WO2014019011A1

WO2014019011A1 - Emulsion composition

Info

Publication number: WO2014019011A1
Application number: PCT/AU2012/001405
Authority: WO
Inventors: Mildred ESTRADA; David Peter Dowdell; Carlos Catibog ILAO, Jr
Original assignee: Croda Singapore Pte Limited
Priority date: 2011-11-14
Filing date: 2012-11-14
Publication date: 2014-02-06

Abstract

An emulsion explosive composition is described comprising an effective amount of an explosive oxidizer material and an alkyl (meth)acrylate copolymer having a long alkyl group chain. The copolymer is present in a self-emulsifying composition which forms the base of the emulsion explosive composition. The copolymer and self-emulsifying composition are used to stabilise an emulsion explosive composition. A method is also provided for stabilising an emulsion explosive composition. The method comprises adding an alkyl (meth)acrylate copolymer to an emulsion comprising an explosive material.

Description

Emulsion Composition

The present invention relates to an emulsion comprising an effective amount of an oxidizer material for use in mining applications. In particular, the present invention provides an emulsion system for emulsion explosives, providing high, and controllable, stability for the emulsion, and good viscosity in the presence of high levels of electrolytes.

Emulsion explosives are widely used in mining applications. The explosives comprise an effective amount of an oxidizer in an emulsion system and preferred oxidizer materials are usually ammonium nitrates.

Emulsion explosives are water in oil emulsions with a super saturated oxidizer salt solution as the internal water phase. Emulsion stability can be a big challenge in these high-electrolyte systems.

Existing emulsification systems used in emulsion explosives are generally based on three different technologies. The first is sorbitan esters. These are based on esters such as sorbitan monooleate, sorbitan dioleate, sorbitan sesquioleate and sorbitan monoisostrearate. The second system is one based on PIBSA (polyisobutene succinic anhydride). These PIBSA systems are typically produced from the reaction between PIB (polyisobutene) with maleic anhydride. The third type of emulsification system generally used for emulsion explosives is based on PIB-lactone chemistry. These systems are typically produced by reacting a PIBSA with a suitable amine such as triethanolamlne, diethanolamlne or monoethanolamine. Combinations of the above types of emulsification systems are also known for use in emulsion explosives. For example, blends of sorbitan monooleate and either PIBSA or PIB-lactone based emulsifiers are known.

Emulsion systems such as those of the types described above, and especially the sorbitan ester type emulsification systems, are not as effective or stable in situations where a high level of electrolytes are present. In emulsions where there is a high level of elecrolytes present, the emulsion systems do not show good stability and start to degrade, in some cases rapidly. Therefore, emulsions explosives tend to be produced and used within a relatively short space of time to ensure that the emulsion is stable at the time of use. In view of this, there exists a need to provide an emulsification system for an emulsion explosive that exhibits good stability at high electrolyte levels. There exists also a need to provide emulsification systems which allow stability to be controlled and tailored to meet requirements of particular end uses. It is an object of the present invention to address one or more of the above-mentioned or other disadvantages associated with the prior art.

According to a first aspect of the invention, there is provided an emulsion explosive composition comprising an effective amount of an explosive oxidizer material and an alkyl (meth)acrylate copolymer having a long alkyl group chain.

Preferably, the emulsion explosive composition is a water-in-oil emulsion. The long chain alkyl (meth)acrylate copolymer comprises the polymerisation product of monomers of (meth)acryllc acid. The long chain alkyl (meth)acrylate copolymer further comprises monomers of an alkyl (meth)acrylate ester.

By the term (meth)acrylic acid, it is meant either acrylic acid, methacryllc acid or a mixture of acrylic acid and methacryllc acid. Preferably, the copolymer comprises monomers of the polymerisation product of acrylic acid.

Preferably, the alkyl (meth)acrylate ester comprises an alkyl carbon chain length of from 16 to 24 carbon atoms inclusive, preferably of from 18 to 24 carbon atoms inclusive, more preferably of from 20 to 22 carbon atoms inclusive and most preferably 22 carbon atoms. Preferably, the alkyl group in the alkyl (meth)acrylate ester is provided by a fatty alcohol. Suitable alcohols for the esterification reaction include cetyl alcohol, stearyl alcohol, eicosanol, behenyi alcohol and tetracosanol, preferably behenyi alcohol. Preferably, the alkyl group is a saturated alkyl group. Preferably, the alkyl group is linear.

More than one alcohol may be used for the esterification reaction. Preferably, where more than one alcohol is used, the alkyl (met h)acry late ester comprises 40% or more by weight of C₂₀-C₂₂ alkyl groups, preferably C₂₂, preferably, the alkyl (meth)acrylate ester comprises 50% or more by weight of C₂₀-C₂₂ alkyl groups, preferably C₂₂, more preferably, the alkyl (meth)acry!ate ester comprises 60% or more by weight of C₂₀-C₂₂ alkyl groups, preferably C₂₂, more preferably, the alkyl (meth)acrylate ester comprises 70% or more by weight of C₂₀-C₂₂ alkyl groups, preferably and most preferably, the alkyl (meth)acrylate ester comprises 80% or more by weight of C₂₀-C₂₂ alkyl groups, preferably C₂₂.

Preferably, the alkyl (meth)acrylate ester comprises an alkyl methacrylate ester. Preferably, the alkyl (meth)acrylate ester consists essentially of an alkyl. methacrylate ester Preferably, the alkyl methacrylate ester Is stearyl methacrylate, elcosanyl methacrylate, behenyl methacrylate and/or tetracosanyl methacrylate, preferably behenyl methacrylate.

The copolymer may comprise monomers of more than one alkyl (meth)acrylate ester.

Preferably, the copolymer comprises from 0.5 to 5 parts by weight of alkyl (meth)acrylate monomers per 100 parts by weight of (meth)acrylic acid monomers, preferably from 1 to 3 parts by weight of alkyl (meth)acrylate monomers per 100 parts by weight of (meth)acrylic acid monomers, more preferably from 1.5 to 2.5 parts by weight of alkyl (meth)acrylate monomers per 100 parts by weight of (meth)acryiic acid monomers, and most preferably, from 1.8 to 2.2 parts by weight of alkyl (meth)acrylate monomers per 100 parts by weight of (meth)acrylic acid monomers.

Preferably, the copolymer has a high viscosity in the presence of electrolytes.

The copolymer may be effective as an emu!silier in an emulsion explosive composition. Preferably, the copolymer is water soluble. Preferably, the copolymer is in the form of a fine powder. Preferably, the copolymer forms part of the oil phase of the emulsion explosive composition.

Preferably, the copolymer is present in the emulsion explosive composition at a concentration in the range of from 0.001 to 1% by weight based on the total weight of the emulsion explosive composition, preferably from 0.005 to 0.8%. more preferably from 0.01 to 0.5% and most preferably from 0.05 to 0.35% by weight based on the total weight of the emulsion explosive composition.

The explosive oxidizer material may any suitable material capable of detonation. .Examples of explosive materials comprise nitroglycerin, trinitrotoluene (TNT), octogen (or HMX), pentaerythritol tetranitrate (PETN), nitrocellulose and nitrates, such as ammonium nitrate, sodium nitrate and calcium nitrate. Preferably, the explosive oxidiser material is any nitrate, such as ammonium nitrate, sodium nitrate and calcium nitrat.e or any combination of two or more or all of these. Preferably, the explosive material Is ammonium nitrate. Preferably, the explosive oxidizer material is present in the emulsion explosive composition at a concentration in the range of from 20 to 90% by weight based on the total weight of the emulsion explosive composition, more preferably from 35 to 85%, more preferably from 40 to 80% and most preferably from 65 to 75% by weight based on the total weight of the emulsion explosive composition. The ratio of copolymer to explosive oxidizer material In the emulsion explosive composition is preferably at least 1 :50 preferably at least 1 :100, preferably at least 1:150, most preferably at least 1:200. The ratio of copolymer to explosive material in the emulsion explosive composition is preferably up to 1:5000, preferably up to 1:3000. more preferably up to 1:1000 and most preferably up to 1:800.

Preferably, the emulsion explosive composition further comprises a fuel oil. Preferably, the fuel oil is a fraction obtained from petroleum distillation, either as a distillate or a residue such as paraffin wax. Preferably, the fuel oil Is selected from the group of petroleum fractions that are liquid at ambient temperature. Preferably, the fuel oil is selected from the group comprising kerosene, diesei oil, lubricating oils, mineral oil and paraffin. Preferably, the fuel oil is diesei oil or mineral oil, more preferably diesei oil. Alternatively, the fuel oil may be selected from non-petroleum based oils and waxes For example, the fuel oil may be selected from the group comprising glyceride oils, vegetable oils, vegetable waxes, ester oils and silicone oils, and mixtures thereof.

Furthermore, the fuel oil may be a recycled oil, for example mineral oils which are reoyoled from cooling systems for example in power stations, and treated to become solvent neutral.

Preferably, the fuel oil Is present in the emulsion explosive composition at a concentration in the range of from 1 to 20% by weight based on the total weight of the emulsion explosive composition, more preferably from 2 to 17% by weight, more preferably from 4 to 14% and most preferably from 5 to 10% by weight based on the total weight of the emulsion explosive composition.

The ratio of copolymer to fuel oil in the emulsion explosive composition is preferably at least 1:5 preferably at least 1:10, preferably at least 1:15. most preferably at least 1:20. The ratio of copolymer to fuel oil in the emulsion explosive composition is preferably up to 1:500, preferably up to 1:300, more preferably up to 1:100 and most preferably up to 1:80.

Preferably, the emulsion explosive composition further comprises one or more emulsifiers. Preferably, the or each emulsifier is selected from the group comprising sorbitan esters, suoh as sorbitan monooleate (SMO), such as Span™ 80 (ex Croda) and sorbitan monoisostearate, glyceryl monooleates, polyglyceryl polyricinoieates, polyethylene glycol polyhdroxystearates, PIBSA (polyisobutene succinic anhydride)-based and PIB-lactone-based emulsifiers, such as Anfomul™ 2887 (ex Croda). Preferably/ the emulsion explosive composition comprises either a sorbitan ester emulsifier or a PIBSA or PIB-lactone emulsifier, preferably a sorbitan ester emulsifier. Alternatively, a combination of a sorbitan ester emulsifier and/or a PIBSA and/or PIB-lactone emulsifier may be used.

Preferably, the total concentration of emulsifier present in the emulsion explosive composition Is in the range of from 0.01 to 10% by weight based on the total weight of the emulsion explosive composition, more preferably from 0.05 to 7% by weight, more preferably from 0.1 to 5% and most preferably from 0.5 to 2% by weight based on the total weight of the emulsion explosive composition.

The ratio of copolymer to emulsifier in the emulsion explosive composition is preferably at least 1:1 preferably at least 1:2, preferably at least 1:5, most preferably at least 1:7. The ratio of copolymer to emulsifier in the emulsion explosive composition is preferably up to 1:60, preferably up to 1 :30, more preferably up to 1 :15 and most preferably up to i :9.

Preferably, the emulsion explosive composition further comprises water. Preferably, water is present in the emulsion explosive composition at a concentration in the range of from 5 to 60% by weight based on the total weight of the emulsion explosive composition, more preferably from 7 to 40% and most preferably from 10 to 20% by weight based on the total weight of the emulsion explosive composition. Preferably, the explosive oxidizer material is present in the water phase of the emulsion.

Preferably, the emulsion explosive composition is mildly acidic. Preferably, the pH of the emulsion explosive composition is In the range of from 3 to 8, preferably from 4 to 7, more preferably from 5 to 7, and most preferably from 5.5 to $.5.

Preferably, the viscosity of the emulsion explosive composition Is In the range of from 10 to 200 Pa-s, preferably from 18 to 175 Pa-s, more preferably from 20 to 150 Pa-s and most preferably from 23 to 120 Pa-s measured on a Brookfield RVT viscometer using spindle 7 at 20rpm and 80°C.

Preferably, the viscosity and stability of the emulsion explosive composition is dependent on the pH of the composition.

Preferably, the emulsion explosive composition exhibits good thermal stability. Preferably, the emulsion composition is stable up to 40*0, preferably up to S0^eC, more preferably up to 55^SC and most preferably up to 60^eC. Preferably, the emulsion explosive composition exhibits good thermal stability at a low concentration of copolymer, preferably at a concentration of the copolymer of 0.05% by weight based on the total weight of the emulsion explosive composition.

Preferably, the emulsion explosive composition is stable for at least 1 month, preferably at least 3 months and more preferably at least 5 months. Preferably, the emulsion explosive composition exhibits long term stability at a low concentration of copolymer, for example at a concentration of the copolymer of 0.05% by weight based on the total weight of the emulsion explosive composition. Sorbitan ester emulsifiers. especially SMOs, are known to produce relatively unstable emulsions explosive compositions, especially in the presence of diesel oil as the fuel oil. However, the applicant has surprisingly found that, in the presence of the copolymer, a stable emulsion explosive composition can be provided using both sorbitan ester emulsifiers, such as SMO, and diesel oil.

The emulsion explosive composition may comprise further additional components. For example, the additional components of the emulsion explosive composition may comprise one or more of a chemical gassing aid, a physical gassing aid, a prilled oxidizer and/or one or more antioxidants.

Preferably, the alkyl (meth)acrylate copolymer of the first aspect of the Invention Is part of a self-emulsifying composition according to the second aspect of the present Invention as described hereunder. Preferably, the emulsion explosive composition comprises the self- emulsifying composition of the second aspect of the invention.

According to a second aspect of the present invention, there is provided a self-emulsifying composition comprising an alkyl (meth)acrylate copolymer.

In the second aspect of the invention, the alkyl (meth)acrylate copolymer is as described in relation to the first aspect of the invention.

Preferably, the alkyl (meth)acrylate copolymer is present in the self-emulsifying composition at a concentration of from 1 to 20% by weight based on the total weight of the self-emulsifying composition, more preferably from 3 to 17% by weight, more preferably from 5 to 14% and most preferably from 7 to 10% by weight based on the total weight of the self-emulsifying composition. Preferably, the copolymer is present in the self-emulsifying composition at a concentration of at least 1.5% by weight based on the total weight of the self-emulsifying composition, preferably at least 2% and more preferably at least 3% by weight based on the total weight of the self-emulsifying composition. Preferably, the copolymer is present in the self-emulsifying composition at a concentration of up to 20% by weight based on the total weight of the self-emulsifying composition, preferably up to 15% and more preferably up to 10% by weight based on the total weight of the self-emulsifying composition. Preferably, the self-emulsifying composition further comprises one or more emulsifiere. The or each emulsifier is as described in relation to the first aspect of the invention.

Preferably, the concentration of the emulsifier(s) present in the self-emulsifying composition is in the range of from 20 to 95% by weight based on the total weight of the self-emulsifying composition, more preferably from 30 to 90% by weight, more preferably from 45 to 80% and most preferably from 65 to 75% by weight based on the total weight of the eelf-emulslfying composition.

Preferably, the self-emulsifying composition further comprises a stabilizer, preferably a thickening agent. The stabilizer is preferably a natural or synthetic wax, more preferably a vegetable-derived wax. The stabilizer is preferably selected from the group comprising high melting point waxes, such as tribehenin. paraffin wax, microcrystalline wax. beeswax, carnauba wax, long chain glycol esters and long chain acid triglycerides. Preferably, the stabilizer is tribehenin (fully hydrogenated high erucic rapeseed oil with a minimum C_& content of 35% by weight - ex Walter Rau).

Preferably, the stabilizer is present in the self-emulsifying composition at a concentration of from 0.1 to 10% by weight based on the total weight of the self-emulsifying oomposition, more preferably from 0.3 to 8% by weight, more preferably from 0.5 to 6% and most preferably from 1 to 4% by weight based on the total weight of the self-emulsifying composition.

Preferably, the ratio of the copolymer to the stabilizer present in the self-emulsifying composition is at least 0.1 :1 , preferably at least 0.5:1 , more preferably at least 1:1 and most preferably at least 2:1. Preferably, the ratio of copolymer to stabilizer in the self-emulsifying composition is up to 50:1 , preferably 25:1 , more preferably 10:1 and most preferably 7:1.

In one embodiment, the self-emulsifying composition further comprises a non-ionic surfactant and/or a dispersing agent. Preferably, when present, the non-ionic surfactant present in the setf-emulsifying composition is a surfactant derived from natural materials such as fatty acid esters, ethers, hemi-acetals or acetals of polyhydroxylic compounds or a fatty acid amide which is N-substituted with the residue of a polyhydroxylic•compound. When present, the non-ionic surfactant may have the same composition as the one of the, or the, emulsifier(s) present in the self -emulsifying composition.

Preferably, the non-ionic surfactant is an ester of a polyhydroxylic compound, such as esters of fatty acids, preferably fatty acids having from 8 to 24, more preferably 12 to 22, and particularly 16 to 20 carbon atoms, and polyols, particularly glycerol or a polyglycerol, or an anhydro- saccharide such as sorbitan. Preferred non-ionic surfactants are glycerol esters where the fatty acid has 14 to 24 carbon atoms such as glycerol mono-stearate, -oleate, or -laurate; and anhydrosaccharide fatty esters such as sorbitan mono-stearate, -isostearate, -cocoate or - laurate. More preferably, the non-ionic surfactant is selected from the group consisting of sorbitan cocoates, sorbitan stearates, sorbitan isostearates, alKoxylated fatty acids, alkoxylated fatty alcohols, glycerol mono-oleates, glycerol Isostearates, polyglycerol oleates, polyglycerol ricinoleates and polyglycerol isostearates, and mixtures thereof. Preferably, the non-Ionic surfactant is polygIycerol-3 polyricin oleate, for example, of the type available commercially as Cithrol™ PG3PR (ex Croda).

Preferably, the non-ionic surfactant is present in the self-em ulsifylng composition In the range of from 0.1 to 5% by weight based on the total weight of the self-emulsifying composition, more preferably from 0.5 to 4% by weight, more preferably from 1 to 3% and most preferably from 1.5 to 2.5% by weight based on the total weight of the self-emulsifying composition.

Preferably, where present, the dispersing agent is selected from the group consisting of the reaction products of monocarboxylic acid, di- or tri-carboxylic acids having 2 to 12 carbon atoms, more preferably having 4 to 6 carbon atoms, and mixtures thereof reacted with short chain alcohols of between 1 and 6 carbon atoms and mixtures thereof.

It will be appreciated that the carboxylic acids, fatty alcohols and alkoxy groups used in reactions to produce the preferred alkoxylated dispersing agents used in the present invention often contain a variety of similar compounds of various carbon chain lengths, especially when derived from natural resources and references to specific acids and alcohols refer to the primary or major components of the materials used.

More preferably, the dispersing agent is selected from the group consisting of the reaction products of di- or tri-carboxylic acids having 4 to 6 carbon atoms and mixtures thereof reacted with short chain alcohols of between 1 and 5 carbon atoms, more preferably between 1 and 3 carbon atoms, and mixtures thereof. Particularly preferred carboxylic acids include the dicarboxyiic acids maleic. succinic and adipic acids and the tricarboxylic acid citric acid. Particularly preferred alcohols include methanol, ethanol and propanol. More preferably, the dispersing agent Is trimethyl citrate (TMC). Preferably, the dispersing agent is immiscible in water.

Preferably, the dispersing agent is present in the self-em ulslfylng composition at a concentration in the range of from 1 to 10% by weight based on the total weight of the self- emulsifying composition, more preferably from 2 to 8% by weight, more preferably from 3 to 6% and most preferably from 3.5 to 4.5% by weight based on the total weight of the self- emulsifying composition.

In a particularly preferred embodiment of the invention .the self-emulsifying composition comprises both a dispersing agent and a non-ionic surfactant as described herein.

Preferably, the self-emulsifying composition further comprises an organic medium. Preferably, the organic medium comprises one or more oily materials which are liquid at ambient temperature. Examples of suitable mediums include, but are not limited to those selected from the group Including fatty alcohols, glycols, glyceride oils, vegetable oils, ester oils, fatty alcohol alkoxylates, alkyl carbonates, mineral oils and silicone oils, and mixtures thereof. Preferably, the organic medium comprises at least one mineral oil, particularly light mineral oil.

The concentration of the organic medium is preferably in the range of from 1 to 50% by weight based on the total weight of the self-emulsifying composition, more preferably from 2 to 40% by weight, more preferably from 5 to 30% and most preferably from 10 to 15% by weight based on the total weight of the self-emulsifying composition.

Preferably, the self-emulsifyirig composition is anhydrous. By anhydrous, it is meant that the self-emulsifying composition comprises less than 5% by weight of water based on the total weight of the self-emulsifying composition, preferably less than 3% by weight water and most preferably less than 1% by weight water based on the total weight of the self-emulsifying composition.

In one embodiment, the copolymer is operable to be added to the self-emuisifying composition in the form of a pre-dispersion. Preferably, the pre-dispersion forms a component of the self- emulsifying composition. Preferably, the pre-dispersion is present in the self -emulsifying composition at a concentration of from 1 to 60% by weight based on the total weight of the self- emulsifying composition, more preferably from 5 to 50% by weight, more preferably from 15 to 45% and most preferably from 25 to 35% by weight based on the total weight of the self- emulsifying composition.

Preferably, the copolymer is present in the pre-dispersion at a concentration of from 1 to 60% by weight based on the total weight of the pre-dispersion, more preferably from 5 to 50% by weight, more preferably from 15 to 45% and most preferably from 25 to 35% by weight based on the total weight of the pre-dispersion.

Preferably, the pre-dispersion comprises the copolymer dispersed In an organic liquid medium phase which comprises the dispersing agent, non-ionic surfactant and the organic medium. The organic medium acts in this embodiment as a dispersing medium.

The concentration of the organic dispersing medium is preferably in the range of from 20 to 80% by weight based on the total weight of the pre-dispersion, more preferably from 30 to 70% by weight, more preferably from 40 to 60% and most preferably from 45 to 55% by weight based on the total weight of the pre-dispersion.

Preferably, the dispersing agent and/or the non-ionic surfactant described above form part of the pre-dispersion. Preferably, the dispersing agent is miscible in the organic dispersing medium. Preferably, the self-emulsifying composition comprises the pre-dispersion comprising the dispersed copolymer; the or each emulsifier; and the thickening agent.

In an alternative embodiment, the copolymer may be combined with the or each additional emulsifier and the thiokening agent in the self-emulsifying composition directly.

Preferably, the self-emulsifying composition forms a part of the oil phase of an emulsion explosive composition. Preferably, the self-emulsifying composition is present in the emulsion explosive composition at a concentration in the range of from 0.1 to 10% by weight based on the total weight of the emulsion explosive composition, more preferably from 0.2 to 8% by weight, more preferably from 0.3 to 5% and most preferably from 0.5 to 2.5% by weight based on the total weight of the emulsion explosive composition. The invention further extends to an emulsion explosive composition according to the first embodiment of the invention consisting essentially of:

a) a self-emulsifying composition according to the second aspect of the invention comprising an alkyl (meth)acrylate copolymer;

b) an effective amount of an explosive oxidizer material;

c) a fuel oil; and

d) water. According to a third aspect of the present invention, there is provided a pre-emulsion composition comprising the self -emulsifying composition of the second aspect of the invention and water.

Preferably, ratio of self-emulsifying composition to water is from 1:1 to 1:10, preferably from 1:1.5 to 1:7, more preferably from 1:2 to 1 :5 and most preferably from 1:2.5 to 1:4.

Preferably, the water dilution of the self-emulsifying composition provides a mildly acidic pre- emulsion composition. Preferably, the pH of the pre-emulsion composition is in the range of from 3 to 8, preferably from 4 to 7, more preferably from 5 to 7, and most preferably from 5.5 to 6.5.

Preferably, the viscosity of the pre-emulsion composition Is in the region of from 12 to 40 Pa-s, preferably from 15 to 35 Pa s, more preferably from 20 to 30 Pa-s and most preferably from 23 to 27 Pa s.

Preferably, the pre-emulsion composition further comprises one or more additional components such as, for example, a base oil, a processing aid, a thickening agent(s), a fuel oil, and/or surfactant(s). Preferably, the or each additional component is a stabilizer. Preferably, the or each additional component Is operable to stabilize the pre-emulsion.

The or each additional base oil is preferably a mineral oil. Preferably, the base oil is a re-used, re-processed or recycled mineral oil.

Preferably, the or each processing aid is an ester-based compound, preferably a polymeric ester, more preferably a polyether-based ester. The additional thickening agent(s) and/or surfactant(e) in the present aspect are as defined in relation to the second aspect of the invention. Preferably, the additional component(s) comprises a surfactant. The additional surfactant may be a sorbitan ester, such as sorbitan monooleate (SMO) and sorbitan monoisostrearate, PIBSA (polyisobutene succinic anhydride)- based and PIB-lactone-based surfactant, preferably a PIB-lactone-type surfactant.

Preferably, the pre-emulsion composition further comprises a glycerol-derived oil, for example a triglyceride. The glycerol-derived oil is preferably a viscosity modifier, preferably a viscosity modifier to increase the flowability of the pre-emulsion, and/or a plasticising agent.

When present in the pre-emulsion, the base oil is preferably present at a concentration of up to 30%. preferably 25%,,more preferably 20% and most preferably 15% by weight based on the total weight of the pre-emulsion. When present In the pre-emulsion, the base oil is preferably present at a concentration of at least 1%, preferably 5%, more preferably 8% and most preferably 10% by weight based on the total weight of the pre-emulsion.

When present in the pre-emulsion, the processing aid is preferably present at the lowest concentration possible to be effective. When present in the pre-emulsion, the processing aid is preferably present at a concentration of up to 3%, preferably 2%, preferably 1%. more preferably 0.6% and most preferably 0.3% by weight based on the total weight of the pre- emulsion. When present In the pre-emulsion, the processing aid is preferably present at a concentration of at least 0.01%, preferably 0.05%, more preferably 0.08% and most preferably 0.1 % by weight based on the total weight of the pre-em ulsion. When present in the pre-emulsion, the surfactant is preferably present at a concentration of up to 15%, preferably 10%, more preferably 8% and most preferably 5% by weight based on the total weight of the pre-emulsion. When present in the pre-emulsion, the surfactant is preferably present at a concentration of at least 0.1%, preferably 0.5%, more preferably 1% and most preferably 2% by weight based on the total weight of the pre-emulsion.

Preferably, the pre-emulsion exhibits good long-term stability. Preferably, the pre-emulsion composition is stable for at least 1 month, preferably at least 3 months and more preferably at least 5 months. Preferably, the pre-emulsion composition exhibits good thermal stability. Preferably, the pre- emulsion composition is stable at temperatures of up to 50^BC, preferably up to 60°0, more preferably up to 70^eC and most preferably up to 90^eC. Preferably, the thermal stability of the pre-emulsion makes the composition highly suitable for use in the preparation of cartridge-type emulsion explosives, where continuous processing of the emulsion is undertaken at relatively high temperatures (between SO and 120^SC). According to a fourth aspect of the present invention, there is provided a method of stabilising an emulsion explosive composition, the method comprising adding an alkyl (meth)acrylate copolymer to an emulsion comprising an explosive material.

The alkyl (meth)acrylate copolymer in this aspect of the invention Is as described above in relation to the first aspect of the invention.

Preferably, the emulsion explosive composition Is as described in the first aspect of the invention. According to a fifth aspect of the present invention, there is provided the use of an alkyl (meth)acryiate copolymer to stabilise an emulsion explosive composition.

Preferably, the alkyl (meth)acrylate copolymer is as described in relation to the first aspect of the invention.

According to a further aspect of the present invention, there Is provided a method of manufacturing an emulsion explosive composition, the method comprising the steps of:

a) preparing self-emulsifying composition comprising an alkyl (meth)acrylate copolymer;

b) mixing the self-emulsifying composition with a fuel oil to form an oil phase;

c) preparing a water phase comprising an explosive material and water; and d) mixing the oil phase with the water phase.

In one embodiment, the step of preparing the self-emulsifying composition includes the step of preparing a pre-dlsperslon comprising the alkyl (meth)acrylate copolymer. The pre-dispersion is preferably prepared by forming a liquid phase by mixing together an organic dispersing medium, a dispersing agent and a non-ionic surfactant, and then dispersing the copolymer, in particulate form, in the liquid phase. Preferably, low shear mixing is used, such as with a paddle mixer. Furthermore, preferably, the mixing occurs without heating, i.e. at low or ambient temperature.

Preferably, the step of preparing the self-emulsifying composition further comprises mixing the pre-dispersion with one or more additional emulsifiers and a thickening agent. Preferably, the step of preparing the oil phase further comprises heating the explosive material and self-emulsifying composition to a temperature in the range of from 40ºC to 90ºC, preferably 47ºC to 80*0, more preferably 55°C to 65°C, and most preferably, approximately 60ºC

Preferably, the step of preparing the water phase also comprises adjusting the phi of the water phase using soda ash. Preferably the pH is adjusted to be in the range of from 4 to 9, preferably of from 4.5 to 7.5, more preferably of from 5 to 6, and most preferably, 5.5. Preferably, the step of preparing the water phase comprises heating the water phase to a temperature in the range of from 50°C to 100ºC, preferably 60ºC to 90ºC, more preferably 70º to 85ºC, and most preferably, approximately 80*0.

Preferably, the step of mixing the oil and water phases occurs under stirring.

In an alternative embodiment, the oil phase can be mixed with the water phase without being first heated. In this embodiment, the water phase can provide the required heat for the oil phase. Preferably, in this embodiment, the oil phase is at a temperature of between 5ºC and 60ºC, preferably between 10ºC and 50ºC, more preferably between 15º0 and 45ºC, and most preferably between 20*0 and 40ºC.

In a further alternative embodiment, controlled mixing at gradually increasing rpm is used to avoid the need for soda ash to be added to the water phase to adjust the pH. In this embodiment, the water phase and oil phase are combined under low speed mixing, preferably at around 100-800rpm. preferably at 200 to 700 rpm, more preferably at 300 to 650rpm and most preferably at 400 to 550 rpm. The speed of the mixing is preferably increased gradually as the emulsification of the water phase and oil phase begins. Preferably, as the emulsion thickens, the speed of mixing is gradually increased up to a maximum of around 1000 to 2500 rpm, preferably to a maximum of 1100 to 2200 rpm, more preferably to a maximum of 1200 to 1800 rpm and most preferably to a maximum of 1400 to 1600 rpm. Preferably, the increase in mixing is performed In a series of stages at step-wise increments, preferably about 2 to 5 Increments.

Preferably, the emulsion explosive composition exhibits good stability for a period of at least one month, preferably six weeks.

Any of the aforementioned features may be taken in any combination and with any aspect of the invention. Exemples

The invention will now be Illustrated further by the following non-llmlting examples. All parts and percentages are given by weight of the total composition unless otherwise stated. Example 1 - Preparation of self-emulsifying composition: Formulation 1

345g (69% w/w) of Span™ 80 (ex Croda) (sorbitan monooleate) and 17g (3.4% w/w) of tribehenin were heated together in a first 500g reactor vessel to a temperature of 70 deg C. The heating continued until the 70 deg C temperature was reached or until the tribehenin had completely melted. The mixture was then cooled to between 30 and 40 deg C.

In a second, separate 500g reactor vessel, 245g (49% w/w) of mineral oil, 35g (7% w/w) of polyglyceryl polyricinoleate and 70g (14% w/w) of Crodamol TMC (ex Croda) were combined and mixed until completely homogeneous. 150g (30% w/w) of an alkyl methacrylate copolymer was then added to the reactor vessel gradually with vigorous agitation until all of the powder was wetted out. The mixture was then mixed moderately for an hour until the dispersion looked smooth when seen against a metal spatula.

The dispersion was a milky, viscous liquid at 23 deg C, with a white to off-white colour. The dispersion had a pH of approximately 3.5, and a viscosity of approximately 5000 CPs In a 2.5% aqueous solution with 5% Glycerox HE at pH 5.5. The viscosity was measured on a Brookfield DVII+, RVT sp#5 at 10rpm, time to shear 60sec, 23 deg C. '

138g (27.6% w/w) of the dispersion from the second reactor vessel was then added to the first reactor vessel under slow mixing with an anchor-type or ribbon impeller.

The resulting composition was an off-white to light yellow, creamy liquid having a viscosity of approximately 4500 cPs ± 1500 CPs. The viscosity of the neat composition was measured on a Brookfield DVII+, RVT sp#5 at 10rpm, time to shear 60sec, 23 deg C.

Example 2 - Preparation of self-emulsifying composition: Formulation 2

176g (35.2% w/w) Anfomul™ 2887 (ex Croda) (PIB-lactone), 176g (35.2% w/w) Span™ 80 (ex Croda) (sorbitan monooleate) and 7g (1.4% w/w) tribehenin were mixed together in a first 500g reactor vessel and heated to 70 deg C. The heating continued until the 70 deg C temperature was reached or until the tribehenin had completely melted. The mixture was then cooled to between 30 and 40 deg C. I4lg (28.2% w/w) of the dispersion of the second reactor vessel of [Example 1 was then added to the first reactor vessel under slow mixing with an anchor-type or ribbon impeller. No shear was applied to the mixture since this had the result of thickening the product. The resulting composition was a yellowish brown to brown, viscous liquid having a viscosity of approximately 5500 CPs ± 1500 CPs. The viscosity of the neat composition was measured on a Brookfield DVII+, RVT sp#5 at 10rpm, time to shear 60sec, 23 deg C.

Example 3 - Preparation of pre-emulsion

Water was added to Formulation 1 at a molar ratio of 3:1, and the mixture emulsified. The resultant emulsion was an off-white, creamy liquid.

Example 4 - Preparation of alternative pre-emulsion

Formulation 1 was added to TPR Base Oil Solvent Neutral 150™ (ex Transpacific Refiners) (mineral oil). Cithrol™ DPHS (ex Croda) and Anfomul™ 2887 (ex Croda) and mixed at 2000rpm for 5 minutes using a Silverson homogeniser. Deionised water was then added to the resulting mixture under low speed mixing at 500rpm for 10 minutes using a 4 blade impeller, and then mixed using a Robo mixer at 200rpm for 20 minutes. The proportions of the components in the resulting pro-emulsion were 20.5% by weight Formulation 1, 13.9% by weight TPR Base Oil Solvent Neutral 150, 0.1% by weight Cithrol DPHS, 4.0% by weight Anfomul 2887 and 61.5% by weight deionised water (to pH 6-7). All percentages are given by weight based on the total weight of the resulting pre-emulsion.

Example 5 - Preparation of emulsion explosive composition

7.5% w/w of diesel oil and 0.5% w/w of Formulation 1 were mixed together and heated to 60 deg C to form the oil phase of the emulsion.

In a separate vessel, 73.6% w/w of ammonium nitrate and 18.4% w/w of water were mixed together to form the aqueous phase of the emulsion. Soda ash was added to the ammonium nitrate solution to adjust the pH to 5.5. The pH adjusted ammonium nitrate solution was then heated to 80 deg C.

The heated aqueous phase was added to the oil phase while mixing at 300rpm over 30 seconds. The mixing speed was increased to lOOOrpm using a 4-biade paddle mixer for 10 minutes. Example 6 - Alternative preparation of emulsion explosive oompoeition

7.2% w/w of diesel oil and 2% w/w of the pre-emulsion of Example 4 were mixed together and heated to 60 deg C to form the oil phase of the emulsion.

In a separate vessel, 73.6% w/w of ammonium nitrate and 17.2% w/w of water were mixed together to form the aqueous phase of the emulsion. The ammonium nitrate solution was then heated to 60 deg C. The heated aqueous phase was added to the oil phase while mixing at 500rpm. After 30 seconds, the mixing speed was gradually increased to 700rpm, and then to lOOOrpm after another 30 seconds. The mixing speed was finally gradually increased to 1500rpm after the complete addition of the aqueous phase using a 4-blade paddle mixer for 10 minutes, No soda ash was required to adjust the pH of the emulsion.

Example 7 - Alternative preparation of emulsion explosive composition

7% w/w of diesel oil, 0.1% w/w of an alkyl methacrylate copolymer in powder form and 0.9% w/w of Span™ 80 (ex Croda) were mixed together and heated to 60 deg C to form the oil phase of the emulsion.

In a separate vessel, 67% w/w of ammonium nitrate and 25% w/w of water were mixed together to form the aqueous phase of the emulsion. Soda ash was added to the ammonium nitrate solution to adjust the pH to 5.5. The pH adjusted ammonium nitrate solution was then heated to 80 deg C.

The heated aqueous phase was added to the oil phase while mixing at 300rpm over 30 seconds. The mixing speed was increased to lOOOrpm using a 4-blade paddle mixer for 10 minutes.

Example 8 - Alternative preparation of emulsion explosive composition

7% w/w of diesel oil, 0.3% w/w of an alkyl methacrylate copolymer in solution and 0.9% w/w of Span™ 80 (ex Croda) were mixed together and heated to 60 deg C to form the oil phase of the emulsion.

In a separate vessel, 67% w/w of ammonium nitrate and 24.8% w/w of water were mixed together to form the aqueous phase of the emulsion. Soda ash was added to the ammonium nitrate solution to adjust the pH to 5.6. The pH adjusted ammonium nitrate solution was then heated to 80 deg C.

Example 9 - Stability Test of Emulsion

In the following stability tests, the emulsion explosive composition of Example 5 was used. The emulsion of Example 5 was subjected to thermal cycling, elevated temperature and room temperature stability tests. These are described below. In the tests, the emulsion of Example 5 was compared against samples of other emulsions which substituted the Formulation 1 component of the emulsion of Example 5 with other well-known emulsifiers at the same weight %.

9.1 - Thermal Cycling

A sample of 100ml of the emulsion was placed in a sealed glass container. The container was placed in a freezer set at a constant temperature of -20 deg C and left for a period of 24 hours. After 24 hours, the container was removed from the freezer and allowed to equilibrate to room temperature.

Once equilibrated to room temperature, the container was placed in an oven set at a constant temperature of 40 deg C and left for a period of 24 hours. The container was then removed from the oven and allowed to equilibrate to room temperature.

The sample was then evaluated using polarized light microscopy. This cycle was repeated 12 times, and the sample evaluated after each oyole. Each thermal cycle is the equivalent of approximately 6 weeks of room temperature stability.

The results of the thermal cycling tests are shown in Table 1 below and Figure 1 against analogous results taken from samples of emulsions containing SMO and PIBSA emulsifiers on their own. The images in Figure 1 were obtained from the emulsions using a microscope with 100X magnification and polarised light.

The same test was performed on the emulsion composition of Example 6 and the pre-emulsion of Example 4. These results are also given in Table 1.

Table 1: Thermal Cycling Results

9.2 - Elevated Temperature

A sample of 100ml of the emulsion was placed in a sealed glass container. The container was placed in an oven set at 40 deg C and left for a period of 1 week. After 1 week, the container was removed from the oven and allowed to equilibrate to room temperature. The sample was then evaluated using polarized light microscopy.

The test was repeated on the sample for 12 weeks, with analysis occurring after each week.

The results of the elevated temperature tests are shown in Table 2 below and Figures 2A and 2B against analogous results taken samples of emulsions containing SMO and PIBSA emulsifiers on their own. The images in Figures 2A and 2B were obtained from the emulsions using a microscope with 100x magnification and polarised light.

9.3 - Room Temperature

A sample of 100ml of the emulsion was placed in a sealed glass container. The container was placed in a cabinet at room temperature and left for a period of 1 week. After 1 week, the container was removed from the cabinet and the sample was evaluated using polarized light microscopy.

The results of the elevated temperature tests are shown In Table 3 below and Figures 3A and 3B against analogous results taken samples of emulsions containing SMO and PIBSA emulsifiers on their own. The Images in Figures 3A and 3B were obtained from the emulsions using a microscope with 100x magnification and polarised light.

9.4 - Re-pump Test

A re-pumpability rig was pressurised to a pressure of 70 psia. A sample of 50g of emulsion was introduced into the rig and the emlusion pumped into a beaker. The emulsion was observed by microscopy for the presence of any crystals, and the method repeated 4 times.

The results of the re-pump tests are shown h Table 4 below and Figure 4 against analogous results taken samples of emulsions containing SMO and PIBSA emulsifiers on their own. The images in Figure 4 were obtained from the emulsions using a microscope with 100x magnification and polarised light.

Table 4: Re-pump Results

The microscopy readings show that all emulsions formed ammonium nitrate crystals after successive pump cycles. However, on the 5th cycle, the emulsion of Example 5 has smaller and fewer crystals compared to the PIBSA and PIB-lactone emulsions, and hence is relatively more stable.

The present invention provides an electrolyte-resistant copolymer for use In a self-emulsifying composition and/or emulsion composition for use in emulsion explosive applications. The electrolyte resistance of the copolymer means that the polymer is able to inhibit the growth of nitrate salts which result from the presence of, for example, ammonium nitrate explosives, in an emulsion. It is the presence of nitrate salts that is the primary cause of emulsion breakdown and decrease in overall performance of an emulsion explosive. Therefore, the inhibition of nitrate salt growth by the copolymer provides a very stable emulsion. Furthermore, the present invention provides a self-emulsifying composition and an emulsion composition comprising the copolymer, which exhibit good stability and viscosity in formulations where high concentrations of electrolytes are present.

The copolymer of the present invention is further advantageous as it can be used effectively in single salt systems in contrast to current SMO-based emulsions. The self-emulsifying composition of the present invention provides emulsion explosive compositions which exhibit surprising stability properties. The self-emulsifying composition enables emulsions comprising SMOs to exhibit surprisingly good stability in the presence of electrolytes such as nitrates, and also enables emulsions comprising SMOs to exhibit surprisingly good stability in the presence of diesel oil, which traditionally does not provide for stable emulsions.

Any or all of the disclosed features, and/or any or all of the steps of any method or process described, may be combined in any combination. Each feature disclosed herein may be replaced by alternative features serving the same, equivalent or similar purpose. Therefore, each feature disclosed Is one example only of a generic series of equivalent or similar features.

The above statements apply unless expressly stated otherwise. The term specification, for these purposes, includes the description and any accompanying claims, abstract and drawings.

Claims

1. An emulsion explosive composition comprising an effeotive amount of an explosive oxidizer material and an alkyl (meth)aerylate copolymer having a long alkyl group chain.

2. The emulsion explosive composition according to claim 1, wherein the long chain alkyl (meth)acrylate copolymer comprises the polymerisation product of monomers of (meth)acryiic acid and monomers of an alkyl (meth)acrylate ester.

3; The emulsion explosive composition according to claim 2, wherein the alkyl (meth)acrylate ester comprises an alkyl carbon chain length of from 16 to 24 carbon atoms inclusive.

4. The emulsion explosive composition according to any preceding claim, wherein the copolymer comprises from 0.5 to 5 parts by weight of alkyl (meth)aorylate monomers per 100 parts by weight of (meth)acrylic acid monomers.

5. The emulsion explosive composition according to any preceding claim, wherein the copolymer is present in the emulsion explosive composition at a concentration in the range of from 0.001 to 1% by weight based on the total weight of the emulsion explosive composition.

6. The emulsion explosive composition according to any preceding claim, wherein the explosive oxidizer material is present in the emulsion explosive composition at a concentration in the range of from 20 to 90% by weight based on the total weight of the emulsion explosive composition.

7. A self-emulsifying composition comprising an alkyl (meth)acrylate copolymer according to any preceding claim. -

8. The self-emulsifying composition according to claim 7, wherein the alkyl (meth)acrylate copolymer is present in the self-emulsifying composition at a concentration of from 1 to 20% by weight based on the total weight of the self-emulsifying composition.

9. The self-emulsifying composition according to claim 7 or claim 8, wherein the self- emulsifying composition further comprises one or more emulsifiers.

10. The self-emulsifying composition according to 9, wherein the concentration of the emulsifier(s) present in the self-emulsifying composition is in the range of from 20 to 95% by weight based on the total weight of the self-emulsifying composition.

11. The self-emulsifying composition according to any of claims 7 to 10, wherein the self- emulsifying composition forms a part of the oil phase of an emulsion explosive composition.

12. An emulsion explosive composition according to any of claims, 1 to 6, consisting essentially of:

a) a sett-emulsifying composition according to the second aspect of the Invention comprising an alkyl (meth)acrylate copolymer;

b) an effective amount of an explosive oxidizer material;

c) a fuel oil; and

d) water.

13. A pre-emulsion composition comprising the self-emulsifying composition according to any of claims 7 to 11 and water.

14. The pre-emulsion composition according to claim 13. wherein the ratio of self- emulsifying composition to water is from 1 :1 to 1 :10.

15. A method of stabilising an emulsion explosive composition, the method comprising adding an alkyl (meth)acrylate copolymer to an emulsion comprising an explosive material.

16. The use of an alkyl (meth)acrylate copolymer to stabilise an emulsion explosive composition.

17. A method of manufacturing an emulsion explosive composition, the method comprising the steps of:

a) preparing serf-emulsffying composition comprising an alkyl (meth)acrylate copolymer;