US3496039A - Explosive compositions containing an aromatic nitro compound and calcium phosphate - Google Patents

Description

U.S. Cl. 149-2 5 Claims ABSTRACT OF THE DISCLOSURE In an explosive composition comprising fusible aromatic nitro compounds, the improvement which comprises calcium phosphate fume in a minor proportion effective to improve detonation characteristics, thermal stability or exudation characteristics. The calcium phosphate fume is characterized by low density and high specific surface area.

The invention relates to the improvement of the properties of explosives and explosive compositions of fusible aromatic compounds, particularly TNT and trinit-robenzene, or mixture-s of these nitro compounds with nitramines and/ or with nitric acid esters, e.g. mixtures with tetry-l and/or nitropentaerythrol (nitropenta), including e-ute tics with tetryl or nitropenta, by adding finely divided calcium phosphate to them. Known additives, such as metal powders or desensitizers can be included.

The calcium phosphate has been manufactured by mixing phosphoric acid with the required amount of calcium nitrate or calcium chloride to form a clear solution or paste, and by spraying this mixture into a current of hot inert gas at temperatures of 190 to 450 C. The production of the calcium phosphate fume is described in DAS 1,196,166, issued to Chemische Fab-rik Kalk. We call this product calcium phosphate fume. The calcium phosphate fume is a finely divided product having a large specific surface area, in general about l50 m. /g., and having an extremely low bulk density in general about 0.010.07 g./cm. It is added to the explosive components in minor proportion, e.g. a quantity of 0:1 to 15 preferably 0.2 to5% by weight of the composition.

It has been found that the addition of the abovementioned calcium phosphates to the fusible aromatic nitro compositions and compounds, for example, TNT and trinitrobenzene, surprisingly modifies particularly the following three properties;

(1) The capability of detonation is improved;

(2) Thermal stability and shock resistance; and

'(3) The exudation of impurities is largely prevented.

Also particularly surprising was the extent to which the properties of the castable explosives according to the invention changed. This is made apparent hereinafter by a comparision betwen TNT charges with and without the addition of calcium phosphate.

EXAMPLE 1 Sticks of TNT were cast with and without the addition of calcium phosphate. The length of the sticks was 20 cm., and the diameter was varied. The sticks of explosives were ignited with a pressed pellet of 15 g. of tetryl and were stood up on a lead plate which served as an indicator for complete detonation. The tests were performed without any enclosure. A stick of TNT having a diameter of 50 mm. and no additive would not propagate the detonation and the lead plate was undamaged.

3,496,039 Patented Feb. 17, 1970 If the TNT contained 1% calcium phosphate (specific surface area 15 m. /g.; bulk density of 0.03 g./cm. the charge detonated perfectly all the way through the stick, even at a diameter of 10 mm.

Cast TNT cylinders 200 mm. long and 28 mm. in diameter and having a specific weight of 1.60 g./cm. could not be detonated with No. 8 aluminum blasting caps. With the addition of 1.5% calcium phosphate, such explosive sticks detonated perfectly all the way through. The density of this explosive composition according to the invention amounted to 1.58 g./cm. The tests were performed with any wrapper or enclosure. At the end of the stick opposite the blasting cap, a detonation speed of 6600 m./s. was measured. If 12 or 15% calcium phosphate was added to the molten TNT, a paste-like composition was obtained having a specific weight of 1.61 g./cm. and 1.64 g./cm. respectively. Cylinders 200 mm. long and 28 mm. in diameter prepared from this composition could not be detonated, even with a No. 6 blasting cap containing 0.5 g. of PETN and 0.5 g. of potassium chloride as a booster. The detonation speed amounted to 6500 and 6200 m./s. respectively.

The advantage of the improved detonatability consists mainly in the fact that TNT charges can be detonated easily without the use of boosters made of pressed tetyrl, PETN, hexogen or TNT. In fact, cast TNT charges containing the calcium phosphate additive according to the invention can be used as boosters for explosives that are diflicult to initiate. For example, slurries can be detonated in blasting holes with detonators made of TNT and the calcium phosphate additive according to the invention, instead of charges of cast pentolite such as are used today.

The improvement in thermal stability and shock resistance is clarified by the following experiments: 0.4 g. of TNT with and without the addition of calcium phosphate according to the invention was finely ground and placed in a glass test tube. This tube was placed in a 'heated bath of Woods metal which was adjusted to a constant temperature. The time it took for the TNT to flash or explode was determined. The longer this time is, the better the explosion tolerates thermal stress. The time for TNT amounted to 38 seconds, and for TNT containing the addition of 2% calcium phosphate according to the invention amounted to seconds. The falling weight impact tests were performed according to Koenen Ide (Explosivstotfe, N0. 2, February 1961, pp. 3436). With a weight of 5 kg. and a 10 cm. drop, the first explosions produced in the TNT were without additive. If the TNT contained the addition of 2% calcium phosphate according to the invention, the beginning of the reactions was not obtained until the drop amounted to 20 cm. The following results were measured for the total of 6 tests of each explosive at heights of 10, 20, 30, 40, 50 and 60 cm.:

98: TNT,

2 calcium TNT phosphate No reaction 24 28 Partial reaction 0 4 Explosion 12 4 paper and exposed for 20 hours to a temperature of 70 C. This produced spots of greater or lesser size on the filter paper. The larger the diameter of these spots, the greater is the tendency of the explosive to exudation. For a TNT with a solidification point of 80.47 C., a spot diameter of 44 mm. was measured. If increasing amounts of calcium phosphate are added to this TNT, the following spot diameters are measured:

Calcium phosphate content (percent): spot diameter, mm. 44

The advantage of the addition of calcium phosphate according to the invention consists, according to this eX- periment, in the fact that cast TNT charges can be stored at higher temperatures, e.g., in hot sunlight, without the occurrence of exudation.

EXAMPLE 2 The experimental results described in Example 1, involving explosive charges of TNT with and without the addition of calcium phosphate according to the invention were obtained in like manner also with explosive compositions made of aromatic nitro compounds and metal powders. A cast stick (200 mm. long, 28 mm. diam.) made of a mixture of 75% TNT and 25% aluminum powder with the addition of 2% calcium phosphate (specific surface area 15 m. /g.; bulk density 0.03 g./cm. according to the invention could be detonated with a No. 8 aluminum blasting cap, for example, while the same mixture without the addition of the calcium phosphate could not be initiated with a No. 8 aluminum blasting cap. A mixture of 47.6% TNT and 52.4% aluminum required 59 seconds to flash or explode at a temperature of 340 C. However, if 1 part of calcium phosphate was added to the mixture, the time required to ignite it amounted to 67 seconds. The size of the spot produced by bleeding was measured at 38 mm. for the mixture of 75% TNT (solidification point 80.47 C.) and 25% aluminum. With the addition of 1% calcium phosphate according to the invention, the diameter of the spot amounted to only 11 mm.

EXAMPLE 3 In the case of explosive compositions containing a suflicient amount of nitramines or nitric acid esters, the improvement of detonatability by the addition of calcium phosphate according to the invention is of no importance. Consequently, it has not been our aim to bring about an improvement of the initiability of such compositions. In the case of such explosive mixtures, flashing or explosion was produced at 238 C. after the following periods- Mixture A:

40% TNT (solidification point 80.47 C.),

60% hexogen seconds 33 Spot diameter mm 40 Mixture B:

39% TNT (solidification point 80.47 C.),

60% hexogen, 1% calcium phosphate (specific surface area 12 m. /g.; bulk density 0.07 g./cm. "seconds" 40 Spot diameter mm 10.5

EXAMPLE 4 In the case of explosive compositions of TNT (solidification point 80.47 C.), hexogen and powdered aluminum, flashing or explosion was produced at 235 C. within the periods specified below, the specific weights and spot diameters being also given- 4 Mixture A:

TNT percent 35 Hexogen do 40 Aluminum powder do 25 Time seconds Spec. weight g./cm. 1.85 Spot diameter mm Mixture B:

TNT percent 30 Hexogen do Aluminum powder d0 25 Desensitizer consisting of 4.2 parts paraflin wax, 0.7 part nitrocellulose, 0.1 part lecithin do 5 Time seconds 29 Specific weight g./cm. 1.77 Spot diameter mm Mixture C:

TNT percent 34.5 Hexogen do 40.0 Powdered aluminum do 25.0 Calcium phosphate (spec. surface area 42 m. /g.; bulk density 0.01 g./cm. do 0.5 Time seconds 46 Specific weight g./cm. 1.84 Spot diameter mm 8.3

From this it is apparent that the addition of calcium phosphate according to the invention not only produces an excellent desensitizing effect and an obvious reduction of bleeding as compared with the conventional desensitizers, but also that the castings made from such compositions also have a greater specific weight than those made with the conventional desensitizers.

EXAMPLE 5 In the case of explosive compositions made from TNT (solidification point 80.47 C.) and tetryl (this two component mixture is known as tetrytol), the following spot diameters were measured and flashing or explosion occurred at 230 C. after the following periods- Mixture A:

TNT percent 30 Tetryl d0 70 Time seconds 28 Spot diameter mm 48 Mixture B:

TNT percent 30 Tetryl do 69 Calcium phosphate (spec. surface area 18 m. /g.;

bulk density 0.025 g./cm. do 1 Time seconds 42 Spot diameter mm 18 In these two experiments the explosive was not in powder form, but was placed in the test tube in the form of a piece weighing 0.4 g.

EXAMPLE 6 In the case of explosive compositions of TNT (solidification point 80.47 C.) and PETN (pentaerythritol tetranitrate), flashing or explosion occurred at 230 C. after the periods of time specified hereinafter, and the spot diameters were as described- Mixture A:

TNT percent 50 PETN do 50 Time seconds 27 Spot diameter (at C.) mm 41 Mixture B:

TNT percent 50 PETN do 49 Calcium phosphate (spec. surface area 20 m. /g.;

bulk density 0.02 cm. do 1 Time seconds 34 Spot diameter (at 65 C.) mm 13 In these two experiments the explosive was placed in the test tube not in powder form but in the form of a piece weighing 0.4 g.

EXAMPLE 7 The following are the spot diameters and the time periods required to produce the flashing or explosion of explosive mixtures of tetryl, trinitrobenzene and hexogen at 230 C.

Mixture A:

Tetryl percent 16 Trinitrobenzene do 24 Hexogen do 60 Time seconds 30 Spot diameter mm 50 Mixture B:

Tetryl percent 16 Trinitrobenzene do 24 Hexogen do 59 Calcium phosphate (spec. surface area m. /g.;

bulk density 0.03 g./cm. do 1 Time seconds 38 Spot diameter mm 19 The spot test was performed at 75 C. over a period of 2 hours.

EXAMPLE 8 The addition of calcium phosphate to explosive com positions according to the invention can also be combined with the addition of other desensitizers. The desensitizing effect of such combined additives in this case can be increased considerably if, for example, a mixture of chlorinated naphthaline with a softening point of 116 C. is used as a desensitizer together with the calcium phosphate (spec. surf. area 15 m. /g.; bulk density 0.03 g./cm. For explosive compositions made from tetryl and TNT (solidification point 80.47 C.), and known as tetrytol, the following are the spot diameters and the time periods required to produce flashing or explosion at 230 C.

Mixture A:

Tetryl percent 70 TNT do 30 Time seconds 28 Spot diameter (at 60 C.) mm 48 Mixture B:

Tetryl percent 69 TNT do 30 Chlorinated naphthaline do 1 Time seconds 43 Spot diameter (at 60 C.) mm 50 6 Mixture C:

Tetryl percent 69 TNT do 30 Calcium phosphate do 1 Time seconds 42 Spot diameter (at C.) mm 18 Mixture D:

Tetryl percent 68 TNT do 30 Calcium phosphate do 1 Chlorinated naphthaline do 1 Time seconds 53 Spot diameter (at 60 C.) mm 20 In these 4 experiments the explosive was not placed in the test tube in powder form, but in the form of a piece weighing 0.4 g.

The specific surface area was measured according to Blaines test. This test is described in the directives by the Verein Deutscher Ingenieure (VDI) (Association of German Engineers) No. 2031 of October 1962 under the title Feinheitsbestimmungen an technischen Staeuben and can be obtained from the VDI-Verlag GmbH, Dusseldorf, Germany.

What is claimed is:

1. In an explosive composition comprising fusible aromatic nitro compounds of the group trinitrotoluene and trinitrobenzene, the improvement which comprises calcium phosphate fume having a specific surface area of about 1050 m. g. and a bulk density of about 0.01-0.07 g./cm. in a minor proportion effective to improve detonation characteristics, thermal stability or exudation characteristics.

2. Explosive composition according to claim 1, wherein the calcium phosphate fume is present in amount of about 0.145% by weight of the composition.

3. Explosive composition according to claim 2, said amount being about 0.25% by weight of the composition.

4. An explosive composition according to claim 1 containing a material of the group nitramines, nitric acid esters, and mixtures thereof.

5. An explosive composition according to claim 1 and containing metal powder.

References Cited UNITED STATES PATENTS 3,271,212 9/1966 Riedl et a1 149106 X CARL D. QUARFORTH, Primary Examiner S. I. LECHERT, JR., Assistant Examiner US. Cl. X.R.

mg? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,496,039 Dated Feb. 17, 1970 Ioventofls) Adolf Berthmn, l.

It is certified that error appear in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

F T I C 201. Zfline l2 change "with" to ---without-.

.- P smusumo SEALED L I (SEAL) "Atteat: L

Edward'n'nmha' *2" wmma E. sudw .m. Attesting Officer Q 5. Oomissiqnqif orjetents