US2433417A - Blasting explosive - Google Patents

Description

Patented Dec. 30, 1947 BLASTING EXPLOSIVE Charles D. Bitting, Kenvil, N. J., and Robert W. Lawrence, Wilmington, Del., assignors to Hercules Powder Company, Wilmington, Del., a

corporation of Delaware No Drawing. Application October 5, 1943,

. Serial No. 505,036

1 This invention relates to gelatin dynamites of improved explosive properties and more particularly to gelatin dynamites in which the improvement results from the incorporation therein of low density, cellular, carbonaceous ingredients which have been specially treated to provide stiffened cell walls.

For use in blasting under wet conditions, or at various depths under liquid heads such as, for example, water and oil, blasting gelatin andgelatin dynamites have long been used. As is well known in the art, gelatin dynamites consist of a plastic explosive formed by the gelatinization of nitroglycerin with nitrocellulose to which mixtures may be added oxidizing salts and carbonaceous ingredients. These compositions are especially resistant to the penetration of water and for that reason are particularly useful for blasting under liquid heads.

Diificulties have been encountered in the past with gelatin dynamites becoming insensitive after prolonged storage and when used under the great depths of water-and oil such as are-encountered, for example, in seismographic prospecting and oil well shooting. In the latter case, it has been fairly well established that this results because the apparent density of the gelatin has increased, approaching the theoretical'density of the'mixture of ingredients used.

This difficulty has been overcome to a certain extent by the incorporation of suitable low density ingredients in the gelatin dynamite. Although the pressure to which such a gelatin dy amite can be subjected is increased slightly, the results ob tained are not very much better than with ordinary gelatin dynamites. Essentially the same difficulty is encountered as with ordinary gelatines when they are used under the high heads of liquid that are prevalent in oil well shooting and seismographic' prospecting. The gelatins are still very much compressed in consequence of the high pressure so that the apparent densities of the gelatin dynamites still approach the theoretical'maximum density so closely that the explosive becomes insensitive to detonation by ordinary blasting caps. Incorporation of appreciable quantities of low density ingredients also has an undesirable effect in lowering the initial density of the gelatin dynamite so much that it may become undesirably bulky.

This invention has as an object the production of explosive compositions'ofimproved sensitiveness under adverse conditions. A further object of this invention is the preparation of gelatin dynamites which will function successfully after more or less prolonged subjection to immersion under great depths of water or other liquids. A still further object of this invention is to accomplish this without seriously departing from thej b asic characteristics of gelatin dynamites,

11 Claims. (01. 52-13) which involve in addition to water resistance, high density and plasticity. A still further object of this invention is to provide a low density, cellular, carbonaceous ingredient, which when incorporated in a gelatin dynamite, will prevent excessive compression under high pressures. Still further objects will appear hereinafter.

The objects of this invention are accomplished in accordance with this invention by using corncob meal treated with a material which will effectively stiffen the meal so that the cell structure willnot be destroyed under high liquid pressures, as an ingredient in gelatin dynamite.

Weshall within this specification and claims use the term gelatin dynamite to include the three main classes ofgelatin dynamites which are commonly known as straight gelatins, ammonia gelatins, and permissible gelatins. The straight gelatins range in strength, according to the usual terminology, from 20 to 100%. The latter is commonly known as blasting gelatin. These ordinarily contain a gelatinized liquid explosive ingredient, with varying proportions of sodium nitrate and combustibles, depending on the strength and other properties which may be required. The ammonia gelatinsusually containa smaller proportion of gelatinized liquid explosive than straight gelatins of the same grade strength,the strength being made up by the use of ammonium nitrate. Permissible gelatins may be of either the straight or the ammonia type, with the addition of a safety ingredient which permits their safe use in coal mines, where there is danger of explosion from mine gas and coal dust.

We have found that low density, carbonaceous ingredients prepared in accordance with the copending application of Lawrence, Serial No, 459,- 007 now Patent No. 2,375,008, produce a gelatin dynamite which will suffer less than the usual degree of compression under high pressures. Carbonaceous ingredients which are suitable for this purpose include cork, balsa, bagasse, bongo wood, corncobs, and their equivalents which have been comminuted to a desired screen size to reduce them to a particulate form. The treatment to which they are subjected involves treating the material while in particulate form at an elevated temperature with heat-hardening synthetic resins such as the urea-aldehyde, phenol-aldehyde, thiourea-aldehyde type resins and the like; and subse'quently heat-hardening the resin in situ. The synthetic resins may be formed and hardened on the carbonaceous ingredient or applied as an intermediate condensation product, from a solution in water or an organic solvent, which is hardened after evaporation of the solvent. Thus, in accordance with the copending application of Lawrence, the resins are formed as a supporting film on the individual particles of the particulate carbonaceous material and thus strengthen and support 3 the unaltered interior cellular structure of these individual particles.

The art has heretofore incorporated low density carbonaceous ingredients such as cork, balsa wood, bagasse, etc., in gelatin dynamites to improve their sensitiveness under high water pressures. However, this incorporation has not 4 Alternatively, the urea formaldehyde solution may be sprayed on the hot corncob meal and the mixture dried and the resin hardened as before; or the urea-formaldehyde solution may be mixed cold with the corncob meal and the mixture heated with continuous agitation to form the resin, dry the mixture, and harden the resin;

yielded gelatin dynamites which are entirely satisfactory under high liquid pressures. Improvement in the art using these untreated carbonaceous ingredients has been only slight. Furthermore, the density of the gelatin dynamite is often lower than is desirable, thereby requiring larger packages for a given weight of explosive. By using treated carbonaceous ingredients, a remarkable improvement in sensitiveness under high liqud pressure is secured with a small quantity of low density material and at the same time gelatin dynamites of the desired normal high density are produced. Thus, gelatin dynamites can be prepared which will have a density in the order of 1.5-1.6 g./cc. and will shoot after two hours under water at 50 1bs./sq. in. of Water pressure by incorporation of 3% of untreated corncob meal. However, incorporation of 3% of treated cob meal will give ge latins having a density in the order of that of the untreated meal which will shoot after two hours under water at 500 lbs/sq. in. of water pressure. Infact, the gelatins with treated cob meal have been shot after periods of one and two weeks under water at 500 and 400 lbs/sq. in., respectively.

The present invention makes it possible to prepare gelatin dynamites economically and simply which are of greatly increased effectiveness when used under high pressure conditions.

Now the present invention is specifically directed to a gelatin type exposive composition comprising a liquid explosive, nitrocellulose, and corncob meal having the cell walls thereof stififened with a synthetic resin heat-hardened in situ. carbonaceous ingredients stiffened with a synthetic resin heat-hardened in situ, other than corncob meal, which have been found suitable for this purpose are disclosed in our copending application, Serial No. 329,492, filed April 13, 1940, now Patent No. 2,365,170.

The advantages of the invention are illustrated by the following specific embodiments. The corncob meal used will preferably have a major proportion retained on a 40 mesh screen and may consist of the entire ground cob or certain fractions thereof. For example, the woody outer part and the pithy inner part have been found to give very satisfactory results as well as the entire ground cob. However, the essential factor resides in the size of the treated corncob meal as is set forth in the examples following.

The treatment which gives the stiffened cells may be carried out in the following manner: The corncob meal is placed in a suitable container heated to approximately 70 C.-, and a solution of urea in an aqueous formaldehyde solution is added to the corncob meal and the mixture is incorporated. The mixture is then further heated to cause condensation of the urea-formaldehyde and to dry the meal. This drying may conveniently be carried out at about 70-100 C. The corncob meal and the resin thus treated will then be additionally heated to harden the resin. This is done by heating for to 1 hour or more at 100 C. or for shorter periods at temperatures up to 150 C. This procedure, as will be obvious to those skilled in the art, may be varied considerably.

or the urea may be mixed with the corncob meal and then the formaldehyd solution added with drying and hardening of the resin carried out as described above.

The ratio of the urea to formaldehyde may be varied over wide limits, for example, from 1 part of urea and 2 parts of 40% formalin, to 1 part of urea and 5 parts of 40% formalin (37% formaldehyde by weight), although we do not wish to be limited by these proportions. Furthermore, the solutions may be diluted to any desired degree, although for economy of operation, it is desirable to use quite concentrated solutions.

Instead of preparing the resin in the above described manner, a partial condensation product of urea and formaldehyde may be prepared by methods well known in the art which can be applied from an aqueous solution or from solution in an organic solvent such as ethyl alcohol, the carbonaceous material heated, the solvent evaporated, and th resin heat-hardened.

In treating corncob meal with urea-formaldehyde solution, good results have been obtained when the quantity used was such as to give a final product containing from about 20% to about 45% of resin. The preferred range is from about 25% to about 40% resin by weight of the final treated corncob meal.

In the use of the phenol-aldehyde resins to treat corncob meal, the most satisfactory results are obtained when the resin is formed in and on the outer cellular structure of the corncob meal. For example, oresol may be dissolved in 37 formaldehyde solution, catalyst stirred in and the mixture added to the corncob meal. By heating the mixture of corncob meal with the cresol and formaldehyde, condensation, drying and hardening of the resin ar accomplished, The final hardening operation is carried out at temperatures in the range of -150 C Other heat-hardening resins or combinations may be used to treat the cellular material, for example, a combination of chlorinated rubber and a heat-hardening phenol-aldehyde resin, such as Bakelite No. 3360, gives good results when applied to corncob meal from an organic solvent and then heat-hardened. Alternatively, these materials may be applied from an aqueous emulsion of a concentrated solution of these materials in an organic solvent. This has the advantage of limiting the quantity of solvent used, thus reducin the fire hazard and eliminating the necessity of installing a recovery system for the solvent.

The corncob meal in accordance with this invention is in particulate form when treated with a suitable heat-hardening resin and has a hard, rather gritty feel in contrast to the soft and compressible qualities of the untreated material. Incorporation of the treated corncob meal in gelatin dynamites to the extent of from about 1 to about 10%, but preferably in the order of about 3 results in greatly improved ability to detonate under conditions of high Water pressure.

In the preparation of the specially treated corncob material, two factors are of especial importance: (1) Mixing. with the resin ingredients in a relatively low viscosity phase to insure thorough incorporation; and (2) continuous agitafollows:

Pounds Cob meal (dry weight) 100 Aqueous formaldehyde (37% by weight) 98 Urea 41 The'above gave a resin-treated product containing about 36% resin.

Table I following shows three gelatin type dynamites characterized in turn by no cob meal, untreated cob meal and resin-treated cob meal. The type resin and the proportions used were the same as indicated above. The resin-treated cob meal contains 36.7% resin.

TABLE I Untreated Cob Meal Treated No Cob Meal Cob Meal Formula, Per cent Nitroglycerin.--. Nitrocellulose.

alsa Untreated Cob Meal.. Resin-Treated Cob Meal- Chalk Physical Properties:

Hardness at 70 F Density, g./cc..-- C Si tg. ze Tests Under Water Pressure: After 2 hr. under 50 lb./sq.

in. After 2 hr. under 751b./sq.

1.11. After 2 hr. under 500 lb./sq.m.

Failed....-

Shot.

With reference to the above table, it will be seen that only the dynamite made with the resintreated material shot under a high water pressure, that is, in the order of 500 lbs/sq. in.

In Table 11 following is shown nitroglycerin absorbency and screen tests on cob meal with various resin contents from to approximately 25%,

in which A represents the cob meal before treatment, B with 0% resin content and C, D and E, resin contents of 10.1, 20.4 and 24.7%, respectively.

TABLE III Cob meal wzth varzous resin contents Composition A B C D E Cob Meal Dry Wt., g 890 890 890 890 Formnlin, g 1 507 169 380 506 "Dre 75 169 225 Moisture, per cent- 10.97 2. 42 1.61 2. 35 2.91 Density, g./cc 0. 398 0.338 0.356 0.373 0.379 NG Absorbency, per 56.1 62. 0 56. 4 56. 4 55. 6 Resin Content, per cent 0 10. l 20. 4 24 7 Screen Test, per cent:

On 12 mesh T T T 0.1 0.2

On 29 mesh. 12.1 14. 7 15. 3 20. O 17.

On 40 mesh. 66. 9 57. 6 62. 8 64. 6 60. 6

On 60 mesh. 14. 6 14.6 12. 1 9. 1 13. 0

On 100 mesh. 4. 5 7. 1 5. 1 3. 4 5.0

Thru 100 mesh 1. 9 6. 0 4. 7 2. 8 3. 7

1 Water.

With reference to the above table, it will be noted that the cob meal B, with the 0% resin content, was water-treated with the amount of water contained in the quantity of formaldehyde solution shown in Table III as follows:

TABLE I11 Gelatin dynamite made with cob meal having [various resin contents Example D-l D-2 D-3 D-4 Formula, percent:

40% Nitroglycerin." 49.0--- 49.0 49.0.---- 49.0. Nitroeotton 1.5.... 1.5 .5 1.5. Sodium Nitrate alsa Resin -Treated Cob Meal Composition. D Chalk 1.0 1.0 1.0.--. 1.0 Physical Properties:

Hardness at 72 F.. 16# 15# l9# 22#. Den ity, gJcO 1.556. 1.557. 1.522.. 1.532. Ctg. Size 2 x 16" 2 x 16" 2" x 16 2" X16" Resin content of cob 10.1..... 20.4..... 24.7.

meal, per cent. Tests Under Water Pressure:

After 2hr. at 50 lb./sq. Failed. Failed.

1H. After 2 hr. at 1b.] do Failed sq. 111. After 2 hr. at 200 lb.!

sq. in. After 2 hr. at 300 1b.]

sq. in. After 2 hr. at 500 lb./ Shot.

sq. in.

With reference to Table III above, it will be seen that the example containing cob meal with a resin content in the order of 24.7% Was the only one that shot under an exceedingly high water pressure. Therefore, about 25% is the preferred lower limit for resin content in accordance with the applicants invention, although it is to be understood that successful results can be attained with reduced resin content at lower pressures.

In the above formulations where the use of nitroglycerin is indicated, it should be understood that by the term nitroglycerin is meant either this compound by itself or with the addition or partial substitution of any of the commonly used freezing point depressants such'as, for example, ethylene glycol dinitrate, nitrated polymerized glycerin, nitrated sugars, nitrated chlorhydrins, dinitrotoluene, etc. The term nitroglycerin as here described is well accepted in the explosive art.

The explosive compositions of the invention have been found especially advantageous in blasting operations Where there is a substantial liquid head above the explosive charge. In deep well blasting such as, for example, seismographic prospecting and oil well shooting, these compositions have proved invaluable since their sensitiveness is not impaired under the high pressures encountered. The compositions are also utilizable in underwater operations, such as those carried out in channels or harbors, due to the retention of their sensitivity under high pressure.

It will be understood that the details and examples hereinbefore set forth are illustrative only, and that the invention as broadly described and claimed is in no way limited thereby.

This application is a continuation- -in-part of our application for United States Letters Patent, Serial No. 329,492, filed April 13, 1940, now Patent No. 2,365,170,

What we claim and desire to protect by Letters Patent is:

1. A gelatin type explosive composition compr si g a ieoicl e plosi e. nitrooe tliose. andcomooh meal, havin t e el t .Q' ZQ sti ned with synthetic: esin. heat-ha den d situ said corn cob meal being; o a Sizesuch. that a major proportion retained on a 40 mesh screen.

A ge a in ype explosive, co po i io c m.- prising a liquid explosive, nitrocellulose, and between about 1%. and about Qt o q meal having the cell walls thereof stiffened with a. synthetic resin heatardened in si u s Corn cob meal being of a size such that amaior proportion is retained on a ,0 mesh screen,

3. A gelatin type explosive composition comprising a liquid explosive, nitrocellulose, and corncob meal having the cell Walls thereof stifiened with between about 20 and about ,557), of a synthetic resin heatehardened in situ said corn cob meal being of a size such that a, maior'nro portion is retained on a 40 mesh screen.

4. A gelatin type explosive composition comprising a liquid explosive, nitrocellulose, and

corncob meal having the cell Walls thereof stifitened with a phenol-aldehyde resin heat-hardened in situ said corn cob meal being of a size such that a major proportion is retained on a 49 mesh screen.

5. A gelatin type explosive composition comprising a liquid explosive, nitrocellulose, and corncob meal having the cell walls thereof stiffened with a urea-aldehyde resin heat-hardened in situ said corn cob meal being of a size such that a major pro g ortiqm is retained on a 40; mesh scre n- 6;. A gelatin type explosive composition comprising a liquid explosive, nitrocellulose, andbetween about 1% and about of a corncob meal having the cell walls thereof stiffened with a phenol-aldehyde resin heat-hardened in situ saiq corn cob meal being of a size such that a; major proportion is retained on a 40 mesh screen.

7. A gelatin type explosive composition comprising a liquid explosive, nitrocellulose, and between about 1% and about 10% ofa' corncob meal having the cell Walls thereof stiffened with a urea-aldehyde resin heat-hardened in situ said corn cob meal being of a size such that a major proportion is retained on a- 40 mesh screen,

8 it. A a la n wh exp os ve QmP Q itLon. c n risine a. iquid, explosi e. nitr c ll ose. and orncob h ing he ol-l walls there f. tifi ened with. between. about, and. about 4.5 '7. of

- a. phenol-aldehyde resin heat-hardened in situ,

id. com ooh m al be ng o a. size such. tha a mai r pronort on. s re a ned o a 41 mesh screen.

s. A ge atin tyne expl s ve om osi ion com: pris ng liq dexnl s a. nitr cellul se... and. corncob meal having the cell walls thereof stifii= ened with between about 20% and about 45% ot a urea-aldehyde resin heat-hardened in situ aid corn oh me l eing of: a such that. a. major proportion is retained on a mesh screen.

10. A gelatin type explosive composition comprisinga liquid explosive, nitrocellulose, and; between about 1% and about 10% of corncob meal having the cell wallsthereof stiffened with betwe bout 20% and about of a phenolal'dehyde resin heat-hardened in situ said corn cob meal being of a size such that a major pro portion is retained on a 40 meshscreen.

ll. A gelatin type explosive composition com-- prising a liquid explosite, nitrocellulose, and between about 1% and about 10% of corncob meal having, the cell walls thereof stiffened with between about 20,-% and; about 45% of a urea-aldehyde resin heat-hardened in situ said corn cobm e n or a. ize. such that. a. ma or rone-r tion is v retainedQn a 4O-mesh screen.

CHAR E H TTING ROBERT W. LAWRENCE.

REFERENCES CITED The following, references are of, record: in the file Q i aten UNITED STATES Number Name Date 1,923,848 Spaeth Aug. 22,1933 1,979,681; Fox Nov 6; 13.934 1,992,189 Chapman Feb. 26; 1935 2,211,737 Berkley Aug. 13, 1940 2,334,149- Ripper Nov. 9,1943

EQBEIGN ATENTS Number Country: Date 514.5,4510 GreatBritairr s May 26, 1 9 42