US2179313A

US2179313A - Progressive-burning smokeless powder

Info

Publication number: US2179313A
Application number: US233596A
Authority: US
Inventors: Elton R Allison
Original assignee: Hercules Powder Co
Current assignee: Hercules Powder Co
Priority date: 1938-10-06
Filing date: 1938-10-06
Publication date: 1939-11-07
Anticipated expiration: 1956-11-07

Description

Patented Nov. 7, 1939 rear orrles PROGRESSIVE-BURNING SMOKELESS POWDER Elton R. Allison, Kenvil, N. J., assignor to Hercules Powder Company, Wilmington, Del, a corporation of Delaware No Drawing. Application October 6, 1938, Serial No. 233,596

7 Claims.

This invention relates to smokeless powder, and particularly to coated, deterred, or progressive-burning smokeless powder.

Smokeless powder, on combustion in the chamher of the gun in which it is used, tends to burn initially at a more rapid rate than is desired and thus produces high breech pressures. This defeet is not overcome by using larger grains of powder, in the case of those powders intended to give maximum results in center-fire rifle cartridges. Many attempts have been made in the past to deter the initial rate of burning of the powder grains by coating said grains with an agent, explosive or non-explosive, which will slow down the initial rate of combustion of the powder grains, thus extending the period of time taken by the grains to burn completely, and in this way reduce the otherwise high breech pressure in the The coating material used penetrates the 530 powder grains more or less, so that, as the powder grains burn, the successively exposed surfaces contain, gradually, less and less of the deterrent material, thus causing subsequent combustion of the powder grain to proceed with increasing .3 speed as the bullet travels down the bore of the gun.

In .the past, many substances have been used, without complete success, to coat smokeless powder grains, e. g., such materials as diethyldiphena ylurea, dimethyldiphenylurea, dinitrotoluene, a1-

k'yl phthalates, or mixtures thereof, and various methods of applying such deterrent substances have been known.

The known methods of deterring or coating ,3; smokeless powders have not been completely effective in that they have not produced smokeless powders of high gravimetric density combined with high ballistic stability. By ballistic stability is meant the maintenance, with age, of the inw :tial ballistics produced by the powder. For example, many of the coating agents continue to penetrate into the powder grain, particularly in warm climates, and thus alter their deterrent characteristics.

A; With modern loads of deterred smokeless powstable with age and of high gravimetric (or loading) density. The high gravimetric density of my coated powders enables me to use greater charges than hitherto permitted by the volumetric capacity of the cartridge, which is a dis- -5 tinct improvement over prior art powders and an advantage which has been sought for many years by the art. In addition my improved smokeless powder is not subject to clustering or sticking together of the grains. 101

In the preparation of coated smokeless powder in accordance with my invention, I use as coating agents the aryl esters of benzoic acid or the aryl esters of a lower fatty acid which are characterized by having a melting point within the '15} range from about 35 C. to about 110 C. Among these compounds which I have found suitable as coating agents are phenyl benzoate, naphthyl benzoate, A-naphthyl acetate, B-naphthyl acetate, B-naphthyl prop-ionate, and B-naphthyl isobutyrate. The smokeless powder may be coated with any of these compounds alone or with various combinations of these compounds or these compounds may be used in combination with other coating agents.

I may use as the powder grain to be coated either a single base (nitrocellulose) powder, or a double base (nitrocellulose-nitroglycerin) powder. Although the powder grain may be of any size, I have found that my coating agents offer the most advantage when used with the larger caliber powders.

In practicing my invention the herein specified coating agents are applied to the smokeless powder as a solution ofsaid coating agents in a .35 volatile solvent which is substantially a nonsolvent for the smokeless powder. Among the volatile solvents which I have used are toluene, ethylene dichloride, petroleum naphtha, isopropyl alcohol and ethyl alcohol and of these I prefer using 95% by volume ethyl alcohol. To 100 parts by weight of smokeless powder I add from about 1 to about 10 parts by weight of the specified coating agents, dissolved in a suitable quantity of solvent. The smokeless powder is treated with the coating agent in any suitable manner, for example, by tumbling the powder and the coating agent solution in a barrel at a temperature within the range from about 10 C. to about 95 C. for a period of time between about 5 minutes to about 4 hours, after which the powder so coated may be subjected to further heat treatment to eliminate any remaining solvent, if this appears desirable. The time and temperature of treatment, as well as the quantity of coating As specific illustrations of the carrying out of my invention, the following examples are given: Example 1 Nine hundred and seven parts by weight of a double base smokeless powder containing 20% nitroglycerine, pressed through a 0.045 inch die having a 0.015 inch pin, and the strand so produced' cut into 11 particles per inch, was placed in a sweetie barrel maintained at 75 C., and to this was added 45.3 parts by weight of phenyl benzoate dissolved in 160 parts by weight of ethyl alcohol. The mixture was tumbled in the closed sweetie barrel for hour at 75 C., then for another hour at 90 C., after which time the powder was removed to a dry house and dried for three days at 55 C., then graphited, screened and exposed to an atmosphere of 50% to 60% relative humidity to bring the moisture content to equilibrium. A yield of 94% of unclustered powder was obtained having a gravimetric density of 0.951.

Example 2 Nine hundred and seven parts by weight of the same smokeless powder as in the preceding example was coated in the same manner as in Example 1 with 45.3 parts by weight of B- naphthyl acetate dissolved in 160 parts by weight of ethyl alcohol and then finished in the same manner indicated in Example 1. A yield of 97% of unclustered powder was obtained having a gravimetric density of 0.940.

I Ezrample 3 As a comparison with the above examples, I coated 907 parts by weight of the same smokeless powder as above in the same manner as already indicated with 45.3 parts by weight of symmetrical diethyldiphenylurea (Centralite #1). A yield of 68% of unclustered powder was obtained having a low and unsatisfactory gravimetric density of 0.919.

Powders prepared in accordance with the three examples above were fired in a .30 caliber-1906 cartridge case using a 110 grain bullet, the cartridge being loaded in each case with sufficient powder to fill said cartridge to the base of the It will be noted in the above table that powders coated with the agents disclosed by the present invention have an appreciable velocity increase over comparator Example 3 in which a prior art coating material is used. Furthermore, in comparison with Example 3 it will be noted that a greater charge of powder can be utilized in the same space in the cartridge in the case of Examples 1 and 2 which is, of course, due to the higher gravimetric densities of powders prepared in accordance with this invention.

To illustrate the improvement in stability obtained by my coated powders, I subjected some of these to warm storage using for comparison a powder coated in the same manner with butylphthalyl butylglycollate. These results are shown in the following table:

The improvement in ballistic stability is apparent from the above table.

It will be understood that the foregoing examples are by way of illustration only, and that the scope of my invention is not to be limited thereto, except as hereinafter defined by the claims.

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

1. Smokeless powder grains surface coated with an aryl ester of an organic acid selected from the group consisting of benzoic acid and a lower fatty acid, said ester being characterized by having a melting point within the range from about 35 C. to about 110 C.

2. Smokeless powder grains surface coated with about 1% to about by weight of an aryl ester of an organic acid selected from the group consisting of benzoic acid and a lower fatty acid, said ester being characterized by having a melting point within the range from about 35 C. to about 110 C.

3. Smokeless power grains surface coated with phenyl benzoate.

4. Smokeless powder grains surface coated with B-naphthyl acetate.

5. Double base smokeless powder grains surface coated with an aryl ester of an organic acid selected from the group consisting of benzoic acid and a lower fatty acid, said ester being characterized by having a melting point within the range from about 35 C. to about 110 C.

6. Double base smokeless powder grains surface coated with phenyl benzoate.

'7. Double base smokeless powder grains surface coated with B-naphthyl acetate.

ELTON R. ALLISON.