The resin is filtered after leaving the barrel and screw area to ensure that a clean polymer is applied to the web. The filter also reduces infusibles such as fish eyes and gels in the polymer melt stream. The most common type of filtration in coating/composite extruders is a stack of screens or layers of the same or different mesh. Since the viscosity and pressure of the polymer are greater than the web stack can withstand, there is a breaker plate on the back for supporting the screen mounted on its upstream side. The breaker plate consists of a perforated plate that allows the polymer to flow through the breaker plate and maintains a good support. The breaker plate does not have much effect on the system pressure drop.
The screen is placed in the groove of the breaking plate to prevent it from moving upstream. The mesh of the screen used varies with the amount of filtration required. A typical mesh stack consists of two or three 40-120 mesh screens with the thickest mesh facing the direction of the broken plate to increase the pressure of the supporting colored holes and increase the effective opening area of the polymer melt.
In operation, the screen intercepts foreign objects, and the accumulation of impurities will block the circulation of the polymer to a certain extent. When such a situation occurs, the blockage increases the discharge pressure. When using a new screen, the pressure drop of the extruder can be 7000-14000 kPa, and then the pressure increases with time until it reaches a level of about 17500 to 35500 kPa, at which point the flow begins to decrease and the melting temperature increases to an undesired level. . The mesh stack should be replaced.
There are many types of mounting arrangements for the broken board. On older extruders, the breaker was installed between the two detachable flanges at the end of the extruder. It can be fixed with bolts, hinge bolts, "C', retainer, destructive locking device or other clamping method. The actual use of the broken plate is a metal-to-metal polymer sealing ring in the concave bore flange. The method of relying on clamping force to prevent polymer gap leakage, the type should be able to be quickly disassembled to minimize the time of changing the plate. The device in the hole requires removing the downstream socket and die for easy disassembly. The particle breaker is another option that allows the loaded material to enter the side of the housing at right angles to the polymer melt. This allows the downstream equipment to remain in place when the breaker is replaced. The inlet device is constructed as a bolted housing to allow the breaker plate to be inserted into the melt stream to seal the resin only when the extruded polymer is stopped. Due to the high precision components required to prevent low production conditions The leakage of the viscosity resin has also been tried, that is, the use of a slide or a plug device. Usually it is changed every four days or weeks from time to time to determine its operation must be simple, easy and cost-effective. Generally it can also be combined with other production lines. When there is a downtime Planned.
The breaker zone and equipment located downstream of the screw tip should be heated to maintain the metal temperature at the same temperature as the interior of the molten resin. It is also required to heat the downstream equipment to a different heating zone, instead of trying to balance the heating capacity.
The pressure sensing device is placed behind the mesh stack so that together with the sensor at the downstream end of the screw, the operating function checks for a drop in pressure and a rise in the press due to clogging of the mesh stack.
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