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Патент USA US2405104

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July 3%, 19416.
' Filed Aug. 7, 1941
W; “Ram Mydahfi
Patented July 30, 1946
William E. Mydans, Cambridge, Mass.
Application August 7, 1941, Serial No. 405,879
1 Claim.
(Cl. 102-97)
(Granted under the act of March 3, 1883, as
amended April 30, 1928; 370 0. G. 757)
The invention described herein may be manu
factured and used by or for the Government for
in contact with pyrocellulose and other mixed
governmental purposes, without the payment to
me of any royalty thereon.
This invention relates to ordnance powder bags
5. The containers or bags should have mechan
ical strengthadequate to retain the powder and
to permit‘the reasonably rough handling that
may be required under the pressure of battle.
6. The powder bag material should introduce
or containers.
In large caliber guns it is customary to load a
projectile into a, gun through an opened breach,
no new defects or hazards such as the holding
then to insert propellent powder in an amount to
of static electric charges or the release of acrid
give the desired range. Finally, the detonator is 10 or toxic vapors which might affect men within a
gun turret housing.
inserted and the breach closed. The propellent
powder, which is usually a pyrocellulose or mixed
In addition to the foregoing properties, these
pyrocellulose-nitroglycerine composition formed
materials should also possess the following ad
into grains varying in size with the gun caliber
vantages which, however, are not prerequisites for
and containing perforations to control the rate 15 a satisfactory and acceptable powder bag.
or" burning, is contained in a sack or bag. One
7. The materials should have properties which
important and necessary characteristic of the
are well-known. These materials should be able
material from which these bags is made is that
to be readily worked or prepared on equipment
‘following the explosion, whatever residue re
which has already‘ been developed and is readily
mains must cease immediately to burn, glow, or 20 available.
smoulder and so make possible the immediate in
8. The materials should be light in weight and
troduction of the next charge with safety. This
so add little to transport di?iculties. They should
property is lacking in all ?bers of vegetable origin.
be low in bulk and so require no changes in the
For many years, powder bags for large caliber
volume or design of the present gun barrels.
ordnance have been made from a natural silk 25
9. The containers made from these materials
cloth. Silk has the desired property of no “after
should be waterproof and watertight, thus per
glow” but is expensive-and is obtainable only from
mitting the use of component parts of the pro
foreign sources.
pellent charge which are sensitive to water.
An object of this invention is to devise ord
The above and other features of my invention
nance powder bags or containers made chie?y 30 may be best understood from the following de
from other than naturally occurring animal or
scription of exempli?cations thereof, reference
vegetable ?bers.
being had to the accompanying drawing wherein
Another object is to devise such powder‘ba‘gs
the single ?gure represents a cross-section
from materials which, in addition to the attri
through a powder bag incorporating my inven
butes of silk, possess the advantages of being inex
pensive, readily available, and highly stable dur
I may construct my novel powder bags of a.
ing long periods of storage.
ntirocellulose composition. Such a material pos
In accordance with my invention, it is desir
sesses in great measure all of the advantages out
able to construct ordnance powder‘ bags from
lined above. Since the major component of the
synthetic organic ‘materials which have the fol 40 propellent charge is nitrocellulose (usually pyro
lowing desirable properties:
cellulose of between 12 and 13.4% nitrogen) a
1. These materials should burn or be consumed
nitrocellulose bag introduces a material not dis
during the explosion of thepropellent powder
and if any residue remains at the termination of
similar to the propellent charge.
However, for
the powder bags, I prefer to use a nitrocellulose of
such explosion, said residue should immediately ' 45 somewhat lower nitrogen content than pyrocellu
cease to burn, glow or‘ smoulder.
lose, such as a plastic or coating grade of nitro
2. These materials should burn with the least
cellulose, i. e., of about 10 to 12% nitrogen.
possible residue, thus minimizing gun fouling;
The nitrocellulose may be employed in the
and further, any residue which remains should
formation of powder bags in a number of ways.
neither contain nor generate substances corro 50 For example, nitrocellulose may'?rst be dissolved
sive to the gun barrel.
in suitable solvents. 'Such solvents, which may
3. The materials should be readily available
from domestic sources and be low in cost.
be employed singly or in various combinations,
include the following types: Alcohols, aldehydes,
ketones, chlorinated hydrocarbons, ethers, esters,
4. The materials should be stable when sub
jected to moisture, light, and ‘storage even when 55 nltropara?ins, ‘hydroxyaldehycles,
tones, and the like. Aliphatic, aromatic and
alicyclic hydrocarbons may be employed as dil
uen s. The speci?c solvents or combination of
solvents chosen will depend on a number of fac
tors which include the boiling or evaporation
ranges desired, the degree if nitration of the nitro
cellulose employed, the viscosity characteristics
desired in the solution to be cast or coated, the
solubility characteristics of the plasticizers, res
shown at 4, the material may be stitched prefer
ably with silk thread or may be cemented with
the cementing compositions already described.
Instead of using two layers of nitrocellulose
?lm, one or both of said layers may be replaced
by a ?lm of other suitable material such as ethyl
‘cellulose; cellulose acetate, 0 ein or other pro
> tein-p-lastic ?lm in order to secure lower in?am
mability in handling and transportation, reduced
inous materials, cellulose ethers, and the like, l0 tendency toward accumulation of static electric
charges or other modi?ed physical properties.
which may be incorporated, the ?ammability of
Since the physical properties thus enumerated are
the solvent mixture, the ease of solvent recovery,
usually desirable for the external surface of the
resistance to ?lm blushing, etc.
bag, preferably such material will be substituted
The nitrocellulose solution thus prepared may
be cast in the form of a ?lm or may be used to
coat a fabric backer as will be described below.
for the nitrocellulose layer 2 as shown in the
One method of producing the laminated struc
ies may be incorporated in the solution before the , V ture as shown in the drawing is to pass the light
weight textile materials enumerated above in a
?lm is castso as to impart to the ?lm the desired
degree of flexibility and strength.
'20 continuous web under, a spray of or through the
nitrocellulose plasticized lacquer solutions to pro
Among the plasticizers that may be used, singly
duce thereon a continuous ?lm. In order to se
or in various combinations to give plasticity or
cure sufficient thickness multiple coats may be
suppleness to the ?lm are the following types;
As already stated plasticizers and resinous bod
camphor, triaryl and trialkyl phosphates, phthal
ate esters, aryl and alkyl sulfonamides, butyl
phthalyl-butyl-glycollate and related materials,
castor oil, blown and heat-bodies vegetable oils,
methyl abietate, tartaric acid esters, citric acid
, esters, lactic acid esters, and the like.
Where a
minimum of ash and corrosive products are de
sired, it is preferable to avoid the use of plasticiz
ers containing inorganic constituents, such as tri
cresyl phosphate and chlorinated diphenyls.
Among the resinous materials that may be em
ployed, singly or in various combinations to add
body, stiffness, stability, or other modifying prop
erty to the ?lm are: Alkyd resins, preferably in
the “B” or soluble stage, rosin, rosin esters, tolu
ene sulfonamide-formaldehyde resins, furfural
ketone resins, dammar, terpene resins, urea
formaldehyde resin solutions in butanol, mela
required with drying of the ?lm with each appli
25 cation.
If desired the ?nal coating may be of some
other film forming material such as ethyl cellu
lose, cellulose acetate, isobutene polymer, casein,
zein, etc., in order to secure modi?cation of the
30 physical properties, especially as it relates to
?ammability during handling and transportation
and reduced tendency toward the accumulation of
static electrical charges.
The use of low viscosity nitrocellulose in the
above process will permit the building up of coat
ings of appreciable thickness with a minimum
number of applications.
Comparatively thick
sheets of nitrocellulose ?lms may be applied to the
fabric web from aqueous emulsions by dipping or
under a doctor knife with the advantages of re
duced solvents, elimination of solvent recovery
systems, lowered ?re hazard and ease of applica
Nitrocellulose ?lm, especially in the thicker
rials having a nitrogen content range of 10 to 45 gauges, may be deep-drawn by the application of
heat and pressure to make seamless containers of
12%. The viscosity properties may likewise be
high mechanical strength and water resistance
selected to secure a coating or casting solution of
with low weight and bulk. Such a container,
the desired properties. Where proper considera
e. g., a cylinderwith bottom integrally formed and
tion is given to the plasticizers Or other materials
present in the solution, scrap nitrocelullose ?lm or 50 having a diameter to ?t snugly into the gun barrel
can be ?lled with the powder charge and the top
other waste nitrocellulose products may be em
sealed by crimp-?tting or cementing in place a
circular disc of the same material. Such a
The ?lm may be formed in any suitable man
method of processing lends itself readily to mass
‘her, as by casting and drying in the usual way.
The ?lm is then formed into bags or sacks by 55 production technique.
Instead of making the powder bags of nitrocel
stitching, as with silk thread, or by cementing
lulose ?lm, the powder bags may be made in fab‘
with resinous or nitrocellulose composition adhe
ric form from spun nitrocellulose yarn that has
sives or with ‘medium-boiling nitrocellulose sol
vents such as the monoethyl ether of diethylene
not been denitri?ed, i. e., treated to hydrolyze .o?
60 some of the nitrate groups and thus reduce its
in?ammability. Such nitrocellulose fabrics can
Instead of constructing the powder bag of a
easily be made by nitrating puri?ed cotton fabric
single thicknessof ?lm as described above, the
of the correct weight and weave in batch nitra
bag maybe made of laminated material as shown
tions or even in continuous process nitration.
in the drawing. The inter-layer I may be of
Conventional nitrating mixtures of nitric and sul
some light weight fabric such as silk “mummy”
furic acids are used with carefully controlled tem
cloth, which is a silk cheesecloth having a very
peratures. Thereafter the nitrated' fabric is
low weight of silk per square yard. Likewise this
washed, stabilized by boiling in dilute acid'solu~
interlayer may be of wool, cellulose acetate, syn
tions, then in water, then in dilute alkaline solu
thetic casein or soy bean ?ber cloth, nitrocellulose
fabric which may be prepared as described below, 70 tions, and then again in water to remove hemi
celluloses, cellulose sulfates and low nitrate esters
and such other synthetic fabrics as represented
that contribute to instability. The» material is
by ‘-‘nylon.” On each side of the interlayerv l is
then dried.
formed the ?lms 2 and 3 cast, coated or cemented
In batch nitrations the foregoing process could
on said interlayer. Where the edges of the lami
be carried out either on the piece goods or on the
nated material forms a seam as, for example, is
mine-formaldehyde resins, and the like.
The nitrocellulose which is dissolved as de
scribed above is preferably selected from mate
complete cotton bags after cutting and sewing.
Under carefully controlled conditions of nitration,
the ‘cotton fabric not only does not lose its me
chanical strength but such strength may be in
respect. Tests on commercial ethyl cellulose and
cast ethyl cellulose ?lm have shown the mate
rial to have a very low degree of flammability,
and ?lms once lighted have no tendency to con
tinue to burn, glow or smoulder when‘ the ignit
creased. In this form, nitrocellulose of any de
ing flame is removed. Ethyl cellulose ?lm may
gree of nitration between 9% and 14% nitrogen
may be employed although I prefer to use a collo_
be made in a variety of ?lm-thicknesses, widths
and in combination with a variety of plasticizers,
dion stage with nitrogen content of about 10%
resins and waxes to give ?lms having a wide
to 12%.
variety of physical characteristics. In addition
Were the powder bags to -be made of nitrocel
to using ethyl cellulose in a laminated material,
lulose yarn, it is desirable to nitrate the cotton
the ethyl cellulose ?lm itself may be utilized.
cloth or the completed bags as described above
Powder bags can be formed from such ?lm by
in order to eliminate the necessity of looming so
stitching or cementing. Ethyl cellulose is- com
inflammable material as nitrocellulose yarn.
In‘ the arrangement as shown in the drawing 15 patible with nitrocellulose and may be used in
the interlayer i may be made of a light weight
combination with nitrocellulose, together with
plasticizers and resins if desired, to give ?lms
cotton cloth nitrated as described above. Such
having modi?ed physical properties, such as the
'nitrated cloth as 'I have described abovec'may be"
rate of burning, decreased ?ammability during
modi?ed by immersion in solvents, ‘in solvent
plasticizer mixtures, in solvent-plasticizer-resin 20 handling and transportation, and increased flex
solutions, all with or without the addition of
non-solvent diluents, e. g., hydrocarbons. By
such treatment over controlled periods of time,
partial or extensive swelling or “colloidizing” of
the‘ nitrated ?ber may be accomplished, together
with absorption by the ?ber of such plasticizers
and/or resins that have solvent power or affinity
Other cellulose ethers, such as benzyl cellulose,
have similar properties and may be substituted
for ethyl cellulose in these applications.
Ethyl cellulose is soluble in a wide variety of
solvents, particularly in mixed solvents, and is
compatible with a wide variety of plasticizers,
resins, waxes, raw, blown or heat-bodied oils,
for nitrocellulose. Dyes, which, for example may
be used to characterize the type of powder to be
bituminoussubstances, etc., making possible the
contained in the bag, may be incorporated at this 30 formation of ?lm having a wide variety of physi
cal properties.
stage. On subsequent drying, such treatment
Cellulose acetate, mentioned as a component
will serve to cement adjoining ?bers together to
part of the laminated material from which my
give a more impervious and stiffer fabric, though
novel powder bags may be made, also has prop
the latter may be modi?ed Widely by the choice
of plasticizers and/or resins that may be em 35 erties suitable for this purpose. Flame tests on
commercial cellulose acetate ?lm have shown that
ployed. The solvents, plasticizers and resins al
the material burns and also fuses readily, but the
ready listed above are suitable for this purpose.
films once lighted have no tendency to continue
The nitrocellulose of which my novel powder
to burn, glow or smoulder when the igniting
bags are made may be employed mixed with cellu
lose ethers such as ethyl cellulose in order to con 40 ?ame is removed. Cellulose acetate is available
in the form of yarn and in a great variety of
trol its various physical properties such as rate
woven and knitted fabrics, and also in the form
of burning, stiffness, melting or softening point.
of ?lm in a variety of widths, thicknesses. and
The ?nished nitrocellulose bag or container
plasticizer-resin compositions having a wide vari
may be given a coating of graphite in a thin
lacquer or other suitable adhesive or binder in 45 ety of physical properties. In addition to the
use of cellulose acetate as one or more of the
order to facilitate the ready dissipation of any
layers of the laminated structure as shown inthe
static electrical charges that may accumulate.
drawing, powder bags may be made by knitting
The same end may be achieved by coating the
cellulose acetate yarn or by cutting and stitching
bags with very thin ?lms of hygroscopic or mois
ture-retaining material such as gelatin-glycerol 50 suitable cellulose acetate fabrics into the desired
shapes. The ?nished fabric container may be
water combinations, with or without the incor
poration of graphite.
coated with ?lms of nitro-cellulose to accelerate
burning during the combustion of the charge or
“Nylon,” which I have mentioned above, is
to make the container more impervious to mois
formed by the condensation of aliphatic dicar
boxylic acids with aliphatic diamines. It is a 55 ture transfer.
The cellulose acetate ?lm, especially in the
molecularly oriented, high-molecular weight
thicker gauges, may be deep-drawn by the appli
polyamid and as such bears a close chemical rela
cation of heat and pressure to form seamless con
tionship to silk and wool. It melts at a lower
tainers of high mechanical strength. Such a con
temperature than does silk, but fails to burn when
exposed to a free ?ame, even when a thin fabric 60 tainer, e. g., a cylinder with an integrally formed
bottom and having a diameter snugly ?tting the
of this material is held directly in a ?ame. This
gun barrel can be ?lled with the powder charge
material, drawn into ?laments suitable for knit
ting or spinning, can be formed into powder bags
and the top sealed by crimp-?tting or cementing
or sacks that will show no after-glow following
in place a circular disc of the same material.
the combustion of the explosive charge. Alter
natively, the material can be extruded through a
slit and stretched before cooling to yield a strong,
durable, light-weight ?lm that may be formed
into powder containers by stitching or cement
65 Such a processing method lends itself readily to
mass production technique.
Similarly, as detailed above in the application
of nitrocellulose and ethyl cellulose to this prob
lem, cellulose acetate ?lm can be formed into
ing. As already stated, thin “nylon” fabrics may 70 bags by stitching or cementing, or composite ?lm
of high mechanical strength can be produced by
serve as the interlayer I of the laminated mate
rial as shown in the drawing.
laminating two cellulose acetate ?lms to a rein
forcing interlayer of suitable fabric. Or, for one
Ethyl cellulose, which I have indicated may be
of the cellulose acetate ?lms in the composite
used as a component part of my novel powder
bag, has properties which are desirable in this 75 ?lm, other ?lm materials may be substituted,
ers that meet the basic requirements of a satis
factory powder bag. These materials may be
compounded with suitable plasticizers, resinous
e.; g., nitrocellulose ?lm to give accelerated burn
ing during the combustion of the charge.
, _Fabrics may be coated with cellulose acetate
> compositions (cellulose acetate, together with
materials, waxes, etc., and cast into ?lms, coated
suitable plasticizers and resins if desired, homo Cl on fabrics or upon other ?lm material to yield de
sirable products for my purpose. The resulting
geneously dispersed in suitable solvents) by
spraying or immersing the continuous fabric web
?lms may be hardened or cured by treatment
with formaldehyde and may be rendered less
sensitive to water and more readily inflammable
,Other cellulose esters and mixed esters have
similar properties to cellulose acetate and may be 10 during combustion of the charge by a coating of
substituted for the latter in Whole or in part to
cellulose-nitrate, wax, resin, or similar materials,
secure modi?ed physical properties. These in
It is desirable to avoid the use of ?xed alkalis
clude cellulose acetobutyrate, and cellulose aceto
and the like as solubilizers in preparing the pro
tein solutions, or the use of alums, chromic salts
Instead of the synthetic cellulose materials al 15 and the like as hardening or curing agents, as
with such solutions.
ready described, isobutene polymers may be used 7
such a practice will lead to a high ash or residue
in the construction of powder bags.
in the gun after combustion. Urea and various
Isobutene polymers are available in different
aliphatic amines make suitable protein solubiliz
degrees of polymerization ranging from thick
ing agents,v though zein is readily dissolved in
syrup-like ?uids to rubber-like materials. These 20 80%’ ethanol. Polyhydric alcohols and amides
materials have the unique property of volatiliz
make suitable plasticizers and rosin, manilla
ing without residue when subjected to tempera
copal, and shellac are examples of suitable resins
tures of 400-500“ F. and higher. These isobu
for use in such compositions to add to the body
tene polymers are compatible in general with ma—
and modify the ?lm properties. These protein
terials having very low contained oxygen per
centages, e. g., Waxes in general, including paraf
?n and ozokerite waxes, petrolatum, rubber, as
25 ?lm materials have no tendency toward the ac
phalts, pitches, rosin, rosin esters, dammar, ter
pene resins, and the like. Isobutene polymers
can be compounded with various combinations 30
of the above substances and dissolved in aliphatic,
aromatic or alicyclic hydrocarbons, terpenes, chlo
rinated hydrocarbons, etc. to yield a material
cumulation of static electric charges.
The term “coating” as used in the appended
claim is intended to include applied pre-formed
?lms as well as coverings applied in liquid or
plastic form.
What is claimed is:
An ordnance powder bag of the type which
when ?lled with a propellent powder charge is
adapted for insertion into a gun ‘barrel for use as
suitable for coating fabrics such as those listed
above as reinforcing-interlayers, to yield suitable 35 the propellant for separate loading ammunition,
bag or container material or for coating other
said bag having its walls formed of a composite
sheet or ?lm material to secure modi?cation of
sheet-like material formed of a light weight com
the physical properties of the latter. Isobutene
bustible fabric on each side of which is a ?lm of
polymers, suitable for use according to the inven
tion, appear on the market under the trade 40 nitrocellulose adhering thereto and having upon
the nitrocellulose ?lm exteriorly ‘of the bag a
name “Vistanex.”
coating of a combustible material which has less
The protein-plastic materials mentioned above
?ammability and less tendency to accumulate
as being useful in ?lm form as one of the layers
static electricity than nitrocellulose, and having
of the laminated structure shown in the drawing
are also available in fabrics and in woven and 45 upon the last mentioned coating a coating com
knitted fabrics. Such protein-plastic materials
have been made from puri?ed casein andysoy
proteins and also from zein from corn.
chemical nature of these materials bear a close
relationship to that of silk and wool and such ma
terials may be made into powder bags or contain—
prising a material which is a conductor of elec
tricity whereby static electric charges accumulat
ing'upon the bag may be allowed to escape from
the bag.
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