The Universal Selection Source: Polymer Additives

Precipitated Calcium Carbonate – Multifunctional Additive for PVC: Techno Brief

Calcium carbonate is one of the most widely utilized minerals. Ground calcium carbonates (GCC) are used mainly as fillers, while precipitated calcium carbonates (PCC), in addition to being reinforcing fillers, can function as a processing aids and impact modifiers as well. This Precipitated Calcium Carbonate guide is designed to help you understand more about the use of PCC in PVC polymer, focusing on the benefits and main applications.

Precipitated Calcium Carbonate Production

Precipitated calcium carbonate is produced using the most economic process existing today. Limestone is converted into calcium oxide and carbon dioxide by means of calcination at temperatures in excess of 900°C. To ensure a high level of purity, the calcination process is carried out using natural gas. After the calcined lime has been slaked with water, the resulting milk of lime is purified and carbonated with the carbon dioxide obtained from the calcination process (See reactions below).

Figure 1

Following total carbonation, a suspension of CaCO3 results. A cake comprising 40% - 60% solid matter (depending on particle diameter) is then obtained by filtration. This filter cake is then dried and subsequently deagglomerated in grinders. Ultrafine PCC grades are reacted with fatty acids prior to filtration i.e. when still in the suspension stage.

The fineness of the grain, as well as the crystal form (aragonite, calcite), is controlled by temperature, concentration of reactants and time.

Depending on the chemical composition of the milk of lime used and on the purifying stages during production, both technical as well as foodstuff and pharmaceutical grades can be produced.

Figure 2

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