The scraps generated during the processing of mulilayer polyolefins/ EVAL® structures are commonly recycled in a regrind layer for sheet and bottle applications. In some cases, some technical problems may happen such as die build-up, thermal instability （gels）, poor mechanical properties, poor welding or flow instability. Flow instability is occasionally observed in multilayer structures containing regrind, especially in cases where the ratio of regrind is high and/or the EVAL content in the regrind is high. The main cause of flow instability is the poor dispersion of the EVAL resin in the regrind layer due to the incompatibility between the various polymers.
Improvement can be obtained by mechanically creating a better mixing during extrusion （regrind extruder, adapter size）. Also, Kuraray1 R&D has developed the GF-30 resin, an effective compatibilizer, which corrects this flow instability by finely dispersing the EVAL particles in the regrind mixture. GF-30 is also an effective thermal stabilizer designed to prevent regrind degradation. The GF-30 resin is a compatibilizer and a thermal stabilizer for polyolefin-EVAL mixtures.
However, with any set of operating parameters, the information presented here can not be considered absolute. It does contain general operating procedures and recommendations which should provide some guiding lines for effective operation. |
