Calcium Carbonate Composite Fillers, 2004 Paper Summit, Spring Technical & International Environmental Conference, (including Papermakers; Process Control, Electrical & Information; Product & Product Quality)

In this work, PCC-pulp composites are produced by co-precipitating calcium carbonate on top of the non-wood and wood pulps. The composite paper samples are compared with two types of reference handsheets formed by conventionally adding commercially produced PCC (ref-PCC), and PCC-pulps at similar proportion to the composites (ref-blend), to the stock pulp suspension.

The results show that, with increasing filler addition, the paper with composite filler has a lower bulk and similar tensile strength compared to ref-PCC handsheets. The Scott bond strength with composite filler added samples is higher than ref-PCC samples. Internal bond strength is highest for bagasse composite sheets, even higher than the zero filler added reference, followed by pine composite handsheets. Light scattering and opacity are higher for composite filler handsheets compared to the conventional ref-PCC paper. Lower strength and higher optical properties are obtained with composite filler added handsheets compared to ref-blend samples. Light scattering and opacity are higher for composites filled handsheets compared with all types of reference samples.

Scanning electron microscopy (SEM) pictures of the samples show that, in the composite filler, the PCC is spaced along the length of the fibrils, and hence, the highly refined pulp fibers and PCC form a porous network. The adhesion of PCC to the fiber surfaces prevents the cellulosic fibrils from completely collapsing and bonding in consolidation. Thus, in composite sheets a higher fraction of the cellulose surface area is available for light scattering, increasing optical performance.