Modification of Precipitated Calcium Carbonate Filler for Papermaking with Adsorption of Cationically Derivatized Chitosan and Carboxymethyl Chitosan

To improve the performance of precipitated calcium carbonate (PCC) as a papermaking filler, the combination of cationically derivatized chitosan and carboxymethyl chitosan was employed as modification agents for PCC. When the dosage ratio of cationic chitosan to carboxymethyl chitosan was 1:2, the two polymers were efficiently deposited onto precipitated calcium carbonate, which showed better retention than the control PCC at the same dosage. The brightness and opacity of handsheets filled with modified precipitated calcium carbonate were markedly improved in comparison to the control. Furthermore, handsheets filled with modified precipitated calcium carbonate reduced the loss of tensile strength compared to the control at the same precipitated calcium carbonate content.