US2945751A - Process for making smokeless powder - Google Patents

Description

United States Patent PROCESS FOR MAKING SMOKELESS POWDER John J. ONeill, Jr., Roxana, IlL, assignor to Olin Mathieson Chemical Corporation, a corporation of Virginia N0 Drawing. Filed Feb. 24, 1951, Ser. No. 212,667

Claims. (CI. 52-20) This invention relates to the manufacture of powder and particularly to propellent powder.

In the manufacture of propellent powders it is sometimes desirable in order to modify the characteristics of the powder to incorporate therein finely subdivided water insoluble compounds that are also insoluble in the usual nitrocellulose solvents. The need for such a modifying agent is disposed, for example, by Crawford in. US. Patent 2,440,327, issued April 27, 1948, in which it is pointed out that a dye or carbon black uniformly dis persed throughout the powder grain prevents what is known in the trade as fissures or worm holes resulting from radiant ignition in transparent grains. Bruce and Klein in US. 2,499,295, issued February 28, 1950, disclose a method for incorporating carbon black in powder in which the carbon black is dispersed in a plasticizer for nitrocellulose, this dispersion is then added to a suspension of nitroglycerine and nitrocellulose in water, and after addition of the remaining ingredients, the mass in dewatered and the resulting wet paste dried. The dry material is then colloided in the usual manner by Working on differential speed rolls at relatively high temperature. This method of incorporation, although allegedly securing uniform distribution of the carbon black through the powder, has the disadvantages that it is not always desirable to include such a plasticizer in the powder composition and the method of colloiding by working on rolls is relatively hazardous. Olsen, Tibbitts, and Kerone in US. Patent 2,027,114, issued January 7, 1936, disclose an eflicient relatively safe process of making powder in which nitrocellulose and a solvent for the nitrocellulose are agitated in a non-solvent vehicle containing a protective colloid with subsequent removal of the solvent by vaporization or the like to form the globular powder grains. Insoluble modifiers have been incorporated in the powder grains by merely adding the modifier to the agitated bath, but this method has the disadvantages that a not entirely uniform distribution of the modifier was obtained and a large portion of the modifier would not even enter the powder grain, so that control of the composition of the grain was practically impossible. Attempts have also been made to incorporate such modifiers in powder grains by first dissolving the nitrocellulose in the solvent to form a lacquer, incorporating the modifier and other ingredients therein, and then adding the mixture to the non-solvent with agitation. This method has the disadvantage that appreciable amounts of solvent are necessary to provide a flowable lacquer, making the control of grain size difficult and requiring additional handling equipment.

Such a process of forming powder grains in a nonsolvent dispersion has numerous advantages and it is an object of this invention to provide an improvement thereon permitting the incorporation of such pulverulent insoluble modifiers uniformly throughout the powder grains in controlled amounts. Another object of this invention is to provide an improved process for the 2,945,751 Patented July 19, 1960 incorporation in smokeless powder of a modifier which is relatively insoluble in water and the ordinary nitrocellulose solvents. Still another object is to provide an improved process for the manufacture of powder having the advantages attending the formation of powder grains in aqueous medium and permitting the uniform incorporation in the powder grain of controlled amounts of insoluble modifiers.

In accordance with this invention, these and other objects are accomplished by wetting the insoluble modifier with a volatile solvent for the nitrocellulose before addition of the modifier to a non-solvent bath in which the nitrocellulose and solvent therefor are agitated to form the powder grains. In carrying out the process, the nitrocellulose or smokeless powder base with or without nitroglycerine is usually suspended in a non-solvent vehicle such as water bath by agitation. The pulverulent insoluble modifier is dispersed in a volatile nitrocellulose solvent, i.e. having a boiling temperature less than that of the non-solvent vehicle and relatively immiscible or only partially soluble in the non-solvent vehicle, and the resulting dispersion is then added to the non-solvent vehicle with the agitation being continued until the nitrocellulose is dissolved in the solvent. A protective colloid such as dextrin, starch, gum arabic, or those derived from animal proteins, and the like, is then added to prevent the globules of the so-formed nitrocellulose lacquer emulsion from sticking together or to the side walls of the vessel. When as a result of agitation the globules in the emulsion have attained the desired particle size, the solvent is vaporized to provide the resultant hardened grains of powder. The resultant powder grains contain uniformly dispersed therein substantially the entire amount of such modifier added to the bath. If desired the modifier may be wet with or dispersed in only a portion of the solvent utilized in forming the powder grains, but in any event the insoluble modifier should be thoroughly wet with the solvent prior to its addition to the non-solvent vehicle.

Any desired insoluble modifier, i.e. substantially insoluble in the non-solvent vehicle and nitrocellulose solvent, may be added to the powder, uniformly throughout the powder grains and in controlled amounts in accordance with this process. For example, the powder grains may have thus incorporated therein carbon black to provide the desired opacity and prevent undesirable radiation ignition, or modifiers such as cyclomethylenetrinitramine or even aluminum dust to provide additional energy, or calcium carbonate for increased stability, or powdered iron, iron oxide, red lead, lead chromate, or lead sulphide for controlling the burning characteristics, and the like. The nonsolvent vehicle, variously referred to herein as the non-solvent or the vehicle," should have substantially no solvent power for either the powder base, or the solvent for the nitrocellulose, or the insoluble modifier. Because of its availability and low cost water is preferred as the non-solvent, although any other suitable non-solvent may be employed. Any suitable nitrocellulose solvent substantially insoluble in the non-solvent vehicle and having a boiling temperature below that of the vehicle may be utilized, as for example ethyl acetats, methyl ethyl ketone, or the like. Other soluble ingredients, such as deterrents and the like may be added to the powder in accordance with the usual practice.

In order that the invention may be further clarified following is an example illustrating a typical embodiment of the invention. Two hundred fifty parts of nitrocellulose having a nitrogen content of 12.6% was agitated with 4100 parts of water at about C. to form an aqueous slurry. A suspension of carbon black in ethyl acetate was separately prepared by first thoroughly mixing 0.562 parts of carbon black with 100 parts of ethyl acetate. This mixture of carbon black and ethyl acetate was then added to 1000 parts more of ethyl acetate, and the resultant dilute carbon black-ethyl acetate mixture was agitated to insure uniform distribution of the suspended particles of carbon black. Thirty six and onetenth parts of dinitrotoluene and 2.8 parts of ethyl centralite were then added to the carbon black-ethyl acetate mixture. When the dinitrotoluene and the ethyl centralite were dissolved, the resulting mixture was then added to the nitrocellulose slurry while the slurry was under agitation. The temperature was raised to 68 C. and the complete charge agitated for one hour at which time the nitrocellulose was dissolved. Twenty-five parts of a protective colloid of the type derived from animal protein dispersed in 150 parts of water was then added and the agitation was continued until the nitrocellulose solution was formed into globules of the desired size. One hundred twenty-five parts of sodium sulfate dissolved in 300 parts of water was added over a one hour period and agitation continued for an additional 3 hours. The globules were then hardened to form powder grains by removal of the ethyl acetate during continuous agitation and heating up to about 99 C. in accordance with the practice set forth in U. S. Patent 2,027,114 referred to, hereinbefore. The resultant powder grains were composed of 87.7 nitrocellulose, 11.0% diinitrotolueue, 0.3% carbon black, and 1.0% ethyl centralite, with the carbon black being uniformly dispersed throughout the grains. Substantially the entire amount of carbon black originally added to the agitated slurry was in the powder grains. In those instances, when the carbon black was added without first being wetted with the ethyl acetate only a relatively small fraction of the carbon black added to the slurry appeared in the powder grains and the residual carbon black in the water was lost when the powder was filtered therefrom.

In the following embodiment there is illustrated a method for incorporating an energizing modifier, such as cyclotrimethylenetrinitramine, in the powder grains. To 1000 parts of water at a temperature of about 50 C. was added 75 parts of nitrocellulose having a nitrogen content of 12.3% and the mixture agitated to form a slurry. About 94 parts of cyclotrimethylenetrinitramine was then suspended in about 375 parts of ethyl acetate having dissolved therein about 0.94 part of diphenylamine as a stabilizer and about 19 parts of dibutyl phthalate as a deterrent and the resulting mixture was added to the nitrocellulose-water slurry with agitation and the mixture heated to 68 C. When the nitrocellulose was all dissolved, fifty parts of protective colloid derived from animal protein was then added and the mixture agitated until the resulting globules of nitrocellulose lacquer attained the desired particle size. Twenty-five parts of sodium sulfate dissolved in 50 parts of water were then added. After three hours of agitation the temperature was then gradually raised to about 99 C. to effect removal of the ethyl acetate and harden the powder grains. Upon filtering the powder grains from the aqueous bath, it was found that the cyclotrimethylenetrinitramine was uniformly distributed throughout the nitrocellulose of the grain. The composition was about 50% cyclotrimethylenetrinitramine, about 40% nitrocellulose, about dibutyl phthalate, and about 0.5% diphenylamine.

In still another embodiment, 12.1 parts of nitrocellulose having a nitrogen content of 12.6% were added to 430 parts of water and the mixture was agitated and heated to a temperature of 50 C. In a separate vessel, 68.8 parts of crystalline cyclotrimethylenetrinitramine were suspended in 137.5 parts of ethyl acetate having dissolved therein 0.086 part of diphenylamine. The suspension of the cyclotrimethylenetrinitramine in the ethyl acetate was then added to the water bath of nitrocellulose and the mixture heated to 65 C. with continued agitation. After about 1 /2 hours, at which time the nitrocellulose was all in solution and the cyclotrimethylenetrinitramine was uniformly distributed through the nitrocellulose solution, 2.2 parts of protective colloid derived from animal protein dispersed in 30 parts of water was then added to the agitated nitrocellulose solution. After approximately /4 of an hour of continued agitation, the globules of nitrocellulose solution had attained the desired size and 12.5 parts of sodium sulphate dissolved in 30 parts of Water was slowly added to the mixture which was then agitated for about 5% hours. When the. sodium sulphate is added an osmotic action takes place tending to remove any water dissolved in the globules of nitrocellulose solution and thus, the final density of the powder grain is increased. If no sodium sulphate, or equivalent material, is utilized, the powder grains tend to have a greater porosity. The bath was then heated to raise the temperature slowly to about 99 C. to drive oil the solvent and harden the globules into powder grains. The hardened powder analyzed about cyclotrimethylenetrinitramine, about 20% nitrocellulose, and about 0.1% diphenylamine. The crystals of cyclotrimethylenetrinitramine were substantially uniformly dispersed throughout the nitrocellulose of each grain.

In each of the above examples the pulverulent insoluble modifier had a particle size substantially less than that passing through a standard 100 mesh U. S. sieve. Although insoluble modifiers having substantially greater particle size may be incorporated in the powder grains in accordance with this process, it is preferred that the particle size be such as to pass through a standard U.S. 100 mesh sieve. The powder base may be fibrous or colloided nitrocellulose, and may include nitroglycerine or other ingredients, and any base suitable for smokeless powder may be utilized.

From the foregoing specific examples it will thus be apparent that widely divergent amounts of pulverulent insoluble modifiers may be uniformly dispersed in powder grains and in controlled amounts in accordance with this invention and the desired objects and advantages are thereby attained. While the foregoing embodiments have been set forth in detail, it is to be distinctly understood that many modifications and variations will naturally present themselves to those skilled in the art without departing from the spirit of this invention or the scope of the appended claims.

Having thus described the invention, what I claim and desire to secure by Letters Patent is:

1. In the art of makingpowder by a process in which a smokeless powder base dissolved in a solvent therefor is agitated in a non-solvent vehicle containing a protective colloid and the solvent is subsequently removed to yield hardened powder grains, the step of incorporating therein a pulverulent modifier insoluble in said solvent and vehicle which comprises first wetting said insoluble modifier with a solvent for the smokeless powder base which has a boiling point less than that of the vehicle, and then introducing said wet insoluble modifier into said vehicle.

2. In the art of making powder by a process in which a smokeless powder base dissolved in a solvent therefor is agitated in a water bath containing a protective colloid and the solvent is subsequently removed to yield hardened powder grains, the step which comprises introducing into said water bath a pulverulent modifier insoluble in but wet with a solvent for said smokeless powder base which has a boiling point less than that of water.

3. The process of claim 1 wherein said modifier is carbon black.

4. The process of claim 1 wherein said modifier is cyclotrimethylenetrinitramine.

5. The process of claim 1 wherein said nonsolvent vehicle contains sodium sulfate.

References Cited in the file of this patent UNITED STATES PATENTS 6 OTHER REFERENCES Davis: The Chemistry of Powder and Explosives," vol. II, published in NY. (1943), by John Wiley and Tibbitts et July 1934 Sons, Inc., London, Chapman and Hall, Ltd., pages 327, 015M! et a1. 9, 5 and Olsen Aug'11'1942 Hackh's Chemical Dictionary (Grant, 3rd edition), Herwg 5, 1946 pub. 1944, by the Blakiston 00., Philadelphia, Toronto BI'HCQ et a]. Feb. 28, 1950 (reprinted 1950), page 653.

Attesting Oficer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 25945351 July 19 1960 John J. O"Neil1 Jr.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring o orrection and that the said Letters Patent should read as corrected below.

Column l line 22 for "disposed" read disc losed column 3 line 27, for "87.7 read M 87.7% l1ne 73 for "part" read parts Signed and sealed this 3rd day of January 1961,

(SEAL) Atteet:

A AXLINE ROBERT C. WATSON Commissioner of P 81161118

Claims (1)

1. IN THE ART OF MAKING POWDER BY A PROCESS IN WHICH A SMOKELESS POWDER BASE DISSOLVED IN A SOLVENT THEREFOR IS AGITATED IN A NON-SOLVENT VEHICLE CONTAINING A PROTECTIVE COLLOID AND THE SOLVENT IS SUBSEQUENTLY REMOVED TO YIELD HARDENED POWDER GRAINS, THE STEP OF INCORPORATING THEREIN A PULVERULENT MODIFIER INSOLUBLE IN SAID SOLVENT AND VEHICLE WHICH COMPRISES FIRST WETTING SAID INSOLUBLE MODIFIER WITH A SOLVENT FOR THE SMOKELESS POWDER BASE WHICH HAS A BOILING POINT LESS THAN THAT OF THE VEHICLE, AND THEN INTRODUCING SAID WET INSOLUBLE MODIFIER INTO SAID VEHICLE.