VISCOSITY BEHAVIOR OF MULTIVALENT METAL ION-CONTAINING CARBOXYMETHYL CELLULOSE SOLUTIONS

The influence of Ca2+ - and Al3+ -ions, respectively, upon the viscosi ty behaviour (so-called salt tolerance) of aqueous solutions of sodium carboxymethyl cellulose (CMC) with different degree of polymerization (DP) and, on the other hand, with both different degree of substituti on (DS) and distribution of substituents, was investigated. Viscosimet ry by means of a rotational rheometer at a shear rate of 500 s-1 shows that the relative drop in viscosity as a result of addition of the mu ltivalent metal cations is independent of DP (ranging from 160 to 900) of the CMC samples. Homogeneously synthesized CMCs (2) with a higher content of 2,3,6-tri-O-carboxymethyl glucose units in the polymer chai n possess a significantly higher salt tolerance than those (1) prepare d under heterogeneous reaction conditions at comparable total DS value s.