Process design blending

For any given process, one takes a qualitative look at the possible role of fluid shear stresses. Then one tries to consider pathways related to fluid shear stress that may affect the process. If there are none, then this extremely complex phenomenon can be dismissed and the process design can be based on such things as uniformity, circulation time, blend time, or velocity specifications. This is often the case in the blending of miscible fluids and the suspension of sohds. 

This chapter discusses key considerations in excipient selection formulation and process design and control and blending and content uniformity during development of a low-dose direct compression formulation. 

Chemical engineers have worked with polymers since the first Bakelite articles were produced early in this century. Since then, the class of polymeric materials has grown to encompass a whole range of thermoset and thermoplastic resins, as well as copolymers and polymer blends, and chemical engineers have played major roles in the rise of these materials to commercial success. From production of the resins (which involves heat and mass transfer, kinetics, fluid dynamics, process design, and control) to the fabrication of final articles (involving many of the same processes, as well as some unit operations not part of traditional chemical engineering, such as extrusion... 

Scheme 1 shows that it is possible to distinguish among different kinds of processes leading to chirality transfer. This distinction is mainly based on the possibility of choosing the type of control that self-organization processes have to obey thermodynamic, kinetic or a designed blend of both. 

Therefore, it is not surprising that this cascaded process opens the door to products with combinations of properties so far not known [48-50]. It is important to underline that with this process design the polymer generated in all three polymerization reactors is finely divided in the final polymer particle. Each catalyst primary particle is enveloped with the polymer from reactors 1, 2, and 3. With this in-situ blend it is possible to obtain a homogeneous melt in the granulation facility this is necessary to exploit the full potential of the product in the solid state. Mechanical blending of such three types of polyethylenes would never lead to a homogeneous melt. 

In 1979, the UNIPOL process for gas-phase production of LLDPE was introduced by the Union Carbide Corp. Since the new resins were difficult to process on the lines designed for LDPE, by 1982 several patents were issued for improvement of LLDPE processability by blending it with other polyolefins, viz., LDPE, PP, and olefinic rubbers. Ethylene copolymers, rubbers, EPDM, EVAc, maleated polypropylene, EPR, etc., have also been used (Cowan 1983 Turtle 1983 Fukui et al. 1983 Haas 1983 Hert 1983). Thus, blends LLDPE/LDPE were found miscible at low LDPE contents, then immiscible at high LDPE. Addition of HDPE as cosolvent resulted in miscible tertiary blends (Lee and Denn 2000). 

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