Provided with guide-roll, continuous water changing, cutting unit, rotating cylindric blade, 7.5 kW engine
RPP tank, 3 m³ provided with supply unit
Process Description
Bidirectional two-phase elongation of flat film
PP granulates get melted, homogenized and formed into a sheet through a broad-gap die
The sheet is transmitted between water-chilled chromate cylinders
In the longitudinal expansion section the film is preheated to the expansion temperature, then expanded in one or two phases with a relatively high expansion speed
The two edges of the film are fixed by an endless series of clips, and the film is introduced into the transversal expansion section
After expansion follow the phases of temperature stabilization, edge trimming, surface treatment winding
The expansion temperature influences the strength and optical properties of the film
The product has longitudinal and transversal mechanic properties that differ; the effect of the transversal expansion is dominant
Theoretically it is possible to expand the film first in transversal and after that in longitudinal direction
Extrusion Line General Features
The basic units are: the extruders, the moulding device, the MDO, the TDO and the winder
The mixture necessary for the production of plain films is melted by the main extruder at 220-260 °C
The temperature is in function of the revolution of the screw, the thickness of the film, and the properties of the raw material
Between the normal transporting limbs of the screw there is installed another blocking limb that regulates the homologous state of the melt, the fluctuations of the temperature and the pressure
The temperature of the extrusion zone is adjusted by a heating-chilling system
The melt passes through the filter and the breaking roll to equilibrate the flux, create counter-pressure, and eliminate external, unmelted or burned parts
The melt then gets to the static mixer that eliminates the radius directed temperature gradient
From the mixer the melt gets to the broad-gap die
For coextrusion-type films, the melt of copolymers necessary to the sealable superficial layers is produced by two coextruders
The scope of the moulding unit is to chill the melt and form a sheet; the melt leaving the broad-gap die passes a gap of air of a few centimetres, after which it is pressed to the surface
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