Blown Film Extruder Reduces Scrap by 80% Using Dyna-Purge^® Engineered Purging Compounds.

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Situation:

Plásticos Hidrosolubles, Rafelbunol, Valencia, Spain produces water-soluble plastic film and converts it into bags to package a wide range of products, including hospital laundry bags, prepackaged automatic washing machine detergents, agricultural fertilizers and chemicals, and industrial chemicals (e.g. colorants, pigments, dies and stiffeners).

Operating a blown film extruder with a 60mm screw, the company makes three core products, processing PVOH at about 200°C (392°F). Although the film products are biodegradable and non-toxic, designed to dissolve in water at temperatures ranging from 5°C to 50°C (41°F to 122°F), the resins are solid in raw material form. Purging, which is necessary at least once every week, was difficult and time-consuming.

Using 5-to-6 kgs (11-to-13 lbs.) of standard polyethylene to purge, it would take Plásticos Hidrosolubles at least three-to-four hours to change materials or colors. This would waste a significant amount of material until an acceptable level of quality was achieved.

Solution:

Upon consultation with David Navarro of Comercial Química Massó, Plásticos Hidrosolubles tested Dyna-Purge F, a specialized thermoplastic purging compound designed to purge single-layer film from extrusion equipment at processing temperatures from 160°C to 215°C (320°F to 420°F). Comercial Química Massó (www.cqm.es) is the authorized distributor of Dyna-Purge in Spain.

Results:

• Using Dyna-Purge instead of polyethylene, purging is faster and more effective. The screw is cleaner.
• Downtime for purging has been reduced by approximately 50%.
• There is 80% less scrap when purging with Dyna-Purge, saving valuable resin and improving operating efficiency.