US3278350A - Explosive-ammonium nitrate in phenol-aldehyde resin - Google Patents

Description

United States Patent Ofifice 3,278,350 Patented Oct. 11, 1966 3,278,350 EXPLOSIVE-AMMONIUM NITRATE [N PHENOL- ALDlEI-IYDE RESIN Walter Anderson Caldwell, West Kilbride, and Vincent Davies, Salteoats, Scotland, assignors to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain No Drawing. Filed Feb. 3, 1964, Ser. No. 342,283 Claims priority, applicatgol fil'glt Britain, Feb. 11, 1963,

6 Claims. (Cl. 149-7) This invention relates to new explosive compositions of the kind comprising ammonium nitrate sensitised by a carbonaceous material. The invention also includes a process for the preparation of such explosive compounds.

It is well known that detonatable explosives can be prepared by mixing ammonium nitrate with combustible materials such as, for example, hydrocarbon oils or waxes which sensitise the normally non-explosive ammonium nitrate so that the mixture can be detonated. In general, when the combustible material is itself non-explosive, the mixed explosive requires to be initiated by a relatively large quantity of sensitive priming explosive before it will detonate. In particular, when the normal commercial grades of ammonium nitrate are used in the mixture, these explosives cannot be reliably initiated to detonation by a commercial detonator in which a small quantity of initiating and priming explosive is encapsulated in a metal tube.

According to the present invention an explosive composition comprises ammonium nitrate and a sensitising quantity of a solid thermosetting aldehyde resin. It is unnecessary for the explosive to contain sufiicient aldehyde resin to completely balance the excess oxygen of the ammonium nitrate; provided there is suflicient to sensitise the ammonium nitrate other non-explosive may be incorporated, if desired. to balance at least part of the excess oxygen and so give a more efiicient explosive. Preferably the proportion of resin should be at least 3.5 percent by weight of the ammonium nitrate.

The compositions of the invention comprising ammonium nitrate of a certain grain size are more easily initiated than compositions comprising ammonium nitrate of the same grain size and the non-explosive sensitisers used hitherto.

The explosives of the invention, being prepared from non-explosive ingredients, have the further advantage that, when stored in damp conditions with consequent leaching out of ammonium nitrate, the residual mixture does not become more sensitive, as happens with an ammonium nitrate explosive sensitised by a substantially water insoluble self-explosive sensitiser.

The aldehyde resin is conveniently one formed by condensing formaldehyde resin with urea, melamine or a phenol such as phenol, resorcinol or cresol. It is possible to prepare explosives, comprising such resins, which can be initiated by commercial detonators and which are less sensitive to impact and friction than ammonium nitrate explosives sensitised by self-explosive materials such as nitro-glycerine and trinitrotoluene.

The compositions of the invention may, if desired, contain other non-explosive ingredients of the kind commonly used in explosives, for example, oxidising salts such as potassium nitrate and combustible materials such as anthracite, aluminium or woodmeal. With some compositions the inclusion of a minor proportion of potassium nitrate or sodium nitrate renders the compositions more sensitive to initiation by a detonator.

In accordance with the process of the invention explosives are conveniently prepared by treating ammonium nitrate granules with a solution consisting of a quantity of aldehyde resin, sufiicient to sensitise the ammonium nitrate granules, dissolved in a quantity of solvent, insufficient to dissolve the ammonium nitrate granules, and drying off the solvent. The process yields a granular product, of which the granules have an outer layer containing a high proportion of aldehyde resin.

Phenol/formaldehyde resins are more soluble in alkaline solutions and in order to obtain sufficiently concentrated solutions of this resin it is advantageous to dissolve it in an alkaline solution such as, for example, aqueous sodium hydroxide. It is preferred to use an amount of solvent which is less than 10 percent by weight of the ammonium nitrate.

The solvent is conveniently removed by passing a heated 7 air stream over the granules. After removal of the solvent it is advantageous to heat the granules to above 70 C. to effect polymerisation and crosslinking of the aldehyde resin and to improve the free running properties. This has the advantageous effect of enhancing the water resistance of the explosive and rendering it more suitable for use in damp conditions.

Explosives prepared by the process of the invention from free-running granular ammonium nitrate are themselves free-running provided the solvent has been sufliciently dried off. In general, the free-running properties of the explosives which have been heated to effect further polymerisation of the resin are superior to those of the original ammonium nitrate.

The invention is further illustrated by the following examples in which all parts and percentages are by weight.

Example 1 7.5 parts of phenol/formaldehyde resin (having a molar ratio of 1 phenol to 1.4 formaldehyde units) dissolved in 5 parts of a 2 percent aqueous solution of sodium hydroxide were mixed with 92.5 parts granular ammonium nitrate. The mixture was dried by passing a stream of air at 70 C. over the mixture for 8 hours while it was agitated in a mixing machine. The moisture content of the product was 0.2 percent. The grain size of the ammonium nitrate was such that percent passed a B.S. 8 mesh sieve, 70 percent passed a B.S. 16 mesh sieve, 10 percent passed a B.S. 30 mesh sieve.

The explosive was passed through a B.S. 6 mesh sieve to break any aggregates formed and the resulting granular product was very free-running. It had a bulk density (as poured) of 0.75 g./cc. and its grain size was such that 76 percent passed a B.S. 8 mesh sieve, 16 percent passed a B.S. 16 mesh sieve, 3 percent passed a B.S. 30 mesh sieve.

An unconfined 2 /2 inch diameter canister cartridge of the product was capable of being initiated by a detonator containing 1 gram of 80/20 mercury fulminate/ potassium chlorate mixture or by one containing a base charge of 0.15 gram pentaerythritol-tetranitrate (PETN). Its velocity of detonation in this diameter was 1700 metres per second. The power of the explosive measured by a ballistic mortar was 79 percent blasting gelatine. No detonations were observed in a torpedo friction test when a 1 kilogram steel torpedo was allowed to slide freely down a surface 80 centimetres in length, inclined at 70 to the horizontal, on to a thin layer of the explosive on a steel base. Similarly no detonations were observed when a thin layer of the explosive contained between two steel surfaces was subjected to the blow from a /2 kg. hammer dropped from a height of centimetres.

The properties of the explosive prepared in this example indicated that it was suitable for use as a blasting agent both in cartridge form and in bulk.

Example 2 7.5 parts of phenol/formaldehyde resin, as used in Example 1, dissolved in 7.2 parts of a 2 percent aqueous solution of sodium hydroxide were mixed with 92.5 parts of a finer grade of ammonium nitrate than was used in Example 1. The mixture was dried by passing a stream of air at 50 C. for 80 hours over the mixture spread in a layer /2 inch thick. The moisture content of the product was 0.2%.

The grain size of the ammonium nitrate used was such that 100 percent passed a B.S. 30 mesh sieve 75 percent passed a B.S. 60 mesh sieve 30 percent passed a B.S. 100 mesh sieve 8 percent passed a B.S. 170 mesh sieve The explosive was broken down by crushing through a B.S." 16 mesh sieve. The resulting powder had a bulk density of 0.6 g./cc. and its grain size was such that 100 percent passed a B.S. 16 mesh sieve 57 percent passed a B.S. 30 mesh sieve 7 percent passed a B.S. 60 mesh sieve It was pourable but was less free-running than the product of Example 1.

A 2 /2 inch diameter cartridge was capable of being initiated by a detonator containing 0.8 gram of 80/20 mercury fulminate/ potassium chlorate mixture and its velocity of detonation was 2,200 metres per second. Its power and sensitivity to initiation by friction and impact were similar to the corresponding properties of the product of Example 1.

Example 3 10 parts of phenol/formaldehyde resin, as used in Example 1, dissolved in 9.5 parts of a 2 percent aqueous solution of sodium hydroxide were mixed with 90 parts of coarse ammonium nitrate as used in Example 1 and dried in a stream of air at 50 C. for 80 hours as described in Example 2. The product was passed through a 6 mesh B.S. sieve and its density was 0.6 g./cc. Its moisture content, grain size, sensitivity to friction and impact, quantity of initiating explosive required for initiation and velocty of detonation, were similar to those of the product of Example 1. Its power was 81% blasting gelatine.

The free-running properties of this product were slightly inferior to those of the product of Example 1 but it was improved in this respect when heated at 100 C. for 3 hours. This was believed to be due to further polymerisation of the resin.

Example 4 .15 parts of urea/formaldehyde resin (having a molar ratio of 1 urea to 1.9 formaldehyde units) dissolved in 5 parts of Water were mixed With 85 parts of granular ammonium nitrate as used in Example 1. The mixture was dried by heating in air at 32 C. for 100 hours. The moisture content of the product was 0.3 percent.

The product was passed through a B.S. 6 mesh sieve and the product had the similar grain size to the product of Example 1, and a bulk density of 0.7 g./cc.

A 2% inch diameter cartridge of the product was capable of being initiated by a detonator containing a base charge of 0.8 gram of pentaerythritoltetranitrate. The power was 77 percent blasting gelatine. Its sensitivity to initiation by friction and impact was similar to that of Example 1.

Example 5 9 parts of resorcinol/formaldehyde resin (having a molar ratio of 1 resorcinol to 1.1 formaldehyde units) disolved in 5 parts of a 0.25 percent aqueous solution of sodium hydroxide were mixed with 91 parts granular ammonium nitrate as used in Example 1 and spread inch thick on a tray in a room at about 20 C. for 72 hours. The cake was broken through a 6 mesh B.S. sieve and dried in a stream of air at 100 C. for 2 /2 hours, as described in Example 1. The product was passed through a 6 mesh B.S. sieve and its density was 0.95 g./cc. at 25 p.s.i and its grain size was such that 90 percent passed as B.S. 8 mesh sieve 47 percent passed a B.S. 16 mesh sieve 20 percent passed a B.S. 30 mesh sieve Its moisture content, sensitivity to friction and impact, quantity of initiating explosive required for initiation in an unconfined 2 /2" diameter canister cartridge and velocity of detonation were similar to those of the product of Example 1. Its power was percent blasting gelatine.

Example 6 94 percent passed a B.S. 8 mesh sieve 47 percent passed a B.S. 16 mesh sieve 24 percent passed a B.S. 30 mesh sieve The moisture content, sensitivity to friction and impact and velocity of detonation were similar to those of the products of Example 1. An unconfined 2 /2" diameter canister cartridge was capable of being initiated by a detonator With a base charge of 0.24 g. of pentaerythritoltetranitrate or by a detonator containing 2.00 g. of 80/20 mercury fulminate/ potassium chlorate mixture.

Example 7 8.5 parts of the resin as used in Example 6 dissolved in 10 parts of industrial alcohol were mixed with 83 parts of ammonium nitrate and 9.25 parts of a fine grade potassium nitrate and dried as in Example 6. The product was passed through a 6 mesh B.S. sieve and its density at 25 p.s.i. was 0.80 g./ cc. The moisture content, sensitivity to friction and impact, velocity of detonation and sieve analysis were similar to those of the product of Example 6. An unconfined 2 /2" diameter canister cartridge was capable of being initiated by a detonator containing 0.40 g. of /10 mercury fulminate/potassium chlorate mix' ture. The power was 77% blasting gelatine.

Example 8 8 parts of resin as used in Example 6 dissolved in 9.5

13.4 parts of a melamine/formaldehyde resin (having a molar ratio of 1 melamine to 4.5 formaldehyde units) dissolved in 12 parts of 50 percent aqueous alcohol were mixed with 86.6 parts of granular ammonium nitrates as used in Example 1. The mixture was dried at 90 C. for 4 hours as described in Example 1. The moisture content of the product was 1.2%. The product was passed through a B.S. 6 mesh sieve and had a bulk density of 0.79 at 25 p.s.i. and a grain size such that 90 percent passed through a B.S. 8 mesh sieve 40 percent passed through a B.S. 16 mesh sieve 10 percent passed through a B.S. 30 mesh sieve An unconfined 2 /2" diameter canister cartridge of the product was capable of being initiated by a detonator containing a base charge of 0.80 g. of pentaerythritoltetranitrate. Its velocity of detonation, its power and sensitivity to impact and friction were similar to those of the product of Example 1.

Example 4.7 parts of a phenol/formaldehyde resin (having a molar ratio of 1 phenol to 1.4 formaldehyde units) dissolved in 2.7 parts of a 1.5 percent aqueous sodium hydroxide solution was added to 86.1 parts of granular ammonium nitrate as used in Example 1 and 9.2 parts of granular aluminium. The mixture was dried at 90 C. for 4 hours as described in Example 1. The product had a moisture content of 0.4%. The product was passed through a B.S. 6 mesh sieve and had a bulk density at 25 p.s.i. of 1.1 and a grain size such that 98 percent passed through a BS. 8 mesh sieve 64 percent passed through a BS. 16 mesh sieve 34 percent passed through a BS. 30 mesh sieve An unconfined 2 /2 diameter canister cartridge of the product was capable of being initiated by a detonator containing 0.65 g. of an 80/ 20 mercury fulminate/ potassium chlorate mixture. The velocity of detonation was 2,200 and the power Was 87% blasting gelatine. The sensitivity to frieton was the same as Example 1 and the product was initiated by the impact described in Example 1 at 120 cm. height.

Example 11 8.6 parts of a phenol/formaldehyde resin (having a molar ratio of 1 phenol to 2.2 formaldehyde units) dissolved in 8.8 parts of 1.2 percent aqueous sodium hydroxide solution were added to 91.4 parts of granular ammonium nitrate as used in Example 1. The mixture was dried at 90 C. for 4 hours as described in Example 1. The moisture content of the product was 0.4 percent and the cake was broken through a BS. 6 mesh sieve. The bulk density was 0.75 at p.s.i. and the sieve grain size such that 99 percent passed through a BS. 8 mesh sieve 79 percent passed through a BS. 16 mesh sieve 39 percent passed through a BS. mesh sieve An unconfined 2 /2" diameter canister cartridge was capable of initiation to detonation by a detonator containing 0.65 g. of an 80/20 mercury fulminate/ potassium chlorate detonator. The sensitivity to impact and friction were similar to Example 10.

What we claim is:

1. An ammonium nitrate/resin explosive composition consisting essentially of a nitrate selected from the group consisting of ammonium nitrate, mixtures of ammonium nitrate with alkali metal nitrate and mixtures of ammonium nitrate with alkaline earth nitrate and a sensitizing non-explosive phenol-aldehyde resin, said resin being present in a suflicient amount to render the composition sensitive to a commercial detonator having a base charge of 0.24 gram of pentaerythritol tetranitrate or 2.0 grams of 80/ 20 mercury fulminate/potassium chlorate.

2. An explosive composition according to claim 1 wherein the proportion of resin is between about 3.5% to about 10% by weight of the explosive composition.

3. A process for the preparation of an explosive composition according to claim 1 which comprises mixing granules of said nitrate with the phenol-aldehyde resin dissolved in a solvent without dissolving said granules and drying said mixture by removing said solvent.

4. A process as claimed in claim 3 wherein the solution is an alkaline solution of the aldehyde resin.

5'. A process as claimed in claim 3 in which the solvent is less than 10 percent by weight of the ammonium nitrate.

6. A process as claimed in claim 3 wherein, after removal of the solvent, the granules are heated to above C.

References Cited by the Examiner UNITED STATES PATENTS 1,700,085 1/ 1929 Scott 149-7 2,630,379 3/1953 Lytle 1497 2,841,481 7/1958 Hall 14919 2,995,432 8/1961 Corley et al. 14960 X BENJAMIN R. PADGETT, Primary Examiner.

CARL D. QUARFORTH, Examiner.

A. G. BOWEN, S. I. LECHERT, Assistant Examiners.

Claims (1)

1. AN AMMONIUM NITRATE/RESIN EXPLOSIVE COMPOSITION CONSISTING ESSENTIALLY OF A NITRATE SELECTED FROM THE GROUP CONSISTING OF AMMONIUM NITRATE, MIXTURES OF AMMONIUM NITRATE WITH ALKALI METAL NITRATE AND MIXTURES OF AMMONIUM NITRATE WITH ALKALINE EARTH NITRATE AND A SENSITIZING NON-EXPLOSIVE PHENOL-ALDEHYDE RESIN, SAID RESIN BEING PRESENT IN A SUFFICIENT AMOUNT TO RENDER THE COMPOSITION SENSITIVE TO A COMMERICAL DETONATOR HAVING A BASE CHARGE OF 0.24 GRAM OF PENTAERYTHRITOL TETRANITRATE OR 2.0 GRAMS OF 80/20 MERCURY FULMINATE/POTASSIUM CHLORATE.