Transfer rolls

Transfer-roll chemical finishing, 17 513 Transformation herbicide, 13 309 of plant species, 12 485 plasmid, 12 501... 

Unit sizes are similar to those available for drum dryers listed in Table 6.8. The dip feed arrangement of Fig. 6.5 is common but transfer roll, top (nip) feed and other feed mechanisms are also in use. Production capacity and characteristics of the finished product vary from product to product and have a complex relationship (Table 6.9). 

Methods which enploy liquid phase treating liquors (spray, transfer rolls and belts, etc.) share a cannon difficulty stemming from the lew volume of liquor in relation to the large surface area of the fibers conprising the substrate to be treated. This difficulty is acerbated when aqueous liquors are to be applied to hydrophilic fibers. Foam coating methods enploy stable foams which allow the thickness of the liquid-air mixture to be controlled by a doctor blade or roll. Conparatively low add-ons can be achieved by virtue of the low density of the foam layer, but the stable nature of such foam, and its immobile liquid phase, inhibit rapid, uniform distribution through the substrate. 

There are two main types of low wet picknp applicators. The first is the saturation-removal type where the fabric is completely satnrated with the finish liquid and then the excess liqnid is removed mechanically or with a vacnnm before drying. With the second type, a precise amount of finish liqnid is nniformly applied to the fabric using transfer roll, spray or foam techniqnes. Table 2.2 gives a snrvey on low wet pickup finishing application methods, some of which will now be discussed in more detail. 

In the area of topical application, several methods have been used to apply chemical finishes using transfer rolls. The kiss roll. Fig. 2.4, picks up the chemical finish and transfers it by direct contact to the fabric. The amount of finish picked up is dependent upon how well the finish wets the roll, the absorbency of the fabric, and to a lesser extent, the surface speed of the roll relative to the fabric speed. 

Another version of finish apphcation with transfer rolls is the loop transfer system, Fig. 2.5.A loop of fabric is immersed in finish liquid and then squeezed with the fabric to be treated between squeeze rollers. The finish is transferred to the fabric at a much lower wet pickup than possible by direct immersion. These roll transfer techniques are especially useful for the backside application of finishes, for example hand builders and flame retardants, to pile fabrics (without crushing the pile). 

The ink transfer rolls apply a uniform film of ink to the printing plate or roll tills ink film is transferred directly to the paper substrate, or first to the printii blanket and then to the paper substrate. During printing, the ink film penetrates into the porous paper substrate, and that part of the ink film remaining between the substrate and the plate splits, leaving part of the film on the substrate and part on tiie plate. This ink film splitting is described the Walker-Fetsko equation 0 ... 

Transfer application employs a compliant gap to apply most of an arriving pre-metered layer to substrate passing through the gap. The compliant element can be either a soft transfer roll (often called an applicator roll), a soft backing roll, or the web tensioned over a transfer roll. 

Letterpress printing The process used for paper is adapted to plastics by the use of special inks and transfer rolls, and possibly a modification of press speed. Flexible printing plates are usually employed, made of vinyl or rubber. It is the oldest method of printing flat plastic substrates and uses a press for rehef printing ffom metal type or raised surfaces formed ffom wood, metal, or linoleum. Leach RH, Pierce RJ, Hickman EP, Mackenzie MJ, Smith HG (eds) (1993) Printing ink manual, 5th edn. Blueprint, New York. 

Transfer roll n. In the coil coating industry, the roll between the pick-up roll and applicator roll where three rolls are present in a coating operation. 

Simultaneous coatings can also be made with one flexible blade against the web on the roll, where the web moves downward. On one side the coating fluid is supplied to a puddle in front of the blade, and on the other side the fluid is carried into the nip by the roll. Edge dams between the web and the blade and between the web and the roll keep the fluid contained. The roll may rotate faster than the web. Figure 6 shows a version where the fluid on the roll side is supplied by a transfer roll. 

Inan and co-workers study of the flammability of PA6-clay nanocomposites provides an elegant illustration of the dominant heat transfer roll that the char plays in controlling nanocomposite flammability.In these experiments PA6 nanocomposite samples were placed atop pure PA6 samples, these compression-molded composite samples were burned in a cone calorimeter, and the reduction in peak heat release rate for the composite sample was found to be 11% of that expected if the entire sample had been nanocomposite. Since only half of the composite contained clay, this magnitude of effect is surprising. Furthermore,... 

---