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.
Benefits and Implementation
Cost Reduction
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.
Formulation Flexibility
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.
Processing Considerations
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.
FAQ Section
What are the main benefits of using direct CaCO3 dosing in pipe extrusion?
Direct CaCO3 dosing allows for cost reduction by replacing more expensive polymer material. It also increases stiffness, potentially allowing for thinner pipe walls for the same stiffness requirement. This also reduces the amount of fossil fuels per pipe length, contributing to sustainability.
What equipment is typically used for direct CaCO3 dosing and what are potential challenges?
Direct dosing is often done using dosing feeders, which can be single or double screw, volumetric or gravimetric. An Intermixer may also be used. Challenges include pourability issues with high-filled dry blends and potential stalling of vertical crammer feeders due to CaCO3 behavior under pressure.
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Albert Vaartjes
