Water resistance additive for particulate ammonium nitrate-fuel oil (ANFO) explosives

Abstract

The present invention provides for the use of at least one oil soluble polymer comprising linear polymethylene sequences with an average of 10 to 40 consecutive methylene groups to improve the water resistance of an explosive composition comprising particulate ammonium nitrate and a fuel oil, said linear polymethylene sequences with in average 10 to 40 consecutive methylene groups may be either in the main chain or in the side chains of the oil soluble polymer.

Claims

1. A process for improving the water resistance of a particulate ammonium nitrate fuel oil explosive, comprising the step of adding a fuel oil containing at least one oil soluble polymer, to an explosive composition comprising at least one particulate ammonium nitrate, wherein the particulate ammonium nitrate fuel oil explosive is not in the form of an emulsion and comprises less than 2 wt.-% of water, and the at least one oil soluble polymer is a copolymer (i) of ethylene and at least one vinyl ester, acrylic ester, methacrylic ester, and/or alkyl vinyl ether, wherein the copolymer (i) has linear polymethylene sequences with an average length PS(i) of 12 to 40 consecutive methylene groups, the average length PS(i) being calculated according to the formula $PS (i) = (\frac{molar content of ethylene}{molar content of comonomer}) * 2 + 1$ or a homo- or co-polymer (ii) of esters, amides, and/or imides of ethylenically unsaturated carboxylic acids, wherein the homo- or co-polymer (ii) has linear polymethylene sequences with an average length PS(ii) of 12 to 40 consecutive methylene groups, the average length PS(ii) being calculated according to the formula $PS (ii) = m_{1} .Math. \underset{i}{.Math.} w_{1 i} .Math. n_{1 i} + m_{2} .Math. \underset{j}{.Math.} w_{2 j} .Math. n_{2 j} + .Math. + m_{g} .Math. \underset{p}{.Math.} w_{gp} .Math. n_{gp}$ wherein m.sub.1, m.sub.2, . . . m.sub.g are the molar fractions of the comonomers in the polymer and the sum of the molar fractions m.sub.1 to m.sub.g=1, w.sub.1i, w.sub.2j, . . . w.sub.gp are the proportions by weight of the individual chain lengths i, j, . . . p of the alkyl radicals of the different comonomers 1 to g, and n.sub.1i, n.sub.2j, . . . n.sub.gp are the chain lengths i, j, . . . p of the alkyl radicals of the comonomers 1 to g, wherein terminating methyl groups of alkyl residues are included in the chain lengths of the alkyl residues; and wherein an amount of the at least one oil soluble polymer added to the explosive composition is 0.05 to 5.0 wt.-% of the weight of the at least one particulate ammonium nitrate in the explosive composition.

2. The process according to claim 1, wherein the at least one oil soluble polymer is a copolymer(i) of ethylene and at least one vinyl ester, acrylic ester, methacrylic ester and/or alkyl vinyl ether, wherein the copolymer (i) comprises 5 to 11 mol-% of the at least one vinyl ester, acrylic ester, methacrylic ester, and/or alkyl vinyl ether.

3. The process according to claim 2, wherein the at least one vinyl ester, acrylic ester, methacrylic ester, and/or alkyl vinyl ether has a C.sub.1 to C.sub.8 alkyl or alkenyl group.

4. The process according to claim 2, wherein the at least one oil soluble polymer is a copolymer (i) of ethylene and at least one vinyl ester according to formula (1)
CH.sub.2?CHOCOR.sup.1(1) in which R.sup.1 is a C.sub.1- to C.sub.8-alkyl.

5. The process according to claim 2, wherein the at least one oil soluble polymer is a copolymer (i) of ethylene and at least one vinyl ester selected from the group consisting of vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl hexanoate, vinyl heptanoate, vinyl octanoate, and vinyl 2-ethylhexanoate.

6. The process according to claim 2, wherein the at least one oil soluble polymer is a copolymer (i) of ethylene and at least one vinyl ether corresponding to formula (3)
CH.sub.2?CHOR.sup.4(3) in which R.sup.4 is a C.sub.1 to C.sub.8-alkyl.

7. The process according to claim 2, wherein the at least one oil soluble polymer is a copolymer (i) of ethylene and at least one ester of an ethylenically unsaturated monocarboxylic acid corresponding to formula (2) ##STR00004## in which R.sup.2 is hydrogen or methyl and R.sup.3 is a C.sub.1- to C.sub.8-alkyl.

8. The process according to claim 2, wherein the at least one oil soluble polymer is a copolymer (i) of ethylene and at least one acrylic ester or methacrylic ester selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n and isobutyl (meth)acrylate, and hexyl (meth)acrylate, octyl (meth)acrylate, 2 ethylhexyl (meth)acrylate and mixtures of these comonomers, the formulation (meth)acrylate including the respective esters of acrylic acid and methacrylic acid.

9. The process according to claim 1, wherein the at least one oil soluble polymer is a homo- or co-polymer (ii) of esters, amides, and/or imides of ethylenically unsaturated carboxylic acids, wherein the esters, amides, and/or imides have alkyl residues with an average alkyl chain length of C.sub.10-C.sub.40.

10. The process according to claim 9, wherein the at least one oil soluble polymer is a homo- or co-polymer (ii) of esters of ethylenically unsaturated carboxylic acids, wherein the homo- or co-polymer (ii) repeat structural units of formula (4) ##STR00005## wherein R.sup.5 and R.sup.6 are each independently hydrogen, phenyl or a group of the formula COOR.sup.8, R.sup.7 is hydrogen, methyl or a group of the formula CH.sub.2COOR.sup.8 and R.sup.8 is a C.sub.10- to C.sub.40-alkyl radical, with the proviso that at most, one of R.sup.5 and R.sup.6 and R.sup.7 include a carboxylic ester group COOR.sup.8.

11. The process according to claim 10, wherein the ethylenically unsaturated carboxylic acid esters are esters of ethylenically unsaturated carboxylic acids selected from the group consisting of acrylic acid, methacrylic acid, cinnamic acid, maleic acid, fumaric acid and itaconic acid.

12. The process according to claim 10, wherein R.sup.8 has 11 to 32 consecutive methylene groups.

13. The process according to claim 9, wherein the ethylenically unsaturated carboxylic acid esters are esters of alcohols, wherein the alcohol is selected from the group consisting of 1-decanol, 1-dodecanol, 1 tridecanol, isotridecanol, 1 tetradecanol, 1 hexadecanol, 1-octadecanol, eicosanol, docosanol, tetracosanol, hexacosanol and their mixtures.

14. The process according to claim 9, wherein the homo- or copolymers (ii) are homo- or copolymers of amides and/or imides of ethylenically unsaturated carboxylic acids and are obtained by reaction of homo- and copolymers of ethylenically unsaturated carboxylic acids, their anhydrides, and/or their esters with lower alcohols with 1 to 4 carbon atoms, with amines having one or, in case of amides one or two, alkyl residues with 10 to 40 consecutive methylene groups.

15. The process according to claim 14, wherein the amines are selected from the group consisting of 1-decyl amine, 1-dodecyl amine, 1 tridecyl amine, isotridecyl amine, 1 tetradecyl amine, 1-hexadecyl amine, 1 octadecyl amine, eicosyl amine, docosyl amine, tetracosyl amine, hexacosyl amine and their mixtures.

16. The process according to claim 9, wherein the at least one oil soluble polymer is a copolymer (ii) containing 10 to 95 mol % of structural units derived from esters of ethylenically unsaturated carboxylic acids.

17. The process according to claim 9, wherein the at least one oil soluble polymer is a homopolymer (ii) consisting solely of structural units derived from the ester of an ethylenically unsaturated carboxylic acids, wherein the ester contains C.sub.10-C.sub.40-alkyl radicals.

18. The process according to claim 10, wherein R.sup.5 and R.sup.6 are each hydrogen and R.sup.7 is hydrogen or methyl.

19. The process according to claim 10, wherein one of R.sup.5 and R.sup.6 is hydrogen and the other a group of the formula COOR.sup.8 and R.sup.7 is hydrogen, or wherein R.sup.5 and R6 are hydrogen and R.sup.7 is a group of the formula
CH2COOR.sup.8.

20. The process according to claim 1, wherein the at least one oil soluble polymer comprising at least one linear polymethylene sequence with an average of 10 to 40 consecutive methylene groups is a graft polymer (iii) of homo- and copolymers b) of esters, amides and/or imides of ethylenically unsaturated carboxylic acids, said esters, amides and/or imides bearing alkyl radicals with an average alkyl chain length of C.sub.10-C.sub.40 on copolymers a) of ethylene with 5 to 18 mol-% of at least one monomer selected from vinyl esters, esters of ethylenically unsaturated carboxylic acids and vinyl ethers having a C.sub.1 to C.sub.8 alkyl or alkenyl group.

21. The process according to claim 20, wherein the graft polymer (iii) contains ethylene copolymer a) and a homo-or copolymer of an ester of an ?,?-unsaturated carboxylic acid with a C.sub.10- to C.sub.40-alcohol b) in a weight ratio of 1:10 to 10:1.

22. The process according to claim 2, wherein a number average molecular weight of the copolymer (i) is between 500 and 100,-000 g/mol, as determined by Gel Permeation Chromatography using poly(styrene) standards.

23. The process according to claim 9, wherein a number average molecular weight of the homo- or copolymer (ii) is within a range from 4000 to 200,-000 g/mol, as determined by means of Gel Permeation Chromatography against poly(styrene) standards.

24. The process according to claim 1, wherein the explosive composition comprises at least one ammonium nitrate with a bulk density of between 0.6 and 0.9 g/cm.sup.3.

25. The process according to claim 1, wherein the explosive composition comprises particulate ammonium nitrate particles with an average diameter of between 0.5 and 5 mm.

26. The process according to claim 1, wherein the at least one particulate ammonium nitrate contains at least 90 wt.-% of ammonium nitrate.

27. The process according to claim 1, wherein the fuel oil is selected from the group consisting of mineral oil distillates, biofuels, synthetic fuel oils and oily liquids derived from plant and animal origin and their synthetic equivalents.

28. The process according to claim 1, wherein the fuel oil has a pour point above ?20? C.

29. The process according to claim 1, wherein the fuel oil has a pour point below +30? C.

30. The process according to claim 1, wherein the amount of the at least one oil soluble polymer added to the explosive composition is 0.1 to 5.0 wt.-% of the weight of the at least one particulate ammonium nitrate in the explosive composition.

31. The process according to claim 1, wherein at least 50 wt.-% of solid ANFO is recovered after 24 hours of exposure of solid ANFO to a water saturated substrate, a water saturated substrate being defined as a system wherein a water absorbent sponge is placed in a tray of water so that the bottom half of the sponge is immersed keeping the entire surface of the sponge damp and a paper towel is laid over the sponge to give a uniform surface and the paper towel is kept saturated with water by the sponge below.

32. The process according to claim 1, wherein the particulate ammonium nitrate fuel oil explosive is in the form of free flowing solid particles.

33. The process according to claim 1, wherein the at least one oil soluble polymer is added to the explosive composition in the form of a solution and/or dispersion of the at least ne oil soluble polymer in the fuel oil.

Description

EXAMPLES

(1) Water Resistance Tests

(2) In these examples, the water resistance is determined as the mass portion remaining after a sample of ANFO has been exposed to a water saturated substrate for 24, 48 respectively 72 hours. In the water resistance test, ANFO samples are prepared using the LDAN/Fuel ratio given in Table 4 (weight-%). The oil soluble polymers, if present, are part of the fuel component.

(3) For testing water absorbent sponges are placed in trays of water so that the bottom half of the sponges are immersed keeping the entire surface of each sponge damp. A paper towel is laid over the sponges to give a uniform surface. The paper towel is kept saturated with water by the sponges below. 10.0 g samples of ANFO are weighed into cylindrical molds sitting on temporary plastic sleeves. The molds are then placed on the saturated paper towel and the temporary bottom sleeve is removed exposing the ANFO to the damp surface. After 24, 48 respectively 72 hours storage at ambient temperature the remaining amount of ANFO is reweighed and the loss of ANFO calculated as the weight loss.

(4) TABLE-US-00001 TABLE 1 Characterization of the low density ammonium nitrate (LDAN) used: Ammonium nitrate content 99.5 wt.-% Water content 0.15 wt.-% pH (5%) solution 5.0 Oil retention >10 wt.-% Bulk Density 0.75 g/cm.sup.3

(5) TABLE-US-00002 TABLE 2 Characterization of fuel oils used for the preparation of ANFO samples FO (I) FO (II) Type Diesel Heavy Fuel Oil Cloud Point (EN 23015) ?15? C. +23? C. Pour Point (DIN ISO 3016) ?19? C. +18? C. Viscosity 4 cSt at 40? C. 650 mm.sup.2/s at 50? C. Density (15? C.) 0.845 0.860 Water content 0.006 wt.-% 0.008 wt.-%

(6) TABLE-US-00003 TABLE 3 Characterization of the polymers Polymer Characterization (PS)* P1 Copolymer of stearyl acrylate and 5% allyl polyglycol, 50% 18.0 active in xylene. The K-value determined according to Fikentscher in 5% solution on toluene was 31. P2 Ethylene-vinyl acetate copolymer (11 mol-% vinyl acetate, (i) = 17.2 an MFI(190/2, 16) of 7 g/10 minutes) grafted with behenyl (ii) = 21.2 acrylate comprising as main components 6 mol-% C.sub.18-, 18 mol-% C.sub.20-, 74 mol-% C.sub.22- and 1 mol-% C.sub.24-acrylate in a weight ratio of 4:1 as a 25% active mixture in Solvesso 200, P3 Ethylene-vinyl acetate copolymer (11 mol-% vinyl acetate, (i) = 17.2 an MFI(190/2, 16) of 7 g/10 minutes) grafted with behenyl (ii) = 21.0 acrylate comprising as main components 4 mol-% C.sub.18-, 51 mol-% C.sub.20-, 26 mol-% C.sub.22-, 14 mol-% C.sub.24- and 4 mol-% C.sub.26-acrylate in a weight ratio of 4:1, 35% active in Solvesso? 100 P4 Copolymer of maleic anhydride and C.sub.20-C.sub.24 ?-olefin 21.1 (comprising 2 mol-% C.sub.18, 44 mol-% C.sub.20, 34 mol-% C.sub.22, 17 mol-% C.sub.24, 1 mol-% C.sub.26) which had been esterified with behenyl alcohol comprising as main components 6 mol-% C.sub.18-, 18 mol-% C.sub.20-, 74 mol-% C.sub.22- and 1 mol-% C.sub.24-alcohol, as a 20 wt.-% active in Shellsol? AB. P5 Ethylene-vinyl acetate copolymer (8 mol-% vinyl acetate, an (i) = 24.0 MFI(190/2, 16) of 500 g/10 minutes) grafted with a mixture of (ii) = 19.8 alkyl acrylates comprising as main components 35 mol-% C.sub.18-, 33 mol-% C.sub.20-, 18 mol-% C.sub.22-, 10 mol-% C.sub.24- and 2 mol-% C.sub.26-acrylate in a weight ratio of 3:1, 35% active in Solvesso? 100. P6 Ethylene-vinyl acetate copolymer (11 mol-% vinyl acetate, 17.2 V.sub.140 of 250 mPas, 50% active in kerosene P7 Copolymer of ethylene and propylene with an ethylene n.a. (comp.) content of 68% and a Mw of 6000 g/mol as determined by GPC using poly(styrene) standards. P8 Ethylene-vinyl acetate copolymer (8 mol-% vinyl acetate, 24.0 V.sub.140 of 600 mPas, 50% active in kerosene P9 Ethylene-vinyl acetate copolymer (6 mol-% vinyl acetate, 32.3 V.sub.140 of 500 mPas, 50% active in kerosene P10 Ethylene-vinyl acetate copolymer (20 mol-% vinyl acetate, 9.0 (comp.) V.sub.140 of 3500 mPas, 40% active in kerosene P11 Ethylene-vinyl acetate copolymer (4 mol-% vinyl acetate, 49.0 (comp.) MFI(190/2, 16) of 135 g/10 min; 20% active in decaline P12 Poly(methylacrylate) with a Mn 12,000 g/mol determined by 1 (comp.) GPC using polystyrene standards, 30% active in acetone P13 Poly(isobutylene) with a Mn of 600,000 g/mol as determined n.a. (comp.) by GPC using polystyrene standards (corresponding to a Mv of approx. 1,200,000) *PS = average length of linear polymethylene sequence; n.a. = not applicable All polymers used were essentially water free, i.e. they contained less than 100 ppm (wt/wt) of water.
Preparation of ANFO

(7) Samples of ANFO, each about 2 kilograms, were prepared from low density ammonium nitrate (AN) miniprills characterized in table 1 and the fuel characterized in table 2 containing the polymers characterized in table 3 in the amounts given in table 4. The polymers were dissolved in the fuel oil in the concentrations given in table 4. The ANFO samples were formed by charging the dry, free-flowing ammonium nitrate miniprills to a planetary mixer to which was then added the liquid mixture containing the fuel oil containing the oil soluble polymer in order to form dry, free-flowing ANFO miniprills having the compositions set forth in Table 4 below.

(8) The improvement of water resistance was rated according to the scale Excellent>Very Good>Good>Fair>Poor

(9) TABLE-US-00004 TABLE 4 Water resistance (WR) of ANFO wt.-% of Ratio wt.-% ANFO remaining after Example Polymer FO type polymer in FO LDAN:FO 24 hours 48 hours 72 hours WR rating 1 blank FO (I) 0 94:6 5 2 1 Very poor 2 blank FO (II) 0 94:6 6 3 1 Very poor 3 P1 FO (I) 10 94:6 90 86 82 Very good 4 P2 FO (I) 10 94:6 88 72 60 Good 5 P3 FO (I) 10 94:6 96 91 86 Very good 6 P4 FO (I) 10 94:6 86 70 58 Good 7 P5 FO (I) 10 94:6 89 75 64 Good 8 P6 FO (I) 5 94:6 95 81 56 Good 9 P6 FO (I) 10 94:6 97 93 90 Excellent 10 P6 FO (II) 10 94:6 97 94 92 Excellent 11 P6 FO (I) 10 92:8 98 96 93 Excellent 13 P6 FO (I) 10 96:4 95 92 89 Excellent 14 P8 FO (I) 10 94:6 95 91 85 Very good 15 P8 FO (II) 3 92:8 96 92 76 Excellent 16 P9 FO (I) 10 94:6 93 88 81 Very good 17 P9 FO (II) 15 96:4 98 95 93 Excellent 18 (comp.) P7 FO (I) 10 94:6 62 38 30 Fair 19 (comp.) P10 FO(I) 10 94:6 65 42 36 Fair 20 (comp.) P 11 FO (I) 10 94:6 28 19 11 Poor 21 (comp.) P 12 FO (I) 10 94:6 38 29 21 Poor 22 (comp.) P 13 FO (I) 10 94:6 36 27 16 Poor
Detonation Tests

(10) In further examples, the water resistance is determined by the success of detonation as measured by Velocity of Detonation (VOD) after ANFO has been exposed to a water saturated sand for 24 hours. For the detonation test, ANFO samples are prepared using a LDAN/Fuel ratio of 94:6 (by weight-%) using fuel oil (I) as described above in the water resistance section. The oil soluble polymers, if present, are part of the fuel component.

(11) For testing, a 90 mm diameter cylinder with a height of 500 mm was formed from fly-wire mesh having a mesh size of approximately 1 mm. A 20 mm wide strip of PVC with 8 VOD cables mounted in holes drilled at 30 mm intervals was attached vertically to the side of the fly-wire. The fly-wire mesh cylinder was placed in the centre of a 30 litre plastic bucket. A length of 90 mm PVC pipe was placed inside the mesh to provide temporary support while the mesh was surrounded by 35 kg of washed Sydney sand which was saturated with 5 litres of water. A standard mass of 2.5 kg of ANFO was then poured inside the centre pipe after which the PVC pipe was removed thereby exposing the ANFO to the wet sand via the mesh. The ANFO was left exposed to the wet sand for 24 hours. After 24 hours 150 g of a Pentolite 50/50 cast booster was placed in the ANFO with the top of the initiator level with the top of the column of ANFO. The ANFO was then detonated and the VOD measured. A velocity of detonation (VOD) of at least 2400 metres per second indicates a successful detonation. The tests were made in duplicate.

(12) TABLE-US-00005 TABLE 5 Results of detonation tests wt.-% of polymer Ratio VOD Example Polymer in FO LDAN:FO [m/s] 23 (comp.) none 0 94:6 failed to detonate 24 (comp.) none 0 94:6 failed to detonate 25 P1 8 94:6 3150 26 P1 8 94:6 3100 27 P4 12 94:6 2750 28 P4 12 94:6 2850 29 P6 10 94:6 3200 30 P6 10 94:6 3350

Water resistance additive for particulate ammonium nitrate-fuel oil (ANFO) explosives

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Cpc classification

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C06B23/001

CHEMISTRY; METALLURGY

Classification Explorer

C06B23/009

CHEMISTRY; METALLURGY

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C06B31/285

CHEMISTRY; METALLURGY

International classification

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C06B23/00

CHEMISTRY; METALLURGY

Classification Explorer

C06B31/28

CHEMISTRY; METALLURGY

Abstract

Claims

Description