Ij. Mclennan et R. Pelton, SOME FACTORS INFLUENCING THE MORPHOLOGY OF FLEXO INK CALCIUM SOAP PARTICLES, Journal of pulp and paper science, 23(6), 1997, pp. 263-269
The reaction between CaCl2 and various types of fatty acid soaps has b
een studied by dynamic light scattering (DLS), transmission electron m
icroscopy (TEM), light microscopy, and chemical analysis with regard t
o the formation of colloidal particles and microscopic particles. The
ratio of calcium to soap determines whether the particles formed small
colloidally stable particles or larger precipitates. At high ratios o
f calcium to soap, the reaction between calcium and soap was found to
be stoichiometric and reached equilibrium rapidly (< 4 min). Calcium s
oap particles at low calcium to soap ratio (colloidally stable) were m
ade and examined by TEM. Particles made with pure sodium oleate formed
more regular structures with a narrow size distribution, whereas part
icles made from soap mixtures (containing saturated and unsaturated fa
tty acids) formed more amorphous structures of various sizes. The reac
tion between a dispersed ink (flexo ink) and pre-made calcium soap par
ticles was studied by light microscopy. The deposition of flexo ink on
to the calcium soap particles was found to be very dependent on the fr
ee calcium ion concentration in solution at 50 degrees C. At low calci
um ion concentrations (< mmol/L), flexo ink did riot deposit onto the
calcium soap particles, whereas at calcium concentrations between 1.5
and 4.4 mmol/L, several different aggregation processes (leading to di
fferent structures) occurred in the mixture. The structures varied fro
m small (< 50 mu m) homocoagulates of flexo ink to large (> 300 mu m)
aggregates of flexo ink and calcium soap particles.