Micro necking

Halfte/Anteil/Teil moiety Hals/Tubustrager micros neck Halsbildung polym... 

The preparation was carried out in a dried 250 ml three-necked flask equipped with a nitrogen inlet, magnetic stirrer, reflux condenser, micro-dropping funnel and recording thermocouple. The reaction flask was immersed in a constant temperature bath (25°C) and 100 ml of the 2,4-tolylene diisocyanate (TDI) were placed into the flask. When constant temperature was reached in the flask, one ml of a solution of a catalyst in acetonitrile was added dropwise to the reaction mixture and the resultant mixture was intensively mixed for 4 hours. The reaction product was analyzed by GPC and the conversion was determined by the dibutylamine method. 

Crystals can be dried in any of the usual types of apparatus, such as the Abderhalden drying pistol or the variant described by Smith,82 or on a Benedetti-Pichler drying block. However, simpler apparatus also suffices 100-ml or 250-ml wide-necked flasks with well-fitting ground glass joints can be used as, e.g., micro desiccators and a wide glass tube closed by a stopper and tap (Figure 18) can serve as a vacuum-desiccator that can be heated. 

---