Roller Compaction Process Research Articles

Roller compaction: Application of an in-gap ribbon porosity calculation for the optimization of downstream granule flow and compactability characteristics.

This paper reports the use of an in-gap ribbon porosity calculation for the optimisation of roller compaction ribbon parameters in order to control downstream granule and tablet properties for a typical pharmaceutical formulation. The study demonstrates the effect of changes to roll speed and roll gap on the relative level of ribbon compaction for ribbons with equivalent in-gap porosities. It is demonstrated that in-gap ribbon porosity can be applied to enable optimization of the downstream granule processability characteristics for a typical pharmaceutical formulation and an understanding of the control space of a roller compaction process.

Systematical approach of formulation and process development using roller compaction

The roller compaction process has gained heightened interest in the pharmaceutical industry. In this review, common excipients and equipment used for dry granulation are described. Roller compaction process parameters and their impact on the critical quality attributes of the final product, as well as evaluation methods for roller compaction product such as ribbons and granules, are discussed. Overall, a systematical approach of formulation and process development has been proposed for excipient selection, critical process parameter identification, and necessary tests.

Micro-manufacturing of micro-scale porous surface structures for enhanced heat transfer applications: an experimental process optimization study

Integrated and compact products necessitate the use of advanced thermal management systems with reduced footprint and cost as well as increased efficiency. Micro-scale, porous and modulated (i.e. channels, pyramids, etc) surfaces offer increased surface area for a given volume and lead to two-phase heat transfer conditions with efficiency enhancements up to 300%. Such surfaces made of copper powders were demonstrated to be quite effective by several researchers after they were produced in controlled lab environments. Similar surfaces made of high temperature resistant materials such as stainless steel, nickel and titanium can also be used in fuel processor, SOFC and PEM fuel cell applications as bipolar/interconnect plates. However, their fabrication under mass-production conditions for marketable and cost-effective products requires well-established process parameters. In this study, warm compaction of copper powders onto thin copper solid substrates was experimented with under different compaction pressure (15–50 MPa), temperature (350–500 °C) and surface geometry (flat, large and small channeled) parameters using a design of experiment (DOE) approach to determine the proper process conditions. Porosity and bonding strength of compacted samples were measured to characterize their feasibility for compact and/or micro-scale heat/mass transfer applications. Results showed that a minimum 350 °C temperature and 15 MPa pressure level is necessary to obtain sound porous and micro-channeled surface layers. It was also found that at higher pressure levels (50 MPa), fabrication of micro-scale surface structures is highly repeatable with enhanced bonding strength characteristics. DOE findings will be used to establish proper process conditions to produce such porous surfaces using a continuous roll compaction process in the future.

Cost Effective Pure Titanium with High Mechanical Response by Oxide Dispersion Strengthening

Titanium (Ti) alloys are possible to be applied to various products such as aircraft, automotive and motor cycles industries because of their weight reduction effect, superior mechanical responses and high corrosion resistance. Ti-6Al-4V (Ti64) is one of the most common Ti alloys used in structural components. It shows high tensile strength of 900MPa or more. On the other hand, its applications are limited to high-performance products because of both its poor plastic formability and high cost due to the addition of vanadium element and difficult melting process. In this study, the highly strengthened pure titanium has been developed using cheap sponge Ti powders via repeated plastic deformation, avoiding the melting process. The main strengthening mechanism of this material is the oxide dispersion strengthening (ODS) by the in-situ formed TiO 2 fine dispersoids during the repetitive plastic deformation of sponge Ti powders. Roll-Compaction (RCP) process, consisting of cold powder rolling and fragmentation, was employed to induce much plastic strain into the matrix of the Ti powders. Subsequently, the grain refinement was also obtained to enhance the mechanical properties. The extruded sponge Ti powder composites reinforced with TiO 2 particles indicated high tensile strength of 640 MPa and enough elongation of 17.2% after RCP process with 20 cycles.

純チタンの結晶粒微細化と酸化物分散強化

Titanium (Ti) alloys are applied to various products used in the aircraft, automotive and motor cycles industries due to their high specific strength. Ti-6Al-4V (Ti64) is one of the most general Ti alloys, and shows superior mechanical properties i.e. density of 4.43 g/cm3 and tensile strength over than 900 MPa. However, its application is limited because of a poor plastic formability and the expensive raw materials. In this study, Roll-Compaction (RCP) process was applied to fabricate high strength pure titanium composite reinforced with titanium oxides (TiO2) by using cheap sponge Ti powders as input materials. RCP was effective to improve the mechanical responses by the grain refinement and the in-situ formation of TiO2 dispersions of the matrix. RCPed powder was consolidated by using spark plasma sintering (SPS) process to serve a high density compact. Subsequently, hot extrusion process was applied to the sintered billet to prepare a full density rod specimen. The evaluation of their mechanical properties at room temperature showed high tensile strength of 640 MPa and good elongation of 17%.

S0401-1-1 酸化物分散および微細組織化によるチタン粉末固化材の強度特性(粉末成形とその評価(1))

Titanium (Ti) alloys are applied for various fields such as aircraft and automotive industries due to their high specific strength. Ti-6Al-4V (Ti64) is the most general Ti alloy, and shows superior mechanical properties i.e. 900MPa to 1200MPa of tensile strength. However, its application is limited because of a poor ductility and the expensive initial cost. In this study, Roll-Compaction (RCP) process is applied to pure Ti powder to solve the above problems. Pure sponge Ti powders were employed as input materials. RCP was effective for the grain refinement and the in-situ formation of titanium oxide (TiO_2) dispersions of the matrix to improve the mechanical response in using pure titanium. RCPed powder was consolidated by using spark plasma sintering (SPS) equipment to serve a high density billet. Subsequently, hot extrusion process was applied to the billet to prepare a full density rod specimen. The evaluation of mechanical properties at room temperature showed high tensile strength of 640MPa and good elongation of 17%. Moreover, the refining process and heat treatment of RCPed powders before SPS showed extremely high tensile strength of 935MPa.

Characterisation of density distributions in roller-compacted ribbons using micro-indentation and X-ray micro-computed tomography

Roller compaction is one stage in a dry granulation process to produce free flowing granules. Its proper understanding is essential in optimising manufacturing efficiency and product quality. Roller compaction produces a compacted strip or “ribbon”, which is then milled to produce granules. For a given milling condition, the density distribution in the ribbons determines the properties of the granules (particularly their size distribution and strength). Therefore, knowing the density distributions in the ribbons is very important in improving the effectiveness of the roller compaction process and the quality of the granules produced. In this paper, the density distribution in roller-compacted ribbons of microcrystalline cellulose (Avicel PH102) has been examined using three different techniques: (1) sectioning; (2) micro-indentation and (3) X-ray micro-computed tomography. It has been shown that with proper calibration all three techniques can essentially produce the same results, but with a different degree of resolution (scale of scrutiny). In addition, the influence of process conditions, such as roll gap, roll speed and the presence or absence of lubrication, on the ribbon density distributions has also been investigated. Flow into the press is often constrained by the presence of “cheek plates”, which prevent lateral powder movement. In this type of arrangement, it is found that non-uniform powder feeding occurs in the compaction region, induced by the friction between the powder and the cheek plates; as a result, the densities in the middle of the ribbon width are generally higher than those close to the edges. It has also been shown that higher average ribbon densities are obtained when the roll gap, roll speed, or the friction between the powder and the side cheek plates is reduced.

Investigation of the Variability of NIR In-line Monitoring of Roller Compaction Process by Using Fast Fourier Transform (FFT) Analysis

The purpose of this research was to investigate the variability of the roller compaction process while monitoring in-line with near-infrared (NIR) spectroscopy. In this paper, a pragmatic method in determining this variability of in-line NIR monitoring roller compaction process was developed and the variability limits were established. Fast Fourier Transform (FFT) analysis was used to study the source of the systematic fluctuations of the NIR spectra. An off-line variability analysis method was developed as well to simulate the in-line monitoring process in order to determine the variability limits of the roller compaction process. For this study, a binary formulation was prepared composed of acetaminophen and microcrystalline cellulose. Different roller compaction parameters such as roll speed and feeding rates were investigated to understand the variability of the process. The best-fit line slope of NIR spectra exhibited frequency dependence only on the roll speed regardless of the feeding rates. The eccentricity of the rolling motion of rollers was identified as the major source of variability and correlated with the fluctuations of the slopes of NIR spectra. The off-line static and dynamic analyses of the compacts defined two different variability of the roller compaction; the variability limits were established. These findings were proved critical in the optimization of the experimental setup of the roller compaction process by minimizing the variability of NIR in-line monitoring.

Simulation of Roller Compaction with Subsequent Tableting and Characterization of Lactose and Microcrystalline Cellulose

Tablets are by far the most common solid oral dosage forms, and many drugs need to be granulated before they can be tableted. Increasingly roller compaction is being used as a dry granulation technique; however it is a very time and material intensive method. Thus some mini roller compactors and simulations of the roller compaction process have been developed as a means of studying the technique at small scale. An important factor in the selection of materials for roller compaction is their ability to be recompressed into tablets after the initial roller compaction and milling steps. In this paper the roller compaction process was simulated on the basis of some models by Gereg and Cappola (2002) and Zinchuk et al. (2004). An eccentric tableting machine was used to make compacts from α–lactose monohydrate, anhydrous β-lactose, spray-dried lactose and microcrystalline cellulose at different maximum relative densities (ρrel,max 0.6–0.9). These compacts were milled immediately to granules with a rotary granulator. The properties of the granules were analyzed and compared to the properties of the original powders. These granules and powders were then tableted at different maximum relative densities (ρrel,max 0.75–0.95) and their properties including elastic recovery, crushing force and 3D-model were analyzed. The properties of the tablets made from the granules were compared to the properties of the tablets made from the powders to determine which excipients are most suitable for the roller compaction process. The study showed that anhydrous β-lactose is the preferred form of lactose for use in roller compaction since compaction did not affect tablet crushing force to a large extent. With the simulation of roller compaction process one is able to find qualified materials for use in roller compaction without the necessity of a great deal of material and time.

Electrochemical Dissolution Characteristics of Magnesium Alloy Produced by Roll Compaction Process

The extruded AZ31B Mg alloy specimens using powders fabricated by roll compaction processing (RCP) was prepared, and their corrosion behavior has been investigated through the polarization test, electrochemical impedance spectroscopy test, immersion test and SEM observation in comparison to that of the conventional AZ31B Mg alloy, hereafter shortened as I/M specimen. The extruded AZ31B Mg alloys using RCP powder showed little change in Ecorr irrespective of number of pass cycles. Both anodic and cathodic current density suppression of the RCP specimens became larger with an increase in number of pass cycles. It was also confirmed that the corrosion characteristics of the RCP specimens depended strongly on their structural morphology and that the corrosion resistance of the RCP specimens subjected to 50 pass cycles was nearly same as that of the I/M specimen.

Improving the compaction properties of roller compacted calcium carbonate

The effects of roller compaction process parameters, morphological forms of calcium carbonate and particle size of sorbitol on flow, compaction and compression properties were investigated. The morphology of the calcium carbonate and the sorbitol particle size were more influential on the compaction properties than the settings of the roller compactor. The roller compaction process was demonstrated to be robust and stable in regard to flowability and compactibility. The flowability of the granules was improved adequately to facilitate compression in a production scale rotary tablet press. By adding sorbitol to the calcium carbonate, the compressibility – characterized by the Walker coefficient W ID – and the compactibility C P were improved considerably. A correlation between the consolidation characteristics was demonstrated. Compactibility data from the compaction simulator correlated with the tablet press for two of the calcium carbonates, the cubic form and the ground quality.

Application of thermal effusivity as a process analytical technology tool for monitoring and control of the roller compaction process

The aim of this study was to examine the relationship between physical characteristics of compacted ribbons and their thermal effusivity in an attempt to evaluate the feasibility of using effusivity for in-process monitoring of roller compaction. In this study, thermal effusivity, solid fraction, tensile strength, and Young's modulus of ribbons of microcrystalline cellulose (MCC), anhydrous lactose, and placebo (PBO) formulations containing various ratios of MCC to anhydrous lactose (75:20, 55:40, 40:55, and 20:75) were determined at various compaction pressures (25-150 bars). The effusivity-square root of solid fraction relationship was linear for MCC and all the PBO formulations but was a second-order polynomial function for lactose. This could be due to the predominant deformation of lactose by brittle fracture, which might have significantly increased the number and size of contact points between particles, causing a change in thermal conductivity along with a density change. The effusivity-tensile strength and effusivity-Young's modulus relationships were best described by logarithmic functions for MCC but were linear for lactose up to a compaction pressure of 65 bars. There were similar relationships for effusivity with tensile strength and Young's modulus for all PBO formulations except PBO IV, which might have been due to the deformation of lactose, the largest component in this formulation. Strong correlations between effusivity and physical properties of ribbons were established. Although these correlations were formulation-dependent, they demonstrate the possibility of using effusivity as a tool in monitoring roller compaction.

Using intelligent software to predict the effects of formulation and processing parameters on roller compaction

Roll compaction is a dry, continuous granulation process, which is widely used in the pharmaceutical, chemical, metallurgical, mineral and agricultural industries to produce dust-free and free-flowing agglomerates. Intelligent software has been used to predict the relationships between tablet formulations, roll compaction process parameters and the roll compacted ribbon, from which granules for tablet manufacture can be produced. The software exploits the strengths of artificial neural networks, genetic algorithms and fuzzy logic to predict multivariate relationships from experimental data. Input data were generated from material characterisation studies and from investigations conducted on a 20 cm diameter laboratory-scale roll press with side plates, where process parameters such as roll speed (1–5 rpm), roll gap (0.5–1.4 mm) and compaction pressure (up to 230 MPa) could be manipulated. The relative significance of inputs on various outputs such as ribbon properties, nip angle and maximum roll compaction pressure was investigated using the commercially available artificial intelligence software FormRules (Intelligensys, Teeside, UK). The important inputs and required outputs were subsequently used in the model-development software INForm (Intelligensys, Teeside, UK) so that the conditions necessary to produce ribbons with specific desired properties could be predicted.

各種手法により作製されたＭｇ合金の腐食特性

The fundamental corrosion behavior of conventional AZ-series Mg alloys, i.e. AZ31, AZ61 and AZ91, has been conducted through the electrochemical test to investigate the corrosion behavior of extruded Mg alloys using powders fabricated by roll compaction process (RCP). The corrosion behavior of AZ-series Mg alloys depended on the standard electrode potential of Al content in Mg alloys. And the corrosion resistance has been improved most in AZ91 Mg alloy. The corrosion behavior of extruded AZ31B Mg alloys using powders fabricated by RCP has been also investigated through the polarization test, immersion test and SEM observation in comparison to that of the conventional AZ31W Mg alloy. The extruded AZ31B Mg alloys using RCP powder showed little change in Ecorr irrespective of number of pass cycles. Both anodic and cathodic current density suppression of the RCP specimens became larger with an increase in number of pass cycles. It was also confirmed that the corrosion characteristics of the RCP specimens depended strongly on their structural morphology and that the corrosion resistance of the RCP specimens subjected to 50 pass cycles was nearly same as that of the I/M specimen.

434 RCP処理を施したマグネシウム合金押出材の組織と集合組織(アルミニウム合金およびマグネシウム合金の創製と加工技術2)

Magnesium alloy is the lightest in a practical metal and that expected to be used various industries. However, the magnesium alloys has the property that with the plastic forming at ordinary temperature range is difficult since film aggregate texture is formed. It is understood that RCP refine grains and reduce crystalline orientation. The extruded magnesium alloy via casting has anisotropy; the mechanical property is different according to extruding direction. It is suitable that the anisotropy is smaller when magnesium alloys are used at various industrially. In this study, the anisotropy for extrusion direction of the extruded AZ31 magnesium alloy via rollcompaction process is investigated, and influence of microstructure and texture on anisotropy is cleared.

Investigation of Serrated Roll Surface Differences on Ribbon Thickness During Roller Compaction

Many parameters are considered when developing a roller compaction process. However, roll serration volume is generally not considered when using serrated rolls. It was hypothesized that serration volume of concavo-convex rolls can have a significant effect on ribbon thickness due to differences in nip angle. Experiments were conducted to investigate ribbon thickness using different roll sets having a range of serration volumes. Roll sets with approximately twice the serration volume produce ribbons 20–25% greater in thickness. These results correlated with physical measurements taken of the serrations from each set. Thus, differences in roll serration volume can significantly affect ribbon thickness.

粉体プロセスによるマグネシウム合金の微細組織制御と高強靭性化

Roll compaction (RCP) process has been developed in order to produce wrought magnesium alloys with a good balance of strength and ductility via powder metallurgy. Extruded Mg alloys showed fine microstructures; a mean grain size with 1-2μm by dynamic recrystallization during RCP and hot extrusion. In applying RCP to the conventional AZ31 alloy powder, their wrought materials had superior mechanical properties of 390MPa tensile strength, 360MPa yield strength and 16% elongation at room temperature compared to the conventional ones. Its low temperature formability was also completely improved due to both refined grains and texture control by RCP process.

Roll compaction of maize powder

This paper presents a study of a roll compaction process as a dry granulation method for typical food materials such as maize powder. This process is widely applied in industry as it can continuously produce large quantities of granular product at comparatively low cost. The objectives of this work were to predict the roll compaction performance from a simple measurement involving uniaxial die compaction using the classical Johanson model. This involved determination of the optimum operating conditions for the production of granules as evaluated by apparent density. In the current work, a smooth counter-rotating rolling mill with a roller diameter of 0.08 m and a roller width of 0.20 m was used. The operating conditions for the rolling mill are shown to be influenced by parameters such as the roll gap, the roll speed, the feed powder amount, and the friction ratio. Material properties such as the compressibility factor and the angle of wall friction were investigated using uniaxial die compaction. The angle of wall friction was analysed using both contact mechanical and continuum mechanical approaches. The results indicated that this simplified approach can be used to provide a quantitative prediction of the extent of the roll compaction performance, and can be used to design optimal roller geometries and operating conditions.

2244 結晶粒微細化処理マグネシウム合金の機械的特性(S25 軽量化・高強度化材料とその加工)

High strengthened magnesium alloys were developed by employing grain-refined coarse powder via roll compaction (RCP) process. The conventional powder metallurgy (P/M) process, consisting of cold compaction and hot extrusion with an extruding ratio of 37, was applied to fabricate the grain-refined powder into full dense. The grain size strongly depends on the number of cycles in RCP process, for example the mean grain size of 4μm and 1.1μm in 30 and 50 cycles, respectively were observed in optical microstructures. The micro-hardness and tensile strength increase with increase in the number of cycles in RCP. The hot extruded AM60 alloy in using the powder after 50 cycles indicates 370MPa UTS and elongation of 20%. The mechanical properties are extremely superior, compared to the conventional P/M magnesium alloys. Newly developed magnesium alloys, ZAXE1713 (Mg-1Zn-7Al-1Ca-3La/mass%), via RCP and hot extrusion process, show a good balance of high strength and ductility, such as 410MPa UTS and elongation of 17% at room temperature.

Simulation of roller compaction using a laboratory scale compaction simulator

A method for simulation of the roller compaction process using a laboratory scale compaction simulator was developed. The simulation was evaluated using microcrystalline cellulose as model material and ribbon solid fraction and tensile strength as key ribbon properties. When compacted to the same solid fractions, real and simulated ribbons exhibited similar compression behavior and equivalent mechanical properties (tensile strengths). Thus, simulated and real ribbons are expected to result in equivalent granulations. Although the simulation cannot account for some roller compaction aspects (non-homogeneous ribbon density and material bypass) it enables prediction of the effects that critical parameters such as roll speed, pressure and radius have on the properties of ribbons using a fraction of material required by conventional roller compaction equipment. Furthermore, constant ribbon solid fraction and/or tensile strength may be utilized as scale up and transfer factors for the roller compaction process. The improved material efficiency and product transfer methods could enable formulation of tablet dosage forms earlier in drug product development.