US2213255A - Explosive - Google Patents

Description

Patented'sept 3, 1940 earner or ies EXPLOSIVE Fredrich Olsen, Gordon 0. Tibbitts, and Edward B. W. Kerone, Alton, Ill., assignors to Western Cartridge Company, East Alton, 111., a corporation of Delaware No Drawing. Application January 6, 1936,

Serial No. 57,662

\ 19 Claims.

This invention relates generally to the manufacture of smokeless powder and particularly to the production of smokeless powder in the form of relatively small grains of substantially spherical shape. As to common subject matter this application is a continuation of our copending application Serial No. 598,332, filed March 12, 1932, Patent Number 2,027,114, patented January 7, 1936.

The object of the present invention, generally stated, is to provide a process of manufacturing smokeless powder in the form of generally spherical grains and suitable for use as a propellant for various military or sporting weapons and particularly adapted for use in shotguns and other small arms ammunition.

Another object of the invention is'to provide a powder grain of the type referred to and a process of manufacturing the same whereby 20 the ballistic properties of the grain may be controlled with facility.

Another object of this invention is to pro vide a propellant powder grain of generally spherical form having an interior of controlled porosity and a substantially impervious exterior.

A more specific object of the invention isto provide a process of making propellant powder grains in which globules of a dissolved smokeless powder, base containing water are dispersed in a medium which is a non-solvent for the smokeless-powder base and hardened while maintained in disper- SlOl'l.

Other objects will become apparent to those skilled in the art when the following description,

is read.

In accordance with the present invention, generally stated, a lacquer may be made by disso1v-. ing a smokeless powderbase in a solvent. -The lacquer thus formed is suspended in a medium 40 which is a non-solvent for the powder base and substantially a non-solvent for the solvent. selected for the powder base. With the lacquer thus suspended in the non-solventmedium, agi-. tation and other conditions are controlled so as to produce globules of the lacquer which are substantially spherical in form. While this condition of the dispersed globules is maintained, the solvent for the powder base is vaporized from the globules so as to harden them intograins of generally spherical form.. The size of the resulting grains may, therefore, be controlled by controlling the size of the globules of lacquer. Various factors aiiect the size of the globules, as for instance, the more vigorous the agitation of the bath containing the lacquer the smaller will be ,suitable protective colloids smokeless powder bases.

the globules distributed; the higher the viscosity of the lacquer, the larger the globules; and and emulsifying agents may be employed for further controlling the size of the distributed globules.

The smokeless powder base employed in accordance with the present invention may be nitrocellulose of any suitable type, nitro-starch, or a mixture of nitrocellulose and nitroglycerine and/or deterrents, as well as other suitable 5 The process of. the present invention lends itself to the treatment of a variety of substances as the smokeless powder base; For instance, when nitrocellulose is employed it need not be highly purified but in fact may be freshly nitrated cellulose which has not gone through all the usual stages of purifica-'- tion. Moreover, deteriorated cannon powder; containing centers of high acidity maybe re-. worked in accordance with the present invention. If a double base powder is desired thedeteriorated cannon powder may be one containing nitrocellulose and .nitroglycerine such, for instance, as Ballistite. 1

The medium in which the lacquer is to be sus-' 25- pended is, of course, selected in accordance with the solvent which has been chosen, it beingimportant to select a non-solvent medium which is relatively insoluble with the solvent, but yet the medium should be one with which .the s01- 1 vent selected can be emulsified'or dispersed in the form of globules without too much difficulty. As a general rule, and from the economical standpoint, water is the preferable non-solvent medium to use.

As just pointed out, the solvent selected must be one which is substantially insoluble in the nonsolvent vehicle to be employed, but one whose solution of the powder base may be dispersed as globules by agitation in the non-solvent medium,

and the dispersion controlled. When water is employed as the non-solvent medium, ethyl acetate, isopropyl acetate, butyl acetate, or methyl isobutyl ketone may be employed with advantage.

If,'however, a non-solvent medium other than water is employed, such as glycerine, acetone may be used as the solvent.

The selection of a solvent will, of course, also be governed by the smokeless powder base employed, it being advantageous, in the interest of safety, when a nitrocellulose-nitroglycerine powder is employed to use a solvent having a low boiling point. Hence in the treatment of double base powders or in powders in which nitroglycerine is incorporated during the process, ethyl ace- Q5 probably, however, due to the fact that the interfacial tension between the lacquer and the water is higher and the mutual solubility of the solvent with water is usually lower in the solvents having higher boiling points than ethyl acetate.

Solvents having the higher boiling points have an advantage over the lower boiling point sol-' vents when it is desired to make very dense grains without porous interiors. This is possibly due to the fact that solutions of nitrocellulose in such solvents have less tendency to emulsify water within the lacquer and hence the globules have less water within them during the hardening stages than those made with the lower boiling solvents, so that the hardened grains are less porous.

The process of the present invention lends itself to the production of powder grains having a variety of ballistic properties. For instance, if it is desired to produce a double base powder from a single base deteriorated cannon powder, the desired amount of nitroglycerine may be introduced into the lacquer formed, by the action of the selected solvent upon the nitrocellulose cannon powder.

a in order to incorporate accelerators, deterrents,

stabilizers, etc. 'in powder grains manufactured in accordance with the present invention, the material to be incorporated may be first dissolved in the solvent,'a'nd the nitrocellulose .subsequently introduced, or the desired amount of'the incorporated material may be introduced directly into the nitrocellulose lacquer and thoroughly distributed therein, or 'suitable agents may be dispersed in the vehicle and be sorbed by the powder grains.

I According to one embodiment of the present invention a nitrocellulose lacquer may be agitated with a quantity of water so as to emulsify some of the water within the nitrocellulose lacquer.

- Thereafter this emulsion 'of water in nitrocellulose lacquer may bedispersed in the form of globules in an excess of water and while thus dispersed the temperature of the bath elevated to a point such..to accomplish distillation of the solvent from the dispersed globules and also to effect removal of some or all of the water from the dispersedglobules of emulsion. The grains-resulting from the process of this embodiment are, therefore, spherically shaped with a substantially impervious and hard exterior but the interiors of the grains may be somewhat porous depending on the amount of the water present in the globule. By thus controlling the amount of water which is emulsified in the nitrocellulose and the amount of water which is present in each globule of lacquer; the degree of porosity of the interior of the individual grain may thus be varied and controlled, and hence the gravimetric density of the powder may be controlled.

. As a more specific illustration of the process Likewise, suitable deterrents, such as. DNT, diamyl or dibutyl phthalate may be intro-" of the present invention, deteriorated nitrocellulose cannon powder will be taken as the illustrative smokeless powder base; water will be taken as the non-solvent vehicle, and isopropyl acetate will'be taken as the illustrative solvent. The cannon powder may be used as such or may be ground to a fineness such as to facilitate treatment, as for instance, eight to twenty mesh or finer.

For example, 37.5 pounds of ground cannon powder may be mixed with 350 pounds of water and agitated in a suitable still so as to thoroughly distribute the particles of cannon powder throughout the water. In order to neutralize any acid which may diffuse from the particles of cannon powder into the water, a small quantity, such as 0.375 pound of a neutralizer, such as calcium carbonate may be added.

While agitation of this mixture is continued the solvent may be introduced. 244 pounds of isopropyl acetate which may contain, for instance 1.88 pounds of DNT and a small quantity of diphenylamine, such as 0.28 pound may be added to the mixture in the still in as short a period of time as possible, agitation continuing at a rate sufiicient to keep the particles of cannon powder suspended in the water in the still.

' After the solvent has been added to the mixture in the still, the temperature of the still may be elevated to about 50 C. and held at that temperature with agitation continuing until the solvent has dissolved the nitrocellulose and formed a lacquer. Due to the agitation which has continued-during this solution period, some water will have been emulsified in the nitrocellulose lacquer.

Agitation may now be interrupted and the mixture allowed to stand quiescent for a period sufiicient to permit the nitrocellulose lacquer to coalesce into one mass of emulsion (water in nitrocellulose lacquer), separating from the excess of water.

During the period of coalescing the temperature of the .mass may be held substantially constant, that is to say, at or about 50 C.

' After the lacquer has coalesced, agitation may be resumed. and a suitable protective colloid,

such as gum arabic may be added. For instance,

a solution of 14.- pounds of gum arabic in poundsof water made at 75 C.- may be added to the contents of the still as agitation is resumed. The temperature of the mixture in the still may now be elevated as rapidly as possible to just below the boiling point of the mixture of solvent and non-solvent vehicle. In the case of isopropyl acetate which in mixture with water boils at about 74 C., the temperature may be elevated to 73 C. plus or minus 0.5 degree. After this temperature of just below the boiling point of mixture of solvent and nonsolvent is attained, the mixture may be agitated more vigorously as,

,for instance with one type of agitator the speed may be increased from 800 R. P. M. to 1200 R. P. M. (it being understood that the particular speedof agitation will depend upon the type of agitator employed). Thus during the period of more vigorous agitation, after the temperature of just below the boiling point of the mixture has been reached, the lacquer is being broken up into globules of the desired size, and dispersed in the water.

, In this manner the lacquer is broken up into the desired size of globules at about the same temperature as that which will be attained during the initial hardening of the grains so that there will be no substantial change of viscosity of the' globules because of temperature changes until the globules have assumed the desired shape.

After the vigorous agitation has proceeded at the temperature just below the boiling point of the mixture for a time sufficient to break up the lacquer into globules of the desired size, the speed of agitation may be reduced to a point just sufficient to maintain the globules suspended in the bath without formation of a crust on the surface of the still charge but not so high as to effect a distortion of shape of the globules.

At this time, if it is desired to remove the water from the interior of the globules in a manner so as to control the porosity of the resultant grains, a suitable amount of a solute; such as potassium nitrate, sodium sulphate, barium nitrate, or the like, may be added to the water in the still (the amount depending upon the porosity desired) as described and claimed inthe copending application of Harold F. Schaefer, Serial No. 57,763, filed January 6, 1936, Patent Number 2,160,626, patented May 30, 1939. For example 4 pounds of barium nitrate dissolved in a small quantity of water may be added. While the temperature is still held just below the boiling point of themixture, agitation'continues at a speed such as to maintain the hardening globules in suspensionv but not so high as to move the globules in the bath at a speed such as to render them unshapely.

In the case of the agitator in which the speed of 1200 R. P. M. is employed for breaking up the lacquer, as just described, the speed may be reduced to 850 R. P. M. Agitation continuesfor a period sufficient to accomplish mild evaporation of the solvent from the surfaces of the globules thus to preliminarilyshape them.

Thereafter and while the temperature is maintained at just below the boiling point of the mixture, the speed of agitation may be further reduced as the surfaces of the grains are now sufficiently hardened that the tendency to stick together will be minimized. Altogether a period of five to six hours at a temperature just below the boiling point of the mixture will harden the grains to an extent sufficient to prevent them from from bursting when subjected to a higher temperature.

The temperature of the bath may now be gradually elevated to about C. (in the case of isopropyl acetate) over a period of about .three The final temperature and the period hours. over which it is gradually reached will, of course, depend upon the solvent selected but the distillation-is continued for a period of sufficient duration and at a temperature sufiiciently high to remove substantially all of the solvent. and the desired amount of the water from the interior of the globules.

.Thus, while there is some evaporation of solvent during the graining and shaping stages While the temperature is just below the boiling point of the mixture, the solvent is not evaporated with rapidity until after the globules have been sized, shaped and preliminarily hardened. The temperatures and periods of treatment will of course vary with the solvents employed; higher temperatures being possible, the higher the boiling point of the solvents. Thus, when ethyl acetate is used, the temperature during the graining and shaping stages may be just below 68 C. (the boiling point of the initial mixture), while after methyl isobutyl ketone.

butyl acetate, the graining and shaping stages may be carried out at a temperature just below 93 C. (boiling point of initial mixture), but since butyl'acetate boils at a temperature of C.

the water vaporizes more rapidly than the solvent and the additionof extra water to the still may be necessary before all the solvent is vaporized. This may prolong the time required for carrying out the process with such a'solvent. Likewise with methyl isobutyl' ketone whose boiling point is 116-119" C. but the initial mixture thereof in water may be such as to boil at about 95 C.

After the distillation has continued for a time sufficient to remove substantially all, or the desired amount, of solvent from the globules, the charge in the still may be cooled to about 50 C. after which the contents of the still isdumped and the excess liquor drained from the grains.

Instead of forming the lacquer of smokeless powder base and solvent in the presence of the non-solvent vehicle, such as water, as has been described hereinbefore, it will be understood that the lacquer may be formed by mixture of the .solvent with the smokeless powder base before they are introduced into the presence of the nonsolvent vehicle. I, In other words, the procedure referred to in our copending application Serial No. 598,332 under theheading Solution of Laoquer Process may be carried out with solvents, such as isopropyl acetate, butyl acetate, and Likewise, these solvents may be employed in the procedure described under the heading Large base particle process described in said copending application.

l After the powder grains resulting from the process of the present invention are dumped from the still and, either before or after they are dried,

they may be subjected to a surface treatment with a desired modifier, such for instance, as an accelerator or a deterrent or both. The powder grains resulting from the process of the'present invention lend themselves particularly to surface treatment with combustion modifying agents in view of the fact that the surfaces of the grains are smooth and devoid of projections upon which a surface treating-agent might otherwise concentrate. Hence the smooth and rounded surfaces of the grains resulting from the present invention may be surface treated so as toaccomplish a .uniform coating and uniform impregnation by the surface treating agent so that the burning rate is substantially uniform over the entire surface of. the grain.

While it will be understood that the powder grains of'the present invention may be surface treated in accordance with any desiredprocess, the surface treatment may. be advantageously carried out as follows: One part of powder grains (by weight) may be suspended in four to five to about 40 C. A priming emulsion may then be introduced. Such priming emulsion may be a water emulsion containing three parts of isopropyl acetate to two parts of benzol in twice its volume of water. In order to obtain an effective emulsion suitable emulsifying agents may be employed such for instance as about 0.02% of Turkey red oil. The amount of this emulsion added to the slurry of powder grains may be such as to introduce an amount of isopropyl acetate and 'benzol equivalent to 5-20% ofthe weight of the powder grains. This emulsion primes the surface of the powder grains for the subsequent application of the surface treating agent. Then while the surfaces of the powder grains remain soft the surface treating agent may be introduced in the 0.2% of gum arabic.

If it is desired to coat the powder with both an,

accelerator and a deterrent, a suitable deterrent, such as dinitrotoluene, dibutyl phthalate or the like; may be introduced into the nitroglycerinetoluene solution so that the deterrent and the accelerator will be deposited concurrently upon the surfaces of the grains.

As a further example the coating may be accomplished by suspending the powder in four times its weight of water and the water heated to a temperature of 45 to55 C. The coating agent may be any desired combustion modifier, ei-

ther an accelerator or deterrent, or both. A solution of the coating agent or agents in a mixture of benzol and alcohol is prepared such that it contains the proper quantities of the components. As an example, a solution of 25% nitroglycerine, 25% benzol and 50% alcohol may be used. Sufficient of this solution is weighed out so that the proper quantity of nitroglycerine desired, based on the weight of the powder, will be had. In this solution is dissolved that quantity of deterrent desired. This alcohol-benzol solution is then added to the water-powder mixture which is being agitated at such a rate as to prevent agglomeration of the grains. The alcohol is dissolved out of the benzol-nitroglycerine solution by the water, leaving the nitroglycerine in solution in the benzol together with the deterrent in fine droplets. These droplets attack the powder grains and coat the surface thereof. The temperature is then raised to about 65 C. and held for a period sufiicient to accomplish the desired penetration, as for instance, about 45 minaccelerator such as nitroglycerine over a deterrent coated powder of any type where the deterrent employed has been such as to reduce the ignitability of the powder. Moreover, even if the nitroglycerine is applied first, good ignitability will be maintained when a deterrent is deposited over the nitroglycerine coating.

As previously described, the powder produced is not only substantially spherical in shape but of uniform density; It, therefore, has advantages not only from a ballistic standpoint, but also from a loading standpoint. Spherical grains of the same size and composition burn at the same rates. Accordingly, by screening grains closely the same size can be secured. This is impossible with angular or oblong grains which, on account process comprising,

of their varying shapes have different volumes, even though all may pass through the same screen opening. In accordance with this invention there is produced, therefore, a. powder teristics can, therefore, be accurately controlled;

for packing in a cartridge is not a matter of chance as with flaky or angular grains where the weight per volume depends upon the arrangement of the grains in the charge, Spherical grains also flow easily.

While in the foregoing description severalpractical examples of the process of the present invention have been given, it is to be understood that the invention is not limited to the detail of practical examples given, but that it is of gene'ral application, and hence it is to be understood that various changes may be made in the details and various combinations and sub-combinations of features used without departing from the spirit of this invention; Such modifications are, although not specifically described herein, contemplated by and within the scope of the ap pended claims.

Having thus described the invention, what is claimed is:

1. A propellant powder grain composed of homogeneous smokeless powder base gelatinized throughout, said grain having a porous interior and a substantially impervious exterior surface layer.

2. A propellant powder grain composed of a solidified droplet of gelatinized smokeless powder base having a porous interior and a substantially impervious exterior said grain being gelatinized throughout.

3. A propellant powder grain composed of a solidified droplet of gelatizined nitrocellulose and nitroglycerine said grain being gelatinized throughout.

4. A propellant powder grain composed of homogeneous smokeless powder base gelatinized throughout, said grain having a porous interior and a substantially impervious exterior surface layer coated with a deterrent and an accelerator.

5. In the art of making smokeless powder,

' the process comprising, forming a solution of a smokeless powder base in a solvent, suspending the solution in the form of globules in a vehicle having a lower boiling point than the solvent, said solvent and said vehicle being substantially mutually insoluble and extracting the solvent from the globules.

6. In the art of making smokeless powder, the forming a solution of a smokeless powder base in a solvent which is substantially insoluble with'water, emulsifying water into the solution, agitating the emulsion with an excess of water to disperse globules of the emulsion in the water, and solidifying the globules whilethe dispersion is maintained.

7. In the art of making smokeless powder, the process comprising, forming a solution of a smokeless powder base in a solvent which is-substantially insoluble with water, emulsifying water into the solution, agitatingthe emulsion with an excess of water to disperse globules of the emulsion inthe water, and vaporizing the solvent from the globules of emulsion while the dispersion is maintained.

8. In the art of making smokeless powder, the process comprising, forming a solution of a smokeless powder base in a solvent, suspending the solution in the form of globules in a vehicle having a lower boiling point than the solvent, said solvent and said vehicle being substantially mutually insoluble and vaporizing the solvent from the globules at a temperature below the boiling point of the solvent.

9. In the art of making smokeless powder, the process comprising, forming a solution of a smokeless powder base in a solvent, suspending the solution in the form of globules in a vehicle having a lower boiling point than the solvent, said solvent and vehicle being substantially mutually insoluble, and extracting the solvent from the globules.

10. In the art of making smokeless powder, the process comprising, forming a solution of nitrocellulose and nitroglycerine in a solvent therefor, dispersing the solution in the form of globules in an excess of a bath, the vehicle of said bath being substantially insoluble with said solvent and being a non-solvent for nitrocellulose and nitroglycerine, and solidifying the globules while the dispersion is maintained.

11. In the art of making smokeless powder, the process comprising, forming a solution of nitrocellulose and nitroglycerine in a solvent therefor, dispersing the solution in the form of globules in an excess of a bath, the vehicle of said bath being substantially insoluble with said solvent and being a non-solvent for nitrocellu-- lose and nitroglycerine, and vaporizing the solvent from said globules while the dispersion is maintained.

12. In the art of making smokeless powder, the process comprising, forming a solution of nitrocellulose, nitroglycerine and a deterrent in a solvent therefor, dispersing the solution in the form of globules in an excess of a bath, the vehicle of said bath being substantially insoluble with said solvent, and being a non-solvent for nitrocellulose, nitroglycerine and deterrent, and vaporizing the solvent from the dispersed globules.

13. In the art of makingsmokeless powder, the process comprising, forming a solution of nitrocellulose and nitroglycerlne in a solvent therefor, dispersing the solution in the form of globules in an excess of a bath, the vehicle of 55 said bath being substantially insoluble with said 14. In the art of making explosives, the proc ess comprising, suspending formed propellant powder grains in a non-solvent bath, and treating the suspensionwith a solution of combustion modifier in a composite solvent containing an ingredient which is insoluble and another ingredient which is substantially soluble in said non-solvent bath.

15. In the art of making explosives, the process comprising, agitating a smokeless powder base in water with isopropyi acetate to an extent sufiicient to dissolve the base and to form globules of the dissolved base, and removing the isopropyl acetate from the globules.

16. A propellant powder grain composed of homogeneous smokeless powder gelatinized throughout, said grain having a porous interior and an impervious surface layer, said grain being spherically shaped, and coated with a combustion modifier.

17. In the art of making explosives, the process comprising, agitating a smokeless powder base in water with butyl acetate to an extent suflicient to dissolve the base and to form globules of the dissolved base, and removing butyl acetate from the globules.

18. In the art of making explosives, the process comprising, agitating a smokeless powder base in water with methyl isobutyl ketone to an extent sufficient to dissolve the base and to form globules ofthe dissolved base, and removing methyl isobutyl ketone from the globules.

19. In the art of making smokeless powder,

'the process comprising, forming a. solution of a smokeless powder base in a solvent; suspending the solution in the form of 'globules in a vehicle having a lower boiling point than the solvent, said solventand said vehicle being substantially mutually insoluble, extracting the solvent from the globules to form grains, treating the resultant grains with a volatile solvent to an extent suflicient to soften the surfaces of the grain, and, while the surfaces remain soft, depositing a nonvolatile combustion modifier upon the grain.

' FREDRICH OLSEN.

GORDON C. TIBBI'IIS., EDWARD B. W. KERONE.