US2471851A - Manufacture of high-explosive compositions or charges - Google Patents

Description

developed by which these apparently ;tradictory requirements have been met.

for instance, it is possible to prepare such an exfplosive consisting of a predominating proportion Patented May 31, 1949 UNITED STATES PATENT OFFICE MANUFACTURE OF HIGH-EXPLOSIVE COMPOSITIONS OR CHARGES No Drawing. Application August 15, 1944, Serial No. 549,639. In Great Britain August 18, 1943 Claims.

- primers, but which are characterised by low sensitiveness to mechanical shock and friction. Certain compositions, as for examples those claimed in U. S. Patent No. 2,407,595, have recently been con- Thus,

, of finely crystalline pentaerythritol tetranitrate embedded in a lesser proportion of a matrix of a ,solution of nitrocellulose in a liquid mixture of dinitrotoluenes and trinitrotoluenes with or .without a proportion of a non-explosive nitrocellulose solvent constituent. This explosive is an example of the general kind of detonating explosive composition to which the present invention particularly relates, namely, compositions of the kind in which a finely divided crystalline high explosive compound sensitive to detonation -by friction or shock (hereafter referred to as ffsensitive ingredient) is embedded in a matrix comprising nitrocellulose dissolved or gelatinised in a water insoluble liquid nitrocellulose solvent which is substantially non-volatile and relatively 'insensitive to detonation by friction or shock (hereinafter referred to as the insensitive ingredient) In the manufacture of compositions of the I kind described the chief hazard is associated with for the manufacture of detonating explosive compositions of the kind described and in the form of aggregates capable of conversion into plastic form by mechanical working, comprises forming a slurry of the sensitive ingredient and the nitrocellulose in a substantial quantity of cold water,

,-mixing into the said slurry at ordinary temj perature a proportion of the insensitive ingredient insufficient to form a continuous phase,

but sufficient to agglomerate the sensitive ingredient and the nitrocellulose into discrete aggregates each containing the nitrocellulose in swollen but incompletely gelatinised condition as- ,sociated with the insensitive ingredient and with a plurality of the crystals of the sensitive ingredient, separating the still discrete aggregates from the bulk of the cold water without the application of any appreciable pressure, and drying the separated aggregates without causing any substantial coalescence thereof.

The sensitive ingredient may consist, for example, of pentaerythritol tetranitrate or other crystalline solid nitric ester, a nitramine or certain aromatic nitrocompounds. The insensitive ingredient may consist of certain aromatic nitrocompounds for instance, a liquid mixture of dinitrotoluenes and trinitrotoluenes, with or without a proportion of a non-explosive liquid nitrocellulose solvent.

The sensitive ingredient is preferably used in water-wet condition and the nitrocellulose can also advantageously be in water-wet form. The amount of water in the slurry may conveniently be about 4 to 6 times the weight of the sensitive ingredient.

In carrying out the present invention the mixing operation is preferably continued until the water is substantially clear of the solvent.

When the amount of the sensitive ingredient required to be present in the composition substantially exceeds the amount of nitrocellulose solvent which is required to be present, it will usually be permissible to introduce the whole of the one or more nitrocellulose solvents to be used into the slurry and yet obtain discrete aggregates that can be satisfactorily separated from the bulk of the water and dried without sticking together too much, but otherwise preferably only a portion of the one or more nitrocellulose solvents required is introduced into the slurry and a further quantity of one or more nitrocellulose solvents introduced subsequent to the drying of the aggregates, namely, when the dry aggregates are being converted into plastic form and the one or more solvents introduced at this stage need not necessarily be the one or more solvents added to the slurry.

Mechanical or other non-manual means for agitating the contents of the mixing vessel during the distribution of the liquid nitrocellulose solvent through the explosive mixture in the slurry are desirable, provided they are not so violent in their action as to compress the aggregates appreciably together. The water may be largely decanted away, and the aggregates may be drained. In order to assist the drying of the moist aggregates, it is frequently desirable to break down the larger ones, which can often be achieved by crumbling them lightly with the fingers or otherwise, whilst avoiding any such pressure aswould tend to com- 3 pact them into dense masses. The moist aggregates may then be spread in layers of about half an inch thickness or less on drying trays so that While they are in the stove they have no substantial weight of material pressing down upon them, and drying is" continued until the moisture content does not exceed approximately 1%, which will usually take several hours. For re'a sons of safety and convenienceit is often desirable to carry out the drying at somewhat lower temperature than can be used without causing any substantial merging of the aggregates. Thus, the liquid nitrocellulose solvent may frequently include ingredients that become more appreciably volatile in steam as the temperature rises towards the boiling point of water, which can nevertheless be used witholit serious loss if the drying temperature of the drying air is kept below, say, 65 C. The dried aggregates when cold are distinctly lessIiable to stick together under pressurethan the jr'no'ist' aggregates, and if desired they may b stored or transported in substantial quantities whilein this' condition. For the purpose of converting the explosive content into plastic form it may convenientlybe worked in a Mo- Roberts type of mixer, but other methods of mech anically working it may otherwise be used.

Qnciethe explosive has been made plastic it may be loaded or ca'rtri'dged by means of an extrusion machine or the like.

The invention is illustrated in the following examples, in which the parts are parts by weight:

Example 1 through a 160 mesh British stander-a specificar scien iyt ab it to 15% 'of its weight of Water. The nitrocellulose used consists partly of quarter seco'nd industrial nitrocellulose or 11.9% nitrogen content, and. partly of blasting somme'hitroeeiluibse, both of which (are use in the water wet'eohdition, containing from about one third to about half of their own weight of water, in each'cas'e reckoned on the dry material. The liquid hi'tiocelliilose s61- vent cohsists 'of a mixture "or about 14% trinitrotoluene, 11% dibutyl phthalate and 75% of a mixture of isomeric emamttmenes wholly liquid at a temperature approximating to the melting point of ice, as obtained 'b'y'n'itration of the 'so- "called inta f'raction of 'rn'o'no'nitrotoluene obtaihed as a lay-product of the manufacture of orthoand para -nitr'otol'uene.

The amount of the water 'w'et pentaerythritol tetr'anitrate 'correspondingto 66.5 parts of the material and amounts of the Wet nitrocelluloses equivalent to 3.6 parts of the quarter second in- 'dustrial nitrocellulose "and 0.4 part of the blastf 'ing soluble nitrocottfon are mechanically stirred in about 500 parts tree 1 water in a mixing machine fitted with slanted b'afiies 'ahd a paddle. After about ten minutes mixing 30.5 parts of the liquid nitrocellulosesolvent are introduced and l the stirring is c unuea;forabout 21 minutes. by Whih time the SOIV'G'lll? 'Sl'iOUl-ld "be Well distributed in association with the pentaerythritol tetranitrate and the nitrocelluloses. The slurry is allowed to settle and the bulk of the water is decanted. The somewhat sticky powder that remains is transferred to filtering cloths and drained without application of pressure first Without and then with suction on the filter. The d'rained material, which at this stage usually contains about 16% moisture, is transferred to drying trays after large quantities have been rubbed down. On the cloth bottoms of the drying trays it is spread out into half inch layers and the trays are then inserted into a stove in which hot air at 60 C. is passed through them, and in which the material is dried down to a water content not exceeding 1%, which may take from four to six hours. Only a negligible amount of the nitrocellulose solvent is lost during the deaiitation and filtering of the water, and the loss of the solvent being steamed away in the course (if drying usuanyamountsto about one' part. Cold an is then introduced into the stove, the dried and cooled material is removed and bagged for storage and/or transport. Itis-firially worked iii a McRobe'rt's mixer until it has become satisfactorily plastic. The resulting'plastic composition can then be loaded into containers or cartridged by means of an extrusion machine.

The resulting plastic explosive has a power amounting to about of that of blasting gelatine, as measured in 'theballistic mortar and can be initiated by a No'f'8' l'ead styphnate-lead az'idetetryl detonator at a velocity of detonation of approximately 7,000 metres per second. It is preferred, however, to employ a one o'u'nce'tetryl pellet for its initiation. The density is'appro'xiinately 1.45 grams per cubic centimetre, andthe explosive neither burns nor detonates when backed by a steel plate and struck by a 0.303 rifle bullet Mark VII fired from a range of '30 yards from a servicerifie. It remains plasticon storage.

Example 2 The ingredients used and the composition of the plastic explosive are the same as in Example 1, but only 15.5 parts of the liquid nitrocellulose solvent mixture are introduced into the slurry of the pentaerythritol tetranitrate and the nitrocelluloses, the remaining 15 parts being mixed in the McRobertsmixer with the dried and cooled composition removed from the drying stove. The

properties of the final explosive are very similar to those of the explosive made according to Example 1, but the material on the filter from the slurry is not quite so sticky as the material obtained at the corresponding stage, according to Example 1.

Example 3 tion screemwet with about 10 to 15 per cent of its weight of water.

The nitrocellulose and the liquid nitrocellulose solvent used are the saine as in Example 1.

The afmourit of the water-wet cyclctrim'ethylene"trinitramiiie-corresponding to 6655 parts of the dry ma-renalarra amounts'or the Wet intro cellulose equivalent to 3.6 parts of the quarter second industrial nitrocellulose and 0.4 part of the blasting soluble nitrocotton are mechanically stirred in about 500 parts of cold water in a mixing machine fitted with slanted baffles and a paddle. After about ten minutes mixing parts of the liquid nitrocellulose solvent are introduced and the stirring is continued for about minutes as in Example 1 but instead of finally working the powder alone in a McRoberts mixer it is worked with a further 10 parts of the liquid nitrocellulose solvent until it has become satisfactorily plastic.

The resulting plastic explosive has a power amounting to about 96% of that of blasting gelatine, as measured in a ballistic mortar and can be initiated by a No. 6 lead styphnate-lead azide-tetryl detonator at a velocity of detonation of approximately 7000 metres per second.

The density is approximately 1.45-1.50 gram per cubic centimetre, and the explosive is sensitive to rifle bullet fire under the same conditions as given in Example 1. It remains plastic on storage.

We claim:

1. A process for the manufacture of detonating explosive compositions containing nitrocellulose, a crystalline high explosive compound sensitive to detonation by shock or friction selected from the group consisting of a solid crystalline nitric ester and a solid crystalline nitramine, and a liquid mixture comprising dinitrotoluenes and trinitrotoluene wherein the crystalline high explosive compound is in the predominating proportion and the nitrocellulose is in the least proportion which comprises forming a slurry of the crystalline high explosive compound and the nitrocellulose in cold water, admixing the said liquid mixture, and continuing the mixing operation until the nitrocellulose and the crystalline compound are converted into discrete aggregates, separating the thus formed aggregates from the bulk of the water without the application of pressure, and thereafter drying the aggregates.

2. The process of claim 1 wherein the dried aggregates are mechanically worked into plastic consistency.

3. The process of claim 1 wherein an additional quantity of said liquid mixture is added and the resulting aggregates are mechanically Worked into plastic consistency.

4. The process of claim 1 wherein the crystalline high explosive compound comprises cyclotrimethylene trinitramine.

5. The process of claim 1 wherein the crystalline high explosive compound comprises pentaerythritol tetranitrate.

HAROLD REGINALD WRIGHT. JAMES TAYLOR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,547,809 Hale July 28, 1925 1,867,283 Stettbacher July 12, 1932 1,867,287 Stettbacher July 12, 1932 1,924,465 Teeple Aug. 29, 1933 2,079,792 Delficio May 11, 1937 2,235,298 Olsen Mar. 18, 1941 2,407,595 Williams et a1 Sept. 10, 1946 FOREIGN PATENTS Number Country Date 13,486 Great Britain 1889 469,721 Germany Dec. 20, 1928 11,809 Great Britain 1913 437,035 Great Britain Oct. 23, 1934