Abstract:
This disclosure considers the use of specifically-sized Nitrocellulose particles of 75 ml fineness, free of other chemicals, as a flame enhancer in a Diazodinitrophenol primer mixture that is free of heavy metal constituents.

Description:
BACKGROUND ART  
         [0001]    Since the 1930&#39;s, the primers for small arms ammunition have, generally, contained Lead Styphnate as a primary explosive, Tetracene to sensitize the Lead Styphnate, Barium Nitrate for an oxidizer, Antimony Sulfide for a frictionator and fuel, a secondary explosive like PETN for brisance, and various gums as a binder. These primers were very successful for many years and are still in use today. They are very reliable, moisture resistant, and stable in storage and use. They were a great improvement over the corrosive Potassium Chlorate and Mercury Fulminate primer mix formulations in use prior to that time.  
           [0002]    Now, however, there has been a growing demand for a primer that is non-toxic to the shooter and the environment, when fired in indoor ranges. Heavy metal byproducts of primer combustion, such as Lead, Barium, and Antinomy can be harmful when inhaled or ingested by the shooter. Many indoor shooting ranges have been closed in recent years because of these hazards. Consequently, customers are demanding primers that are free of Lead, Barium, and Antimony compounds.  
           [0003]    Many patents have been issued over the last few years for priming compositions that are free of these heavy metals. They usually contain Potassium Dinitrobenzofuroxan (KDNBF) or Diazodinitrophenol (DDNP) as a primary explosive, Tetracene as a sensitizer, powdered Aluminum for a fuel, Calcium Silicide, powdered glass, or Boron as a frictionator, and various gums for a binder. The oxidizers used are KNO 3 , SnO 2 , CaCO 3 , MnO 2 , Sr(NO 3 ) 2 , etc. Processed propellant material, such as WC 669, and ground double base propellants have been used as a flame enhancers in these priming mixes. These nitrocellulose-based products work as intended, but are not ideal because they are usually granular materials of random size or propellant by-products with graphite, flash suppressants, and other chemicals, which are not desirable in primers.  
           [0004]    Another drawback of the Nitrocellulose and processed propellant flame enhancers used previously is that they can result in Nitrocellulose agglomerations or propellant particles of a size that can cause misfires in the ammunition. Further, the Nitrocellulose agglomerations are not easily dispersed and do not blend uniformly throughout the primer mixture. It is known that such masses of these materials have been deposited between the anvil tip and primer cup in Centerfire percussion primers that created a “dead spot” which caused the primer to fail to fire on impact of the firing pin. Similar “dead spots” have also been found in Rimfire ammunition when such particles or agglomerations were found to be deposited in the annulus of the cartridge rim. 
       
    
    
     DESCRIPTION OF THE INVENTION  
       [0005]    The research that led to the present invention revealed that by using a Nitrocellulose of very small fibers, with dimensions of 75 ml fineness or less, allow the production of an improved non-toxic priming composition that is more uniform and at a more cost-effective price as compared to the state of the art.  
         [0006]    The improvement corresponds to the dimensioning of the nitrocellulose fibers used in the priming composition. The limitation of fiber dimension to 75 ml or less ensures easy dispersion of the Nitrocellulose, fostering its complete mixing with the remaining chemicals used in the priming mixture and thus practically eliminating the risk of forming clusters and warranting uniform, homogenous mixtures. It is worth remembering that the mixture uniformity is a commanding feature for the primer detonator sensitivity with major influence over the ballistic performance.  
         [0007]    One added advantage of the present invention is that the mixture homogeneity makes its dosing easy whatever the scale used, thus ensuring the production of uniform pellets which are homogenous as far as their composition is concerned, therefore featuring also homogenous and uniform weights.  
         [0008]    The elimination of the risk of clustering of the flame enhancer Nitrocellulose during the manufacture of the primer mixture prevents the appearance of the so-called “dead spots” both in Centerfire and Rimfire primer detonators that can cause misfires in small arms cartridges. Furthermore it eliminates the risk of other similar dead spots due to lack of homogeneity that could occur in the mixture when processed propellants are used as flame enhancers.  
         [0009]    Chemically, the specific sized small particle Nitrocellulose is a pure material, which does not have any nitroglycerin, Diphenylamine, graphite, flash suppressants, or residual alcohol-acetone, which would get into the primer. These adulterating chemicals can destabilize the non-toxic priming and generate adverse ignition temperatures, especially under extreme ambient temperature conditions.  
         [0010]    Another advantage of the present invention is the reduction of the effective production cost. Said reduction derives from the fact that the processed propellants used in the primer mixture composition are obtained from nitrocellulose, which before reaching the processed propellant condition undergoes the following processing steps: dilution in alchool-ketone, maceration, extrusion, cut, drying, annealing, mixing, etc. In the present invention, the nitrocellulose is added in natura to the primer mixture composition, therefore foregoing all the processing steps previously required to reach the condition of processed propellant. The addressed economy gain derives from the elimination of the use of the raw materials required for the steps of dilution in alchool-ketone, maceration, mixing, etc., and also the dropping of the previously required skilled workforce for performing such steps.  
         [0011]    Among the various formulations of non-toxic primer mixtures composition using specifically-sized Nitrocellulose tested, it was found that the formula presented on Table 1 below featured better results with the lowest effective cost.  
                                               TABLE 1                           PROCESSING EXEMPLE                Preferred   Acceptable           Percentage   Extended Range                            Diazodinitrophenol   35   30-45           Tetracene   5   4-6           Specific-sized Nitrocellulose   25   12-30           Potassium Nitrate   17   10-19           Powdered aluminum   4   4-7           Powdered glass   13    8-15           Gum Tragacanth   1   0.1-1                        
 
         [0012]    Diazodinitrophenol manufactured by the standard procedure of reacting Hydrochloric acid and Sodium Nitrite with Sodium Picramate is washed and de-watered. A moisture check is made and it is put in storage until used.  
         [0013]    Tetracene and specifically-sized Nitrocellulose are also tested for moisture and stored until needed.  
         [0014]    Potassium Nitrate, Powdered Aluminum, ground glass, and gum Tragacanth are weighed out in the correct proportions and are blended. This dry pre-mix is then stored until needed in the final composition mixing.  
         [0015]    The wet Diazodinitrophenol, Nitrocellulose, and Tetracene are weighed in the correct proportions, according to their moisture content, in preparation for the mixing process. The total amount of moisture in these components is calculated, and if additional water is required to make a final primer mix of the correct water content, it is measured out before the mixing process begins.  
         [0016]    In the final mixing process, the three wet components, Diazodinitrophenol, Specifically-sized Nitrocellulose, Tetracene and additional water are placed in the mixing bowl. These are then blended thoroughly by remote control until thoroughly homogenized. The dry mix is then added to the mixing bowl and blended remotely until the final primer mix is completely homogenous. The blended primer mix is then removed from the mixer bowl, transferred to conductive containers, and stored until used. Charging of the mix and assembly of primers is done in the usual manner, and is well known to those experienced in the art.  
       PRIMER TEST DATA  
       [0017]    CBC No. 1½ small pistol size primers were made using a primer mix formulation in the preferred percentage proportions and tested in 9 mm Luger cases and ammunition. These were tested in comparison with the CBC No. 1½ small pistol primer and compared to SAAMI specifications. These were found to comparable in all respects. The results of these tests are presented in Tables 2 and 3 below.  
                           TABLE 2                               Primer                   detonators       Primer detonator   Non-toxic mixture   with Lead       sensitivity test   primer detonator   Styphnate   SAAMI       results   Samples   based mixture   Directive                   H − Mean Height   11.83 cm   13.64 cm   11.0 cm       of fire       s − standar    2.05 cm    1.36 cm    4.25 cm       deviation       H − 2s − non-    7.73 cm   10.92 cm    2.5 cm       operating height       H − 4s −   20.03 cm   19.08 cm   28.0 cm       Operating height                  
 
         [0018]    [0018]                                                     TABLE 3                           Cartridges   Cartridges               with   with           detonators   detonators           loaded with   loaded with           non-toxic   Lead Styphnate           primer   based primer       Ballistic test   mixture N.°   mixture N.°   SAAMI       results   1 ½ NT   1 ½   Directive                                Chamber pressure (+   2099   kgf/cm 2     2099   kgf/cm 2     2510 kgf/mc 2         21° C.)       s (Standard   73   kgf/cm 2     75   kgf/cm 2     Not available       deviation)       Chamber pressure (+   2128   kgf/cm 2     212   kgf/mc 2     Not available       50° C.)       s (Standard   80   kgf/cm 2     83   kgf/cm 2     Not available       deviation)       Chamber pressure(−   2015   kgf/cm 2     1969   kgf/cm 2     Not available       50° C.)       s (Standard   130   kgf/cm 2     83   kgf/cm 2     Not available       deviation)       Velocity (+   330   m/s   327   m/s   332 ± 27 m/s       21° C.)       s (Standard   5   m/s   5   m/s   Not available       deviation)       Velocity (+   334   m/s   332   m/s   Not available       50° C.)       s (Standard   5   m/s   7   m/s   Not available       deviation)       Velocity (−   319   m/s   312   m/s   Not available       50° C.)       S (Standard   9   m/s   7   m/s   Not available       deviation)                    
         [0019]    Those skilled in the art will realize that the foregoing description of one of the preferred embodiments does not limit the application of the present invention to mixture compositions with the characteristics described, and that it can be applied to other similar compositions for priming mixtures without departing from the scope and inventive spirit covered on the following set of claims.