NZ206131A

NZ206131A - Method of making an emulsion explosive

Info

Publication number: NZ206131A
Application number: NZ206131A
Authority: NZ
Inventors: J G B Smith
Original assignee: Aeci Ltd
Priority date: 1982-11-03
Filing date: 1983-11-02
Publication date: 1987-01-23
Also published as: GB8329301D0; ZW23383A1; GB2132999A; AU2093383A; CA1227038A; GB2132999B; AU563042B2

Description

New Zealand Paient Spedficaiion for Paient Number £06131 v~' I 3 1 Pri ority Date(s): Complete Specification Filed: Class: A . fi?k^P.ei/.<?A. . &? Publication Date: ... P.O. Journal, No: .... (£$/. 6'3 JANi HO OBJUHHS NEW ZEALAND PATENTS ACT, 1953 No.: Date: COMPLETE SPECIFICATION A METHOD OF MAKING AN EXPLOSIVE IN THE FORM OF AN EMULSION xpywe, AECI LIMITED of 16th Floor, Office Tower, Carlton Centre, Commissioner Street, Johannesburg, Transvaal Province, Republic of South Africa, a South African Company hereby declare the invention for which*! / we pray that a patent may be granted to 3s»fe/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - 206131 ^ - 2 - a THIS INVENTION relates to an explosive. In particular ^ the invention relates to an explosive of the emulsion type in whi<ih an oxidizing salt-containing component forms the discontinuous phase in an emulsion wherein the continuous phase 5 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 10 oxidizing salt component includes no water they can be regarded as "melt-in-fuel" 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 contin-15 uous 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 206i:i 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 tc 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 0 acid having a molecular weight of at least about 280. The carbon chain may be optionally branched but preferably unbranched and ideally may be of the formula CH,(CH_) COOH where n is from i z n 16 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 where x is from 2 to 5# eg c 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 O > -4. 206131 oleic acid chloride, with a diamine): Acid Amine Product C17H3 3COOH+NH2(CH2)XNH2 C17H33CONH(CH2) NH2+H20 Acid Chloride Amine Product c17h33coci+nh2(ch2)xnh2 c17h33conh(ch2)xnh2+hci It is believed that such reaction products act as sur- > factants 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 10 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% ni/m, preferably 2 to 5% m/m of the final 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 20 solid. 206131 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, t alkaline earth metal perchlorates, ammonium nitrate, ammonium perchlorate, and I mixtures of two or 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. 206131 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, decagly-cerol decaoleate, decaglycerol decastearate, polymeric emulsi-fiers containing polyethylene glycol backbones with fatty acid side chains, and suitable mixtures of two or more thereof.

The fuel will be immiscible 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, microcrystal-line waxes, paraffin waxes, xylene, petrolatum, toluene, dinit-rotoluene and mixtures of two or more thereof. 206131 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 microballoons 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 microbal loons, 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: 206131 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 petroleum-jelly 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 0,36g 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. ' '' 206131 9 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 tc 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. i 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. 206131 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 & 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 t 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 polyviny- 20613 - ii - lidene 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 i§ 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 inventior by itself provides enhanced shelf life when compared with Spar 80, a standard but expensive emulsifier used for this purpose, and even better results are obtained when the invention is usee 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 carbo xylic acids, carboxylic acid halides, and amines, which ca: potentially be used for the purpose of the present invention am routine experimentation will be required to determine reagent: and proportions thereof for particular emulsion explosive formulations .

O.'' & S£?n y

Claims

WHAT WE CLAIM IS:

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 oxidising 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 16 to 20.

6. A method as claimed in any one of the preceding claims wherein the acid is oleic acid. v : ■ -"?iV'1 -•;-;'r..-v -. —>j : '/*"*+ J *\ - * - is - 206131

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 an(^ x from 2 to 5. Q

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 f^j 7 to 9 wherein the amine has a molecular weight of from 70 to 120

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.

12. A method of making an explosive as defined according to any one of claims 1 to 11 inclusive substantially as herein described and exemplified.

13. An explosive in the form of an emulsion when prepared according to the method as claimed in any one of claims 1 to 12.

14. An explosive as claimed in claim 13 wherein O the oxidising salt comprises a member selected from the group consisting of alkali metal nitrates, >A ' es-% f'y c J3A(jGI936.' \-S< / - 14 - 205131 « alkali metal perchlorates, alkaline earth metal nitrates, alkaline earth metal perchlorates, ammonium nitrates, ammonium perchlorates, and mixtures of two or more thereof.

15. An explosive as claimed in claim 13 or claim 14 wherein the oxidising salt is present in an aqueous solution.

16. 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.

17. An explosive as claimed in any one of the . claims 13 to 16, wherein the fuel forms 2 to 25% by mass of the emulsion.

18. An explosive as claimed in any one of the claims 13 to 17, wherein the fuel is organic and non-self-explosive.

19. An explosive as claimed in claim 18 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. J - 15 - 206131

20. An explosive as claimed in any one of claims 13 to 19 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 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 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. VJ

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

24. An explosive as claimed in olaim 23 which has a density of 1.15 to 1.20 g/ml at 2 5°C. >£r4N0Vl986

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. An explosive as defined according to any one of claims 13 to 25 inclusive substantially as herein described and illustrated. j AT ED THIS 3r^ DAY OF19<H <-\ . J . p ™ H ■ a F AL/lzi'J i R;< & SON TriE APPLICANTS