Extrusion monitoring

Key words extrusion monitoring NIR polymer quantitative analysis... 

Treatment of ethyl 2,7-di-/ert-butylthiepin-4-carboxylate (24) with 3-chloroperoxybenzoic acid at — 78 °C results in the benzene derivative 25 only, and no sulfur-oxidized products 80 however, the stable 2,7-di-ter/-butylthiepin (26) can be oxidized with 0-benzyl 00-hydrogen monoper-oxycarbonate at — 78 °C to give the corresponding S-oxide 27, which was monitored by HNMR spectroscopy at — 40°C. At —15 C, sulfoxide 27 was converted, via extrusion of sulfur monoxide, with a half-life of 5.5 hours to the benzene derivative 28.87 The oxidation reaction of 26 with excess of the monoperoxycarbonate did not proceed to the S,S-dioxide, even though the parent thiepin 1,1-dioxide is known to be stable at room temperature.15... 

The synthesis of monocyclic thiepins from thiophene and dimethyl acetylenedicarboxylate is often accompanied by the loss of sulfur. In particular, in cases where room temperature is required for efficient rates of cycloaddition and rearrangement76 (see Section 2.1.3.3.), the desulfurization reaction proceeds rather quickly with the consequence that thiepin formation can be monitored by low temperature HNMR spectroscopy, but the products cannot be isolated.76 - 78 However, in the case of thiepin 1 where R1 = R2 = C02Me and R3 = H, refluxing toluene is necessary for the extrusion of sulfur.78... 

S.E. Barnes, E.C. Brown, M.G. Sibley, H.G.M. Edwards and P.D. Coates, Vibrational spectroscopic and ultrasound analysis for the in-process monitoring of poly(ethylene vinyl acetate) copolymer composition during melt extrusion, Analyst, 130, 286-292 (2005). 

I. Alig, D. Fischer, D. Lellinger and B. Steinhoff, Combination of NIR, Raman, ultrasonic and dielectric spectroscopy for in-line monitoring of the extrusion process, Macromol. Symp., 230, 51-58 (2005). 

Details are given of the development of an on-line sensor using near IR spectroscoy for monitoring carbon dioxide concentration in polymeric extrusion foaming processes. The calibration curve relating the absorbance spectrum at 2019 nm to the dissolved gas concentration was derived so as to infer dissolved carbon dioxide gas concentration... 

Compared to the time scale of their formation, the carbonyl oxides are quite long lived (10 -10 s), and so their subsequent reactions can be monitored kinetically. For most of the carbonyl oxides, the decay is best fit to a second-order rate law, indicating a bimolecular decomposition pathway. For benzophenone oxide, the ketone is the major product at room temperature, and no dimer can be detected. A bimolecular process involving O2 extrusion from two molecules of the oxides is suggested under these conditions. 

To summarize, while selection and scale-up of extruders is governed by extruder geometry, formulation, and process variables, secondary variables could be used to monitor the process on a continuous basis. Based on the reports thus far in the literature, the variables that seem to play a critical role in scale-up of extrusion are summarized in Table 7. 

Another parameter of interest in the extrusion process is screen pressure, as that has been shown to affect the size of the final pellets as shown in Figure 24 (31). The extruder can be fitted with a suitable pressure transducer to monitor the pressure drop associated with extrusion. One such... 

Little work has been published comparing the shelf life of flavors encapsulated by different processes. The purpose of this investigation was to determine the shelf life of cold pressed orange oil encapsulated by spray drying, extrusion, and molecular inclusion. Limonene-1,2-epoxide concentration was used to monitor oxidation. 

In a 2-year study, the emissions produced during the processing of a series of thermoplastic materials were investigated. In the case of HIPS, the emissions at sheet extrusion and injection molding processes were monitored. Sheet extrusion was done at 193°C, whereas, injection molding was done at 225°C. 

The reaction of MP with 1-methyl- and l-phenyl-2-vinylpyrrole 20a,b afforded 1-substituted indole-4,7-dicarboxylie esters 27 via a further [4 + 2]-cycloaddition to the initially formed 6,7-dihydroindole-4-carboxylic ester 26 by a second molecule of MP, followed by a retro-Diels-Alder extrusion of ethene (80JOC4515). Maximum yields were obtained with 2 1 ratio of MP to vinylpyrrole. The intermediate adduct 26 could not be isolated and when the reaction was monitored by NMR spectroscopy, signals attributable to the dihydroindole-4-carboxylic ester 26 were of very low intensity, suggesting that the second and third steps of the reaction sequence were either comparable in rate or faster than the initial cycloaddition step. 

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