Price: 10.00
The graphic arts industry has an ongoing need to modify and control the
rheology of energy curable inks. Rheology modifying (RM) resins allow me
industry to enhance rheological properties of lithographic, letterpress and screen
ink printing processes which currently incorporate silica, talc and other additives.
Increasing rheological body significantly in printing inks is difficult with existing
acrylated resins, even with the incorporation of nonreactive, powder type
additives. In addition, these additives impart detrimental side-effects in most ink
systems. RM resins offer the industry an alternative to the conventional methods
for controlling rheology.
Lithographic, letterpress and screen inks are high viscosity inks which need
to be completely formulated prior to printing on a 1 Hence, rheology control
is important because adjustments are difficult to make during a press run. Most
high viscosity inks have a paste like consistency. During a press run, ink is
affected by increasing shear and temperature so that its viscosity and consistency
decrease causing it to flow freely. To achieve optimum printing properties, the
tendency of an ink to flow needs to be controlled.
Some critical printing ink properties are: viscosity, yield value, thixotropy,
flow, color development, printability, sharp printing and tack1. These properties
are directly related to the formulation of the ink system. Typically an energy
curable lithographic ink formulation contains 40-60% resin. Overall ink
performance is characteristic of the oligomeric backbone comprising the
formulated system and thus, selecting the right resin is a critical task for the
formulator2. Currently, there are no available energy curing resins on the market
which possess inherent gelling or thixotropic capabilities. A gel like structure or
consistency is usually obtained within an ink by adding silica, talc, clay and other
nonreactive, powder type additives. Some problems associated with the use of
these additives include:
o increase in viscosity with time resulting in inconsistent flow
o significant reduction in gloss and
o respiratory hazards due to the creation of dust.
