Shrinkage packaging technology
Shrink packaging is a packaging method that uses shrink film to wrap the packaging material, and then heats the film to shrink and tightly wrap the product.
Shrink packaging has good protective performance, transparent luster, low processing cost, light weight, suitable for small products, large products, pallet packaging, and mechanized production.
Material selection
Shrinkable film is a commonly used type of packaging material. According to the characteristic that thermoplastic will recover under heating conditions, during the process of making a film from plastic raw materials, it is heated and stretched in advance, and then cooled to produce a shrink film. The manufacturing methods include the secondary stretching method of making sheet-like films and then stretching them separately along the longitudinal and transverse directions, and the primary stretching method of simultaneously stretching them in both directions. There are also methods of first making cylindrical films for secondary stretching or primary stretching.
The most commonly used shrink film materials currently are polyvinyl chloride, polyethylene, and polypropylene, followed by vinylidene chloride, polyester, polystyrene, chlorinated rubber film, and nylon resin. When selecting, the main considerations are the shrinkage rate, shrinkage ratio, shrinkage tension, shrinkage temperature, and heat sealing properties of the material.
Currently, PVC, POF, PP, and PE are commonly used for shrink packaging in the market. PVC and POF are used for shrink packaging of smaller and lighter products, while PP and PE are used for shrink packaging of larger and heavier products
Selection of shrink packaging method for Ayi shrink machine
The shrink packaging process is generally carried out in two steps. Firstly, pre packaging involves wrapping the product with shrink wrap and heat sealing the necessary openings and seams; Then there is thermal shrinkage, where the pre packaged product is heated in a thermal shrinkage device.
a. Pre packaging operation. When pre packaging, the film size should be 10% -20% larger than the equipment size. If the size is too small, it will be inconvenient to fill the items, and if the shrinkage tension is too high, it may break the film; If the size is too large, the shrinkage tension will be insufficient, and the packaging may not be tight or even. The thickness of the shrink film used can be determined based on the size, weight, and required shrink tension of the equipment;
b. Heat shrink operation. The equipment used for thermal contraction is called a thermal contraction channel (also known as a thermal contraction tunnel), which consists of a conveyor belt and a force free hot chamber. The thermal shrinkage process involves placing pre packaged items on a conveyor belt that runs at a specified speed, feeding them into a heating chamber, and using hot air to blow onto the packaged items for heating; After completing the thermal shrinkage, leave the heating chamber and cool naturally before removing from the conveyor belt. Common production process for shrink packaging: shrink film is processed into pockets (if the machine is semi-automatic or fully automatic, it does not need to be processed into pockets, and the machine can directly complete the bag making process) → bagging → sealing (specific requirements, some products do not require sealing) → put into a heat shrink machine for heating → shrink → cool → finished product is completed.