Development of Hybrid Calcium Carbonate for High Loading Paper (III) - Post Hybrid Calcium Carbonate -

High filler loading in printing paper is desirable for papermakers because they can reduce production cost and carbon dioxide emission, if all the paper properties are acceptable. Two new filler preparation methods were presented and compared in this study. The hybrid calcium carbonate (HCC) was prepared by the in-situ calcium carbonate (CaCO₃) formation on the pre-flocculated mixture of grounded calcium carbonate (GCC) and calcium oxide particles in aqueous medium. For the preparation of ‘Post HCC’, only GCC particles were pre-flocculated firstly, calcium oxide was added to the pre-flocculated GCC secondly, and carbon dioxide were introduced lastly until the pH of the aqueous medium becomes neutral. Both methods increased tensile strength, stiffness, and bulk, but kept smoothness when compared to the case of simple GCC addition at equivalent ash level in the handsheet study. Post HCC gave higher solid content and higher stiffness than HCC.