Method and apparatus to prepare monobasic propellant charge powd

Details Method and apparatus to prepare monobasic propellant charge powd Method and apparatus to prepare monobasic propellant charge powd

1990-12-13

1993-02-16

Nelson, Peter A.

Plastic and nonmetallic article shaping or treating: processes

Explosive or propellant article shaping or treating

Extrusion to form sheet or rod

C06B 2100

Patent

active

051868717

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a method of preparing monobasic propellant charge powders with alcohol and ether as solvents, making use of an extruder. It also relates to an apparatus for making monobasic propellant charge powders of the kind mentioned which apparatus comprises at least one screw supported in a housing and an extruder head, including at least one die, arranged at the discharge end of the housing and having a cooling means to cool the propellant charge powder mixture which is located at the discharge end.
It is known from the prior art to prepare propellant charge powders by resorting to an extruder DE-OS 32 42 301, for instance, discloses an apparatus with which the propellant charge powder material is mixed and kneaded by making use of a double shaft screw extruder. The apparatus comprises a cooling means to dissipate the heat resulting from the extrusion and to adjust a certain temperature profile in the powder mixture throughout the length which the mixture passes in the extruder. In the case of monobasic powders the temperature should be highest at the discharge end. An extruder comprising a cooling means for the production of propellant charge powders is known also from DE-OS 34 07 238.
The use of solvents is required in the preparation of monobasic propellant charge powders. Alcohol, acetone, and ether belong to the customary solvents chosen. The nitrocellulose used normally is moist with alcohol. Where monobasic propellant charge powders are prepared in the extruder so far only alcohol/acetone are added as solvents. Ether has a very low boiling point. Since heat is set free in the extruder, the ether may evaporate and, as a consequence, the powder mixture exiting from the extruder contains ether bubbles throughout. The ether bubbles disturb the homogeneity of the pulverous substance, result in a porous surface of the powder strands, and consequently yield a product of inadequate quality. Furthermore, the exiting ether-air mixture presents quite a considerable hazard. For this reason the use of alcohol/ether as solvents was precluded until now although these solvents do have marked advantages as compared to alcohol/acetone. For instance, it is much more difficult to remove acetone from the propellant charge mixture than ether. Longer drying times under vacuum and prolonged watering are needed, for example. Besides, monobasic propellant charge powders prepared with acetone have a tendency to be brittle when cold at temperatures below freezing.
It is, therefore, an object of the invention to indicate a method and an apparatus of the kind defined initially which, while being of simple structure and operationally safe to handle, permit the preparation of high-quality monobasic propellant charge powders with alcohol and ether as solvents by making use of an extruder.
The method according to the invention, devised to solve the problem posed, is characterized in that the pulverous substance is cooled before it leaves the extruder.
The method according to the invention has a number of distinct advantages. The occurrence of ether bubbles can be avoided reliably by the fact that the propellant charge powder is cooled before it is discharged from the extruder.
It must be taken into account with the method of the invention that part of the kneading energy in gelatinizing nitrocellulose is converted into heat. Therefore, the material in the extruder usually is heated to a temperature above the boiling point of ether (35.degree. C.). If the formation of ether bubbles at the powder surface is to be avoided, the temperature of the propellant charge powder mixture having passed the die must not be much higher than the boiling point. In accordance with the invention only that part of the equipment is cooled at which the occurrence of ether bubbles is especially critical which is the outlet zone or discharge end of the extruder. In that area, therefore, the temperature of the pulverous mass is reduced to the boiling point of ether or below that point.
The invention is based on the finding that monobasic prop

REFERENCES:
patent: 3855373 (1974-12-01), Swotinsky et al.
patent: 4102953 (1978-07-01), Johnson et al.
patent: 4120920 (1978-10-01), Cougoul et al.
patent: 4298552 (1981-11-01), Gimler
patent: 4326901 (1982-04-01), Leneveu et al.

Affiliated with

Also associated with

Rating

Method and apparatus to prepare monobasic propellant charge powd does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method and apparatus to prepare monobasic propellant charge powd, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus to prepare monobasic propellant charge powd will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2146586