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Browsing by Subject "twin screw granulation"

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  • Hietala, Tarja (2017)
    Twin screw granulation (TSG) has gained considerable interest as a continuous wet granulation method in the pharmaceutical industry and has been studied the most. However, there is still lack of understanding how continuous granulation affects the material compaction behavior even though it has been noticed in several dry and batch wet granulation studies that the granulation process has an influence on the final tablet strength. Thus, studies on the material compactability and tabletability after continuous wet granulation are relevant for the overall understanding of twin screw granulation process and its effect on material behavior in tableting. Hence, the main objective of this study was to investigate the influence of continuous twin screw granulation on the compactability and tabletability of commonly used excipients. Additionally, the impact of binder on the compaction behavior of materials was examined. Furthermore, the suitability of two "loss in compressibility" models i.e. the Unified Compaction Curve (UCC) model and a porosity model to predict the loss in tablet strength after twin screw granulation and for the materials used was assessed. Earlier, the models have been applied to dry and batch wet granulations only. Full factorial design of three variables (binder type, binder addition method and the number of kneading elements) with two levels was conducted for the ConsiGma1 twin screw granulation of formulations containing microcrystalline cellulose (MCC), mannitol or anhydrous dicalcium phosphate (DCPA) as the main excipient and polyvinylpyrrolidone (PVP) or hydroxypropyl cellulose (HPC) as binder. Magnesium stearate was added as lubricant after granulation prior to tableting. In addition to the full factorial design, granulation with PVP, dry binder addition and four kneading elements was repeated for each main excipient. In total this made 27 experiments. The granules were dried and milled after granulation and all the batches were tableted. Additionally, all the formulations were direct compressed in order to be able to detect the change in compactability and tabletability after granulation. Torque of the granulation was determined as well as bulk density and particle size distribution of the granules. Additionally, the tensile strength and porosity of the tablets were analysed. Tabletability and compactability were determined based on the compaction pressure and the obtained tensile strength and porosity values of the tablets. Furthermore, parameters (PWG, TWG and εWG) describing the loss in compressibility models were calculated. MCC experienced loss in compactability and tabletability after twin screw granulation due to hornification effect. On the other hand, the compaction behavior of mannitol improved due to the formation of porous granules. The compactability of DCPA decreased and the tabletability increased. However, the change was only moderate presumably due to brittle nature of DCPA. Additionally, the binder type had an effect of the compaction behavior of the materials, PVP producing stronger tablets compared with the less hydrophilic HPC. However, the binder addition method played only a small role in modifying the compaction behavior. The UCC model was applicable to MCC as loss in tabletability was detected. Thus, the model can be used to predict tablet tensile strength when MCC is granulated with twin screw granulator. Additionally, the UCC model can be used to design the granulation process to achieve a target tensile strength based on small scale preliminary studies thus reducing the resources needed for case-studies. However, the UCC model was not feasible to mannitol and DCPA because they experienced improvement in tabletability after twin screw granulation. The porosity model was applicable to MCC and DCPA but not to mannitol as it showed improvement in compactability. The porosity model described the loss in compactability of MCC only moderately due to lack of tensile strength data points and the linearity of the tensile strength-porosity relationship. However, the model described well the loss in compactability of DCPA at tablet porosities achieved with compaction pressures used in industry. As a conclusion, the results demonstrate that twin screw granulation can have a significant impact on the final tablet strength and that the compaction behavior of the formulation can change either way depending on the used materials. Furthermore, the small influence of the binder addition method on the tablet strength indicates that the time consuming binder dissolving process step can be excluded from the tablet production chain enabling continuous manufacturing with twin screw granulation.
  • Häkkinen, Aino (2016)
    There is a growing interest towards continuous manufacturing in pharmaceutical industry. When considering solid dosage form manufacturing and continuous wet granulation, twin screw granulation is the most studied technology. In spite of this, process knowledge is not as comprehensive as it is for batch granulation technologies such as high shear granulation. One problem with twin screw granulation seems to be bimodal and broad particle size distribution of granules. Specific causes of bimodal distribution and the ways to possibly gain unimodality either in granulation step or via dry milling are not fully understood. The purpose of this study was to optimize the ConsiGma25 continuous twin screw wet granulation process and study dry milling as a possible way of gaining unimodal particle size distribution in order to optimize particle size for tablet compression purposes. One aim was also to compress tablets from the obtained twin screw granules and evaluate the quality against high shear and direct compressed tablets of same formulation. Central composite circumscribed design was used as a design of experiments for twin screw wet granulation process. Factors (powder feed rate, screw speed, liquid to solid ratio (L/S ratio) and mill screen size) were varied in two levels. In total, 29 experiments were conducted. Tablet compression design was fractional as only 11 experiments from the twin screw granulation design were tableted. High shear granulation was conducted with Diosna P-1/6 using three different L/S ratios. All of these batches were compressed to tablets. Also direct compression was carried out. Formulation used had ibuprofen as active pharmaceutical ingredient, mannitol and MCC as fillers, HPC as binder and croscarmellose sodium as disintegrant. Lubricant, sodium stearyl fumarate, was blended to granules before tablet compression. Torque was measured during granulation in order to evaluate equilibration of the twin screw granulation process. It stabilized quickly and stayed stable after parameter changes and increased as L/S ratio and barrel fill rate increased. Particle size distribution and flowability of granules were analysed and tablets were analysed according to European and United States pharmacopoeias. Also tensile strengths and compactibilities were evaluated. Particle size distributions of unmilled twin screw granules were bimodal and broad. After dry milling, QicPic dynamic image analysis results showed unimodal particle size distributions for all experiments whereas Mastersizer laser diffraction analysis showed more unimodal distributions for experiments milled with smaller mill screen sizes. Mill screen size had the largest effect on particle size and as increased mill screen size increased particle size. Results showed that dry milling was a way to optimize particle size distribution for tablet compression purposes. Also flowability of formulation and process parameters needed to be optimized as granulation parameters had an effect on particle size and manufacturability was enhanced with better flowing formulation compared to previous study. Knowledge of the influence of L/S ratio, screw speed and powder feed rate, on granule size was gained. The effect of these process parameters varied depending whether d10, d50 or d90 was measured and particle size analysis method used. Increased L/S ratio and screw speed increased granule size as increased powder feed rate decreased it. Twin screw tablets showed higher tensile strengths and better compactibility compared to both high shear tablets and direct compressed tablets. Twin screw tablets showed also faster dissolution compared to direct compressed tablets probably due to of lower compression force. Mill screen size had the largest effect on dissolution properties of the twin screw tablets. When larger mill screen size was used, dissolution was slower due to larger particle size. Also increased powder feed rate made dissolution rate slower due to higher fill rate of the barrel. In other tablet properties analysed, no significant differences were seen between different twin screw experiments or between twin screw tablets and direct compressed tablets. All of the twin screw tablets and direct compressed tablets fulfilled the requirements of European and United states pharmacopoeia. As a conclusion, continuous granulation process was successfully optimized and high quality tablets resulted showing especially the effect of dry milling on granule size and shape as well as on tablet properties.