Roller compactor

The spray-dried flavours or powder blends are processed by a roller compactor into lumps (Fig. 21.12). These lumps are crushed into granules. This process cannot be categorised as a direct encapsulating technique, since the flavour-encapsulating effect of compacted flavours is based on the use of spray-dried raw material. 

Gereg and Capolla developed process parameters determined by a model laboratory bench scale Carver press, model C (Carver Inc. Savannah, Georgia, U.S.A.), which were translated to production scale compactor parameters (6). Their study provided a method to predict whether a material is suitable for roller compaction. Their study objectives were to characterize properties of the material to identify process parameters suitable to achieve the necessary particle size and density using the dry granulation process and then translate laboratory information to a production scale roller compactor. Actually, information developed from a Carver press was correlated and scaled-up to a production scale Fitzpatrick roller compactor. Model IR 520 (Fitzpatrick Co., Elmhurst, Illinois, U.S.A.) The compactor produced very similar powder granule characteristics as the Carver press. Various lactose materials, available as lactose monohydrate or spray dried lactose monohydrate, were used as the model compounds. Results indicated that a parametric correlation could be made between the laboratory bench Carver press and the production scale compactor, and that many process parameters can be transferred directly. 

The roller compactor s full axial rolls produced compacts in the form of sticks. The unmilled compacts from both machines had the same density, 1.3g/cm. The milled roller compacts produced comparative granules except for bulk density and correspondingly the Carr index values ... 

Table 6 Physical Properties of Blends Manufactured Using Alexanderwerk AW-120 Roller Compactor... 

Roll speed and vacuum deaeration were kept constant at 8 rpm and 0.2 atmospheres, respectively. Roller compactor was equipped with 5 mm primary screen. Final sizing was conducted using an oscillator equipped with 20 mesh screen. 

Table 7 Vector Freund Roller Compactor Equipment Settings...

Table 9 Vector Freund Roller Compactor Parameters from Continued Trials...

Roller Compactor Development to Manufacturing Scale-Up Using Active and Placebo Blends... 

The corresponding AW 200 force/cm roll length of 4.10-7.40 kN translated to 50-85 bar. Therefore, the optimized roller compactor... 

Table 10 Roller Compactor Operating Conditions and Particle Size Distributions for 5% Active Granulation Trials...

Figure 3 Plot of d90 and d50 values for the 10% tolmetin granules versus the slope of best-fit line showing good agreement between the values from the compacts prepared under two different sets of roller compactor roll/HFS/VFS speed settings.

Figure 4 Comparison of the offline slope values (filled circles) with the real-time slope values (open triangles) for the 10% tolmetin compacts prepared at different roller compactor settings. Values on top are the roll, HFS, and VFS speeds, respectively.

Figure 5 shows the results of the authors study on the ability of NIR to monitor the scale-up from the laboratory Carver Press to the Fitzpatrick roller compactor. Because the NIR signal is influenced by changes in the physical and mechanical properties, multivariate data analysis techniques were used to identify and separate these contributions in the overall NIR signal. A flat-faced rectangular die and punch set, 40 x 15 mm in size, was fitted on the laboratory Carver Press to prepare tablets similar in shape and size to the roller compacted samples. 

Different spectral preprocessing and transformations available in SIMCA P-p (version 10.0, Umetrics, Sweden) were evaluated and the best approach for data handling and manipulation was determined. Data collected on the surrogate tablets were divided into a training set to generate the PLS models, and prediction set to test the PLS models. MCC powder, equilibrated at different RH, was also roller compacted at different roll speeds on a Fitzpatrick IR220 roller compactor fitted with smooth rolls. Powder feed rate and roll pressure were kept constant for all experiments. The key sample attributes measured on the surrogate tablets were also measured for the samples prepared by roller compaction. 

The authors thank Alexanderwerk Inc., Horsham, Pennsylvania, U.S.A. for information provided the Consortium for the Advancement of Manufacturing of Pharmaceuticals (CAMP), Narberth, Pennsylvania, U.S.A. for funding this work and the Fitzpatrick Company, Elmhurst, Illinois, U.S.A. for providing the roller compactor for the NIR study. The authors acknowledge the careful editing of the manuscript by Carol G. Miller. 

MICHAEL LEVIN is President and CEO, Metropolitan Computing Corporation (MCC), East Hanover, New Jersey, specializing in process analytical instrumentation as well as data acquisition and control systems for tablet presses, mixers, roller compactors, and other equipment. Prior to forming MCC in 1985, he was a consultant to pharmaceutical companies such as Merck, Sandoz, and Warner-Lambert. A member of the American Association of Pharmaceutical Scientists, the International Society for Pharmaceutical Engineering, and the Biomedical Engineering Society, Dr. Levin received the Ph.D. degree (1985) in biomathematics from the University of Washington, Seattle. 

Miller RW. 1994. Advances in pharmaceutical roller compactor feed system designs. Pharm. Technol. 18(3) 154-162. 

Manufacture by Roller Compaction The active ingredients and Kollidon VA 64 were granulated in a Gerteis Roller compactor. 

Conventional processing equipment (mixers, granulators, roller compactors, drying equipment, and mills) can be used to produce effervescent preparations if the influence of atmospheric moisture is considered. As a rule, tablet presses have to be adapted to handle effervescent products, except for tablets with a sufficient proportion of a self-lubricating substance, such as acetylsalicylic acid. 

Johanson pointed out that no roller compactor theories at that time determined the angle of the nip and the bulk density at 0 = a, except by actually rolling the granular solid in a roll press. He also provided a method to calculate the nip angle and the pressure distribution between the rolls. His calculations... 

Pietsch described a compaction capacity throughput equation for a roller compactor using flat rolls. The equipment capacity equation is theoretical in nature it assumes that all compacts are 100% useable for downstream processing needs. Compact capacity throughput, Cc, for a roller compactor can be determined by Eq. (4). ... 

Certainly, a key enhancement that highlights today s pharmaceutical industry s state-of-the-art roller compactors, is programmable logic controllers (PLCs). They are used to control and monitor mechanical parts that regulate screw feed rate, roll speed, roll pressure, roll gap, vacuum deaeration, and mill speed. This section will not discuss PLC designs as it relates to compactor design features and advancements. 

Irmovatively designed feed screw systems are used commercially in roller compactors worldwide. An example is shown in Fig.6. 

Sizing devices are now trimly fitted to the compactor body and controlled by variable speed drives. Most compactors no longer require a second machine (mill) in tandem to size compacts as required by slugging technology. Roller compactors have clean-in-place (CIP) systems that offer environmental and safety features. These systems minimize human exposure to chemicals and improve cleaning efficiencies. Fig. 7. 

Currently, one manufacturer of roller compactor equipment for the pharmaceutical industry has a fixed roll-pair system. This type of roll design system relies on powder gravity feed and a specially designed compression feed screw to continuously deliver powder feed stock to the fixed roll pair. Fig. 10. 

Fig. 12 Roller compaction compacts. Roller compactor feed screw designs twin feed screw and single feed screw. (Courtesy of R. W. Miller, personal files.)...

Fig. 18 Computer controlled roller compactor with horizontal feed screws, vacuum deaeration, and cantilevered rolls. (Courtesy of Alexanderwerk Inc.)...

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