US2221391A - Manufacture of double base propellent powders - Google Patents

Description

NOV. 9 E. WHITWORTH EI'AL 2,221,391

MANUFACTURE OF DOUBLE BASE PROPELLENT POWDERS Filed July 28, 1939 Thomas- Thomson 'Ldward Wlzz'zworzb m OR ATTORNEY Patented Nov. 12 1940 UNITED STATES PATENT OFFICE MANUFACTURE OF DOUBLE BASE PROPELLENT POWDERS Application July 28, 1939, Serial No. 286,970 In Great Britain August 2, 1938 Claims. (01. 52-13) The present invention relates to the manufac- I ture of double-base propellentpowders; that is to say, propellent powders in which the active base comprises both nitrocellulose and nitroglycerine.

In the manufacture of certain propellent powders, nitrocellulose, in the form of nitrated comminuted paper board or the like, has been directly treated with nitroglycerine; these powders however retain a fibrous structure, and are not free-flowing. In the manufacture of non-fibrous free-flowing granular double-base propellent powders it has hitherto been necessary to gelatinise the fibrous nitrocellulose by a volatile or non-volatile nitrocellulose solvent, with or without nitroglycerine; the grains being formed after gelatinisation irrespective of the original degree of subdivision of the fibrous nitrocellulose.

This invention hasas an object to devise a new method of manufacturing granular double-base 2 propellent powders. A further object is to devise such a method which will provide a non-fibrous free-flowing granular powder with greater simplicity and economy than by known methods. Further objects will appear hereinafter. These 25 objects are accomplished by the following invention.

We have found that we can achieve these objects by employing nitrocellulose in the form of a product obtained by the nitration and comminu- 30 tion, in either order, of regenerated-cellulose sheet material, and treating the product with nitroglycerine in the presence of a volatile medium that is a non-solvent fornitrocellulose. The nonfibrous nature of regenerated-cellulose sheet ma- 85 terial and its nitration product renders it possible to effect the comminution of these materials to a size suitable for powder-grain formation (without destruction of the lamellar form of the particles) and the sheet material may be, if de- 4o sired, partly or wholly comminuted while in the water-wet state by mechanical means, such, for

instance, as beating or pulping machines. The

comminution may be carried out partly or wholly before or after the nitration of the regenerated 45 cellulose.

The comminuted nitrated regenerated-cellulose sheet material may, for instance, be produced by nitration of deglycerinated scrap commercial regenerated-cellulose sheet of about 0.001 in. in

50 thickness. Such scrap material can be obtained for instance from the waste left when sheets of regenerated cellulose material are out to size. A suitable method for the production of nitrated regenerated-cellulose sheet material for the pur- 55 poses of the present invention consists in comminuting the waste commercial regenerated-cellulose sheet into the form of small crumpled pieces of single thicknesses and washing repeatedly with water, for instance at a temperature of about 40 C.-45 C., to remove the polyhydric al- 5 cohol employed as softening agent, and .to float 011 any lacquer that may have been applied to the surface of the sheet. The product thus freed from foreign constituents is centrifuged, dried, and nitrated, advantageously at a temperature of 40 C.-60 C. with from -45 parts by weight of a nitrating acid containing at least 16% of water, sulphuric acid in amounts up to 65% and from 19-30% nitric acid. The fragments of comminuted nitrated regenerated-cellulose sheet mal6 terial may, for instance, be less than 1 mm. square.

Another suitable method for the production of nitrated regenerated cellulose sheet material is to comminute such sheet material of ab'out0.001 in. 20 thickness in a pulper to fragments of a size varying from about 0.01 in. square up to about 0.04 in. square.

The treatment of the comminuted nitrated product with nitroglycerine in a nitrocellulose non-solvent volatile medium may be carried out with agitation in known manner; e. g. in aqueous suspension or by use as a vehicle of another liquid that does not dissolve nitrocellulose. Moderants or other additional ingredients may be 80 introduced into the product either at, the same time, or subsequently. During the treatment of, the nitrated comminuted regenerated cellulose with the nitroglycerine, the particles may agglomerate to some extent; but powders of satisfactorily uniform grain size and excellent ballistic properties can nevertheless be obtained in the manner described.

The invention is further illustrated but not limited by the following examples, in which the parts are parts by weight, and which refer to the production of shotgun powders.

Example 1 Scrap commercial regenerated cellulose mate- 5 rial about 0.001 in. in thickness is comminuted in a pulper to fragments of a size varying from about 0.01-0.02 in. square up to about 0.04' in.

square. The comminuted mass is washed with hot water at C. to remove all soluble foreign matter from the regenerated cellulose and to float off any insoluble lacquer or wax coating. The purified comminuted regenerated cellulose is centrifuged, dried, and nitrated at a temperature not exceeding 40 C. with 25 times its weight of a nitrating acid containing 35.2% sulphuric acid, nitric acid and 14.8% water, washed and stabilised.

100 lbs. of this 'nitrated regenerated cellulose made from commercial material 0.001 in. thick in comminuted thin sheet form, are suspended in 300 lbs. water at 25 C. in a rotating copper pan. 40 lbs. nitroglycerine containing 5-lbs. diethyl phthalate are added gradually through a rosespray, and mixing is continued for 1 hour.

The pan is then discharged and the impregnated powder is steeped for 24 hours at C. in a solution containing, for every lb. nitrated regenerated cellulose, 87 lb. barium nitrate and 21 lb. potassium nitrate dissolved in 56 gallons of water. At the end of this time the powder is removed and drained. It is sieved while still wet through an 18 mesh sieve to break up any undesirably large aggregates and is then transferred to a drying stove at 43 C. for a period of 24-. hours.

The dry powder is finally surface graphited with 1% graphite, sifted and blended according to standard procedure.

Example 2 100 1b. nitrated regenerated cellulose as used in the process of Example 1, and 8 lb. finely ground 2:4 dinitrotoluene are mixed in a rotating copper pan for 5 minutes, and 300 lb. water are added at 25 C. 40 lb. nitroglycerine are added gradually through arose-spray, and mixing is continued for a period of 1 hour.

The subsequent procedure is identical with that described in Example 1.

As stated above, we prefer to use regenerated cellulose sheet of about 0.001 in. thickness, but we could get good results with thicknesses which lie between 0.0005 and 0.01 in. We prefer to break this up into lamellae of a size between 0.0004 and 0.0025 sq. in. but sizes between 0.000025 and 0.0156 sq. in. are also useful provided that the size is chosen in accordance with the thickness of the sheet so that the general lamellar shape is retained. Dust is undesirable and is sieved out from the nitrated product.

The finished grain should not exceed 0.125 in.

in diameter, and we prefer to use grains which will pass through an 18 mesh sieve which has apertures about 0.033 in. square.

. solve nitrocellulose.

same in the accompanying drawing which shows 6 clearly the characteristic form of the same comprising rounded masses including nitroglycerin and aggregations of lamellar fragments of nitrated regenerated cellulose sheet material.

the fact that the illustration represents a mag-" nification of 20 diameters.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

We claim:

1. A process for the manufacture of a doublebase propellent powder that includes the step of agitating comminuted and nitrated regeneratedcellulose sheet material with nitroglycerine in presence of a volatile liquid that does not dis- 2. A double-base propellent powder comprising rounded masses including nitroglycerin and aggregations of lamellar fragments of nitrated regenerated-cellulose sheet material.

3. A double-base propellent powder comprising rounded masses including nitroglycerin and aggregations of lamellar fragments of nitrated regenerated-cellulose sheet material, the said rounded masses being less than 0.125 in. in diameter.

4. A double-base propellent powder comprising rounded masses including nitroglycerin and aggregations of lamellar fragments of nitrated regenerated-cellulose sheet material, the said lamellar fragments having a thickness between 0.0005 and 0.01 inch and a size between 0.000025 and 0.0156 square inch.

5. A double-base propellent powder as claimed in claim 2 in which the size of the lamellae lies 1 between 0.0004 and 0.0025 square inch.

EDWARD WHIIWORTH. THOMAS THOMSON.

The size of these particular grains is indicated by 10

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