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PATENT SPECIFICATION 644,073

Inventor: ALEXANDER CANTLAY HUTCHISON.

Date of filing Complete Specification: Aug. 11, 1948.
Application Date: Oct 10, 1947. No. 27240/47.
Complete Specification Published: Oct. 4, 1950.

PROVISIONAL SPECIFICATION

Improvements in and relating to Solid Gas Generating Charges

We, IMPERIAL CHEMICAL INDUSTRIES LIMITED, of Imperial Chemical House, Millbank, London, S.W.1, a British Company, do hereby declare the nature of this invention to be as follows:—

The present invention relates to improvements in solid gas generating charges of the kind capable of propagating through themselves a self-sustaining exothermic non-detonating gas-evolving decomposition when a merely local portion of the charge is heated from room temperature to the temperature at which its active decomposition begins. Such gas-generating charges have found application for a variety of purposes including, for instance, the activation of gas pressure operated mechanical devices, blasting operations, the dispersion of volatilisable pecticides [sic], insect repellants, rodenticides, propulsion of rockets and the expulsion of liquids from containers such as fire extinguishers.
It is known that guanidine nitrate undergoes an exothermic gas evolving decomposition when it is strongly heated, but under atmospheric pressure conditions the reaction does not sustain itself if a portion only of a quantity of the compound is heated from atmospheric temperature to the temperature at which decomposition begins, unless external heating is maintained. The decomposition leads to the production of steam, nitrogen, ammonia and oxides of carbon, but there is also formed a certain amount of a difficultly fusible yellow nitrogenous organic residue.
When the conditions are such that the prevailing gas pressure is sufficiently high, namely of the order of 70 atmospheres, once the reaction has been locally initiated it will sustain itself throughout a mass of the guanidine nitrate and under, such gas pressure conditions the products are almost wholly gases and vapours.
It has been proposed to provide charges capable of decomposing with a high yield of permanent gases when locally heated by a non-detonating element at lower pressure than guanidine nitrate, said mixtures comprising guanidine nitrate with a proportion of a metallic hypophosphite or ammonium hypophosphite whereby if desired charges capable of supporting their decompositions even at atmospheric pressure when locally heated may be obtained.
Owing to the nature or amount of the residue the hypophosphites leave behind or other disadvantages attendant on their employment, these charges have only a limited applicability and it would still be desirable to provide improved gas generating charges based on guanidine nitrate and capable of self-sustained decomposition under conditions of much lower gas pressure than guanidine nitrate alone.
It is also known that the pressure required to render possible the self-sustained decomposition of a charge based on guanidine nitrate may be progressively reduced by making up the guanidine nitrate into charges with progressively increasing amounts of colloided nitrocellulose as a binding agent by mixing the guanidine nitrate with a solution of nitrocellulose in a volatile solvent, forming the resulting paste into the required shape and evaporating off the volatile solvent, but the use of a volatile solvent adds to the expense and necessitates a drying operation, while the applicability of this method is also somewhat limited.
We have now found that gas generating charges suitable for a variety of purposes free from the disadvantages attendant on the use of hypophosphites or gelatinised nitrocellulose and capable of self-sustained non-detonating decomposition when merely locally heated, with a high yield of hot gases under considerably lower gas pressures than are required for guanidine nitrate, may be obtained by the use in admixture with guanidine nitrate of a polynitro-phenol or a polynitroso-phenol.

In the absence of diluents or heat-absorbing ingredients a proportion of the polynitrophenol or polynitroso-phenol amounting to about 8 to 20 per cent. of the weight of the guanidine nitrate suffices to render the composition capable of self-sustained decomposition when locally heated even under atmospheric pressure condition. As a polynitrophenol, it is preferred to employ 2:4 dinitro-resorcinol, but 2:4:6 trinitro-resorcinol, 2:4 dinitroso-resorcinol 4: 6 dinitro-orthocresol; 3:5 dinitro-catechol, 2:6 dinitro-paracresol, and 3:5 dinitro-salicylic acid may also be used. If desired an aliphatic carboxylic acid selected from the group consisting of tartaric, maleic, citric and fumaric acids may be employed in partial replacement of the polynitro-phenol or polynitroso-phenol. It is an advantage of the invention that the compositions may be made by simple admixture of the ingredients, and that when the charge is required to be of compact structure and predetermined form so that it will react only on its exposed external surface it may be made by compressing the mixture into a mould of the desired shape. Moreover, if it is required to protect a portion of the surface of the compact charge from the hot gases evolved by means of an adherent covering of heat-insulating material, this may if desired be done in the course of the pressing operation instead of applying protective material to the surface of the charge after it has been shaped.
When charges made up from guanidine nitrate and a polynitro-phenol or polynitroso-phenol are consumed under atmospheric pressure conditions or at comparatively low super-atmospheric working pressures e.g. up to about 10 atmospheres, their decomposition into gaseous products is not quite complete, and they leave a certain amount, (usually 15 to 20%), of the difficultly fusible nitrogenous organic residue already referred to; and at these pressures the gases contain appreciable quantities of vaporised condensable organic materials, the presence of which may be undesirable in certain applications of the charges e.g. if they are to be used in driving engines or operating other mechanical devices where these organic vapours can condense and cause fouling of pipes or moving parts.
We have also found however that the inclusion of a very small proportion of vanadium pentoxide amounting to about 0.2 to 1 per cent. of the weight of the guanidine nitrate has the effect of completing the decomposition of the guanidine nitrate thus obviating the formation of the aforesaid yellow difficultly fusible organic residue and correspondingly increasing the yield of hot gases at working pressures at which this residue would otherwise be formed; and we preferably include in the charge such a proportion of vanadium pentoxide or the equivalent proportion of a chemically equivalent vanadium compound e.g. ammonium vanadate.
We have further found that the condensable vaporised organic compounds that would otherwise be formed at pressures near atmospheric may be destroyed as a result of an exothermic reaction further increasing the hot gas yield, by causing the mixture of gases and vapours, before cooling takes place, to pass over suitable heat resisting catalytic solid surfaces such as those of iron, steel or platinum wire gauze or asbestos, or including in the composition of the charge a small percentage of asbestos fibre of other heat resisting material characterised by a large surface and amounting to not less than about 0.25% of the weight of the charge. The large surface material also steadies the self supporting characteristics of the reaction and holds together the ash of the charge. It may be desirable to include a small percentage of potassium nitrate in the charge, amounting, for instance, to about 0.25 to 1%, since the potassium nitrate assists the reaction between the gases and vapours on the solid catalytic surface. The use of the potassium nitrate is especially desirable if the charge is in an unusually cold condition before it is locally ignited, or in an environment such that the gases and vapours are at a lower temperature than that at which they would normally be generated.
Charges made in accordance with the invention may be used for instance for actuating gas pressure operated mechanical devices, e.g. for driving engines, or for operating pneumatic tools, for operating fire extinguishers, for propulsion of rockets and other gas escape reaction propelled devices for dispersing insecticidal or the like substances, for making coloured smokes, or for safety blasting operations by means of blasting assemblies in which the charge is caused to undergo decomposition in a pressure resisting container adapted to vent the gases once a predetermined pressure has been built up within the container. It will be understood that according to the purpose for which the charge is required it may be in powder, granular or compact form of any required shape, and may or may not include ingredients for reducing or raising the temperature of the gases it generates.
Charges in accordance with the invention modified by the inclusion in their composition of thermally volatilisable effect materials, which may be for instance insect repellants; insecticides, fungicides, bacteriacides [sic] and other pesticides; smoke producing compounds or coloured dyestuffs, may be employed for volatilising and dispersing the effect material. In this case the charge will usually be required to decompose under atmospheric pressure conditions; and if the effect material is an organic compound it will be understood that if the charge is to include asbestos fibre or other material of large surface characteristics its composition must be such that the gases and vapours will not undergo to any extent a reaction on its surface that would destroy the volatilisable compound in the gas stream. The volatilisation of the organic compound has a cooling action so that if sufficient of this composition is used the temperature will be too low for any such undesired surface reaction to take place. 4:6 Dinitro-ortho-cresol is an example of a polynitro-phenol that has itself marked insecticidal and arachnicidal properties.
The invention is further illustrated by the following examples, in which the parts are parts by weight.

Example 1.

A mixture of the composition:—

Guanidine nitrate		88.75%
2:4 dinitro-resorcinol		10.0%
Asbestos fibre		0.5%
Vanadium pentoxide		0.5%
Potassium nitrate		0.25%

was subjected to ball milling until the composition was well mixed and pulverised. 3 lbs. of the mixture was then loaded in four equal increments into a 3" diameter open ended steel tube lined with compressed asbestos fibre sheeting, each increment being pressed for 1 minute at 7000 lb. per square inch the compressed composition occupying all but one inch at each end of the length of the tube. A hole of 1 inch diameter was then drilled axially through the length of the compressed composition. Four or five circles of iron wire gauze each of 3" diameter and of a mesh ranging from 10 to 50 to the inch (BSS) were fitted into one end of the tube and an electrical ignition system including a rod of cordite weighing 20 grams was arranged at the other end of the tube with the. cordite extending into the drilled channel.
The tube containing the composition was used to operate a motor of rotary blower design at a progressively increasing speed at a constant working pressure of about 120 lbs. per square inch. The charge left an incombustible skeleton amounting to less than 1.25% of the weight thereof, without depositing any condensed organic material in the apparatus.

Example 2.

A mixture of the composition:—

Guanidine nitrate		88.7%
2:4 dinitro-resorcinol		9.8%
Potassium nitrate		0.25%
Vanadium pentoxide		0.5%
Mineral oil		0.5%
Asbestos fibre		0.25%

was subjected to ball mixing until the ingredients were well mixed and the form of a fine powder. 20 gms. of the mixture were pressed in a tubular mould 0.95 inches in diameter lined with asbestos paper under a pressure sufficient to give a well consolidated pellet. The pellet with its asbestos sheath was extruded from the mould and fitted into a cylindrical container of approximately 1" diameter closed at one end and fitted with a screw-on cap at the other end carrying a jet 0.055 inch in diameter. The ignition system for the pellet at the open end consisted of a sliver of cordite held on the surface of the composition by means or a tightly fitting circle of 60 mesh BSS stainless steel wire cloth with a length of thin black powder fuse running from the cordite to the exterior through the jet in the cap or the container.
This miniature jet motor formed the propulsion unit of a model racing car. The ignition was brought about by igniting the fuse with a match which ignited the cordite, which in turn locally heated the composition of the charge to the temperature at which the evolution of the gases became active, the decomposition then sustaining itself through the charge. In this manner a thrust of 3 ozs. weight lasting for 20 seconds was exerted on the model racing car. The ash was a coherent skeleton of the pellet and amounted to about 1% of its weight.

Example 3.

A mixture of the composition:—

Guanidine nitrate		67%
4:6 dinitro-o-cresol		18.0%
Alpha - alpha - bis - (parachloro-
phenyl) - beta - beta - beta -
trichloroethane (D.D.T.)		15%

It is an advantage of the invention that the compositions may be made by simple admixture of the ingredients

was prepared by grinding the ingredients together until they were well mixed in the form of a fine powder. 20 gms of the mixture were consolidated into the form of a pellet 1 inch in diameter by compression in a mould and extruded. The resulting insecticidal pellet when strongly heated at one end, e.g. by the flame of a bunsen burner or by means of an ignition composition, supported its own decomposition, giving a yellow smoke without flame, containing 4:6 dinitro-o-cresol and D.D.T., which deposited a fine coating of the insecticidal material on surfaces contacted by it thus rendering them lethal to house flies for some time. The pellet left a non volatile residue amounting to about 10% of its weight.

Example 4.

The ingredients were the same as in Example 3, except that the gamma-isomer of hexa-chloro-cyclohexane (Gammexane) was substituted for D.D.T. An insecticidal pellet was prepared from the resulting mixture and its decomposition was initiated after the fashion described in Example 2. Its decomposition produced a yellow smoke without flame, containing 4:6 dinitro-o-cresol and Gammexane which deposited a fine coating of powder letha1 to house flies. The non volatile residue amounted to about 1% of the weight of the pellet.

Example 5.

A mixture of the composition:—

Guanidine nitrate		65%
Dinitro-resorcinol		15%
Gammexane		20%

was ground thoroughly until mixed in the form of a fine powder. A 20 gm. insecticide pellet of the composition was pressed as in the fashion described in Example 3 and its decomposition was initiated in similar fashion. A dense white smoke containing Gammexane was produced without any flame. The non volatile residue amounted to about 10% of the weight of the pellet.

Dated the 9th day of October, 1947.
E. A. BINGEN.
Solicitor for the Applicants.

COMPLETE SPECIFICATION

Improvements in and relating to Solid Gas-Generating Charges

We, IMPERIAL CHEMICAL INDUSTRES LIMITED, a British Company, of Imperial Chemical House, Millbank, London, S.W.1, do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement:—

[The smoke] deposited a fine coating of the insecticidal material on surfaces contacted by it thus rendering them lethal to house flies for some time.

The present invention relates to improvements in solid gas generating charges of the kind capable of propagating through themselves a self-sustaining exothermic non-detonating gas-evolving decomposition when a merely local portion of the charge is heated from room temperature to the temperature at which its active decomposition begins. Such gas-generating charges have found application for a variety of purposes including, for instance, the actuation of gas pressure operated mechanical devices, blasting operations, the dispersion of volatilisable pecticides [sic], insect repellants, rodenticides, propulsion of rockets and the expulsion of liquids from containers such as fire extinguishers.
It is known that guanidine nitrate undergoes an exothermic gas evolving decomposition when it is strongly heated, but under atmospheric pressure conditions the reaction does not sustain itself if a portion only of a quantity of the compound is heated from atmospheric temperature to the temperature at which decomposition begins, unless external heating is maintained. The decomposition leads to the production of steam, nitrogen, ammonia and oxides of carbon, but there is also formed a certain amount of a difficultly fusible yellow nitrogenous organic residue.
Only when the conditions are such that the prevailing gas pressure is sufficiently high, namely of the order of 70 atmospheres, will the reaction sustain itself throughout a mass of the guanidine nitrate once it has been locally initiated, and under such gas pressure conditions the products are almost wholly gases and vapours.
It has been disclosed in a Specification No. 21,529/1905 that certain amidic derivatives of carbonic acid, among which in the Provisional Specification. there was mentioned guanidine nitrate, may be introduced either individually or mixed together in some suitable proportion and insuitable [sic] quantity into the composition of all explosives having a base of nitrocellulose or certain other nitrated vegetable tissue substances of a similar kind, with or without nitroglycerine either before or after gelatinisation if such gelatinisation should be necessary; and that for the nitroglycerine there might be substituted wholly or in part nitrobenzene, nitrotoluene, or other similar compounds behaving as fixed solvents. This Provisional Specification further stated that the nitrate of dicyandiamidine, as well as guanidine nitrate, nitroguanidine or nitrosoguanidine might be used with success either individually or mixed together in different proportions in the composition of all explosives having a nitroglycerine base, as well as in the composition of all explosives having as a base oxidising salts. The explosives in which the amidic derivatives of carbonic acid were to be introduced included smokeless powder compositions and also powerful high explosive compositions and mining explosive compositions; for example, it was stated that there could be obtained very powerful explosives, though of very great insensibility to shocks and friction, by coupling the properties of these nitrogenous products with those of certain explosives already known and well characterised which were capable of disengaging in their combustion a great number of calories and in consequence could supply the heat necessary to develop the entire energy of the explosives in question, derived from dicyandiamide. There was in particular a disclosure of explosives of this kind made by mixing nitroguanidine with picric acid, either when this latter was in a state of fusion (to be more precise, during the act of fusing it) or by a simple intermixture of two substances in a crystalline state, or pulverised, or by crystallising them together from their solution in a common solvent. The mixture might be suitably compressed, either alone or after the addition of variable quantities or oxidising salts such as nitrate, chlorates, perchlorates, chromates, or permanganates. For picric acid there could be substituted its salts or various nitro-derivatives of the aromatic series.
It has been proposed to provide charges capable of decomposing with a high yield of permanent gases when locally heated by a non-detonating element at a lower pressure than guanidine nitrate, said mixtures comprising guanidine nitrate with a proportion of a metallic hypophosphite or ammonium hypophosphite whereby if desired charges capable of supporting their decompositions even at atmospheric pressure when locally heated may be obtained.

Such gas-generating charges have found application for a variety of purposes including […] insect repellants, rodenticides, propulsion of rockets and […] fire extinguishers.

Owing to the nature or amount of the residue the hypophosphites leave behind or other disadvantages attendant on their employment, these charges have only a limited applicability and it would be desirable to provide improved gas generating charges based on guanidine nitrate and capable of self-sustained decomposition under conditions of much lower gas pressure than guanidine nitrate alone.
It is also known that the pressure required to render possible the self-sustained decomposition of a charge based on guanidine nitrate may be progressively reduced by making up the guanidine nitrate into charges with progressively increasing amounts or colloided nitrocellulose as a binding agent, by mixing the guanidine nitrate with a solution of nitrocellulose in a volatile solvent, forming the resulting paste into the required shape and evaporating off the volatile solvent, but the use of a volatile solvent adds to the expense and necessitates a drying operation, while the applicability of this method is also somewhat limited.
According to the present invention gas generating charges capable of local heating of non-detonating decomposition comprise mixtures in compacted form whose constituents comprise guanidine nitrate and a polynitro- or polynitroso-derivative of phenol or of a hydroxy-, carboxy- or methyl substitution derivative of phenol, in which mixtures the guanidine nitrate is present in proportion preponderating over the total proportion of the other constituent or constituents and the said polynitro- or polynitroso-derivative is present in sufficient proportion to render the compact mixture capable of sustaining its own decomposition under atmospheric pressure conditions once this has been initiated by merely local heating.
As the polynitro-derivative it is preferred to employ 2:4 dinitro-resorcinol, but 2:4:6 trinitro-resorcinol; 4:6 dinitro-ortho-cresol; 3:5 dinitro-catechol, 2:6 dinitro-para-cresol, or 3: 5 dinitro-salicyclic acid may also be used. As polynitrosophenol derivative there may be employed 2:4 dinitroso-resorcinol. In the absence of diluents or heat absorbing ingredients the proportion of the poly-nitro- or polynitroso-derivative required to render the compact composition capable or self-sustained decomposition when locally heated under atmospheric pressure conditions may vary from 8 to 20 per cent of the weight of the guanidine nitrate according to the particular compound used.

[I]t would be desirable to provide improved gas generating charges based on guanidine nitrate and capable of self-sustained decomposition under conditions of much lower gas pressure than guanidine nitrate alone

The gas generating charges obtained in accordance with the invention are suitable for a variety of purposes and are free from many of the disadvantages attendant on the use of hypophosphites or gelatinised nitrocellulose as sensitisers, e.g. they can be manufactured and stored more safely than compositions containing hypophosphites and yield less obnoxious gases on recomposition. The compacted mixtures can be formed in a greater variety of sizes and more quickly and conveniently than those containing nitrocellulose. They sustain their non-detonating decomposition with a high yield of hot gases which do not corrode ferrous metal equipment.
If desired the compact mixtures comprised in the charges according to the invention may include an aliphatic carboxylic acid selected from the group consisting of tartaric, maleic, citric and fumaric acids. The presence of an aliphatic carboxylic acid permits less of the said polynitro-derivative or polynitroso-derivative to be present than would otherwise be necessary. It is an advantage of the invention that the compositions may be made by simple admixture of the ingredients, and that when the said compacted mixture is required to be of such a form that it will react only on its exposed external surface it may be made by compressing the mixture into a mould of the desired shape. Moreover, if it is required to protect a portion of the surface of the compacted mixture from the hot gases evolved by means of an adherent covering of heat-insulating material, this may if desired be done in the course of the pressing operation instead of applying protective material to the surface of the mixture after it has been shaped.
When charges consisting of the aforesaid compacted mixtures are consumed under atmospheric pressure conditions or at comparatively low superatmospheric working pressures e.g. up to about 10 atmospheres, their decomposition into gaseous products is not quite complete, and they leave a certain amount, (usually 15 to 20%), of the difficu1tly fusible nitrogenous organic residue already referred to; and at these pressures the gases contain appreciable quantities of vaporised condensable organic materials, the presence of which may be undesirable in certain applications of the charges e.g. if they are to be used in driving engines or operating other mechanical devices where these organic vapours can condense and cause fouling of pipes or moving parts.
We have found however that the inclusion of a small proportion of vanadium pentoxide amounting for example to 0.2 to 1 per cent of the weight of the guanidine nitrate has the effect of completing the decomposition of the guanidine nitrate thus obviating the formation of the aforesaid yellow difficultly fusible organic residue and, correspondingly increasing the yield of hot gases at working pressures at which this residue would otherwise be formed; and we preferably include in the charge such a proportion of vanadium pentoxide or: the chemically equivalent proportion of a vanadate e.g. ammonium vanadate.

The gas generating charges obtained in accordance with the invention […] sustain their non-detonating decomposition with a high yield of hot gases which do not corrode ferrous metal equipment.

It has also been found that certain compounds of molybdenum e.g. molybdic acid, may be used in place of the vanadium compounds. We have further found that the condensable vaporised organic compounds that would otherwise be formed at pressures near atmospheric may be destroyed as a result of an exothermic reaction further increasing the hot gas yield, by causing the mixture of gases and vapours, before cooling takes place, to pass over suitable heat resisting catalytic solid surfaces such as those of iron, steel or platinum wire gauze or asbestos, or including in the composition of the compacted mixture a small percentage of asbestos fibre or other heat resisting material characterised by a large surface and amounting to not less than about 0.25% but not exceeding 1 per cent of the weight of the compacted mixture. The large surface material also steadies the self-supporting characteristics of the reaction and holds together the ash of the compacted mixture. It may be desirable to include a small percentage of potassium nitrate in the compacted mixture, amounting, for instance, to 0.25 to 1%, since the potassium nitrate assists the reaction between the gases and vapours on the solid catalytic surface. The use of the potassium nitrate is especially desirable if the charge is in an unusually cold condition before it is locally ignited, or in an environment such that the gases and vapours are at a lower temperature than that at which they would normally be generated.

It may be desirable to include a small percentage of potassium nitrate in the compacted mixture, […] if the charge is in an unusually cold condition before it is locally ignited

Charges made in accordance with the invention may he used for instance for actuating gas pressure operated mechanical devices, e.g. for driving engines, or for operating pneumatic tools, for operating fire extinguishers, for propulsion of rockets and other gas escape reaction propelled devices, for dispersing insecticidal or the like substances, for making coloured smokes, or for safety blasting operations by means of blasting assemblies in which the charge is caused to undergo decomposition in a pressure resisting container adapted to vent the gases once a predetermined pressure has been built up within the container. It will be understood that according to the purpose for which the charge is required it may be in granular or other compact form of any required shape, and may or may not include ingredients for reducing or raising the temperature of the gases it generates. The hereinafter mentioned thermal1y volatilisable effect materials are examples of ingredients which reduce the temperature of the said gases and by way of example ammonium perchlorate and ammonium nitrate are reagents which raise the temperature of the said gases.
Charges in accordance with the invention may include thermally volatilisable effect materials, which may be for instance, insect repellants; insecticides, fungicides, bactericides and other pesticides; smoke producing compounds or coloured dyestuffs. In this case the charge will usually be required to decompose under atmospheric pressure conditions; and if the effect material is an organic compound it will be understood that if the charge is to include asbestos fibre or other heat resisting material of large surface characteristics the composition of the charge must be such that the gases and vapours will not undergo to any extent a reaction on the surface of said heat resisting material that would destroy the volatilisable compound in the gas stream. The volatilisation or the organic compound has a cooling action so that if sufficient of this compound is used the temperature will be too low for any such undesired surface reaction to take place. 4:6 Dinitro-ortho-cresol is an example of a polynitro-phenol derivative that has itself marked insecticidal arachnicidal properties.
The invention is further illustrated by the following examples in which the parts are parts by weight.

Example 1.

A mixture of the composition:—

Guanidine nitrate		88.75%
2:4 dinitro-resorcinol		10.0%
Asbestos fibre		0.5%
Vanadium pentoxide		0.5%
Potassium nitrate		0.25%

is subjected to ball milling until the composition is well mixed and pulverised. 3 lbs. of the mixture is then loaded in four equal increments into a 3" diameter open ended steel tube lined with compressed asbestos fibre sheeting, each increment being pressed for 1 minute at 7000 lb. per square inch, the compressed composition occupying all but one inch at each end of the length of the tube. A hole of 1 inch diameter is then drilled axially through the length of the compressed composition. Four or five circles of iron wire gauze each of 3". diameter and or a mesh ranging from 10 to 50 to the inch (BSS) are fitted into one end of the tube and an electrical ignition system including a rod of cordite weighing 20 grams is arranged at the other end of the tube with the cordite extending into the drilled channel.
The tube containing the composition is used to operate a motor of rotary blower design at a progressively increasing speed at a constant working pressure of about 120 lbs. per square inch. The charge leaves an incombustible skeleton amounting to less than 1.25%. of the weight thereof, without depositing any condensed organic material in the apparatus.

Example 2.

A mixture of the composition:—

Guanidine nitrate		88.7%
2:4 dinitro-resorcinol		9.8%
Potassium nitrate		0.25%
Vanadium pentoxide		0.5%
Mineral oil		0.5%
Asbestos fibre		0.25%

is subjected to ball mixing until the ingredients are well mixed into the form of a fine powder. 20 gms. of the mixture are pressed in a tubular mould 0.95 inches in diameter lined with asbestos paper under a pressure sufficient to give a well consolidated pellet. The pellet with its asbestos sheath is extruded from the mould and fitted into a cylindrical container of approximately 1" diameter closed at one end and fitted with a screw-on cap at the other end carrying a jet 0.055 inch in diameter. The ignition system for the pellet at the open end consists of a sliver of cordite held on the surface or the composition by means of a tightly fitting circle of 60 mesh BSS stainless steel wire cloth with a length of thin black-powder fuse running from the cordite to the exterior through the jet in the cap of the container.

This miniature jet motor forms the propulsion unit of a model racing car. The ignition is brought about by igniting the fuse with a match which ignites the cordite, which in turn locally heats the composition of the charge to the temperature at which the evolution of the gases became active, the decomposition then sustaining itself through the charge. In this manner a thrust of 3 oz. weight lasting for 20 seconds is exerted on the model racing car. The ash is a coherent skeleton of the pellet and amounts to a about 1% of its weight.

Example 3.

A mixture of the composition:—

Guanidine nitrate		67%
4:6 dinitro-o-cresol		18.0%
Alpha - alpha - bis - (parachloro-
phenyl) - beta - beta - beta -
trichloroethane (D.D.T.)		15%

In this manner a thrust of 3 oz. weight lasting for 20 seconds is exerted on the model racing car.

is prepared by grinding the ingredients together until they are well mixed in the form of a fine powder. 20 gms of the mixture are consolidated into the form of a pellet 1 inch in diameter by compression in a mould and extruded. The resulting insecticidal pellet when strongly heated at one end, e.g. by the flame of a bunsen burner or by means of an ignition composition, supports its own decomposition, giving a yellow smoke without flame, containing 4:6 dinitro-o-cresol and D.D.T., which deposits a fine coating of the insecticidal material on surfaces contacted by it thus rendering them lethal to house flies for some time. The pellet leaves a non volatile residue amounting to about 10% of its weight.

Example 4.

The ingredients are the same as in Example 3, except that the gamma-isomer of hexa-chloro-cyclohexane (Gammexane) is substituted for D.D.T. An insecticidal pellet is prepared from the resulting mixture and its decomposition is initiated after the fashion described in Example 2. Its decomposition produces a yellow smoke without flame, containing 4:6 dinitro-o-cresol and Gammexane which deposits a fine coating of powder letha1 to house flies. The non volatile residue amounts to about 10% of the weight of the pellet.

Example 5.

A mixture of the composition:—

Guanidine nitrate		65%
Dinitro-resorcinol		15%
Gamma-isomer of hexachloro-
cyclohexane		20%

is ground thoroughly until mixed in the form of a fine powder. A 20 gm. insecticide pellet of the composition is pressed as described in example 3 and its decomposition is initiated in similar fashion. A dense white smoke containing the said gamma-isomer is produced without any flame. The non-volatile residue amounts to about 10% of the weight of the pellet.
In Specification No. 620,600 there are claimed inter alia fumigating compositions, or cartridges containing or compact pellets formed from these, consisting of a mixture comprising a thermally vaporisable pesticidal or insect-repellent compound, the nitrate and/or nitro-derivative of guanidine and a sufficient quantity of the sensitiser of the thermal decomposition of the said guanidine-derivative or derivatives to permit a self-sustained flameless thermal decomposition of the said guanidine derivative or derivatives to take place in the presence of the pesticidal or insect-repellent compound, which may if desired include alpha-alpha-bis (parachlorophenyl) beta - beta - beta-trichloroethane or hexachlorocyclohexane.
We make no claim herein to anything claimed in Specification 620,600.
Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is:—
1. Gas generating charges capable on local heating of non-detonating decomposition comprising mixtures in compacted form whose constituents comprise guanidine nitrate and a poly-nitro- or poly-nitroso-derivative of phenol- or of a hydroxy-, carboxy- or methyl substitution derivative of phenol, in which mixtures the guanidine nitrate is present in proportion preponderating over the total proportion of the other constituent or constituents and the said polynitro- or poly-nitroso-derivative is present in sufficient proportion to render the compact mixture capable of sustaining its own decomposition once it has been initiated by merely local heating under atmospheric pressure conditions.
2. Gas generating charges as claimed in claim 1 wherein the dinitro-derivative is 2:4 dinitro-resorcinol.
3. Gas generating charges as claimed in claim-l wherein the polynitroso-derivative is 2:4 dinitroso-resorcinol.
4. Gas generating charges as claimed in claim 1 wherein the polynitro-derivative is 2:4:6 trinitro-resorcinol, 4:6 dinitro-ortho-cresol, 3:5 dinitro-catechol, 2:6 dinitro-para-cresol. or 3:5 dinitro-salicylic acid.
5. Gas generating charges as claimed in claim 1 or claim 2 wherein the mixture is substantially free from diluents or heat absorbing ingredients and contains 2:4 dinitro-resorcinol in a proportion amounting to not less than 8 per cent of the weight of the guanidine nitrate.
6. Gas generating charges as claimed in any of the preceding claims wherein the compacted mixture includes an aliphatic carboxylic acid selected from the group consisting ot tartaric, maleic, citric and fumaric acid.
7. Gas generating charges as claimed in any of the preceding claims wherein the compacted mixture includes a small proportion of vanadium pentoxide or molybdic acid.
8. Gas generating charges as claimed in claim 7 wherein the amount of vanadium pentoxide included is 0.2 to 1 per cent of the weight of the guanidine nitrate.
9. Gas generating charges as claimed in any of claims 1 to 6 wherein the compacted mixture includes a small proportion of a vanadate.
10. Gas generating charges as claimed in claim 9 wherein the vanadate is ammonium vanadate.
11. Gas generating charges as claimed in any of the preceding claims which include a heat-resisting catalytic solid material positioned so that the gases and vapours pass over it.
12. Gas generating charges as claimed in any of the preceding claims wherein the compacted mixture includes a small percentage of heat-resisting material having a large surface area and amounting to not less than about 0.20 per cent but not exceeding 1 per cent of the weight of the compacted mixture.
13. Gas generating charges as claimed in claim 12 wherein the heat-resisting material is asbestos fibre.
14. Gas generating charges as claimed in any of the preceding claims wherein the compact mixture includes a small percentage of potassium nitrate.
15. Gas generating charges as claimed in claim 12 wherein the percentage of potassium nitrate is 0.25 to 1 per cent. of the weight of the compacted mixture.
16. Gas generating charges as claimed in any of the preceding claims which include constituents for reducing or raising the temperature of the gases generated.
17. Gas generating charges as claimed in any of the preceding claims which include thermally volatilisable effect materials.
18. Gas generating charges as claimed in claim 17 wherein the thermally volatilisable effect materials are insect repellants, insecticides, fungicides, bactericides and other pesticides.
19. Gas generating charges as claimed in any of the preceding claims in granular or compact form of any required shape.
20. Gas generating charges when in compact form as claimed in claim 19 wherein a portion of the surface of the compacted mixture is provided with an adherent covering of heat-insulating material.
21. Gas generating charges substantially as described with reference to the foregoing examples.

Dated the 11th day of August. 1948.
E. A. BINGEN,
Solicitor for the Applicants.

Leamington Spa: Printed for His Majesty's Stationery Office, by the Courier Press.—1950.
Published at The Patent Office, 25, Southampton Buildings. London, W.C.2, from which copies, price 2s. Od. each (inland) 2s. 1d. (abroad) may be obtained.

[The smoke] deposited a fine coating of the insecticidal material on surfaces contacted by it thus rendering them lethal to house flies for some time.


	Acknowledgements - Original patents located, copied and compiled by Gerhard Everwyn; contributed by Terry Kidd

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