Smoke generating compositions and methods of making the same

Details Smoke generating compositions and methods of making the same Smoke generating compositions and methods of making the same

2001-07-24

2003-05-06

Metzmaier, Daniel S. (Department: 1712)

Explosive and thermic compositions or charges

Structure or arrangement of component or product

Solid particles dispersed in solid solution or matrix

C149S019700, C149S083000, C149S084000, C149S117000, C516S002000

Reexamination Certificate

active

06558487

ABSTRACT:

FIELD OF THE INVENTION
The present invention is generally directed to smoke generating compositions and methods of making the same in which a polysaccharide such as polymerized sucrose is used as a binder.
BACKGROUND OF THE INVENTION
Smoke generating compositions which can be used by the military to produce white or colored smoke typically contain a formulation for generating smoke often including a monosaccharide or disaccharide (e.g. sucrose) as a fuel, and a binder for maintaining the smoke generating formulation, typically in the form of a mixture of smoke generating materials in a compact form so that it may be used in the production of, for example, smoke generating grenades.
The binder typically used in smoke generating compositions of this type is polyvinyl alcohol. The polyvinyl alcohol is dissolved to provide a liquid capable of being sprayed onto the components of the smoke generating formulation which are in the form of dry mix granules. The spraying typically takes place in a fluidized bed. The binder assists in forming particles of the smoke generating formulation or mixes and allows the mixes to consolidate to thereby form pellets. The pellets can then be incorporated into smoke generating devices such as grenades.
Polyvinyl alcohol is problematical as a binder for forming smoke generating compositions because it tends to cross-link adjacent polymer chains or branches of the same polymer chain. Cross-linking of polyvinyl alcohol in this manner often results in a cross-linked material which sticks to the equipment used to make and transfer the polyvinyl alcohol solution.
The formation of layers of the polyvinyl alcohol material on various equipment including double jacket steam reactors can adversely affect heat transfer. In addition, the presence of the cross-linked material in the flow system and spray system can create pressure head and actually block the nozzles of the spray system. Prepared solutions of polyvinyl alcohol dissolved in a solvent require continuous heating and agitation to avoid solidification of the polyvinyl alcohol material. Once solidified polyvinyl alcohol will not re-dissolve in the original solvent or in any other organic solvent and thus loses its function as a binder. Thus, when polyvinyl alcohol is used as a binder maintenance requirements are high.
Polyvinyl alcohol also adversely effects the efficiency of the smoke generating composition to generate smoke. Polyvinyl alcohol creates about 30% of compact ash when the smoke generating material is ignited. The compact ash prevents some of the smoke generating materials from functioning properly and thereby reduces the output of the smoke generating device.
Other problems associated with the use of polyvinyl alcohol as a binder is its high cost, the possibility that it may be carcinogenic and the possibility that it is responsible, at least in part, for wide variation in burn times for smoke generating grenades operating in hot and cold environments. The wide variation in burn times affects smoke quality and thus leads to wide variations in smoke quality over a range of operating temperatures.
It would therefore be a significant advance in the art of producing smoke generating compositions including those that may be used in military devices such as smoke grenades to eliminate polyvinyl alcohol as a binder. It would be a further advance in the art to employ a binder for a smoke generating composition which eliminates or at least reduces the problems associated with polyvinyl alcohol.
SUMMARY OF THE INVENTION
The present invention is generally directed to a smoke generating composition in which polyvinyl alcohol is no longer used as a binder but is replaced by a polymerized monosaccharide or disaccharide.
In a particular aspect of the present invention, there is provided a smoke generating composition comprising:
a) at least one smoke generating material; and
b) a binder comprising a polymerized monosaccharide or disaccharide.
In a further aspect of the present invention, a portion of the monosaccharide or disaccharide is polymerized to form the binder which reduces the cost of the smoke generating device and eliminates the use of a binder which heretofore has caused significant problems with the production of smoke generating compositions.
In a further aspect of the present invention, there is provided a method of producing a smoke generating composition comprising treating at least one smoke generating material with an effective amount of a binder in the form of a polymerized monosaccharide or disaccharide.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is generally directed to a smoke generating composition and method of preparing the same in which a polymerized monosaccharide or disaccharide is employed as a binder.
Although any monosaccharide or disaccharide may be employed in the present invention, a clearly preferred embodiment is the use of polymerized sucrose because sucrose is typically used as one of the smoke generating materials (i.e. as a fuel). A part of the sucrose is first polymerized and then dissolved in water and sprayed over the smoke generating materials.
The polymerized monosaccharide or disaccharide binder is particularly effective for smoke generating compositions because it is water soluble and easily sprayed over the smoke generating materials. As the monosaccharide or disaccharide is polymerized, it does not lose its original function as a fuel within the smoke generating composition. Thus, the polymerized monosaccharide or disaccharide serves a dual purpose of being both a binder and a fuel to provide a more efficient smoke generating composition.
The binder of the present invention is prepared by polymerizing a monosaccharide or disaccharide (e.g. sucrose) in the presence of an acid catalyst, preferably under vacuum at a temperature typically in a range of from about 60 to 120° C., most preferably about 80° C. There are a variety of catalysts that may be used for this purpose, including but not limited to, p-toluene sulfonic acid and sulfuric acid. The reaction typically takes place at a mass ratio of monosaccharide or disaccharide:acid catalyst:water of from about 1:0.001:0.04 to 1:0.01:0.15, most preferably a mass ratio of about 1:0.005:0.1.
The polymerization process is preferably conducted under agitation and reduced pressure of from about 200 to 700 mmHg, most preferably about 400 mmHg. The polymerization process typically takes from about 1 to 6 hours, depending in part on the mass ratio, temperature and pressure employed in the polymerization process.
Smoke generating materials are generally known in the art and include, for example, magnesium carbonate, potassium chlorate and monosaccharides and disaccharides (e.g.sucrose) as a fuel. The amount of monosaccharide or disaccharide is typically from about 13 to 18% by weight of the smoke generating composition. In the preparation of white smoke generating compositions, terephthalic acid alone or in combination with pentaerythritol is used in combination with magnesium carbonate and potassium chlorate. Stearic acid may be used as an optional component. In the preparation of colored smoke generating compositions, potassium chlorate, magnesium carbonate and sucrose are typically combined with a dye such as solvent yellow 33 (for the production of yellow smoke) and solvent yellow 33 combined with solvent green 3 (for the production of green smoke).
The preparation of white smoke generating compositions in accordance with the present invention is prepared by combining a first composition containing 70 to 100% by weight of terephthalic acid alone or in combination with 0 to 30% by weight of pentaerythritol. The first composition prepared above is combined with magnesium carbonate, potassium chlorate, optionally stearic acid, and sucrose to form a white smoke generating composition. From about 12% to 100%, preferably from about 15% to 50% of the monosaccharide or disaccharide (e.g. sucrose) employed in the smoke generating composition will be polymerized in accordance with the present invention to

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