Modification of PCC with agar and its application in papermaking

Abstract

Modification of filler with polysaccharides such as starch, cellulose and their derivatives by preflocculation is an effective means to overcome the main drawback of mechanical strength decline resulting from filler addition. Agar is a mucilaginous polysaccharide extracted from red algaes and was used to modify precipitated calcium carbonate (PCC) for papermaking in our studies. Results showed that when 0.03% cationic polyacrylamide (CPAM) was used as retention aid, tensile index of handsheets using agar (3%, based on PCC) modified PCC as filler was 29.5% higher than native PCC, whereas filler retention did not change obviously. Optical microscope observation and laser diffraction particle size analysis confirmed that PCC was flocculated and coated by agar after modification. Characterizations of mechanical strength and filler retention of handsheets at different filler content indicated the handsheets can be filled with about 10% more agar modified PCC but to maintain the same strength level.