GB2132999A

GB2132999A - Producing an emulsion explosive

Info

Publication number: GB2132999A
Application number: GB08329301A
Authority: GB
Inventors: Jeremy Guy Breakwell Smith
Original assignee: AECI Ltd
Current assignee: AECI Ltd
Priority date: 1982-11-03
Filing date: 1983-11-02
Publication date: 1984-07-18
Also published as: GB2132999B; AU563042B2; GB8329301D0; CA1227038A; AU2093383A; NZ206131A; ZW23383A1

Abstract

A method of making an explosive in the form of an emulsion comprising a discontinuous phase which includes an oxidising salt, and a continuous phase which includes a fuel and which is immiscible with the discontinuous phase, the method comprising dispersing an aqueous solution of an oxidising salt, such as ammonium nitrate and/or sodium nitrate, containing an amine, such as ethylene diamine or diethylene triamine, dispersed therein into a continuous phase which includes a fuel, such as a paraffinic hydrocarbon oil, and which has a long chain carboxylic acid, such as oleic acid, and/or the halide of a long chain carboxylic acid, such as oleic acid chloride, dispersed therein, thereby to form an emulsion, the amine reacting with the acid and/or acid halide to form one or more reaction products which act to stabilize the emulsion.

Description

SPECIFICATION A method of making an explosive in the form of an emulsion This invention relates to an explosive. In particular the invention relates to an explosive of the emulsion type in which an oxidizing salt-containing component forms the discontinuous phase in an emulsion wherein the continuous phase comprises a fuel component which is immiscible with the discontinuous phase.

Such explosives, where the oxidizing salt-containing component contains water and is in the form of an aqueous solution are known as "water-in-fuel" emulsions, and when the oxidizing salt component includes no water they can be regarded as "melt-in-fuei" emulsions.

According to the invention there is provided a method of making an explosive in the form of an emulsion comprising a discontinuous phase which includes an oxidizing salt and a continuous phase which includes a fuel and which is immiscible with the discontinuous phase, the method comprising dispersing an aqueous solution or melt of an oxidizing salt containing an amine dispersed therein into a continuous phase which includes a fuel and which has a long chain carboxylic acid and/or the halide of a long chain carboxylic acid dispersed therein, thereby to form an emulsion, the amine reacting with the acid and/or acid halide to form one or more reaction products which act to stabilize the emulsion.

The method may include dissolving the amine in the discontinuous phase, and the method may include dissolving the carboxylic acid and/or the acid halide in the continuous phase.

By "long chain" carboxylic acid" is meant a carboxylic acid having a molecular weight of at least about 280. The carbon chain may be optionally branched but preferably unbranched and ideally may be in the formula CH3(CH2)nCOOH where n is from 1 6 to 20. For example, the carboxylic acid may be oleic acid.

The amine may have several amine groups, being for example a diamine or a triamine.

Suitable diamines may be of the formula NH2(CH2)XNH2 where x is from 2 to 5, eg ethylene diamine, and triamines of similar molecular weights ie from 70 to 120, such as diethylene triamine, may also be suitable.

Without being bound by theory, the applicant believes that, at the interfaces between the droplets of the dispersed phase in the emulsion and the continuous phase, the amine reacts with the acid or acid halide, which is conveniently a chloride, according to the following reactions (shown for oleic acid and oleic acid chloride, with a diamine): Acid Amine Product C17H33COOH + NH2(CH2 )xNH2 C17H33CONH(CH2)xNH2 + H20 Acid Chloride Amine Product C17H33COC + NH(CH2 )xN H2 Ci7H33CONH(CH2)xNH2 + HCI It is believed that such reaction products act as surfactants with emulsifying and stabilizing properties, to provide the emulsion explosives produced with enhanced stability.These reaction products are formed in situ, at the droplet surfaces where the surfactant properties are required.

Starting materials should be used, typically, in such proportions that the reaction products of the acid and/or halide thereof and the amine constitute about 1 ,5 to 10% m/m, preferably 2 to 5% m/m of the finai emulsion explosive.

The emulsion is formed by dispersing the discontinuous phase in the continuous phase when they are both in liquid form, but the expression "emulsion" is intended to be construed as covering also the emulsions at temperatures below that at which they were formed, so that the discontinuous phase may be a solid.

The invention extends to an explosive in the form of an emulsion when prepared according to the method of the invention.

The oxidising salt of the emulsion may comprise a member selected from the group consisting of: alkali metal nitrates, alkali metal perchlorates, alkaline earth metal nitrates, alkaline earth metal perchlorates, ammonium nitrate, ammonium perchlorate, and mixtures of two of more thereof.

The oxidising salt may be present as an aqueous solution.

Instead, the discontinuous phase may comprise ammonium nitrate and one or more compounds which, together with the ammonium nitrate, form a melt which has a melting point which is lower than that of the ammonium nitrate, the compounds being capable of acting as oxygen releasing salts or fuels.

The fuel may form from about 2 to 25% by mass of the emulsion, preferably being in the region of about 3 to 12% by mass thereof.

The fuel may comprise an emulsifier in addition to reaction products of the said amine and acid and/or acid halide.

The additional emulsifier may comprise a member selected from the group consisting of sorbitan sesquioleate, sorbitan monooleate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearaate, the mono- and diglycerides of fat-forming fatty acids, soya bean lecithin, derivatives of lanolin, alkyl benzene sulphonates, oleyl acid phosphate, laurylamine acetate, decaglycerol decaoleate, decaglycerol decastearate, polymeric emulsifiers containing polyethylene glycol backbones with fatty acid side chains, and suitable mixtures of two or more thereof.

The fuel will be immiscibie with and insoluble in water, and is preferably a non-self-explosive organic fuel, being for example selected from the group consisting of hydrocarbons, halogenated hydrocarbons and mixtures thereof. Thus the fuel may comprise a member selected from the group consisting of mineral oils, fuel oils, lubricating oils, liquid paraffin, microcrystalline waxes, paraffin waxes, xylene, petrolatum, toluene, dinitrotoluene and mixtures of two or more thereof.

The emulsifers act as stabilizers to promote the formation of the emulsion and to combat coalescing and/or crystallization of the discontinuous phase.

In general when the discontinuous phase contains water, this water should be kept at a minimum consistent with forming a satisfactory emulsion and the prevention of wasted energy arising from steam production upon detonation.

The density of the emulsion will be such as to form a suitable explosives composition, and preferably may be between 1,30 g/ml and 1,45 g/ml at 25"C.

The explosive may thus include micro-balloons to provide the emulsion with a desired density eg 1,15-1,20 g/ml at 25"C. The emulsion may comprise up to 3% by weight of the microballoons, which are preferably not of glass but of a polymeric material, and preferably 1 to 3%, and they can also act to sensitize the explosive. Gassing may instead be used for density control and sensitizing, and it should be noted that glass micro-balloons are not preferred because their presence has been found to reduce the emulsion stability.

The following emulsion was prepared and used as a control emulsion: The formulation of this control emulsion was as follows: % by mass Ammonium nitrate 68,3 Sodium nitrate 13,6 Water 11,5 Span 50 2,6 P95 oil 4,0 The emulsion was prepared in a Hobart mixer having a steam-jacketed bowl, with a wire whip. The inorganic salt solution (oxidizer) was heated up to a temperature of 85"C.

The oil phase consisting of the P95 paraffinic oil and the Span 80, was heated up to 85"C in a steam-jacketed bowl. The oxidiser solution was subsequently added with the wire whip at a speed of 285 rpm. The resultant emulsion was stirred for another two minutes at the same speed, which was then increased to 591 rpm for a period of ten minutes. After this the product had a petroleumjelly like consistency and a density of 1,45 g/ml. Sufficient polymeric microballoons were added at 65"C to bring the density down to 1,15 to 1,20 g/ml. The emulsion detonated with 0,399 of pentaerythritol tetranitrate (hereafter referred to as PETN) at 25"C in 25 mm diameter, and was found to have a shelf life at ambient temperatures (during which it could be detonated in this fashion) of 4-6 weeks.

The invention will now be described, with reference to the following non-limiting examples: EXAMPLE 1 The procedure for the control test was repeated except that the Span 80 was reduced to 1,3% m/m and oleic acid and ethylene diamine were added (in a mass ratio of 1:5) to the oxidizer phase and fuel phase starting materials respectively, to make up to 100%. The emulsion explosive obtained was similar to the control but had an improved shelf life of 5-6 months.

EXAMPLE 2 Example 1 was repeated, using oleic acid chloride instead of oleic acid. A similar explosive with a similar improved shelf life of 5-6 months was obtained.

EXAMPLE 3 Example 1 was repeated except that diethylene triamine was used instead of ethylene diamine, and the ratio of oleic acid to the amine was 1:3. Again similar results with a shelf life of 5-6 weeks at ambient temperatures were obtained.

EXAMPLE 4 Example 3 was repeated except that the acid was replaced by the acid chloride, and similar results with a similar extended shelf life of 5-6 months were obtained.

EXAMPLE 5 The procedure for the control was repeated except that all the Span 80 was replaced by a 1:5 m/m ratio of oleic acid and ethylene diamine added to the oxidizer and fuel phases respectively.

A similar emulsion was again obtained, which however had an extended shelf life of 3 months at ambient temperatures.

EXAMPLE 6 Example 5 was repeated with oleic acid chloride instead of oleic acid and a similar emulsion with a similar shelf life of 3 months was obtained.

EXAMPLE 7 Example 5 was repeated, with the ethylene diamine replaced by diethylene triamine, and the mass ratio between the oleic acid and diethylene diamine set at 1:3. A similar emulsion with a similar shelf life of 3 months was again obtained.

EXAMPLE 8 Example 7 was repeated with the oleic acid replaced by oleic acid chloride. A similar emulsion with a similar shelf life of 3 months was again obtained.

In the control and Examples, the P95 oil was a paraffinic hydrocarbon oil (fuel) available from B P Southern Africa (Proprietary) Limited; the Span 80 was sorbitan monooleate emulsifier available from Atlas Oil and Chemical Company; and the polymeric microballoons were formed from a copolymer of polyvinylidene chloride and acrylonitrile, made by Kema-Nord, Sweden and available in South Africa from Alfred Rieson (Proprietary) Limited as "Expancel 642".

An advantage of the invention is that it provides an inexpensive and easily used emulsification system whereby, using easily available and inexpensive starting materials, a surfactant with emulsifying and stabilizing properties can be provided in situ at the droplet surfaces, during formation of the emulsion. Mixing can be carried out at the usual temperatures and pressures employed in the art, and no special equipment and process conditions, such as elevated pressures, are needed. The invention by itself provides enhanced shelf life when compared with Span 80, a standard but expensive emulsifier used for this purpose, and even better results are obtained when the invention is used together with a reduced proportion of Span 80.

Although the invention has been described above with reference to certain specific starting materials in the Examples, it will be appreciated that there are a large number of carboxylic acids, carboxylic acid halides, and amines, which can potentially be used for the purpose of the present invention and routine experimentation will be required to determine reagents and proportions thereof for particular emulsion explosive formulations.

Claims

1. A method of making an explosive in the form of an emulsion comprising a discontinuous phase which includes an oxidising salt and a continuous phase which includes a fuel and which is immiscible with the discontinuous phase, the method comprising dispersing an aqueous solution or melt of an oxidizing salt containing an amine dispersed therein into a continuous phase which includes a fuel and which has a long chain carboxylic acid and/or the halide of a long chain carboxylic acid dispersed therein, thereby to form an emulsion, the amine reacting with the acid and/or acid halide to form one or more reaction products which act to stabilize the emulsion.

2. A method as claimed in Claim 1 which includes dissolving the amine in the discontinuous phase.

3. A method as Claimed in Claim 1 or Claim 2 which includes dissolving the carboxylic acid and/or the acid halide in the continuous phase.

4. A method as claimed in any one of the preceding claims wherein the carboxylic acid is unbranched.

5. A method as claimed in any one of the preceding claims wherein the carboxylic acid is of the formula CH3(CH2)nCOOH and n is from 1 6 to 20.

6. A method as claimed in any one of the preceding claims wherein the acid is oleic acid.

7. A method as claimed in any one of the preceding claims wherein the amine is a diamine.

8. A method as claimed in Claim 7 wherein the diamine is of the formula NH2(CH2)XNH2 and x is from 2 to 5.

9. A method as claimed in any one of Claims 1 to 6 wherein the amine is a triamine.

10. A method as claimed in any one of Claims 7 to 9 wherein the amine has a molecular weight of from 70 to 1 20.

11. A method as claimed in any one of the preceding claims which includes using starting materials in such proportions that the reaction products of the acid and/or halide thereof and the amine constitute 1,5% to 10% m/m of the final emulsion explosive.

1 2. A method of making an explosive substantially as herein described and exemplified.

1 3. An explosive in the form of an emulsion when prepared according to the method as claimed in any one of Claims 1 to 1 2.

1 4. An explosive as claimed in Claim 1 3 wherein the oxidising salt comprises a member selected from the group consisting of alkali metal nitrates, 'alkali metal perchlorates, alkaline earth metal nitrates, alkaline earth metal perchlorates, ammonium nitrates, ammonium perchlorates, and mixtures of two or more thereof.

1 5. An explosive as claimed in Claim 1 3 or Claim 14 wherein the oxidising saft is present in an aqueous solution.

1 6. An explosive as claimed in Claim 14 wherein the discontinuous phase includes ammonium nitrate and a compound which, together with the ammonium nitrate, forms a melt which has a melting point which is lower than that of the ammonium nitrate, the compound being capable of acting as an oxygen releasing salt or fuel.

1 7. An explosive as claimed in any one of the claims 1 3 to 16, wherein the fuel forms 2 to 25% by mass of the emulsion.

1 8. An explosive as claimed in any one of the Claims 1 3 to 17, wherein the fuel is organic and non-self-explosive.

1 9. An explosive as claimed in Claim 1 8 wherein the fuel includes a member selected from the group consisting of mineral oils, fuel oils, lubricating oils, liquid paraffin, micro-crystalline waxes, paraffin waxes, xylene, petrolatum, toluene, dinitrotoluene, and mixtures of two or more thereof.

20. An explosive as claimed in any one of Claims 1 3 to 1 9 wherein the fuel includes an emulsifier in addition to reaction products of the said amine and acid and/or acid halide.

21. An explosive as claimed in Claim 20 wherein the emulsifier comprises a member selected from the group consisting of sorbitan sesquioleate, sorbitan monooleate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, the mono-and di-glycerides of fatforming fatty acids, soya bean lecithin, derivatives of lanolin, alkyl benzene sulphonates, oleyl acid phosphate, laurylamine acetate, decaglycerol decaoleate, decaglycerol decastearate, polymeric emulsifiers containing polyethylene glycol back bones with fatty acid side chains, and suitable mixtures of two or more thereof.

22. An explosive as claimed in any one of Claims 13 to 21 wherein the density of the emulsion is from 1,30 g/ml to 1,45 g/ml at 25"C.

23. An explosive as claimed in any one of claims 13 to 21 which includes microballoons.

24. An explosive as claimed in Claim 23 which has a density of 1,1 5 to 1,20 g/ml at 25"C.

25. An explosive as claimed in Claim 23 or Claim 24 wherein the microballoons are of glass or polymeric material and form from 1 % to 3% by mass of the emulsion.

26. A novel explosive substantially as herein described and illustrated.