Residence time distribution of a pharmaceutical grade polymer melt in a single screw extrusion process

Abstract

a b s t r a c tThe residence time distribution (RTD) of a flowing polymer through a single screw extruder was studied. This extruder allows injecting supercritical carbon dioxide (scCO 2 ) used as physical foaming agent. The tested material is Eudragit E100, a pharmaceutical polymer. RTD was measured at various operating conditions and a model describing RTD has been developed. High screw speed or high temperature implies short residence time, but these parameters do not have the same effect on polymer flow. In the flow rate range studied, scCO 2 has no significant influence. A mathematical model consisting of a plug flow reactor in series with a continuous stirred tank reactor (CSTR) cross-flowing with a dead volume fitted well the experimental data.

Optimising Drug Solubilisation in Amorphous Polymer Dispersions: Rational Selection of Hot-melt Extrusion Processing Parameters

“…In agreement with literature, the average residence time decreased significantly upon elevation in both temperature and screw speed (33)(34)(35). Among all investigated temperature-screw speed (°C-rpm) combinations, 110°C with 20 rpm resulted in dramatically prolonged mean residence time, approximately 3∼20 folds longer than that of the others.…”

“…This local temperature rise may then reflect local viscosity fluctuations that could subsequently affect the τ readings; thus, greater standard deviations may be observed for mean torque values at higher screw speeds (41)(42)(43). Therefore, for the FD-EPO melt inside the extruder, a decrease in residence time and increase in average torque would be expected with increasing screw speed, and the same should hold true for elevations in processing temperature (35). Moreover, the similarity in the mean residence time and the torque values between 140°C and 150°C may be attributed to a similar melt viscosity of the system at these two temperatures, regardless of the applied screw speed.…”

Use of supercritical CO2‐aided and conventional melt extrusion for enhancing the dissolution rate of an active pharmaceutical ingredient

“…[9] This work was also completed by the study of the influence of scCO 2 on the polymer flow of Eudragit E100 in the extruder. [10][11][12] Lipid soluble chemicals, such as carvedilol (CAR), are almost insoluble in water. Therefore, they are poorly absorbed through the gastrointestinal tract.…”

Método Simples Para Determinar Distribuição De Tempo De Residência De Polímeros Em Extrusora a Partir De Medidas De Luminância

“…Os mesmos apresentam um perfil que indica a retenção de uma fração considerável de material no interior da extrusora por um tempo anormalmente longo. Fazendo uso destas curvas, Equação 7 e Figura 4, foram determinados graficamente os tempos médios de residência (τ) do PP na extrusora: 30rpm ô = 283 s; 38rpm ô = 258 s; e 48rpm ô = 205 s. Como era esperado, o aumento da velocidade de rotação da rosca ocasiona a redução de τ, conforme já verificado anteriormente por Nikitine et al [15]. O aumento da velocidade de rotação da rosca leva a um aumento da vazão e da taxa de cisalhamento, o que contribui para a redução de τ e incremento da mistura do fundido.…”

“…A presença destas zonas causa o aparecimento de longas caudas nas curvas E(t) e F(t), i.e., uma pequena fração do marcador sai da extrusora somente depois de decorrido um longo período de tempo [2,15]. Embora a RTD tenha sido determinada com a extrusora em regime permanente, existem modelos matemáticos para obter a RTD durante o fluxo em regime transiente zonas nas quais o polímero apresenta-se inicialmente sólido (zona de alimentação), ocorrendo a mistura apenas após a fusão.…”