Multi-layer blow molding is a blow molding technology developed to meet the special requirements of certain industries, such as medicine, food and cosmetics, for packaging containers, such as air tightness, corrosion resistance, etc. The basic process principles and single-layer product blow molding technology Similarly, there are two main types: co-extrusion blow molding and injection (injection) blow molding. In the co-extrusion method, multiple extruded sails are used, and different resins are extruded into the multi-layer die at the same time to form a multi-layer concentric product parison, which is then blow-molded. When using injection blow molding. After injecting one layer on the male mold, the cavity is changed to inject the second layer on the first layer, and the operation is repeated to form a multi-layer product parison, and then blow molding is added. Multi-layer systems that have been used in industry include polyamide/polyolefin, polystyrene/polyacrylonitrile/polypropylene, polyolefin/polyvinyl chloride, etc.
Multi-layer blow molding is a technology that uses one,two or more extruder screw to melt and knead the same or dissimilar plastics in different extruders, compound and extrude them in the same head, and then blow molding to manufacture multi-layer hollow containers.
Multi-layer blow molding is developed on the basis of injection blow molding and extrusion blow molding. There is no big difference in process, but the product wall is not a single layer but multiple layers. The multilayer structures used are: nylon/polyolefin, polyvinyl alcohol/polyolefin, polyethylene/polyvinyl chloride/polyethylene, polystyrene/polyacrylonitrile/polypropylene, etc. Multi-layer blow-molded containers are mainly to meet the increasing airtightness requirements of cosmetics, medicines, and food packaging. Therefore, the raw materials and the number of layers of the multilayer container should be selected according to needs. It can adopt two kinds of plastic two-layer structure, two kinds of plastic three-layer structure, three kinds of plastic four-layer structure or four kinds of plastic four-layer structure, etc. The more levels, the higher the technical requirements.We can produce extrusion blow molding machine with 1 layer,2 layer, 3 layer, 4 layer, 5 layer, 6 layer.
The key to multi-layer blow molding is to control the melt adhesion between the resins of each layer. There are two bonding methods. The first is to mix in resin with adhesive properties, which can reduce the number of layers and maintain a certain strength. The second is to add an adhesive material layer, which requires the addition of an extruder for extruding the adhesive material, which makes the equipment and operation complicated.
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