Flexographic process

At present, the most important technical objective for the flexographic process is to reduce or eliminate the use of inks based on organic solvent. The research is directed mainly towards improving water-based inks but several reports on the use of UV-cured inks have been published. For applications in which no alternative to solvent-based inks is available at present the trend is towards eliminating hydrocarbon solvents. 

With the flexographic process, water-based inks can be used on paper (original aniline dye process) where adsorption forms part of the drying process. 

Strip plies are usually printed by gravure or flexographic processes either on or off the strip pack machine. Registration is usually carried out on one ply. Repetitive printing is frequently employed, i.e. three repeats to two pocket areas, so that one full print will appear on each unit. 

Anilox roller. In the flexographic process ink is transferred from the ink fountain by a rubber transfer roller onto the anilox roller. The latter is usually an etched or patterned roller, giving cells of constant depth and size, from where it is trans ferred to the relief plate (cylinder), without the ink being squashed over the sides of the relief characters. 

Coating thickness limitations are inherently defined by the flexographic process. When engraved anilox rolls transfer coatings to printing plates and in turn to substrates, the process rarely delivers less than 19% or more than 24% of the cell s wet coating content to the substrate surface [3]. There are therefore clear boundaries as to the amount of coating that can be delivered to a substrate surface. These boundaries are defined in Table 9.2. 

Western Michigan University Web Site http //www.wniich.edu/ppse/flexo/, Flexographic Process... 

Inorganic chemicals may also be used. Beatonite may be used as a flocculant ia combination with polymer treatmeat. Alum, oace a common coagulant, is less used because its concentration can build up ia recycle water. Alum oftea biads ink to fibers and iacreases the difficulty of deinking. Removal of the very small flexographic ink particles ia process water is difficult. Ultrafiltratioa (qv) has beea proposed for removing these very small dispersed ink particles (53). 

Figure 12.11. A simple representation of the process and components associated with four common graphic arts printing technologies screen, flexographic, gravure, and lithographic printing.

Roll-to-Roll Printing Processes Gravure, Flexographic,... 

The conditions to be met in decorative printing are particularly demanding. Decorative papers for gravure and flexographic printing are used to produce laminated plastic sheets. Pigment selection is a matter not only of the type of resin (melamine or polyester), but also a function of the processing method. 

Michler s Ketone as the sensitiser and chlorophenyl-bis-trichloromethyltriazine as the radical photoinitiator. In the flexographic plate process the monomers are mono-and multi-fnnctional acrylates, e.g. butanedioldiacrylate, and the photoinitiators are radical prodncers, e.g. benzildimethyacetal, nsing UV-A (350-370 nm) light. 

Flexographic printing inks are similar to those used in gravure processes but have a somewhat higher carbon black concentration (10-15%). 

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