Two-layer Tubular-quenched Pp Line Claims World-beating Output

Cast and biaxially-oriented polypropylene extrusion lines are prohibitively expensive for many Indian converters, whose captive processing requirements are usually much lower than their typical 700- to 800-kg/h outputs. Low-cost tubular-quenched PP lines are popular in India, but their low outputs can be restrictive, too. But at the Plastindia exhibition in February, Rajoo Engineers Ltd., Rajkot, India, unveiled a 2-layer tqpp line with a 175-kg/h capacity, double that of most existing lines.

The line has a 60-mm, 30 l/d grooved feed extruder, and a 40-mm, 26 l/d extruder. A 300-mm oscillating die with specially-designed spiral channels achieves close thickness tolerances, and a static filter enables prolonged runs without filter changes. Other equipment include a 4-station center winder, an auto tension-control system, side and center slitters, bow rollers, and pneumatic winding shafts.

The line can extrude film as thin as 20 µm with +/-4% tolerance, which Rajoo says is sufficient to enable printing and metalizing. "We've achieved enhanced tolerance through improved screw design, which enables high output at low temperature with less thermal degradation, employing a large filter area for homogenizing, and design improvements in the die spirals," says director Sunil Jain.

The line sells for $150,000. Layflat width is from 430 to 1050 mm, line speed is from 10 to 60 m/min, and maximum film thickness is 100 µm. Inline slitting allows winding of up to four rolls.

Indian processor Alpha Plastomers, which already runs 25 Rajoo monolayer lines with 140-kg/h output, will accept the first line. "With the core layer of homopolymer, the other layer could be of 'designer resins' or a random copolymer for achieving the appropriate property mix," says Jain. Transparency and gloss are said to be on par with cpp and bopp.

Rajoo will develop a 3-layer line, which will yield films with high-slip layers for faster converting on bag-making mach-ines, and non-slip layers for metalizing.