The flow of granular magnesia

Flow Equations for Free-Flowable Particle Fractions of Sorbitol for Direct Compression: An Exploratory Multiple Regression Analysis of Particle and Orifice Size Influence

Highlights

Abstract

Flowability is among the most important properties of powders, especially when fine particle size fractions need to be processed. In this study, our goal was to find a possibly simple but accurate mathematical model for predicting the mass flow rate for different fractions of the pharmaceutical excipient sorbitol for direct compression. Various regression models derived from the Jones–Pilpel equation for the prediction of the mass flow rate were investigated. Using validation with experimental data for various particle and hopper orifice sizes, we focused on the prediction accuracy of the respective models, i.e., on the relative difference between measured and model-predicted values. Classical indicators of regression quality from statistics were addressed as well, but we consider high prediction accuracy to be particularly important for industrial processing in practice. For individual particle size fractions, the best results (an average prediction accuracy of 3.8%) were obtained using simple regression on orifice size. However, for higher accuracy (3.1%) in a unifying model, valid in the broad particle size range 0.100–0.346 mm, a fully quadratic model, incorporating interaction between particle and orifice size, appears to be most appropriate.

Starch flow behavior alone and under different glidants action using the shear cell method

The objective of this work was to analyze the flow behavior of a commonly used filler (pregelatinised starch) and the effect of two of the most used lubricants (talc and colloidal silicon dioxide). The studies were carried out according to the conventional methods (Angle of Repose, Bulk and Tapped densities and from these the Compressibility Index) and shear cell methods (Brookfield Powder Flow Tester apparatus) described in European Pharmacopeia (Ph. Eur.). The results showed some surprising and unexpected values for the flow behavior of this filler under influence of the methods and the used glidants. Regarding pure starch and mixtures containing talc, the flow behavior was similar between them and the Flow Index (ff_c) values varied between 1.8 and 4 (very cohesive and cohesive) as consolidation stress (σ₁) increased. In this case, the glidant effect was not observed. However, for the mixtures of starch with colloidal silicon dioxide this effect was observed providing Flow Index (ff_c) values between 2.6 and 8.9 (cohesive and easy-flowing) as consolidation stress (σ₁) increased. Other parameters that are also used to characterize flow properties, more specifically, within silos, chutes and hoppers, such as effective angle of internal friction (φe), effective angle of wall friction (φx), critical arching and critical rathole values, provided similar information. Based in the obtained results from all tests it can be said that the talc did not induce improvement on the starch flow behavior in the used conditions in opposition to the effect produced by colloidal silicon dioxide.HighlightsExample 1. A good flowability of powders is needed in order to be compressed/filled;Example 2. The overcome the poor flow it is usual to use glidants;Example 3. CSD improved the pregelatinised starch (Starch 1500®) flow;Example 4. Talc do not have relevant effect in the pregelatinised starch (Starch 1500®) flow;Example 5. Powder FlowTester method showed more complete and consistent results.

Contribution to the methodology of optimization and in-process control of some physical properties of pharmaceutical bulk substances and granulates

Many experts consider drug analysis exclusively as a chemical measuring technique. In the pharmaceutical industry, physical and physico-chemical parameters form an integrated part of the quality specification, because they play an essential role both in quality assurance and in the technical and economic aspects of production on the commercial scale. Such physical and physico-chemical properties are analysed by special, non-chemical methods. In their programme of systematic research in this field, the authors have elaborated new methods to test some essential properties of powders and granulates used in the production of compressed tablets. The following test and production methods have been developed: (i) the determination of flowing-sliding characteristics of granulates based on the measurement of the mass-flow (g s(-1)) and mass-flow density (g s(-1) cm(-2)); (ii) the determination of optimum granulometric parameters with regard to tablet diameter; (iii) the direct determination of the temperature-dependent equilibrium vapour pressure; and (iv) the compression of tablets under controlled temperature.

Preliminary evaluation of dika fat, a new tablet lubricant

Dika fat, a solid vegetable oil extracted from the kernels of Irvingia gabonensis var excelsia has been evaluated as a lubricant on the basis of its effect on the flow rate of granules, disintegration time and dissolution rate of tablets. The fat shows a maximal effect on flow at a concentration of 2.5% w/w. It produces better disintegration and dissolution profiles than magnesium stearte at all concentrations tested. The indication is that there is less degradation of aspirin in tablets containing this oil than there is in tablets containing magnesium stearate. The use of Dika fat (m.p. 39--40 degrees C) eliminates the hydrogenation step often necessary for vegetable oils.

The action of colloidal silicon dioxide as a glidant for lactose, paracetamol, oxytetracycline and their mixtures

Anomalies are observed in some of the physical and mechanical properties of mixtures of lactose, paracetamol and oxytetracycline when small amounts of colloidal silicon dioxide are added to them. Owing to its differing propensities to coat the particles of the host powders, the silicon dioxide acts as a glidant for the lactose and paracetamol, but as an antiglidant for the oxytetracycline.

Application of powder failure testing equipment in assessing effect on glidants on flowability of cohesive pharmaceutical powders

Powder failure testing equipment was used successfully to study the effect of glidants on the flowability of two cohesive pharmaceutical powders, lactose and calcium hydrogen phosphate, using the flow factor as the flowability parameter. Fine silica, magnesium stearate, and purified talc were investigated as glidants; for each host powder-glidant mixture, an optimum concentration of glidant was observed beyond which no further increase in flowability occurred. The order of efficiency of glidants for both host powders was fine silica greater than magnesium stearate greater than purified talc. The mode of action of the three glidants is discussed.