Plastic and nonmetallic article shaping or treating: processes – Explosive or propellant article shaping or treating – Rolling to form sheet or rod
Patent
1988-06-16
1990-10-16
Locker, Howard J.
Plastic and nonmetallic article shaping or treating: processes
Explosive or propellant article shaping or treating
Rolling to form sheet or rod
86 201, 86 2012, 1491096, 264 31, 264 33, C06B 2100, D03D 2300, D03D 4300, F42B 300
Patent
active
049632965
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to a process for the preparation of propellant charge powder, in particular of dibasic POL powder from a raw powder mixture moistened with water.
BACKGROUND OF THE INVENTION
In known processes for the preparation of propellant charge powders such as a dibasic POL powder from a moist raw powder, raw powder mixture is cutomarily kneaded by means of calander rollers for the purpose of homogenizing and gelatinizing or plasticizing the mixture but this can only be carried out batch-wise, not continuously. A sheet is typically formed on one of the two rollers of the calander, and this sheet must be kneaded to completion and then completely removed before a fressh batch of powder mixture can be introduced.
It is also known to carry out the kneading process continuously by means of an extruder containing kneading elements. In that case, the kneading process may be immediately followed by the moulding process within the same extruder without a break. This means that the raw powder mixture is directly converted into powder strands. It is, however, difficult to feed the correct amount of raw material into the extruder, especially if the material is made moist with water, and an even more critical difficulty is that when the powder mass is kneaded in the extruder, it is subjected to a considerable amount of heat and mechanical stress inside a closed space. This constitutes a considerable safety risk and if spontaneous ignition occurs, this inevitably results in an explosion.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a process for continuous and safe production of a propellant charge.
In the process according to this invention, an open set of cooperating paired shearing rollers of known kind is used for kneading powder. The kneading process takes place continuously on these rollers. The raw powder mixture is continuously introduced near one end of the shearing rollers and is gradually transported to the other end of these rollers in the course of kneading. A sheet is formed on one of the two rollers of the set and this sheet may be continuously removed at the other end, e.g., by continuously cutting off a strip of the sheet. Since the set of shearing rollers is open, spotaneous ignition of the powder mixture can at worst result in burning of the sheet but not in an explosion. The difficulties of dosing the how rate of powder mixture supplied to the shearing rollers, especially when the mixture is moistened with water, are eliminated, while the kneading process is made continuous. This enables the rollers to be operated and observed from a distance so that the safety of processing the material is considerably enhanced. Lastly, the removal of water from the raw mixture kneaded in the set of open rollers does not give rise to any difficulties, in contrast to the process of kneading in a closed extruder. The granulating process may preferably carried out immediately after the kneading process, for example by punching granulate out of the sheet by means of a granulating head as the sheet leaves the rollers at the discharge end, and then removing the granulate.
For moulding the granulate, an extruder is advantageously used in combination with the process according to this invention. The granulate may be continuously introduced into the extruder as it is formed. The entire production process from introduction of the raw powder mixture to formation of the powder strands is then completely continuous. Kneading can subject the powder mixture to severe heating and mechanical stress, but is not required and should not occur, in the extruder used for the moulding process, hence no particular safety problems are encountered. It is particularly advantageous that the granulate can be directly transferred from the shearing rollers to the extruders as it is formed and while it is still hot. Long heating zones are therefore not required in the extruder, also a very short extruder may be used. The quantity of propellant charge powder enclo
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Helmich Wolfgang
Knobloch Jurgen
Miehling Wolfgang
Niedermeier Gunther
Pausch Helmut
Locker Howard J.
WNC-Nitrochemie GmbH
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