US2338164A - Explosive composition - Google Patents

Description

I Patented Jan. 4,

UNITED srA'rss PATENT orr cs Hercules Powder Company, W

llmlngton, Del.,

a corporation of Delaware No Drawing. Application August 31, 1940,

.Beriai No. 355.025

14 Claims. (CI. 52-7) This invention relates to blasting explosives. and more particularly to a nongelatinous type of explosive possessing a high resistance to water.

Nongelatinousblasting explosives of the type customarily used are normally comprised of a mixture of dry, solid ingredients such'as ammonium and/r sodium nitrates, wood pulp, and/or other carbonaceous ingredients and sensitizing explosives such as nitrostarch, dior trinitrotoluenes or the like, either with or without nitroglycerin and other liquid sensitizers. A flne 1y powdered antacid such as chalk is also added to most compositions.

Dynamites'of'the above type, while suitable for blasting in dry holes, have the disadvantage of such poor resistance to water that they cannot be usedin boreholes that are appreciably wet." Water in contact with such mixtures will penetrate fairly rapidly, dissolving or saturating the ingredients and greatly reducing or completely overcoming the explosive force. Since the occurrence v of wet boreholes is fairly common, the application of such dynamites is seriously restricted. Consequently numerous attempts have been made in the past to increase their water resistance. These attempts have been restricted to two methods, one involving the use of rigid or semirigid,

waterproof containers, for example, of tin-plate or heavy paper, and the other involving-surface treatments of the water-sensitive ingredients, for example, by coating the salt content of the Qdynamites with water-repellant or resistant coating agents such as wax-like or resinous substances.

While a very high degree of water resistance may be imparted by using 'water-proof'containare, the provision of an inflexible or stifl container involves manufacturing difiiculties, may increase the hazards of packing sensitive explosives, and restricts the useful. applications of the dynamite. For example, the cartridges may not be subdivided or deformed to fit the borehole.

The coating of the water-soluble salts, although not subject to these disadvantages necessarily involves an additional step in the manufacture of the dynamite ingredients. This necessity considerably complicates the manufacturing procedures, especially in case of mixtures containing several components. In such cases. it is usual to coat only the ingredient that is the most affected by the water, for example, the ammonium nitrate, and rely on the water resistance of the coated ingredient to protect the rest of the mixture. This procedure, however, is not completely satisfactory and does not always give the desired eflect. The coating of the entire mixture, or

of coating each ingredient separately, is not feasible because of the increased hazard and the in-.

a mechanical admixture containing water-soluble salts which will be resistant to water.

A further object is to provide a means for reduclng the rate of solution of a soluble salt in water A still further object of this invention is to provide a material which when incorporated in an admixture produces an increased water resistance. v

Other objects will be apparent hereinafter.

These objects in accordance with this inven-i tion are accomplished by adding to the dynamites or mixtures of water-sensitive and soluble ingredients during the mixing thereof, for example, by conventional mixing machines, a small proportion of substantially petroleum-hydrocarbon insoluble pine wood resin in finely divided or pulverized condition. The amount to be added may be varied between fairly wide limits to give the desired water resistant effect, but it has been found that between about 0.1% and about 5% gives the maximum water resistance with the minimum eflect on the explosive power and other physical properties of the composition, and preferably between about 0.25% and about 2.0% is used. The addition of this substantially petroleum-hydrocarbon insoluble pine wood resin to soluble salts and mixtures thereof in explosive compositions protects the ,soluble salts against the action of water. In accordance with this invention the use of this resin has been found adaptable for other applications, for example. in reduction in the rate of solution 'of soluble fertilizer salts, etc.

The principal requirements for a successful application of my method are the use of the insoluble resin in the proper screen size and the attainment of a suiiiciently thorough distribution thereof among the other ingredients in the mixture. To produce-a satisfactory effect the substantially petroleum-hydrocarbon insoluble pine I as 2 assaies size such that substantially all of the material will pass a 60 mesh screen and preferably will pass a 100 mesh screen. However, in the special case of application to nitroglycerin-containing resin is slightly soluble in the nitroglycerin and the partial or complete solution of the coarser partlclesleads to a more thorough distribution, but I do not wish to be limited to this explanation. The use of the coarser material is advisable only in case of explosives containing nitroglycerin.

The substantially petroleum-hydrocarbon insoluble pine wood resin 'is adaptable for use in this application on account of its brittleness and the facility with which it maybe pulverized to a finely divided form. It is superior to many other resins, in this respect. In addition, the melting point of the material is sufficiently high so that once pulverized, it does not tend to sinter or fiow together again, but remains free-flowing. This resin may be obtained commercially in a pulverized form and will remain in the pulverized form indefinitely. The commercial material normally has the following screen analysis- 100% through 30 mesh, 90% through 80 mesh and 60% through 100 mesh.

The present method for attaining a high degree of water resistance comprises the admixture of the finely powdered. resin into the salt .containing admixtures at room temperature.

By the present method, the entire process is carried out at normal temperatures and this leads to great simplicity in operation and improved safety. It is possible in accordance with by grinding. Over 90% of the ground product would pass a 100 mesh screen and approximately 50% :passed a- 200 mesh screen. One part of the powdered resin was added to 99 parts of ranular ammonium nitrate and the two substances were thoroughly mixed at room tempera.-

ture. The resultant mixture was tested for water resistance by the following method.

The test I employ to determine water resistance of such mixtures and of dynamites comprises packing the material firmly into a 25 cc. Gooch crucible, covering the material with a layer of cheesecloth stretched tightly over the top, immersing the crucible and contents in water at 65 F. in an inverted position to a depth of 2 inches, suspended by wires. After a predetermined time, th crucible and contents are removed and drained, the dry contents separated by a knife from the moistened portion, and the weight of the former determined as percentage of the original material.

The comparative water resistance of the untreated and treated ammonium nitrate as described above is given in Table I.

TABLE I Water Material resistance (24 hrs.)

Per cent Untreated ammonium nitrate 0 Ammonium nitrate containing 1% substantiallypetroleum-hydrocarbon insoluble pine wood resin.. I 59 The comparative water resistatnce of dynamites with and without small proportions of the pine wood resin is given in Table II.

TABLE II Dynamite composition Per cent Per cent Nitroglycerin l3. 5 l3. Ammonium nitrate 74. 0 74. Sodium nitrate 4. 8 4. Carbonaceous materials and chalk. 7 7 7.

Pulvcrized substantially petroleum-hydrocarbon iusoluble pine wood resin 0, 0 0.

Water resistance (24 hrs.) 0 84 It is evident from these results that when used in soluble salts or in dynamite compositions of a type usually possessing little or no resistance to the penetration of water, a small proportion of pulverized substantially petroleum-hydrocarbon nitroglycerin, 37.5% ammonium nitrate (coated with 1% of a wax-resin mixture as disclosed in my copending application Serial No. 152,668), 34.7% uncoated sodium nitrate, 14.3% carbonaceous ingredients, sulfur and chalk, and 0.5% pulverized substantially petroleum-hydrocarbon insoluble pine wood resin. When submitted to the abovewater resistance test, this dynamite was 72% dry after 16 hours immersion in water. Corresponding samples with the same formula but (1) without the gasolineinsoluble resin or (2) without either the coating or the powdered resin gave test results of about 30% and0% dry after a 16 hour test. The latter dynamite was completely'wet after less than 10 minutes immersion. Thus it will. be seen that whereas the application of either the powdered resin or a resinwax coating will result in a considerable improvement in water resistance, an improved resistance may be realized from the combination of both,

Th substantially petroleum-hydrocarbon pine wood resin which I have found greatly increases the water resistance of various dynamite compositions may be modified by various chemical treatments such as for example, by condensing with formaldehyde, surface treating with calcium oxide, precipitating with calcium oxide, or by the formation of other water insoluble modified forms with various chemicals. These water insoluble modified forms of the resin have been found to give improved water resistance equivalent to those results obtained by using the unmodified resin.

A modified resin was prepared by treating an aqueous suspension of the substantially petroleum-hydrocarbon insoluble pine wood resin with assume 0.5% of its weight of calcium oxide dissolved in" the water. The resulting modified resin was dried and when incorporated in a dynamite composition was found to give results comparable to the unmodified resin. The water resistance results obtained by incorporating the modified resin are compared to the results obtained by incorporating unmodified resin and to the results without resin in Table III below:

Tenn III IPowdered'resin incorporated zf ggf None a S] ht trace. 17 unmodified resin 153 1 o modified resin 53 The composition of the dynamite tested inthe the control powder which .contained no resin had 10.3% manioc.

- of the extraction processes utilized. This resin will meet or nearly meet the following specificstion. namely, substantial insolubility in petro leum-hydrocarbons, substantially complete slu-' bility in alcohol, a methoxy content from about 3% to about 7.5% (usually from about 4% to about 6%) an acid number in the range from about 90 to about 110, and a, drop melting point in the range from about 96 C. to about 125? 0.

It will be understood that the details and examples given hereinbefore are illustrative only andin'no way limiting on my invention as broadly described hereinbefore and in the appended claims.

- What I claim and desire to protect by Letters Patent is: p g 1. An explosive composition comprising watersoluble oxidizing inorganic salt and substantially petroleum hydrocarbon-insoluble pine wood res-- An additional test was made in which 1% of the resin modified by treatment with formaldehyde gave results comparable to'the limed resin above. Modifying with formaldehyde was accomplished by treating 500 parts of the unmodifled resin with 297 parts of 37.2% aqueous formalin, 155 parts of ammonium hydroxide (29% NIH) and 2148 parts of water. The mixture was heated until th water was expelled and the resin was in molten form. The product was cooled, pulverized and used in a dynamite mix with satisfactory results.

The material-which is characterized by the term substantially petroleum-hydrocarbon insoluble pine wood resin," herein and in the appended claims; is the resinous material which may be prepared from pine wood, preferably from stump pine wood, in the following manner. Thepine'wood, which may or may not have been steamed. to remove volatile constituents such as turpentine and pine oil, may be extracted with a coal tar hydrocarbon such as benzol or toluol, and the extract'freed of volatile constituents,

leaving a residue consisting of a mixture of wood rosin and the resin used in the present compositions. Extraction of this mixture with a petroleum-hydrocarbon such as, for example, gaso- 1ine,'dissolves and removes the rosin. After separation of the rosin, high in-abietic acid, a resinous residue remains which is low in abi'etic acid.

Alternatively, the initial coal tar hydrocarbon extract may be treated with furfural, and the two layers which form, separated, in which case the resinous residue is found dissolved in the furfural from which it may be obtained by evaporation of the furfural. This resinous residue, used in the composition of the present invention, is characterized by a dark red brown color, cherry red in solution, and by substantial insolubility in petroleum-hydrocarbons, ,but it will vary somewhat in its specific characteristics such as acid number, melting point, exact petroleum ether solubility, and content of naphtha and toluol insoluble material, depending upon the details the order of 20 mesh.

in, said resin being present in pulverulent form in amount from about 0.1 to about 5% by weight of said salt and the major portion thereof capable of passing through a screen of the order of mesh.

2. An explosive composition comprising ammonium nitrate and substantially petroleum hydrocarbon-insoluble pine wood resin, said resin being present in pulverulent form in amount from about 0.1 to about 5% by weight of said ammonium nitrate and the major portion thereof capable of passing through a screen of the order of 60 mesh.

3. An explosive composition comprising a mix:

ture of water-soluble oxidizing inorganic salts and substantially petroleum hydrocarbon-insoluble pine-wood resin, said resin being presentin pulverulent form in amount from about 0.1 to about 5% by weight of said salts and the major portion thereof capable of passing-through a screen of the order of 60 mesh.

4. An explosive composition comprising a sensitizer, an oxidizing salt, and substantially petroleum hydrocarbon-insoluble pine wood resin, said resin being present in' pulverulent form in amount from about 0.1 to about 5% by weight of the composition and themajor portion thereof capable of passing through a screen of the order of 60 mesh. I

5. An explosive composition comprising a liq- --uid explosive nitric ester, granular ammonium nitrate, a carbonaceous ingredient, and substantially petroleum hydrocarbon-insoluble pine wood resin, said resin being present in pulverulent form in amount from about 0.1 to about 5% by weight of the composition and the-major portion thereof capable of passing through a screen of '6. An explosive composition comprising nitroglycerin, ammonium nitrate, sodium nitrate, and

substantially petroleum hydrocarbon-insoluble pine wood resin,-said resin being present in pulverulent form in amount from about 0.1 to about 5% by weight of the composition and the major portion thereof capable of passing through a screen of the order of 20 mesh.

7. The explosive of claim 6 in which the sub.- stantially petroleum hydrocarbon-insoluble pine wood resin is. chemically modified by condensing with formaldehyde.

8. The explosive of claim 6 in which the substantially petroleumhydrocarbon-insoluble pine wood resin is chemically modified by treating with calcium oxide.

9.. A composition comprising granular inorganic nitrate and substantially petroleum hydrocarbon-insoluble pine wood resin. said resin being present in pulveru'lent form in amount from about 0.1 to about 5% by weight of said inorganic nitrate and the major portion thereof capable of passing through a screen of the order of 60 mesh.

1Q. A composition comprising granular ammonium nitrate and substantially petroleum hydrocarbon-insoluble pine wood resin, said resin being present in pulverulent form in amount from about 0.1 to about 5% by weight of said ammonium nitrate and the major portion thereof capable of passing through a screen of the order of 60 mesh.

11. The explosive composition of claim 1 in which the substantially petroleum hydrocarboninsoluble pine wood resin is chemically modified bycondensing with formaldehyde.

12. The explosive composition of claim 1 in which the substantially petroleum hydrocarbonin'soluble pine wood resin is chemically modified by treating with calcium oxide.

13. The composition of claim 9 in which the substantially petroleum hydrocarbon-insoluble pine wood resin is chemically modified by con- 1 densing with formaldehyde.

14. The composition 01' claim 9 in which the substantially petroleum hydrocabon insoluble pine wood resin is chemically modified by treating with calcium oxide.

ROBERT W. CAIRNS.