Water quenched film line

Figure 5.9 Simplified water quenched film line...

Figure 8.9 Typical water quench film line.

Copolymer film is produced by extmsion blowing foUowed by water quenching. In-line, the film is blown, crystallized, and oriented. PVDC copolymer film is difficult to produce. 

Fig. 38. DSC scans of the isothermal crystallization, at 104 C, of ultraquenched (solid line) and ice water quenched (dotted line) PET films. 

Flat film identifies cast film. Other names used include chill roll film, roll cast film, slot cast film, water quench, water chill film, etc. These cast film lines require dies that yield a wide range of diverse products. Widths may range from less than 6 in. (15 cm) to more than 33 ft... 

Cast film is produced by extruding the melt from a slit die and cooling it either by contact with a chill roll or by quenching in a water bath. The most popular process used to produce the flat film is with the chill rolls. Chill roll lines can be arranged in different layouts to meet different requirements. Example is shown in Figure 5.7. Water chill tank or quench film is also a popular process. 

The rapid-water-quenching system produces good optical properties, has low equipment cost, but can be difficult to use to get precise control over the water temperature. Vibrations and currents can cause little marks on the film. A critical point is the necessity for maintaining a smooth surface in the water quench tank where the melt first enters. Different devices are used to control the flow of water such as baffles with openings. It has serious limitations when high production speeds are attempted the water must be kept from carrying over into any on-line pretreatment and the finished roll. However, these problems can be controlled. This liquid bath system has been used for blown tubular film inside the blown film to improve... 

Isotactic polypropylene (iPP), when quenched from the melt in cold water, gives rise to a metastable, solid mesophase, which transforms into the stable a form by annealing at elevated temperatures [25-27]. The X-ray powder diffraction pattern of this disordered form of iPP presents only broad halos at 20 = 14.8 and 21° (Fig. 33A). Oriented fibers of iPP in this mesomorphic form can be obtained by stretching the corresponding unoriented films [25]. The X-ray fiber diffraction patterns present broad peaks on well-defined layer lines as shown in Fig. 33B the chain periodicity corresponds to 6.5 A, as in the crystalline a form. 

A quench system is used downstream of the incinerator furnace to cool hot furnace gases to adiabatic saturation temperature, about 185°F (85" C). A quench system includes a refractory-lined carbon steel chamber with a watertight rubber film between the refractory and the carbon steel. Where acids are generated in the furnace, the refractory is acid resistant. Either water or air can be used as the... 

Simultaneous Biaxial Orientation. There are two predominate systems available to do this, tubular and flat film. In the tubular process (see Fig. 9), also referred to as the double bubble process, a continuous tube is extruded and quenched. Typically, an interior cooled mandrel is hung from the die inside the tube. The surface of the mandrel may greatly influence the interior surface of the tube. Care must be taken not to impart scratch lines in the melt as it is pulled down over the mandrel. Air pressure in this primary tube is very critical. The melt needs to be held out over the mandrel but not too far away. A water bath on the external side of the tube helps quench the tube rapidly. A nip pulls the tube from the die and acts to isolate the casting bubble from the air pressime in the stretching bubble (27). 

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