Pyrotechnic Grains of Large Dimensions, and Their Production and Use

Abstract

The present invention provides pyrotechnic grains of composition comprising at least one oxidizing charge and at least one reducing charge and no binder. In characteristic manner, said grains are in the form of substantially cylindrical blocks: with a thickness of more than 5 mm; with an equivalent diameter of 10 mm or more; and with porosity in the range 1% to 8%, limits included. Said grains, advantageously based on guanidine nitrate and basic copper nitrate, are suitable for the slow, low-pressure generation of gas over an extended period.

1 . A pyrotechnic grain, the composition of which comprises at least one oxidizing charge selected from ammonium, potassium, sodium, barium, strontium, and basic copper nitrates, and ammonium, potassium, and sodium perchlorates, and mixtures thereof;
 at least one reducing charge selected from nitroguanidine, guanidine nitrate, and mixtures thereof; and   no binder,   wherein it is in the form of a substantially cylindrical block:
 with a thickness of more than 5 mm; 
 with an equivalent diameter of 10 mm or more; and 
 with porosity in the range 1% to 8%, limits included. 
   
   
   
       2 . The pyrotechnic grain according to  claim 1 , wherein the thickness of said block is 7.5 mm or more and/or the equivalent diameter of said block is 20 mm or more. 
   
   
       3 . The pyrotechnic grain according to  claim 1 , wherein the thickness and/or equivalent diameter of said block is in the range 10 mm to 60 mm, limits included. 
   
   
       4 . The pyrotechnic grain according to  claim 1 , wherein the porosity of said block is 5% or less. 
   
   
       5 . The pyrotechnic grain according to  claim 1  wherein it is in the form of a sleeve of internal equivalent diameter that is advantageously more than 10 mm. 
   
   
       6 . The pyrotechnic grain according to  claim 1 , wherein said at least one oxidizing charge consists of basic copper nitrate. 
   
   
       7 . The pyrotechnic grain according to  claim 1 , wherein said at least one reducing charge consists of guanidine nitrate. 
   
   
       8 . The pyrotechnic grain according to  claim 1 , wherein its composition comprises:
 45% to 55% by weight of guanidine nitrate;   40% to 50% by weight of basic copper nitrate; and   0 to 5% by weight of additives.   
   
   
       9 . A method of producing a pyrotechnic grain according to  claim 1 , the method comprising:
 intimately dry or wet mixing said oxidizing and reducing charges used in the powder state;   dry or wet granulating the powdered mixture obtained;   sizing the granules obtained; and   shaping the retained sized granules by compacting;   
     the characteristics of the starting powders, the retained sized granules and the compacting parameters being selected to produce said pyrotechnic grains having said dimensional and porosity characteristics. 
   
   
       10 . The method according to  claim 9 , wherein the intimate mixture or (and) granulation is (are) carried out by a dry method. 
   
   
       11 . The method according to  claim 9 , wherein the granules are sized by sieving. 
   
   
       12 . The method according to  claim 9 , wherein it comprises:
 using at least one reducing charge with a median diameter of 200 μm or more; and/or, advantageously and   sieving the granules to retain those with a median diameter of more than 200 μm; and/or, advantageously and   shaping by compacting at a pressure in the range 15×10 6  Pa to 35×10 6  Pa for 0.1 s to 30 s.   
   
   
       13 . The method according to  claim 9 , wherein it is carried out with guanidine nitrate as the reducing charge and basic copper nitrate or potassium perchlorate as the oxidizing charge. 
   
   
       14 . A method of generating gas, comprising the combustion of at least one pyrotechnic grain, wherein said at least one pyrotechnic grain is a grain according to  claim 1  and/or a grain produced by a method comprising:
 intimately dry or wet mixing said oxidizing and reducing charges used in the powder state:   dry or wet granulating the powdered mixture obtained:   sizing the granules obtained: and   shaping the retained sized granules by compacting:   
     the characteristics of the starting powders, the retained sized granules and the compacting parameters being selected to produce said pyrotechnic grains having said dimensional and porosity characteristics.