1 x 60
1 x 90
|L:D ratio screw(s)||
1 x 30D
1 x 33D
|Max. web width||1780 mm|
|Type of winding||Double for flat film|
|Tower construction included||Yes|
|Machine can be seen in production||Yes|
Machine used the double bubble extrusion process. In the double bubble process, the polymer is extruded as a tube into a water bath. The water rapidly quenches the polymer, reducing its crystallinity compared to conventional air quench blown film. The lower level of crystallinity helps in the subsequent orientation process.
Following quenching the tube is reheated to the orientation temperature using a hot water bath or IR heater. This two-step process of quenching and reheating the tube helps control the crystallinity as well as produces a more uniform temperature for orientation. The tube is expanded by blowing air inside the tube similar to a conventional blown film process. A difference is that in the double bubble process the tube is oriented at lower temperatures, producing higher stresses during orientation. Stretch ratios are also typically much higher than in conventional blown film. As a result, double bubble films have more orientation than conventional blown films. Melt strength is also not a factor as it is in the blown film process.