PROPELLENT CHARGE COMPRISING NITROCELLULOSE
United States Patent 3779820
A dry compacted Caseless Propellant Charge comprising in addition to the usual constituents of a propellant explosive, a proportion of nitrocellulose having an average nitrogen content of 11.0 to 12.0 percent by weight.
US Patent References:
Nitric acid esters of cellulose and method of preparation
Bennett et al. - January 1957 - 2776965
/3655836.html
Dehm et al. - April 1972 - 3655836
METHOD OF MAKING PROPELLANT BODY HAVING VOIDS THROUGHOUT BODY
Remaly et al. - May 1972 - 3673286
Nitric acid esters of cellulose and method of preparation
Bennett et al. - January 1957 - 2776965
/3655836.html
Dehm et al. - April 1972 - 3655836
METHOD OF MAKING PROPELLANT BODY HAVING VOIDS THROUGHOUT BODY
Remaly et al. - May 1972 - 3673286
Inventors:
Stevely, Robert Reid (Saltcoats, SC)
Webster, William Snodgrass (Beith, SC)
Webster, William Snodgrass (Beith, SC)
Application Number:
05/282057
Publication Date:
12/18/1973
Filing Date:
08/21/1972
View Patent Images:
Export Citation:
Assignee:
Imperial Chemical Industries Limited (London, EN)
Primary Class:
Other Classes:
102/700, 264/3.300, 149/96, 149/97
International Classes:
C06B21/00; C06B25/18; C06B25/00; C06B5/00; C06B5/02
Field of Search:
102/DIG.1 149/2,97 260/220 264/3C
Primary Examiner:
Sebastian, Leland A.
Claims:
What we claim is
1. A unitary caseless propellant charge consisting of dry compacted grains of a propellant composition comprising a high nitrogen content nitrocellulose and 10 to 30 percent by weight of a nitrocellulose of 11 to 12 percent nitrogen content by weight.
2. A propellant charge as claimed in claim 1 formed with a surface indent to accommodate an appropriate quantity of a priming composition.
3. A propellant charge as claimed in claim 2 wherein the surface indent contains priming composition.
4. A propellant charge as claimed in claim 3 wherein the priming composition comprises lead styphnate.
5. A method of making a unitary caseless propellant charge which method comprises dry compacting grains of the composition of claim 1 at pressures in the range of 30,000 to 70,000 psi.
6. A method as claimed in claim 5 wherein the propellant grains are porous.
1. A unitary caseless propellant charge consisting of dry compacted grains of a propellant composition comprising a high nitrogen content nitrocellulose and 10 to 30 percent by weight of a nitrocellulose of 11 to 12 percent nitrogen content by weight.
2. A propellant charge as claimed in claim 1 formed with a surface indent to accommodate an appropriate quantity of a priming composition.
3. A propellant charge as claimed in claim 2 wherein the surface indent contains priming composition.
4. A propellant charge as claimed in claim 3 wherein the priming composition comprises lead styphnate.
5. A method of making a unitary caseless propellant charge which method comprises dry compacting grains of the composition of claim 1 at pressures in the range of 30,000 to 70,000 psi.
6. A method as claimed in claim 5 wherein the propellant grains are porous.
Description:
This invention relates to a propellant composition for caseless propellant explosive charges, to charges made from such compositions and to a method of making such charges.
The use of caseless propellant charges as the power source for projectiles and for explosive percussion tools such as nail guns is now established. However, the design of a satisfactory unitary propellant charge having ballistic properties comparable to those of a granular charge presents many problems and as yet caseless charges have not captured any significant proportion of the market.
A caseless charge must be designed so that, on ignition, burning will not be limited to the surface of the charge but will occur throughout the mass as in a loose charge. In one method of preparing caseless propellant charges individual grains of propellant explosive composition are compacted either dry or treated with plasticiser or solvent to stick the grains together in a coherent mass. The degree of compaction is intended to be such as to bind the grains sufficiently to prevent breakage in normal handling but to leave the charge sufficiently friable that the grains separate and burn as a loose charge on actuation of the primer which is used to ignite the charge. It is extremely difficult to achieve a balance of the many factors involved so as to produce a satisfactory commercial charge which will burn reliably without leaving a residue which can jam breech mechanism of a nail gun.
It is an object of this invention to provide a nitrocellulose propellant composition which, in granular form, can be compacted to produce an improved unitary compacted caseless propellant charge.
We have found that propellant grains containing a proportion of nitrocellulose having an average nitrogen content 0f 11.0 to 12.0% N by weight can be dry compacted without solvent or adhesives to give improved unitary caseless propellant charges. The charges disintegrate more reliably under the action of the primer to simulate the ballistic effect of a loose charge better than compacted charges hitherto available, and they can be handled in normal use without substantial loss due to breakage.
Accordingly, the propellant explosive composition of this invention comprises, in addition to the usual constituents of a nitrocellulose based propellant explosive, a proportion of low nitrogen nitrocellulose having an average nitrogen content of 11.0 to 12.0 percent by weight. The propellant may conveniently be a single-base propellant based on high nitrogen nitrocellulose having an average nitrogen content of 13.2 to 13.4 percent by weight (guncotton), a double-base propellant containing nitroglycerine and guncotton nitrocellulose or a triple-base propellant containing nitroguanidine, nitroglycerine and guncotton nitrocellulose.
Preferably the proportion of low nitrogen nitrocellulose is within the range 10 to 30 percent by weight of the total composition.
From a further aspect the invention includes a unitary caseless propellant charge comprising compacted grains of the aforedescribed propellant composition. The charge is conveniently cylindrical. If desired for convenience, the charge may be formed with a surface indent to accommodate an appropriate quantity of a priming composition.
The invention also includes a method of making a unitary caseless propellant charge which method comprises dry compacting grains of a propellant composition containing, in addition to the usual constituents of a propellant explosive, a proportion of low nitrogen nitrocellulose having an average nitrogen content of 11.0 to 12.0 percent by weight. Preferably the grains are compacted at a pressure within the range 30,000 to 70,000 psi.
The propellant composition may be prepared in granular form in conventional manner, for example by incorporating into the composition a solvent or plasticiser for the nitrocellulose constitutents to form a dough and shaping the dough into the required grain by moulding or extrusion as a cord which is subsequently divided. The grains may advantageously be porous. The porosity may be achieved in known manner by initially including a removable filler in the composition which is subsequently removed from the grains. For example potassium nitrate crystals may be included and removed by leaching out of the grains with water. The amount of filler is preferably in the range 50 to 200 parts per 100 parts by weight of the composition.
The invention is further illustrated by the following Examples in which all parts and percentages are by weight.
EXAMPLE I
84 parts (as dry) of guncotton nitrocellulose having an average nitrogen content of 13.3% N vetted with 44 parts of ethyl alcohol, 15 parts of low nitrogen nitrocellulose containing an average of 11.6 to 11.8% N, 1 part of diphenylamine, 100 parts of potassium nitrate and 66 parts of diethyl ether were mixed to form an extrudable dough. The dough was extruded through a die to form a cord 1.4 mm diameter which was air dried and cut into disc-shaped grains of approximate thickness 0.32 mm. These grains were stepped in hot water (60°C) to remove most of the potassium nitrate and air dried. They were then tumbled in a pan with fine graphite (average particle size 100 μ) to give them a glaze coating to improve their free running properties and facilitate subsequent feeding to a mould. The composition of the grains was
Guncotton nitrocellulose 84 parts Low nitrogen nitrocellulose 15 parts Diphenylamine 1 part Potassium Nitrate 1 part Graphite 0.4 part
0.35 gram quantities of the grains were pressed in a mould at a pressure of 50,000 psi to form cylindrical pellet charges each having a diameter of 8.85 mm and a thickness of 3.8 mm with a circular primer indent in one of its flat faces of diameter 4.5 mm and 2.0 mm in depth.
The primer indent of each charge was filled with a priming composition consisting of 64 parts of lead styphnate and 36 parts of ground glass slurried in a solution of nitrocellulose. The slurry was dried and covered with a thin protective coating of collodion.
The caseless propellant charge of this Example was tested in an explosively actuated nail driving gun and it burned cleanly and had ballistic properties comparable to a corresponding loose granular charge. It withstood normal rough handling without breakage.
EXAMPLE II
74 parts (as dry) of guncotton nitrocellulose having an average nitrogen content of 13.3% N wetted with 40 parts of ethyl alcohol, 25 parts of low nitrogen nitrocellulose containing an average of 11.8 to 12.0% N, 1 part of diphenylamine, 50 parts of potassium nitrate and 60 parts of diethyl ether were mixed to form an extrudable dough. The dough was formed into grains which were steeped to remove the potassium nitrate and glazed as described in Example I. The composition of the resulting grains was
Guncotton nitrocellulose 74 parts Low nitrogen nitrocellulose 25 parts Diphenylamine 1 part Potassium nitrate 1 part Graphite 0.4 part
0.30 gram quantities of the grains were pressed in a mould at a pressure of 40,000 psi to form cylindrical unitary charges of approximately the same shape and dimensions as the pressed charges of Example I.
When the charges were primed as in Example I and tested in a nail gun they burned cleanly with ballistic properties comparable to those of a corresponding loose charge. They withstood normal rough handling without breakage.
EXAMPLE III
59 parts of guncotton nitrocellulose having an average nitrogen content of 13.3 percent, 20 parts of low nitrogen nitro-cellulose (average N content 11.5 percent) and 1 part of ethyl centralite were slurried with 800 parts of water and 20 parts of nitroglycerine were mixed into the slurry to form a paste. The paste was dried in hot air, mixed with 36 parts of acetone and four parts water and 200 parts of potassium nitrate were added to form a dough which was extruded and granulated as in Example I. The grains were steeped in hot water (60°C) to remove the potassium nitrate and were subsequently air dried and glazed as described in Example I.
The composition of the grains was
Guncotton nitrocellulose 59 parts Low nitrogen nitrocellulose 20 parts Nitroglycerine 20 parts Ethyl centralite 1 part Potassium nitrate 1 part Graphite 0.4 part.
0.25 gram quantities of the grains were pressed in a mould at a pressure of 30,000 psi to form cylindrical unitary charges of approximately the same shape and dimensions as the pressed charges of Example I.
When the charges were primed as in Example I, and tested in a nail gun they burned cleanly with ballistic properties comparable to those of a corresponding loose charge. They withstood normal rough handling without breakage.
EXAMPLE IV
69 parts of guncotton nitrocellulose having an average nitrogen content of 13.3 percent, 15 parts of low nitrogen nitrocellulose containing an average of 11.2 to 11.4% N, and 1 part of ethyl centralite were slurried with 800 parts of water and 15 parts of nitroglycerine were mixed into the slurry to form a paste. The paste was dried in hot air, mixed with 40 parts of acetone and 8 parts of water and 100 parts of potassium nitrate were added to form an extrudable dough. The dough was formed into grains which were steeped to remove the potassium nitrate and glazed as described in Example I.
The composition of the grains was
Guncotton nitrocellulose 69 parts Low nitrogen nitrocellulose 15 parts Nitroglycerine 15 parts Ethyl centralite 1 part Potassium nitrate 1 part Graphite 0.4 part
0.35 gram quantities of the grains were pressed in a mould at a pressure of 60,000 psi to form cylindrical unitary charges of approximately the same shape and dimensions as the pressed charges of Example I.
When the charges were primed as in Example I and tested in a nail gun they burned cleanly with ballistic properties comparable to those of a corresponding loose charge. They withstood normal rough handling without breakage.
The use of caseless propellant charges as the power source for projectiles and for explosive percussion tools such as nail guns is now established. However, the design of a satisfactory unitary propellant charge having ballistic properties comparable to those of a granular charge presents many problems and as yet caseless charges have not captured any significant proportion of the market.
A caseless charge must be designed so that, on ignition, burning will not be limited to the surface of the charge but will occur throughout the mass as in a loose charge. In one method of preparing caseless propellant charges individual grains of propellant explosive composition are compacted either dry or treated with plasticiser or solvent to stick the grains together in a coherent mass. The degree of compaction is intended to be such as to bind the grains sufficiently to prevent breakage in normal handling but to leave the charge sufficiently friable that the grains separate and burn as a loose charge on actuation of the primer which is used to ignite the charge. It is extremely difficult to achieve a balance of the many factors involved so as to produce a satisfactory commercial charge which will burn reliably without leaving a residue which can jam breech mechanism of a nail gun.
It is an object of this invention to provide a nitrocellulose propellant composition which, in granular form, can be compacted to produce an improved unitary compacted caseless propellant charge.
We have found that propellant grains containing a proportion of nitrocellulose having an average nitrogen content 0f 11.0 to 12.0% N by weight can be dry compacted without solvent or adhesives to give improved unitary caseless propellant charges. The charges disintegrate more reliably under the action of the primer to simulate the ballistic effect of a loose charge better than compacted charges hitherto available, and they can be handled in normal use without substantial loss due to breakage.
Accordingly, the propellant explosive composition of this invention comprises, in addition to the usual constituents of a nitrocellulose based propellant explosive, a proportion of low nitrogen nitrocellulose having an average nitrogen content of 11.0 to 12.0 percent by weight. The propellant may conveniently be a single-base propellant based on high nitrogen nitrocellulose having an average nitrogen content of 13.2 to 13.4 percent by weight (guncotton), a double-base propellant containing nitroglycerine and guncotton nitrocellulose or a triple-base propellant containing nitroguanidine, nitroglycerine and guncotton nitrocellulose.
Preferably the proportion of low nitrogen nitrocellulose is within the range 10 to 30 percent by weight of the total composition.
From a further aspect the invention includes a unitary caseless propellant charge comprising compacted grains of the aforedescribed propellant composition. The charge is conveniently cylindrical. If desired for convenience, the charge may be formed with a surface indent to accommodate an appropriate quantity of a priming composition.
The invention also includes a method of making a unitary caseless propellant charge which method comprises dry compacting grains of a propellant composition containing, in addition to the usual constituents of a propellant explosive, a proportion of low nitrogen nitrocellulose having an average nitrogen content of 11.0 to 12.0 percent by weight. Preferably the grains are compacted at a pressure within the range 30,000 to 70,000 psi.
The propellant composition may be prepared in granular form in conventional manner, for example by incorporating into the composition a solvent or plasticiser for the nitrocellulose constitutents to form a dough and shaping the dough into the required grain by moulding or extrusion as a cord which is subsequently divided. The grains may advantageously be porous. The porosity may be achieved in known manner by initially including a removable filler in the composition which is subsequently removed from the grains. For example potassium nitrate crystals may be included and removed by leaching out of the grains with water. The amount of filler is preferably in the range 50 to 200 parts per 100 parts by weight of the composition.
The invention is further illustrated by the following Examples in which all parts and percentages are by weight.
EXAMPLE I
84 parts (as dry) of guncotton nitrocellulose having an average nitrogen content of 13.3% N vetted with 44 parts of ethyl alcohol, 15 parts of low nitrogen nitrocellulose containing an average of 11.6 to 11.8% N, 1 part of diphenylamine, 100 parts of potassium nitrate and 66 parts of diethyl ether were mixed to form an extrudable dough. The dough was extruded through a die to form a cord 1.4 mm diameter which was air dried and cut into disc-shaped grains of approximate thickness 0.32 mm. These grains were stepped in hot water (60°C) to remove most of the potassium nitrate and air dried. They were then tumbled in a pan with fine graphite (average particle size 100 μ) to give them a glaze coating to improve their free running properties and facilitate subsequent feeding to a mould. The composition of the grains was
Guncotton nitrocellulose 84 parts Low nitrogen nitrocellulose 15 parts Diphenylamine 1 part Potassium Nitrate 1 part Graphite 0.4 part
0.35 gram quantities of the grains were pressed in a mould at a pressure of 50,000 psi to form cylindrical pellet charges each having a diameter of 8.85 mm and a thickness of 3.8 mm with a circular primer indent in one of its flat faces of diameter 4.5 mm and 2.0 mm in depth.
The primer indent of each charge was filled with a priming composition consisting of 64 parts of lead styphnate and 36 parts of ground glass slurried in a solution of nitrocellulose. The slurry was dried and covered with a thin protective coating of collodion.
The caseless propellant charge of this Example was tested in an explosively actuated nail driving gun and it burned cleanly and had ballistic properties comparable to a corresponding loose granular charge. It withstood normal rough handling without breakage.
EXAMPLE II
74 parts (as dry) of guncotton nitrocellulose having an average nitrogen content of 13.3% N wetted with 40 parts of ethyl alcohol, 25 parts of low nitrogen nitrocellulose containing an average of 11.8 to 12.0% N, 1 part of diphenylamine, 50 parts of potassium nitrate and 60 parts of diethyl ether were mixed to form an extrudable dough. The dough was formed into grains which were steeped to remove the potassium nitrate and glazed as described in Example I. The composition of the resulting grains was
Guncotton nitrocellulose 74 parts Low nitrogen nitrocellulose 25 parts Diphenylamine 1 part Potassium nitrate 1 part Graphite 0.4 part
0.30 gram quantities of the grains were pressed in a mould at a pressure of 40,000 psi to form cylindrical unitary charges of approximately the same shape and dimensions as the pressed charges of Example I.
When the charges were primed as in Example I and tested in a nail gun they burned cleanly with ballistic properties comparable to those of a corresponding loose charge. They withstood normal rough handling without breakage.
EXAMPLE III
59 parts of guncotton nitrocellulose having an average nitrogen content of 13.3 percent, 20 parts of low nitrogen nitro-cellulose (average N content 11.5 percent) and 1 part of ethyl centralite were slurried with 800 parts of water and 20 parts of nitroglycerine were mixed into the slurry to form a paste. The paste was dried in hot air, mixed with 36 parts of acetone and four parts water and 200 parts of potassium nitrate were added to form a dough which was extruded and granulated as in Example I. The grains were steeped in hot water (60°C) to remove the potassium nitrate and were subsequently air dried and glazed as described in Example I.
The composition of the grains was
Guncotton nitrocellulose 59 parts Low nitrogen nitrocellulose 20 parts Nitroglycerine 20 parts Ethyl centralite 1 part Potassium nitrate 1 part Graphite 0.4 part.
0.25 gram quantities of the grains were pressed in a mould at a pressure of 30,000 psi to form cylindrical unitary charges of approximately the same shape and dimensions as the pressed charges of Example I.
When the charges were primed as in Example I, and tested in a nail gun they burned cleanly with ballistic properties comparable to those of a corresponding loose charge. They withstood normal rough handling without breakage.
EXAMPLE IV
69 parts of guncotton nitrocellulose having an average nitrogen content of 13.3 percent, 15 parts of low nitrogen nitrocellulose containing an average of 11.2 to 11.4% N, and 1 part of ethyl centralite were slurried with 800 parts of water and 15 parts of nitroglycerine were mixed into the slurry to form a paste. The paste was dried in hot air, mixed with 40 parts of acetone and 8 parts of water and 100 parts of potassium nitrate were added to form an extrudable dough. The dough was formed into grains which were steeped to remove the potassium nitrate and glazed as described in Example I.
The composition of the grains was
Guncotton nitrocellulose 69 parts Low nitrogen nitrocellulose 15 parts Nitroglycerine 15 parts Ethyl centralite 1 part Potassium nitrate 1 part Graphite 0.4 part
0.35 gram quantities of the grains were pressed in a mould at a pressure of 60,000 psi to form cylindrical unitary charges of approximately the same shape and dimensions as the pressed charges of Example I.
When the charges were primed as in Example I and tested in a nail gun they burned cleanly with ballistic properties comparable to those of a corresponding loose charge. They withstood normal rough handling without breakage.