Oven, flash-drying

Moisture. Transfer an accurately weighed portion of approx 1 g of the flash charge compn to a tared moisture dish 2 inches in diameter. Place the moisture dish and contents in a drying oven at 80°—85 °C for 2 hours, cool in a desiccator and weigh. Calculate the loss in weight of die dish and contents to percent moisture in die sample... 

After the preform had been felted from a water slurry, it was compacted at atmospheric pressure, removed from the die dried at 140°F in a steam-heated, circulating air oven. The dried preform was then soaked in the impregnating resin soln, drained, and finally flash-dried in a vacuum oven to a point where it could be post formed... 

After a very short flash-off time (3-10 s), the coated metal passes through a drying oven, which can be up to 50 m long. Drying time is 20-60 s at 180- 260°C, depending on the coating type. 

It has been found that if the oven is powered by a combustion process, some of the carbon dioxide that is generated in such a process might be absorbed on the plate surface such that the surface becomes harder. The elevated temperature of the flash-drying process also helps start the curing reactions. Small plates are usually stacked horizontally on pallets and thicker, larger plates are usually placed with the long edge upward in racks. 

Purification. The commercial LDPE was dissolved in hot toluene and precipitated in methanol. The resulting small chips were dried in a vacuum oven overnight at 80° C. HDPE was purified in the same manner, except that in this case much of the commercial material was insoluble in toluene, and so significant fractionation apparently occurs during t.he purification. The model compounds were purified by the flash chromatographic technique of Still et al. (10). 

A 1-L, oven-dried, round-bottomed flask equipped with a magnetic stirrer is charged with 9.92 g (27.9 mmol) of methyl R)-3-(tert-butyldiphenylsilyloxy)-2-methylpropionate and 200 mL of dry hexanes (Note 15). The solution is cooled to -78°C, and 31.5 mL (31.5 mmol) of 1 M diisobutylaluminum hydride (in hexane) (DIBAL-H) (Note 16) is added dropwise over 15 min via a syringe pump. After the addition is complete, the resultant solution is stirred at -78°C for 2 hr. The reaction is quenched by pouring the cold solution info 250 mL of saturated aqueous Rochelle s salt. Ether (300 mL) and HjO (75 mL) are added and the biphasic mixture is stirred vigorously for 1 hr (Note 17). The layers are separated and the ether layer is washed with brine. The aqueous layer is extracted with ether (2 x 50 mL) and the combined extracts are dried over Na2S04. Filtration of the solution and concentration of the filtrate under reduced pressure followed by purification of the crude product by flash chromatography (Note 18) yields 7.85 g (86%) of (R)-3-(tert-bUtyldiphenylsilyloxy)-2-methylpropanal as a white solid (Note 19). 

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