Low energy fuse and method of manufacture

Abstract

A low energy fuse in extruded as a single ply primary tube 1 from a plastic resin blend with particulate energetic material 2 being internally distributed in a manner known per se, said resin blend comprising a major amount of an orientable polymer, for example, linear low density polyethylene to provide structural integrity and a minor amount of a modifier to impart enhanced particle retentive properties to the tube and preferably also containing a polymer or copolymer to impart melt strength and aid in tube extrusion.

We claim:  
     
       1. A cold drawn low energy shock wave conductor comprising an extruded single-wall, dimensionally stable plastic tube having an inner surface coated with a particulate reactive energetic material, the plastic of the tube comprising a substantially homogeneous extrudable  blend of a major amount of a draw orientable  oriented polymer resin lacking adequate reactive material-retaining properties, and a minor amount of a modifier which is a miscible or compatible material which imparts an enhanced reactive material-retaining capability to the inner surface of said extruded plastic tube. 
     
     
       2. A shock wave conductor according to  claim 1  wherein said polymer resin is in the form of a continuous matrix and the modifier is distributed in the matrix polymer such that it has a greater concentration at said inner surface of the tube than in the body of the matrix. 
     
     
       3. A shock wave conductor according to  claim 2  wherein said modifier is present as non-contiguous particles or fibrils within the matrix. 
     
     
       4. A shock wave conductor according to  claim 3  wherein said particles are about  0.5μin  μ in  size. 
     
     
       5. A shock wave conductor according to  claim 2  wherein said modifier is concentrated in segregated zones in the matrix. 
     
     
       6. A shock wave conductor according to  claim 1  wherein the polymer resin is a fibre forming a  polymer. 
     
     
       7. A shock wave conductor according to  claim 1  wherein the polymer resin is selected from the group consisting of (1) addition polymers and condensation polymers having a substantially linear hydrocarbon backbone structure; (2) such polymers wherein the backbone structure is interrupted by hetero atoms; (3) such polymers wherein the backbone structure is substituted by polar functional groups; and ( 4 ) such polymers wherein the backbone structure is interrupted by hetero atoms and substituted by polar functional groups. 
     
     
       8. A shock wave conductor according to  claim 7  wherein the addition polymer is selected from the group consisting of a polyolefin homopolymer and a polyolefin copolymer. 
     
     
       9. A shock wave conductor according to  claim 7  or  8  wherein the addition polymer is selected from the group consisting of a copolymer of ethylene and a copolymer of an alpha-olefin with a substituted olefin monomer. 
     
     
       10. A shock wave conductor according to  claim 7  wherein the condensation polymer is selected from the group consisting of a polyester and a polyamide. 
     
     
       11. A shock wave conductor according to  claim 1  wherein said modifier is selected from the group consisting of a homo-polymer, a copolymer resin, and a material of lower molecular weight than the homopolymer and copolymer resin but of like properties. 
     
     
       12. A shock wave conductor according to  claim 11  wherein the modifier is selected from the group consisting of ionomers, ethylene/acrylic acid (EAA) copolymers, ethylene/methacrylic acid (EMA) copolymers, polyisobutylenes (PIB), polybutadienes (PBD), polyethylene waxes (PE Wax), polyethylene glycols (PEG), poly-propylene glycols (PPG), ethylene vinyl alcohol resins (EVAL), butyl rubber, Rosin, maleinised polypropylene, polyacrylamide or polyacrylamide oxime resins, polyethylene imine, sulphone and phosphonate resins. 
     
     
       13. A shock wave conductor according to  claim 11  wherein the modifier is selected from the group consisting of ethylene/acrylic acid (EAA) copolymers, ethylene/methyacrylic acid (EMA) copolymers and neutralised ionomers thereof. 
     
     
       14. A shock wave conductor according to  claim 11  wherein the modifier is selected from the group consisting of polyisobutylenes (PIB), polybutadienes (PBD), polyethylene waxes (PE Wax), polyethylene glycols (PEG), polypropylene glycols (PPG), ethylene vinyl alcohol resins (EVAL), butyl rubber, Rosin, maleinised polypropylene, polyacrylamide, poly-acrylamide oxime resins, polyethylene imine, sulphone and phosphonate resins. 
     
     
       15. A shock wave conductor according to  claim 11  wherein the modifier is selected from the group consisting of ethylene/acrylic acid (EAA) copolymers, ethylene/methacrylic acids (EMA) copolymers and partially and wholly neutralized monomers thereof. 
     
     
       16. A shock wave conductor according to  claim 1  comprising a minor amount of a homopolymer or copolymer resin or cross-linking agent which is miscible in or compatible with said orientable  polymer resin and which imparts melt strength and aids in tube extrusion. 
     
     
       17. A shock wave conductor according to  claim 16  wherein the melt strength/extrusion improving resin is selected from the group consisting of ethylene/vinyl acetate copolymers and copolymers of ethylene with lower alkyl esters of acrylic or methacrylic acid. 
     
     
       18. A shock wave tube according to  claim 1  having a tensile strength of up to 170 newtons per square millimeter. 
     
     
       19. A shock wave conductor according to  claim 1  wherein the coreload is from about 15 to 60 mg.m −1 . 
     
     
       20. A shock wave conductor according to  claim 1  wherein the coreload is up to about 20 mg.m −1 . 
     
     
       21. A shock wave conductor according to  claim 1  wherein the tube has dimensions of from 2.5 to 3.3 mm O.D. and about 1.3 mm I.D. 
     
     
       22. A shock wave conductor according to  claim 1  wherein the tube is treated externally with agents to improve resistance to water or oil or to water and oil. 
     
     
       23. A shock wave conductor according to  claim 1  wherein the polymer resin is a condensation polymer having a substantially linear hydrocarbon backbone structure interrupted by hetero atoms. 
     
     
       24. A shock wave conductor according to claim  9   7 or  claim 23  wherein the polymer resin has a substantially linear hydrocarbon backbone structure substituted by polar functional groups. 
     
     
       25. A low energy shock wave conductor in the form of a cold drawn extruded single wall, dimensionally stable plastic tube having an inner surface coated with particulate reactive energetic material formed according to the method which comprises 
       (a) extruding a polymeric melt through a wide annular die in the form of a thick walled tube while distributing particulate reactive energetic material in a core load per unit of length on the inner surface of the thick walled tube, the polymeric melt comprising a substantially homogenous blend of a major amount of a draw orientable melt-extrudable polymer resin and a minor amount of a miscible or compatible material as an adhesion promoting agent which is distributed in the extruded melt such that it has a greater concentration at the inner surface of the tube than in the body of the extruded melt and imparts an enhanced reactive energetic material-retaining capability to the inner surface of the extruded tube, and  
       (b) cold drawing the thick walled tube to elongate and form a localized drawing point to increase tube tensile strength, reduce wall thickness, and to reduce core load per unit length of the reactive energetic material.  
     
     
       26. A low energy shock wave conductor according to  claim 25  in the form of a cold drawn extruded single wall, dimensionally stable plastic tube having an inner surface coated with a particulate reactive energetic material wherein the polymer melt further comprises a minor amount of a homopolymer or copolymer resin which is miscible in the polymer melt and which imparts melt strength and aids in tube extrusion. 
     
     
       27. A low energy shock wave conductor comprising a cold drawn, dimensionally stable extruded tube made of extrudable  a plastics material, and containing a core loading of a particulate reactive energetic material, wherein the said tube has an extruded single-wall, and throughout its length an inner surface circumscribing a void through which a shock wave may be transmitted, the said surface retaining said particulate reactive energetic material as a layer thereon, and the said plastics material comprises a substantially homogeneous blend of a major amount of a draw orientable  oriented polymer resin lacking adequate reactive material-retaining properties, and a minor amount of a modifier which is a miscible or compatible material which imparts an enhanced reactive material-retaining capability to said polymer resin. 
     
     
       28. A low energy shock wave conductor comprising an extruded single-wall, dimensionally stable plastic tube having an inner surface coated with a particulate reactive energetic material, the plastic of the tube comprising a substantially homogeneous extrudable  blend of a major amount of a draw orientable  oriented polymer resin lacking adequate reactive material-retaining properties, and a minor amount of a modifier which is a miscible or compatible material which imparts an enhanced reactive material-retaining capability to the inner surface of said extruded plastic tube wherein the polymer resin is a continuous matrix and the modifier is present as fibrils a few microns in length with aspect ratios of from about 6 to about 10 aligned with the tube axis and distributed in the matrix polymer such that it has a greater concentration at the inner surface of the tube than in the body of the matrix. 
     
     
       29. A cold drawn shock wave conductor according to  claim 28 . 
     
     
       30. A low energy shock wave conductor comprising a cold drawn plastic tube having a longitudinal axis and an inner surface which circumscribes a void, said inner surface being coated with a reactive material which upon ignition produces a shock wave which is transmitted along the tube within the void, said tube comprising: 
       ( a )  a first polymer which:    
         (   i ) has a chemical composition which:  
       ( a )  causes the first polymer to exhibit an increase in tensile strength per unit area when draw oriented, and    
       ( b )  lacks adequate reactive material - retaining properties; and    
       ( ii )  has been draw oriented by being cold drawn in the direction of said longitudinal axis; and    
       ( b )  a second polymer which:    
       ( i )  has a chemical composition which causes the second polymer to exhibit enhanced reactive material - retaining capability compared to the first polymer; and    
       ( ii )  is located at at least said inner surface.   
     
     
       31. The low energy shock wave conductor of  claim 30  wherein the first polymer has been draw oriented at a draw ratio of at least  4 : 1 , weight for weight for equal lengths of undrawn and drawn polymer. 
     
     
       32. The low energy shock wave conductor of  claim 30  wherein the first polymer comprises a linear polyethylene. 
     
     
       33. The low energy shock wave conductor of  claim 30  wherein the second polymer comprises an ethylene acrylic acid copolymer. 
     
     
       34. The low energy shock wave conductor of  claim 30  wherein the second polymer comprises an ethylene/methacrylic acid copolymer. 
     
     
       35. The low energy shock wave conductor of  claim 34  wherein the ethylene/methacrylic acid copolymer is wholly or partially neutralized. 
     
     
       36. The low energy shock wave conductor of  claim 30  wherein the second polymer comprises an ionomer. 
     
     
       37. The low energy shock wave conductor of  claim 30  wherein the inner surface is coated with the reactive material at a core load rate of  10 - 30  milligrams per meter.