US2470082A - Gas-producing charges suitable for the generation of gas pressure for the operation of mechanical devices and for blasting operations - Google Patents

Description

Patented May 10, 1949 UITED FICE GAS-PRODUCING CHARGES SUI'EAJBLE FOR THE GENERATEUN F GAS PRESSURE FUR THE OPERATKQN QF MECHANKCAL DE- VICES AND FOR ELASTKNG OPERATEONS- No Drawing. Application September 7, 1945, Se-

rial No. 615,105. In

7 Claims.

The present invention relates to new or improved gas-producing charges of the kind capable of propagating a self-sustained gas-producing non-detonating decomposition through themselves, when they are locally heated by a limited non-detonating igniting element, that is to say, one capable of heating a small portion of the Charge to a high temperature and insufficient of itself to efiect any substantial general rise in the temperature of the charge.

Depending on the rate at which the gas-producing decomposition is propagated through the charge under increasing pressure conditions, the nature of the gases produced, the amount and quality of any solid products of the reaction and the presence or absence of flame, such charges may find application for a variety of purposes, including, for instance, the generation of gas pressure for actuating pneumatically operated mechanical devices and blasting operations when a slow heaving action is required, as in the winning of lump coal.

It is known that Various compositions comprising ammonium nitrate and oxidisable ingredients are capable of undergoing a progressive selfsustaining gas-producing decomposition yielding a high proportion of permanent gases suitable for the actuation of pneumatically operated mechanical devices when locally heated at temperatures substantially above atmospheric, and it has been proposed to sensitise the decomposition of certain charges containing ammonium nitrate by the inclusion of a suitable chromate compound in the composition so that the decomposition can be initiated at ordinary atmospheric pressure by local heating of a portion of the charge with a limited non-detonating igniting element. It has also been proposed to provide composite charges for the actuation of pneumatically operated mechanical devices in which a succession of charges which may comprise ammonium nitrate and oxidisable ingredients of organic character, or guanidine nitrate, are sensitised so that they can likewise be initiated at lower pressures than would otherwise have been the case, by making them into a paste with a solution of nitrocellulose in a volatile solvent and evaporating the solvent so as to form compact charge units. Ammonium nitrate undergoes volume changes at its transition slightly above atmospheric; and the hygroscopic and deliquescent properties of ammonium nitrate Great Britain September may necessitate special measures for waterproofing the charges.

It is known that nitroguanidine can be decomposed when strongly heated, givin a good 5 yield of permanent gases that would be suitable for the aforesaid purposes leaving a certain amount of solid residue. It is also known that nitrodicyandiamidine and dicyandiamidine nitrate are capable of partial decomposition when strongly heated. lhese compounds, like guanidine nitrate, are free from the disadvantage of undergoing volume changes at temperatures near to atmospheric temperature, and they are nondeliquescent sub-stances. It has been proposed to form composite charges for the slow generation of gas pressure suitable for the actuation of mechanical devices in which at least one of the charge elements incapable of supporting its own combustion when ignited locally at atmospheric pressure by a limited non-deton ating igniting element, but capable of supporting in excess of atmospheric, comprises compacted nitroguanidine, optionally in admixture with the binding agent. In this connection, it may be stated that although the presence of gelatinised nitrocellulose as binding agent for nitroguanidine or for guanidine nitrate reduces the minimum pressure at which a charge element comprising the compound can support its combustion the employment of a nitrocellulose solution makes it difficult to prepare compact forms of charge that will maintain their burning characteristics well on storage if the form is required to have a smallest dimension of any substantial size, owing to the diiiiculty of effecting complete evaporation of the volatile solvent,

We have now found that new or improved charges suitable for the aforesaid purposes capale of decomposing with the evolution of a high yield of permanent gases suitable for the aforesaid purposes when they are locally heated by a non-detonating element at lower pressures than would otherwise be the case are obtained from mixtures comprising nitroguanidine, guanidine 4.5 nitrate, nitrcdicyandiamidine or dicyandiamidlne nitrate with a proportion of a metallic hypophosphite or ammonium hypophosphite, whereby if desired charges capable of supporting their decomposition even at atmospheric pressure when locally heated as aforesaid may he obtained.

According to the present invention therefore gas producing charges of the kind herein defined comprise a mixture of any one or more of the compounds nitrcguanidine, guanidine iiitrate, nitrodicyandiamidine' or dicyandiamidine 3 nitrate and a metalilc hypophosphite or ammonium hypophosphite.

Charges made in accordance with the invention decompose smoothly when they are ignited, and they do not undergo volume changes at temperatures at which they are likely to be exposed on storage. It is also possible by means of the invention to obtain charges that decompose without flame when they are locally heated and which are accordingly suitable for blasting in fiery or dusty mines. For blasting purposes it is frequently advisable to confine the mixture in order to enable the pressure to be built up satisfactorily, and for this purpose a blasting assembly comprising a gas producing charge confined in a pressure resisting vessel having the closure adapted to yield at a predetermined pressure may conveniently be employed.

In putting the invention into efiect, the nitrate or nitro-cornpound used and the hypophosphite employed advantageously in a fine state of division may be mixed together and if desired compasted into the desired form by pressure. As hypophosphites theremay be employed, for instance calcium hypophosphites, sodium hypophosphite or ammonium hypophosphite. The proportion of the hypophosphite to the organic nitrate or nitrocompound present in the mixture may vary considerably. The minimum proportion of the hypophosphite required to render the mixture capable of sustaining its own decomposition when locally heated at atmospheric pressure in particular varies according to the particular compounds used, and it is often sufficient that the minimum pressure at which the charge should be capable of supporting its combustion should be slightly greater than atmospheric, since it is customary to employ in cartridges for the actuation of mechanical devices an igniting system that is itself capable of generating a gas pressure of few atmospheres; and it is generally advisable to employ only so much of the hypophosphite as is necessary to ensure that the decomposition will proceed satisfactorily. Amounts of hypophosphite of about 5-3 per cent of the weight of the nitrate or nitrocompound are usually satisfactory. If desired a minor proportion of an oxidising ingredient for instance an alkali metal nitrate or ammonium nitrate may be included in the composition; and it is frequently desirable in some cases to include in the composition a small quantity of binding or bonding agent.

The invention is further illustrated in the following examples:

Ezvample 1 Guanidine nitrate, 90% ammonium hypophosphite, 107

Guanidine nitrate, 80% ammonium hypophosphite, 20):

Guanidine nitrate, 66% ammonium hypophosphite, 34%

The combustion of these charges takes place without flame at successively increasing speeds. The third composition is the fastest.

' Example 2 The composition of the charge which are prepared as in Example 1 are as follows:

Dicyandiamidine nitrate, 80% ammonium hypophosphito, 20% Dicyandiamidine nitrate, 66% ammonium hypophosphite, 34%

The combustion of these charges takes place without flame at slower speeds than the corre-' sponding charges in Example 1.

Example 3 The composition of the charges which are prepared as in Example 1 are as follows:

Per cent Guanidine nitrate Calcium hypophosphite 20 The combustion of this charge takes place without flame at a slower speed than that of the charge of corresponding composition in Example 1 or Example 2.

Example 4 The composition of the charge, which isformed I as described in Example 1 is as follows:

Per cent Nitrodicyandiamidine 69 Ammonium nitrate 27 Ammonium hypophosphite 3% Example 5 The ingredients are milled with an edgerunner mill to a fine state of division, compressed into block form, broken up and screened, the granules passing a 12 mesh but retained on a This charge is loaded to the extent of 50 gms. into a steel tube of 1%" internal diameter, 4 ft. long already provided at the closed end with a 1 ft. 10 in. thickness of sand, and tamped at the other end with sand and a wooden plug through which pass the leads to a small gasless igniter. When the current is passed through the igniter an explosion takes place without any apparent delay, and the steel tube is burst open. This explosion is unaccompanied by flame, and fails to ignite a 9% methane/air mixture. The screened composition may be employed as a. non-detonating blasting powder, advantageously in a pressure resisting steel tube having a closure yielding at a pressure of the order of 12 tons/sq. in. such as is used in Hydrox blasting. The nondetonating decomposition may be brought about by means of a gasless igniter as aforesaid or by means of an electric detonator.

I claim:

1. Gas producing charges capable of selfsustaining decomposition comprising a mixture of at least one of the compounds selected from the group consisting of nitroguanidine, guanidine nitrate, nitrodicyandiamidine, and dicyandiamine nitrate with a hypophosphite selected from the group consisting of sodium hypophosphite, calcium hypophosphite and ammonium hypophosphites, wherein the hypophosphite is from 535% of the total Weight of the charge.

2. Gas producing charges as claimed in claim 1, wherein the hypophosphite is calcium hypophosphite.

3. Gas producing charges as claimed in claim 1, wherein the hypophosphite is ammonium hypophosphite.

4. Gas producing charges capable of selfsustaining decomposition comprising a. mixture of at least one of the compounds selected from the group consisting of nitroguanidine, guanidine nitrate, nitrodicyandiamidine and dicyandiamidine nitrate, with a hypophosphite selected from the group consisting of sodium hypophosphite, calcium hypophosphite and ammonium hypophosphite, wherein the hypophosphite is from 5% to 35% of the charge by weight, and a small quantity of an oxidizing ingredient.

5. The gas producing charge as claimed in claim 4, wherein the oxidizing ingredient is potassium nitrate.

6. The gas producing charge as claimed in claim 4, wherein the oxidizing ingredient is ammonium nitrate.

7. Gas producing charges as claimed in claim 1, wherein the mixture is pressure compacted.

ALEXANDER THOMSON TYRE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 875,913 Holmes Jan. 7, 1908 2,165,263 Holm July 11, 1939 FOREIGN PATENTS Number Country Date 477,956 Great Britain July 6, 1936 479,773 Great Britain Feb. 10, 1938