CA1146757A - Incendiary composition and process of production - Google Patents
Incendiary composition and process of productionInfo
- Publication number
- CA1146757A CA1146757A CA000330240A CA330240A CA1146757A CA 1146757 A CA1146757 A CA 1146757A CA 000330240 A CA000330240 A CA 000330240A CA 330240 A CA330240 A CA 330240A CA 1146757 A CA1146757 A CA 1146757A
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- Prior art keywords
- composition
- incendiary
- cord
- igniter
- water
- Prior art date
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Abstract
ABSTRACT OF THE DISCLOSURE
An incendiary composition and products such as igniter cords employing the incendiary composition is dis-closed. In particular, the composition which comprises an oxidizer, a reducer and a binder, is capable of ignition under water. Previous under-water incendiary compositions employed very hazardous materials, such as nitroglycerine and nitrocellulose, in their manufacture. The present composition employing, for example, an oxidizing salt, a reducing metal and a waterproof binder, substantially elimi-nates these hazards.
An incendiary composition and products such as igniter cords employing the incendiary composition is dis-closed. In particular, the composition which comprises an oxidizer, a reducer and a binder, is capable of ignition under water. Previous under-water incendiary compositions employed very hazardous materials, such as nitroglycerine and nitrocellulose, in their manufacture. The present composition employing, for example, an oxidizing salt, a reducing metal and a waterproof binder, substantially elimi-nates these hazards.
Description
67~7 THIS INVENTION relates to an incendiary composition.
In particular the invention relates to an incendiary composition; a method of making the composition; to products including the composition such as igniter cord, an igniter cord connector and an electric fuse head.
According to the invention an incendiary composition comprises an oxidizing agent, a reducing agent, and a water miscible binder, the binder forming the continuous phase of the composition in which the oxidizing agent and reducing agent are dispersed.
`' ' Naturally, if desired, the composition according to the invention can include more than one oxidizing agent, more than one reducing agent and the water miscible binder may also comprise a mixture of materials.
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~4G757 The composition may be malleable, so that products made therefrom such as igniter cord can be flexible, i.e. capable of belng bent or shaped without cracking or breaking.
The composition may be waterproof, in that it is capable of burning af-ter having been wet, for example by being sprayed with water or immersed in water.
Preferably, the composition is capable of burning under water.
The composition may be one in which, after dispersion of the oxidizing agent and reducing agent in the binder, the binder has been cross-linked. This cross-linking may be achieved by any suitable method, such as the use of a suitable catalyst or a two component system, or by subjecting the composition to suitable irradiation, but cross-linking by heat is preferred~
'' The binder may be selected from the group consisting in acrylics, latices, and polyvinyl acetates. The applicant also believes that there may be ~` starches plasticized with polyols, or polybutadienes which can act as suitable blnders ac~ording to the invention.
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f~",L~ 757 The oxidizing agent may be selected from the group consisting in potassium perchlorate, lead dioxide, red lead, potassium nitrate, ammonium perehlorate, sodium perchlorate, potassium permanganate and sodium dichroma-te. The oxidizing agent may be ` sparingly soluble in water, such as potassium perchlorate or substantially insoluble in water, such as red lead, and is preferably, say, no more than twice as soluble as potassium perchlorate at ambient temperatures.
The reducing agen-t may be selected from the group consisting in carbon, silicon, ferrosilicon, aluminium, copper, zinc and tungsten, and is preferably no more than sparingly soluble in water at ambient temperatures.
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Further according to the invention a method of making the composition described above comprises mixing : the components together in the presence of water . followed by drying of the composition.
:, The method may include modifying the viscosity of the mixture by mixing the components together with a viscosity modifier, such as a thickener or an agent which reduces the viscosity of the mixture, .. . ..
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depending on what is convenient for the process of manufacture, and on the proportions of the various components, including water, in the mixture.
Mixing may be by means of a mechanical mixer. As the presence of water renders the composition safe, the mixing can be performed by almost any type of mixer, such as edge-runner, concrete, planetary and ribbon ~ mixers, and the mixing can be effected for long periods ; of time. secause of this safety, the method may include pumping the mixture, for example via a 15 mm ring main and a Mono pump, from the location where it is mixed to another location prior to drying. In this way the paste or slurry produced can be distributed after mixing to application points by a mechanical distribution system rather than by a manual distribution system.
As the composition is water based, it does not require heating to render it fluid for mixing or handling.
The method may thus involve maintaining the components at ambient temperature prior to drying.
; After the mixing, the binder may be cross-linked.
; As mentioned above, the cross-linking may be effected by the use of a catalyst or a two component system, or the composition may be subjected to suitable irradiation ~;:
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' ~6~7S7 or the cross-linking may be affected by heating. This cross-linking acts to enhance the waterproof qualities of the composition, as the contlnuous phase constituted by the cross-linked binder at least partially encap-sulates or encloses the particles of reducing agent and oxidizing agent dispersed in the binder.
The drying is thus conveniently effected by heating, so that the heating of the drying acts also to cross-link the binder. In ordex to speed up the drying and/or reduce the temperature of the drying, the composition may be subjected to a vacuum during the- drying.
The method may include mixing the components together with a surfactant, such as a wetting agent, to enhance the wettin~ of insoluble components in the mixture, to facilitate preparation of the mixture.
The composition of the invention can be put to a number of uses, such as the manufacture of igniter cord, igniter cord connectors, delay elements, flares, fuse heads, or the like.
The invention thus provides an igniter cord which cornprises a core having a composition according to the invention as described above, applied thereto.
The core may be a metal wire, or the core may be made up of a plurality of yarns or strands, such as textile yarns and/or metal strands.
The core may be enclosed by a flexible extruded incendiary sleeve. The incendiary sleeve may be of a flexible incendiary composition as described above. At least part of the core, under the sleeve may be treated with an incendiary material, and the incendiary material may be an incendiary composition, preferably flexible, as described above. Thus a composition according to the invention as described above may be used for the sleeve and/or for treating the core under the sleeve, the treating of the core with the composition under the sleeve being of particular application when the core is made up of a plurality of yarns or strands.
The igniter cord may have an extruded plastics outer coating, in which case the cross-sectional profile of the cord may be of angular outline. Having the cross-sectional profile of the cord of angular outline, such as square outline, is believed to enhance the formation of air spaces between the coa~ing and the ~ .
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~675~7 cord, thereby permitting forward venting of hot gases during burning and thus increasing the burning speed of the igni-ter cord.
It will be appreciated that an important aspect of the process of making -the incendiary composition according to the invention is that the mixing can take place in the presence of water. The drying of the composition can be natural in -that the composition is merely left until it dries by itself, or it can be forced in that it is subjected to heating and/or a vacuum, etc, to cause rapid drying. Thus the mixture, prior to drying, is incapable of being ignited with a match, but will be capable of such ignition after drying. The choice of suitable components and the proportions used in the mixture enable a slurry or paste to be formed which can be pumped, or formed into any suitable shape rior to drying, and can provide an incendiary composition which after drying can be flexible and can be capable of burning under water. Provided sufficient water is always present at the stage when the oxidizing agents are brought together with the reducing agents or fuels, for example by always adding water to the mixer first, the order of addition of the components during mixing canno-t affect the non-incendivity of the paste. Furthermore, ~ 6'7~7 g ~
mixing times and rates of mixing or rates of addition can be adjusted to any desired value in order to optimize production rates.
In the making of igniter cords, any suitable means can be used to apply the paste or slurry at the application point to the metal wire or the yarns or strands which make up the core of the igniter cord.
Suitable means of application can be, for example, kettle application, extrusion by conventional worm extruders, Mono pump feeding or auger feeding, the iqniter cord which results preferably being flexible and waterproof r and being capable o burning under water as described above.
Although simple extrusion of the composition according to the invention onto cores made of metallic wire such as a single copper wire, or onto composite cores made up of yarn threads or metallic strands, may be suitable to provide igniter cord o~ relatively slow burning rates such as about 30 - 45 seconds a metre, such extrusion can be unsuitable for providing igniter cords having a burning rate faster than about 16 seconds a metre. The reason for this i~s that the burning rate is increased by reducing the quantity~of water miscible binder present in the composition, and the _ -- .. ~ . .. .. . .
excessive reduction of this binder can lead to an unacceptable loss of flexibility in the igniter cord product.
To make a fast burning igniter cord, typically having a burning rate of 8 - 16 seconds a metre or as fast as one second a me-tre, a composite core made up of spun yarn or threads of metallic and/or non-metallic nature can be used. This core is first drawn through a kettle or bath containing a slurry-like incendiary composition to form what is called a semi-cord. This semi-cord is then coated by means oE extrusion with a plastic incendiary sleeve. This process has the advantage that longitudinally extending air spaces created between the semi-cord and its extruded flexible incendiary sleeve permit forward venting of hot gases produced during combustion which increases the burning rate of the cord over that of cords which do not have the air spaces and which rely on simple forward heat conduction to determine the burning rate. The slurry-like incendiary composition in the kettle or bath and the incendiary sleeve are preferably both of compositions including a water miscible binder according to the invention as described above. However, as mentione'd above either the slurry-like incendiary composition or the incendiary sleeve may be of conventional incendiary compositions which do not include a water miscible binder.
,7 The invention also provides an igniter cord connector comprising a metal tube having a plug of an incendiary composition according to the invention as described above, the plug being recessed from an open end of the tube.
Both ends of the tube may be open, the plu~ extending to the end of the tube opposite the end from which it is recessed. Instead, the connector may be of a construction in which the end of the tube opposite the open end is closed, the side of the tube at the closed end having a transverse slot therein for receiving an igniter cord, the slot extending through the plug. In each case the open end of the tube from which the plug is recessed is intended for crimping or other suitable connection to a safety fuse, and the ign1ter cord can thus be provided with such safety fuse inserted into and connected to the end of the tube from which the plug is recessed, and "open end of the tube" is to be construed accordingly as covering the situation where it is in fact closed , bu-t closed with a safety fuse inserted into it.
The exposed part of the plug remo~te fro~ the recessed end ie the opposite end of the tube when both ends of the tube are open or the part of the plug ., exposed by the slot when -the tube has a slot, is intended for being initiated by an igniter cord, and this exposed part may be sealed against water penetration, conveniently by a suitable sealant, and depending on the nature of the water miscible binder used for the incendiary composition according to the invention, this binder may be suitable for use as the sealant.
The invention also provides an electric fuse head comprising a fuse head skeleton enclosed by a composition according to Claim 1.
In the drawings;
Figure 1 shows in graphical form the variation of burning speed in proportion to the level of binder in cords;
Figure 2 shows a connector composition being placed into a mould;
Figure 3 shows a connector and ignitercord combination;
and Figure 4 shows mould filling with a syringe injector system.
The invention will now be described with reference to the following illustrative and non-limiting Examples.
A paste composition in accordance with the invention was made by thoroughly mixing together, on a weight basis, 14.5%
water, 8.6% of a water miscible acrylic binder available as A272 from Revertex S.A. (Proprietary) Limited, Durban, 16.1% potassium perchlorate, 38.7% red lead, 21.9% ferrosilicon and 0.2% of a 10% weight a~ueous carboxymethyl cellulose solution. The potassium perchlorate and red lead were the oxidizing agents --, _ ,_ -~ .
, while the ferrosilicon and carboxymethyl cellulose respectively formed the reducing agent and a thickener.
This composition beEore drying was Eound to be incapable of ignition with a match, and it was arranged in the mixing that the oxidizing and reducing agents were brought into contact in the presence of the water, so that no stage was an incendiary material produced prior to drying.
The composition according to Example 1, prior to drying, was extruded as a water-based paste onto a copper wire using an auger feeder, to provide an incendiary sleeve around the copper wire, and the paste was dried at a sufficient temperature to cause cross-linking of the acrylic binder. The product was then finished by extruding a plastics (polyethylene) outer coating around the sleeve to provide a flexible incendiary igniter cord capable of burning under water which burnt at a rate of 24,5 seconds a metre in air. The use of a water-based paste permitted thorough mixing leading to enhanced reproducibility of the igniter cord burning speed. Ten one metre lengths of the igniter cord burnt at an average value of 24,5 seconds a me-tre with a standard deviation of 0,97 seconds a metre, whereas igniter cord of comparable speed made by conventional methods burnt at 23,9 seconds a metre with a standard deviation of 1,99 seconds a metre.
It was found that the burning speed of the igniter cord produced according to Examples 1 and 2 can be altered easily by a number of methods, for example by changing the proportion of binder in the composition produced according to Example 1, or by changing the shape of the extrusion die. When the incendiary sleeve was extruded with a square die, the cord was found to burn more quickly than with a round die, and without being bound by theory it is believed by the applicant that the use of a square die having an angular cross-sectional profile leads to the formation of air spaces between the ethylene outer coat and the sleeve, leading to forward venting of hot gases during burning and enhance the speed.
The process of Example 1 was repeated with variations in the proportion of binder, and varia~ion of burning speed in air with variation in the proportion of binder for round cords is shown in Figure 1.
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It was found -that paste rheology could be altered to suite the method oE applica-tion. For example, a runny paste of approximate viscosity of 1000 poise suitable ~or kettle application could be produced, whereas a thick paste having a viscosity of about 5000 poise could be produced for auger feeding. The viscosity was altered by changing the amount of water in the composition and/or by the incorporation of suitable viscosity modifiers. Thus in Example 1 14j5% water was employed to ensure non-incendivity of the wet paste, but as a thick paste was required for auger feeding 0,2% of the 10% carboxymethyl cellulose solution was added as a thickener.
An incendiary composition in the form of a runny paste in accordance with the invention was made having a composition of 150 parts by weight of water, 40 parts by weight of a polyvinyl acetate water miscible binder available as MOWILITH*DC from Hoechst South Africa (Proprietary) Limited, Industria, 75 parts by weight of potassium perchlorate, 175 parts by weight of red lead and 100 parts by weight ferrosilicon. This incendiary paste was runny and was suitable for coating a core comprising cotton cord, by drawing the core through an application kettle.
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The proportion of water was then reduced to 70 parts by weight (the proportions of the other components being unaltered) and 2 parts by weight of a viscosity modifier (reducer) comprising ammonium polybutylacrylate available as POLYSALZ*S from BASF South Africa (Proprietary) Limited, Johannesburg, was incorporated, to obtain a runny paste of substantially the same viscosity capable of application to a cotton cord by drawing through an application kettle in the same fashion.
In each case a round igniter cord was produced, which was not provided with an extruded sleeve and was not coated with a plastics coating, and which was found to burn at a speed of 37 seconds a metre.
Alternative formulations to the composition of Example 1 were made and tested, in which the potassium perchlorate and particularly the red lead were replaced with other oxidizing agents such as lead dioxide, -~ potassium nitrate, ammonium perchlorate, sodium perchlorate, potassium permanganate and sodium dichromate. These formulations were all found to provide suitable general purpose incendiary compositions with the advantage that, before drying, the enhanced safety provided by the invention was present. However, as the oxidizing * TM
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" 1~4~57 agents tested were all more soluble in water than red lead, in the production of igniter cord they tended to crystallize at the surface of the cord during drying, having been brought to the surface by the evaporating water. They thus suffered loss of flexibility and waterprooEness, and were found to be somewhat inhomoge-neous, although burning rates were unaffected. Red lead on the other hand, is virtually insoluble in water, and potassium perchlorate is only sparingly soluble in water.
In these tests a surfactant was used as a wetting agent, to facilitate the paste preparation, and to enhance the wetting of the insoluble components of the paste. In particular, the surfactant available as TAMOL NNO from BASF South Africa (Proprietary) Limited, ~ohannesburg, compr~sing the sodium salts of the condensation product of naphthalene sulfonic acid with formaldehyde, was used. The TAMOL was used in a 1%
aqueous solution.
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- An incendiary composition in the form of a slurry in accordance with the invention was made up from 1340 parts by weight of a 1% by weight TAMOL solution, 150 *TM
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~6757 parts by weight of A272 acrylic binder, 250 parts by weight potassium perchlorate, 600 parts by weight red lead and 340 parts by weight ferrosilicon together with 3,25 parts by weight of a 10% by weight carboxymethyl cellulose solution. This slurry was applied by drawing two parallel paper yarns -through a kettle containing the slurry, followed by drying, followed by countering (spinning) with one jute yarn and three rayon yarns, to produce a semi-cord.
This semi-cord was then coated by means of extrusion with a conventional plastic incendiary composition (not according to the invention) comprising suitable proportions of red lead and potassium perchlorate as oxidizing agents, a suitable proportion of ferrosilicon as reducing agent, and a suitable proportion of plasticized nitrocellulose as a binder, followed by a polyethylene outer coating or sheath. Burning of twenty five one metre lengths produced a mean burning rate of 7,7 seconds a metre with a standard deviation of 0,56 seconds a metre.
Use of the same slurry, but with three parallel paper yarns having the slurry applied thereto and countered (spun) with three rayon ya~ns followed by coating with the nitrocellulose-containing plastic . ~
incendiary composition and the polythene sheath, yielded an igniter cord which burnt at a rate of 2,3 seconds a metre with a standard deviation of 0,~3 seconds a metre.
The cords produced above and haying an extruded sleeve of the nitrocellulose-containing plastic incendiary composition did not burn under water. However, when the extruded sleeve was replaced by a sleeve according to the formulation of Example 1, an igniter cord was obtained capable of burning under water. Likewise, when the slurry applied in the kettle to the parallel paper yarns was replaced by a conventional slurry-like incendiary composition com~rising one or more suitable oxidizing agents, one or more suitable reducing agents and nitrocellulose dissolved or suspended in acetone or a similar volatile solvent to form the semi-cord, followed by extrusion of a sleeve of a composition according to the invention of the formulation of Example 1, and a polythene sheath, a flexible igniter cord was obtained, which was once again waterproof, and capable of burning at 6 seconds a metre in air, and 30 seconds a metre under water.
fast burning flexible igniter cord could thus be obtained by extruding a sleeve of flexible incendiary material according to the invention on semi-cord, the i75~7 semi-cord being produced either from a sluxry in accordance with the invention or a conventional slurry. A conventional plastic incendiary composition sleeve can also be extruded over a semi-cord made with slurry in accordance with the invention, although this does not have the advantage oE waterproofness. In each case, without being bound by theory, the applicant believes that air spaces, permitting forward venting of hot gases during burning, are created between the semi-cord and the sleeve. The igniter cords were of round cross-sectional profile.
A paste formulation incendiary composition according to the invention was made. 25,0% by weight MOWILITH DM772 water miscible binder (a copolymer dispersion of acr~lic acid esters available from Hoechst South Africa (Proprietary) Limited) was mixed together with 0,625%
by weight POI.YSALZ S, 15,625% potassium perchlorate, 37,5% red lead and 21,25% ferrosilicon. This paste was spread with a blade across a board containing conventional aluminium igniter cord connector tubes inserted in holes therein, and e~tending downwardly'therefrom.
These tubes were filled to the required depth with plugs of the composition.
, ~f~7S7 A diagrammatic drawing is shown in Figure 2, generally designated 10. The board is designated 12, the blade being shown by reference numeral 14 as part of a knife 16. The blade ls shown being drawn in the direction of arrow 18, to spread a mass 20 of the paste on the upper surface 22 of the board into the tubes 24 in the openings in the board. The depth to which the paste enters the tubes is determined by pedestals 26 and the paste forms plugs 28 in the tubes. The upper surfaces of the pedestals can be covered with a suitable tape, such as polytetrafluoroethylene tape, to prevent adhesion of the paste to the pedestals.
The tubes, as shown, were open at both ends, and after withdrawing the tubes from the board the plugs were dried and cross~linked by heating and the ends of the tubes from which the plugs were recessed, were crimped onto lengths of safety fuse by conventional means. Twenty five connector capped fuses made in this way were inserted into conventional plastic adaptors used for such open ended igniter cord connectors, and attached to a length of igniter cord. They all fired.
; Figure 3 shows a diagrammatic representation of the connectors in use, the same reference numerals being used unless otherwise specified. Reference numeral ~, 30 generally shows the arrangement, with the adaptor being shown by reference numeral 32, the igniter cord belng shown by reference numeral 3~, and the safety ~use shown by reEerence numeral 36 crimped as at 38 into the tube, the exposed end 28.1 of the plug in use touching the igniter cord.
In an alternative possible construction the tubes 24 can have the end where the plug is located closed, and a transverse slot through the side wall of the tube and the plug at the closed end for receiving the igniter cord. The closed end is shown at 24.1 and the slot at 24.2 in Figure 3. With this construction the adaptor 32 is not used and the igniter cord is merely pressed into the slot into contact with the plug.
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A composition according to the invention similar to the paste of Example 6 was made Erom 25,0% by weight A272 acrylic binder, 0,625% POLYSALZ S, 15,625% potassium perchlorate, 37,5% red lead and 21,25% ferrosilicon.
This paste was dosed into connector tubes raised on pedestals covered with polytetrafluoroethylene tape.
~6~7~S^7 This arrangement is shown in Figure 4, by reference numeral 40, and unless otherwise specified, ` like reference numerals refer to like parts. The dosing can be effected by any convenient means, and in practice a hypodermic syringe 42 was used.
; 1500 connectors made in this fashion showed no failures in dry burning tests of the type described in Example 6. Also 50 assemblies tested under water and 50 tested under water spray all burnt. When more severe tests were carried out in the assemblies, such as burning after immersion in a water pot pressurised to 30 psi for 10 minutes, it was found to be necessary to seal the open end of the tube opposite the crimped recessed end, by covering the plug with a layer of the acrylic binder used in the incendiary composition for 100% firing.
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Both in Example 6 and in the present Example water was not added to the formulations, because the acrylic binders used in each case contained about 15%
by weight wa-ter which amount was sufficient to render the paste insensitive to match ignition, the other components being added to the binders, and the POLYSALZ S being used to control viscosity. With ~' , .
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, these compositions a possiblity exists tha-t connectors : could be produced merely by dipping the ends of the safety fuses into the compositions, followed by drying, i.e. omitti.ng the aluminium tubes. This connec-tor would however have the disadvantages of ~ow : mechanical strength and possible water pick-up by the black powder core of the safety fuse..
A number of electric fuse heads were made by dipping fuse head skeletons into the composition of . Example 7. After drying, fuse heads with an acceptable appearance were obtained, which were crimped into detonator tubes. In use, all the fuse heads which ignited initiated the detonators, but it was found that a relatively high current (temperature) was required for ignition, and at conventional current strengths the tubes did not all ignite.
A futher paste in accordance with the invention was thus formulated, comprising 24,4% by weight A272, 15,2% potassium perchlorate, 0,6% POLYSALZ S, 36,6%
red lead, 20,7% ferrosilicon and 2,5% pyropowder (comprising 89% by weight nitrocellulose, 7% dinitrotol~ene, and 4% dibutylphalate). In this case, fuse heads were obtained which gave a 100% success rate at the ~, ~ 757 ~25-lower conventional ignition -temperature. It was found that incorporation of the pyropowder lowered the ignition tempera-ture when measured on a differential scanning calorimeter from 431C to 247C, when compared wi-th the formulation of Example 7, without making the water based pas-te sensitive to ini-tiation with a match flame. When the pyropowder was used, 100% success rate was obtained at the lower ignition temperature which is conventionally used for electric fuse heads wherein the incendiary compostions are -typically lead mononitroresorcinate/ potassium chlorate, charcoal/potassium chlorate, nitrocellulose/
diethyl ether, etc. On the other hand, when the pyropowder was omitted, and the formulation according to Example 7 was used, there was in fact a 66% ignition, using the same current strengths as are used for said conventional formulations.
A principal advantage of the invention, when compared with known flexible incendiary compositions capable of burning under water, is that the fire hazard is reduced. Such other flexible incendiary compositions lcnown to the applicant use materials such as nitrocellulose and plasticized organic materials such as nitroglycerin or dibutylphthalate, as their continuous flexible phase. Plas-ticized nitrocellulose is extremely hazardous to process, and the equipment used for the manufacture of the incendiary composition has either to be extremely well protected against accidental ignition or well dispersed so that -the effects of ignition are minimized. Also, because plasticized nitrocellulose does not flow readily at ambient temperatures, it often has to be heated in order to be cast in the required shape. The hazardous nature of the materials determines that mixing times are kept to a minimum, resulting in large variations in the burning speed of the incendiary composition arising from ina~equate mixing in the manufacture. The present invention on the other hand, as it is water based and non-incendive, is inherently less hazardous, does not require to be heated in order to be cast in the required shape, and any desired mixing time can be employed to reduce variations in burning speed.
These advantages are particularly useful, in making waterproof igniter cord which is fast burning in air, and which can burn under water if necessary. In this case, previous semi~cords known to the applicant were made from a slurry incendiary composition typically ~ comprising a mixture of one or more oxidizing agents, one or more.reducing agents, and nitrocellulose dissolved ~.
or suspended in acetone or a similar volatile solvent.
~fl~;'7~7 t This incendiary slurry used in the kettle or bath is ~ extremely sensitive to impact and friction, and after .
coating the semi-cord, it must be heated to dry off the solvent. ~-t this stage the previous processes are particularly dangerous. Use of the slurry composition in accordance with the present invention avoids or at least substantially reduces these dangers. The components of the compositions according to the present invention can now be mixed together in great safety, provided that water is always present and at no time un-til the final drying and processing of the product is a potentially dangerous product present. This enables the process to be carried out in a much simpler and more compact fashion, and permits large batches to be mixed for an extensive period, thereby reducing batch to batch variation and variations in burning speed in a single batch.
~ lso when applied to igniter cord connectors, the applicant is aware that previously the connectors were made of aluminium tubes which were open at both ends or closed at one end and having a slot as described above, and that prior art incendiary products were pressed into these tubes under pressure. When a tube closed at one end was used, the slot was cut to provide a contact area on the incendiary plug for initiation by an igniter -.
cord. Typically, 100 mg of an incendiary connector base composition was gravity fed into an open ended aluminium tub`e and pressed at about 1200 lb. force, followed by 80 mg of black powder pressed in as a pill at the same pressure. The connector base composition was a homogeneous mixture of pyro powder, lead peroxide, antimony sulphide and silicon powder. These connectors were crimped, as described above, onto lengths of safety fuse, for transferring the flame from igniter cord to black powder cored safety fuses. Despite the high pressure used during filling, water was still found to penetrate the previous connectors and to cause the black powder pill to fail. The connectors according to the present inventi.on, on the other hand, are relatively waterproof, and relatively safe to prepare and handle, and whereas -the previous connectors had a failure rate at the 0,1~ level, the failure rate of connectors according to the present invention is comparitively negligible.
In particular the invention relates to an incendiary composition; a method of making the composition; to products including the composition such as igniter cord, an igniter cord connector and an electric fuse head.
According to the invention an incendiary composition comprises an oxidizing agent, a reducing agent, and a water miscible binder, the binder forming the continuous phase of the composition in which the oxidizing agent and reducing agent are dispersed.
`' ' Naturally, if desired, the composition according to the invention can include more than one oxidizing agent, more than one reducing agent and the water miscible binder may also comprise a mixture of materials.
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~4G757 The composition may be malleable, so that products made therefrom such as igniter cord can be flexible, i.e. capable of belng bent or shaped without cracking or breaking.
The composition may be waterproof, in that it is capable of burning af-ter having been wet, for example by being sprayed with water or immersed in water.
Preferably, the composition is capable of burning under water.
The composition may be one in which, after dispersion of the oxidizing agent and reducing agent in the binder, the binder has been cross-linked. This cross-linking may be achieved by any suitable method, such as the use of a suitable catalyst or a two component system, or by subjecting the composition to suitable irradiation, but cross-linking by heat is preferred~
'' The binder may be selected from the group consisting in acrylics, latices, and polyvinyl acetates. The applicant also believes that there may be ~` starches plasticized with polyols, or polybutadienes which can act as suitable blnders ac~ording to the invention.
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f~",L~ 757 The oxidizing agent may be selected from the group consisting in potassium perchlorate, lead dioxide, red lead, potassium nitrate, ammonium perehlorate, sodium perchlorate, potassium permanganate and sodium dichroma-te. The oxidizing agent may be ` sparingly soluble in water, such as potassium perchlorate or substantially insoluble in water, such as red lead, and is preferably, say, no more than twice as soluble as potassium perchlorate at ambient temperatures.
The reducing agen-t may be selected from the group consisting in carbon, silicon, ferrosilicon, aluminium, copper, zinc and tungsten, and is preferably no more than sparingly soluble in water at ambient temperatures.
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Further according to the invention a method of making the composition described above comprises mixing : the components together in the presence of water . followed by drying of the composition.
:, The method may include modifying the viscosity of the mixture by mixing the components together with a viscosity modifier, such as a thickener or an agent which reduces the viscosity of the mixture, .. . ..
.
depending on what is convenient for the process of manufacture, and on the proportions of the various components, including water, in the mixture.
Mixing may be by means of a mechanical mixer. As the presence of water renders the composition safe, the mixing can be performed by almost any type of mixer, such as edge-runner, concrete, planetary and ribbon ~ mixers, and the mixing can be effected for long periods ; of time. secause of this safety, the method may include pumping the mixture, for example via a 15 mm ring main and a Mono pump, from the location where it is mixed to another location prior to drying. In this way the paste or slurry produced can be distributed after mixing to application points by a mechanical distribution system rather than by a manual distribution system.
As the composition is water based, it does not require heating to render it fluid for mixing or handling.
The method may thus involve maintaining the components at ambient temperature prior to drying.
; After the mixing, the binder may be cross-linked.
; As mentioned above, the cross-linking may be effected by the use of a catalyst or a two component system, or the composition may be subjected to suitable irradiation ~;:
~' , ',~
' ~6~7S7 or the cross-linking may be affected by heating. This cross-linking acts to enhance the waterproof qualities of the composition, as the contlnuous phase constituted by the cross-linked binder at least partially encap-sulates or encloses the particles of reducing agent and oxidizing agent dispersed in the binder.
The drying is thus conveniently effected by heating, so that the heating of the drying acts also to cross-link the binder. In ordex to speed up the drying and/or reduce the temperature of the drying, the composition may be subjected to a vacuum during the- drying.
The method may include mixing the components together with a surfactant, such as a wetting agent, to enhance the wettin~ of insoluble components in the mixture, to facilitate preparation of the mixture.
The composition of the invention can be put to a number of uses, such as the manufacture of igniter cord, igniter cord connectors, delay elements, flares, fuse heads, or the like.
The invention thus provides an igniter cord which cornprises a core having a composition according to the invention as described above, applied thereto.
The core may be a metal wire, or the core may be made up of a plurality of yarns or strands, such as textile yarns and/or metal strands.
The core may be enclosed by a flexible extruded incendiary sleeve. The incendiary sleeve may be of a flexible incendiary composition as described above. At least part of the core, under the sleeve may be treated with an incendiary material, and the incendiary material may be an incendiary composition, preferably flexible, as described above. Thus a composition according to the invention as described above may be used for the sleeve and/or for treating the core under the sleeve, the treating of the core with the composition under the sleeve being of particular application when the core is made up of a plurality of yarns or strands.
The igniter cord may have an extruded plastics outer coating, in which case the cross-sectional profile of the cord may be of angular outline. Having the cross-sectional profile of the cord of angular outline, such as square outline, is believed to enhance the formation of air spaces between the coa~ing and the ~ .
' '' , , , .
~675~7 cord, thereby permitting forward venting of hot gases during burning and thus increasing the burning speed of the igni-ter cord.
It will be appreciated that an important aspect of the process of making -the incendiary composition according to the invention is that the mixing can take place in the presence of water. The drying of the composition can be natural in -that the composition is merely left until it dries by itself, or it can be forced in that it is subjected to heating and/or a vacuum, etc, to cause rapid drying. Thus the mixture, prior to drying, is incapable of being ignited with a match, but will be capable of such ignition after drying. The choice of suitable components and the proportions used in the mixture enable a slurry or paste to be formed which can be pumped, or formed into any suitable shape rior to drying, and can provide an incendiary composition which after drying can be flexible and can be capable of burning under water. Provided sufficient water is always present at the stage when the oxidizing agents are brought together with the reducing agents or fuels, for example by always adding water to the mixer first, the order of addition of the components during mixing canno-t affect the non-incendivity of the paste. Furthermore, ~ 6'7~7 g ~
mixing times and rates of mixing or rates of addition can be adjusted to any desired value in order to optimize production rates.
In the making of igniter cords, any suitable means can be used to apply the paste or slurry at the application point to the metal wire or the yarns or strands which make up the core of the igniter cord.
Suitable means of application can be, for example, kettle application, extrusion by conventional worm extruders, Mono pump feeding or auger feeding, the iqniter cord which results preferably being flexible and waterproof r and being capable o burning under water as described above.
Although simple extrusion of the composition according to the invention onto cores made of metallic wire such as a single copper wire, or onto composite cores made up of yarn threads or metallic strands, may be suitable to provide igniter cord o~ relatively slow burning rates such as about 30 - 45 seconds a metre, such extrusion can be unsuitable for providing igniter cords having a burning rate faster than about 16 seconds a metre. The reason for this i~s that the burning rate is increased by reducing the quantity~of water miscible binder present in the composition, and the _ -- .. ~ . .. .. . .
excessive reduction of this binder can lead to an unacceptable loss of flexibility in the igniter cord product.
To make a fast burning igniter cord, typically having a burning rate of 8 - 16 seconds a metre or as fast as one second a me-tre, a composite core made up of spun yarn or threads of metallic and/or non-metallic nature can be used. This core is first drawn through a kettle or bath containing a slurry-like incendiary composition to form what is called a semi-cord. This semi-cord is then coated by means oE extrusion with a plastic incendiary sleeve. This process has the advantage that longitudinally extending air spaces created between the semi-cord and its extruded flexible incendiary sleeve permit forward venting of hot gases produced during combustion which increases the burning rate of the cord over that of cords which do not have the air spaces and which rely on simple forward heat conduction to determine the burning rate. The slurry-like incendiary composition in the kettle or bath and the incendiary sleeve are preferably both of compositions including a water miscible binder according to the invention as described above. However, as mentione'd above either the slurry-like incendiary composition or the incendiary sleeve may be of conventional incendiary compositions which do not include a water miscible binder.
,7 The invention also provides an igniter cord connector comprising a metal tube having a plug of an incendiary composition according to the invention as described above, the plug being recessed from an open end of the tube.
Both ends of the tube may be open, the plu~ extending to the end of the tube opposite the end from which it is recessed. Instead, the connector may be of a construction in which the end of the tube opposite the open end is closed, the side of the tube at the closed end having a transverse slot therein for receiving an igniter cord, the slot extending through the plug. In each case the open end of the tube from which the plug is recessed is intended for crimping or other suitable connection to a safety fuse, and the ign1ter cord can thus be provided with such safety fuse inserted into and connected to the end of the tube from which the plug is recessed, and "open end of the tube" is to be construed accordingly as covering the situation where it is in fact closed , bu-t closed with a safety fuse inserted into it.
The exposed part of the plug remo~te fro~ the recessed end ie the opposite end of the tube when both ends of the tube are open or the part of the plug ., exposed by the slot when -the tube has a slot, is intended for being initiated by an igniter cord, and this exposed part may be sealed against water penetration, conveniently by a suitable sealant, and depending on the nature of the water miscible binder used for the incendiary composition according to the invention, this binder may be suitable for use as the sealant.
The invention also provides an electric fuse head comprising a fuse head skeleton enclosed by a composition according to Claim 1.
In the drawings;
Figure 1 shows in graphical form the variation of burning speed in proportion to the level of binder in cords;
Figure 2 shows a connector composition being placed into a mould;
Figure 3 shows a connector and ignitercord combination;
and Figure 4 shows mould filling with a syringe injector system.
The invention will now be described with reference to the following illustrative and non-limiting Examples.
A paste composition in accordance with the invention was made by thoroughly mixing together, on a weight basis, 14.5%
water, 8.6% of a water miscible acrylic binder available as A272 from Revertex S.A. (Proprietary) Limited, Durban, 16.1% potassium perchlorate, 38.7% red lead, 21.9% ferrosilicon and 0.2% of a 10% weight a~ueous carboxymethyl cellulose solution. The potassium perchlorate and red lead were the oxidizing agents --, _ ,_ -~ .
, while the ferrosilicon and carboxymethyl cellulose respectively formed the reducing agent and a thickener.
This composition beEore drying was Eound to be incapable of ignition with a match, and it was arranged in the mixing that the oxidizing and reducing agents were brought into contact in the presence of the water, so that no stage was an incendiary material produced prior to drying.
The composition according to Example 1, prior to drying, was extruded as a water-based paste onto a copper wire using an auger feeder, to provide an incendiary sleeve around the copper wire, and the paste was dried at a sufficient temperature to cause cross-linking of the acrylic binder. The product was then finished by extruding a plastics (polyethylene) outer coating around the sleeve to provide a flexible incendiary igniter cord capable of burning under water which burnt at a rate of 24,5 seconds a metre in air. The use of a water-based paste permitted thorough mixing leading to enhanced reproducibility of the igniter cord burning speed. Ten one metre lengths of the igniter cord burnt at an average value of 24,5 seconds a me-tre with a standard deviation of 0,97 seconds a metre, whereas igniter cord of comparable speed made by conventional methods burnt at 23,9 seconds a metre with a standard deviation of 1,99 seconds a metre.
It was found that the burning speed of the igniter cord produced according to Examples 1 and 2 can be altered easily by a number of methods, for example by changing the proportion of binder in the composition produced according to Example 1, or by changing the shape of the extrusion die. When the incendiary sleeve was extruded with a square die, the cord was found to burn more quickly than with a round die, and without being bound by theory it is believed by the applicant that the use of a square die having an angular cross-sectional profile leads to the formation of air spaces between the ethylene outer coat and the sleeve, leading to forward venting of hot gases during burning and enhance the speed.
The process of Example 1 was repeated with variations in the proportion of binder, and varia~ion of burning speed in air with variation in the proportion of binder for round cords is shown in Figure 1.
.. , .,.. ~.. ,, .. , ... ... . ~ .
It was found -that paste rheology could be altered to suite the method oE applica-tion. For example, a runny paste of approximate viscosity of 1000 poise suitable ~or kettle application could be produced, whereas a thick paste having a viscosity of about 5000 poise could be produced for auger feeding. The viscosity was altered by changing the amount of water in the composition and/or by the incorporation of suitable viscosity modifiers. Thus in Example 1 14j5% water was employed to ensure non-incendivity of the wet paste, but as a thick paste was required for auger feeding 0,2% of the 10% carboxymethyl cellulose solution was added as a thickener.
An incendiary composition in the form of a runny paste in accordance with the invention was made having a composition of 150 parts by weight of water, 40 parts by weight of a polyvinyl acetate water miscible binder available as MOWILITH*DC from Hoechst South Africa (Proprietary) Limited, Industria, 75 parts by weight of potassium perchlorate, 175 parts by weight of red lead and 100 parts by weight ferrosilicon. This incendiary paste was runny and was suitable for coating a core comprising cotton cord, by drawing the core through an application kettle.
, * TM
,, ;
.; .
~ 67~i~
The proportion of water was then reduced to 70 parts by weight (the proportions of the other components being unaltered) and 2 parts by weight of a viscosity modifier (reducer) comprising ammonium polybutylacrylate available as POLYSALZ*S from BASF South Africa (Proprietary) Limited, Johannesburg, was incorporated, to obtain a runny paste of substantially the same viscosity capable of application to a cotton cord by drawing through an application kettle in the same fashion.
In each case a round igniter cord was produced, which was not provided with an extruded sleeve and was not coated with a plastics coating, and which was found to burn at a speed of 37 seconds a metre.
Alternative formulations to the composition of Example 1 were made and tested, in which the potassium perchlorate and particularly the red lead were replaced with other oxidizing agents such as lead dioxide, -~ potassium nitrate, ammonium perchlorate, sodium perchlorate, potassium permanganate and sodium dichromate. These formulations were all found to provide suitable general purpose incendiary compositions with the advantage that, before drying, the enhanced safety provided by the invention was present. However, as the oxidizing * TM
fif ~
. ~ . . .
" 1~4~57 agents tested were all more soluble in water than red lead, in the production of igniter cord they tended to crystallize at the surface of the cord during drying, having been brought to the surface by the evaporating water. They thus suffered loss of flexibility and waterprooEness, and were found to be somewhat inhomoge-neous, although burning rates were unaffected. Red lead on the other hand, is virtually insoluble in water, and potassium perchlorate is only sparingly soluble in water.
In these tests a surfactant was used as a wetting agent, to facilitate the paste preparation, and to enhance the wetting of the insoluble components of the paste. In particular, the surfactant available as TAMOL NNO from BASF South Africa (Proprietary) Limited, ~ohannesburg, compr~sing the sodium salts of the condensation product of naphthalene sulfonic acid with formaldehyde, was used. The TAMOL was used in a 1%
aqueous solution.
:
- An incendiary composition in the form of a slurry in accordance with the invention was made up from 1340 parts by weight of a 1% by weight TAMOL solution, 150 *TM
.
s, ,~, . . .
~6757 parts by weight of A272 acrylic binder, 250 parts by weight potassium perchlorate, 600 parts by weight red lead and 340 parts by weight ferrosilicon together with 3,25 parts by weight of a 10% by weight carboxymethyl cellulose solution. This slurry was applied by drawing two parallel paper yarns -through a kettle containing the slurry, followed by drying, followed by countering (spinning) with one jute yarn and three rayon yarns, to produce a semi-cord.
This semi-cord was then coated by means of extrusion with a conventional plastic incendiary composition (not according to the invention) comprising suitable proportions of red lead and potassium perchlorate as oxidizing agents, a suitable proportion of ferrosilicon as reducing agent, and a suitable proportion of plasticized nitrocellulose as a binder, followed by a polyethylene outer coating or sheath. Burning of twenty five one metre lengths produced a mean burning rate of 7,7 seconds a metre with a standard deviation of 0,56 seconds a metre.
Use of the same slurry, but with three parallel paper yarns having the slurry applied thereto and countered (spun) with three rayon ya~ns followed by coating with the nitrocellulose-containing plastic . ~
incendiary composition and the polythene sheath, yielded an igniter cord which burnt at a rate of 2,3 seconds a metre with a standard deviation of 0,~3 seconds a metre.
The cords produced above and haying an extruded sleeve of the nitrocellulose-containing plastic incendiary composition did not burn under water. However, when the extruded sleeve was replaced by a sleeve according to the formulation of Example 1, an igniter cord was obtained capable of burning under water. Likewise, when the slurry applied in the kettle to the parallel paper yarns was replaced by a conventional slurry-like incendiary composition com~rising one or more suitable oxidizing agents, one or more suitable reducing agents and nitrocellulose dissolved or suspended in acetone or a similar volatile solvent to form the semi-cord, followed by extrusion of a sleeve of a composition according to the invention of the formulation of Example 1, and a polythene sheath, a flexible igniter cord was obtained, which was once again waterproof, and capable of burning at 6 seconds a metre in air, and 30 seconds a metre under water.
fast burning flexible igniter cord could thus be obtained by extruding a sleeve of flexible incendiary material according to the invention on semi-cord, the i75~7 semi-cord being produced either from a sluxry in accordance with the invention or a conventional slurry. A conventional plastic incendiary composition sleeve can also be extruded over a semi-cord made with slurry in accordance with the invention, although this does not have the advantage oE waterproofness. In each case, without being bound by theory, the applicant believes that air spaces, permitting forward venting of hot gases during burning, are created between the semi-cord and the sleeve. The igniter cords were of round cross-sectional profile.
A paste formulation incendiary composition according to the invention was made. 25,0% by weight MOWILITH DM772 water miscible binder (a copolymer dispersion of acr~lic acid esters available from Hoechst South Africa (Proprietary) Limited) was mixed together with 0,625%
by weight POI.YSALZ S, 15,625% potassium perchlorate, 37,5% red lead and 21,25% ferrosilicon. This paste was spread with a blade across a board containing conventional aluminium igniter cord connector tubes inserted in holes therein, and e~tending downwardly'therefrom.
These tubes were filled to the required depth with plugs of the composition.
, ~f~7S7 A diagrammatic drawing is shown in Figure 2, generally designated 10. The board is designated 12, the blade being shown by reference numeral 14 as part of a knife 16. The blade ls shown being drawn in the direction of arrow 18, to spread a mass 20 of the paste on the upper surface 22 of the board into the tubes 24 in the openings in the board. The depth to which the paste enters the tubes is determined by pedestals 26 and the paste forms plugs 28 in the tubes. The upper surfaces of the pedestals can be covered with a suitable tape, such as polytetrafluoroethylene tape, to prevent adhesion of the paste to the pedestals.
The tubes, as shown, were open at both ends, and after withdrawing the tubes from the board the plugs were dried and cross~linked by heating and the ends of the tubes from which the plugs were recessed, were crimped onto lengths of safety fuse by conventional means. Twenty five connector capped fuses made in this way were inserted into conventional plastic adaptors used for such open ended igniter cord connectors, and attached to a length of igniter cord. They all fired.
; Figure 3 shows a diagrammatic representation of the connectors in use, the same reference numerals being used unless otherwise specified. Reference numeral ~, 30 generally shows the arrangement, with the adaptor being shown by reference numeral 32, the igniter cord belng shown by reference numeral 3~, and the safety ~use shown by reEerence numeral 36 crimped as at 38 into the tube, the exposed end 28.1 of the plug in use touching the igniter cord.
In an alternative possible construction the tubes 24 can have the end where the plug is located closed, and a transverse slot through the side wall of the tube and the plug at the closed end for receiving the igniter cord. The closed end is shown at 24.1 and the slot at 24.2 in Figure 3. With this construction the adaptor 32 is not used and the igniter cord is merely pressed into the slot into contact with the plug.
.
A composition according to the invention similar to the paste of Example 6 was made Erom 25,0% by weight A272 acrylic binder, 0,625% POLYSALZ S, 15,625% potassium perchlorate, 37,5% red lead and 21,25% ferrosilicon.
This paste was dosed into connector tubes raised on pedestals covered with polytetrafluoroethylene tape.
~6~7~S^7 This arrangement is shown in Figure 4, by reference numeral 40, and unless otherwise specified, ` like reference numerals refer to like parts. The dosing can be effected by any convenient means, and in practice a hypodermic syringe 42 was used.
; 1500 connectors made in this fashion showed no failures in dry burning tests of the type described in Example 6. Also 50 assemblies tested under water and 50 tested under water spray all burnt. When more severe tests were carried out in the assemblies, such as burning after immersion in a water pot pressurised to 30 psi for 10 minutes, it was found to be necessary to seal the open end of the tube opposite the crimped recessed end, by covering the plug with a layer of the acrylic binder used in the incendiary composition for 100% firing.
.~ .
Both in Example 6 and in the present Example water was not added to the formulations, because the acrylic binders used in each case contained about 15%
by weight wa-ter which amount was sufficient to render the paste insensitive to match ignition, the other components being added to the binders, and the POLYSALZ S being used to control viscosity. With ~' , .
' ;
, these compositions a possiblity exists tha-t connectors : could be produced merely by dipping the ends of the safety fuses into the compositions, followed by drying, i.e. omitti.ng the aluminium tubes. This connec-tor would however have the disadvantages of ~ow : mechanical strength and possible water pick-up by the black powder core of the safety fuse..
A number of electric fuse heads were made by dipping fuse head skeletons into the composition of . Example 7. After drying, fuse heads with an acceptable appearance were obtained, which were crimped into detonator tubes. In use, all the fuse heads which ignited initiated the detonators, but it was found that a relatively high current (temperature) was required for ignition, and at conventional current strengths the tubes did not all ignite.
A futher paste in accordance with the invention was thus formulated, comprising 24,4% by weight A272, 15,2% potassium perchlorate, 0,6% POLYSALZ S, 36,6%
red lead, 20,7% ferrosilicon and 2,5% pyropowder (comprising 89% by weight nitrocellulose, 7% dinitrotol~ene, and 4% dibutylphalate). In this case, fuse heads were obtained which gave a 100% success rate at the ~, ~ 757 ~25-lower conventional ignition -temperature. It was found that incorporation of the pyropowder lowered the ignition tempera-ture when measured on a differential scanning calorimeter from 431C to 247C, when compared wi-th the formulation of Example 7, without making the water based pas-te sensitive to ini-tiation with a match flame. When the pyropowder was used, 100% success rate was obtained at the lower ignition temperature which is conventionally used for electric fuse heads wherein the incendiary compostions are -typically lead mononitroresorcinate/ potassium chlorate, charcoal/potassium chlorate, nitrocellulose/
diethyl ether, etc. On the other hand, when the pyropowder was omitted, and the formulation according to Example 7 was used, there was in fact a 66% ignition, using the same current strengths as are used for said conventional formulations.
A principal advantage of the invention, when compared with known flexible incendiary compositions capable of burning under water, is that the fire hazard is reduced. Such other flexible incendiary compositions lcnown to the applicant use materials such as nitrocellulose and plasticized organic materials such as nitroglycerin or dibutylphthalate, as their continuous flexible phase. Plas-ticized nitrocellulose is extremely hazardous to process, and the equipment used for the manufacture of the incendiary composition has either to be extremely well protected against accidental ignition or well dispersed so that -the effects of ignition are minimized. Also, because plasticized nitrocellulose does not flow readily at ambient temperatures, it often has to be heated in order to be cast in the required shape. The hazardous nature of the materials determines that mixing times are kept to a minimum, resulting in large variations in the burning speed of the incendiary composition arising from ina~equate mixing in the manufacture. The present invention on the other hand, as it is water based and non-incendive, is inherently less hazardous, does not require to be heated in order to be cast in the required shape, and any desired mixing time can be employed to reduce variations in burning speed.
These advantages are particularly useful, in making waterproof igniter cord which is fast burning in air, and which can burn under water if necessary. In this case, previous semi~cords known to the applicant were made from a slurry incendiary composition typically ~ comprising a mixture of one or more oxidizing agents, one or more.reducing agents, and nitrocellulose dissolved ~.
or suspended in acetone or a similar volatile solvent.
~fl~;'7~7 t This incendiary slurry used in the kettle or bath is ~ extremely sensitive to impact and friction, and after .
coating the semi-cord, it must be heated to dry off the solvent. ~-t this stage the previous processes are particularly dangerous. Use of the slurry composition in accordance with the present invention avoids or at least substantially reduces these dangers. The components of the compositions according to the present invention can now be mixed together in great safety, provided that water is always present and at no time un-til the final drying and processing of the product is a potentially dangerous product present. This enables the process to be carried out in a much simpler and more compact fashion, and permits large batches to be mixed for an extensive period, thereby reducing batch to batch variation and variations in burning speed in a single batch.
~ lso when applied to igniter cord connectors, the applicant is aware that previously the connectors were made of aluminium tubes which were open at both ends or closed at one end and having a slot as described above, and that prior art incendiary products were pressed into these tubes under pressure. When a tube closed at one end was used, the slot was cut to provide a contact area on the incendiary plug for initiation by an igniter -.
cord. Typically, 100 mg of an incendiary connector base composition was gravity fed into an open ended aluminium tub`e and pressed at about 1200 lb. force, followed by 80 mg of black powder pressed in as a pill at the same pressure. The connector base composition was a homogeneous mixture of pyro powder, lead peroxide, antimony sulphide and silicon powder. These connectors were crimped, as described above, onto lengths of safety fuse, for transferring the flame from igniter cord to black powder cored safety fuses. Despite the high pressure used during filling, water was still found to penetrate the previous connectors and to cause the black powder pill to fail. The connectors according to the present inventi.on, on the other hand, are relatively waterproof, and relatively safe to prepare and handle, and whereas -the previous connectors had a failure rate at the 0,1~ level, the failure rate of connectors according to the present invention is comparitively negligible.
Claims (26)
1. An incendiary composition comprising an oxidizing agent, selected from the group of potassium perchlorate, lead dioxide, red lead, potassium nitrate, ammonium perchlorate, sodium perchlorate, potassium permanganate sodium dichromate and mixtures thereof, a reducing agent, selected from the group of carbon, silicon, ferrosilicon, aluminium, copper, zinc, tungsten and mixtures thereof, and a cross-linkable water miscible binder, selected from the group of acrylics, latices, and polyvinyl acetates, the binder forming the continuous phase of the composition in which the oxidizing agent and reducing agent are dispersed.
2. A composition as claimed in Claim 1, which is malleable.
3. A composition as claimed in Claim 1, which is waterproof.
4. A composition as claimed in Claim 3, which is capable of burning under water.
5. A method of making a composition as claimed in Claim 1, which comprises mixing the components together in the presence of water followed by drying of the composition.
6. A method as claimed in Claim 5, which includes modifying the viscosity of the mixture by mixing the components together with a viscosity modifier.
7. A method as claimed in Claim 6, in which the viscosity modifier is a thickener.
8. A method as claimed in Claim 6, in which the viscosity modifier is an agent which reduces the viscosity of the mixture.
9. A method as claimed in Claim 5, in which the mixing is by means of a mechanical mixer.
10. A method as claimed in Claim 5, which includes the step of pumping the mixture from the location where it is mixed to another location prior to drying.
11. A method as claimed in Claim 5, in which the components and mixture are maintained at ambient temperature prior to drying.
12. A method as claimed in Claim 5, in which, after the mixing, the binder is cross-linked.
13. A method as claimed in Claim 12, in which the cross-linking is effected by heating.
14. A method as claimed in Claim 5, which includes mixing the components together with a surfactant.
15. A composition according to Claim 1 in the form of a core-coated igniter cord.
16. An igniter cord as claimed in Claim 15, in which the core is a metal wire.
17. An igniter cord as claimed in Claim 15, in which the core is made up of a plurality of yarns or strands.
18. An igniter cord as claimed in Claim 15, in which the core is enclosed by a flexible extruded incendiary sleeve.
19. An igniter cord as claimed in Claim 15, in which at least part of the core, under the sleeve, is treated with an incendiary material.
20. An igniter cord as claimed in Claim 15, which has an extruded plastics outer coating.
21. An igniter cord as claimed in Claim 20, in which the cross-sectional profile of the cord is of angular outline.
22. An incendiary composition according to Claim 1 in the form of an igniter cord connector, said connector comprising a metal tube containing a plug of the said incendiary composition, the said plug being recessed from an open end of the tube.
23. A connector as claimed in Claim 22, in which both ends of the tube are open, the plug extending to the end of the tube opposite the end from which it is recessed.
24. A connector as claimed in Claim 22, in which the end of the tube opposite the open end is closed, the side of the tube at the closed end having a transverse slot therein for receiving an igniter cord, the slot extending through the plug.
25. A connector as claimed in Claim 22 or Claim 23, in which the exposed part of the plug remote from the recessed end is sealed against water penetration.
26. An incendiary composition, according to Claim 1 in the form of an electrically actuable fuse head.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ZA19783542A ZA783542B (en) | 1978-06-21 | 1978-06-21 | Incendiary composition and process of production |
| ZA78/3542 | 1979-02-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1146757A true CA1146757A (en) | 1983-05-24 |
Family
ID=25573071
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000330240A Expired CA1146757A (en) | 1978-06-21 | 1979-06-21 | Incendiary composition and process of production |
Country Status (5)
| Country | Link |
|---|---|
| BR (1) | BR7903843A (en) |
| CA (1) | CA1146757A (en) |
| NZ (1) | NZ190759A (en) |
| ZA (1) | ZA783542B (en) |
| ZW (1) | ZW11279A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2635134C1 (en) * | 2016-08-02 | 2017-11-09 | Акционерное общество "Федеральный научно-производственный центр "Научно-исследовательский институт прикладной химии" | Incendiary effect composition |
| CN113480389A (en) * | 2021-07-09 | 2021-10-08 | 北京理工大学 | Preparation method of high-explosive-capacity synergistic energetic micro-projectile |
-
1978
- 1978-06-21 ZA ZA19783542A patent/ZA783542B/en unknown
-
1979
- 1979-06-12 ZW ZW112/79A patent/ZW11279A1/en unknown
- 1979-06-18 BR BR7903843A patent/BR7903843A/en unknown
- 1979-06-18 NZ NZ190759A patent/NZ190759A/en unknown
- 1979-06-21 CA CA000330240A patent/CA1146757A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2635134C1 (en) * | 2016-08-02 | 2017-11-09 | Акционерное общество "Федеральный научно-производственный центр "Научно-исследовательский институт прикладной химии" | Incendiary effect composition |
| CN113480389A (en) * | 2021-07-09 | 2021-10-08 | 北京理工大学 | Preparation method of high-explosive-capacity synergistic energetic micro-projectile |
Also Published As
| Publication number | Publication date |
|---|---|
| ZW11279A1 (en) | 1981-01-21 |
| NZ190759A (en) | 1982-09-07 |
| BR7903843A (en) | 1980-04-01 |
| ZA783542B (en) | 1980-03-26 |
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