US3506505A - Nitrocellulose base propellant coated with graphite,plasticizer,and inorganic pigment - Google Patents

Description

United States Patent NITROCELLULOSE BASE PROPELLANT COATED WITH GRAPHITE, PLASTICIZER, AND INOR- GANIC PIGMENT Hermann Herzog, deceased, late of Kaufbeuren, Germany, by Johanna Herzog, heir, Kaufbeuren, and Hubert Frey, Steyerberg, Germany, assignors to Dynamit Nobel Aktiengesellschaft, Troisdorf, Germany No Drawing. Filed Dec. 1, 1967, Ser. No. 689,746

Int. Cl. C06b 19/02 US. Cl. 149-11 16 Claims ABSTRACT OF THE DISCLOSURE The present disclosure relates a a propellant charge powder having a nitrocellulose base wherein the grains of the powder are coated with a plasticizer, graphite, and at least one inorganic pigment. Particular advantages are gained with an inorganic pigment from the group consisting of metal oxides and metal sulfides, with specifically advantageous examples being iron oxide, molybdenum sulfide, titanium dioxide, or zinc oxide, within the range of 0.1 to 1.0 percent by weight of the charge.

When a particularly high effectiveness is required for a propellant charge powder, nitrocellulose base propellant charge powder is conventionally manufactured in the form of a loose powder. In this condition, it is necessary to treat the loose powder with a plasticizer, for example, dibutylphthalate, or another coating agent, for example, symmetrical diethyldiphenylurea, in such a manner that the outermost layer of the powder granules is impregnated by this plasticizer or coating substance. This treatment, called stabilization, will slow down the initial combustion of the powder to a predetermined degree and consequently influence the progression of powder combustion. Also, this treatment, with the addition of a polishing agent, will advantageously smooth the surface of the powder granules so that a higher cubic weight, that is density, is obtained. Also, the calorific content of the powder may be advantageously reduced.

The above-mentioned powder treatment is usually conducted in a steep angle or vertical drum, with the treating substance dissolved in an organic solvent, such as ethyl alcohol, which does not dissolve the nitrocellulose. The solvent is applied to the powder simultaneously with the addition of graphite so that the powder will have a smoothly polished surface when the treatment is terminated.

However, experience has shown that the above-described treatment may under certain circumstances cause an undesirable and intolerable delay in the firing of the powder. The delay in firing increases with the amount of stabilizer added; the delay in firing being defined as the time from the instant of firing the primer composition to the actual firing of the powder. A too long delay in firing time must be avoided at all cost. This disadvantage of the prior art is more apparent the smaller the ratio of surface to mass of the powder granule.

An additional disadvantage occurring during the abovementioned treatment is that the graphite may form nodules to produce a non-uniform and unsatisfactory product, because of the poor wettability of the graphite.

It is known to overcome the firing delay disadvantage by adding ground aluminum or magnesium powder during the treatment, because these additives have the effect of imparting to the stabilized surfaces of the powder granules a greater ignition tendency. To further this sensitivity effect, it is also known to add saltpeter or other oxygen-evolving substances to the powder during the treatment thereof.

3,506,505 Patented Apr. 14, 1970 Also, it is necessary to remove the residues of the solvent after the stabilizing treatment with a water treatment of the stabilizer-treated loose powders at high temperatures. However, the sensitivity of aluminum or magnesium to water has a very disadvantageous effect upon the stability of the powder, while the addition of saltpeter or other oxygen evolving water soluble salts is completely out of the question because of the subsequent water treatment. Therefore, solutions by the addition of ground aluminum or magnesium powder and the addition of saltpeter or similarly effective substances has proven to be unsatisfactory.

It is an object of the present invention to avoid the above-mentioned disadvantages. The present invention employs particular additives to prevent the formation of graphite nodules during the powder treatment, to increase the ignition sensitivity that would otherwise be reduced by the addition of a stabilizer and provide for the subsequent water removal of solvent residues without adversely affecting the treated powder.

According to the present invention, inorganic pigments, particularly metallic oxides and metallic sulfides are added during the surface treatment of the powder with a stabilizing agent. Particularly advantageous results have been obtained with inorganic pigments such as iron oxide (ferric oxide or ferrous oxide), molybdenum sulfide, titanium dioxide, zinc oxide, iron sulfide, or zinc sulfide, in an amount corresponding to desired degree of ignition sensitivity, preferably between 0.1 and 1.0 percent by weight of the charge.

The above noted substances added according to the present invention are known by the commercial names of polishing rouge, Molykote, titanium white (titania), and zinc white. These substances are particularly suitable because they are excellent polishing agents due to their good wettability and moreover increase, in mixture with graphite, the ignition tendency of the powder, which would otherwise be decreased by the stabilizer addition. With such an increase in the ignition tendency, the period from the ignition of the primer to the actual initial firing of the powder may be adapted to the particular requirements. Also, the substances added by the present invention reduce the moisture sensitivity of the resulting powder in an advantageous manner.

The resulting propellant powder may be used in a cartridge case for propelling a projectile out of the barrel of a weapon, or as a propellant in a rocket.

Although it is known to add the known treating agents, including graphite in a batch-wise manner, it is a particular feature of the present invention to add the inorganic additives of the present invention in a batch-wise manner to the nitrocellulose base powder to obtain as uniform a distribution of the additives in the powder as possible.

The advantages of the present invention in adding the abovementioned mineral or inorganic additives to the nitrocellulose base powder can be seen, for example, from the fact that a nitrocellulose-7-hole powder treated with 4% camphor and 0.2% graphite on its surface attained a ballistic velocity of 1.151 milliseconds at a gas pressure of 2929 atmospheres and a firing development period of 2.9 milliseconds, whereas when using nitrocellulose-7* hole powder surface treated with 4% camphor, 0.1% graphite, and 1.0% titanium white, there was attained a ballistic velocity of 1,167 milliseconds at a gas pressure of 3102 atmospheres and with a firing development period of only 1.9 milliseconds. The above test brings out the advantages of the present invention by comparing the known surface treatment of a specific powder with the surface treatment according to the present invention of the same specific powder. The expression 7-hole powder mentioned above refers to granulate powder in cylinder form which is provided with 7 holes or bores extending in the longitudinal direction and distributed symmetrically over the cross section of said cylinder for the purpose of increasing the burning surfaces of the powder.

As was demonstrated by additional tests, a substantial improvement is still achieved even when a lesser amount of titanium white is used.

The lowering of the moisture sensitivity of the powder due to the addition of the mineral additives according to the present invention can be seen from the fact that when a nitrocellulose-7-hole powder is stored at a relative atmospheric humidity of, for example, 35 and 91%, which powder was surface-treated with 6% camphor and 0.2% graphite, there is also a difference in the H content of 1.0%, whereas the same nitrocellulose-7-hole powder when treated with 6% camphor, 0.1% graphite, and 1.0% titanium white, at a difference in H O of only 0.94%. The above test comparing the moisture sensitivity of a specific powder treated according to the known treatments and the moisture sensitivity of the same powder treated according to the present invention bring out the advantages of the present invention in this regard.

The specific and highly advantageous results have been obtained with the additives iron oxide, molybdenum sulfide, titanium dioxide, or zinc oxide when within the range of 0.1 to 1.0% by weight of the charge.

The foregoing specific embodiments have been described in detail along with their specific advantages as preferred embodiments of the broader invention, and further modifications, embodiments and variations of the present invention are contemplated within the spirit and scope of the invention as defined by the following claims.

We claim:

1. A process for influencing the ignition sensitivity of a nitrocellulose base propellant charge powder which comprises coating the surfaces of the propellant powder with a plasticizer, graphite and an inorganic pigment selected from the group consisting of metallic oxides and metallic sulfides, said inorganic pigment being added in an amount sufficient to achieve the desired degree of firing sensitivity.

2. The process of claim 1, wherein the inorganic pigment is added in an amount of about 0.1 to 1.0% by Weight of the charge.

3. The process of claim 1, wherein the inorganic pigment is selected from the group consisting of ferrous oxide, ferric oxide, titanium dioxide, zinc oxide, molybdenum sulfide, iron sulfide and zinc sulfide.

4. A process for increasing the ignitability of a propellant charge powder consisting essentially of nitrocellulose which comprises coating the surfaces of the propellant powder with a mixture of a plasticizer, graphite and an inorganic pigment selected from the group consisting of metallic oxides and metallic sulfides, said inorganic pigment being added in an amount of about 0.1 to 1.0% by weight of the charge.

5. The process of claim 4, wherein the coating step increases the concentration of flammable substances on the surface of the propellant powder.

6. The process of claim 4, wherein the inorganic pigspectively.

9. The process of claim 1, wherein the coating step includes adding the plasticizer, graphite and inorganic pigment by batch-wise addition.

10. A propellant charge consisting essentially of a nitrocellulose base propellant charge powder coated with a plasticizer, graphite and an inorganic pigment selected from the group consisting of metallic oxides and metallic sulfides, said inorganic pigment being present in an amount sufiicient to achieve the desired degree of firing sensitivity.

11. The propellant charge of claim 10, wherein the inOrganic pigment is present in an amount of about 0.1 to 1.0% by weight of the charge.

12. The propellant charge of claim 10, wherein the inorganic pigment is selected from the group consisting of ferrous oxide, ferric oxide, titanium dioxide, Zinc oxide, molybdenum sulfide, iron sulfide and zinc sulfide.

13. A propellant charge with increased ignitability which consists essentially of nitrocellulose powder coated with a mixture of a plasticizer, graphite, and an inorganic pigment selected from the group consisting of metallic oxides and metallic sulfides, said inorganic pigment being present in an amount of about 0.1 to 1.0% by weight of the charge.

14. The propellant charge of claim 13, wherein the inorganic pigment is selected from the group consisting of iron oxide, titanium dioxide, zinc oxide and molybdenum sulfide.

.15. The propellant charge of claim 13, wherein the propellant charge is nitrocellulose powder and the plasticizer is camphor.

16. The propellant of claim 15, wherein the camphor and graphite are present in amount of about 4% and about 0.1%, respectively.

References Cited UNITED STATES PATENTS 692,143 1/1902 Jones 1499 693,547 2/1902 Jones 1499 1,354,442 9/1920 Woodbridge et a1 149-9 1,390,740 9/1921 Woodbridge 1499 1,393,623 10/1921 Henning 1499 2,131,354 9/1938 Marsh 149--9 2,865,729 12/1958 Foster et al 149-9 CARL D. QUARFORTH, Primary Examiner S. J. LECHERT. JR., Assistant Examiner US. Cl. X.R. 149-9, 10,