3,329,624 United States Patent Office Patented July 4, 1967 1. 2 bromine analog. oxide suitable for use in this inven 3,329,624 COMPOST ON FOR PRODUCING tion should be of a fine particle size, and preferably should William Eric Ashton, Niagara Falls, N.Y., assignor to be low in lead content, and most preferably, free of lead. Hooker Chemical Corporation, Niagara Falls, N.Y., a Very fine and very coarse zinc oxides form slower burn corporation of New York ing mixtures than the intermediate grades. The amounts No Drawing. Filed Jan. 16, 1963, Ser. No. 251,764 or proportions of moisture, carbonates, and sulfates in the 5 Claims. (C. 252-305) affect the burning rate, while the apparent den sity of the zinc oxide has no apparent effect on this rate. The present invention relates to pyrotechnic composi Commercial zinc oxides produced by either the French or tions and more particularly to smoke-generating composi 0 American process are suitable for this application. tions. The proportion of aluminum used and its particle size Chemicals in the category of screening are those can be varied within limits. The heat evolution of the which, when dispersed in air, produce a cloud of finely smoke mixture increases with increasing aluminum con divided particles of solid, liquid, or both. These are used tent, while the burning time decreases. Generally 2 to 15 to shield tactical operations or disrupt the movements of 5 percent of the smoke mixture is aluminum, but prefer the enemy. Outstanding examples of such materials are: ably, from 3.6 to 10.1 percent. Finely divided aluminum fuel oil used in "artificial ' generators, white phos causes a shorter burning time than the coarser aluminum phorus, sulfur trioxide, tetrachloride, and so powder. When the aluminum content is reduced below 5 called smokes. Each of the above-listed percent, the burning becomes erratic, and retarders such smoke-generating compositions is characterized by certain 20 as basic Zinc oxide, urea and Monastral blue dye are advantages and disadvantages in military operations, de added. pending upon the importance of such factors as mobility The preparation of of the smoke producing apparatus, toxicity, logistical con siderations, and the total obscuring power of the compo perchloropentacyclo-(5.2.1.0%6.03.9.058)-decane (CoCl2), sition employed. a white crystalline solid, is disclosed in A. N. Johnson's For military use, volatile hygroscopic chloride (HC) United States Patent No. 2,996,553 and may be summa smokes are the most important, other than oil mixtures, rized as the condensing of hexachlorocylopentadiene in which are utilized for large scale operations. The most the presence of aluminum chloride, at an elevated tem widely used HC types of smokes are those resulting in the perature. Perchloropentacyclodecane contains approxi production of zinc chloride smokes. 30 mately 71 percent and 29 percent carbon, and The original mixture employed to produce a zinc chlo has a melting point of 485 degrees centigrade. ride smoke was the Berger mixture, developed by the The prior art suggests the use of perchloropentacyclo French Army during . The original Berger decane as a fire-retardant additives in thermoplastic and mixture consisting of zinc dust and carbon tetrachloride thermoset resins which have application in the paper, with zinc oxide and diatomite. Upon ignition, a vigorous 35 paint, rubber, and electrical fields. Therefore, it is quite reaction takes place, resulting in the formation of zinc chlo surprising to find perchloropentacyclodecane also to be ride, which is volatilized by the heat of the reaction and well suited for inclusion in a composition for producing solidifies to form smoke. However, since this mixture em smoke and heat by burning. ployed a liquid organic chloride, it was difficult to trans port and store. By the beginning of World War II, the 40 The ratio of zinc oxide to perchloropentacyclodecane United States Government had developed a mixture desig may be varied within wide limits, however, it is preferable nated “HC smoke mixture' which contained zinc, a per that in all cases an amount less than the stoichiometric chlorate as an oxidizing agent, as the amount of perchloropentacyclodecane be employed. The organic chloride compound, with a retarder, ammonium reaction involved when the mix is ignited (as a “candle') chloride. Subsequently, a mixture was found which was may be shown as follows: better in many ways than the original; it was a combina 45 tion of hexachloroethane, aluminum and zinc oxide. This mixture required no stabilizer against moisture absorption, The aluminum, zinc chloride, and carbon particles so and changing the percentage of aluminum varied the burn formed all contribute to the obscuring power of the smoke. ing time, as desired. However, these compositions are The ratio of zinc oxide to perchloropentacyclodecane corrosive and will interfere with firing mechanisms, there 50 may vary from 1.2 to 1.4 parts by weight to 7 to 1 parts by materially limiting the storage life of the smoke gen by weight. Preferably the ratio employed will fall between erating composition. 1 to 1 and 4 to 1. A composition of the following parts by There have now been discovered novel smoke generat weight produces a satisfactory screening smoke: ing compositions which have improved storage stability properties, while also having the other desirable charac 55 Parts teristics needed for producing controlled and effective Perchloropentacyclodecane ------31.0 amounts of Smoke. Zinc oxide ------62.0 Accordingly, it is an object of this invention to provide Aluminum powder ------7.0 improved pyrotechnic and smoke-generating compositions. 60 Temperatures in excess of 300 and preferably above Other objects will also become apparent to those skilled 1000 degrees centigrade are necessary to initiate the reac in the art upon reference to the following detailed descrip tion of the above mixture. However, once initiated, the tions and the example. reaction is self-sustaining. The initial heat may be sup In accordance with this invention, there is provided a plied by any convenient means. smoke-generating composition comprising the compound 65 The particles of smoke vary in size from those just large perchloropentacyclo-(5.2.1.026.03.9.05.8)-decane (CoCl12), enough to be perceived by the unaided eye to those that and zinc oxide. Additionally, zinc dust, aluminum dust, approach the size of the single molecules. In general, and other modifiers may be present to moderate heat smoke particles are intermediate in size between dust par evolution. In place of the ticles (104 centimeters) and gas particles (10 centi perchloropentacyclo-(5.2.1.026.039,058)-decane 70 meters) and average about 10 centimeters in diameter. other suitable halogen derivatives may be used, e.g., the As a rule, the smaller the particles in a given quantity of 3,329,624 4. smoke, the greater is their obscuring power; hence, the 1. A composition for producing smoke wherein the aim is to generate a smoke consisting of the maximum smoke-producing halide, perhalopentacyclo-decane, is number of particles of minimum size. present in less than stoichiometric amount with zinc oxide The invention is illustrated by but not limited to the to produce smoke when said perhalopentacyclodecane and following example. All proportions are by weight and tem Zinc oxide are ignited. peratures are in degrees centigrade, unless otherwise indi 2. A process for producing an abscuring smoke which cated. comprises reacting a zinc oxide with an amount less than A Smoke screen composition was prepared by mechani the stoichiometric amount of cally blending together a composition composed of 31 perchloropentacyclo-(5.2.1.0.2, 6.03.9.058)-decane percent perchloropentacyclodecane, 62 percent zinc oxide, O and 7 percent powdered aluminum. The composition was at an elevated temperature. consolidated at a 5,000 pound dead load into the 3. A smoke generating composition comprising zinc body and topped with an ignition compound. The burning oxide, powdered aluminum, and time for this composition varied from 105 to 150 seconds, perchloropentacyclo-(5.2.1.02, 6.03.9.05.8)-decane which is within the desired burning range for smoke screen 15 . said Zinc oxide being present in more than stoichiometric When viewed from a distance of 60 yards, after burning amounts with respect to the 2 minutes and 20 seconds in a 4 to 8 mile per hour wind, perchloropentacyclo-(5.2.1.02, 6.03.9.05.8)-decane the Smoke generated by a grenade completely obscured and the powdered aluminum comprising from about 2 to more distant objects in the observer's line of sight. 20 about 15 percent of the total smoke-generating composi A determination of the particle size of the smoke tion. evolved was made, according to standard sampling tech 4. A smoke generating composition comprising zinc niques employing a multi-stage impactor. Results are tabu oxide and perchloropentacyclo-(5.2.1.02.6.03.9.05.8)-decane lated in the table below: - in the ratio of from 1.2 to 1.4 parts by weight to 7 to 1 PARTICLE SIZE DISTRIBUTION 25 parts by weight, and powdered aluminum in an amount from 2 to 15 percent by weight of the combined zinc oxide Impactor Stage Percent Particle Size and perchloropentacyclodecane. Microns (Average) 5. A composition for producing smoke comprising 10.3 30 perchloropentacyclo-(5.2.1.02.6.03.9.05.8)-decane 7.2 3.3 and Zinc oxide wherein said Zinc oxide is utilized in more 26.0 13.1 than stoichiometric quantity. 20.1 ; References Cited 35 Additional smoke grenades comprising housings con UNITED STATES PATENTS taining the test composition were tested for storage sta 1,632,339 6/1927 Kiefer ------252-305 bility. Specimen grenades were placed in hermetically 2,409,201. 10/1946 Finkelstein et al. -- 252-305 sealed containers and stored at 160 degrees Fahrenheit 2,494,454 1/1950 Ritchie ------252-305 for 90 days under high humidity conditions. At the end 40 2,574,466 11/1951 Clay ------252-305 of this test period, all units functioned satisfactorily and 2,695,258 11/1954 Johnstone et al. ------252-305 exhibited little, if any, corrosion. 2,996,553 8/1961 Johnson ------260-648 Various changes and modifications may be made in the method and apparatus of the invention, certain preferred LEON D. ROSDOL, Primary Examiner. forms of which have been herein described, without de 45 parting from the spirit and scope of the present invention. JULIUS GREENWALD, Examiner. What is claimed is: H. B. GUYNN, Assistant Examiner.