2. Safety and Hygiene Precaution
2.1 Precaution in Molding
||Set the following material temperatures and dwell time in the cylinder so as to avoid decomposing materials:
• The appropriate material temperature : 190-210°C
(Never heat up to 250°C or higher)
• Dwell time in the cylinder
||Maximum dwell time
When molding is temporarily stopped, purge the material from the cylinder and lower the cylinder temperature. If overheating is observed or suspected, lower the cylinder temperature and purge the overheated material by feeding a new material. In this case, gas emission is restrained if the purged melt is immersed in water and cooled. When purging, wear protective glasses and gloves and do not bring your hands and face close to the nozzle tip. Do not allow vinyl chloride resins or halogen type fire retardants to mix with DURACON® POM in the cylinder, as they accelerate the thermal decomposition of DURACON.
||Partial or total ventilation in a molding shop is recommended during molding operation.
||Since pellets scattered on the floor may cause operators to slip and fail, it is recommended that they be removed at once by cleaning.
Formaldehyde gas is irritating, especially to the eyes and throat, and inhaling the gas over a certain level of concentration for a long period of time is dangerous. For this reason, partial or total ventilation is recommended during operation. Although differences between individuals make it difficult to determine the detection threshold of formaldehyde gas, it is thought to be approximately 0.05-0.06 ppm. The maximum permissible quantity of formaldehyde recommended by the Japan Society for Occupational Health is 0.1 ppm per eight-hour work shift, whereas the maximum permissible concentration of formaldehyde provided in the U. S. is 0.75 ppm.
2.3 Starting Up, Shutting Down and Changing of Materials
(1) If the material previously used was DURACON
Molding can be started after the heater is turned on, the cylinder temperature and nozzle temperature have reached the specified level, and the cylinder is purged several times. In this case it is necessary to confirm that the nozzle is open. (This can be confirmed by checking for drooling from the nozzle.) When stopping molding operations while the cylinder is being filled with DURACON, stop resin feed, carry out purging until no resin is discharged from the nozzle, then turn the heater off.
(2) If the resin used in the previous operation was not DURACON
(a) When the resin can be replaced directly with DURACON
Resin which can be molded within the same temperature range and which has the same superior thermal stability as DURACON – as polyethylene, polypropylene, polystyrene, and AS resin – can be replaced directly by DURACON.
(b) When the resin must be replaced with polyethylene, polystyrene or polypropylene, and then with DURACON
Resins with higher molding temperatures such as polycarbonate, nylon, PBT, PET, PPS or LCP, as well as resins such as polyvinyl chloride, which have lower molding temperatures and could decompose at molding temperature of DURACON, cannot be replaced directly with DURACON. In this case, the replacement procedure is as follows. After the cylinder is heated to the proper molding temperature of the resin, the resin to be purged is replaced once with polyethylene, polystyrene or polypropylene, and then polyethylene or polystyrene is replaced in turn with DURACON after the proper molding temperature for DURACON has been reached.
(c) When the previous resin is difficult to replace
If the resin to be replaced has a dark color such as black and the color cannot be easily replaced, it is recommended that the cylinder be cleaned with a natural resin containing glass fiber and then cleaned with a commercial cleaner.
(3) Replacement of DURACON with another material
Replace directly with the material if it has the same molding temperature as DURACON. However, if the resin has a different molding temperature, replace DURACON with polyethylene, polystyrene or polypropylene, then change the temperature and replace with next molding material.