Resin handling

Peptide synthesis resins are extremely fragile and the beads, if wrongly handled, can easily fracture, leading to the generation of fines which can block reaction vessel filter-frits and solvent lines. 

All resins must be swollen with an appropriate solvent before use, with the exception of PEGA resins which are supplied as a slurry in methanol or water. Underivatized polystyrene resins do not swell particularly well in dimethyl-formamide (DI ), hence the resin must be first swollen in dichloromethane (DCM). In contrast, PEG-PS resins can be packed dry into the reaction vessel and be swollen directly with DMF. In continuous-flow instruments, pumping the solvent up the reaction column is an effective way to remove air bubbles trapped in the resin bed. 

Resins are normally washed between reaction steps with DMF as it is an excellent solvent both for protected amino acid derivatives and for most reagents used in peptide synthesis. 

At the end of the synthesis or before long-term storage, resins must be shrunk and dried to remove all traces of solvent from within the resin particles as described in Protocol 1C. Many resins, when dry, adhere strongly to glass and plastic surfaces, making it difficult to remove the last traces of the material from the reaction vessel or filter funnel. Any resin remaining after removal of the bulk of the material can be washed with DMF down into the bottom corner of the filter-frit, washed with DCM, being careful not to spread the resin back up the sides of the vessel, excess DCM removed, and the damp resin removed with a spatula. 

PEGA resins must always be handled in the swollen state as the resin beads have no structure when dry. Following chain assembly the resin can be washed successively with DMF and DCM, excess DCM removed, and the resin transferred to the cleavage reactor as a damp cake. 

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We have previously described the basic resin handling and washing procedures, as well as nitro group reduction, cyclization with aldehydes to form the benzimidazole ring, and chemical encoding procedures for a related benzimidazole system.18 Reagents and solvents used are available from Aldrich (Milwaukee, WI) and Calbiochem-Novabiochem (San Diego, CA). 

The GPPS and HIPS reactor sections each contain several polymerization reactors in series, two-stage devolatilization and a pelletizing line. The devolatilization equipment is designed to deliver polystyrene product with a concentration of residual total volatile material (TVM) of less than 100 wt-ppm. Common equipment includes sections for feed preparation, SM recovery, water removal and bulk-resin handling. 

Solid Resin Handling. When the molten resin is discharged from the autoclave at IOO-150 C, it must be cooled rapidly, especi ly in the case of the one-stage resin, to prevent further reaction. Rapid cooling requires that thin layers be spread because the thermal conductivity is low a typical novolac resin has a thermal conductivity of 0.13 Btu/(hr) (sq ft) ( F) aUd a specific heat of 0.33. Water- or air-cooled floors, tra3W in racks, and moving belts have been used to cool the resin. 

Any large-scale resin handling system has three basic subsystems un-... 

If computer-integrated resin handling systems are considered, one must compare their operating procedures with one s process requirements. These process requirements describe the flow of resin and product through the system, which determines the system s electronic architecture. Pertinent considerations include batch vs. continuous operations, the type and number of conveying lines, resin storage and distribution, quality control means and procedures, inventory control, the type and quantity of process parameter sensors, the type and quantity of controlled devices, modes (automatic, semiautomatic, manual, and/or shutdown modes), process information, process management controls, and centralized vs. local operation (Fig. 9-1). 

Resin Handling characteristics Final part properties Typical applications... 

Resin Handling Characteristics Final Part Properties Typical Apphcations... 

Resin manufacturers usually provide health and safety information through Material Safety Data Sheets (MSDS) that discuss resin handling and storage, toxicity, combustibility, disposal, labeling, and FDA status. 

Any large-scale resin-handling system has three basic subsystems, for unloading, storage, and transfer. For a complete system to work at peak efficiency, processors need to write specifications that fiilly account for the unique requirements of each subsystem. The least efficient component, no matter how inconsequential it may seem, will limit the overall efficiency of the entire system. 

Extrusion is used in four major plastic processes, including twin-screw compounding, blown film and sheet, tubing and pipe, and profile extrusions. Each of these extrusion operations has a resin handling system, drying system, extruder, shaping device, cooling device, and take-up device. 

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