples:EXAMPLEI
~_ ,
Cotton fibers, cut to about 0.15 inch and> purif‘,
ñed to meet the specifications for linters to be',
used in the productionf-of‘fpyro’.’ nitrocellulose'
by the Naval Powder Factory, were dried over@v
night at 105° C. A `32 g.- portion oftheldried»
iiber was stirred in a solutionconsisting of,v 231i> g.,
of H2O, '866 g. 0fA H2SO4, andÍ 494 g. QÉHNOS, all“
chemicals used beingvof C_rlP. or reagent grade.
The mixture wask maintained at _40° C. for _2Q
minutes,v immediately after which the formed
nitrocellulose was ñltered and drowned in cold
tap water, It was then washed with 1l) changes
of water, and was boiled f_or 4 hours underreñux
_and dried, giving a lot having a nitrogen cont
The boiled nitrocelluloseas. above, obtained.
was divided in four parts, one vof which was rinsed
and dried and kept as a controlsample. The
the nitrocellulose.
According to this invention, ammonia isA used at 25 other threek parts were separately stirred. for.¿.1-_5_
minutes, each with 50 parts o_f ammonium hy@
a lower temperature, preferably room tempera
droxide solution containing 0.05%, »0.20% and
ture, as one treatment, in which event the alka~
1.00% of ammonia, respectively, at roomtempera-Ä
linity need not be so carefully controlled.` Also.4
tures„to obtain three separate stabilized samples'.v
ammonium salts may be used instead of the
hydroxide, andif the treating solution is buffered
to remain slightly acidic, excess salt can be used
with a hot solution with no deleterious eiîect on
the nitrocellulose, and thus be introduced in con~
nection with a boiling treatment as claimed in
copending application, Serial No. 670,086, filed
May 16, 1946.
. Preferably, the ammonia treatment is combined
with at least a‘prior boil, and boiling and beat
ing treatments may be advantageously employed
subsequent to the boil but prior to the ammonia
Room temperatures are most satisfactory for
the ammonia treatment because of convenience,
althoughhigher and lower temperatures are effec
tive. _In general; it may be said, however, that
the higher the temperature the more closely the
alkalinity must be controlled.
The` process has been carried out principally
using cut cotton as the cellulosic raw material, but
The excess ammonium hydroxide was removed
Tests were run on these samples against-the
control sample using the known134.5° heat'test
(Military explosives, War Department TechnicaA
Manual 9~2900. August 29, 1940, DD. 66 andö'l),
and also using a `second procedure'hereinafter
designated as the ‘_‘110° test.” This second _pre-_'
cedure was developed especially to handle small
samples with safety and reproducibility, and is
illustrated by the apparatusïshown in Figure 1
of the drawing. In thisapparatus, -.a.„suitable
quantity (0.5 g. with _an apparatus having dimens
sions as shown in the drawing) ofthe sample to
be tested is placed in a U-tubeläl immersed -inïa
tricresyl phosphate bath fl! maintained at
110°i0.55’ C. 'The U-tube IB isstoppered at its`
upper ends, and has one of its legs connected by
a tube l2 to one leg of a second U-tube I3.
indicator consisting of l ml. of an aqueous solu-ï
has been found’to be equally effective with cotton 50 tion of 0.5% potassium iodate,__1.0% potassium
iodide, and 3 drops of a 2% starch solution is
ing treatment, the other part being stirred for
placed in the second U-tube I3. This U-tube
15 minutes at room temperature in 1%V aqueous
is also stoppered at its upper ends, and its other
ammonia following the boiling and beating treat
leg is connected through a tube I4 to a suitable
ments, rinsed and dried.
suction device (not shown). Outside air is drawn CY
In the boiling and beating treatment, the water
from a tube I5 at the rate of 30 ml. per minute
was changed at the end of 4, 16, 28, 40, 50, 63 and
through sulfuric acid in flask I6, thence through
70 hours.
soda line in bulb I'I, thence passing through
Test results on the removed samples are given
U-tube IIL sweeping through the sample therein,
in the following table, the asterisks in the table
and thence passing through tube I3, bubbling
indicating that the samples were too unstable to
through the indicator therein. The air sweeps
be tested by the procedure employed, and the
the volatile decomposition products from the
:blanks indicating that no test was conducted in
sample, the end of the test being determined when`
the particular instances.
blue coloration develops in the` indicator. The
Table Z
time required for this coloration to'occur is taken
as a measure of the stability of the sample tested_
With the 110° test, as above described, the sta
134.5° heat test
110° test
bility of highly unstable nitrocellulose samples
may be evaluated with comparative safety and
the reproducibility with such samples is excellent. 20
Boiling and beating
Control Atlëèä‘êxàla Control Aälelzïllt‘èrâm
Moisture control of the sample is not such a
critical factor as in the case of those tests which
keep evolved gases in contact- with the heated
sample, and therefore the 110° test may be used
None., _______________ __*_____
with air-dried samples.
The 110° test and the 134.5° heat test often
Boiled 4 hrs.
Boiled 14 hrs
vyield approximately the same times for a given
sample. In both tests samples showing times of
Boiled 2 hrs.
__________ __
26, 26
Boiled 2O hrs _.
good stability.
29, 18 '
25, 25
__________ __
5, 5
27, 31
Boiled 30 hrs ........................... „_-_..
Boiled 40 hrs ....... __
15, 17
32, 37
8, 7
7, 7
32, 26
23, 17
27, 23
15, 23, 20
Boiled 40 hrs. and
beaten ___________ __
26, 24
less than 10 minutes may be classified as having
Boiled 50 hrs. (beaten
poor stability, those showing from 10 minutes to 30 at 40 hrs.) __________________ __
Boiled 63 hrs. and
25 minutes as having moderate stability, and
`those showing more than 25 minutes as having
4, 4
4, 5
4, 5
beaten (2d time)___
Boiled 70 hrs. (beaten
at 40 and 63 hrs.)_-_
23, 23
________ __
16, 22
27, 29
40, 40
32, 30
24, 24
24, 24
16, 14
23, 23
The following table indicates results of the tests
of the control and the three samples of Example I, 35
Comparison cf results given in the data of Ta
the several results indicated from each test of a
ble 2 shows that ammonia treatment produces a
sample being obtained by repeated tests on the
greater change in stability inthe earlier stage of
same sample.
Table 1
the boiling and beating treatments than in the Y
later stages. A product of high stability is ob
40 tained if ammonia is used with only 4 hours prior
134:.5‘x heat
110° test
test, minutes
y minutes
boil, whereas without the use of ammonia a 40
hour .boil is required to give a corresponding de
gree of stability.
3, 4
0.05% NH3
0.20% NH
Control. _ __-
32, 29
30, 30
80, 52. 64
40, 69,35
1.00% NHL.“
37, 35
102,100, 72, 60
In order to- determine whether the stabilizing
effect of' the ammonia treatment isdue to the
y alkality of the ammonia, experiments were con
ducted on similar samples of freshly prepared
nitrocellulose using dilute aqueous solutions of
other basic` substances such as lithium carbonate,
’sodium ' hydroxide, methylamine, etholamine,
pyridine, and urea. The stabilizing eifects of
these were nil. Apparently, therefore, the stabi
lizing action of ammonia is not due to its alka
linity, or at least due to this alone, but involves
other properties.
As illustrated by the following example, im
provement in stability is obtained by combining
the ammonia treatment with a variety of boiling
and beating treatments.
A 64 g. batch of cut cotton was nitrated in a
manner similar to that employed in Example I,
giving a lot having a nitrogen content of 12.66%.
All boiling and beating treatments were made
in distilled water and with a Waring blender.
At various `stages of the boiling, with or without
beating, Samples were removed and each removed
sample was divided into two‘parts. One part was
rinsed and dried and used as the control to indi
cate stability derived from the boiling and beat.
‘ In the examples given above, the ammonia
treatment was eifected by using dilute aqueous
ammonium hydroxide as the stabilizing agent.
However, other ammonium agents, such as am
monium sulfate, may be used. For- example,
freshly prepared nitrocellulose may be boiled with
a slightly acid solution containing ammonium
salts buffered to remain at a pI-I higher than 3.5,
preferably higher than 4, with excellent stabiliz
ing results.
In this case, the concentration of
ammonium salts in the solution may be as low
as 0.10%, calculated as ammonium sulfate. The
buffering agent may be any which will give a
satisfactory buffering action in the faintly acid
region. Sodium acetate', potassium acid phthal
60 ate, and sodium citrate have been found satisfac
tory. One hour lboiling in such a solution gives
a nitrocellulose of excellent stability.
Cut cotton fibers were used in the preceding
examples. The treatment with cotton linters
65 gives similar stabilization results, as illustrated
in the following example:
A batch of nitrocellulose prepared from cot
ton linters and having a nitrogen content of
12.73% was divided into two parts. One part
was boiled for 4 hours without ammonia treat
mentV and the other was placed in water, adjusted
to slight alkalinity with ammonium hydroxide,
and stirred for 1 hour at room temperature.
2,404,887 ,
nitrocellulose, essentially the same procedure of
Test results on the two parts are shown in Ta
extraction may be followed as in analysis for the
bleu 3.
sulfate. In this case, it is better to use the 0.01`
normal I-ICl solution for the boiling. The re
moved ammonia may then be determined by use
of Nessler’s reagent (see formula of Bock and
Table 3
110° test
Benedict, as given by Hawk and Bergeim, Prac
stiriedihburin dilute NH, .........
so, so
tical Physiological Chemistry (1937),` 111th ed.,
Blakiston, Philadelphia, Pennsylvania, p. 928) and
10 the blank and test samples compared with the
.Coleman spectrophotometer at 425 mu, the quan-V
As before stated, the action of the ammonia is
Boiled 4 hours, no NH; ______________________________ . _
3, 3
not due alone to its alkalinity, as has been amply
tity of ammonia being read from a standard curve
demonstrated by substitution of other bases.
vAlthough the true action is not definitely known,
established with known solutions of ammonium
i .
By using the 0.01 normal HC1 solution for boil
it may be stated that it is probably due to an 15
ing, both the sulfate and ammonia determina-1
ability of the ammonia to penetrate the structure
tions may be made simultaneously on the same
of the nitrocellulose fiber and neutralize thesul
fate bound within the ñfber structure or within
In analysis for the ammonia according to the
the molecules themselves. Experiments relative
to sulfate contents and consumed ammonia con 20 above-outlined procedure, ithas been found thaty
repeated boiling with changes of solution does
tent tend to exhibit this. Such experiments also
not show the amount of ammonia removed in
indicate the consumption of ammonia in the
successive extracts to approach zero, as would
process and optimum conditions relative to other
be expected. Rather, the readings approach a
factors, and they give an indication of the nature
of the sulfate association with the nitrocellulose v25 minimum of approximately 0.03 mg. NH3- per g.
of nitrocellulose. This minimum is usually
reached after four boiling treatments.
Quantitative analyses of sulfate and ammonia
Testing the analysis on 70 treatments with‘boil
in nitrocellulose present numerous difficulties.
ing and beating, using many samples of nitrocellu
The amounts of sulfate to be determined lie be
tween 0.1 mg. and 8.0 mg. S04 per g. of nitro 30 lose which had not been exposed to an ammonia
treatment and were presumably free from ammo
cellulose, .and the ammonia contents vary be
nia, showed an average of 0.034 mg. NH3 (or at
tween 0.03 mg. and 2.0 mg. NI-Ls per g. The anal
least a substance which reacted with Nessler’s re
yses which involve the destruction of the nitro
agent), per g. of nitrocellulose.` Therefore, it has
cellulose by chemical digestion are not trust
worthy under these conditions, as they introduce 35 been concluded that the observed minimum of ap
proximately 0.03 mg. NH3 per g. of nitrocellu
complicating factors obscuring the desired results
lose is a systematic error in the procedure and
when dealing with such small percentages of sul
all values are adjusted by subtracting 0.034 from
fate and ammonia.
the observed value in each separate reading.
A substitute procedure involving mechanical
It has also been found that the vigorous beat-_
separation of the sulfate and ammonia was used, 40
therefore, in which comparatively large samples
ing given the nitrocellulose in the above-described
manner of mechanical separation of the sulfate,
are given repeated boiling in pure water or in a
quickly liberates the sulfate even from samples
dilute aqueous solution of HCl and beating treat
which had been subjected to long boiling, and
ments. In this manner, extracts are obtainedY
which contain a minimum of interfering decom- ~` that a short period of >locating (5 minutes) is
accompanied by an increase in stability of the
position products from the cellulose nitrate. By
' using suitably large samples and by concentrat
nitrocellulose, provided the nitrocellulose has al
ready been extensively boiled. However,> con
ing the extracts, it is possible to analyze for the
tinued beating introduces unstability. Therefore,
very small traces of sulfate and ammonia re
it appears that the beating results in two com
moved from the nitrocellulose which probably
peting factors: first, stabilizing due to separa
escape detection in the usual methods of analysis.
tion of the sulfate from the nitrocellulose, accom
The vigorous beating action desired in this
plished in a short period; and second, a harmful
method of analysis is well obtained by use of a `
effect probably due to some action of the beater
Waring blender.
on the nitrocellulose itself, introducing unsta
For analysis of the sulfate, 58 hours. boiling
bility in the longer periods of beating. For this
with eight changes of approximately 100 parts
reason, unless otherwise noted, all described beat
of distilled water or of a 0.01 normal HC1 so
ing periods are for 5 minutes.
lution of the sample per part, may be employed,
By using the extraction method of analysis for
followed by one beating. The severa1 filtered ex
tracts may then be combined for sulfate deter (il) the sulfate and by testing the nitrocellulose for
stability at various stages in the extracting proc
‘ mination or each may be investigated separately
ess, precise information on the effect of sulfate
and the amounts totaled for determination of the
on stability was obtained. As' representativaa
total sulfate content. Determination of the ex
20 g. sample of nitrocellulose (13.0% N) 4was
tracted sulfate is readily accomplished by the
boiled with changes of distilled water, beating
turbidimetric method of` Treon and Crutchfield
treatments being introduced at intervals, and the
(Ind. Eng. Chem., anal. (1942) ed. 14, p. 119)
several extracts were analyzed for S04, the proc
modiñed to allow for use of smaller volumes of
essbeing continued until a negligible amount ofA
solutions. With a 25 m1,'volume, ‘amounts of S04
SOiwas'removed in the >final' treatments.- By
between 011mg. and 2.0 mg. may be determined
computing the amount of 'sulfate removed in each
with considerable accuracy. Observations may
be made in a rColeman Model 11 spectrophotom
eter at a wave length of 540 mu and the values
read from a standard curve established with
known solutions of sulfuric acid.
In determining the ammonia content of the
extract per gram of sample and adding the re--
sults, the total sulfate content of the original
sample was obtained. Also, the sulfate content
of the sample at the beginning of any stage of
removal was similarly determined by adding'the,
_ 2,404,887
S04 .determinations of theextracts including that
lulose (12.82% N), treated only by rinsing, which
stage and those following. >Table 4 indicates the
was then stirred for 15 minutes in a 1% aqueous
ammonia solution and washed with distilled water
until the washings gave no test with Nessler’s re‘-`
results of lone such experiment.
,Tabfzç 4
5 agent. This sample had a stability of 45 minutes
1f t'i
, with the 110° test, as compared to2 minutes in
o aoîiliiî e
the absence of the ammonia treatment.. ,.Ten.v
grams of the ammonia-treated sample _was re,
muws i
f Treatment
Rinsednu-__________ __'_ ____ ,V
goileâï? ärs- ~
Bghâd Íôáîg
.L05 __________ __
ñltering on washed paper were made up to known
volume for determination of .sulfate andammo-V
nia contents. Toward the end of the boiling, .a
beating treatment was introduced. The amountsA
ggägä îâlrîíhlgîêz
eaten 10mm ““““““““““ "
Boiled ,7,1m ---------------- ~~
ägägg Èôhïrlës-
53 '
Boiled 1c 135111111111
12 l5 of sulfate'and ammonia removed fromthe sam
ple by the various extracts are indicated in Table ‘
5, all ammonia Values being adjusted by sub
traction of the 0,34 mg./g. to compensate for the
-olia """ "ëöïèò
Boiled 58 hrs. with 8 changes
ci water and beaten 5mm.“k
'peaiediy boiled with 25o m1. `ef aornermai HC1,
l0 and the extracts obtained from each boiling by
systematic error before described.
0.00 __________ _.
Table 6
The relationship of sulfate content and stability 1s morel easlly vlsualized by reference to
Boiling treatment
Ammonia' Sulfateœo)
removed, l
curve A shown in Figure 2 of the drawing, in 25
which the ordinate represents S04 content in
mg. per g. of nitrocellulose, and the abscissa rep-
1st extract (boiled 14 hrs.) ........... __
resents stability as determined by the 110° test
the curve indicating less stability after the 30-
4th extract (boiled2hrs.) ............ __
is introduced
point, due
the beatingbeyond
that point 30
Curve A dirigere 2 indicates that stability is
a function' of S04 content, provided other fac-
Total ------------------------- -.
tors, such as excessive beating, are not introduced
which tend to alter the stability.
The data of Table 6 show that as` regards the
If ammonia treatment is given, the Stability
sample tested, 1.4 mg. of ammonia is suñicient to
results are entirely different, as indicated in Tastabilize l g. of freshly prepared nitrocellulose
ble 5 showing tests on a number of samples of
containing 6.43 mg. of sulfate. This gives aratio
nitrocellulose having dilïerent S04 contents, and
of mols of NH3 to Inols of S04 oi' 1.20.
treated for l5 minutes at room temperature with 40
A number of other‘experiments similar to thel
a'1% ammonia solution.
one described next above were carried out with
Table 5
other samples, some without and some with the
boiling treatment, the results of which are shown
SO C011tent 1%treatment
V Pmwustreatmentufsamples
es ’mm es
mused free ofaeids
Boiled 30 min-..
, 28
Boiled 2 hrs_,_
25, 25
ller: _ _ _ _ _ _
e , an
firtsä lirlieinesbeiëigeingthecorrespon
total linging
e o i er
. Digg/21,65’ ìtaëüity 1ì0° à” lines for the other samples, a column for the
_ s
_ _ _ _ _ _ _ _ __
Table 7
35,45 5()
ratio of meis ei NH3 te mois di S04 being added.
The results of Table 5 are visually represented
Treatment pil'leceding stabiliza-
“m W“ 1% mmm
Rinsed (from Table 6).
in curve B of Figure 2. This curve shows that 55 äfilïse‘äìáógñfjï‘m*
good stability is achieved by the use of the am-
B0i1ed2hrs ___________ __ _____ __
Mol NH.;
tig/4g); . M015@
momia treatment with nitrocellulose containing as
high as 3.2 mg. S04 per g. of nitrocellulose. As
the S04 content approaches zero, curves A and
The data of Table ’l show toc wide a variation
to rbe taken as establishing an exact vrelationship
B tend to meet, indicating that the effect of the 00 between the ammonia consumed in the treatment
ammonia treatment ls to oiïset the unstability due
and the sulfate present in the sample.` However,
to presence~ of the S04. Also, apparently the arnin the tests for determination of ammoniaQthe
monia treatment has no elîect on other factors
ammonia content in the sample will include not
only that consumed in neutralizing the unstabili
, Again, it is mentioned that the stability ob- U5 zation dueto the S04, but probably in addition -a
tained by the ammonia treatment is not due, sole. ly atleast, to its alkalinity, since tests with other
_ portions of the same samples used in obtaining
the data for Table 5, but substituting a sodium
hydroxide treatment for the
small amount bound' by the nitrocellulose within
the über structure, held by liquid retained on the
treated über, o_r both. It is‘probable, therefore,
that the ratios are higher than the ratios required
ammonia 70 for neutralization of the S04 itself.
treatment, gave no noticeable increasein stability
over the samples not so treated;
The marmer `by which ammonia brings about
stabilization of nitrocellulose is indicated in the
following experiment using a sample of nitrocel- 25
If the sulfate is present in the nitrocellulose
über as half-ester represented by R-S04H as has
been suggested, l mol of NH3 would combine With
l mol of S04. If, however, the sulfate is.l present'
as free acid, as has been suggested'also, 2 molspf
NH3 Would combine with 1 mol of S04. There
process is attended with little work and. is accom
fore, the data above favor the half-ester sugges
plished in a short time, it may be seen that the
invention involves a very simple and inexpensive
In another experiment, freshly prepared nitro
manner of treatment.
cellulose (12.6% N) was treated with ammonia, 5
The above examples and experiments were all
rinsed and dried, giving a resulting stability with
conducted with laboratory-prepared samples and
the 110° test of 18 minutes. Three grams of the
equipment. In the following example, the nitro
stabilized material was then stirred for 10 min
cellulose sample was from a batch being prepared
utes with 75 ml. of 5 normal HCl, rinsed free from
for `making pyro powder.
Cl ions, and dried, resulting in a nitrocellulose re 10
duced in stability to 5 minutes, which could not
be improved by further rinsing. However, upon
1.5 pounds of nitrocellulose were taken from a
a retreatment with ammonia, good stability again
boiling tub following two 4-hour periods of boil
ing with changes of water. The sample was
The evidence at hand as shown by the fore 15 beaten in a laboratory beater to ñneness approxi
going experiments indicates that the ammonia
mating that of ñnished pyro. It was next boiled
treatment oiîsets the harmful eifect of the sul«
for four hours and allowed to settle. The water
furic acid bound within the structure or fiber of
was decanted, replaced with cold water to which
the nitrocellulose, and that other bases, at least
was added aqueous ammonia containing NH3
the many tried, are unable to accomplish this re 20 amounting to 1 percent of the weight of the ni
sult, possibly because of inability to penetrate to
trocellulose. The suspension was stirred at room
the position where the sulfate is iixed.
temperature for 1 hour, allowed- to settle, and
It may be noted from the experiments that a
washed by decantation with eight changes of
very small amount of ammonia actually is in
water. The product gave stability of 29 minutes
volved in the stabilization of the nitrocellulose, 25 by the 134.5° German test and 37 minutes by the
1.40 mg. of NH3 per g. of nitrocellulose being in
65.5° starch-potassium iodide test (this test is
dicated in Table 6. It has been shown that with
a standard procedure described in War Depart
nitrocellulose which has been boiled for 4 hours
ment Technical Manual 'I‘M 9-29900). Similar
and beaten, less than 0.1 mg. per g. is required.
stable products were produced with 6.5 to 15
These amounts are almost negligible.
30 hours of boiling.
In actual production of the stabilized nitro
It is desirable that a certain amount of boil
cellulose, the ammonia consumption would in
ing follow the beating treatment. The beater inv
clude also the small amount bound by the nitro
this example was a. small paper mill type beater.
cellulose and any lost by the liquid retained on
Excellent stability was also produced when am
the ñber when draining the treating solution 35 monia was introduced into the solution during
from the nitrocellulose. The liquid loss involved
in this latter amount, without taking special
precautions for recovery, may be roughly ten
times the weight of the nitrocellulose ñber
the beating operation. This has the advantage
of reducing acidity and hence reducing the cor
rosion of the beater as Well as produing good
treated. Thiswould involve a loss of 5 pounds 40
Having thus described the invention, what is
of ammonia per 1,000 pounds of nitrocellulose
claimed is:
on the basis of employment of a 0.05% ammonia
1. A process comprising stirring nitrocellulose
solution. Under these conditions, the total loss
in an aqueous solution containing ammonia- at
of ammonia would approximate 0.64% of the
room temperature for a time not to exceed about
weight of the fiber treated, and this could be con 45 l hour, thereby to stabilize the nitrocellulose.
siderably decreased by pressing or centrifuging
2. A process comprising stirring nitrocellulose
the treated fiber to recover the retained liquid
with weak ammonium hydroxide at room tem
or by recovery of the ammonia from the water
perature for a time not to exceed aboutl 1 hour,
used in washing the retained liquid from the ñber.
thereby to stabilize the nitrocellulose.
Since the ammonia solution drained ou' the 50
batch of treated nitrocellulose may be reused, if
desired, in treating other batches, and since the
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