US1838345A - Propellent powder - Google Patents

Description

Patented DecVZQ), 19311 serene RICHARD GEORGE WOODBRIDGE, OF WILMINGTON, DELAWARE, ASSIGNOR TO E. I. DU POINT DE NEMO'URS & COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE No Drawing.

7 This invention relates to a fiashless propellent powder and more particularly to a flashless propellent powder of the nitrocellulose type.

This case is a continuation in part of my copending application Serial Number 81,086, filed January 13,1926.

Dautriche, Comptes Rendus 1908, volume 146, pages 535-538, disclosed that the use of sodium and potassium salts, particularly saltpetre (potassium nitrate), prevented the ignition of fire damp in mines when used in small amounts, 3 to 6%, in explosives having an ammonium nitrate base. Dautriche in the same article cited-the use of salts of sodium and potassium for the suppression of muzzle flash and of the recurrence of flame (flare back) in the firing of smokeless powder.

Vennin and Chesneau Les Poudres et Explosifs et Les Mesures de.Securite dans les Mines de Houille (published in 1914) discusses at considerable length the influence of alkaline salts in explosives and smokeless powder for suppression of flash as follows:

Page 139, section 107-Influence of alkaline salts. 1

Page 158, section 123-Flare back.

Page 318, section 300Volatilizable salts and alkaline salts.

Page 445, section 419-Flash and flare back.

Page 445, section 420.

According to Vennin and Chesneau, page 445, section 420, above, Dautriche also appreciated that the saltpetre content of the black powder making up the priming char e also acted to suppress flash, as will be 0 served from the following:

The addition of alkaline salts to the charge gives'us much greater safety as it almost always causes the gas to be extinguished (Dautriche Comptes Rendus 1908, volume 146, page 537). The experiments made by M. Dautriche in this connection have also shown that the primin charge of black powder reduces considera ly, but not entirely, the probability of flare back.

p The use of saltpetre, or other sodium or potassium salts for extinguishing muzzle flash in guns, has not found general use in Application filed April 13,

1928. .Serial No. 269,881.

military propellants, due to a number of factors. According to Marshall, Explosives, (year 1915) page 246, I The quantity of smoke is thereby increased and this will reveal the position by day, and will obstruct the gunmen. Marshall, in A Short Account of Explosives (year 1917) page 96, states The flame can be diminished by the addition of a cooling agent to the powder or a small proportion of a salt of sodium or potassium, but these additions are liable to increase the amount of smoke, which is equally objectionable, especially by day.

Another objection to the use of salts of sodium and potassium for the prevention of muzzle flash, is that many of these salts are seriously hygroscopic. Edwards, British Patent Number12,188 of 1908, states It haslong been suggested that this result (prevento decompose under the influence of hygrometric variation, and to become deliquescent inside the substance of the explosive itself in which they have been embodied, and consequently to bring about the more or less rapid and more or less dangerous decomposition of the explosive.

Another and serious objection to the use of salts of sodium and potassium for the pre vention of muzzle flash, is that military cannon powders of the nitrocellulose type have for many years, and particularly during the World War, been water dried, that is, treated in hot water to remove more rapidly the volatile solvents, ether and alcohol, used in their manufacture. Sodium and potassium salts which appear to possess the special property of preventing muzzle flash, are readily s olu ble in water, particularly in hot water, so that it would be expected that salts of potassium and sodium would be readily removed from the nitrocellulose colloid if the same were subjected to a. water drying treatment. I

It is known that Germany, during the World War, made use of packets of potassium chloride which were added to the powder charge, largely at night, for the prevention of muzzle flash. It is also known that such additions seriously disturbed the ballistics of the powder charge as relatively large amounts of potassium chloride were required.

German Patent No. 301,659, issued May 14, 1921, discloses that the use. of small amounts of potassium chloride when added tosmokeless powder will prevent the occurrence of muzzle flash. Paragraph 4, first sentence, of this patent states as follows:

With all nitrocellulose powders, and with powders containing nitrocellulose and nitroglycerine for guns of small caliber, small additions of potassium chloride of 0.5 to 2% suflice; on the other hand, with nitrocellulose-nitroglycerine powders of high combustion temperatures for larger guns, amounts of 3 to 5% are necessary. 4

In my copending application No. 81,086, filed January 13, 1926, I have shown that flashless results can be obtained in small guns such as the 75 m/m field gun, model 1897, with a propellent powder of the following composition 85 parts nitrocellulose of about 13.15% nitrogen 10 parts dinitrotoluol 5 parts dibutylphthalate 1% added diphenylamine and with other similar compositions in which dimethyldiphenylurea, acetyl laurins, ethyl palmitate, diethylphthalate, and dibutyltartrate are substituted for the dibutylphthalate. However, the composition containing the dibutylphthalate is the preferred composition.

In larger guns such as the 155 m/m G. P. F. gun I disclose in my said copending application that it is necessary to increase the amount of dibutylphthalate to about 10 parts, decreasing the amount of nitrocellulose from 85 to 80 parts in order to obtain flashless results, but that elimination of the luminous muzzle flash in this manner gives rise tomore smoke.

The manufacture and testing of propellent powders for guns requires considerable time and large expenditures, but it is only by such testing that claims for an improved propellant can be substantiated. The fact that a powder givesflashless results in one gun does not necessarily mean that the same composition or a different combination of the same ingredients, will give fiashless results in all guns. Furthermore, flashless results mean little or nothing if the same are not accompanied by the desired or standard ballistics far the particular gun, together with an acceptable uniformity in Velocity and pressure with an amount of smoke which is acceptable to the user of the powder, besides satisfactory chemical stability as well as ballistic stability of the powder.

I have found as a result of actual experiments covering a period of years that flashless results with the required standard ballistics and without an objectionable amount of smoke, can be readily obtained in a numher of the smaller guns, including the 2.95

inch mountain gun, 75 m/m pack howitzer,

75 m/m field gun, model 1897, 75 m/m field gun, model 1920 (normal charge), and 105 m/m howitzer with powder of the composition 85 parts nitrocellulose of about 13.15% nitrogen 10 parts dinitrotoluene 5 parts dibutylphthalate 1% added diphenylamine.

Also that similar satisfactory results are obtained in the 75 m/m field gun, model 1920 (super charge) and in the 3-inch anti-air craft gun, model 1917, with 15-pound projectile with powder of the composition 83 parts nitrocellulose of about 13.15% nitrogen 10 parts dinitrotoluene 7 parts dibutylphtha-late 1% added diphenylamine.

increased amount of. smoke; in other gunsand for other uses, the amount of smoke is a serious disadvantage. It is also obvious that a powder which may give oil an objectionable amount of smoke in the day-time may be entirely satisfactory for night firings. I have therefore, continued experiments with the object of obtaining flashless results with reduced amount of smoke in the more difiicult guns, especially the larger guns.

The object of my invention is to produce a smokeless propellent powder from nitrocellulose without the aid of nitroglycerine, which will possess greatly reduced hygroscopic qualities as compared with powder made from nitrocellulose only. A further object of my invention is the elimination of the white luminous flash such as is produced at the muzzle of guns, for example, by the present Pyro Service Powder of the United States Government. This white luminous muzzle flash is commonly attributed to the ignition of the combustible gases formed during the con ibustion of smokeless powders, due

ide, carbon monoxide, hydrogen, water vapor and small .amounts of methane. Of these, the combustible gases are carbon monoxide,

hydrogen and methane. The white luminous flash at the muzzle of the gun is due to the combustion of these gases in the presence of oxygen. This combustion can be prevented in the case of small arms by firing into an atmosphere of carbon dioxide. When the White luminous flash is eliminated in this manner, or is eliminated by the use of a pow-.

der containing suitable ingredients, only a small reddish glow appears at the muzzle of the gun. This glow is not readily visible and can be easily concealed.

A further object of my invention is the production of a nitrocellulose propellent powder which, besides being of greatly reduced hygroscopicity and flashless in most guns, can be dried not onlyin air but also in hot water to more effectively and expeditiously remove the volatile solvents added for the purpose of assisting in the colloiding of the nitrocellulose.

A still further object of my invention is to retain as far as possible, the advantages of the improved propellent powder as described in my copending application, aforesaid, therefore only modifying its composition to the slightest degree necessary in order to obtain flashless results in certain guns in which flashless results or consistently flash less results are not readily obtained withou excessive amounts of black smoke.

Other objects will appear as the descrip tion proceeds.

These objects are accomplished by incorporating in the powder an alkali salt that is non-hygroscopic up to about 90% relative humidity at atmospheric temperatures and that has no harmful action on the stability of the powder. q I

For example, I have obtained consistently flashless results in the 3-inch anti-air craft gun, model 1917, with the 12.7 pound projectile and with only the smallest amount of whitish to whitish gray smoke with powder of the following composition:

85 parts nitrocellulose of about 13.15% nitrogen content 10 parts dinitrotoluene 5 parts dibutylphthalate 1 part diphenylamine r 1 part potassium sulphate.

I have also found that the above powder gives complete and consistently flashless rewhereas flashless results are only obtained with powder of the composition:

82 parts nitrocellulose of 13.15% nitrogen '10 parts dinitrotoluene 8 parts dibutylphthalate 1 part diphenylamine by the use of an extra ignition charge of about 5 ounces of black powder placed preferably at the front, end of the powder charge. In the latter case, while flashless results are usually obtained, the amount of smoke is considerable and the color medium to dark I have found that approximately 1% of potassium sulphate in the above composition can be replaced by an equal amount of .po-

tassium nitrate, potassium phthalate, sodiumnitrate and sodium chloride. Salts which I have found do not give flashless results or consistently so, include calcium phthalate, lead phthalate, strontium phthalate, calcium oxalate, barium sulphate, lead sulphate and calcium sulphate, and also potassium chloride when added in the same amount as potassium sulphate in the above formula.

Of the salts of sodium and potassium which I have found give flashless results, I prefer to use those which are non-hygroscopic up to about 90% relative humidity at atmospheric temperatures and also which have no harmful action on the stability of the powder. For example, I have found that sodium nitrate, and potassium phthalate are, too bygroscopic to be suitable for use as an ingredient of a military propellent powder to give the most satisfactory results. Also sodium chloride in addition to being too hygroscopic, will blacken powder containing di- .phenylamine, which discoloration is very obj ectionable, indicating harmful action on the stability of the powder. Potassium chloride is open to the same objection of blackening the powder even if this salt had given equally satisfactory results as regards suppression of flash.

Of the salts tried, I have found that potassium sulphate and potassium nitrate are the most satisfactory, so far as obtaining I 3-inch anti-aircraft gun, model 1917, with the 12.7 pound projectile: 85 parts nitrocellulose of about 13.15% nitrogen 10 parts dinitrotoluene 5 parts dibutylphthalate 1 part diphenylamine 1 part potassium sulphate or potassium ni trate.

In the ignition of the above powder there was used the regular ignition charge as used for propellent powder of the Pyro type, in the 155 m/m G. P. F.'gun, namely a 21 gram two compositions made up for the 3-inch anti-aircraft gun, model 1917, and 'fired with the 12.7 pound proof slug with regular 110 grain primer.

Potas- Percentslum Mean g fi i Muzzle pressure 51 Composition of powder sulphate finighed g figyg gg Muzzle flash and smoke in p r. powder platinic g g fi as made chloride method 8% pigs. dN/Cf13t.1]5%1N. 1 s. ini r 0 no p ts. dibutylphthalate. 0. 98% 0. 84% 5 lbs. 2693 28050 No flash and medium white smoke. 1 pt. diphenylamine. 1 pt potas. sulphate.

85 pts. N/C 13.15% N. pts. dinitrotoluol. 5 pts. dibutylphthalate. 2. 41% 2. 5 lbs. 2727 30070 No flash and medium white smoke. 1 pt. diphenylamine. 3 oz. 2.5 pts. potas. sulphate.

Pyro Service Powder. None. None. 10 8% lbs. 2703 28540 Large flash.

primer with an 8 ounce ad of black powder at the base of the pow er charge. As black powder contains about 75% of saltpetre, the 8 ounces of black powder would contain 6 ounces of saltpetre. When muzzle flash is obtained with-the ordinary powder this saith petre is volatilized by the flash. \Vhen the muzzle flash is prevented as by the addition of 1% potassium sulphate in the powder, this six ounces of saltpetre is the cause of a certain amount of white smoke due to finely divided particles of potassium carbonate and potassium sulphate caused by the combustion of the black ignition powder. This white smoke in the present example would be increased by the smoke from about four ounces of potassium sulphate or the amount present in the 25 pound required weight of charge of powder containing about 1% of potassium sulphate. While occasional flashless results can be obtained with powder of the above composition containing 0.50% and 0.75% potassium sulphate instead of about 1.0%, the margin of safety as regards flashlessness is seriously reduced thereby and besides the amount of white smoke is reduced only by the small reduction in the amount of potassium sulphate in the powder as the eight ounces of black ignition powder is fixed and required for the ignition of the powder charge.

In view of the high solubility of potassium sulphate in water, the powders containing this salt were first air dried for both the 3- inch anti-aircraft gun, model 1917, and the 155 m/m GI P. F. gun. However, I have discovered. that powder of the above composition conta-ining 1% of potassium sulphate can be water dried with so little loss of the potassium sul hate that nospecial m caution need be taken in the water treat ment of the powder to prevent or minimize the extraction'of the salt. For example, the

I following table gives the results obtained on The above powders containing potassium sulphate were subjected, after solvent recovery treatment to recover ether and alcohol used in their manufacture, to a water drying treatment, that is, steeping in hot water at 55 C. for six days with frequent changes in water. The loss of potassium sulphate was very small. On the other'hand potassium nitrate appears to be more readily removed from the powder during the water drying treatment, but less so than from an etheralcohol nitrocellulose powder without additions of non-volatile, water-insoluble nitrocellulose solvent such as dinitrotoluene and dibutylphthalate. This difficulty of removing potassium sulphate and to somewhat a lesser degree, potassium nitrate from my powder, may be due to the fact that the mixture of dinitrotoluol and, dibutylphthalate both of which are solvents for nitrocellulose, give a more thoroughly colloided powder than an ether-alchol colloid of the same nitrocellulose without additions of dinitros toluol and dibutylphthalate, the ether-alcohol colloids only the soluble and not the insoluble nitrocellulose, while the mixture of dinitrotoluol and dibutylphthalate colloids both the soluble and insoluble types of nitrocellulose durin the process of manufacture. Thus the discovery that potassium sulphate when used in my composition is not readily extracted from the powder during the water drying treatment, is a very important one, as large economies in time and money are possible when the propellent powder can be water dried as against the air discolor the 10 white smoke to that which would normally be produced from the black powder contained in the primer or the ignition pad. The potassium sulphate has no harmful effect. on the chemical stability and does not powder as does potassium chloride. I have experimented with potassium sulphate by the addition of packets of this material contained in silk bags to the powder charge. I have found that by the use of a larger quantity of potassium sulphate than is required when uniformly incorporated in the powder, flashless results are frequently obtained, but on account of the larger amount of potassium sulphate "used, the 'quantity of white smoke is appreciably increased, and the ballistics of the powder disturbed. It is therefore obvious that the small quantity of potassium sulphate which, when incorporated in the powder prevents muzzle flash, is due to the fact that the salt is uniformly distributed throughout the powder. It is therefore obvious that in cases where it is preferred not to incorporate potassium sulphate in the powder, but to use it by adding it to the powder charge, that better results are possible by more uniformly distributing the potassium sulphate throughout the charge such as by using silk weighted with the salt or nitrocellulose, cellulose ester or other films in which the salt has been incorporated. However, I prefer to incorporate the potassium sulphate in the powder, in orderto simplify the loading of the powder and the use of the loaded charges.

The manufacture of the powder requires no special skill. The nitrocellulose is dehydrated with denatured ethyl-alcohol of suitable grade and then colloided in asuitable mixer with the addition of ether. There is added in the ether or directly to the mixer, the dinitrotoluene and the dibutylphthalate.

Due to the solvent action of the latter two ingredients, less alcohol and ether are required than are usually employed for nitrocellulose powders not containing these ingredients. The potassium sulphate is uniformly and finely ground in a ball mill or other type of mill to a fineness sufficient to passthrough a wire screen with meshes to the inch. However, I do not limit myself to-this fineness. Diphenylamine is usually added as a stabilizer and is usually dissolved in the ether. The colloid may be pressed either in tubular grains with one or more perforations or in the solid grain, or in the ribbon or strip form of grain. The grains of powder are given thorough solvent recov ery treatment before the final drying, which may be in air or hot water at a temperature not in excess of 60 C. although a higher temperature may be used without injury to the chemical stability of the powder.

While I prefer to use a standard composition containing parts nitrocellulose of about 13.15% nitroen. '10 parts dinitrotoluol 5 parts dibutylphthalate 1 part diphenylamine 1 part potassium sulphate it will be understood that I do not limit myself to these proportions or to these ingredients. For example, the nitrocellulose may be of a mixture of the type soluble in ether-alcohol with the type insoluble in etheralcohol mixture (two parts ether to one part ethyl-alcohol) and ofa higher or lower nitrogen content than 13.15% or it may be entirely of the soluble type, having a nitrogen content between about 12.0 and about 12.80%.

The dinitrotoluol may be decreased or increased or replaced by other nitro compounds.

The dibutylphthalate may also be increased or decreased or entirely omitted, or replaced by other "cooling agents which'are solvents for nitrocellulose such as those mentioned in the foregoing and in my copending application aforesaid.

The amount of potassium sulphate which I prefer to use will -be in the neighborhood of 1%, but it will be understood that it is added merely for the purpose of preventing muzzle flash to a composition flashless in many guns and approaching flashlessness in other guns.

Therefore, the minimum quantity required to prevent flashmay be as low as 0.50%. I prefer not to add more than 2.0% in order to obtain the minimum amount of white smoke.

While I prefer to use potassium sulphate as an ingredient of powder of the nitrocellulose type, that is, without nitroglycerine, on account of the recognized lower erosion caused by nitrocellulose powders as compared with nitroglycerine, I do not intend to be limited in my claims to powders of the nitrocellulose type. It is obvious that the flash preventing properties of the potassium sulphate are equally applicable to all propellent powders, regardless of the composition. Furthermore, in powders of the nitroglycerine type having a high temperature of combustion, an increased amount of potassium sulphate will be required to prevent muzzle flash unless the temperature of combustion of the nitroglycerine powder is reduced by the use of Vaseline, carbon, methylethyldiphenylurea or diethyldiphenylurea or ders, it is preferred to air dry the powder,

since there is serious loss of nitroglycerine during hot water steeping of powder containing this ingredient. I

The invention is applicable to the production of flashless powder for small arms and cannon.

Some of the advantages of my flashless powder over other powders are briefly as follows:

Flashless results are obtained by the uniform incorporation in the powder of relative ly finely pulverized potassium sulphate. Due to the fact that the composition of 85 parts nitrocellulose of about 13.15% nitrogen content. 10 parts dinitrotoluol,

5 parts dibutylphthalate 1 part diphenylamine gives flashless results in many of the smaller guns, and tends to approach fiashlessness in other guns, a less quantity of potassium sulphate is required than would otherwise be the case, which results in flashlessness being obtained. with less smoke than if a larger -quan tity were required.

Powder of the above type containing potassium sulphate may be dried by steeping in hot water without removing any substantial amount of the salt.

Potassium sulphate is less hygroscopic than the saltpetre or potassium nitrate used in the black -powder ignition charge so that the powder can be subjected to humidity conditions up to and above 93% relative humidity, at which relative humidity potassium nitrate will deliquesce, without change other than slight increase in moisture, due to the higher humidity condition. Potassium sulphate is not hygroscopic until about 97% relative humidity.

Potassium sulphate does not discolor powders containing diphenylamine and is without harmful effect on the stability of powder.

As many apparently widely different embodiments of this invention may be made without departing from the spirit thereof, it is to be understood that I do not intend to limit myself to the specific embodiments thereof except as indicated in the appended claims.

I claim:

1. A propellent powder comprising nitrocellulose in combination with a deterrent eX- plosive and deterrent material, each of which when in-liquid form has a substantial solvent action on the nitrocellulose, and a muzzle flash eliminator comprising potassium sulphate.

2. A propellent powder comprising nitrocellulose in combination with substances which when in liquid form have a substan tial solvent action on the nitrocellulose, said substances comprising nitro-aromatic compounds, and a cooling agent, and a muzzle flash eliminator comprislng potassium sulphate.

3. A gelatanized nitrocellulose propellent powder containing a muzzle flash preventative which comprises potassium sulphate.

4. A gelatinized nitrocellulose propellent powder containing a muzzle flash preventative which comprises 0.5 to 2.0 per cent of potassium sulphate.

5. A propellent powder. comprising nitro cellulose, a polynitrotoluene, a dialkylphthalate, and potassium sulphate.

6. A propellent powder comprising nitrocellulose, a polynitrotoluene, a dialkylphthalate, and 0.5 to 2.0 per cent potassium sul- 10. A propellent powder containing as an ingredient, potassium sulphate.

11. A propellent powder containing as ingredients, nitroglycerine and a small quantity of potassium sulphate.

12. A propellent powder containing as ingredients, nitrocellulose, nitroglycerine, and

a small quantity of potassium sulphate.

13. A propellent powder containing as an ingredient, 0.5 to 2.0 per cent potassium sulphate.

1 1. A propellent powder containing as ingredients, nitroglycerine and .5 to 5.0 per cent potassium sulphate.

15. A propellent powder containing as ingredients, nitrocellulose, nitroglycerine, and .5 to 5.0 per cent potassium sulphate.

16. A propellent powder charge containing a muzzle flash preventative comprising potassium sulphate.

In testimony whereof, I aflix my signature.

RICHARD GEORGE WOODBRIDGE.