Fig. 4 Principle of operation of rotor/stator homogenizer. late matter and can have compatibility problems with the product. [These sealing aids are now being made of polytetrafluoroethylene (PTFE), which improves the situation in most cases.] For manufacture of sterile products, the dispersing elements need to be sterilized, preferably by using steam. Experiments have shown that these elements are steam sterilizable in 15-30 min at 121 °C. These dispersers are available as in-line models or vertically mounted "probe"-style units (see Fig. 5). A colloid mill has several similarities with the rotor-stator type mixer. It has a stationary "stator" through the center of which the product is pumped at high pressure. The rotor moves close to the stator. The gap is often adjustable and is of the order of 0.1 mm. The adjustable feature of the gap often makes reproducibility of batches a challenge, as the screw type of adjusting mechanism for the rotor often is not repro-ducible to a high degree of accuracy. In a reciprocating design homogenizer, a piston moves in a cylinder and pushes the product through a nozzle whose opening is adjustable by means of a spring loaded Fig. 5 Dispersing element of an in-line unit. (Photo courtesy of Ika-Werke, Germany.)

doi:10.1201/9781420000955-66

Chapter

Fig. 4 Principle of operation of rotor/stator homogenizer. late matter and can have compatibility problems with the product. [These sealing aids are now being made of polytetrafluoroethylene (PTFE), which improves the situation in most cases.] For manufacture of sterile products, the dispersing elements need to be sterilized, preferably by using steam. Experiments have shown that these elements are steam sterilizable in 15-30 min at 121 °C. These dispersers are available as in-line models or vertically mounted "probe"-style units (see Fig. 5). A colloid mill has several similarities with the rotor-stator type mixer. It has a stationary "stator" through the center of which the product is pumped at high pressure. The rotor moves close to the stator. The gap is often adjustable and is of the order of 0.1 mm. The adjustable feature of the gap often makes reproducibility of batches a challenge, as the screw type of adjusting mechanism for the rotor often is not repro-ducible to a high degree of accuracy. In a reciprocating design homogenizer, a piston moves in a cylinder and pushes the product through a nozzle whose opening is adjustable by means of a spring loaded Fig. 5 Dispersing element of an in-line unit. (Photo courtesy of Ika-Werke, Germany.)

Chapter

Fig. 4 Principle of operation of rotor/stator homogenizer. late matter and can have compatibility problems with the product. [These sealing aids are now being made of polytetrafluoroethylene (PTFE), which improves the situation in most cases.] For manufacture of sterile products, the dispersing elements need to be sterilized, preferably by using steam. Experiments have shown that these elements are steam sterilizable in 15-30 min at 121 °C. These dispersers are available as in-line models or vertically mounted "probe"-style units (see Fig. 5). A colloid mill has several similarities with the rotor-stator type mixer. It has a stationary "stator" through the center of which the product is pumped at high pressure. The rotor moves close to the stator. The gap is often adjustable and is of the order of 0.1 mm. The adjustable feature of the gap often makes reproducibility of batches a challenge, as the screw type of adjusting mechanism for the rotor often is not repro-ducible to a high degree of accuracy. In a reciprocating design homogenizer, a piston moves in a cylinder and pushes the product through a nozzle whose opening is adjustable by means of a spring loaded Fig. 5 Dispersing element of an in-line unit. (Photo courtesy of Ika-Werke, Germany.)

ABSTRACT

The submerged-jet-type disperser is a new design that has recently been introduced. This type of equipment makes use of "free turbulence," created when two jets of fluid impinge on each other. The product is pumped at pressures ranging from 3000 to 25,000 psi through a narrow channel, which is then bifurcated into two channels of smaller size. The product streams passing through these channels are then directed at each other in an interaction chamber, where they impinge upon each other (see Fig. 6). The resulting free turbulence (as opposed to the wall turbulence created when moving parts create turbulence) results in size reduction. Considerable heat is generated and in general this calls for intercooling between passes. While these types of dispersers can be steam-sterilized, the extremely small size of their channels can provide a challenge when trying to validate the sterility by seeding with spores. Sterilization using hydrogen peroxide may be a highly efficient and pharmaceutically acceptable method for this type of equipment. This type of equipment is available from lab-scale to fullscale size (see Fig. 7).