Pelletization processes process

Sorted plastic packaging materials are shipped, usually in bales, to processing plants to be converted to polymer resins. The bales are broken and the bottles sorted to ensure that only one type of polymer is further processed. Processing consists of chopping and grinding the bottles into flakes. These flakes are washed. Processing steps such as flotation are used to remove polymeric contaminants from the flakes (15,16). The flakes are melted and converted into pellets. 

Oxidation of LLDPE starts at temperatures above 150°C. This reaction produces hydroxyl and carboxyl groups in polymer molecules as well as low molecular weight compounds such as water, aldehydes, ketones, and alcohols. Oxidation reactions can occur during LLDPE pelletization and processing to protect molten resins from oxygen attack during these operations, antioxidants (radical inhibitors) must be used. These antioxidants (qv) are added to LLDPE resins in concentrations of 0.1—0.5 wt %, and maybe naphthyl amines or phenylenediamines, substituted phenols, quinones, and alkyl phosphites (4), although inhibitors based on hindered phenols are preferred. 

Other apphcations include dewatering extremely fine (0.1 llm) laterite leach tailings (91). These pelletizing processes should be compared in flocculant consumption and operating and capital costs with belt-filter presses. 

Typical results of the dry pelletizing process when a charge of carbon black and its plus 52-mesh seeds is tumbled in a drum (12) are shown in Figs. 31 and 32. Initially, the seeds grow in size rapidly by snowballing. The dip in the bulk density of the seeds (Fig. 32) suggests that the deposited layers are quite porous in the beginning but get compacted in due course to... 

The task of developing a suitable catalyst for commercial applications involves many considerations, ranging from obvious factors like catalyst activity and selectivity to variables like the catalyst shape and the composition of the binder used in a pelletizing process. This section is devoted to a discussion of these considerations and of the techniques involved in manufacturing industrial catalysts. 

Since fine catalyst particles are desired, the costs associated with the pelleting process are avoided, and it becomes possible to use catalysts that are difficult or impossible to pelletize. 

Yesilada O, Asma D, Cing S (2003) Decolourization of textile dyes by fungal pellets. Process Biochem 38 933-938... 

A commercial pelleting process, used for powdery, lumpy and pasty products, is illustrated in Figure 2.35. 

At the start of the melting process, the pressure in the channel is relatively low and the solid bed may not be fully compacted. In this case, molten resin from all films has the ability to flow into the voids between the individual pellets. This process is often referred to as melt infiltration. A photograph of a cross section of a Maddock solidification experiment at the start of the melting process is shown by Fig. 6.21. For this figure, the molten material prior to the solidification was black. Melt infiltration is shown by the black resin that has flowed from the films and in between the pellets. The flow of resin into the solid bed will likely cause the pressure in the films to decrease. 

Table 13.3 Screw Channel Dimensions for the 381 mm Diameter Screw for the PE Flame Retardant Pelletization Process...

Urethanes are processed as rubber-like elastomers, cast systems, or thermoplastic elastomers. The elastomer form is mixed and processed on conventional mbber mills and internal mixers, and can be compression, transfer, or injection molded. The liquid prepolymers are cast using automatic metered casting machines, and the thermoplastic pellets are processed like all thermoplastic materials on traditional plastic equipment. The unique property of the urethanes is ultrahigh abrasion resistance in moderately high Shore A (75—95) durometers. In addition, tear, tensile, and resistance to many oils is very high. The main deficiencies of the urethanes are their resistance to heat over 100°C and that shear and sliding abrasion tend to make the polymers soft and gummy. 

Leuenberger H, Luy B, Studer J. New development in the control of a moist agglomeration and pelletization process. STP Pharma 1990 6 303-309. 

Although many types of pellet dosage forms have been introduced in the marketplace, a greater understanding is needed of the role of excipients, equipment, process variables, and controls involved in the pelletization process and those that govern successful scale-up from laboratory to... 

Table II. Effects of Method of Moist Pellet Processing on the Isolation of Mutagenic Residue Organics from Secondary Sludge...

Figure 2.7.3 shows a schematic drawing of a Cryogen Rapid Pelletizer. This process is of special interest if a product has to be frozen more quickly than is possi-... 

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