US2267261A - Smokeless powder - Google Patents

Description

' SMOKELESS roan.

' Elton n. n, Wharton, N. a, gnor to Hercules ll'owder Company, W

ilmington, Dei a corporation oi Delaware No Drawing. Application November c, 1940, Serial No. cameo 4 Claims.

This invention relates to a method of preparing progressive burning smokeless powder and more particularly to an improved method of coating smokeless powder with a deterrent material, and to smokeless powder coated with a water soluble deterrent material.

It has been known to coat smokeless powder with a deterrent material in order to provide for a close control of the burning rate and to produce a high velocity of the projectile without excessively high breech pressures. Such coating materials desirably penetrate the powder grains more or less, so that as the powder burns, the successively exposed surfaces contain grad- 'ually less and less of the deterrent material, thus causing the combustion of the grains to proceed with increased speed.

Treatment of smokeless powder grains with deterrent to render their combustion progressive, by methods heretofore known, while producing the desired results to a degree, has been open to a number of objections. For example, the use of a deterrent and powder grains alone requires long continued heat and tumbling to obtaini uniform distribution of deterrent on thepowder grain which may lead to explosion. The use of water with the deterrent and powder grains requires long treatment and renders uniform coating dimcult on account of the water insolubility of many deterrents heretofore known. The use of a deterrent solvent, e. g., benzol, is open to the great risk of explosion of solvent vapors, their poisonous nature, and the economic necessity for recovery of the solvent. The use of prior known water soluble deterrents has furthermore not produced smokeless powder of high ballistic st bility, i. e., the maintenance with age of the al ballistics produced by the powder.

is an object of this invention to produce a coated smokeless powder which overcomes the disadvantages of prior known powders.

it is a further object of this invention to produce a smokeless powder coated with a water soluble deterrent substance.

A. still further object of this invention is to produce a smokeless powder coated with phthalide.

A further object of this invention is to producea coated smokeless powder which has an improved hot storage ballistic stability.

Qther objects will appear hereinaiter.

The objects of my invention are accomplished by coating grains of smokeless powder with phthalide.

As an example for carrying out my invention 100 parts by weight of double base (29% N. GJ)

riflle powder granulated .045.015 x 1/21 were placed in a sweetie or tumbling barrel and wet with 15 parts by weight of cold water. The wet powder was tumbled and heated to 75, C. and then 5 parts by weight of phthalide added. The mixture of powder, water and phthalide was agitated 30 minutes at 75 C. and 30 minutes at 85 0., removed from the barrel, dried, glazed and humidified. One portion of the powder was stored for 30 days at 50 C. and another portion for 30 days at normal atmospheric temperatures and then both portions rehumidified. The powder which had been stored hot wasithen tested in direct comparison with the powder which had been stored at normal temperatures.- For the sam charge of powder the hot storage sample produced 1,000 lbs/sq. in. higher pressure than the normal storage powder.

' parts by weight of double base (20% N. G.) rifle powder granulated .045.015 x 1/21 were placed in a sweetie barrel and wet with 15 parts by weight of cold water. The wet powder was 2 tumbled and heated to 75 C. and title parts by weight-oi diacetin added. The mixture of powder, water and diacetin was agitated minutes at C. and 30 minutes at 0., removed from the barrel, dried, glazed, and humidified. One 30 portion of the powder was stored for 30 days at 50 C. and another portion for 30 days at normal atmospheric pressures and then both portions rehumidifled. The powder which had been stored hot was then tested in direct comparison 35 with the powder which had been stored at normal temperatures. Fdr the same, charge of powder the hot storage sample produced 9,100 lira/sq. in. higher pressure than the normal storage powder. I The increased hot storage capacity of smokeless powder treated with water soluble phthalide as compared to the water soluble diacetin is apparent from the above examples. I am not at present prepared to give a sound theoretical explanation of the improved behavior of powder coated with phthalide as compared to powder coated. with previously known water soluble deflig listic stability test. lihthalide is a solid under As a comparison with the above example,

these conditions. It is my belief that poor bai listic stability is caused by mobility of deterrent molecules and that the molecules of deterrent substances which are in the liquid state under normal conditions will have greater mobility than those of materials which are solids under the same conditions. When a deterrent is applied to a smokeless powder grain, it penetrates into the powder grain surfaces more or less according to the temperature of application, the solvent or plasticizing power of the deterrent, and the state of aggregation of the deterrent. After the powder is dried, glazed, humidified and cooled to normal temperatures, this penetration due to deterrent mobility nearly ceases. It may continue at a very low rate at normal temperatures but if the powder is stored at somewhat higher temperatures the mobility and penetration tend to increase. Under thes conditions the deterrent which is normally in the solid state.

of aggregation will give improved ballistic stability.

It is tobe understood that single base as ,well as double base rifle powder may be treated in accordance with th 'teachings of this invention. The amount of phthalide added may be varied in accordance with the granulation of the powder and the deterrent effect desired. While 5% by weight of the weight of powder being coated was a satisfactory amount in the'instance of the example given it is to be understood that I am rent action.

Where in this specification I refer to phthalide I meanthe inner ester of o-hydroxy-methylbenzoic acid obtained by the reduction of phthalic anhydride or. chloride with Zn and HCl and which has a melting point of 73 C., and a boiling point of 290 C.

My invention provides an improved smokeless powder having an increased hot storage ballistic stability, and one which is comparatively safely, economically and eillciently produced. This powder may be used in the manufacture of cartridge ammunition.

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

1. A smokeless powder comprising smokeless powder grains surface coated with phthalide.

2. A double base smokeless powder comprising smokeless powder grains surface coated with phthalide.

3. A single base smokeless powder comprising smokeless'powder grains surface coated with phthalide.

4. A smokeless powder comprising smokeless powder grains coated with phthalide in amount from about 1% to about 10% by weight of the powder.

ELTON R. ALLISON.