A major application area for which the Marcus polyethylenes are well suited when in the appropriate form (dispersion, micronized, and emulsion) is for addition to letterpress, lithographic, screen, gravure and flexographic inks. Also, particularly for the micronized grades, in overprint lacquers / varnishes.
The nature of the wax for addition to printing inks is very important as it has to be of the correct structure, molecular weight and distribution in order to have a regular and fine particle size, and also possess adequate hardness to give optimum results. For example, if the structural features do not have the right balance, the particle size will be too large which will lead to an unacceptable reduction in film gloss, resulting in poor performance, particularly in offset inks where the film thickness is around 5 microns. Further, if the wax is too hard then the inherent brittleness can give rise to a powdering problem.
The MARCUS polyethylenes have a very good balance of properties which single them out for imparting valuable high performance attributes in inks whether it be from dispersion or from micronized and emulsified forms. The optimum results are secured with an addition level as low as 0.5% (on total ink solids). Broadly, the advantages are:
- Rub resistance improvement.
- Slip and anti – blocking properties.
- Minimum gloss reduction.
- Tack reduction.
- Reduced smudging tendency.
- Better abrasion and scratch resistance.
Modification of rheological characteristics.