Die Face Pelletizing in the pharmaceutical industry
[News vom: 24.03.2011]
Today the pharmaceutical industry starts to discover the possibilities
of hot melt extrusion technology and its associated downstream
processes. Thereby strand pelletizing, calendering and spinning are some
of the downstream processes which are under investigation. A main
disadvantage of these technologies is the need of several additional
processes like milling, sieving, spheronization, etc. to achieve
appropriate product quality.
A
promising downstream technology avoiding this limitation is die face
pelletizing, as used in the plastics industry since many years. One of
our research projects deals with the adaption of this technology for
pharmaceutical manufacturing processes. Goal of this project is the
formation of pellets in one production step which can be directly
transferred to a subsequent process unit, for example the capsule
filling process.
The applied die face pelletizing system comprises a knife which rotates directly in front of a die plate. A blend of an active ingredient, a polymeric matrix and several processing aids is heated and melted inside the extruder and is then extruded through the die into a strand. This strand is cut immediately after the outlet of the die plate by the rotating knife and formed into small pellets. The size and shape of the pellets are determined by the properties of the molten mass, the rotation speed of the knife, the cooling and the way of the air flow inside the pelletizing system.
Several challenges have to be overcome to obtain pellets with the desired properties. The accuracy of the feeding systems for the dosing of raw materials, the cooling regime of the die cut system, the inline process control (PAT) and the selection of the screw configuration are only some factors that have to be taken into account. Another challenge is the development of an adequate formulation since not every polymeric matrix can be processed with die face pelletizing technology. The processability of the extrudate depends on different parameters, like for example glass transition temperature, viscosity, stickiness and elasticity of the materials used.
The applied die face pelletizing system comprises a knife which rotates directly in front of a die plate. A blend of an active ingredient, a polymeric matrix and several processing aids is heated and melted inside the extruder and is then extruded through the die into a strand. This strand is cut immediately after the outlet of the die plate by the rotating knife and formed into small pellets. The size and shape of the pellets are determined by the properties of the molten mass, the rotation speed of the knife, the cooling and the way of the air flow inside the pelletizing system.
Several challenges have to be overcome to obtain pellets with the desired properties. The accuracy of the feeding systems for the dosing of raw materials, the cooling regime of the die cut system, the inline process control (PAT) and the selection of the screw configuration are only some factors that have to be taken into account. Another challenge is the development of an adequate formulation since not every polymeric matrix can be processed with die face pelletizing technology. The processability of the extrudate depends on different parameters, like for example glass transition temperature, viscosity, stickiness and elasticity of the materials used.
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