US2329575A - Propellent powder - Google Patents

Description

Patented Sept. 14, 1943 uN-irr. s re res of Delaware No firawing. Appiicationiilulylifl, 19310, Serial No. 348,552

This invention relates to an improved [priopellent smokeless powder and more particularly to "a'nove1 and improved method of pro'ducin'ga l'iighgravimetric density, free flowing, non-cluster h progressive bur'ning smokeless powder.

l. Heret'ofore the art has recognized and used surface coated propellent powder. The surface coated propellent powder which the art produced by coating powder grains with a deterrent ma;

terial have proved partially satisfactory but there are a number of disadvantages to the known processes of coating. The powder grains coated with deterrent materials by the accepted processes now known to the art are not entirely successful because in all instances there is a tendency for the-individual grains to be coated with unequal amounts of deterrent. Unequal coating resultsin clustering, low gravimetric densities and non-uniform ballistics.

The basic methods'of coating smokeless powder with deterrent materials now :usedby the art comprises, in general, the tumbling or stirring of powder grains in the presence of a quantity-of deterrent material. The tumbling or stirring process is normally carried out in a revolving drum or sweetie barrel and the coating proc esses now used are aided by the addition tothe drum of solvents or non-solvents for the powder grains and coating materials such as is more. par; ticularly described in UVS. Patents 1,661,278 to Troxl r; 2, 13, 1 to w r ee; 2 2 Q.9.., Troxler; 2,028,990 to Olsen; =1,955;927 to McBride; and 1,967,913 to Tibbets. v v Each of the above methods described in the foregoing prior art patents produces propellent smokeless powder grains which finally receive a coating of deterrent material which is not -substantially equally deposited on all surfaces of the rains and which therefore are not of the highest gravim'etric density nor of the uniform ballistics required by modern high velocity riflesand guns The smokeless powder by the prior art methods was found to be more or less sticky, tended to: florm clusters and did' not load"freely into car; tridge'shells, The'non-fre'e ilowing disadvant is mainly due to the lack of a uniform coat of deterrent material on the surface of the grains; Manufactured powders, du'e'to the above difficulties often fail to test satisfactory and have to be reworked with consequent loss of time and pro: duction.

It is the object ofthis invention to'pro'vid" means whereby deterrent substances present on the surface of coated smokeless powder grains mayioe evenly dist'r' tit ed cn 'the-surface o'fsaid smokelesspowder-grains. t

A furtherfiobjec' or th'i's' inv'e'nt-i'on 15 a coated smokeless powoer g an; X gravimetric density aind'ffreqoadihg'bharacterflstics, .A further ooje'ct is to provide a memo or redistributing uneven coinin of deterrent material. I, ..,A.sti11ifur'ther object-of this invention is to provide-a smokeless-powderoi iinproved ballis es; quality and regularity. :other objects trues-iiiventi'ohwillsappear hereiiraiter.

In gene1'al',--the o 'jct'sfdf this inv ntion are accomplished by treating -'s'i1r'fa'e coated shakeless powder produced :und'r methods well-known in sth'e vart, by :"an additional step which rears; tributes the deterrent coating aon' the-grain surface in" suchra: manner that a substaiiti'ally equal coating. or the deterrent material isolate-med on all surfaces of each grain. rhe' additional step includes the treatment or the oatfljsn'iokfless powder grains with a volatile liquid which a non solvent for a poor solvent "for the powder grains themselve's; which is ;a weak solvent but for the deterrent material uses-es a coating for the:powder grains.

-More specifically Ithe treatment in accordance with this invention comprises-placing as erse of surface coated z powder grains .into a sweetie barrelyand adding thereto ab'oi11i 6 to '10% weight of "a volatile liquid ".whi'chi-i's, substantially a non-solvent for the powder -graih's'and which is' a. very weak. solvent 'f0r.ith'e' -deterrent thereon. Usually ethyl alcohol ioriaiimiirtures thereof with water will-be "found desirable-as the volatile-liquid depending upon'the deterrent toibe redistributed The powder chargewithin the sweetie barrel is heated by 'means or a water bath to between about 10. ;.C.-al1d-ab0 ut 20' below boiling point "Ofth volatile -'li'q11iil and their tumbled *rdrbetween about I5Lnii'nuts and two hours or-untii the volatile li'quid lias/redissolved and redistributed" the deterre'n't :ooatiiigh originaily win the graihsintoa substantially edual layer of deterrent coating over the enti're surface of-e'acli grain. It is thought that-the volatile' liduidTedistributesthe deterrent material by dissolving it from these surfaces or the "powder grains hav-- alfigh' concentration of the deterrent material anufi d siting I ition these surfaces having 1 a low concentration or: theldt'erreift'zmaterial until at equilibrium: te r'eachedwherein there's e'q'u'eL-I (EOI ICeI-itlati'On of '.th fle'tefieh't 'Inafte'lial p151 all surfaces,' however,f th' treatment" with" the volatile v'elii'cl may iilcf'ease' the" penetration. The

redistribution or penetration of the deterrent material effected eliminates stickiness of th powder grain and the resulting powder flows more freely, has a higher density, and gives better ballistics than powder not given the treatment. The volatile vehicle preferred for use is 95% ethyl alcohol diluted with from about 20% to about 50% water. The vehicle should be selected so that from about 5% to about 50% of the deterrent material present on the grains may be dissolved therein.

The treatment in accordance with this invention may be carried out in the sweetie barrel directly after the coating and so doing the water present in the powder is used to dilute the alcohol.

The powder is heated at a temperature near the melting point of the deterrent material for from minutes to two hours, depending upon how much redistribution of the deterrent material is necessary. Although an alcohol-water mixture containing from 70-80% alcohol is preferably used, mixtures containing 5095% alcohol can be used. However the treatment is also specifically adapted for treatment of coated powders which have been completed and .found by ballistic tests to be unsatisfactory.

Other volatile liquids which have been found adaptable for the procedure in accordance with this invention are those liquids similar in action to ethyl alcohol and ethyl alcohol-water mixtures mentioned above such as, for example, dioxane, acetone, petroleum naphtha, butyl acetate and the like, either alone or in admixture with each other or with water. Mixtures of dioxane and water, acetone and water, petroleum naphtha and butyl acetate have been found especially desirable. The volatile liquids which are to be used for the process of this invention should have a boiling point less than that of water and in no instance higher than about 120 C. as the treatment of the powder grains above about 80 to 90 C. may cause decomposition and affect the stability of the powder.

The actual redistribution procedure of this invention is carried out by the addition of the socalled volatile liquid to a given weight of coated propellent powder grains and the grains and liquid tumbled in a sweetie barrel for a period of time and at a temperature sufidcient to cause the liquid to act as a solvent for the coating and to cause the liquid to evaporate thus leaving the coating evenly distributed on the surface of the individual powder grains.

In order to specifically point out the improvement which is obtained by the method of my invention, the following progressive burning propellent smokeless powders were prepared:

EXAMPLE 1 A double base tubular rifle powder, granulated .070 x .015 x .091 andcontaining nitroglycerin was coated with ethyl ortho benzoyl. benzo'ate by the coating method described in U. S. Patent 2,152,509. The procedure following.

comprised the addition of 4. parts by weight of water to 50 parts by weight of powder rains contained in a sweetie barrel. The barrel was revolved, and to the water wet powder 1.25 parts by weight of ethyl ortho benzoyl benzoate .was added. The barrel was covered and tumbled for 45 minutes at a water bath temperature of 65 C., after which two parts by weight of additional water and .875 part by weight of additional ethyl ortho benzoyl benzoate were added. The barrel was revolved for an additional 50 minutes at 65 C. and then 2 parts of additional water .-and

.625 part of additional parts of ethyl ortho benzoyl benzoate were added. The barrel was revolved an additional 30 minutes at 65 C., then 15 minutes without the application of heat. After the cooling period, the powder was dried for one day at 55 C., glazed with graphite, screened to remove the fine and coarse powder, humidified by exposure to 60% relative humidity and then tested for ballistics and gravimetric density. The above powder is classed as coated powder and is a commercial powder known to the art. The powder had a gravimetric density of .900 andwhentested in a. .50 caliber rifle allowed a charge of 202 grains to be inserted in the cartridge which gave a velocity of 2670 ft. per second, and a pressure of 49,000 lbs. per sq. inch.

EXAMPLE 2 A portion of the coated powder as described in the Example 1 above was treated in accordance with this invention by placing 1812 parts .by weight of the powderin a .sweetielbarrel, adding thereto parts by weightiof ethyl alcohohand about 20 parts by weight of water and revolving the barrel for about one hour. at atemperature of 65 C. The barrel was revolved an additional 15 minutes without the application of heat after which the powder was dried for a day at 55913,; glazed with graphite, screened'to remove'the fine and coarse powder, humidified by exposure ;to 60% relative humidity and then tested for: bal listics and gravimetric density in the same manner as the powder of Example 1 was tested. The powder of this example has a gravimetricdensity of .995 and when tested in a .50 caliber rifle-"al lowed a charge of 241 grains of powder t'mb'e placed in the cartridge which gave 'a velocity of 2888 ft. per second and'a pressure. of 48,000 lbs; per sq. inch. 5

A comparison of the results obtained with coated powder manufactured by a prior; art method (Example 1) and the results obtained with a coated powder treated in accordance with this invention (Example 2) shows that the process of this invention increased the gravimetric density of the powder grains by.09'5 which al lowed an increase in charge of 39 grains, which increased the velocity of the bullet by 21'8f'ft. per second. while decreasing the pressure of 1000 lbs. per sq. in. These'results indicatethat 'a great improvement is made by givingi 'coated powder the treatment of thisinvention. v

To further show the improvement efiected when coated powder grains are treated by-' the process of this invention," the following examplesare given and the results of gravimetric density and ballistics are listed in Table I.

EXAMPLE 3 area: the. same treatment .as'described Example' 3 except that. thewtemperature oftreatmentwa's'85C.

- EXAMPLE 6;

1812 parts by weight. of coated grains. described in Example 1, were placed in'asweetie barrel and tumbled at 65 C. Withl72 parts by Weight of alcohol and 36 parts by weight of water. After this operation the powder grains were cooled, glazed, screened, humidified and tested inthe manner described in Examples 1 and 2.

EXAMPLE. .7

. A sample of powder was, treated the same way asdescribed in Example .5 except that 75 parts by weight of alcohol and 36 parts by weight of water were used.

ExAMPLE 8 A sample of powder was treated inthe same way as described in Example 6 .exceptthat 360 parts by weight of alcohol and 90 parts by weight of water were used. v The resultsof testing the above powders are given in Table I:

As a further example; a sample of prior art powder was manufactured and coated with dinitrotoluena. The. coating process comprised adding 1812 partsby weightof rifle powder containing 20% nitroglycerin. .to.;a sweetie barrel-,- wetting ,the powder with 125 :parts by weight of water and sprinklingthereon 190: parts by weight of dinitrotoluene. The barrel was .thenrevolved for 40 minutes at a temperature of .85i-C-. After this treatment, 145 parts of additic-nalwater and 90 parts of additional dinitroto1uene. were added and the barrel revolved 1 hour, at 85 C.

One-half of the above coated powder was cooled, dried, glazed, scree ned,- an-dwhumidified and! then submittedto ballistic and gravimetric density testing. The other half of-thestill wet coated powder was treated in. accordance with this invention by placing it back in the .sweetie barrel, adding 90 parts by Weight of alcohol and revolving the barrel for one hourat 85 C. This treated sample was cooled, glazed, screened, humidified .and then tested for g'ravimetric den-. sity and ballastics. The comparative results, of the two powders aregiv'en in Table 'II:'

From the above table, it is noted that the gravimetric density of the treated grains has been materially increased.

. EXAMPLEL-IQO'L:

As a further example of my invention, .50 caliber powder having a granulation of r ,.070 x .015 x .091 was coated as iollows: 550 parts by: wcightof powder-were. wet. with40. parts by;

weight watenand 1.6 parts by weight Centralite (symmetricalfdiethyl diphenylurea). were added and the barrel revolved for,45- minutes at. 8'7 C. To. the-powderwas then added'20 parts additional water and. .9 parts additional- Centralite and the barrelfrevolved for 45. minutesat 87 C. After this treatment, 20 parts by Weight additional water and 5 partsby weight of additional Centralite were added and the sweetie barrel revolved for 30 minutes at 87- C. In this manner, a total of 7,000 lbs. of 50 caliber powder was coated .sothat the coating of the. Centralite variedbetween 5 to 6%. The powder was dried, glazed, screened :and. humidified and then had a gravimetric density. of -.952 .-and a cha-rge of 232 grains of the-powderngaveea velocity-of 2832 .ft..per second and apressure of 51,000 lbs. per e ition in a :50 caliber rifle.v

' EXA PLE E11 A portion of powder =.prep-ared- 'as' described above was then treated in accordance with this invention by placing, it in a sweetie barrel and adding 10% by weight of an alcohol-water (80-20) mixture. After treatment by revolving the barrel for 15 minutes at 50 C. and 45 minutes at 60 0., the powder was dried, glazed, screened, and humidified and when tested gave a gravimetric density of .979 in a .50 caliber rifle. A charge of 240 grains gave a velocity of 2905 ft. per second with a pressure of 48,900 lbs. per sq. inch. A comparison of the above figures shows that the treatment. in accordance with this inyention increases the gravimetric density of powdergrai-ns and-provides better ballistics in given components. I

EXAMPLE 12 In order to further show the improved results of this invention 50 parts by weight of .50 caliber double base powderhaving a granulation of .070 X .015 X .091 were placed in a sweetie barrel' and wet'w'ith 3.5 parts by wei. t i arid l'-'p-art by-weight-of Cent-retire (sym metrical diethyl-diphcnm urea) were added and the barrel revolved fo l- 45 minutes at C. To the powder was then added 1.75 par-ts by we ght of additionalwater and 0.82 5 part by" weight additional Centralite #1 and the barrel revolved for minutes at 85 C." Aft er this'treatment,1.75 parts by weight additional water and 075- part byweight additional Centralite were added and the barrel revolved for 30 minutes C. After this treatment the barrel was revolved for 15 minutes without further heating and the powder then removedfl'from. the barrel, dried, glazed, screened, and humidified. This powder designated as coated untreated powder is compared with -treated samples-in Table III which will follow.

EXAMPLE 13 ing the barrel for 15 minutes at C. and then for 45 minutes at C. the powder was dried, glazed, screened, and humidified. This powder is designated coated dioxane-water treated powder in Table III.

EXAMPLE 14 Another portion of the coated untreated powder described above was further treated in accordance with this invention by placing it in a sweetie barrel and adding by weight of a 90-10 petroleum naphtha-butyl acetate mixture.

Other details of the treatment were exactly as described in the previous example. The finished powder is designated as coated petroleum naphtha-butyl acetate treated powder in Table III.

The coated untreated powder and the three coated treated powders were tested for gravimetric density and ballistics in a .50 Ca. rifle. The comparative results obtained with the different powders are given in Table III below.

TABLE III I Gmvimetric Charge Velocity Pressure Puatmem' type density gr. [.ls. lbs. /sq. in.

None 928 220 2, 899 50. 600 Dioxane-water 983 250 3, 051 49, 400 Acetone-water 971 226 2, 932 5Q, 000 Petroleum-naphtha. Butyl-acetate 948 225 2,927 50, 100

From the above table it is noted that the gravimetric density of the treated samples has-been increased and that the deterrent action of the coating has been made more effective as is shown by the ability to load the treated powders to higher velocities without exceeding the pressure obtained with the coated untreated powder.

The treatment in accordance with this invention gives high yields of unclustered grains and at the same time gives a smokeless powder which is of highest quality and which is better ballistically than the powders manufactured by prior art methods. s

It will be understood that the details and examples hereinbefore set forth are illustrative only, and that the invention as broadly described and claimed is in no way limited thereby.

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

i. A process for producing improved progressive-burning surface-modified propellent smokeless powder grains which includes the steps of placing progressive burning smokeless powder grains having a coating of deterrent material .on their surfaces into tumbling means, adding thereto a volatile liquid which is a non-solventfor Other details of the the said grains. but is ;a;weak' solventfor 'theisaid deterrent on the said -grains,;hea,ti n the solvent and grains to a temperature substantially below the boiling point of the voltaile liquid and tumbling the grains, whereby. thesaid deterrent is redistributed and deposited onall surfaces of the said grains in a substantially equaled? 2..A process forproducing 'improvedp s, l siv'e-burnirig'surface-IriQdified4probellrit smog less powder grains which'iincludes. the.steps of adding to smokeless ,powde zg-rams, .i havingjdt posited on their surface a deterrent materi'a'La volatile liquid which is a:non-solvent for said grains but which is a weak solvent ior said deterrent, heating the liquidwet grainstoa' tempera:- ture substantially below the" boiling point .ofjthe liquid; and tumbling said grains and} liquid, whereby the said deterrent is redistributed and deposited on all surfaces of: the said grains in a substantially equalcoating.

3. A process for producing improved -p-rogres sive-burning surface-modified p' ropellent more; less powder grains which includes the steps of adding to smokeless powder 'grains',.havin' gdposited on their surface the deterrent 'symmetri cal diethyl diphenyl urea, an alcoholwater mixture, which is a non-solvent for said grains but which is a weak solvent for said deterrent heating the alcohol water wet grains to between about 1 C. and about 20 C. below the boiling. point of the alcohol water mixture and tumbling said grains and liquid, whereby the said deterrent is redistributed and deposited on all surfaces of the said grains in a substantially equal coating.

4. A process for producing improved progres: sive-burning surface-modified propellent smokeless powder grains, which includes the steps of adding to smokeless. powder grains, having deposited On their surface the deterrent dinitrotoluene, an alcohol water mixture which is a nonsolvent for said grains but which is'a weak solvent for said deterrent heating the alcohol wateiiwet grains to between about 10;C. and about's2fl. C. below the'boiling point of thealcohol water r'ni'xture and tumbling said grains and. liquid, where by the said deterrent is:redistributed and deposited on all surfaces'ofs the said 'grains -i'n a substantially equal c'oatingfi 5. A process for.-' producing improved progre's s'ive-burning' surface modified' rtpenenvsmtke: less powder grains which inclu'd s the steps or adding to smokeless powder 'g'rains, havin'g'deposited on their surface'the-deterrent ethyl'ortho benzoyl benzoate, analcohoF water mixturefwhicfi is a non-solvent 'for sa-id' grains but which isa weak solvent for said deterrent heating the gueq hol water wet grains to between about 10C} and about 20 o, elow theb oilin'g poin't of 'the "o' hol water' mixture and tumbling "she ,g rain s, an liquid, whereby the said deterrent is redistri 1 and'depositedon all surfaces ofthe saidgr in a substantially, equalcoating. 1.11: ,.,.1,

ELTON R; ALLISON. ELLSWORTH: S. GOODYEAR.