Patent Publication Number: US-H925-H

Title: Encapsulated signal illumination flare composition

Description:
DEDICATORY CLAUSE 
     The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalties thereon. 
    
    
     BACKGROUND OF THE INVENTION 
     The present method for signal flare manufacture involves using a high-shear muller type mixer because the binder is viscous and highly adhesive. The use of a cured Laminac 4116 type binder even with mixing performed with a muller type mixer makes mixing difficult, and particularly, homogeneity of the ingredients is difficult to achieve. The mixing problems are attributed to the highly viscous and adhesive properties of the Laminac 4116 type binder. Because of the employment of this method of mixing, loss of materials due to hang-ups, time consumed in cleaning and equipment, and batch mixing due to the short potlife of the binder are contributing factors to substantial capital expenditures. 
     SUMMARY OF THE INVENTION 
     The object of this novel method for the manufacture of signal illuminant flare compositions is to provide an encapsulated binder whereby the flare ingredients of magnesium powder, sodium nitrate, and an capsulated adhesive are blended to achieve homogeneity of ingredients prior to feeding into a flare press. When the specified ingredients are pressed in the flare-producing press, the binder capsules are crushed and the other ingredients, sodium nitrate and magnesium are bonded into a solid flare mass. 
     The instant invention involves the use of PEF-12 capsular adhesive without the titanium dioxide filer. This material is manufactured by the National Cash Register Company. The adhesive consists of two separate capsules which are blended together. One capsule contains the condensation products of epichlorohydrin and Bisphenol A or diglycidyl ether of Bisphenol A (EPON 828) 79% with 12% benzoyl peroxide. The second capsule contains Aropol 72-40-MC polyester resin with 5% N,N&#39;-dimethyl-o-toluidine as the cure accelerator. The cell walls of both capsules are composed of Arabic gum and gelatin. They are produced using the coacervation technique. The capsules are blended in the order of one part epoxy capsule to two parts polyester capsule. The capsule sizes range from 300-1000 micrometers. When blended together, the capsules form a blend which performs as a free-flow powder containing 91% liquid materials with cell walls composed of about 9% Arabic gum and gelatin. 
     The encapsulated illuminant compositions are manufactured by dry blending magnesium powder, sodium nitrate and the encapsulating binder. A quantity of flare increment is supplied by a flare increment feeder to a compacting flare press. The force of the compacting press causes rupture of the capsules, and the hydrualic force causes the polymers to mix, and surround the powders resulting in a very homogeneous mass. 
     The illuminant compositions are compacted into paper containers (31-mm in diameter and 64-mm long) similarly to the standard M127A1 Hand-Held Signal Illuminants. The candles were compacted in two increments, 14,000 psi and cured for 16 hours at a minimum temperature of 170° F. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 depicts flare burning rate, inches per second (ips), as influenced by magnesium and binder content. 
     FIG. 2 depicts candlepower output as influenced by magnesium and binder content. 
     FIG. 3 depicts a flow diagram for manufacture of M127A1 illuminant flares in accordance with prior art manufacturing sequences. 
     FIG. 4 depicts a flow diagram for the manufacture of encapsulated signal illuminant flares. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The signal illuminant flare composition prepared in accordance with this invention employs a capsular adhesive composition as the binder in two separate capsules which are blended in equal amounts together to form blend which performs as a free-flow powder containing 91% liquid material. The capsules are ruptured when subjected to the force of the compacting press used to consolidate the flare composition, and the resulting hydraulic forces causes the curable polymer to mix and surround the powders resulting in a very homogeneous mass. 
     
                       TABLE 1                                                     
______________________________________                                    
CAPSULAR ADHESIVE COMPOSITION*                                            
Capsule No                                                                
         Content           Weight Percent                                 
______________________________________                                    
1        Diglycidyl ether  79.0                                           
         of Bisphenol A**                                                 
         Benzoyl peroxide  12.0                                           
         Arabic gum and gelatin (1:1)                                     
                           9.0                                            
                           100.0                                          
2        Polyester resin***                                               
                           86.0                                           
          .sub.-- N, .sub.-- N&#39;-dimethyl- -o-toluidine                    
                           5.0                                            
         Arabic gum and gelatin (1:1)                                     
                           9.0                                            
                           100.0                                          
______________________________________                                    
 *PEF-12- Manufactured hy National Cash Register Company                  
 **EPON 828                                                               
 ***Aropol 7240-MC                                                        
 
    
     The percentage of binder, and the magnesium content, which are incorporated in the illuminant compositions influence the burning rate and the candlepower output thereof. These data are presented in Table 2 below and illustrated graphically in FIGS. 1 and 2. 
     
                       TABLE 2                                                     
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EFFECT OF BINDER AND MAGNESIUM                                            
CONTENTS ON FLARE                                                         
BURNING RATE AND CANDLEPOWER                                              
       Binder  Mg     Density                                             
                             Burning                                      
Mix No.                                                                   
       (%)     (%)    (gm/cc)                                             
                             Rate (IPS)*                                  
                                      Candlepower                         
______________________________________                                    
1      6       45     1.808  0.0640   137,400                             
2      6       50     1.762  0.0799   173,300                             
3      6       55     1.707  0.0996   202,400                             
4      6       57     1.686  0.1119   201,400                             
5      8       45     1.847  0.0573   127,400                             
6      8       50     1.794  0.0748   151,100                             
7      8       55     1.754  0.0966   161,400                             
8      8       60     1.696  0.1110   161,700                             
9      10      45     1.858  0.0580   101,800                             
10     10      50     1.815  0.0730   119,500                             
11     10      55     1.764  0.0870   130,900                             
12     10      60     1.728  0.0996   126,600                             
13     12      50     1.863  0.0548   115,100                             
14     12      55     1.787  0.0752   103,800                             
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 Notes: *IPS = inches per second                                          
 1. Illuminant weight = 85 grams                                          
 2. Magnesium powder -30/50 micrometers weightmeans-diameter by sieve     
 analysis                                                                 
 3. Sodium nitrate -20micrometers weightmean-diameter by Fisher Subsieve  
 sizer; 55micrometers weightmean-diameter by sieve analysis               
 
    
     A crush resistant strength test was used to compare the mechanical properties of this illuminant. This involved the preparation of 20-gram samples which are consolidated at 14,000 psi in a 1.0 inch diameter die. The reference for evaluation was the standard illuminant composition which had been cured for 10 days at ambient temperature. Ballistic compositions of illuminant ammunition which had been cured under these conditions have performed satisfactorily, and, therefore, the crush strength measured on these standards has been defined as adequate. The encapsulated binder pellets demonstrated better crush strength over the temperature range of -65° F. to +160° F. than the standard pellets based on Laminac 4116. 
     Friction and drop sensitivity tests were conducted to determine the safety characteristics of these Illuminants. The drop sensitivity of the illuminant containing the encapsulated ingredients were determined to be less sensitive than the standard M127A1 illuminant. The M127A1 illuminant had a drop sensitivity of 19 inches with a 4 pound ball. The illuminant containing the encapsulated binder had a drop sensitivity of 30 inches with a 4 pound ball. Thus, the safety aspects which would result from the adoption of the illuminant containing the encapsulated binder would be lower impact sensitivity, reduced safety hazards in manufacture, significant capital cost savings and manufacturing costs. 
     A flow diagram for the manufacture of M127A1 signal illuminant flares is depicted in FIG. 3, and the flow diagram for the manufacture of encapsulated signal illuminant flares is depicted in FIG. 4. 
     The mechanism of capsular rupturing of the two component capsular adhesive or the curable polymer materials defined in Table I provides a unique means for mixing and consolidating materials for signal illuminant flares. In addition to the fact that this new process offers ease of manufacture, other benefits derived include the following: 
     a. Savings in capital equipment, 
     b. Improved safety, 
     c. Reduced exposure of personnel to hazardous operations, 
     d. Continuous processing instead of bath processing, and 
     e. Lower operating/maintenance costs.