IL28378A - Explosive compositions - Google Patents

Description

■ -*v This invention relates to stable, sensitized explosive compositions comprising nitromethane and as sensitizer, resin balloons. In a particular aspect, this invention relates1 to stable, gelled explosive compositions comprising nitromethane and as sensitizer, resin balloons. In a further aspect, this- invention relates to stable, gelled explosive compositions- in the form of the explosive core for detonator cord comprising nitromethane and as sensitizer, a finely divided, air-entrapping material. In a still further aspect, this invention relates to novel detonating cord having a stable, sensitized explosive core in gelled form comprising nitromethane and a finely divided air-entrapping material.

Explosive compositions comprising nitromethane and a sensitizer for the nitromethane are well-known and are used in a variety of applications. Sensitized nitromethane explosive ■compositions are used in either the normally . liquid form or in gelled form. Normally liquid nitromethane compositions are readily converted to semi-solid or thickened form typically referred to as "gelled form nitromethane" by incorporation with a suitable gelling agent for the nitromethane, such as for example nitrocellulose. Other gelling or thickening agents for nitro^ methane are disclosed in Application Gorial Noi ΊΊ 0 ,-700 farled i-oaued Peptembar g?} ·1&&ΰ. -to R. "Fi Puir&ali .

Numerous materials are known to sensitize nitromethane, of which the nitromethane soluble amines, in particular lower alkylimine, arylalkyleneamine , monoethanolamine , alkylphosphorous-amide, aryldiamine, aminopyridine , N, N ' -diethyl-p-phenylene-diamine, hydrazine and alkylarylidiamine are generally most effective when nitromethane containing explosive compositions sensitized for detonation with conventional blasting caps are desired. . ^ Despite the effectiveness of the aforementioned nitro-methane soluble amines in sensitizing nitromethane, explosive compositions comprising nitromethane and one or more of said amines present serious problems with respect to stability.

Nitromethane explosive compositions sensitized with the' afore-stated amines are generally unstable and decompose after storage for several days . The instability of the 'explosive compositions is a particular drawback when the compositions are used in gelled form as the explosive material in the explosive core of detonator cord. Detonator cord typically comprises an explosive core in the form of a solid explosive composition, a sheath, e.g. a textile sheath for the explosive core and an outer cover of metal or a thermoplastic material such as polyvinyl chloride or polyethylene. When nitromethane sensitized by the aforestated amines: is used in gelled form as the explosive core of detonator cord, pressure from gases formed from the decomposition of the nitromethane often causes ballooning or rupture of the outer covering of the detonator cord.

It is an object of the present invention to provide stable, sensitized nitromethane explosive compositions.

It is a further object of the present invention to provide stable, sensitized nitromethane explosive compositions in gelled form.

It is a still further object of the present invention to provide . stable , gelled, sensitized nitromethane explosive composition in the form of the explosive core for detonator cord.

It is an additional object of the present invention to provide a detonator cord having a stable, sensitized explosive core.

Other objects and advantages of the present invention will be apparent from the specification and appended claims.

The present invention in a first embodiment resides in the discovery that sensitized nitromethane explosive compositions which are stable against decomposition are obtained by incorporating into the explosive composition a sensitizing^ amount of resin balloon.

The present invention in- a second embodiment resides in the discovery that gelled, sensitized nitromethane explosive compositions which are stable against decomposition are obtained by incorporating into the gelled explosive composition a sensitize ing amount of resin balloon.

The present invention in a third embodiment resides in the discovery that gelled, sensitized nitromethane explosive compositions which are stable against decomposition and suitable as the explosive core of detonator cord are obtained By- incorpo^ rating into the gelled explosive composition a sensitizing amount of a finely divided, air-entrapping material. Examples of such finely divided, air-entrapping materials include bagasse, wood flour, ground balsa, resin balloons and the like. Because of the excellent results obtained therewith resin Balloons' are preferred.

The resin balloons of use in the explosive, compositions-of the present invention are water insoluble and nitromethane insoluble, thin-walled, hollow, spherical balloons- of a polymerized thermosetting resin selected from the group cons sts ' ing of urea-formaldehyde and phenol-formaldehyde. The resin balloons ar$ of low density and small particle size. Typical resin balloons have a bulk density of less than 0.3 gr./c.c. and a diameter of from ,about 2 to about 360 microns. Resin Balloons are more fully described in U. S. Patent 3,101,288 to Coursen, et al issued August 20, 1963. Such resin Balloons are commercially available.

The amount of resin balloons required to sensitize ^ nitromethane explosive compositions will vary and will depend chiefly on the use desired for the particular explosive composition. Typically suitable amounts of resin balloons in the explosive compositions of the present invention are in the range of from about 0.1 to about 20% by weight based on the weight of the explosive composition. While amounts greater than 20% by weight of resin balloons may be included in the explosive compositions of the present invention, such amounts- are "considered excess. For most applications and in particular when the explosive composition is used in gelled form as the explosive core of detonator cord, amounts of resin balloons in the range of from about 1.5 to about 10% are preferred.

Explosive compositions comprising nitromethane and resin balloons may be prepared in any suitable manner, as for example by mixing the resin balloons with the nitromethane. It is well understood in the art that high temperatures during mixing should be avoided.

It is sometimes desirable to include one or more additives1 in the explosive compositions of the present invention in order to enhance or alter their performance in particular applications. For example, it is often desirable to include a fuel and/or an oxidizer in the explosive compositions of the present invention.

Examples of fuels include elemental carbon in various-forms, such as carbon black, graphite and the like; aliphatic hydrocarbons such as pentane, octane, dodecane and cyclohexanfe ; organic polymers such as liquid and solid polymers of ethylene and propylene; organic ketones such as diethyl ketone, ethyl butyl ketone, cyclohexanone and the like; and alkyl ethers of saturated glycols such as the monomethyl ether of ethylene glycol and the monoethyl ether of ethylene glycol and the like.

Examples of oxidizers include ammonium nitrate, sodium nitrate, lithium nitrate and the like.

Examples of other additives include guanidine nitrate, pentaerythritol tetranitrate , and cyclotrimethylene trinitramine .

The explosive compositions of the present invention may be used in either the normally liquid or in gelled form.

.Normally liquid nitromethane is readily converted to gelled form by incorporation of a suitable thickening or gelling agent into the nitromethane as previously indicated.

The explosive compositions of the 'present invention have a variety of uses well-known to the art. As previously indicated, gelled explosive compositions of the present invention are especially useful as the explosive core of detonator cord. The compositions of the present invention also are particularl useful in oil wells to fracture oil bearing formations.

The invention will be understood more fully- by reference to the following specific examples. It is understood that the examples are presented for the purpose of illustration only and are not ntended as a limitation of the invention.

In the examples the resin balloons used were prepared from phenol-formaldehyde resins and were commercially sold by the Bakelite Company,, a Division of Union Carbide Corporation under the trademark "Microballoons". The resin balloons were of small particle size and low bulk density. Microballoons manufactured from urea-formaldehyde resins are also commercially available and if desired can be substituted for "Microballoons" manufactured from phenol-formaldehyde resins.

■ E AMPLE 1 Tests were conducted to show the effectiveness of resin balloons in sensitizing nitromethane explosive compositions.

The sensitized explosive compositions used in the >tests designated A-G inclusive in the table below were prepared by blending resin^ balloons into a gelled nitromethane explosive composition prepared by blending 95 parts by weight nitromethane with 5 parts by weight nitrocellulose. The composition used in test H contained no resin balloons and was prepared by blending 95 parts by weight nitromethane with 5 parts by weight nitrocellulose-.

In each test 100 grams of nitromethane explosive composition was placed in a 2" diameter plastic cup. The cup was placed behind a safety shield and was detonated by a No. -6 or. No. 8 blasting cap. The blasting caps were commercially sold by; Atlas Powder Company. The results of the tests are set forth in the table which follows: TABLE Test Resin Balloons Detonator Detonation Weight Percent A 1% No. 6 None B 1% No. 8 Partial C -1.5% No. 6 Partial D . 1.5% No. 8 Complete E 2.5% No. 6 Complete F 5.0% No. 6 Complete G 10.0% No. 6 Complete H None No. 8 None The above results show the effectiveness of resin balloons as sensitizers for nitromethane.

EXAMPLE 2 A detonator cord was prepared by loading a piece of polyethylene tubing 14 inches in length and 1/8 inch, in diameter (inside) with- a gelled , sensitized nitromethane explosive composition comprising 95 parts by weight nitromethane, 5' parts-by weight nitrocellulose and 5 parts by weight resin balloons'.

The cord was detonated with a No. 6 blasting cap.

Detonation of the entire cord was obtained. The rate of detonation was in excess of 18,000 feet per second.

EXAMPLE 3 The following is an example of a stable, sensitized nitromethane explosive composition.

Parts By Weight Nitromethane (liquid) 95 Phenol- formaldehyde Resin 5 Balloons EXAMPLE H The following is an example of a stable, sensitized nitromethane explosive composition in gelled form.

Parts by Weight Nitromethane 100 Carbon black . 40 Ammonium nitrate 200 Nitrocellulose ' 6 Phenol- formaldehyde resin 10 Balloons EXAMPLE 5 The following is an example of a stable, sensitized nitromethane explosive composition in gelled form suitable- for use as the explosive core in detonator cord.

Parts by Weight Nitromethane 95 Nitrocellulose 5 Ground balsa 5 EXAMPLE 6 The following is an example of a stable, sensitized nitromethane explosive composition in gelled form suitable for use as the explosive core in detonator cord. 1 Parts by Weight Nitromethane 95 Nitrocellulose 5 Bagasse 8 Since many embodiments of this invention may be made and since many changes may be made in the embodiments described, the foregoing is to be interpreted as illustrative only and the invention is defined by the claims appended hereto.

Claims (7)

1. An explosive composition characterized by nitromethane and from 0.1 to 20¾ by weight based on the weight of the composition , of a water-insoluble and nitromethane-insoluble polymerized thermosetting resin selected from the group con-sisting of phenol-formaldehyde and urea-formaldehyde resins in the form of thin-walled, hollow, spherical balloons.

2. A gelled explosive composition characterized by nitromethane, a gelling agent for the nitromethane and from 0.1 to 20% by weight based on the weight of the composition of a water-insoluble and nitromethane-insoluble polymerized thermosetting resin selected from the gorup consisting of phenol-formaldehyde and urea-formaldehyde resins in the form of thin-walled, hollow, spherical balloons.

3. The composition of claim 2 wherein the said balloons have a bulk density of less than 0.3 g. per c.c. and a diameter in the range of from 2 to 360 microns.

4. The composition of claim 2 wherei the said gelling agent is nitrocellulose.

5. The composition of claim 2 in the form of an' explosive core for detonator cord.

6. The composition of claim 5 wherein the spherical balloong have a bulk density of less than 0.3 g. per c.c. and a diameter in the range of from 2 to 360 microns.

7. The composition of claim 5 wherein the amount of said spherical balloons in said composition is in the range of from 8, A detonator oord Including an explosive core formed of an explosive composition according to Claim 2 or 5» a sheath for said core and a cover for said eheath. for the Applicants S IS/DD