Nitrogen Drying for Specialty Resins
Dryer introduces an inert gas or nitrogen to inhibit the oxidative degradation of polymers.
Novatec has taken the wraps off a new Nitrogen NovaDrier. Developed in response to increased use of polymers with unique properties that can be diminished if not handled properly during the drying process, the dryer introduces an inert gas or nitrogen to inhibit the oxidative degradation of polymers. Resins that tend to degrade with prolonged exposure to heat in the presence of oxygen include nylons, PBT, PLA, and TPUs. A loss in properties due to oxidation occurs more readily in the presence of the heat used in drying.
Each polymer has different limits on temperature and the amount of degradation that occurs with exposure to heat and oxygen during drying. Typically, the drying temperature can be 10-50° F higher with a nitrogen source in lieu of air, allowing for shorter drying times. These shortened exposures lead to better polymer performance in terms of strength, ductility, color/clarity, viscosity, chemical resistance, stiffness, and stability.
Using nitrogen in dryers is not altogether new. This dryer is unique, however, in that it requires no handling of cryogenic nitrogen or bottles. There isn’t any need to have both the handling and risk of using bottled nitrogen. This dryer uses standard plant compressed air as the feedstock, from which it extracts the nitrogen for drying, so only air is released from the dryer unit (in two streams, one oxygen-rich, and one nitrogen-rich). This approach eliminates the hazards involved with venting of nitrogen into a closed area. It can be used anywhere without special procedures or handling, Novatec says.
U.S. injection molders are still pretty green when it comes to processing the new crop of renewably sourced biopolymers. These biologically derived polymers made from PLA, PHA and starch-based resins are attracting growing market interest as materials with no ties to petrochemical-based thermoplastics.
To dry your polymer correctly you need a dryer that is properly designed and working properly. Here are my suggested specifications, for a two-, three- or four-bed desiccant dryer, the most common types used.
Drying is complicated.