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Патент USA US2407151

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Patented ‘sepg. 3, 1946'
Richard 0. Glogau, Woodbury, N. 1., assignor to
E. I. du Pont de Nemours & Company, Wil
mington, Del., a corporation of Delaware
‘No Drawing. Application August 17, 1944,
Serial No. 549,959
’ 12 Claims.
?owing properties. As has been stated, satisfac
This invention relates to a method of treat
tory silicon-containing compounds for‘use must _
be such as are difficultly soluble in water.‘ So
ing water-soluble materials and of effecting
thereby a marked decrease in their tendency to
dium silicate,‘ for example, is not applicable.
Likewise, naturally occurring silica is not suit
become set or caked in hard masses. More par
ticularly it relates to ammonium nitrate so treat
able, whether granular or occurring in a form
ed and to explosive compositions containing con
siderable amounts of this salt.
Ammonium nitrate is an important ingredient
such as kieselguhr.
While various silicon-containing compounds
‘ of explosive compositions because of its attrac
are applicable in accordance with my invention
disadvantage, however, of being highly hygro
?nd ?nely divided calcium silicate particularly
tive properties and its availability. It has the 10 for protecting the ammonium nitrate grains, I
e?ective. A suitable form is the one obtained
by precipitation from a solution of a calcium
readily. Largely for this reason, ammonium ni
salt by means of sodium or other soluble silicate.
trate on storage tends to set and become caked in
solid masses that can be broken up only with 15 A dried product having a particle diameter for
at least 50% of the grains of not less than 1
great di?‘lculty. This caking tendency has a de
micron is desirable for use. Amorphous precipi
sensitizing effect on the ammonium nitrate and
tated silica also is a satisfactory coating agent,
under very adverse conditions may render ex
scopic and of absorbing water or moisture very
and this and other silicate coatings should be in
plosives containing it incapable of satisfactory
20 very ?nely divided form. With a particle diam
eter of the magnitude mentioned, the coating ma
Other water-soluble compounds and salts ex
terial will be of such a degree of fineness as to
hibit the same tendency to set, and various meth
ods have been proposed ‘for overcoming this dis
advantage. No entirely satisfactory means has
been found, however, for solving the problem. '
be readily capable of passing through a 325-mesh
lar compounds. ' A further object is such a meth
od which can be used effectively in the prepara
tion of explosives containing ammonium nitrate
and other water-soluble ‘salts. A still further ob
iect is a composition of matter of greatly in
creased resistance to setting because of a novel
found a‘ suitable amount of calcium silicate or
other analogousmaterial for_use to be between .
0.05% and 5.0%, based on the weight of the
method or treatment. A further object is a com- I
position comprising ammonium nitrate coated
with an effective anti-setting agent. Additional
objects will be disclosed as the invention is de
The silica or silicate coating may be applied
to the ammonium nitrate by various methods
and at various stages in the treatment of the salt.
It may be added during the graining process, if
desired, or to the final ammonium nitrate prod
uct by agitating the mixture of ammonium nitrate
and coating agent. As previously stated, I have
An object of the present invention is a method
for preventing the caking of water-soluble, granu
water-soluble salt to be coated.
The bene?cial e?ect of the silicate coating in
preventing undue setting of ammonium nitrate
was shown by tests carried out on treated sam
ples. ‘ Hot, dry ammonium nitrate was screened,
I have found that the foregoing advantages are
accomplished when I coat the particles of am 40 introduced with the desired amount of coating
material into 32-oz. bottles, and mixed for 10-15
monium nitrate with a ?nely divided, silicon
scribed more at length hereinafter.
containing compound.
The silicon-containing
compound found effective by me is taken from
the group consisting ofv the dif?cultly soluble
inorganic silicates and precipitated silica. While
varying amounts of the silicon-containing coating
may be used with advantageous effect on the
properties of the salt coated, I preferably use
between 0.05% and 5% 'of the coating agent.
minutes, after which 90-gram portions of the re
spective mixtures were placed in iron pipe sec
tions 3 inches long and 2 inches in diameter, the
material being compressed with a 25-lb. weight
and then tightly st'oppered. The samples thus
prepared were stored alternately under hot
(‘iii-49° C.) and normal (20° C.) conditions, each
sample remaining three days at each tempera
since an amount lower than 0.05% is insu?cient 50 ture. The material was passed through the tran
sition point (32° C.) as many times as desired,
to give adequate protection, while more than 5%
maintained in upright position. The compressed
means unnecessary contamination with foreign
pellets were then removed from the tubes and
inert. material with little further protection. Am
the pressure determined which was necessary to
monium nitrate so protected possesses a greatly
crush them. Increased pressure indicated set
decreased tendency to set and has improved free
' ting oi the salt.
The following results were ob
particles with a ?nely divided material taken
from the group consisting of the dii?cultly soluble
Crushing pressure, pounds,
Setting inhibitor
paislgges through transition
inorganic silicates and'precipitated silica.
sive compositions containing ammonium nitrate,
which comprises coating the ammonium nitrate
2. A method of preventing the setting of water
soluble granular materials which comprises coat
1 ing the grains of said materials with a ?nely di
None .............................. ._
Silica __________________ _l
Calcium silicate _______ -_
I- N
vided compound taken from the group consisting
10 of the di?icultly soluble inorganic silicates and
precipitated silica.
3. The method of claim 2, in which the coating '
' compound is of a ?neness such that the particle
diameter of at least 50% thereof is less than 1
cium silicate coating is plainly brought out in
15 micron.
the above tabulation.
4. The method of claim 2, in which the material‘
The compositions of my invention are advanta
The protection against setting offered by the cal
is coated with calcium silicate.
seous not only from the viewpoint of prevention
5. An‘explosive composition of increased re- '
of setting, but for other purposes also. The coat
sistance to setting comprising a water-soluble
ing of the ammonium nitrate particles with the
?nely divided silicon-containing compound like 20 inorganic oxidizing agent coated with a ?nely
divided material taken from the group consisting
wise protects the material from water and mois
of the dii?cultly soluble inorganic silicates and
ture penetration, and causes the salt to remain in
precipitated silica.
free ?owing condition so that it can be poured
more readily. The improved coating of my in
6. An explosive composition of increased re
vention has the advantage over other materials 25 sistance to setting comprising ammonium nitrate
coated with a ?nely divided material taken from
used that it is inert and non-reacting with respect
the group consisting of the di?icultly soluble inor.
to the salt coated Or to materials with which the
ganic silicates and precipitated silica.
salt is mixed. Organicicoating agents suffer from
7. A composition of matter comprising a water
the drawback that they are reactable with oxi
soluble compound coated with a ?nely divided
dizing agents, so that some hazard may be intro
material taken from the group consisting of the
duced with such combinations at elevated tem—
di?icultly soluble inorganic silicates and. precipi
tated silica.
Storage tests of dynamite compositions high in
8. The composition of claim 7, in which the
ammonium nitrate content demonstrated that
calcium silicate and other silicon-containing com 35 water-soluble compound is sodium nitrite.
9. The composition of claim '7, in which the
pounds within the scope of my invention in ?nely
water-soluble compound is sodium nitrate.
divided’ state acted effectively as anti-setting
10. The composition of claim '7, in which the
agents for the mixed explosives.
water-soluble compound is ammonium nitrate.
Particular mention has been made of the appli
11. A composition comprising ammonium ni
cation of the silicon-containing compounds of 40
I trate having its individual particles coated with
my invention as an inhibiting coating on am
a ?nely divided silicon-containing compound in
monium nitrate. A similar bene?cial eiiect is
likewise obtained when the same coating is used
an amount between 0.05% and 5% by weight 01‘
for other water-soluble materials, especially such 45 the ammonium nitrate, said coating compound
inorganic compounds as sodium nitrate, sodium
being taken from the group consisting of the dif
nitrite, and the like.
?cultly soluble inorganic silicates and precipi
It will be understood that the coated materials
tated silica.
described in the foregoing may be used by them
12. The composition of claim 11, in which the
selves or be present as ingredients of various
silicon-containing compound is precipitated c_al-'
compositions. I intend to be limited only by the
following patent claims.
I claim:
1. A method of preventing the caking of explo
cium silicate.
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