CA1330395C - Explosive composition containing polymer soluble in the organic phase comprising associative functional groups - Google Patents

Abstract

ABSTRACT

AN EXPLOSIVE COMPOSITION CONTAINING A POLYMER SOLUBLE
IN THE ORGANIC PHASE COMPRISING ASSOCIATIVE FUNCTIONAL GROUPS

The invention relates to an elastic emulsion explosive composition comprising a discontinuous phase comprising at least one oxygen-releasing salt; a continuous organic phase; an emulsifying agent; and at least one polymer soluble in the organic phase and wherein the polymer comprises associative functional groups.

Description

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AN EXPLOSIVE COMPOSITION CONTAINING A POLYMER SOLUBLh ~ `
I . IN THE ORGANIC PHASE COMPRISING ASSOCIATIVE FUNCTIONAL GROUPS -`

¦ ~he invention relates to emulsion explosive ¦ compositions having a discontinuous phase comprising an ¦ 5 oxygen-releasing salt and a continuous liquid organic phase :~
and in particular to emulsion explosives compositions .
containing an oil-soluble polymer having associative groups. :~
Emulsion explosive compositions have been widely ~ `:
' accepted in the explosives industry because of their j 10 excellent explosive properties and ease of handling. The emulsion explosive compositions now in common use in the industry are of the water-in-oil type first disclosed by Bluhm in US Patent No. 3 447 978 and comprise as components~
(a) a discontinuous aqueous phase oomprising ; ~ ;

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discrete droplets of an aqueous ~olution of inorganic oxygen- releasing 8a.t8;

(b) a con~inuous water-immi~cible organic phase throughout which the droplet~ are dispersed; and i (c) an emulsifier which forms an emulsion of the droplets of oxidizer salt solution throughout the continuous organic phase.

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10 the oxidizer phase of the emulsion may be ~ -! eliminated or reduced to a low level, for example, to less than 4% by weight of the total emulsion composition. Such compositions are conveniently referred to as melt-in-oil or melt-in-fuel emulsion explosives and have been described, for example, in US Patent 4 248 644.
The term ~emulsion explosive" i~ used herein to embrace compositions of both the `~
water-in-oil and the melt-in-oil types. .`~
Emulsion explosives may be handled in bulk and are easily loaded into boreholes for ;~
large-scale blasting operations. A particular 1 problem however arises where boreholes contain ¦ water, for example, after rain. In such cases, `~
and in particular where boreholes become ~-~ completely or partially filled with water, the -~
explosive performance of emulsion explosives is severely reduced. This is a particular problem when using blends of emulsion explosive and a ~"~ 30 solid ad~uvant such as ammonium nitrate prills or :~
ANFO (Ammonium nitrate-fuel oil).

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Indeed, in many cases it i~ difficult tn detonate an emulsion explosive charge which has been loaded into a borehole containing water.
Due to these problems it has generally ~5 been the practice to drain water from a ~orehole -,before loading the explosive. This is both time consuming and la~our in~ensive.
If emulsion explosives are carefully ]oaded into the bsttom of a borehole via a hose, it is sometimes possible to displace water from the bore-hole. However, this again is a time consuming procedure and unsatisactory for deep boreholes.
We have now developed an emulsion explosive composition which i5 highly elastic and which may be loaded into wet boreholes without using such procedures.
Further advan~ages of the composition of ~9, the present invention will become eviden~ on considering the physical properties of the emulsion explo~ive composition.
Accordingly we provide an emul~ion explosive composition comprising a ~- -discontinuous phase comprising at least one oxygen-releasing salt; a continuous organic phase; an emulsifying agent; and at least one polymer soluble in the organic phase and wherein the polymer comprises associative functional groups.
Generally the associative functional groups axe polar groups capable of entering into 1 specific a~sociation with o~her associative `~ groups.
~ Examples of associative functional group ~ ;
`~35 may be æelected from a group of s ionmer~c ~functional groups; functional group~ which are ''. ,:

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capable of protolytic reaction~; and groups capable fonming hydrcgen bond~.
Examples of functional groups capable of association through hydrogen bond formation may be selected from ~he group consis~ing of hydroxyl, carboxyl and carboxamide functional groups.
Examples of ionomeric functional groups include those ~elected from the groups o salts of sulphonic and carboxylic acids such as metal and ammonium ion salts thereof, and guaternary ~ `
ammonium salts.
Example~ of groups capable of undergoing protolytic reaction include acid group~ ~uch as c rboxylic, sulphonic and phosphoric acid groups and basic groups such as nitrogen-containing ~ basic groups.
`, Examples of nitrogen-containing basic groups may be chosen from the groups of formula I
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~ R
-N
b~R2 ..

where Rl and R2 may be aryl, aralkyl,alkyl cycloalkyl or hydrogen and R and R2 may together form a S or 5 membered heteocyclic ring by a linking group of 4 ~r 5 members; and nitrogen containing heteroaromatic group such as pyridyl, picolinyl, quinolinyl, `
i~oquinolinyl and quinoxalinyl groups and the salts thereof. Preferred acid and basic groups I include the carboxylic acid group, sulphonic acid I group and pyridyl group.

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Examples of the group of formula I
wherein Rl and R2 form a heterocycl~ include pyrazolinyl~ pyrrolidinyl, peperazinyl and morpholinyl.
The said polymer may comprise more than ' one type o~ functional group. For example ~aid 1 polymer may comprise a plurality of differ2nt monomers capable of undergoing dipole-dipole ' interaction or protolytic reaction with one -l 10 another.
Polymers suitable for use in preparation of compositions of the invention may be prepared by conventional polymerization techniques.
Suitable polymer~ may be prepared by addition polymerization reactions using at least one main monoethylenically unsaturated monomer and at ~-~
least one associative monomer comprising a functional group chosen from associative functional groups as hereinbefore described, and grQups capable of conversion to said associative functional groups.
Examples of main monoethylenically unsaturated monomers (hereinafter referred to as main monomer) may be selected from the group consisting of: alkenes, preferably compri~ing from 2 to 6 carbon atoms such as ethylene and propylene; higher alkyl acryla~es and methacrylate~, in which the alkyl group contains from 4 to 18 carbon atoms, for example 2-ethyl hexylacrylate, stearyl methacrylate and lauryl 30 methacrylate; styrenes; alkyl styrenes in which the alkyl group contains from 1 to 12 carbon at~ms, for example tertiarybutyl s~yrene; and vinyl esters of fatty acids, such as vinyl stearate.
Particularly preferred main monomers are -~
i! ~ lauryl methacrylate, styrene and tert~
butylstyrene.

`1 :, 13~33~3 Examples of as~ociative monomers may be chosen from the groups consi~in~ of:
vinyl substi~uted nitrogen containing heteroaromatic compounds such as vinyl pyridines, vinylpicolines, vinyl quinolines, vinylisoquinolines and vinyl quinoxalines, ~
hydroxy~Cl to C6)alkyl acrylates and ~`
~ethacrylates, such as hydroxyethyl acrylate and hydroxy propyl m~thacrylate; acrylic acid, methacrylic acid and their metal or amine salts;
acrylamide; methacrylamide; acids selected from the group of styrene sulfonic acid, vinyl sulfonic acid, 2-acrylamides, propane sulfonic acid, acrylic acid, methacrylic acid; and the metal salts of these acids; halide salts o quaternary ammonium compounds selected from the group consisting of dimethylammonium methacrylate, diethylammonium ethyl-methacrylate;
diethylammonium ethyl-methacrylate; and precursors of these monomer~. Particularly preferred associative monomers are methacrylic i acid and metal and amine salts thereof, and vinylpyridines such as 2-vinylpyridine and 4-vinylpyridine.
Where the associative monomer comprises an associative grollp precursor, the precursor will be capable of conversion to an associative group followinq polymerization.
~ For example, diene~ such a3 norbornene '~ 30 and butadiene may be used in the preparations of j polymers, and the monomeric unit~ derived therefrom may be converted to sulfonic acids and thence to salts of sulfonic acid~ by procedures known to those ln the art.

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Emulsion polymerization is a particularly convenient technique for preparation o~ copolymers for use in ~he present composition However, the method of preparation i~ not S narrowly critical and the skilled artisan will be well acquainted with a wide variety of techniques for preparation of suitable polymers.
The polymers can conveniently b~
obtained by aqueous emulsion copolymerisation of the constituent monomers employing if necessary a minor proportion of a water-miscible organic co-solvent, such as acetone, in order to enhance the solubility of the monomer mixture in the aqueous continuous phase (the main monomers described above will inherently have very low solubilities in water and a measurabl~ degree of -solubility in the continuous phase is necessary if the polymerisation i8 to proceed at an acceptable rate). The polymerisation is generally carried out at a temperature in the range 0 - 70C, preferably 10 - 60C, in an inert j gas atmosphexe and in ~he presence of a water-soluble free radical initiator sy~tem, such I as ammonium persulphate or potassium persulphate ¦ 25 in combination with sodium dithionite optimally, sodium sulphite, sodium thio~ulphate or ascorbic acid. There may be added to the polymeri~ation ;
mixture water-soluble ~urfactants such as sodium ~;
dodecylbenzenesulphonate, ~odium dioctylsulpho~
succinate, sodium lauryl sulphate or salts of sulphated nonylphenol-ethylene oxide condensates.
The amount of initiator (or initiator I combination) used may typically lie in the range ¦ 0.05% to 1%, and the amount of ~urfactant in the 1 35 range 1% to 15%, based on the weight of the . ~.

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monomer mixture. The polymerisation may be effected by a "one-shot" procedure, in which all the monomer required is introduced into the reaction mixture at once, or by a "seed and feed"
procedure in which a small proportion of the total monomer mixture is polymeri~ed initially to form a "seed" polymer dispPrsion and the remainder of the monomer is then added gradually.
Chain transfer a~ent , such as n-octyl mercaptan, dodecyl mercaptan or chloroform, may also be added during the course of the polymerisation, especially in the later stages when more than 75%
of the monomer has been polymerised, in order to regulate the formation of the pol~m~r.
Typically, the polymers are prepared using 0.001 to 30~ associative monomer by weight of total monomer and preferably 0.01 to 20% w/w.
Typically, the total amount of said polymer will comprise in the range of 0.001 to 10% by wei~ht of the emulsion composition.
` However, we have found that particularly good 3 results are obtained by using in the ranqe of 0.01 to 2~ of the total emulsion composition.
~, Generally, the amount of polymer will be in the range of 0.001 to 20% w/w based on the organic phase and preferably in the range 0.1 to 10%.
However, higher or lower quantitie~ may be used if desired, the amount of polymer being determined without undue experimentation based on the required properties of the emul~ion.
`` As hereinbefore stated the polymer is -~
soluble in the organic phase. Generally, the polymer will be sol~bla in the org~nic phase at the polymer~organic phase weight ratio to be u6ed in the emulsion explo~ive.

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g Hence the polymer will generally be soluble in the organic phase at a concentration of at least 0.001% w/w and preferably at least O . 1 96 w/w .
One polymer particularly useful for the preparation of composition of the invention is a polymer of styrene, lauryl methacrylate and methacrylic acid.
An example of such a polymer may ~e derived by emul~ion polymPrization from a mixture of 10-80% w/w styrene, 10-80~ w/w lauryl methacrylate and 0.1-10% w/w methacrylic acid. A
particularly preferred compo ition compri~es 50-60~ lauryl methacrylate, 40-50% styrene and 1-4~ methacrylic acid.
As hereinbefore discussed, the emulsion explosive compositions of the present invention have advantages over conventional explosives, making them more suitable for loading in wet boreholes.
Without wishing to be bound by theory, we believe that the better wet borehole perfoxmance of the emul~ions of the invention may -~
be due to their elastic and cohe~ive nature.
Unlike conventional emulsion explo~ives which tend to break up when loaded into water, the ;~
~ emulsion~ of the present invention pa~s easily I ~hrough water. The cohesive properties and ~ -resiliencQ al~o make the emulsion explosive composition particularly useful in packaged ; products.
Emulsion explo~ive~ cf the invention typically have an elastic modulus in the range 100-1000 Pa at 20C. Typic~lly, the vi~c08ity is in the range 120,000 to 800,000 cp at 20C.

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` - 10 -The advantage~ of the emulsion explosive compositions are particularly apparent when the polymer has an average weight molecular weight of at least 1 x 105. Preferably the polymer has an average molecular weight in the range 5 X 105 to 1 X 107, more pxeferably 1 x 106 to 1 ~ 107. This is particularly surprising as it wa~ expected ~hat the bulk of high molecular weight polymer molecules may disrupt the stability of an emulsion explosive.
For example, in ~he case of water-in-oil emulsion explosives, it i9i generally ~elieved tha~ droplets of oxidizer solution in an emulsion i explosive are separated by bilayars of oil phase which are 5 to 20 nm thick, hence bul~y polymer molecules of molecular weight 1 x 106 and higher ; that are typically 100 to 200 nm in diameter were not expected to be compatible with an emulsion t explosive.
Suitable oxygen-releasing salts for use in the discontinuous phase component of the ` composition of the present invention include the ;¦ alkali and alkaline earth metal nitrate~
Jl chlorate~ and perchlorates, ammonium nitrate, `~ 25 ammonium chlorate, ammonium perchlorate and ; . .
mixtures thereof. The preferred oxygen-releasing `~ ~alts include ammonium nitrate, ~odium nitrate and calcium nitrste. More preferably, the oxygen-releasing salt comprises ammonium n~trate or a mixture of ammonium nitrate and sodium or calcium nitrates.
Typically, the oxygen-releasing ~alt ~ component of the composition~ of the present -¦ ` invention comprise~ from 45 to 95~ and preferably -~
35 from 60 to 90% by weigh~ of the tot~l ~

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~ 33~3~3 composition. In compo3itions wherein the oxygen-releasing salt comprises a mixture of ammonium nitrate and s~dium nitrate t the preferred composition range for such a blend is from 5 to 80 parts of sodium nitrate for every 100 parts of ammonium nitrate. Therefor,e,, in the preferred compositions of the present invention, the oxygen-releasing salt component comprises from 45 to 90~, by weight (of the total composition) ammonium, nitrate from 0 to 40% b~
weight (of the total composition) sodium or calcium nitrates.
The discontinuous phase may be entirely devoid of water, in the case of a melt-in-oil emulsion or may contain water in the case of a water-in-oil ~mulsion. In the latter case, the amount of water employed in the compositions of ;~
:~ the present invention is typically in the range of from 1 to 30~, by weight of the total composition, Preferably the amount employed is from 5 to 25%, and more preferably from 6 to 20%, by weight of the total compc,sition. ~`-The organic phase component of the `~
composition of the present invention comprises the continuous "oil" phase of the emulsion explosive an~ is 8 fuel. P~eferably the organic phase is water-immiscib~le. Suitable organic fuels include aliphatic, alicyclic and aromatic compounds and mixtuxe~ thereof which are in the -~
liquid state at the formulation temperature.
Suitable orqanic fuel~ may be chosen from fuel oil, diesel oil, distillate, kero~ene, naphtha, waxes, (eg. microcrystalline wax), paraffin oil~2, benzene, toluene, xylenes, aEphalti~ materials, , .

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polymeric oil~ such ~s the low molecular welght polymers of olefins, animal oils, fish o il8, and other mineral, hydrocarbon or fatty oils, and mixture~ ~hereof. Preferred organic fuels are liquid hydrocarbons generally referred tl~ as petroleum di~tillates ~uch aR gasoline, kerosene, fuel oils and paraffin oils.
Typically, the organic fuel or continuous phase of the emulsion explosive composition of the present invention compri~es from 2 to 15% by weight and preferably 3 to lO~
by weight of the total composition.
The emulsifying agent component of the composition of the present invention may be chosen from the wide range of emulsifying agents -~
15 known in the art for the preparation of emulsion `~
explosive compositions. Examples of ~uch emulsifying agents include alcohol alkoxylate~
phenol alkoxylates, poly(oxyalkylene) glycol~
poly(oxyalkylene) fat~y acid esters, amine 20 alkoxylates, fatty acid esters of sorbitol and -glycerol, fatty acid salts, ~orbitan esters, poly(oxyalkylene) ~orbitan esters, fatty amine ...
alkoxylhtes, poly(oxyalkylene) glycol esters, ~
fatty acid amides, fat~y acid amide alkoxylates, fatty amines, quaternary amines, alkylo~azolines, I alkenyloxa201ines, imidazolines, alkyl~
sulfonates, alkanoylsulfonates, allkylsulfo-succinates, alkylphosphates, alkenylphosphate~
phosphate esters, lecithin, copolymers of ~:
30 poly(oxyalkylene~ glycol~ and poly(12-hydroxy- :
stearic)acidl polyalkylene succinic acid and i derivative~ thereof, and mixture~ thereof. Among ~ :~
~ the preferred emulsifying agent~ are the 2-alkyl- :~

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and 2-alkenyl-4,4'-bi~ (hydroxymethyl) oxa~oline, the fatty acid esters of sorbi~ol, lecithin, copolymers of poly(oxyalkylen~!) glycols and poly(12-hydroxystearic acid), and mix~ures thereof, and particularly sorbitan mono-oleate, sorbitan sesquioleate, 2-oleyl- 4,4'-bi~
(hydroxymethyl) oxazoline, mixture of ~orbitan sesquioleate, lecithin and a copolymer of poly(oxyalkylene glycol and poly 10 (12-hydroxystearic acid~, polyisobutylene ~-succinic acid and derivatives thereof, and mixtures thereof.
Typically, the emul~ifying agent component of the composition of ~he present lS invention comprises up to 5% by weight of the - total composition. Higher proportions of the emulsifying agent may be used and may serve as a supplemental fuel for the composition but in ~eneral it is not necessary to add more than 5%
by weight of emulsifyinq agent to achieve the desired effect. One of the advantages of the ``~
compositions of the present inven ion is that ~, stable emulsions can be formed using relatively low levels of emulsifying agent, and for reasons of economy it is preferable to keep to amount of emulsifying agent in the ranse from 0.1 to 2.0%
by weight of the total composition.
If desired, other optional fuel materials, hereinafter referred to as secondary fuels, may be incorporated into the compositions of the present invention in addition to the water-immiscible organic fuel phase. Examples of such secondary fuels include finely- divided solids, and water-miscible organic liguid~ which can be used to partially replace water as a , :' " '' ~.
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- ~4 -solvent for the oxygen-releasing salts or to extend the aqueous solvent for ~he oxygen-releasing salts. Examples of solid secondary fuels include finely divided materials such as: sulfur; a:lumin~m; and carbonaceous materials such as gilsonite, comminuted coke or charcoal, carbon black, resin acids such as abietic acid, sugar~ such as glucose or dextrQse ~ :
and other vegetable products such as staxch, nut ::
meal, grain meal and wvod pulp. Examples of water-miscible organic liquids include alcohols such as methanol, glycol3 such as ethylene glycol, amides such as formamide and amines such as methylamine.
Typically, the optional secondary fuel component of the composition3 of the present invention comprise from 0 to 30% by weight of the ~ :
total composition.
It lies within the in~ention that there may also be incorporated into the emulsion explosive compositions hereinbefore described ~ other substances or mixtures of substances which i are oxygen-releasing salts or which are themselves suitable as explosiv~ materials. As 2 typical example of such a modified emulsion explosive composition, reference is made to compositions wherein there i8 added to and mixed with an emulsion explosive composition as hereinbefore described up to 90~ w/w of a solid oxidizing salt such as ammonium nitrate or an explosive composition compriaing a mixture of a solid oxidizing salt such as Emmonium nitrate and fuel oil and commonly ref?srred to by those skilled in the art as "An~?on. The compositions i ~3~9 ~

of "Anfo" are w211 known and have been de~cribed at length in the literature relating to explosives.
Mix~ures of solid ammonium nitrate or ; 5 "Anfo" a-nd the emulsion explosive of the -; invention are suited to use in wet bore holes and ~`~
water con~aining bore hole~. Mixtures of "Anfo"
~or solid ammonium nitra~e) and conventional emulsion explosive generally gi~e poor performance when loaded into bore holes containing water. The mixture tends to breaX up on impact with water and this tends to result in the dissolution of the ammonium nitrate. In contrast, mixture3 of "Anfo" with the emulsion lS explosive of the present invention may be used in bore holes containing water without ~ignificant loss of performance.
Accordingly there i~ provided an explosive composition comprising a emul~ion as hereinbefore described and up to 90% w/w of a composition comprising an ammon~um nitrate fuel oil mixture.
Typically, the proportion of ammonium nitrate or "AnfoN in such compositions will be in 25 the range 20-80% w/w. -~
It also lies within the invention to have as a further explosive component of the composition well known explosive material~
comprising one or more of, for example, trinitrotoluene, nitroglycerine or pentaerythritol tetranitrate.
`j Accordingly there i~ provided an ~ explosive composition comprising as a first '1 component an emulsion explosive compo~itlon as ~-`! 35 hereinbefore described and as a ~econd component an amount of material which 18 an oxidizing salt or which i~ in it3 own riqht an explo~iYe material.

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Generally it i8 not necessary to use thickening agents in the di3continuous phase of the present composition as the amount of polymer may be varied according to the properties desired. However, if desired, the discontinuous phase of the compo3itions of the pre~ent invention may comprise thickening agents which ~-optionally may be cross-linked. The thickening agents, when used in the compositions of the present invention, are suitably polymeric materials, especially gum materials typified by the galactomannan gums such as locust bean gum or guar gum or derivatives thereof ~iuch as hydroxypropyl guar gum. Other useful but less preferred gums are the so-called biopolymeric gums such as the heteropolysaccharide~ prepared by the microbial transformation of carbohydrate material, for example the treatment of glucose ` with a plant pathogen of the genus Xanthomonas typified by Xanthomonas camPestris.
rypically~ where used, the optional ~, thickening agent component of the compositions of ; the present invention comprises from 0 to 2% by weight of the total composition.
As indicated above, when used in the ~ compositions of the present invention, the i thickening agent optionally may be cross-linked.
~ It is convenient for this purpose to use ;~ conventional cros~i-linking agent~ such as zinc chromate or dichromate either as a separate entity or as a component of a conventional redox system such as a mixture of potas~iium dichromate i and potassium antimony tartrate.
`~ Typically, the optional cro~s-linking agent component of the compositions of the present invention comprises from 0 to 0.5~ and ~i preferably from 0 to 0.1% by weiyht of the total ~ composition.
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The emulsion explosive compositions of the presen~ invention may additionally comprise a discontinuous gaseou~ component.
The methods of incorporating a gaseous component and the enhanced sPnsitivity of emulsion explo~i~e compositions comprising such ~aseous components have been previously reported.
Typically, where used the ~aid gaseous component will be present in an amount required to reduce the density of the composition to with in the range 0.8 to 1.4 gm/cc. ;:~
The gaseous componen~ may, or example, be incorporated into the composition of the present invention as fine gas bubble~ di~persed through the composition, as hollow particles which are often xeferred to as microballoons or :
microsphere~, as porous particles, or as mixtures thereof.
A discontinuous phase of fine gas bubbles may be incorporated into the compositions of the present invention by m~chanical agitation, in~ection or bubbling the ~as through the composition, or by chemical generation of the gas in situ.
Suitable chemicals for the in situ generation of gas bubbles include peroxides, such as hydrogen peroxide, peroxide nitxates, such as sodium nitrite, nitrosoamines, such as N, ;:
N'-dinitrosopentamethylene tetramine, alkali metal borohydrides, such as sodium borohyride, and carbonates, such as sodium carbonate.
Catalytic agent~ such as ~hiocyanate or thiourea ~ :
may be used to accelerate the decomposition of a nitrite ~assing agent. Suitable amall hollow :~
35 p~rtlcles inolude sm~ll hollow microJphere~ of , .

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glass or re~inous materials, such as phenol-formaldehyde and urea-formaldehyde.
Suitable porous materials include expanded minerals, such as perlite.
Where used, the gaseous agent is prefe~ably added during cooling, after preparation of the emulsion, and typically -~; comprises 0.05 to 50% by volume of the total -, emulsion explosive composition at ,~mbient temperature and pressure. More preferably, where ;~ used, the gaseous component is present in the range 10 to 30~ by volume of tha emulsion explosive composition and preferably the bubble size of the occluded gas is below ~00 um. More preferably,at least 50% of the gas componPnt will be in the form of bubbles or microspheres of 20 to 90 um internal diameter.
The pH of the emulsion explosive composition of the present invention i8 not narrowly critical. However, in general the pH is ; between 0 and 8, preferably between 0.5 and 6.
The emulsion explosive composition of the present invention may be prepared by a number ~ of methods.
f 25 The polymer may be mixed with the oil phase before preparation of the emulsion.
Alternatively, it may be more convenient to prepare the emulsion composition of the invention by mixing o~ a composition comprising at least one polymer with an emulsion explosive composition comprising: a discontinuous phase comprising at least one oxygen releasing salt; a continuous organic phase; and an emulsifying agent.

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If desired, the polymer may be added using both methods, that is adding th~ polymer to the oil phase ~efore preparation of ~e emulsion and al~o to the emulsion once prepared.
When a composition comprising the polymer is added to the prepared emulsion, the polymer may, for example, be in the form of a solid such as a powder~ a solution in a suitable solvent such as a hydrocarbon solvent or a3 an aqueous dispersion.
i 10 Aqueous dispersions of polymer may be prepared by methods well known ~o those skilled in the art. For example, ~uch a dispersion may be formed by mixing a fine powder of polymer with an aqueous composition in the presence of a surfactant.
In a particularly preferred embodiment of the process~of the invention we therefore provide a process comprising mixing an aqueous dispersion of said polymer with an explosive composition comprising (a) an emulsion explosive ~ comprising a discontinuous aqueous phase 3 comprising an oxygen releasing salt, a continuous ~3 organic phase and an emulsifying agent and optionally ~b) solid ammonium nitrate or a mixture of solid ammonium nitrate and fuel oil.
1 Generally, the composition is mixed for a period ¦ following ~dditive of the polymer so as to facilitate dispersion within the ~nulsion explosive.
One preferred method of preparing suitable polymers involves an em~lsion polymerization technique which produces a latex `~
of the product (i.e., an aqueous di~persion of i small polymer particles). We have found it to be ¦ 35 particularly convenient in many instances to use such compo~ition in preparation of the emulsion `~`~
xplosive compo~ition of preseDt invention ...~''-~' ~33~3~`~3 In an embodiment of the invention there is thus provided a process for the preparation of an emulsion explosive composition, the process comprising: -dissolving said oxygen-relea ing salt in water at a temperature above the fudge point of the salt æolution, preferably at a temperature in the range of 25 to 110C, to give an aqueous salt ~olution;

optionally mixing said polymer with said water immiscible organic phase;
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combining said ~alt solution, said water-immiscible organic phase, said water-in-oil emulsifying agent. `
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Mixing until the emulsion is uniform and if said polymer haæ not been added, adding a ~aid polymer.

The invention i8 now demonstrated by but in no way limited to the following examples in 20 which all proportions are on a weight basis ;~
unless otherwise specified.

Example 1 A high molecular weight (average molecular weight in excess of 1 x 1o6j copolymer of tert-butyI styrene and 4-vinyl pyridine~(97s3 by weiqht) was prepared by emul~ion -~
polymerization.

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. ~ ., ~ 33~3 Emulsion Polvmerization ~ethod - ~pre~aration of polymer latex) The surfactant AEROSOL OT (AEROSOL ~8 a trade mark~ ~available from American Cyanamid), (0.3 g) and initiator ammonium persulf~te~ (0.10 g) were dissolved in acetone (10.0 g) and water (50.0 g) the monomer3 (tert-butyl styrene, and 4-vinylpyridine; 20 g) were added, and the mixture emulsified by ~tirring. The mixture wa~
flushed with nitrogen ~or ten minutes, sealed, and the tempera~ure raised to 50C and mainta~ned at that temperature for 24 hour~, w1th gentle stirring. The re3ulting product was a latex of polymer. The polymer was fvund to have an ~``
average molular wei~ht of approx. 1.19 x 106 g mol 1. Powder To prepare the polymer a~ a , powder a ~mall amount of latex ~10 g) wa~ added f' dropwise to a large excess of methanol (100 ~3, and the polymer isolated by filtration. The -~ -polymer was dried in air and ground to a flne i ` powder.
i Examples 2 and 3 and ComParati~e ~xamPle A

These example~ demo~strata the ~ffect on the viscosity o~ an emulfiion ~xplosive composition of the addition of a polymQr powdor prepared according to Example 1.

Example 2 A diesel solut~on for use a8 the orga~ic phase wa~ prepar~d by dis~olving copolymer powder ~ 30 prepar~d according to Example 1 ln di~el o~l ~t `~' a tempsrature of 80C to g~ve ~ concentration of ¦ 1% w~w o~ d~esel 801ut~on. `

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An emulslon compo~tion wa~ ~hen prepared u31ng ~he ~ollowing component~
Part~ w,w Ammonium nitrate (chemically pure~84.06 Calcium n~trate 75,02 5 distilled w~ter 25.30 die~el solution (1~ w/w copolymer)13.02 emulsifier - sorbitan monooleate 2.60 The method used was as followss The a~monium nitrate and calcium nitrate were dissolved in the water at ~ temperature of about 80~C to give the oxidizer phase. The o~idizer phase was combined with a ~ixture of the diesel solution and emul3ifier and the resulting mixture - was stirred rapidly to form an emulsion. ` ~:

Example 3 The procedure of Example 2 wa~ repeated except that the diesel ~olution wa3 prepase~
using 2~ w/w of copolymer prepared according to , Example 1.

ComParativ~ Example A
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The procedure of Example 2 wa~ repeated ~' except that copolymer was not u8ed in th~ or~anic phase. ;~

The viscoslt~e~ of tha e~ulsions of Example~ 2, 3 and Comparati~Q Example A were measured at rocm temperature ~20&) with a ~R~OKFIELD*instr~ment using spindle ~7 on speed 5 rpm and the re~ult~
are shown ln th~ ~able 1 ~elow. ~-* Trade Mark ~ .

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Copolymer Vi~co~ity :~ concen~ration (cp) , (~ w~w of -i 5 orqanic phase~
~, ,.
Comparat~ve Exsmple A/ - 48,00Q
Example 2 1 75,200 :~
Exampl2 3 2 122,400 i ExamPle 4 and Com~arative Example B

This example demonstrate3 a method of `, preparation of an emul~on of the invention by i::~
addition of a polymer powder to a preformed emulsion.
An emulsion having the following components was prepared according to E~ample 2, ~i the orgsnic phase not containing dissolved ~ polymer. . ~ `
t` Prilled ammonium nitrate (~Nitropril*") 84.06 :~:
Calcium nitrate 75.02 . 20 Distilled water 25.30 `~ Distillate oil 13.42 Emulsifier ~ 2.60 :.`
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`~ * The emulsifier was ~ 1s1 ~olar condensate of ::
`~ poly(i~obutylene) ~uccinic anhydride and 25 ethanolamine and had an average molecular weig~t -in the ran~e of 800 to 1200. `~
, , . . ~ .:
A sample of the compo~t~on was set a~ide for cQmparison (Compara~ive Example B~
* NITROPRIL is ~ trade mark. .
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-- 2f~ --To ~ sample of the prep~rfed emulsion (200 g) at : 80C wa~ added polymer powder (0.24 g, 2~ w/w on dies~!l) prepared according to Example 1. ~he S compG~ition wa~ hea~ed at 80 for four hours with occasional ~tirring, then allowed to cool. Th~
compo3ition was stored at room temperature overnight.

Copolymer Yiscosity % w/w diesel (cp) Comparative Example B 091,400 Example 4 2~ 24~,800 Exam~les 5 to 7 and ComDarative ExamPles C and D
:
.~ 15 The following example~ demonstrate thf highly viiscoela~tic nature of the explosive~ of the invention.
~ COmDaratiVe ExamPle C

An emulsion compo~itio~ having the following component~ was prepared according to Example 2, the or~anic phase being free of polymer.
Parts w/w Chemically pure ammonium nitrate 84.06 , 25 Calcium nitrate ~5.02 ; :~
Di~tilled water 25.30 ~ -Dist~llate oil 13.02 .
Emulslfier ~ 2.60 Ihe emulslfier wa8 a 1~1 mo~ar co~den~ate of '!~'"
poly(isobutylene)succinlc anhydride And ethanolamlne and h~d ~n ~verage ~olecular welght in the range 800 to 1200.

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A sample of ~mulslon was set ~s~de for comp~rison and the bulk of the emulsion was used in prepar~t~on of the following compo6itlon8.

ExamDles 5 t~ ?

S To three samples of emulsion prepare~ :
above were added polymer ~atexes prepared ~.
according to the proce~ure of example 1 using the monomer compositions shown in Table 3 below (numbers in brackets ~how the proportion of each monomer based on the total monomer mposition). The average molecular weight of polymers used ~n Examples 6 and 7 waQ measured and found to be 1.23 x 166 ~ mol~l for example 6 ~:~
and 0.82 x 106 g mol 1 for example 7.
, 15 In each case ~he appropriate latex was ; added to the emulsion to give a polymer concentration of approx. 6~ w/w on the orqanic phase and the latex was thoroughly mixed with the emuls~on.

20 Comparative Exam~le D ~ ~`

An emulsion explosive composition wa~
prepared using the above procedure except that . .
~, the polymer added wa~ a polymer of tert-butyl ~.-styrene prepsred accordinq to Example 1 ~the associative monomer ~4-vinyl pyridine) Wa8 ! omitt~d1.
~ The visco~ity of the emulsion i compositions was mea ured at room temperature u~ing a BXOOXFIELD instrument spLndle ~7 at 8peed 5.
1 The yield stresg ~nd el~stic modulu~ of :~, th2 compo8~tion8 wa8 me~sured u~ing ~ BOHLIN *
Rheometer.
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. * Elonqation i~ a comparative measure of -, ~iscoelasticity of the emul~ion , compo~itions and was determined using ! the following method:-A spatula havj.ng ~ 1 cm wid~h blade was inserted into a bulk sample of emul~ion at an angle of about 45 to the surface ~ ~
to a depth of about 1 cm. :` :-The spatula wa~ rai~ed vertically from the emulsion at a rate of about 1 cm S 1 ~ :~
until the thread of emul~ion between the :~
~ spatula and bulk sample broke or became i less than 1 mm in thickness. The h0ight of the spatula above the bulk emul~ion ~`
was measured at this ~tage.

Composit~ons of the invention typically have an elongation in the range 2 to 30 cm (preferably 4 to 20 cm).

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- 2~ -~xamPle~ 8 ~o 10 and comParatiye Example ~

These examples demonstrat~ the advantage of using explo~ivec~ of the present inven~ion when loading into w~t boreholes.

Comparative Exam~e E

An emulsion explo3ive prepared according ~' to Comparative Example C (7.5 kg) was mi~ed with ANFO" (ammonium nitrate fuel oil mixture) (7.5 kg)t The mixture was gasse~ usiny an 1~ in-situ nitrite ga~sing agent.
.~ .
~ ExamPle 8 , :
An amulsion explo~iv~ prepared aceording to Comparative Example C wa~ (7.5 Xg) was throughly mixed with polymer latex (37.5 g latex containing ~.38 g of ~polymer) to ~ive a polymer concentration of 0.13~ w/w on total emul~ion.
This emulsion mixture ~as combined and mixed with 7.5 kg of "ANFO" and the compo~ition was gass~d using an in-situ nitrite gassing agent.

Exam~le 9 , :
An emulsion~ANFO mix was prepared according to Example 8 axcept that ?5 g o~ latex 18.75 g ~polymex was add~d.
~' * The polymer lHtex UQed in ~xample3 ~ and 9 wa,~
prepared according to th~ procedure of ~x,ampl~ 1 '~ u3ing the monomer~ styrene (47~ uryl m~thacrylate ~50%) ~nd methacrylic acid S3~) lpercenta~a~ ba8~d on w/w of total monomerl ~ i .

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Example 10 An emul~ion~ANF0 mix wa~ preparedaccording to Example 8 except that the quantityof Latex was ad~u~ted to provide a polymer concentration of 0.5~ w~w on total emulsion prior , to addition of ANF0.

t ~he performance of the explosives prepared in Examples ~, 9 and Comparative Example E on loading into wet borehole~ wa~
tested using the followinq procedure~
The explosive sample wa~ dropped 3 metres into water 2 metre~ deep. ~he explosive was allowed to settle and was ~hen removed from ~! the water. After 2 hour~ the total detonation energy of the explosive wa~ tested.

't Re~ults of the te~ts are shown ~n $a~1e 4.

; TABL~ 4 J ;
Example No. Tests Polymer Energy . conc. % w/w ~J Xg-l of emulsion CE E 2 0.38 + ~-8 3 0.13 1.09 +
9 2 0.26 1.12 +
2 0.50 1.50 The above results clenrly ~how the uperiority in performance of the co~po~itions of the pre3ent invention over corre~ponding ;i .
~t compositions devoid of polymer.

Claims (22)

1. An emulsion explosive composition as hereinabove defined comprising a discontinuous phase comprising at least one oxygen releasing salt; and continuous organic phase; and emulsifying agent; and at least one polymer soluble in the organic phase and wherein the polymer comprises associative functional groups selected from the group consisting of ionomeric functional groups, functional groups which are capable of protolytic reactions and groups capable of forming hydrogen bonds.

2. An emulsion explosive composition according to claim 1 wherein said associative functional groups are selected from one or more of the members of the group consisting of carboxylic acid group, sulphonic acid group, phosphoric acid group, nitrogen containing basic groups of formula I

I
wherein R1 and R2 are independently selected from aryl, aralkyl, alkyl, cycloalkyl and hydrogen and R1 and R2 may together form a 5 or 6 membered heterocycle by a linking group of 4 or 5 constituent members; and nitrogen containing heteroaromatic groups.

3. An emulsion explosive according to claim 1 wherein the polymer is a copolymer of at least one monomer selected from the group consisting of C2 to C6 alkenes, (C4 to C18 allyl) - acrylates, (C4 to C18 allyl) methacrylates, styrenes, (C1 to C18 allyl)styrenes, and vinyl esters of fatty acids with at least one comonomer selected from the group consisting of vinyl substituted nitrogen containing heteromatic compounds, hydroxy(C1 to C6 allyl) acrylates, hydroxy(C1 to C6 allyl)methacrylates, vinyl pyridines, acrylic acid, methacrylic acid, the metal and amine salts of acrylic and methacrylic acid, styrene sulphonic acid, vinyl sulfonic acid, 2-acrylamides, propane sulphonic acid, and the halide salts of quaternary ammonium compounds selected from the group consisting of dimethylammonium methacrylate and diethylammonium ethylmethacrylate.

4. An emulsion explosive composition according to claim 3 wherein said polymer is a copolymer of at least one monomer selected from the group consisting of styrene, (C1 to C6 alkyl)styrene, (C4 to C18 alkyl)acrylates and (C4 to C18 alkyl)methacrylates with at least one comonomer selected from the group consisting of vinyl pyridines, acrylic acid and methacrylic acid.

5. An emulsion explosive according to claim 3 wherein said polymer is a copolymer of 10 to 80 by weight styrene, 10-80% by weight lauryl methacrylate and 0.1 to 10% by weight methacrylic acid.

6. An emulsion explosive according to claim 3 wherein said polymer comprises in the range of 0.01 to 20% w/w, based on the total weight of said polymer, of said comonomer.

7. An emulsion explosive according to claim 1 wherein the average molecular weight of said polymer is in the range of from 5 x 105 to 1 x 107.

8. An emulsion explosive according to claim 1 wherein the average molecular weight of said polymer is in the range of from 1 X 106 to 1 X 107.

9. An emulsion explosive composition according to claim 1 comprising in the range of from 0.01 to 10% by weight of said polymer.

10. An emulsion explosive composition according to claim 9 comprising in the range of from 0.01 to 2% by weight, based on the total weight of said composition, of said polymer.

11. An emulsion explosive according to claim 1 wherein said discontinuous phase comprises an aqueous solution of said oxygen-releasing salt.

12. An emulsion explosive according to claim 1 wherein the oxygen -releasing salt component of said emulsion explosive comprises one or more of the salts selected from the group of ammonium nitrate, sodium nitrate and calcium nitrate.

13. An emulsion explosive according to claim 1 wherein the organic phase comprises a fuel selected from the group consisting of fuel oil, diesel oil, distillate, kerosene, naphtha, waxes, paraffin oils, benzene toluene, xylenes, asphaltic materials, polymers of olefins, animal oils and fish oils.

14. An emulsion explosive according to claim 1 wherein the emulsifying agent component comprises at least one emulsifying agent selected from the group consisting of alcohol alkoxylates, phenol alkoxylates, poly(oxyalkylene)glycols, (polyoxyalkylene)fatty acid esters, amine alkoxylates, fatty acid esters of sorbitol and glycerol, fatty acid salts, sorbitan esters, poly(oxyalkylene)sorbitan esters, fatty amine alkoxylates, poly(oxyalkylene) glycol esters, fatty acid amides, fatty acid amide alkoxylates, fatty amines, quaternary amines, alkoxazolines, alkenyloxazolines, imidazolines, alkyl sulfonates, alkanoylsulfonates, alkylsulfosuccinates, alkylphosphates, alkenylphosphates, phosphate esters, lecithin, polymers of poly(oxyalkylene) glycols and poly(12-hydroxystearic acid), polyisobutylene succinic acid and derivatives thereof.

15. An emulsion explosive composition according to clim 1 comprising 60 to 90% w/w of oxygen-releasing salt, 5 to 25% w/w water, 3 to 10% w/w of organic fuel, and 0.1 to 2% w/w of emulsifying agent.

16. An explosive composition mixture comprising an emulsion explosive composition according to claim 1 and further comprising in the range of from 20 to 80% w/w, based on the total weight of said mixture, of either solid ammonium nitrate or a solid ammonium nitrate/fuel oil mixture.

17. A process for preparing an emulsion explosive according to claim 1 comprising mixing a composition comprising said polymer with an explosive composition comprising an emulsion explosive comprising a discontinuous aqueous phase comprising an oxygen releasing salt, a continuous organic phase and an emulsifying agent.

18. A process according to claim 17 wherein the composition comprising said polymer is an aqueous dispersion of said polymer.

19. A process for preparing an emulsion explosive composition according to claim 1 the process comprising dissolving said oxygen releasing salt in water at a temperature in the range of from 25 to 110°C to form an aqueous salt solution; combining said salt solution said organic phase, said emulsifying agent and said polymer and mixing until a uniform emulsion is formed.

20. A process for preparing an emulsion explosive according to claim 17 wherein said composition further comprises solid ammonium nitrate.

21. A process for preparing an emulsion explosive according to claim 17 wherein said composition further comprises a mixture of solid ammonium nitrate and fuel oil.

22. A process for preparing an emulsion explosive composition according to claim 1 the process comprising dissolving said oxygen releasing salt in water at a temperature in the range of from 25 to 110°C to form an aqueous salt solution; combining said salt solution, said organic phase, said emulsifying agent, mixing until a uniform emulsion is formed and mixing said polymer with said emulsion.