Catalytic debinding

The rate of depolymerizing polyacetal to formaldehyde is the subject of much research, because the rate of depolymerizing is a critical factor in MIM costs, and there is not that much proven information on it. Removal of binder is determined by various factors, namely, binder removal temperature, about 120°C (248°F) catalyst linear or random degradation of polyacetal resin fineness of powder mold part shape and size and catalytic debinding furnace. The catalytic furnace developed for debinding... 

TER 93] TER MAAT J.H.H. and EBENHOCH J., Feedstock for ceramic injection molding using the catalytic debinding process , 3" Euro Ceramics Proceedings, Faenza Editrice Iberica S.L., vol. 1, p. 437-442,1993. 

Fig. I. G-protein catalytic cycle. Debinding of GDP and binding of GTP follows interaction of the inactive complex with the ligand stimulated receptor (R). The active G .GTP complex and the complex are able to activate effectors, which include both enzymes and ion channels. Deactivation occurs as a consequence of a slow intrinsic GTPase activity manifest by G leading to G .GDP which recombines with Gp., to give the inactive G g. GDP heterotrimeric complex.

In order to eliminate flaws inherent to thermal debinding and to shorten the duration of this stage, other techniques for the extraction of organic shaping additives have been developed. These techniques are based on an under- or overpressure of the treatment atmosphere, on microwave heating, capillary migration of molten binder, sublimation of a binder in aqueous phase, or solubilization by catalytic reaction or solvents. 

This technique applies to particular binders that exhibit specific degradation (catalytic) mechanisms in certain atmospheres. BASF (Germany) has developed an injection formulation containing polyacetal binders, which are eliminated at 110°C in acid atmosphere (98% nitrogen + 2% nitric acid). This atmosphere leads to the sublimation of a part of the polyacetal binder and the crystallization of the remaining part. However, sublimation vapors reqnire a reliable reprocessing before their evacuation into the air and the debinding furnaces must have an anticorrosion treatment in order to resist nitric acid fumes. 

---