GB1567918A

GB1567918A - Method for preparing smikeless nitrocellulose powders

Info

Publication number: GB1567918A
Application number: GB4156776A
Authority: GB
Original assignee: Korea Explosives Co Ltd
Current assignee: Hanwha Corp
Priority date: 1976-10-06
Filing date: 1976-10-06
Publication date: 1980-05-21

Description

(54) A METHOD FOR PREPARING SMOKELESS NITROCELLULOSE POWDERS (71) We, KOREA EXPLOSIVES CO., LTD., a Korean Body Corporate, of 12-1, Seosomoon-Dong, Chung-Ku, Seoul, Korea, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method for the preparation of smokeless nitrocellulose powders, particularly for small arms.

Hitherto, a batch process has been proposed for preparing such explosive powders which involves introducing nitrocellulose into a granulator containing a large amount of water so as to obtain a nitrocellulose slurry; adding a solvent (e.g. an appropriate organic solvent such as ethyl acetate - preferably with stabilizer added thereto) to the mixture with stirring to produce a cellulose lacquer in water; dividing or cutting the lacquer into small balls or other particulate forms while pouring in an aqueous solution of gum arabic; and then removing the solvent by evaporation to increase the density of the product.

In this process, however, the yield of the resulting particles is poor. Moreover the further step of impregnating the particles with nitroglycerine is essential to improve the ballistic characeristics thereof.

According to the present invention there is provided a method for preparing a smokeless nitrocellulose powder comprising: dissolving nitrocellulose, nitroglycerine and a stabilizer in an organic solvent to give a lacquer solution of a viscosity of 5,000 to 10,000 sec as measured according to JIS-K-4812 at 25%.

introducing the lacquer solution into an aqueous solution containing a coagulation retardant; and granulating the resulting mixture.

This method can be performed by subjecting a mix of nitrocellulose, nitroglycerine and stabilizer to kneading with the solvent in a suitable kneader until a high viscosity 5,000 to 10,000 sec as defined above lacquer substantially free from water is obtained; introducing said lacquer into water containing a coagulation retardant such as gum arabic; and then cutting and granulating the lacquer into balls or other particulate forms.

In following the method, adjustment of the viscosity of the lacquer is possible. In other words, a viscosity below 5,000 sec. can be increased by adding further nitrocellulose and nitroglycerine (in so far as the desired formulation of the composition allows), while a viscosity over 10,000 sec. can be decreased by sufficient stirring with a small amount of water.

In order to increase the yield of powders obtained by employing the high lacquer viscosity required by the invention, it is preferable to use a special granulating kettle as described below.

For a better understanding of the invention and to give an Example of how the same may be ut into effect, reference will now be made, by way of an embodiment of the granulating kettle, to the accompanying drawings, in which: Figure la shows a longitudinal section view of a granulating kettle for use in a method according to the invention; Figure ib shows a plan view of the kettle of Figure la; Figures 2a and 2b show respectively a side elevation and a plan view of blades fitted to a driving axle in the centre of the kettle of Figures la and lb; Figure 2c shows, on a larger scale, a partial sectional view of one of the blades in Figure 2b taken on the line A-A; and Figure 3 shows a diagrammatic curve illustrating the relationship between rotational speed of the blades and the temperature of the kettle of the previous Figures during the granulation step of an embodiment of the method according to the present invention.

Referring to Figures la to 2a, the granulating kettle 1 has a bottom 2 which is inclined and is curved where it meets the wall. The kettle has four agitator blades 3 (which can be driven by means of a suitable device-not shown) and baffle plates 4 secured at right angles to the interior of the side wall at a suitable height in the kettle.

Each of the blades 3 is mounted on a central axle extending into the kettle 1. Each blade is tilted at an angle of 40 to the horizontal where it meets the axle, and is curved over such that its outer end is horizontal. The blades have sharp edges 5 on one side thereof so that cutting or dividing of the lacquer is simply carried out to achieve granulation.

The inclined and curved bottom 2 is provided in order to facilitate collecting and withdraw ing the powder after completing the granulating step.

The method provided by the invention will now be described in more detail with reference to the following example, by which, however, the invention is not limited.

EXAMPLE. A granulating kettle as described above and having the following conditions was used: Diameter : 1200 mm.

Height : 1300 mm.

Total length of agitator : 400 mm.

100 Kg. of nitrocellulose containing 13.5% nitrogen was poured into a conventional kneader and then water slowly added thereto until the water content in the resulting mix was 30%. A lacquer solution was prepard by adding to this mix with agitation 300 Kg of ethyl acetate in which 14 Kg. of nitroglycerine and 0.5 Kg. of diphenylamine had been dissolved in advance.

Thereafter, the viscosity (as herein defined) of the resulting lacquer solution was checked so as to be 5,000 to 10,000 sec. After checking the viscosity, the lacquer solution was slowly poured by means of compressed air from the kneader into an aqueous solution in the kettle previously prepared by dissolving 15 Kg. of gum arabic, 5 Kg. of sodium sulfate and 0.1 Kg. of calcium carbonate in 1000 Kg. of water. Preferably, during this operation, the temperature of the kettle is maintained at 25"C.

The resultant mixture was then granulated. The rotation speed of the blades as well as the temperature of the kettle were controlled as illustrated in Figure 3. In this manner cured particles were obtained from which all of the solvent had evaporated.

More than 90 per cent of the particles formed by this process had a grain size of 20 to 30 mesh. Furthermore the distribution within these limits was bell-shaped.

WHAT WE CLAIM IS: 1. A method for preparing a smokeless nitrocellulose powder comprising: dissolving nitrocellulose, nitroglycerine and a stabiliser in an organic solvent to give a lacquer solution of a viscosity, of 5,000 to 10,000 sec as measured according to JIS-K-4812 at 25%, introducing the lacquer solution into an aqueous solution containing a coagulation retardant, and granulating the resulting mixture.

2. A method according to claim 1 wherein the organic solvent is ethyl acetate.

3. A method according to claim 1 or 2 wherein the coagulation retardant comprises gum arabic.

4. A method according to claim 1 substantially as described in the Example.

5. A smokeless nitrocellulose powder when prepared by a method according to any preceding claim.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

taken on the line A-A; and Figure 3 shows a diagrammatic curve illustrating the relationship between rotational speed of the blades and the temperature of the kettle of the previous Figures during the granulation step of an embodiment of the method according to the present invention.

Referring to Figures la to 2a, the granulating kettle 1 has a bottom 2 which is inclined and is curved where it meets the wall. The kettle has four agitator blades 3 (which can be driven by means of a suitable device-not shown) and baffle plates 4 secured at right angles to the interior of the side wall at a suitable height in the kettle.

Each of the blades 3 is mounted on a central axle extending into the kettle 1. Each blade is tilted at an angle of 40 to the horizontal where it meets the axle, and is curved over such that its outer end is horizontal. The blades have sharp edges 5 on one side thereof so that cutting or dividing of the lacquer is simply carried out to achieve granulation.

The inclined and curved bottom 2 is provided in order to facilitate collecting and withdraw ing the powder after completing the granulating step.

The method provided by the invention will now be described in more detail with reference to the following example, by which, however, the invention is not limited.

EXAMPLE. A granulating kettle as described above and having the following conditions was used: Diameter : 1200 mm.

Height : 1300 mm.

Total length of agitator : 400 mm.

100 Kg. of nitrocellulose containing 13.5% nitrogen was poured into a conventional kneader and then water slowly added thereto until the water content in the resulting mix was 30%. A lacquer solution was prepard by adding to this mix with agitation 300 Kg of ethyl acetate in which 14 Kg. of nitroglycerine and 0.5 Kg. of diphenylamine had been dissolved in advance.

Thereafter, the viscosity (as herein defined) of the resulting lacquer solution was checked so as to be 5,000 to 10,000 sec. After checking the viscosity, the lacquer solution was slowly poured by means of compressed air from the kneader into an aqueous solution in the kettle previously prepared by dissolving 15 Kg. of gum arabic, 5 Kg. of sodium sulfate and 0.1 Kg. of calcium carbonate in 1000 Kg. of water. Preferably, during this operation, the temperature of the kettle is maintained at 25"C.

The resultant mixture was then granulated. The rotation speed of the blades as well as the temperature of the kettle were controlled as illustrated in Figure 3. In this manner cured particles were obtained from which all of the solvent had evaporated.

More than 90 per cent of the particles formed by this process had a grain size of 20 to 30 mesh. Furthermore the distribution within these limits was bell-shaped.

WHAT WE CLAIM IS: 1. A method for preparing a smokeless nitrocellulose powder comprising: dissolving nitrocellulose, nitroglycerine and a stabiliser in an organic solvent to give a lacquer solution of a viscosity, of 5,000 to 10,000 sec as measured according to JIS-K-4812 at 25%, introducing the lacquer solution into an aqueous solution containing a coagulation retardant, and granulating the resulting mixture.
2. A method according to claim 1 wherein the organic solvent is ethyl acetate.
3. A method according to claim 1 or 2 wherein the coagulation retardant comprises gum arabic.
4. A method according to claim 1 substantially as described in the Example.
5. A smokeless nitrocellulose powder when prepared by a method according to any preceding claim.