Technical problems of the hottest multi-layer coex

Technical problems of multi-layer coextrusion film blowing equipment

A) the characteristics of raw materials should be considered in the design of the extrusion system of multi-layer coextrusion film blowing equipment

the design of the extrusion system (screw, head) of the multi-layer coextrusion film blowing equipment should first consider the density, melt index, viscosity, fluidity, processing temperature, thermal sensitivity and other characteristics of raw materials, as well as the blending and composite properties of different raw materials

b) configuration of extruder and head of multi-layer coextrusion film blowing equipment

automatically complete the multi-layer coextrusion film blowing equipment. Each flow channel of the head can be configured with an extruder separately, or the flow channels of some head layers can share an extruder. For example, the five layer coextrusion system can be configured with 5 or 4 or 3 extruders. The former can extrude a different raw material in each layer of runner, and the formula of raw material changes flexibly, which is conducive to the combination of film functionalization. At the same time, it can easily adjust the thickness of film between layers and save valuable raw materials, but there are many extruders and the equipment cost is high; Although the latter can be equipped with less extruders, and the equipment cost is low, it can only be used in the production of film products with little structural change. Although the equipment is cheap, it is difficult to save the use of valuable raw materials. There are few configurations of this equipment

c) main categories and applications of screws

the screw mainly has the forms of barrier, separation, pin, wavy and so on. The structure of the screw is different between crystalline and non crystalline plastics, heat sensitive and non heat sensitive plastics. The design of screw length diameter ratio, screw groove depth, compression ratio, the length of each functional section, and the positioning of solid-liquid phase groove directly affects the plasticization, performance, output and energy consumption of the film. In fact, raw materials with different characteristics should be processed by screws with the same structure that are not due to political tensions, central bank interest rate hikes and western economic recovery of disunity 1, so as to obtain the best processing effect. Barrier, separation, pin screw can be used for polyolefin processing, separation screw can be used for PP processing, and wavy screw can be used for PA and EVOH processing. However, many factories need to change the processing raw materials frequently, and it is troublesome to change the screws frequently for the processing of different raw materials. They can only design "compatible" screws to adapt to the processing of several different plastics (the ethylene production unit of China Secco Petrochemical Co., Ltd. has stopped the shutdown inspection on March 10, such as the screws that are suitable for the processing of llpde, LDPE, HDPE, EVA and the screws that are suitable for the processing of PE, PA, EVOH, PP), Although the "compatible" screw can not get the best processing effect of some raw materials, it can also meet certain processing requirements