Battenfeld Gloucester: Largest blown-film line

A blown film line built by Battenfeld Gloucester for a Latin American company is claimed as one of the biggest in the world. The line, for three-layer coextruded MD/LLDPE geomembranes, has a 2•2 m die and a 25 m tower. It produces 7 m wide film from 500 - 2,500 microns gauge at more than 1,200 kg/hour.
The die, one of the largest ever built by Battenfeld Gloucester, was designed specifically for geomembranes with particular concern to eliminate dead spots and prevent overheating to avoid negatively affecting the properties of the LLDPE - specified to increase the elasticity of the web.
The three extruders in the line are Battenfeld’s Contracool air-cooled units. The B extruder, used for the core of the web, has a 203 mm diameter 36:1 L/D screw, and the A and C extruders for the inner and outer skins have 89 mm screws, also 36 D. Use of such relatively long screws increases the mixing efficiency and homogeneity of the melt and reduces process heat.
Both skins of the web need texturing for greater traction when they are installed, so Battenfeld Gloucester added a system to pump nitrogen into the A and C extruders. When the nitrogen exits the die in the outer and inner layers, it disrupts the melt flow and creates a controlled texturing of the skins. The line can also produce film with non-textured, smooth edges which aids the welding of the geomembranes to each other.
Other special components include the unfolder, secondary nip and winder. The Model 196C winder is designed for geomembranes with a 7•31 m wide spindle. It can be programmed to operate at speeds of 1 to 10 m/min. The largest roll that can be wound is 900 mm, although the company generally winds rolls 400 to 500 mm in diameter.

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