More flexible multi-layer barrier film production line

Due to the rapid development of multi-layered barrier films in recent years, the number of new film types is increasing. Some processors even produce hundreds of different film products within one year. In order to meet the requirements of fast delivery, they must shorten the production cycle as much as possible, thus placing higher requirements on the flexibility of the multilayer barrier film production line. In this regard, the German company KIEFEL proposed their solution.

The ever-changing market for multi-layer barrier films requires that equipment purchased by thin film manufacturers be able to produce a wide range of products to meet rapidly changing market requirements. To this end, the German company Kaifair has a modular design of its blown film production line, and at the same time has improved the function of the relevant automation control system, so that its equipment has a high degree of flexibility and the ability to optimize the combination. This line enables film manufacturers to easily and cost-effectively upgrade and retrofit their equipment when changing products.

Extruder

In the blown film production line, the main task of the extruder is to process all kinds of different raw material granules into a uniform melt. Of course, it must also ensure that the raw materials can be exchanged without any obstacles, and the raw materials do not need to be replaced when they are switched. Screw or take a long cleaning time.

There are two types of extruders available from Kiefer. One is a grooved feed extruder and the other is a smooth feed extruder. Smooth extruders are more suitable for barrier film production. This is because the feed section of the smooth extruder can evenly process various critical raw materials needed for production of barrier films, such as EVOH, PA6, PET or COC, etc. at a relatively low shear rate. To ensure perfect melt quality, the company's two extruders also use a specially designed mixing section with minimal shear. This mixing section ensures the controllability of the melt temperature and the stability of the bubble. In addition, in order to save space and reduce maintenance costs, they use gearbox direct drive technology that does not require a drive belt, which makes the extruder more stable and quiet during operation.

Film blowing machine die

In the processing of multi-layer co-extrusion blown film, a pre-distributor can be used to evenly distribute the melt from each extruder into a multi-layer annular flow channel. The dual-stack pre-distributor of the company can guarantee lower pressure drop, good self-cleaning ability, small temperature difference between the layers of the melt, and the time difference between their stay in their respective flow channels. Low die height makes it easier to operate.

The thickness of each layer of the multilayer co-extruded barrier film and the accuracy of its distribution are determined by the design of the pre-distributor, the spiral core, and its processing accuracy, and the machining accuracy of the internal gap of the die at the junction of the layers is particularly important. The Coriolis-designed spiral core used by the company is able to accurately guarantee the structure and thickness distribution of each layer. At the same time, the optimized design of the pre-distributor also ensures that the multilayer melt has a short confluent path, which can significantly reduce the adverse effects of the very high temperature nylon (PA) layer on other temperature-sensitive material layers.

Wind Ring

The air ring plays a decisive role in many aspects such as the quality of the blown film and the economics of the total production process, because it not only affects the transparency of the film, but also affects the stability of the bubble and the production of the production line. Keefer uses a double-lip air ring, which blows air from both the upper and lower sides. The air blown from the gap below avoids contact between the film and the first cooling lip, while also ensuring the stability of the bubble. The air blown from the upper gap is used for bubble cooling to ensure the stability of the bubble and ensure that it does not come into contact with the second cooling lip. With this double-lip air ring design, bubble movement can be avoided, cooling can be made more efficient, subsequent processing can be easier and the yield can be higher.

Traction device

Since the barrier film is generally hard, when the film bubble is converted into a double-layer flat film through the quenching process, the requirements for the traction and quenching device are relatively high. In general, the longer the extinction rack, the less wrinkles the film has. In addition, the accuracy of the temperature control is also an important factor, and the control of the temperature depends to a large extent on the material of the quenching frame.

Kaifair has improved the design of its traction devices. In this design, the primary nip roller and the reversing roller are located on a rotating platform that is used to support the heaviest portion of the traction device, which ensures the stability of the traction device. In addition, the advantages of the new design are also reflected in the following aspects: Zero-contact (ZERO TOUCH) air reversing roller system. Its patented profiled air cushion prevents direct contact of the film with the air reversal roll, plus a "hardslide" Teflon coating that completely eliminates scratches on the film film surface, which is also the entire drag The biggest feature of the system; it can achieve 6.5o on the extinction rack with a longer extinction length. The minimum flattening angle, thus significantly improving the flatness of the film; using a linear servo motor to control the angle and position of the quench bubble rack, its parameter settings can be saved in the KIRION control system, so that the product can be directly called when the product is replaced, thus eliminating the need for Make repeated adjustments.

As processing costs continue to rise, raw material hardness continues to increase, and film quality requirements are increasingly stringent, equipment is required to produce smooth, wrinkle-free, scratch-free films, which undoubtedly puts new pressure on flattening devices. The challenge. For this purpose, Kiefer has specially designed a brush roller with diagonal nylon bristles.

This brush roller design has more advantages than traditional flattening devices. Because the uniformity of the overall cooling of the film is critical to excellent film flatness, Kiefer uses a unique nylon brush roller. Although the bristles of the nylon brush are very thin and the contact area with the film is small, the side area that can be used for heat dissipation is large, so that it can be used to ensure uniform cooling of the film during the entire production process. However, the old-fashioned aluminum roller or carbon fiber roller will cause its own temperature to rise due to the accumulation of heat, which will adversely affect the cooling and thickness of the film.

This nylon brush roller also plays an important role in the flattening of the film. When using a conventional flattening device, it is difficult to control the flattening speed of the film at the same width to be exactly the same, often resulting in wrinkling or scratching of the film. The soft bristles on the nylon brush roller can equalize the relative speed during its movement, thereby avoiding the damage to the film quality caused by the different flattening speeds. In addition, since the contact area with the film is small, it is also possible to prevent the material from sticking to the roller during flattening. Therefore, it can be said that in many fields of application of the film, this specially designed nylon brush roller provides protection for the film with perfect flatness and transparent properties.

This new type of traction system from the company has a compact design, which makes it possible to increase stability while not requiring additional space. KIRION control system can also set a smaller rotation angle to reduce foaming, very conducive to the production of high flatness film products. Furthermore, the zero position and rotation range of the rotating device can also be arbitrarily selected, and parameters can be stored in the control system.

Winder

In order to obtain a wrinkle-free, flat, and precise width of the film roll in order to facilitate more efficient and economical processing, Kaifir and its subsidiary WINTECH have optimized the design of its film winding equipment. In the KIRION-M winder, the entire winding path is divided into a small independent sub path, that is, the thin film that needs to be wound into each sub path. Due to the fact that the thin film measurement and control system is installed from the secondary nip above the winder, the film at each station undergoes flattening and once again monitoring and control, eliminating the irregular movement of the film in the forward path. So that the film tube can be cut exactly after it is flattened. It is particularly important to maintain stability without drift during slitting the film because drift can cause irregularities on the side of the film roll or inconsistent widths during slitting, which can affect overall product quality.

After slitting, the sub-volumes will be re-flattened, thanks to Wintek's independent drive design. The advantage of using such separately adjustable flattening rolls to give each roll a slight speed difference is that it does not cause stretch deformation of the film, thus ensuring continuous unwinding of the roll. In the subsequent winding station there is also a measurement and control system, through which all external influences can be eliminated, ie only when there is no deviation in the path of the film, it will be allowed to leave the measurement and control system and be received by the carbon fiber roller and then pass through. The integrated vacuum adsorption system transmits to the winding point for perfect drift-free winding. This is more important for films with shrinkage.

At the same winding point, the winder also offers a range of different winding methods:
● Surface winding with constant contact pressure (CLP) function;
● Surfaces with or without constant contact pressure and center rewind;
● clearance winding;
●DCD (dual center drive) center and clearance winding;
The winder can not only take up all the resin-made films by the above-mentioned function, but also adjust the hardness of the film roll according to different material combinations.

Automation Control System

The automatic control system is a necessary means to effectively monitor the production and processing of complex blown film. Kiefer installed a multilingual central control system including Chinese in its blown film production line. The system exchanges data through a distortion-free bus system and has a touch screen with a standard window interface. Depending on the raw material of the film, the automation system can be adjusted and controlled by changing the settings of the die temperature, the air ring temperature, and the air volume of the air ring.

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