US2643611A - Large grain smokeless powder - Google Patents

Description

Patented June 30, 1953 UNITED STATES ATENT OFFICE mesne assignments, to United States of America as represented by the Secretary of War No Drawing. Application November 19, 1945, Serial No. 629,710

- 1 Claim. 1

This invention relates to an improved large grain smokeless powder and more particularly to alarge grain smokeless powder having inhibitor strips adhered thereto with an improved adhesive.

Plastic strips have been glued to the surface of large grain smokeless powder in order to control the burning area and also to act as spacers to prevent the powder from contact with the motor wall. These strips have been applied to the ends of the powder grains and also to the arms of a cruciform stick of smokeless powder. Improved ballistics have been obtained by reducing the initial surface of the powder by gluing plastic inhibitor strips to the powder surface. The firmness with which the inhibitor strip is adhered to the powder is very important, since a single poorly adhered strip may seriously affect the ballistics of the weapon. It has been found that there should be no air bubbles between the strip and the powder and no crack along the edge of the strip which will permit access of the flame to the powder underneath the strip. Such defects nullify the effect of the strip. Many adhesives when spilled on the powder grain produce a slow burning area.

Now, in. accordance with this invention, it has been found that adhesives containing nitrocellulose as a thickener form a strong permanent bond between cellulose acetate or ethyl cellulose inhibitor strips and smokeless powder grains.

The following examples illustrate specific embodiments of the invention:

EXAMPLES 1-6' An ethyl cellulose inhibitor strip having a thickness of 0.1 inch and plasticized with butyl stearate was bonded to large grain smokeless powder having the following composition:

Carbon black (added) C'andelilla wax (added) 0.02

The adhesive was applied evenly to the inhibitor strip by means of a brush forming a layer about 0.075 inch thick. The adhesive composition, time to set up, and permanency of bond are given in Table I.

Table I Examples Adhesive Composition set g gggg Ethyl lactate 9s 1 {Nitrocellulose 2 900d {Ethyl lactate 99% 2 gg l g fi l 2 minutes.-. Do.

y c 050 ve 98 3 {giltlrolcellullose 2% 2 t y e osolve 99 4 lt122011111356 1% .71--.

cs1 y oxi e987 5 {Nitrocellulose 2 7: D 6" {Butyl acetate 99% Nitrocellulose 1% EXAMPLES 7-9 Inhibitor strips of 0.1 inch thickness were made having the following composition:

Percent Cellulose acetate (57% acetic acid) 74 Dibutyl phthalate 4 Diethyl phthalate 16 Dimethyl phthalate 6 These cellulose acetate inhibitor strips were adhered to cruciform powder grain having the composition given in Example 1. The adhesives were made by slowly adding screen-dried nitrocellulose to diacetone alcohol at a temperature of YO- C., while maintaining swift agitation. Table II gives the composition of the adhesive,

time to set up, the initial tackiness of the adhesive, and the permanency of the bond.

4 with the present invention may be varied considerably from the specific powder composition EXAMPLE A cellulose acetate inhibitor strip similar to that described in Examples 7-9 was adhered to large grain smokeless powder having the composition given in Example 1. The adhesive used to bond the strip to the powder consisted of 95% butyl acetate and 5% nitrocellulose having a viscosity of -20 seconds and a nitrogen content of 13.25%. The initial tackiness of the adhesive was good and no air bubbles were formed between the strip and the powder. A Strong bond was formed between the powder and the strip.

As shown in the examples, a solution containing nitrocellulose forms a strong permanent bond between large grain smokeless powder and plastic inhibitor strips. The nitrocellulose should have a viscosity between 1000 seconds and second and a nitrogen content between 11% and 13.4%. The solvents for the nitrocellulose should be softeners for the inhibitor strip and capable of setting up the bond rapidlyf Suitable solvents for use with ethyl cellulose strips include ethyl lactate, ethyl Cellosolve, methyl Cellosolve, mesityl oxide, butyl acetate, ethyl acetate, and methyl ethyl ketone. Suitable solvents for use Table II Examples Adhesive Composition Set g g g gg of The strip pulled Nitrocellulose 5% 1 7 Diacetone alcohol }6 minutes. Goodgggger after 24 i roce ose 2 9 {Diacetone alcoho l 98%.

1 Nitrocellulose had a nitrogen content of 12.58%. I 1 Nitrocellulose had a nitrogen content of 13.42%.

' 15 set forth in the examples. By proper combination of the content and type of nitrocellulose, the content and type of nonvolatile plasticizer, and the content and type of other ingredients, operable powders or considerable variety may be made. However, the present invention is primarily directed to compositions containing a substantial amount of nonvolatile plasticizer:

For example, the powder may contain from about to about 60% nitroglycerin and/or similar organic nitrate, such as diethylene glycol dinitrate or diethanol nitra nine dinitrate (di(2-nitroxyethyDnitramine), as the nonvolatile plasticizer, from 0% to about 5% inorganic salts, from about 0.5% to about 10% stabilizer, from about 0.01% to about 2.0% opaquing agent, and from about to about 65% of nitrocellulose.

with cellulose acetate inhibitor strips include' diacetone alcohol, methyl Cellosolve, ethyl Cellosolve, butyl acetate, ethyl acetate, and methyl ethyl ketone. I

The amount of nitrocellulose used will vary according to the viscosity of the nitrocellulose. Nitrocellulose in the adhesive composition should be between 1% and 10%. When the composition contains a high per cent of nitrocellulose the solvent becomes too Viscous and is difiicult to apply.

The strips may be made from either plasticized ethyl cellulose or cellulose acetate. The strips may contain between 60% and 90% of cellulose acetate or ethyl cellulose and from 40% to 10% plasticizer. The cellulose acetate used for making the strips should have an acetic acid content between 51% and 59%. Suitable plasticizers for the cellulose acetate strips include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, methyl phthalyl ethyl glycolate, p-toluene sulfonamide, p-toluene sulfonate, triacetin, tripropionin, dibutyl tartrate, and triphenyl phosphate. The ethyl cellulose, used for making strips, should have an ethoxy content between about 44% and about 49%. Suitable plasticizers for ethyl cellulose inhibitor strips include butyl stearate, mineral oils such as Fractol A, castor oil, hydrogenated terphenyl, low molecular weight polymers of styrene and substituted styrenes, coumarone-indene polymers, phthalate esters such as dioctyl phthalate, dibutyl phthalate, and chlorinated diphenyl, etc.

The powder compositions for use in accordance The large grain smokeless powder grains formed in accordance with this invention are used in jet-propelled devices, such as rockets, airplane starters, assisted take-off devices, catapult devices, gas-producing devices, and the like, including any devices which derive translational or rotational energy at least partly from the action produced from the issuance at relatively high speed of fluid medium from an opening in the device. The inhibitor strips are made from ethyl cellulose or cellulose acetate and a suitable plasticizer.

Adhesives containing nitrocellulose have the advantage that if any of the adhesive is spilled on the powder grain, it does not interfere with the burning properties of the powder. Nitrocellulose acts as a thickener for the adhesive and forms a bead at the edge of the strip. The adhesives are easily applied without the formation of air bubbles between the strip and the powder grain. They arev quick-setting and do' not adversely affect the stability of the powder.

Where, in the specification and in the appended claim, the term large gain smokeless powder is used, it is meant a smokeless powder having a web thickness of more than 0.20 inch. The web thickness is defined as the least burning thickness from the edge of one surface to the edge of another surface, regardless of the configuration of the grain.

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

A large smokeless powder grain having an inhibitor strip made of a material selected from the group consisting of ethyl cellulose and cellulose acetate tightly bound to said grain by means of an adhesive region coextensive with the covered surface of the grain, said region being formed by plasticizing a thin layer of the powder and of the strip along this surface with a composition consisting essentially of nitrocellulose dissolved in a high boiling organic compound from the group consisting of diacetone alcohol, mesityl oxide, ethyl acetate, butyl acetate and methyl Cellosolve, said organic compound acting as a mutual plasticizer for the powder and for the material of the inhibitor strip.

ALPI-IEUS M. BALL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Maxim Dec. 27, 1904 Woodbridge et a1. Sept. 20, 1920 1 Dreyfus Feb. 24, 1931 Charch Apr. 16, 1935 Keeran June 16, 1936 Holm et a1 Jan. 21, 1941 6 FOREIGN PATENTS Number Country Date 27,197 Great Britain Nov. 30, 1897 of 1896 5 502,560 France Feb. 24, 1920 OTHER REFERENCES Brady: Materials Handbook, McGraw-Hill,

Book Company, 1944, pages 6, 9 and 10.

0 in Division 30.)

(Copy Hackhs Chemical Dictionary, by J. Grant.

Third edition, The Blakiston Company, Philadelphia, Pennsylvania, page 263, 1944. Division 43, U. S. Patent Oifice.)

(Copy in