Why smart dehumidification of resins is necessary
Moretto marketing department highlights the importance of the smart dehumidification of resins and discusses two case studies.
The production of medical products presents multiple challenges to manufacturers, especially injection molders or extruders of plastic medical products. A common headache is the pre-conditioning of hygroscopic resins for processing. Hygroscopic resins are characterized as capable of absorbing moisture into their chemical structure that adversely affects the product’s performance once molded or extruded. To meet product performance standards, that moisture must be removed prior to processing.
The process of moisture removal in resins faces two unique challenges for medical product manufacturers:
- The inability to physically see or confirm resin changes that verify successful moisture removal
- The commonly low throughputs and frequent changes of medical plastic production that often preclude the use of high volume, sophisticated systems designed for large scale dehumidification
Producers of medical products processed from engineering-grade thermoplastic resins face the need to dehumidify reliably, but at lower rates. It is common for medical processors to seek preconditioning equipment that will fit onto the processing machine throat.
In attempt to tackle these multiple problems, a compact drying system called X Comb has been developed by Moretto which is mounted on the machine that incorporates the precision necessary to meet these medical requirements.
This drying system incorporates a compact drying hopper that mounts directly to the throat of an injection molding machines or extruder and is directly coupled to a self-regenerating dehumidification system that employs a rotating desiccant wheel. The wheel contains exclusive zeolite desiccant that is formed into an enclosed honeycomb wheel, providing minimal air flow resistance yet incredibly low dewpoints of -80°F (-62°C).
The honeycomb wheel rotates continuously through resin drying, to desiccant regeneration to desiccant cooling, always providing an efficient flow of dry air for drying the resin. The blowers used for air movement are designed and manufactured for optimized air flow at a wide range of levels to match production requirements. Exclusive turbo-compressors adapt dry air delivery by variable frequency drives to production needs. The result is ‘drying on demand’ and significant energy savings.
Additionally, anti-stress technology is built into the dryer to prevent over-drying of the resin. As the temperature at the top of the drying hopper begins to approach the set-point drying temperature (indicating a production slowdown or stoppage), the anti-stress feature automatically reduces the air flow to the hopper, aligning the drying process to the rate of production, but without reducing the drying temperature.
A more compact hopper, with a special patented geometry and unique thermodynamic properties, called ‘OTX Original Thermal Exchanger’, allows optimal drying performance as each pellet is uniformly subjected to the drying air flow, which dries the resin more quickly for more efficient start-ups.
Fitted with a color touchscreen, controlling the dryer enables the incorporation of a range of external communications. For operation, users input the resin to be dried (from an on-board library) and the production throughput, and the dryer literally does the rest.