US2425854A

US2425854A - Propellent powder

Info

Publication number: US2425854A
Application number: US495536A
Authority: US
Inventors: Harvey B Alexander
Original assignee: Hercules Powder Co
Current assignee: Hercules Powder Co
Priority date: 1943-07-20
Filing date: 1943-07-20
Publication date: 1947-08-19
Anticipated expiration: 1964-08-19

Description

iatente cl Aug. 19 1947 v UNITED STATS PROPELLENT POWDER Harvey B. Alexander, Kenvil, N. J., assignor to p p I Hercules Powder Company, Wilmington, Del., a corporation of Delaware a a No Drawing- Application Ji1ly'20,1943, I Serial,No.495,536" i i 1 18 Claims. (c1.52-13 This invention relates to an improved promanufactured but have not met withsuccessgbe pellent powder and more particularly to a procause no explosive ingredient of high energy congressive-burning propellent powder of high entent has been incorporated into nitrocellulose or ergy content. r nitrocellulose/nitroglycerin powders in a man- In the prior art, thereiare various known pro.- .5 ner', thatwould give even burning characteristics. pellent powders, the most important types being For example, the detonating compositions such single-base or nitrocellulose powders and doubleas mercury fulminate or lead azide, when inbase or nitrocellulose/nitroglycerin powders. cluded in powders, develop sudden high peak These powders, while providing desirable ballistics pressures and therefore do not give desirable in most rifles, in certain cases do not provide suffiballistics. The use of various high energy concient propellent force of arapidly accelerating tent explosives such as nitrostarch, PETN, hexcharacter to give the projectile being fired from ogen, and the like, have never met with complete the rifle a desired high velocity. With the mod- 7 success because when they are incorporated into ern military and sporting rifle construction, it progressive-burning powders they form local hot should be possible to provide a propellent that 15 spots within the powder that cause dangerous will impart a high velocity to a bullet when it peak pressures and give erratic ballistics. All of leaves the gun barrel. In order to impart such the above type added ingredients are capable of velocity, it is necessary to use a propellent charge increasing or accelerating the rate of combustion with a relatively, high energy content, but when 7 of the singleor double-base powders but the inprior art powders of this type are used, certain crease'ofacceleration cannot be controlled. Furinherent disadvantages are encountered,such as, ther; it is difficult tolmodify the powder rains difliculty in causing the initial inertia force of the. containing such. materials so that their initial bullet to be overcome before an extremely high .combustion rate is sufilciently low to overcome pressure is developed by the burning of the 'po'winertia force and is also capable of impartin ders. Velocity thereafter to the bullet without develop- The single-base powders, uncoated and modimerit of excessive pressure which may-cause rupfied, have given progressive-burning charges ture of breech mechanisms or of the barrel'itselfo which are satisfactory for most uses of low veloc- Research programs have been carried out; in

ity bullets. Upon demand of higher velocities, 7 a te p to p p p tp wde s w ich the potential of the nitrocellulose powder was in- W ldt d v p' x ive pressures p n i n creased by adding thereto more powerful explotion .-but. would. immediately thereafterhave such' sive substances, for example, an explosive nitric an increased and accelerated bu spe ditha't. ester, such as, nitroglycerin. The nitroglycerin/ the "bullet, velocity would be substantiallyinnitrocellulose double-base powders are satisfacvc d- In most d v l pment workQtheprotory when they are so deterred by surface coatcedule has been an attempt tO-mOdifY lihesurfac'e ing that their original burning speed is suffiof high ener y Content p s n ord r-to limit ciently slow to overcome the initial inertia, force the'initial combustion ratewithout'iretard'ing the of the bullet, impart velocity to the projectile, Subsequent acceleration. WB IT mOGi YiI-I Q and thereafter increase in speed of burning and ,agents have Ot'b'een foundivihich-iareisatisfacimpart an accelerating effect on the projectile. 40 'Y; because, if'sufficient y t fip- The double-base nitrocellulose/nitroglycerin plied t0 eisurface to obtain limited initial con'ri powders ar limited as t energy cont nt beca s bustion desired, ignition is sozdiflicult that either powder grains which contain more than about g s a d misfiresresu t; 0 h powdcrlf nitroglycerin become sticky and are diflito comp e y-burn; before the bulletjlisexpelled cult to load. The initial ignition and pressure from the barrel- 1 1 are difficult to control, and further, such high .Now,.in accordance with this invention; itshas nitroglycerin content powders upon hot storage been discovered that a high ,energycontentrpow-g. tend to desensitize primers. It is also difficult to der can be made from either single-base 'illil'LIfOrj. coat sticky powders with a deterrent. 7 cellulose powders or double-base nitrocelluloseL Other high energy content powders have been nitroglycerin powders, either uncoated or medi fied, which will give an acceleration rate after initial ignition that will produce the high velocities desired. To obtain this high energy content powder having this very desirable characteristic, various normal singleand double-base powders have been altered by the uniform incorporation therein of excessively fine discrete particles of solid explosives.

In more detail, the invention provides a progressiVe-burning smokeless powder which has incorporated in the grain structure a secondary solid explosive which is incompletely soluble and, therefore, not fully dissolved in any ingredient contained in the powder or used during its manufacture. The explosive, in the form of discrete particles, is incorporated in the colloided singleor double-base powder and is uniformly distributed throughout. These discrete particles are of a screen size corresponding to a United States Standard Sieve No. 200, for example, about 74 microns, and the solid explosives which are incorporated in the smokeless powder are capable of reduction to particle having a diameter not in 4 The powders of Examples 1 through 4 were prepared by colloiding compositions in accordance with the following formulation and then properly granulating:

Per cent by Weight Nitrocellulose (13.20-13.24% N) 48.25 Nitroglycerin 20.00

Solid explosive material (where indicated) 30.00 Diphenylamine 0.75 Potassium sulfate 1.00

The powders of Examples 5 and 6 were prepared by colloiding compositions in accordance with the following formulation and then properly granulating Per cent by weight Comparison of ballistics of uncoated double-base powders containing coarse or fine solid explosive materials as an added. ingredient Charge Mean Mean Granulation diam- Example N 0. Powder Added Ingredlent Grains Velocity, Pressure, eter X length ft./sec. lb./sq. in. in inches A Fine PEIN 43. 2 2, 777 51, 800 053. 015 X l/ll 1 B Coarse PETN 35.4 2,691 52, 400 .053. 015 X l/ll C None 43.8 2.703 51,500 047-.015 X l/ll 2 D Fine tetryl 49. 3 2, 855 52, 100 053- 015 X 1/11 E Coarse tetryl 45.0 2, 781 52,700 053-.015 X l/ll 3 F Fine TN1 56. 0, 2, 439 40,000 045-.015 X l/ll G Coarse TNT 59.8 2,397 40,100 045 015 X 1/11 H Fine PETN. 44.8 3, 071 I 51, 900 053- 015 X l/ll 4 I Coarse PEIN 40.0 2,996 52,000 053-.015 X 1/11 .1 None 42-7 2,941 52, 000 .047. 015 X l/ll Bullets Used: .30-06 Springfield-AP M2. Frankford Arsenal Components; Winchester .348-Winchestcr 200 gr. soft point, Winchester Components; Winchester .270-Winchester pointed soft point, WinchesterOomponents.

Powder A, B, O, D, and ETested in .30-06 Springfield.

Powder F and G-Tested in Winchester .34

Powder H, I, and ITested in Winchester .270. Ten shot tests-Exception Powder I, 8 shots.

andwillpreferably pass a United States. Standard Sieve No. 325.

Bythe incorporation of such discrete. particles, it has been found possible to. produce propellent charges for cartridges, used: in military or sporting rifles which will impart a much higher muzzle velocity to. the projectile than known powders will produce under the limitations fixed by the strength of the gun, both barrel and breech, and the, space which isprovided in the cartridge case for the propellent; charge.

In order to illustrate. the performance, desirable, properties and: ballistics 'of the highv energy content powders of this invention, Examples 1 through 6 are presented in tabular form. Table I shows a comparison of ballistics of uncoated double-base powders containing coarse 'or fine solid explosive materials, where indicated, as an added ingredient. Table I-A shows screen tests on the ingredients used. Table II shows-a comparis'on of ballistics of uncoated single-basepowders containing coarse or fine solid explosive materials as an added ingredient. Table II-A shows screen tests on the ingredients used.

D-Fine tetryl:

By microscopic examination through 325 mesh screen.

E-Coarse tetryl: 7 Per cent On 30 mesh screen 4.9 On 50' mesh screen 20.9v On 100' meshfscreen 31.1 On mesh screen 9.4: Through-140 mesh screen 33.7

1 U. S. Standard Sieve series.

With reference to Table I, Example 1 affords a comparison of powders containing fine PETN, coarse PETN, and a similar uncoated, doublebase powder containing no added explosive ingredients. When tested in a .30-06 Springfield at comparative pressures the powder containing the finely divided PETN gave a higher velocity than the powder containing coarse PETN. Also, the powder with the higher energy content (fine PETN- added) gave a higher velocit for about the same charge weight than the powder containing no added ingredient. Example 2 shows that, in a .30-06 Springfield, a powder containing fine tetryl has a higher velocity with a comparative pressure than one made with coarse tetryl. Example 3 gives a comparison between powders made with fine and coarse TNT in a. .348 cal. Winchester. It will be noted that the powder containing the finely-divided TNT gave better results than the powder containing the coarse TNT. Example 4 is a comparison of the same type powders given in the first example but tested in a .270 cal. Winchester. The powder containing the finely-divided PETN was more progressive burning than the powder containing coarse PETN. For approximately the same charge weights, the powder containin finely-divided PETN gave a higher velocity than the powder containing no added explosive material.

With reference to Table I-A it will be seen that allthe finely-divided solid explosive materials have the major portion thereof capable of passing through a United States standard sieve N o. 200.

TABLE II S M-Fine tetryl:

By microscopic examination-400% through 325 mesh screen.

N-Coarse tetryl: Per cent On 30 mesh screen 4.9 On mesh screen 20.9 On 100 mesh screen 31.1 On 140 mesh screen 9.4 Through 140 mesh screen 33.7

1 U. S. Standard'Sieve series.

With reference to Table II, the powder of Example 5 containing fine PETN gave a higher velocity than did the powder containing coarse PETN. The powders had comparable pressures and approximately the same charge weight. Example 6 clearly demonstrates the effect of using fine and coarse tetryl. The powder made with finely-divided tetryl was very slow burning and the desired pressure of 52000 lbs./ sq. in. could not be reached. However, a velocity of 2411 ft./sec. was obtained. The powder made with coarse tetryl was very fast burning. A charge of 16.9 grains gave a low velocity of 1524 ft./sec. with the desired pressure of 52000 lbs/sq. in. Although the two ballistic tests are not comparable because of the differences in charge weights and pressure levels, the advantages of the present invention are clearly shown, that is, that the powders containing finely-divided material give more progressiveness than powders containing coarse ingredients when prepared under the same conditions.

With reference to Table IIA it will be seen that all the finely-divided solid explosive materials have the major portion thereof capable of passing through a United States Standard Sieve No. 200. g

The tables above show the increase in velocity obtainable in accordance with this invention and also show that by the use of very finely-divided solid explosive materials a progressive-burning powder can be produced which will give more favorable pressure/velocity relations than those Comparison 0 f ballistics of uncoated single-base powders containing coarse or fine solid explosive materials as an added ingredient Charge Mean Mean Granulation diam- Example No. 7 Powder Added Ingredient Grains Ve10c1ty, Pressure, eter length ft./sec. lb./sq. in in inches 5 K Fine PETN 35.0 2, 395 51, 700 .053.015 X 1/11 L Coarse PETN 33.0 2,356 52,100 .053-.015 X 1/11 6 lVI Fine Tetryl 45. 0 2, 411 39, 200 .05l. 015 X 1/11 N Coarse Tetryl 16.9 1, 524 52,100 .O51. 015 X 1/11 Bullet-AP M2, Frankford Ten shot tests.

TABLE IIA Screen analysis 1 of added ingredients 5 Arsenal Components; Powder K, L, M, and NTested in .30-06 Springfield.

given by powders containing commercial grain size explosive materials.

The compositions of the powders of the present invention are based upon various known singleand double-base powders now being used and these singleand double-base powders are so altered by the addition thereinto of finelydivided solid explosives having particles of a size less than about microns that there is pro ducedan improved and difierent powder as shown by pressure and velocity relationships.

The single-base powder compositions altered in accordance with this invention are those now used by the art and which normally comprise a preponderance of nitrocellulose of the smokeless type, i. e., containing about 13% nitrogen and preferably about 13.25% nitrogen with approximately 1% of a stabilizer, and if desirable, small amounts of oxidizing salts such as potassium nitrate and barium nitrate. These single-base powders are manufactured by colloiding the admixture with solvents such as a suitable mixture of ether and alcohol or of acetone and alcohol. Usually in single-base ,poweders, and alcohol/ ether admixture is used.

The double-base powder compositions altered in accordance with this invention are those now known to the art and are quite similar to the single-base powders with the exception that between and 40% of the nitrocellulose present therein is replaced by a liquid explosive nitric ester such as nitroglycerin or the nitrated glycols or their equivalents. These powders are manufactured by colloiding solvents such as a suitable mixture of ether and alcohol or of acetone and alcohol and preferably the latter.

Both the singleand double-base powders, after having been colloided, are pressed into strands and cut into the desired grain sizes, thereafter they are dried, glazed, and sieved.

Any of the single and double-base powders described above may be used as a base for the present invention and the powder of the present invention is produced by the addition during the colloiding operation of the singleor double-base powders of a predetermined amount of very finely-divided explosive material which is diffi cultly soluble and not fully dissolved in any of the ingredients entering the mixing procedure. The finely-divided explosive material will be present in amount between about and about 65% by weight of the composition and preferably between about and about 40%.

The solid explosive materials which have been found useful in increasing the energy content of the singleand double-base powders are those solid explosives which can be reduced to a particle size of less than about 100' microns in diameter and which are not fully dissolved in the ingredients entering the mixing operation. In particular, the explosive materials may be hexogen, nitrolactose, nitromannite, tetryl, TNT, and PETN, the preferred material being PETN. It is desirable that the solid explosive be non-colloidable, but by regulation of the solvent used, it is possible to use some colloidable solid explosives.

In the preparation of the powders of this invention, it may, of course, be necessary to so regulate their initial combustion by surface modification that the pressure initially developed will not be greater than the maximum allowable. The typ coatings or modifications which are satisfactory are numerous and can be either explosive or non-explosive substances such as, for example, dinitrotoluene, the substituted ureas, and the like. Such coatings are well known in the art. t has been found that approximately the same amount of coating is required to obtain the desired initial combustion rate of powders of this invention as is required to obtain the initialcombustion rate desired in normal singleand double-base powders.

In accordance with the prior art, there are two methods available whereby the initial burning speed of p-ropellent powders may be retarded. One method is to increase the granulation, and consequently the web of the powder, while the other method is to modify the surface of the pewder grains with a deterrent coating. The first of these methods is of limited applicability for as the web is increased, there is a tendency for the powder grains to be expelled from the gun before they are completely burned. Also, when relatively thick web powders are used, an excessive charge is needed to obtain the desired ballistics. The second method has the disadvantage inasmuch as a deterrent coating applied to a powder reduces the average energy content of the composition. By application of the principle disclosed in accordance with this invention, namely, that the burning speed of a smokeless powder may be influenced by the state of division of a crystalline component thereof, there becomes available a third method by which the burning rate of the powder may be desirably regulated. This new method when used in conjunction with proper adjustment of granulation and with also, if desired, employment of a deterrent coating, serves to give improved control of burning characteristics over that which has been previously afforded in accordance with prior art methods. Consequently, novel powders of increased progressiveness of burning may be obtained. This is accomplished by the powders of the present invention as is shown in the foregoing examples in which powders containing finely divided material gave more progressiveness than powders containing coarse ingredients, When made under corresponding conditions.

The advantages of the powders of this invention are the development of high velocity, greater striking power and penetration, and greater accuracy and range.

What I claim and desire to protect by Letters Patent is:

1. A progressive-burning smokeless powder comprising colloided nitrocellulose, stabilizer and between about 1-5 and about 65% solid, organic, high explosive material, said solid explosive material being incompletely soluble and non-colloidable in the ingredients and solvents used in preparing the colloided grains, and being uniformly distributed therethrough and sufiiciently finelydivided to characterize the powder by an increased burning rate, the major portion of said solid explosive material being in the form of particles capable of passing through a United States Standard Sieve No. 200.

2. A progressive-burning smokeless powder comprising colloided nitrocellulose, liquid explosive nitric ester, stabilizer and between about 15 and about 65% solid, organic, high explosive material, said solid explosive material being incompletely soluble and non-colloidable in the ingredients and solvents used in preparing the colloided grains, and being uniformly distributed therethrough and sufficiently finely-divided to characterize the powder by an increased burning rate, the major portion of said solid explosive material being in the form of particles capable of passing through a United States Standard Sieve No. 200.

3. A progressive-burning smokeless powder comprising colloided nitrocellulose having a nitrogen content of at least 13%, stabilizer, and between about 15 and about 65% of discrete particles of a solid, organic, high explosive material uniformly distributed therethrough, said solid explosive material being incompletely soluble and non-colloidable in the ingredients and solvents used in preparing the colloided grains, said discrete particles being sufficiently finely-divided to characterize the powder by an increased accelerating rate, the said discrete particles having the major portion thereof capable of passing through a United States Standard Sieve No. 200.

4. A progressive-burning smokeless powder comprising colloided nitrocellulose having a nitrogen content of at least 13%, liquid explosive nitric ester, stabilizer and between about 15 and about 65% of discrete particles of a solid, organic, high explosive material uniformly distributed therethrough, said solid explosive material being incompletely soluble and non-colloidable in the ingredients and solvents used in preparing the colloided grains, said discrete particles being sufficiently finely-divided to characterize the powder by an increased accelerating rate, the said discrete particles having the major portion thereof capable of passing through a United States Standard Sieve No. 200. g

5. A progressive-burning smokeless powder according to claim 1 wherein said solid, organic, high explosive material is pentaerythritol tetranitrate.

6. A progressive-burning smokeless powder according to claim 1 wherein said solid, organic, high explosive material is hexogen.

7. A progressive-burning smokeless powder according to claim 1 wherein said solid, organic, high explosive material is trinitrotoluene.

8. A progressive-burning smokeless powder according to claim 2 wherein said solid, organic, high explosive material is pentaerythritol tetranitrate.

9. A progressive-burning smokeless powder according to claim 2 wherein said solid, organic, high explosive material is hexogen.

10. A progressive-burning smokeless powder according to claim 2 wherein said solid, organic, high explosive material is trinitrotoluene.

11. A progressive-burning smokeless powder comprising colloided nitrocellulose, nitroglycerin, stabilizer and between about 15 and about 65% solid, organic, high explosive material, said solid explosive material being incompletely soluble and non-colloidable in the ingredients and solvents stabilizer and between about 15 and about 65% pentaerythritol tetranitrate, said pentaerythritol tetranitrate being incompletely soluble and noncolloidable in th ingredients and solvents used in preparing the colloided grains, and being uni- 10 formly distributed therethrough and suificiently finely-divided to characterize the powder by an increased burning rate, the major portion of said pentaerythritol tetranitrate being in the form of particles capable of passing through a United States Standard Sieve No. 20-0.

13. A progressive-burning smokeless powder comprising colloided nitrocellulose, nitroglycerin, stabilizer and between about 15 and about hexogen, said hexogen being incompletely soluble and non-colloidable in the ingredients and solvents used in preparing the colloided grains, and being uniformly distributed therethrough and sufiiciently finely-divided to characterize the powder by an increased burning rate, the major portion of said hexogen being in the form of particles capable of passing through a United States Standard Sieve No. 200.

14. A progressive-burning smokeless powder comprising colloided nitrocellulose, nitroglycerin, stabilizer and between about 15 and about 65% trinitrotoluene, said trinitrotoluene being incompletely soluble and non-colloidable in the in gredients and solvents used in preparing the colloided grains, and being uniformly distributed therethrough and sufficiently finely-divided to characterize the powder by an increased burning rate, the major portion of said trinitrotoluene being in the form of particles capable of passing through a United States Standard Sieve No. 200.

15. A progressive-burning smokeless powder according to claim 11 wherein said nitrocellulose has a nitrogen content of at least 13%.

16. A progressive-burning smokeless powder according to claim 12 wherein said nitrocellulose has a nitrogen content of at least 13%.

17. A progressive-burning smokeless powder according to claim 13 wherein said nitrocellulose has a nitrogen content of at least 13%.

18. A progressive-burning smokeless powder according to claim 14 wherein said nitrocellulose has a nitrogen content of at least 13% HARVEY B. ALEXANDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,899,147 I-Iale Feb. 28, 1933 1,547,809 Hale et a1 July 28, 1925 1,784,189 Keck Dec. 9, 1930 1,478,892 Davis Dec. 25, 1923 FOREIGN PATENTS Number Country Date 543,298 Great Britain Feb. 18, 1942