Resin trap

A distributor is frequently installed at the top of the column for use during backwash. It collects water evenly and prevents resin from escaping the column should unexpected surges develop in the water flow during backwash. Columns lacking an upper distributor or screen to prevent loss of resin should have an external system to prevent resin from being lost to the drain. It is referred to as a resin trap and may consist of a porous bag that fits over the outlet pipe or a tank designed to lower the linear velocity. Resin drops to the bottom of the tank and is returned to the column when convenient. 

Woodrow, J.E. Seiber, J.N. Portable device with XAD-4 resin trap for sampling airborne residues of some organo-phosphorus pesticides. Anal. Chem., 1978, 5 , 1229. 

The apparatus is shown in Figure 8. The tube containing the adsorbent (3) is placed in adaptor (1), and microfunnel (2) is used to direct solvent into the adsorbent tube. A 5 ml pear-shaped flask is placed at the lower end of adaptor (1), while a microspiral condenser with drip tip is placed at the upper joint. Solvent is allowed to percolate through the trap until about 0.5 ml collects in the pear-shaped flask. Then this solvent is brought to reflux and the resin trap is continuously extracted for 10-15 minutes. Finally, the apparatus is disconnected and distillation used to reduce the volume to about 75 microliters. 

Figure 8.6 Typical fixed bed. A, feed B, effluent C, backwash supply D, backwash overflow to resin trap E, eluant supply F, spent eluant G, distributor manifolds H, resin removal line I, access hole J, drain K, pressure gage and vent [1], Copyright 1987 John Wiley Sons, Inc. This material is used by permission of John Wiley Sons, Inc.

The volatiles from crushed neem seeds were purged with nitrogen, trapped onto Amberilte XAD-4 resin traps at room temperature, recovered and concentrated Into diethyl ether using a Kuderna-Danish evaporative concentrator at 30 "C, and analyzed by means of capillary gas chromatography/mass spectrometry (GC/MS). For comparative purposes, similar volatile concentrates were prepared from freshly chopped onion bulbs and garlic cloves, and blank controls were simultaneously prepared for each of the three test samples. 

Holes in parison and/or bottles Contaiminated or degraded resin Trapped air Moisture in resin Purge and clean tooling and screw Let extruder run for a few minutes Dry the resin... 

The general setup for trapping a reaction intermediate is shown in Scheme 11-1. The solid phase (I) (resin precursor) can be activated by a suitable reaction to give the low-molecular-weight reaction intermediate, which is soluble and can pass into the liquid phase (solvent). The liquid phase is also in contact with another solid phase (II) (resin trap) so that the reaction intermediate reacts at once with the second resin to give an adduct. The trapped intermediate can either be identified on the resin itself or after cleaving it from the resin. This three-phase approach is best illustrated by the following examples. 

The venting of the mold can also be important for the process control. In vacuum-assisted processes, the vacuum pump stays active during the entire injection process and is protected from penetrating matrix material by a resin trap. If a plastic tube is used for this venting line, the moment the resin flows out of the mold can be easily recognized. If more lockable exits of a cavity are used, an online flow path control can also be realized in ciosed mold concepts. The construction of a closed injection mold with two fixed moid haives is dependent on which effort for the actual application is justified or necessary for the process-related implementation. 

It is not usually possible to monitor solid phase reactions with the standard solution phase chromatographic techniques (TLC, HPLC) because the reaction components are either tied up by the solid phase or present in large excess. However, in a special case, Xiao et al. were able to follow the consumption of a precious solution phase taxoid intermediate as it reacted ( resin-trapped ) with excess resin [39]. 

---