Roll cling

The thinner the sheet the greater the degree of roll cling, Thus the speed of the stripper roll must be varied with respect to the calender speed. Once the desired speed differential is set it is maintained. As the calender speed is altered, the stripper roll speed maintains a constant ratio with the calender speed. 

We use the casting process to make polymer films (less than 0.3 mm thick) and sheets (more than 0.3 mm thick) for such diverse end uses as cling wrap, merchandise bags, roofing membranes, landfill liners, and the interior walls of refrigerators. During chill roll casting, molten polymer is extruded as a curtain from a slot die onto a chilled metal roller where it solidifies. The product is transported over a series of rollers to a winder where it is wound up. 

Conversely, cling film (plasticised PVC/PVDC, (poly(vinyl chloride)/poly (vinylidene chloride), copolymer, which has very high gas-barrier properties) on peeling from a roll generates static electricity thus promoting adhesion to a surface, e.g., ceramics, but not metallic surfaces which conduct the static electricity away... 

Since the heated plastic clings to the calender rolls the web does not drop off the last roll. It has to be pulled off evenly across the width of the roll. This is accomplished by the stripper roll which is normally positioned 3 to 6 in. (75 to 150 mm) from the last roll, and at a height that gives the sheet approximately 270° lap round the roll. 

The choice of a mill may depend on the desired characteristics of the liquid color needed. If a heavy viscosity is acceptable, the three-roll mill is an excellent tool. The premixed liquid color is introduced at the first nip. After passing through that nip, about half the liquid clings to the second roll and is carried around to the second nip. About half that liquid clings to the third roll and is scraped off and collected by a doctor blade (also called the apron). That is the finished liquid. Since the liquid is split twice, about three-quarters of the liquid that passes through the first nip is returned to be reprocessed at the first nip. 

The type of roll surfaces has a marked effect on the overall production throughput of a roller compaction process (Fig, lO). A variety of roll surfaces and configurations are available depending on the compaction behavior of the material. For instance, powders that tend to stick or cling to the roll surface requires the use of smooth or circumferential grooved surfaces, while materials that release cleanly from the roil after compaction may be pressed with one of the pocketed design or rolls with grooves in the axial direction. 

Use In lubricating-oil additives for ashless dispersant processing, rolling, and compressor oils caulks, sealants, adhesives as an elastomeric process aid and cling improver in cling films. 

Table rolls contribute a gentle suction in the downstream expansion zone between wire and roll, while some of the water pulled through clings as a film on the underside of the fabric to be pushed up through the wire on the upstream side of the next roll this vertical pressure pulse helps consolidate the web. Where wire speeds exceed about 25 m s the suction increases excessively and rolls are no longer used. 

The reflectivity of a stack of transparent thin films that are not carefully engineered in terms of thickness or refractive index will give a reflection that appears to be metallic silver. This can be seen in a less-than-perfect fashion with a stack of microscope slides or a roll of thin transparent plastic film, such as cling film . 

In order to mix efficiently, the compound must band (see Fig. 1(a)), but not stick, that is it must cling to one of the rolls. The roll to which the compoimd bands can be influenced by the friction ratio and the roll temperatures. Mixing is difficult if the material bags (see Fig. 1(b)). 

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