Batch extrusion

FIGURE 13.13 Early batch extrusion processing of flavorings. (From Beck, E.E., Essential oil composition, U.S. Patent 3704137, 1972. With permission.)... 

The batch extrusion process, which produces POFs in a completely closed system from the distillation of a monomer by fiber drawing, was developed by Kaino et al. [1]. Figure 5.2 shows a schematic diagram of the apparatus. A purified monomer is placed in a monomer flask, and an initiator and a chain-transfer agent are placed in another flask. Both flasks are sealed and evacuated. After freeze-pump-thaw cycles, the monomer and the mixture of the initiator and chain-transfer agent are distilled into the polymerization reactor. The reactor is heated at a certain temperature for a period adequate to fully polymerize the... 

Continuous Solvent—Extrusion Process. A schematic for a typical continuous process, widely used for making solvent propellant for cannons, is shown in Figure 7. This continuous process produces ca 1100 metric tons of single-base propellant per month at the U.S. Army Ammunition Plant (Radford, Virginia). Continuous processes have also been developed for double- and triple-base propellants and for stick as well as granular geometries. A principal aspect of these processes has been the extensive use of single- and double-screw extmders instead of the presses used in the batch process. 

Screw-Discharge Batch Mixers A variant of the sigma-blade mixer is now available with an extrusion-discharge screw located in the saddle section. During the mixing cycle the screw moves the material within the reach of the mixing olades, thereby accelerating the... 

Following research by Tossavainen et al. (1986), extrusion is often used to produce insoluble acid casein from skim milk powder and to convert acid casein into sodium caseinate. The procedure is faster than batch mixing (Akdogan, 1999). 

Drying and milling the resulting wet pigment presscakes, possibly preceded by extrusion or granulation, finally affords the desired pigment powder. Drying may be carried out either by a continuous process on a conveyor belt or as a batch operation in a convection oven. 

Fig. 2.15. Reactors for producing these materials include batch, continuously vented, tray reactors, twin-screw extruders, and vented single-screw extruders. These production devices will not be covered in this text because they are of more interest to the manufacturing engineer than the extrusion process engineer.

Example 1 Film extrusion on blown film line. Antiblock agents like masterbatches of talc, chalk or silica (e.g., Ecoflex Batch AB 1) can be used for Ecoflex and Ecovio . The recommended level is higher than for polyolefins, e.g., 1 % of antiblock agent. If Ecovio compounds are processed, an antiblock agent in most cases is not needed for Ecovio F Film and Ecovio E Blend, because PLA acts as antiblock agent in higher quantities. 

Example 2 Film extrusion on a chill roll line. In order to avoid sticking to the chill roll of Ecoflex or Ecovio we have to use an appropriate amount of antiblock, e.g., at least 1% of Ecoflex Batch AB 1. Slip agent, e.g., 500-1,000 ppm of erucamide should be used if the final Aim properties require a low coefficient of friction. 

Viscoelastic Measurement. A number of methods measure the various quantities that describe viscoelastic behavior. Some require expensive commercial rheometers, others depend on custom-made research instruments, and a few require only simple devices. Even qualitative observations can be useful in the case of polymer melts, paints, and resins, where elasticity may indicate an inferior batch or unusable formulation. For example, the extrusion swell of a material from a syringe can be observed with a microscope. The Weissenberg effect is seen in the separation of a cone and plate during viscosity measurements or the climbing of a resin up the stirrer shaft during polymerization or mixing. 

Melt filtration systems are commonly employed in pigment master-batch production and in situations where the presence of defects in the compound may have a critical effect on its subsequent processing or properties. This is vitally important, for example, in fibre-spinning operations involving extrusion of polyester or polyamide through fine spinneret plates [162], and in minimizing breakdown of polymer cable insulation subjected to electrical stress [163]. 

Extrusion-spheronization can provide highly dense, spherical pellets with a smooth surface and a narrow particle size distribution and with drug loading as high as 90%. It is also amenable to batch or continuous processing (9-11). A schematic of extrusion-spheronization and associated unit operations (12,13) are shown in Figure 1. 

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