Annealing printing ink in the drying oven

UNION-KLISCHEE are specialists in screen printing, pad printing, digital printing and etching technology. As orders coming from the fields of medical technology, measurement- and sensor technology or precision engineering require prints to have especially high wear resistance, the print colours are annealed in a Memmert drying oven.

Pad printing and screen printing quickly explained 

During screen printing, a printing stencil, which was photographically exposed, only lets colour pass at the desired locations. The colour is poured on a fine-mesh sieve and evenly spread with a doctor blade - a so-called squeegee. Especially the variety of printable materials, the luscious colour application and the use of special colours for effects or functional properties such as weather, scratch and wear resistance, still make screen printing an important printing process. 

During pad printing, an indirect offset printing process, the motive is etched into a printing plate - the so-called cliché - and then exposed. The colour is applied on the etched image and a squeegee strips off the excessive colour. Afterwards, a pad made of elastic silicone absorbs the colour and prints it on the substrate. As the pad is deformable and can adapt to the shape of the printing surface, e.g. a computer mouse, concave or convex surfaces can also be printed on.

2K colours for increased wear and chemical resistance

Colours basically consist of four components: pigments, binders (that bind the pigments to the surface), solvents (that evaporate after the printing process so that the colour becomes solid and dry) and accessory agents for the desired functionalities, such as strength and elasticity. Solvent-containing print colours, which are predominantly used during screen and pad printing, dry by physical vaporisation and form a solid colour film. On surfaces that are not absorbent and if the prints have to be highly resistant (e.g. for medical products that can be sterilised), print colours (mostly 2-component colours - so called 2K colours) often are thermally annealed. At UNION-KLISCHEE, these colours are used mainly for industrial metal parts.

Annealing print colours in a drying oven 

Shortly before printing, a hardening additive is added to the 2K colours. In a Memmert drying oven UN450 with natural convection, the annealing process (the chemical cross-linking of hardener and binder) is fast and requires little space. Depending on print colour and application, the temperatures vary between 60 and 140 °C. The annealing time is between 15 and 60 minutes. In daily use at UNION-KLISCHEE, the heating oven scores mostly because of its quick temperature and time adjustment options, electronically controlled exhaust air valve, temperature stability and reliability.

Furthermore, UNION-KLISCHEE uses the Memmert drying oven UN450 in the field of etching technology, where finest structures have to be etched into thin sheets and metal foils. During the tempering process, the bond between thicker materials (e.g. stainless steel) and the laminate is cured and strengthened.

The text of this article is based on information provided by UNION-KLISCHEE Berlin. AtmoSAFE thanks marketing manager Berit Matschke for her kind assistance.