Field of the Invention

The present invention relates to the field of the desensitization of chemical materials. More particularly, the invention relates to a method for desensitizing potassium nitrate. Still more particularly, the invention relates to a method for preventing the use of the fertilizer potassium nitrate for the production of gun powder or other energetic materials.

Background of the Invention

Potassium nitrate is a widespread fertilizer, manufactured and sold all over the world. While potassium nitrate is a valuable nutrient for crops, it is also found in various energetic mixtures such as gun powder that can be used to propel cartridges and in general energetic materials, by the simple addition of readily available additives, such as coal powder and sulfur.

It is an object of the present invention to provide a method which permits to desensitize potassium nitrate in a simple and cost-effective manner.

It is another object of the invention to provide desensitized potassium nitrate mixtures, which can be efficiently used for regular agricultural uses, inasmuch as they do not contain additives that are- harmful to crops or to the environment, or which are too expensive to be used in agricultural applications. Desensitized potassium nitrate can be easily shipped without the need for special cautions against unwanted explosion.

Summary of the Invention

In one aspect the invention is directed to a desensitized potassium nitrate product comprising as a desensitizing agent at least one additive selected from among scavengers that are reactive with the nitrate moiety, or a flame retardant compound, or a mixture of two or more of said additives.

According to a preferred embodiment of the invention the scavenger is chosen from among the nitrate scavengers group - for example urea. According to another preferred embodiment of the invention the flame retardant is chosen from among groups of halocarbon, hydrate, phosphate or borate flame retardants - for example magnesium sulfate, ammonium phosphate or boric acid

The desensitizing agent comprises up to 15% by weight as related to potassium nitrate, preferably 5-10%. While the addition of higher amounts of additive may further desensitize the resulting mixture, there is a balance between cost and effect, and procesability considerations. Accordingly, for many applications it is sufficient that the additive be present in an amount of up to 10% by weight of the potassium nitrate. The skilled person would be able to determine the optimal amount for his specific requirements, in each case.

The invention further encompasses a desensitized potassium nitrate product comprising as a desensitizing agent at least one additive selected from among scavengers that are reactive with the nitrate moiety, or a flame retardant compound, or a mixture of two or more of said additives.

In another aspect the invention is directed to a method for desensitizing a potassium nitrate product, comprising adding to said potassium nitrate product a desensitizing agent additive selected from among oxygen scavengers that are reactive with the nitrate moiety, or a flame retardant compound, or a mixture of two or more of said additives.

Potassium nitrate may be used in the preparation of various harmful materials. One example of such dangerous products is gunpowder. When used to manufacture gunpowder, the mixture is typically made of 75% potassium nitrate, 15% coal and 10% sulfur.

The above and other characteristics and advantages of the invention will be further understood through the following description of illustrative and non-limitative examples. - A -

Detailed Description of the Preferred Embodiments

The invention will be illustrated with reference to the following specific examples. In the examples to follow the sensitivity of various desensitized compositions was compared with a composition to which no desensitizing additives have been added. The results clearly show that potassium nitrate can be desensitized within the framework of the environmental requirements described above.

Example 1

Various compositions were prepared from the basic mixture of 75% potassium nitrate, 15% coal and 10% sulfur. A desensitizing additive comprising 10% by weight was mixed with potassium nitrate prior to preparation of the mixture, except for the basic mixture. All percentages mentioned herein are by weight. The impact sensitivity of the various mixtures was estimated using the BAM drop-hammer impact test. The impact energy is determined by the following equation, where M is the mass of the drop weight, H is the height from which the weight is being dropped and g is gravitational acceleration:

Im pact energy (J)

The H ₅₀ value (the height from which 50% of the samples explode) was determined according to the Bruceton method, using a 5Kg weight (according to B. T. Fedoroff; O. E. Sheffield;G., ENCYCLOPEDIA OF EXPLOSIVES AND RELATED ITEMS, vol. 5, New Jersey, USA, 1972, p.p. D1550-1555). This method available for testing gunpowder sensitivity allows for an experimental error of up to 20%. Accordingly, results within this experiment error are considered to be of the same kind.

The results are detailed in Table I below.

Table I

From the results shown above it is clear that an amount of up to 10% of additive should be added, to ensure a lack of sensitivity to impact above 250 cm. Of course, somewhat lower amounts can be used, and the skilled person we be able to determine the optimal amount for his specific requirements, in each case.

The above description and examples have been provided for the purpose of illustration and are not intended to limit the invention in any way. Many different combinations of mixtures and of additives can be used to desensitize potassium nitrate, according to the method described herein, without exceeding its scope.