Winding Film factory: Introduction

Wrap film, also known as PE stretch film and heat shrink film, PVC film was produced earlier in China with PVC as the base material and DOA as the plasticizer and acting as self-adhesive. Due to environmental problems, high cost (absolute PE ratio is serious, the unit packaging area is small), poor tensile and other reasons, when the domestic production of PE stretch film began in 1994 ~ 1995, it was gradually eliminated. PE stretch film first used EVA as self-adhesive material, but it has high cost and taste. Later, PIB and VLDPE are used as self-adhesive materials. Now the base material is mainly LLDPE, including C4, C6, C8 and metallocene PE(MPE).

The late stretch film is mostly blown film, from single layer to two layer, three layer; At present, LLDPE stretch film is mainly produced by spreading method. This is because the production of casting line has the advantages of symmetrical thickness and high clarity, which can be applied to the requirements of high rate predrawing. Because single-layer casting can not do a single - sided adhesive, the use of the scope of the range. Single, double layer flow in the material selection is not as wide as the three-layer flow, the formula cost is high, so it is the same as the three-layer co-extrusion structure is more ambitious. High-quality film should have high clarity, high longitudinal elongation, high yield point, high transverse tear strength, good puncture function and so on.

Wrap mills: A way to reduce costs

Using it for product packaging, can effectively reduce the cost of use, the use of winding film is only about 15% of the original wooden box packaging, about 35% of the heat shrink film, carton packaging about 50%. At the same time can reduce the labor intensity of workers, improve the packaging efficiency and packaging grade.

It is divided into two kinds: mechanical film and artificial film. The stretching form of pallet mechanical packaging has direct stretching (also known as flat stretching or resistance stretching) and pre-stretching. Pre - drawing is divided into two kinds, one is roller pre - drawing, the other is electric drawing. Direct stretching is done between the tray and the membrane. The tensile ratio of this method is low (about 15%-20%). If the tensile ratio exceeds 55%-60%, the original yield point is exceeded, the membrane width will be reduced, the puncture performance will be lost, and the membrane will be easily broken. And at 60% tensile rate, the stress is too large, for light goods, it is likely to deform the goods.

Pre-drawing is done mechanically by two rollers. The two rollers pre-stretched by the roller are connected by the gear unit, the tensile ratio can be different according to the gear ratio, the tension is generated by the rotary table, because the stretch is generated in a short distance, the friction between the roller and the film is large, so the film width does not shrink, the original piercing performance of the film is also maintained. No stretching occurs during the actual winding, reducing breakage due to sharp edges or corners. This pre-stretching can increase the stretch multiplier to 100 to 150%.

The stretching mechanism of electric predrawing is the same as that of roller predrawing. The difference is that the two rollers are driven by electricity and the stretching has nothing to do with the rotation of the tray. Therefore, the adaptability is stronger, light, heavy, irregular goods are applicable, because the packaging tension is low, so this method of pre-stretching rate up to 200% ~ 300%, greatly saving materials and reducing costs.

Winding film factory: It can be seen that under the premise of ensuring the product's longitudinal elongation, puncture performance, transverse tear strength and other technical indicators, every 0.001mm thickness reduction of the film can increase the use of about 6% per kilogram of the same width.