Printing flexo

Wash deinking often used for flexo-printed waste and in older tissue mills, large water consumption. Flotation deinking for oil-based printings such as offset and rotogravure, technology from the mining industry. 

In applications where the pigment is fast enough to solvents to satisfy the requirements, it may also be used for offset, packaging gravure, and flexo printing inks. The resulting prints are soap, alkali, and acid resistant. They are not completely fast to paraffin and quite sensitive to butter and a number of other fats. P.R.14 prints are not fast to clear lacquer coatings and may not be sterilized. Heat stabil-... 

P.R.17 provides medium reddish shades. As a result of poor fastness properties, its commercial significance is somewhat limited and it is sold only in small volume. P.R.17 has the advantage of being fast to acid, alkali, and soap. It is therefore used in offset, gravure, and flexo printing inks wherever tolerance to alkali and soap is a major concern. Moreover, P.R.17 is also employed in connection with mass coloration and surface coloration of paper. 

The printing ink industry uses P.R.146 for letterpress and offset inks and also in packaging gravure and flexo printing inks. The pigment lends itself to a variety of special applications it is used, for instance, to print bank notes and securities. A certain tendency to migrate, however, precludes its use in print on plasticized PVC films. 

Good printability (eight color flexo printing) for superior presentation... 

The major use for UV flexo printing is a wide range of packaging products, including ... 

Most inks contain significant amounts of solvent for dissolving the resin and adjusting the ink viscosity. The kind of solvent used depends on the substrate and the end use of the print. Water as well as hydrocarbons are used, also ketones, esters and alcohols. For example ethanol and isopropanol are common in flexo printing. The solution of resin in a solvent is also called vehicle . 

Chabot B, Krishnagopalan GA, and Abubakr S. Effect of ultrafiltration permeate recycling on deinking efficiency of flexo-printed newspapers. Progr. Pap. Recycl. 1998 August 28-38. 

Properties M.w. 228.25 dens. 1.120 b.p. 120 C (1 mm) ref. index 1.4720 Toxicology Eye irritant TSCA listed Storage Refrigerate heat and light sensitive Uses Photosensitive acrylic resin for paint, flexo print resin crosslinking agent for free radical polymerization Manuf./Distrib. Aldrich http //www.sigma-... 

Flexo printing is similar to the traditional rubber-stamp techniques that have been in use for hundreds of years. The primary difference is that the flexible stamp (chche) in a flexo process is wrapped around a drum to be used in a continuous rotary process. In order to control the reinking of the cliche, an anilox roller, a metal or ceramic roller with small indentations (wells) of uniform size and shape, transfers ink firom a fountain to the cliche, as shown in Figure 4.6 through Figure 4.8. Diflferent rollers can be purchased to control the amount of ink that is transferred to the cliche. A doctor blade removes excess ink firom the anilox roller before it contacts the cliche. 

Acreo AB has demonstrated flexo printing of PEDOTrPSS films on photographic paper in a roll-to-roll process. The ink base, developed by AGFA-Gevaert, was mixed with other additives to increase the viscosity of the material (see the viscosity requirements for flexo printing in Section 4.4.1.2.1). 

FIGURE 4.6 Flexo-printing process schematic. Ink is transferred from a well to a flexible printing cliche by an anilox roller, and then from the cliche to the substrate. The choice of anilox roller material and well size and the position of the doctor blade, which removes excess ink from the anilox roller, determine how much ink is transferred. 

FIGURE 4.7 Flexo printing of organic electronic circuits as performed by PolylC. (Courtesy of PolylC GmbH Co. KG, Erlangen, Germany. With permission.)... 

The surface resistivity of PEDOT PSS patterned using flexo printing is rather high, ranging from a few to 10 kfl/n. However, new inks are continually developed, and improved performance is expected. PolylC is also developing a flexo production line for RFID tags based on organic field-effect transistors. 

FIGURE 4.8 Flexo printing at Acreo AB. A flexible printing template is attached to a printing drum (a), inserted into the printer and adjusted (b),... 

In flexo printing, ink must be picked up by an anilox roller, transferred to a cliche and then finally to the paper. Each step requires the ink to wet a new surface. Thus, the choice of materials, including solvent and possibly surfactants, is critical. As with other additives, surfactants can significantly decrease the electroactivity of the printed film if not chosen carefully and used in moderation. 

In the printing industry, relatively polar solvents such as ethyl acetate, alcohols, and water are most commonly used in flexo printing. These solvents are compatible with the soft rubber-like cliche. More aggressive solvents like acetone and chloroform may shorten the cliche s lifetime. 

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