Solventless lamination technology is an environmentally-friendly composite technology that has developed rapidly in recent years. It has the advantages of no solvent residues which has no pollution to the atmospheric environment, significantly reducing energy consumption, fast machine speed, etc. In the solvent-free lamination process, tension control is extremely important and must be very accurate. Tension control mainly includes the control for unwinding tension, film tension, auxiliary unwinding tension, winding tension, and winding taper.
The Application Of Tension Control In Solventless Lamination Machine
The tension of the solventless lamination machine is generally divided into four parts, including the first unwinding tension, the second unwinding tension, channel tension and winding tension. In the process of changing the roll diameter and production speed, solventless lamination has a requirement of constant tension. On the basis of ensuring the quality of the composite material, constant tension plays an extremely important role in improving the quality of the windings.
It is important to ensure that stable tension and winding integrity due to the frequent operations of starting and shutdown, acceleration and deceleration for solventless lamination equipment.
The floating roller has the function of absorbing kinetic energy. When the first unwinding tension is required to be constant, the second unwinding tension and the channel tension control adopt the low friction cylinder to control the swing rod tension control form to ensure the solvent-free. During the acceleration and deceleration, with the stable tension of the lamination machine, the membrane tension and relaxation caused by tension fluctuation are the smallest. If the first unwinding tension, the second rewinding tension and the channel tension are controlled by the bearing tension sensor, the first retraction unit harness, the second retraction unit harness, the coating harness, and the laminating harness are completely synchronized to ensure stability, acceleration and deceleration during the stretching process.
In addition, the flexibility of the guide roller rotation is an important factor in ensuring the stability of tension control during the acceleration and deceleration process. Under normal circumstances, the rotation of the guide roller is only synchronized with the moving movement of the film, so the ink on the film surface will not be scratched, which requires the static friction between the film surface and the guide rolls greater than the resistance of the roller. Therefore, the guide roller must be flexible with high assembly precision. The unwinding tension and channel tension of solventless laminator both have a requirement of constant tension. There are three winding methods, which include linear windings, hyperbolic windings, and parabolic windings.
The solvent-free adhesive is characterized by a solid content of 100%, low viscosity, low initial viscosity. If the composite intima is a stretched film such as PE film and CPP film, it is tried to use a hyperbolic winding method. When rolling up, the inner winding volume is relatively loose and the composite film is not wrinkled. The wrapped diameter is closely wound on the surface, with no bubbles on the surface.
Further, the winding pressure can also play a role of an auxiliary winding, and the air between the films is discharged, some of which have the effect of eliminating static electricity, which can increase the tightness and uniformity of the winding.
Key Points For Tension Control Of Solventless Lamination Machine
1. Generally speaking, the unwinding tension is based on the auxiliary unwinding tension. Increasing the main unwinding tension to match the auxiliary unwinding tension, making the composite film finally reach a flat straight state, the unwinding tension is the minimum tension without a wrinkle.
2. The tension of the film which is gluing, is slightly larger than the unwinding tension, which is used to tract the film, so that the corresponding coated steel roller does not require a large drive current.
3. The winding tension is slightly greater than the unwinding tension, the Initial viscosity of composite membrane which the winding tension needs to withstand, is only about 0.2 N / 15mm, and the winding taper is controlled within 20%, with the increase of coil diameter, the decreasing degree of tension is slower than dry lamination.
4. For the films of different materials, the tension in each part is different in the lamination process. Even the film has the same material and the tension is also very different depending on the different composite structures. For example, in the PET / PE structure, because PE is easy to stretch, its tension is substantially from 3N to 5 N. PET is contended with the shrinkage stress of P and its tension is relatively large, substantially 20N. But in the composite structure of PET/paper, since the stretchability of the paper is better, PET only requires the minimum tension, typically 5N.
Methods For Checking Whether The Tension Control Is Appropriate For Solventless Lamination Machine
Shut down the solventless machine, making a cut on the composite film with a blade at the winding position and the most ideal state is that the composite film remains flat. If the composite film is curled in a direction, which indicates the tension of the film is too large, the tension of the film should be appropriately reduced or increasing the tension of the film in another layer.
During solventless lamination, the requirements for tension control are higher than that of ordinary compounds. The solvent-free lamination machine tension control has high requirements, making the elongation of the two-layer material rolls as consistent as possible through accurate tension control to ensure that the two-layer coils don’t produce relative slip during the solventless laminating process. Accurate tension control is the premise of ensuring the quality of composite films.
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Sinstar Packaging Machinery Co., Ltd is a professional supplier who’s engaged in the research, development, production, sales and service of non solvent laminating machines with annual production capacity of 200 sets.