# Control of Physical Processes in an Extrusion Line Polymer Sleeves Production
## 2 Materials and Methods
### Working Principle of the Extrusion Line to Produce a Polypropylene Film  
The operation of the extrusion line (Labtech Engineering Company Ltd. (Samut Prakan, Thailand), LF-600/LCP models) for the production of polyethylene sleeves, installed under the conditions of \"Holding AltynArna\" LLP (Karaganda City, Kazakhstan) is considered. Figure 7 shows the technological diagram of the extrusion line. The principle of operation is as follows. The dried granules are fed by pneumatic transport into hopper 7 of the extruder. Under the action of gravity, the granules move downward and fill the interturn space of the screw in zone I. The rotating screw moves the polymer along the barrel into extruder 2, which forms the annular angle head 3. The rotating screw moves the polymer along with the barrel in zones II-III and into the annular head. In the head, the melt is cut by a mandrel and, upon leaving, has the shape of a barrel. To give it dimensional stability, the extrudate is cooled from the outside by air coming from the slot of the hollow ring 4. The moment of solidification of the melt (for crystallizing polymer is crystallization) is fixed by the appearance of a characteristic cloud point of the sleeve, the so-called crystallization line 5. Up to this line, the extruded sleeve is stretched along its length by the pulling rolls 7 and blown out by the air inside the sleeve along the diameter. To start inflating the sleeve, there is a special air channel 12 in the head mandrel, which is connected to the blower. Air is fed into the sleeve periodically as it diffuses through the film and leaks through leaks in the film layers between the pinch rolls. Stretched in two or in one direction, the film after the crystallization line continues to be cooled by ambient air, and then gradually folds folding cheeks, diverging at a certain angle 6. The movement of the film and its drawing is carried out by a rubberized pair of rolls tightly pressed to film 7. Then, the sleeve is in folded view and can either be cut on the sides with knives 9 and wound into two bobbins 10 in a single layer or not cut and wound  
Figure 7: Technological diagram of an extrusion line for producing polypropylene film for sleeves: 1—bunker; 2—extruder; 3—annular angular head; 4—hollow ring for air cooling of the film sleeve; 5—crystallization line with height H; 6—folding cheeks; 7—pressure pulling rolls; 8—film; 9—knives for trimming edges; 10—winding device; 11—edges cut from the film; 12—branch pipe for supplying compressed air for inflation of the sleeve. in a double layer on one bobbin. The two cut edges 11 are processed in a granulator and prepared to the primary polymer material. Figure 8 shows that the most critical technological unit in the extrusion unit is the angular angle head. In the production of sleeves films at AltynArna Holding LLP, extrusion plants are used to eliminate the pulsation of the melt, with the ratio L/D = 20-25, with D from 20 to 90 mm. The films are obtained after stretching and blowing, with a thickness of 10 to 300 \(\upmu\)m and thickness variation of \(\pm\)10%. The temperature of the forming tool usually only affects the surface quality of the film, as the material is in the forming die for a relatively short period of time. It is observed that a noticeable change in extruder performance is observed only when the change in heating power occurs in the loading zone. With changes in heating power in areas close to the end of the screw, the productivity changes within the accuracy of the measurement, i.e., controlling the temperature of the polymer melt in areas near the end of the extruder screw has no effect on the performance [26]. Furthermore, it is noted that, in the stationary mode of operation of the extruder, a linear dependence of the change in the temperature of the polymer melt \(\Delta\)Tp on the change in the heating power \(\Delta\)Pi, supplied to the i-zone of the extruder barrel, is observed.