US2798799A - Smoke-producing composition - Google Patents

Description

July 9, 1957 M. M. woYsKx ET AL 7 SMOKE-PRODUCING COMPOSITION Filed Jan. l5, 1945 United States "Patent O 2,798,799 p sMoKE-PnonnclNG CoMPosrrroN Mark M. Woyski and Elmer A.l Ford, Urbana, Ill., as-

signors to the United States of America as represented by the Secretary of War Application January 15, 1945, Serial No. 572,943

6 Claims. (Cl. 527-23) The invention described herein may be manufactured fand used by or for the Government, for governmental purposes, without the payment to us of any royalty thereon.

This invention relates to a filling for munitions and a process for preparing same. More particularly, this invention has reference to a new phosphorus filling for munitions such as bombs, shells, grenades, rockets and the like.

Standard phosphorus munitions lled with solid white phosphorus are known to be effective weapons for producing smoke screens. However, munitions of this character are inefficient in the performance `of all of their functions. In the burst of a standard phosphorus lled shell or other munition a large percentage of the phosphorus is fragmented into minute pieces with the result that it burns in a very limited atmospheric region to form a concentrated and intensely hot cloud of low density which rises from the ground in the phenomenon known :as pillaring. Only a comparatively small number of larger pieces of phosphorus are formed and these burn rapidly while traveling through the air. Only a small number of pieces of suflcient size to be casualty producing reach the ground. Consequently, a major proportion of the smoke produced by a standard phosphorus munition rises above the surface `of the ground in the form of a cloud and much of the smoke is thus not :available to perform its screening function. Likewise, a considerable portion of the phosphorus is not capable of being casualty producing since the small particles burn themselves out in their ight through the air.

The inefficiency of white phosphorus munitions has been found to be primarily attributable to the properties of white phosphorus itself. Thus the brittleness and low strength of solid white phosphorus cause it to be fragmented into finely divided particles in the burst. This, in combination with the low melting point `of white phosphorus, causes a rapid loss of the phosphorus While the small burning fragments are traveling through the air. Also, the high heat of combustion of white phosphorus is conducive to pillaring.

Accordingly, it is one object of this invention to provide a filling for a phosphorus munition which will tend to minimize pillaring.

A further object of this invention is the provision of a process of forming a substantially non-pillaring smoke screen with a white phosphorus munition.

A further `object of this invention is the provision of a filling for a phosphorus munition which tends to increase the casualty producing effects of the munition.

An additional object of this invention is the provision of `a plastic filling for a phosphorus munition which is stable at `ordinary temperatures above and below the melting point of White phosphorus.

An additional object of this invention is the provision of a filling for a phosphorus munition which may be easily prepared :and readily introduced into any standard phosphorus munition.

2,798,79 Patented July 9, 1957 A still further object `of this invention is the provision of a process for producing a new phosphorus filling for a munition.

Further and additional objects will appear from the following description, the accompanying drawing and appended claims.

In accordance with this invention, a filling for a phosphorus munition is provided which comprises :a plastic mixture of phosphorus and a plastic material. Preferably the mixture comprises a major proportion of white phosphorus and a minor proportion of the plastic substance and the two ingredients are thoroughly incorporated, one with the other, to produce a relatively stiff, doughy or gel-like mass which may be readily introduced into any of the ordinary phosphorus munitions such as bombs, shells, grenades, rockets and the like. Upon the bursting of a munition of this character (which is provided with a high explosive burster charge) relatively large fragments of the plastic mixture are thrown into the air and these large fragments are scattered about in much the same manner as the finely divided particles formed during the bursting of a munition containing `ordinary white phosphorus. Inasmuch as a major proportion of the white phosphorus filling of this invention is in the form of large fragments, these fragments burn for a long period of time. Most of the fragments are scattered about on the ground and continue to burn for some time. The surfaces of the burning fragments of this character are very sticky and therefore have a high casualty producing value.v Likewise, the dissemination of the white phosphorus in the form of large fragments minimizes the amount of heat formed inthe immediate vicinity of the munition and, accordingly, the phosphorus smoke does not have a tendency to pillar. This pillaring effect having been minimized, the phosphorus smoke stays relatively close to the ground and will be carried downwind providing excellent screening for a considerable distance.

lt will be apparent from the foregoing that the choice of :a plastic material for plasticizing the white phosphorus may be dependent, in a large measure, upon the particular properties that are desired of the filling. Ordinarily the fragmentation properties of the lling are dependent upon the consistency of the White phosphorus mixture. In order to provide a lling having tough, doughy properties it has beenfound desirable to employ synthetic or natural rubber as the plasticizing agent. The white phosphorus in a fine granular state is preferably admixed with the rubber in any suitable mill in such a manner that the rubber serves to coat and adhere together the individual particles of white phosphorus. In order that the rubber or other plastic may be readily incorporated with the white phosphorus it is preferable to solubilize the rubber with a suitable solvent such as xylene, tetrachloroethane, lorthodichlorobenzene or suitable solvent. In general, howeuer, the hydrocarbon solvents (such as xylene) are to be preferred for this purpose. The resulting mixture, when properly prepared, is stable and does not tend to separate at ordinary temperatures above or below the melting point of the white phosphorus.

The consistency of the filling may readily be controlled by proper selection of the kind and amount of plasticizer employed. Likewise, the burning rate of the mixture can be so controlled, the more plasticizer used the slower the burning rate. Also the consistency and burning rate may be decreased by adding asbestos fibers, wood bers or other particulate material. Red phosphorus particles have been found to be useful for this purpose since the red phosphorus is not inert in the mixture and up to 40% tends to increase the stiffness of the mixture above the melting point of the white phosphorus.

In accordance with one embodiment of this invention, the solvent for the rubber or other plastic material may comprise, in whole or in part, a polymerizable liquid monomer of a synthetic plastic such as a styrene or methylmethacrylate resin. Fillings of this type may then be formed in a more or less liquid Vform and caused to harden after having been introduced into the desired munition. In these instances it is generally desirable to add small quantities of a catalyst such as benzoyl peroxide to catalyze the polymerization reaction. Likewise, it may be desirable to employ a certain percentage of an inert unpolymerizable solvent suchl asxylene or other hydrocarbon. The presence of an inert solvent of this character tends to impart plastic properties to the resulting mass thus insuring that the mass will not fragment into fine particles upon bursting of the munition.

The plastic filling of this invention preferably comprises predominantly granulated white phosphorus having a relatively Vminor quantity of plasticizer admixed therewith and to which certain fillers may or may not be added. As indicated above, the plasticizer preferably comprises natural or synthetic rubber dissolved in a quantity of a suitable solvent therefor. The preferred ranges within which these substances may be present in the filling are in the following ratios in parts by weight:

White phosphorus `65 to 85 Rubber plastic 2 to 14 Rubber solvent 8 to 33 It will be readily apparent that the composition may be varied within wide ranges in order to obtain a filling having any desired degree of stiffness. For example, a very stiff mass had the following composition by weight:

White phosphorus 75.0 Buna-S rubber 11.2 Xylene 13.8

A semi-fluid mass containing more solvent but less rubber had the following composition:

White phosphorus 75.0 Buna-S rubber 7.5 Xylene 17.5

A more or less gelatinous mass with high elasticity and tensile strength had the following composition:

Percent White phosphorus 68.5 G-15 (a high gel rubber) 4.1 Xylene 27.1

As indicated in the foregoing, suitable plastic llings may be prepared using natural rubber or such synthetic rubber as certain types of butadiene styrene copolymer rubbers (e.g. Buna-S). Likewise, -it will be apparent that other rubbers, elastomers and plastic substances may be used which will impart the desired properties to white phosphorus granules when incorporated Vtherewith in the manner to be `hereinafter described. Y A i A suitable composition prepared in accordance with one embodiment of this invention having a polymerizable solvent may have the following general 'formular 75% granulated white phosphorus (by weight) 25% plasticizer of the Ycomposition-- 35% Buna-S rubber v -65% methylmetharylate or styrene monomer 65-.0% inert solvent (Xylene) 0.065% benzoyl peroxide (catalyst) Methylmethacrylate materials polymerize at a rapid rate. At 25 C. the final state is attained in from 36 to 48'hours and at 50 C. only 8 to l2 hours are required. The product with no inert solvent is characterized by toughness and high elasticity. VOn the other hand, styrene mixtures polymerize more slowly and to 6 days are required at room temperature, the rate of polymerization not being greatly accelerated by raising the .temperature to 509 C. Polystyrene materials tend to be brittle. However, the

addition of a few percent of Xylene or other inert solvent tends to make the resulting mass tougher and less brittle.

It should be noted that certain rubbers are prepared with an anti-oxidant .additive which tends to inhibit the polymerization of the monomers even in the presence of the benzoyl peroxide catalyst. With rubbers of this type it is usually desirable to extract them with acetone or other suitable solvent in order to remove these antioxidants.

A large number of compositions prepared in accordance with this invention have been tested in standard phosphorus munitions such as bombs, shells and grenades.

It has been found that in all cases the amount of pillaring in such munitions has been very greatly reduced and almost entirely eliminated in most cases. Therefore, by the use of the present invention, the screening efficiency of white phosphorus munitions has been very materially increased by the use of the plastic filling of this invention. Likewise, the antipersonnel effect of the munition has been increased in accordance with this invention since most of the filling is scattered and forms large casualty producing fragments which do not have the tendency to burn out entirely in the air. Likewise, it has been found that the plasticized phosphorus of this invention is quite stable upon storage at ordinary temperatures above or below the melting point of the white phosphorus.

" In order to enable one skilled in the art to practice this l invention there is here described one method and form of apparatus for preparing the plastic material. Reference is made to the accompanying drawing which shows schematically an apparatus wherein the composition of this invention may be prepared.

' The apparatus comprises a water jacketed melt tank 2, a white phosphorus granulator 4, a jacketed rubber plasticizing chamber 6, a plasticized rubber storage tank 3i, a mixer 10, and an extruder 12. Solid white phosphorus is fed into the melt tank 2 which is partially filled with water. The water and phosphorus is then heated by the hot water in the jacket 14. The melted phosphorus is then forced by hot water pumped into the melt tank 2 b y a pump .16 to the granulator 4 through a conduit 18 extending from the bottom of the melt tank 2. Means, not shown, may be provided for preheating the conduit 18 prior to the passage of the white phosphorus therethrough andV for subsequently removing the white phosphorus therefrom after the ow has been cut oit, thereby preventing vsolidified white phosphorus from plugging the conduit.

. Granulation of the white phosphorus in the granulator 4 is accomplished by rapidly stirring a mixture of water molten white phosphorus by an agitator 20 and at the time introducing cold water through a conduit 22. Ice may be added to the granulator if desired. In order to obtain the best results, the mixture is cooled and stirred rapidly to permit the formation of individual solid white phosphorus 'granules having a particle size of the order of 0.5 mm. diameter.

The resulting slurry of granular white phosphorus and water is pumped through a slurry line 24 to the mixer 10, into which is also introduced a solution of rubber and solvent from the storage tank 8 through a screw feed 26. (This solution or plasticizer for the white phosphorus is preparedy in the plasticizer 6 by agitating the rubber and solvent at any desired solubilizing temperature which latter may be controlled by a heating and cooling jacket 27.) The mixer 10 provides a strong sheering and kneading action to permit the white phosphorus to be thoroughly incorporated into the relatively stiff rubber solution. During this operation a portion of the Water initially introduced with the white phosphorus slurry has a tendency to separate and is drained off by any suitable means (not shown). The resulting product passes from l The consistency of the final product may be affected byV the amount of working that is imparted to the rubber in the plasticizer 6 and the mixer 10. Ordinarily the rubber should not be sheered excessively since it has a tendency to break down.

In the foregoing it was indicated that water be used as the fluid in the granulation process. It will be apparent, however, that other fluids can be used if desired'. Xylene has been `found to be satisfactory for this purpose, however, xylene is not entirely desirable since it tends to dilute the plasticized rubber introduced into the mixer 10, thus rendering the resulting product somewhat too fluid unless the excess xylene is removed by evaporation or other means. The use of water is preferred however and, when used, a certain amount will be present in the final product. Water has a tendency to slow down the burning rate to some extent.

It will be apparent that the above indicated process readily lends itself to the continuous -manufacture of the plasticized filling of this invention. Also, it will be evident that other plastic materials and solvents (inert and polymerizable), as well as particulate fillers as above suggested, may be employed in the process disclosed to prepare the desired filling.

It will be readily apparent to one skilled in the art that many modifications of the filling and process described in the foregoing may be made without departing from the spirit and scope of this invention. Accordingly, it is intended that this invention be limited only by the scope of the appended claims.

We claim:

1. An incendiary, anti-personnel and smoke producing filling for munitions consisting essentially of an intimate mixture of from 65% to 85% by weight of granular white phosphorus, from 2% to 14% of a rubber plastic and from 8% to 33% of a solvent for rubber selected from the group consisting of xylene, polymerized styrene, polymerized methyl methacrylate, polymerized mixtures of xylene and styrene and polymerized mixtures of xylene and methyl methacrylate.

2. A filling as defined in claim 1 wherein said solvent consists essentially of xylene.

3. A filling as defined in claim l wherein said rubber plastic is a butadiene-styrene copolymer rubber, and said solvent consists essentially of xylene.

4. An incendiary, anti-personnel and smoke producing filling for munitions consisting essentially of an intimate mixture of about by weight of granular white phosphorus, about 7.5% by weight of butadiene-styrene copolymer rubber and about 17.5% by Weight of xylene.

5. A filling as defined in claim 1, wherein said solvent is a mixture of styrene and xylene, said styrene being polymerized.

6. A filling as defined in claim 5 wherein said solvent contains benzoyl peroxide as a polymerization catalyst.

References Cited in the file of this patent UNITED STATES PATENTS 1,329,443 Thomas Feb. 3, 1920 1,713,055 Smith May 14, 1929 1,863,517 White June 14, 1932 2,149,694 Vollrath Mar. 7, 1939 2,445,312 Cooke et al. Iuly 20, 1948 2,574,466 Clay et al Nov. 13, 1951 2,586,801 Epler et al Feb. 26, 1952 2,589,129 Ponder et al Mar. 11, 1952 FOREIGN PATENTS 7,314 Great Britain T of 1915 269,979 Great Britain Apr. 27, 1927 OTHER REFERENCES Journal of the Society of Arts, vol. 2, 1853-54, pages 827-9.

Fire From the Air, Zanetti, Columbia Univ. Press, New York (1942), pages 18-24.

Claims (1)

1. AN INCENDIARY, ANTI-PERSONNEL AND SMOKE PRODUCING FILLING FOR MUNITIONS CONSISTING ESSENTIALLY OF AN INTIMATETE MIXTURE OF FROM 65% TO 85% BY WEIGHT OF GRANULAR WHITE PHOSPHORUS, FROM 2% TO 14% OF A RUBBER SELECTED FROM FROM 8% TO 33% OF A SOLVENT FOR RUBBER SELECTED FROM THE GROUP CONSISTING OF XYLENE, POLYMERIZED STRENE, POLYMERIZED METHYL METHACRYLATE, POLYMERIZED MIXTURES OF XYLENE AND STYRENE AND POLYMERIZED MIXTURES OF XYLENE AND METHYL METHACRYLATE.

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