Rotary die process

Fig. 2. Rotary die process of soft gelatin capsules where A represents the drug mix B, the mold wedge C, gelatin ribbons D, die roUs E, capsules and F,...

Following the success of rotary die process, the Norton Company in 1949 has announced the development of another continuous soft gelatin capsule processing technology known as reciprocating die process. 

Soft elastic gelatin capsules arc prepared in a rotary die process from two continuous gelatin ribbons. The capsules are formed, filled, and sealed in accurately timed opera tions, and can be filled with any liquid, semiliquid, paste, or even powder that will not dissolve or interact with the gelatin. 

Rotary compression machines convert powders and granules into hard tablets of quite uniform weight, notably of pharmaceuticals, but also of some solid catalyst formulations. The process is illustrated in Figure 12.8(a). A powder is loaded into a die where it is retained by a lower punch then it is compressed with an upper punch, and the tablet is ejected by raising both punches. 

SL/RN Process. In the SL/RN process (Fig. 4), sized iron ore, coal, and dolomite are fed to the rotary kiln wherein the coal is gasified and die iron ore is reduced. The endothermic heat of reduction and the sensible eneigy that is required to heat the reactants is provided by combustion of volatiles and carbon monoxide leaving the bed with air introduced into the free space above the bed. The temperature profile in the kiln is controlled by radial air ports in the preheat zone and axial air ports in the reduction zone. Part of the coal is injected through the centerline of the kiln at the discharge end. The hot reduced iron and char is discharged into an indirect rotary drum cooler. The cooled product is screened and magnetically separated to remove char and ash. 

The pharmaceutical industry produces tablets almost exclusively on rotary tablet presses from pilot plant to commercial manufacture. The output from different tablet presses may range from a few thousand tablets per hour to more than 1 million tablets per hour. By design, the compression event occurs using three parts a die, lower punch, and upper punch. The dies and punches are mounted on a rotating turret. The shape of the die controls the shape of the tablets, while the distance between the lower and upper punch tips at the maximum compression force determines the thickness of the tablets. The tablet compression process is divided into three steps powder filling into the die, compression, and tablet ejection from the die.85... 

Screw extruders are also used, however, to produce pelleted materials, either as a final product or for further processing, in the food, ceramics, chemical and other industries. Many orifices in a die plate form a multiplicity of extruded rods which are cut into pellets by rotary cutter blades. The extrusion operation is frequently the final step in a sequence of processes which may include binder/lubricant addition, mixing, heating, cooling or vacuum degassing. 

On a rotary press the filling of the die and the following compression process is done at the same time at different stations. The compression is carried out in the simplest case with two rolls touching the upper and lower punches and compressing the powder mixture. In contrast to the eccentric press, the upper and lower punches exert pressure on the tablet mixture from both sides at the same time. 

Rotary tableting machines work with a number of punch and die sets which move in a circle. The dies are fixed in a round die table and the die table circulates. Together with the dies the lower and upper punches circulate on tracks. The lower punches close the dies. The densification process is bilateral since both punches pass the compression wheels and the force is evolving on the upper as well as on the lower side of the powder bed. The produced tablets show the same hardness on the upper and lower surfaces. 

Special Rotary Machines As already mentioned one special rotary machine works slightly different—called IMA Comprima (Figure 6) [34], In this machine the material is filled by centrifugal force from the side directly into the die. The upper punch closes the die at the top and the lower punch closes the die at the bottom. However, when the given volume in the die is filled by the powder, both punches move downward until the die is completely closed. Then the compression process starts and the dies pass the compression wheels. After compression the tablet is ejected by the upper punch at the bottom of the die, contrary to all other rotary tableting machines which eject the tablet at the top of the die. 

Thus the simulation of tableting machines needs much effort and a real simulation is almost impossible because of the hydraulic control. Further the filling process of rotary tableting machines cannot be simulated since die filling is usually processed by a filling shoe moving forth and back. 

It is suggested that four mechanisms are basically involved in the process of compression of particles deformation, densification, fragmentation, and attrition. The process of compression is briefly described as follows small solid particles are filled in a die cavity and a compression force is applied to it by means of punches and then the formed monolithic dosage form is ejected. The shape of the tablet is dictated by the shape of the die while the distance between the punch tips at the point of maximum compression governs the tablet thickness, and the punch tip configuration determines the profile of the tablet. The compression cycle in a conventional rotary tablet press will be described in detail in this chapter and is illustrated in Figure 1. 

The key requirements for an acceptable STI slurry include adequate removal rate (> 3000 A/min) on oxide, desirable selectivity of oxide over nitride (between 200 1 and 400 1), high planarization efficiency across the die regardless of the patterned density, low scratch count, and low particle residue. The typical operating downpressure for an STI process is 3-5 psi. The typical platen and carrier speeds of a rotary tool are 100 and 60 rpm, respectively. The... 

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