Böttcher Golden Pearl, a New Innovative Coating for Distributor Rollers

With Golden Pearl, Böttcher presented on Drupa a totally new special covering for ink transfer and distributor rollers. Up to now, offset printers have worked as a rule with Rilsan-coated steel or aluminium rollers in the ink transfer and distributor roller positions.

In modern presses, the temperature in many of these rollers is controlled by circulating water in order to maintain constant temperatures in the printing couple. The copper-coated distributor rollers still used in some presses more effectively support heat transfer compared to Rilsan-coated rollers.

Copper, however has other disadvantages, when in contact with ink and fountain solution, which have prompted most press manufacturers to opt for Rilsan instead of copper. Rilsan is a polyamide which is highly resistant to the chemicals used in the printing process. But it, too has its disadvantages. The production process, which involves thermoplastic powder coating or hot-spraying, requires subsequent machining in order to achieve the narrow production tolerances specified for offset printing.

This produces a degree of surface roughness that provides crystallization points for accumulating deposits. Every printer had encountered a Rilsan roller that no longer has the desired ink-friendly surface due to deposits of paper coating dust, ink or water residues.

Attempts to clean such rollers often require a great deal of effort and, if they are successful at all, then only for a very short period of time. Aggressive agents must be used to remove the hard deposits. The surface may be clean after treatment, but the mechanical and chemical attacks leave behind a surface that is even more susceptible to the accumulation of new deposits.

Golden Pearl is different: The steel or aluminium base material is milled to the required geometric tolerances. Then, a uniformly thick (40-70µm) layer of a high-tech plastic is applied. This layer is heat-cured and needs no further processing. In this way, we obtain a very smooth surface that offers no points of attack for deposits.

This very smooth surface promotes outstanding ink transfer and considerably facilitates cleaning. It is also chemically inert and resistant to the substances used in the printing process and thus to coating residue accumulation and other deposits. Because of its good abrasion resistance and high impact stability, a very thin layer is sufficient. The layer thickness, which amounts to only about 10-15% of the normal Rilsan layer, enables the Golden Pearl coating to achieve a much higher level of thermal conductivity. This minimizes the energy input required to cool the distributor rollers while providing for more rapid control of printing units temperature.

Golden Pearl is also suitable for UV and UV mixed mode printing applications. Due to its excellent heat resistance (up to 300°C), which is extremely high for a plastic, the use of the Golden Pearl coating in special technical applications outside the printing industry is possible as well.