Small-scale batch compounding

Small-scale batch compounders are particularly suitable for fundamental research as good mixing results can be obtained with small material amounts. Furthermore, the simple systems are easy to clean. Altogether, a broad screening of mixtures and processing 

In a first example, a masterhatch with 15 wt% MWCNTs (Hyperion Catalysis, Inc., Cambridge, USA) has been diluted to obtain composites with 0.875 wt% filler content. For this purpose, a DACA microcompounder (DACA Instruments, USA) has been employed. Two samples have been prepared at 250 and 300 °C mixing temperature, whereby the mixing time and speed were 15 min and 50 rpm, respectively. LM indicated almost complete nanotube dispersion at both mixing temperatures 1) Significant differences in the 

In the following, the influence of mixing conditions on the nanotube dispersion and distribution by direct incorporation will be discussed exemplarily by means of composites containing 1 wt% MWCNTs (Nanocyl NC 7000, Nanocyl S.A., Sambreville, Belgium) in polycarbonate. The samples have been also prepared using a DACA microcompounder. 

Appendix). However, this effect is probably only relevant for raw nanotube material with very low packing densities. The material used for this example exhibits a packing density of around 0.07 and can be compressed to values up to 0.25 [30]. 

Next to the mixing temperature, the fragmentation number depends on the screw speed. The variation of screw speed at 240 °C with 5 min mixing time leads to the results shown 

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Reduction of nitro compounds is accomplished by (1) catalytic hydrogenation, (2) iron reduction (Bechamp), (3) sulfide reduction, or (4) zinc reduction in an alkaline medium. Generally, when the reaction is carried out on a large scale, the catalytic procedure is best. For small-scale batch operations, chemical reduction is preferred. 

Commercial-scale batch reactors are generally used for small-lot or specialty items. This includes chemicals such as paints, dyes, and pharmaceuticals. Batch reactors are very simple and flexible. Vessels used to make one compound can be washed and reused to make other products. The ease of cleaning and maintaining batch reactors along with low capital investment and low instrumental costs... 

The vessel used for the compounding may be different during development simply because of batch size. Compatibility with these different materials is important to consider in preparation for scale-up. Bench-scale studies and small clinical batches may be compounded in glass Erlenmeyer flasks or glass carboys. Commercial-scale manufacturing would typically use larger stainless steel tanks. Compatibility with the different materials that the product comes into contact... 

Continuous processing is useful for reactions that need rapid heat transfer [4], for preparing unstable compounds, and for reactions in which physical effects are localized. When safety or stability is a major concern, continuous processing has advantages over batch processing in that only a small portion of the batch is subjected to reaction conditions at any moment. Following is a discussion of some large-scale and small-scale applications. 

Enantiomerically pure compounds will be used above all as pharmaceuticals and vitamins [4], as agrochemicals [5], and as flavors and fragrances [6]. Pharmaceuticals and agrochemicals usually are multifunctional molecules that are produced via multistep syntheses. Compared to basic chemicals, they are relatively small scale products with short product lives, produced in multipurpose batch equipment. The time for development of the production process is often very short since time to market affects the profitability of the product. 

Oxidation and reduction are fundamental processes in the synthesis of organic and inorganic compounds. Some oxidation and reduction reactions are difficult to control in macro-scale batch reactors and in such cases microflow reactors serve as powerful tools for accomplishing the reactions in a highly controlled manner. This is especially true for many oxidation reactions because of their exothermic nature. It should also be noted that the danger of unexpected explosions can be avoided by the use of microflow reactors because of the small volume and highly efficient heat transfer ability of microflow systems. This chapter provides an overview of oxidation and reduction reactions using chemical, electrochemical and biochemical methods in microflow reactors. 

Based on an evaluation of the physicochemical properties of the active compound, several initial formulations (generally, four to six) are selected and screened in this step (Dobry et al. 2009). A small-scale spray dryer designed for maximizing yields from SDD batches of less than 100 mg is used. This dryer is not designed to replicate optimized bulk powder properties (e.g., particle size, density) of larger scale spray dryers, but rather is used to guide formulation decisions based on physicochemical properties and fast, efficient formulation-screening studies. 

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