SABIC is exploring use of dry ice (solid carbon dioxide) as a coolant and plasticizer to reduce processing temperatures to process high-temperature plastics.
The approach makes it possible to make certain types of articles from neat PAN, neat PPO, and neat polyvinyl chloride. Use of dry ice reduces energy costs and boosts productivity for other tough-to-process plastics.
“Polymers having a high viscosity and/or a high glass transition temperature can be challenging to process via injection molding or extrusion”, states the patent. “High temperature and high pressure are often needed in order to process these materials…Often with such polymers, the temperatures needed for melt extrusion overlap with the degradation temperature.”
PVC cannot be extruded without thermal stabilizers and/or lubricants. PTFE can only be processed via ram extrusion.
In the SABIC invention, neat plastic and solid carbon dioxide are mixed in the hopper of a vented extruder and then plasticized to form a polymer melt with dissolved carbon dioxide. The dry ice cools the polymer melt and then is vented as gas before the die.
A U.S. patent for the technology was awarded today.