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Патент USA US2112989

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April s, 1938.
‘J. HELLEEr AL
-
'
2,112,989
PROCESS FOR THE NITRATION OF STARCH
Fivled Nov. 10, 19:56
V
)Mvnimes
94, H 7%
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M22114“ A T Tp/VA/E Y
2,112,989‘
Patented. Apr. 5, 71938
UNITED STATES‘2,112,989PATENT V OFFICE‘ }
PROCESS FOR
NITRATION OF STARUH
Johann Belle and Alfons Kunz, Fnzfo. Hungary,
assignors to Nitrokém'ia ‘Ipartelepek Rész
vénytarsasalrBndapest, Hungary, a Hungarian
company
Application November 10, 1936, Serial No. 110,188
1mm May 22, 1936
4 Claims. (ct 260-145)
This invention relates to the nitration of starch into the mixed acid, and during the nitration pre
and it is an object of the invention to produce a
product which is uniformly nitrated throughout
and which is easily- ?lterable and consequently
easily separated from the spent acid, and further
cautions taken to ensure that the starch retains
as far as possible its well-powdered condition by
thorough stirring during the entire nitration op
eration. It is important to avoid the formation
v of lumps or at least to reduce such formation to
more a product which is easily- stabilized.
Different processes for the nitration of starch a minimum because these'lumps have an adverse
are already known. Concentrated nitric acid or effect on the quality of the product.
A process is known in which nitration is
a mixture of nitric and sulphuric acids (the so- ‘
effected with a’ mixed acid containing a high 10
10 called mixed acid) is used for the nitration.
The nitration process itself has been carried out proportion of nitric acid at temperatures of 10 to
at various temperatures between minus 10°_ C. 15° C. or at higher temperatures. Under these
5
up to plus 20 to 25° C. and even higher tempera
tures. Mixed acids have been used in which the
ratio of‘nitric to sulphuric acid has been 1:1 or
1:2 and in this case lower temperatures are em
ployed. Processes are also known in which. a
mixed acid is used which contains more than
50% nitric acid in which temperatures of 10 to
20° C. are employed. The ratio between the
starch and the acid used for nitrating was 1:10
and even more.
‘
The fundamental conditions for obtaining a
good nitro-starch is a uniform nitration, i. e.
each starch particle must so far as possible have
the same nitrogen content; it is further desirable
that the nitro-starch should be easily stabillzable
because uniform and stable explosives can only be
made from such nitro-starches with any degree
of reliability.
.
The principle of the invention consists in. the
realization of each of the conditions which are
necessary'to be complied with for the preparation
of such a nitro-starch.
According to the invention there is_ employed
is maintained during the nitration below plus
The result is very satisfactory if a mixed
40 acid is used which contains '75 to 85% HNO; and
25 to 15% H2804 and a temperature of approxi
mately minus 5° C. is maintained. Under these
conditions a water content of 1 to 2% in the acid
employed for the nitration does not‘ adversely
affect the good results.
'
‘ We have found that an easily ?lterable reaction
mixture is obtained if 4 to 6 parts by weight of
the nitrating acid are used for one part by weight
of the dry starch. Thev spent acid can/be com
mercially recovered from this reaction mixture
and the nitrated product can be further worked
up under favourable conditions.
known to use a. mixed acid containing more‘ than
50%_ sulphuric acid in which also higher tem
peratures are employed. This process has also
the above-mentioned disadvantages. 'On this‘ac 20
count, attempts havebeen made to work at lower
temperatures down to about 0° C. In this case
difficulties are met with in that the product pro
duced from such mixed acids, contains a high
proportion of sulphuric acid, is very dif?cult to 25
stabilize although it neitherbecomes pasty nor
does the starch go into solution. Such a mixed
acidyields a powdery product which is very
difficult to ?lter and the further working up of
which is ‘attended with di?lculties."
30
If the ratio between the amounts of starch and
nitrating acid is 1:445, preferably 1:4-5, in they
process of the invention then a thin Dulpy mass '
- is obtained from which the nitrating acid can be
for the nitration of the starch a mixed acid with
a content of '70 to 90% HNO; and the temperature
5° C.
conditions, the starch goes partly into solution,
the yield is adversely aifected, the product is
di?icult to ?lter and has a tendency to become 15
pasty, and. is not easy to stabilize. It is also
'
Well-dried starch in powder form is employed
with advantage for the nitration and provision
. should be made for the introduction'of the starch
easily separated.‘ Such a reaction mixture can, 35
in fact, ?lter_of itself. If, however, the reaction
mixture is thinner, then the ?ne starch'particles
which separate» from the coarser stop up the
?lter; washing out of the starch and recovery of
the nitrating acid are then more dimcult and a 40
very dilute spent acid is obtained. with regard to
the' two commercial considerations, itis particu- .
larly important that the above-mentioned
portions should be adhered. to.
The thorough stirring of the mixture during ‘the 45
nitration inhibits the formation of-lumps. The
nitration of such lumpy starch is only carried out
under very unsuitable . conditions, because the
nitrating acid‘ does not work uniformly on the
entire mass of the starch. The concentration ofv 50
the acid in each lump alters locally on account of
the using-up of the nitric acid during the re
action and also on account of the water freed as
a result of the reaction. The composition of the
nitratlng acid becomes unsuitable for the prepai ’56."
2
ration of a well nitrated starch and undergoes in nitrated product may be ‘commercially produced.
consequence of the reaction local heating. The ' In carrying out the process according to the in- .
result of working with such an acid is that the vention the apparatus, for example as shown in
the drawing, may conveniently be used.
‘
acid instead of nitrating the starch partly de
composes it, and there is obtained not only a
In the drawing Fig. 1 shows the nitration apl 5
product which is nitrated- to a different extent in paratus'in longitudinal sectionon the line l—i '
different parts,‘ but also which is dimcult to of Fig. 2 which is a plan section of the nitration
stabilize._ Furthermore, the yield is adversely‘ apparatus on the line ll-ll of Fig. 1. '
In the vessel III which is made of acid-resist
_ affected and the elimination of acid is-di?lcult‘
10 to carry out on account of di?icult ?ltration, and
ing material 'are two parallel plates II and I2 10
there is obtained a large amount of dilute spent
acid which can only be recovered at considerable
cost.
"
-.
'
which enclose with the walls .of-the vessel Ill and -
the cylinder casing I3, a cylindrical space for
' containing the cooling liquid. Into this cylin
>
According to the invention the nitration is
'15 further carried out in continuous operation in
drical space the cooling liquid is conducted
- through the pipe “and from which it ‘is con
which on the one hand the starch,‘ and on the ducted by means of the pipe 15. In- the interior
other hand the mixed acid, are mixed thoroughly ‘ It of the cylinder ii, the shaft 11 extends which
together in a continuous stream keeping the low
temperature constant, and the reaction mixture
isidrlv'en by the motor l8 and which isprovided
at the end which reaches into the cylindrical
‘20 is conducted down the reaction chamber in a
space IS with propeller arms 19. In the nitra 20
tion apparatus‘ the cooled mixed acid from the
_ Working continuously,‘ the amount of the’ container 24 and powdered starch from the con
:starch added and the amount of the mixed acid tainer 25 are conducted into the space 22 by
added and .further. the removal of the reaction means _of the pipes 26 and 21 respectively. In
mixture can be accurately regulated, so that it the space the two materials are continuously 25
is possible to allow the reaction ingredients to agitated by means of the propeller in the direc
enter the reaction chamber in correct propor
tion of the arrow. ' Meanwhile the mixture ?ows
tions and in relation to the size of the reaction from the space 20 ‘over the tubes 2| fixed in the
‘ chamber to allow them to act together for a .' plates II and i2 back to the space 22, ‘and are
correct period of time. The-added concentrated thoroughly cooled by bringing them into contact 30
mixed acid mixes in the reaction chamber im
with extended cooling surfaces. ‘The nitrated
continuous stream.
.
‘
mediately and continuously with the spent acid
material passes out at 22.‘
'
.
'
The propeller is preferably driven at a high
formed, which in consequence of the reaction
has an altered compositiom Consequently, ‘the
entire mass of thestarch, which is introduced
rotation, for example, 1,000 to 1.500 revolutions
during the nitration into the reaction chamber,
acid are intimately mixed the one with the other, 4
per minute. By this means the starch. and the 35
comes into‘ contact during the entire time ree 'so that in the apparatus a‘uniiorm pulp-like
quired in the reaction chamber with an acid of mass is formed. In consequence of the large
practically constant composition. The nitration number of revolutions of the propeller, the mass :
is moved along the ‘entire cooling surface with 40
40 is consequently uniform and‘every starch par
ticle has to a very large extent thesame content , su?lcient velocity. By this means the rapid and
‘of nitrogen. The extraordinarily 'uniformly uniform mixingof the acid and the starch is
nitrated starch so obtained is very easily stabil
achieved and the cooling of the mass ensures
’ized andv is suitable for the preparation of ex
nitration without decomposition of the material.
45
plosives ot the highest quality. The advantages
of continuous nitration will be apparent by a
I;c1;mparison with nitration processes worked in
tchea.
.
-
'
Example
45
The ordinary grain starch obtained in- the
trade is ground to fine powder, dried and used in
-With. batch nitration the composition of the’ the air-dry condition for nitration. In the nitra- >
tion apparatus the starch is conducted through
nitration. The starch added to the ‘nitrating the feeding device 25 driven by the electric motor
mixture at the beginning comes into contact with ll. Simultaneously, the mixed acid ?ows from
the most concentrated acid and a'highly nitrated the container 24 into the nitrating vessel which ' product is produced, that is to say,_a product of ‘contains-"80% HNO: and 20% HsSQl. This
~55 high nitrogen content. During the reaction a mixed acid is received into thev vessel in con 55
part-of the nitricacid is used up and wateris' tinuous circulation so\that thestarch falling into
50 acid alters progressively in the course of the
formed. The acid is progressively diluted so
‘that it has continually a different composition
the mixed acid mixes ‘thoroughly with this. The .
temperature of the mixed acid conducted to the '
and iorms a product with a_'correspondingly
apparatus is about minus 5° C..and the starch
lower nitrogen content. vThe nitrated product
and the mixed acid are so conducted into the
v_ consists thereforeof-a mixture of starch par
' ticles which are nitrated to a different degree.
_ This condition is, however, highly undesirable in >
illilhl-l‘atus that the ratio of their amounts in the
apparatus comes to 17:45. ‘The heat of the re
action set free in the nitration vessel is con
the ?nal product." In order to reduce the altera ' ducted away by the cooling means which circu
tion in the concentration of the nitrating acid late in ‘the cooling casings so that the tempera-_
during the reaction to the lowest possible degree ture during the nitration is in the neighbourhood
alarge excessofacidisemployedinthebatch 'of minus 5° C.1 The reaction mixture ?ows out
-method.' The employment of a large excess of of the nitration vessel in an amount correspond-.
acid is, however, not commercial, and underithese
circumstances '- the ?ltering properties - of
‘310 ‘ product
are adversely a?ected. .
the
By working continuously in accordance with
the invention the above-mentioned disadvan
ing approximately to the amount of the starch
and mixed acid conducted into ‘the apparatus.
7
The reaction chamber of the apparatus is so di
mensioned, and the amount of acid and starch
v conducted into the apparatus is so determined
tages are avoided and with relatively small, that the entire amount of reaction- mixture pres
76
amountsgof acid .an extraordinary. uniformly
ent in the apparatus is renewed in about half an 7
3
2,112,989
hour. This time is su?lcient for the purpose of
carrying out fully the nitration. As, however,
the in?owing and out?owing go on continuous
ly, it can happen that a few starch particles may
leave the nitration apparatus before the expira
tion of this time. On this account in order to en
sure uniform and complete nitration, the reaction
mixture which ?ows out at 23 is submitted to' a
further nitration. This further nitration is car
10 ried out in an apparatus similar to that above de
scribed, consisting of. a vessel with mixing device
and cooling device in which the temperature of
_ the reaction is maintained also at about minus
5° C. and the reaction-product is thoroughly
15 stirred. The reaction mixture leaves this ap
paratus in‘ which the further nitration takes place
also by over?owing. The over?ow mixture is
separated from the acid in. known manner,
washed, stabilized and worked up into gun powder
Working in accordance with the example given,‘
a nitro-starch is obtained containing 12.8%
' nitrogen and the yield reckoned on dry starch
comes to 168%.
>
_
The hygroscopic measurement of the nitro
starch prepared according to this process is at
least the same as that of nitro-cellulose with the
_
.'
‘
The nitro-starch prepared according to the in
vention has a far-reaching uniform nitrogen con
tent, and the stability of gun powders or ex
plosives prepared therefrom is the same as that
of nitro-cellulose products with the correspond
ing nitrogen content.
1'. A process for the nitration of starch which - I
comprises mixing together dry powdered starch
and nitrating acid containing 70 to 90% nitric
acid, and maintaining the temperatureduring the
mixing operation and until the end of the re
action below plus 5° C.
-
'
»
2. A processfor the nitration of starch which
comprisesmixing together dry powdered starch
and nitrating acid containing‘ '75 to 85% nitric ,10
acid and 15 to 25% sulphuric acid, and maintain
ing the temperature during the mixing operation
and until the end of the re-acti_on at about —5‘’ C.
3. A process for'the nitration of starch which
comprises mixing together one part by weight of 15
dry powdered starch and four to six parts by
weight of nitrating acid'containing '70 to 90%
nitric acid, and maintaining the temperature dur
ing mixing operation and until the end of the
re-action below plus 5° C.
or explosives.
same nitrogen content.
We vclaim:
'
‘
,
20
v
4. A process for nitrating starch in which a
stream of the dry powdered starch is brought to
gether with a stream of the nitrating mixture
containing 70%-,90% nitric acid, and the tem
perature of the mixture is maintained below 5° C. 25
and the reaction mixture is assembled in a cooled
space for the purpose of completing the nitration
wherein the nitratinglmixture is agitated and its
_temperature maintained below 5° C. and'?nally,
the nitro starch is separated from the acid in 30
known manner.
v .
ALFONS KUNZ.‘
JOHANN HELLE._
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