Direct addition of CaCO3 (Calcium Carbonate) is a method used in plastic pipe extrusion, particularly for non-pressure pipes and foam core pipes, to modify formulations and achieve cost savings.
Adding fillers like CaCO3 allows replacement of polymer material. This lowers the amount of fossil fuels used per pipe length, contributing to sustainability. For high-filled dry blends, the formulation is cheaper, and a stiffer material (due to higher E-modulus with CaCO3) can result in a thinner wall while maintaining the required stiffness.
CaCO3 can be added directly using dosing feeders and potentially an Intermixer. This allows for flexibility in adjusting the CaCO3 level in the formulation. Adding higher levels of CaCO3 in the core of foam core pipes can help achieve required stiffness and may even permit adding more blowing agent without creating blisters, leading to further weight and cost saving.
High filled dry blend can present pourability problems, requiring assistance like pneumatic knockers or stirrers in hoppers. CaCO3 can also turn into blackboard chalk under pressure, potentially stalling a vertical crammer feeder. Rollepaal offers a volumetric self-wiping co-rotating double screw dosing feeder or a gravimetric double screw feeder for CaCO3 direct dosing. CaCO3 increases stiffness proportionally to the amount added.