The use of polyelectrolyte multilayers of cationic starch and CMC to enhance strength properties of papers formed from mixtures of unbleached chemical pulp and CTMP. Part I

Abstract

The construction of alternating multilayers of cationic potato starch and anionic carboxymethylcellulose (CMC) was investigated in two parts. In the first part, stagnation point adsorption reflectometry (SPAR) showed that the chosen chemicals formed polyelectrolyte multilayers (PEM) upon adsorption to the silicon oxide surface. This was in accordance with earlier work. The chosen polyelectrolytes adsorbed to similar extents on the silicon oxide surface and recharged the surface enough to allow for adsorption of a consecutive layer. In the second part, the multilayer concept was tested on 80/20, 20/80% of total in mixture of mixed spruce CTMP and bleached chemical pulp in order to enhance the sheet strength properties of a typical packaging board furnish.. The multilayers yielded a significant improvement in Scott Bond values and tensile index and a marginal improvement in tensile stiffness index. The Scott Bond values were improved more than 150% for papers prepared from a furnish consisting of 80% spruce CTMP and 20% chemical pulp. Polyelectrolyte multilayers treatment also led to a slight densification of the sheets, but the polyelectrolyte multilayers treatment resulted in a more favourable density/strength relationship than that achieved with a change in the amount of chemical pulp.