This plastic is used for the production of vinyl film, sheeting, and vinyl-impregnated cloth. The batch mixer are used to feed callendering process. The callendering process consist of large multiple rolls than flatten the mixed dough like plastic into flat sheets. The thermoplastic materials of PVC, vinyl acetate, polyethylene, polypropylene, ABS and impact modified polystyrenes are the most often used. The thermoset materials of melamine and urea are also batch mixed and then rolled into flat stock for grinding into molding powders.
Batch mixers consist of an enclosed steel chamber with internal rotating and intermeshing blades.
The rotating blades smear the material against the container wall while it shears and kneads the material at the center. After the cycle is complete, the glob of mixed material is then discharged, ready for callendering into sheets or processing into molding powder or pellets. A variation of the batch mixer is the Banbury mixer developed in 1916. The Banbury mixer uses two spiral shaped rotors and can be easily fed material through the top. When material is discharged the batch is complete and exits through a door at the side.