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What are the common composite methods of plastic flexible packaging? What are their characteristics?

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the compounding methods of plastic film mainly include:
1. Dry compounding method
dry compounding method is a composite processing process in which the adhesive (glue) is coated on a kind of plastic film, then the excess solvent is volatilized through the drying channel, and then pressed together with another kind of plastic film by hot pressing roller. This composite processing technology has great flexibility in batch and quantity requirements, and can carry out composite processing of multi variety and multi-layer films. It is suitable for compound processing of packaging products with complex variety, small batch and wide variety. This processing method is especially suitable for the characteristics of China’s food and small food, such as wide variety, small batch and fast renovation. The disadvantage of its processing method is that it is difficult to compound too thin films (films below 0.02mm), which are expensive and easy to leave adhesive, flux and peculiar smell. The length of drying channel, heating mode, gluing mode, gluing amount control, material tension control, hot drum temperature control and whether it has cooling and setting device determine its price and grade. At present, two-component adhesives are widely used in domestic dry composite, and single component adhesives are also used by small manufacturers and individual products. The water-soluble adhesive not only meets the requirements of environmental protection, but also has no solvent residue. However, the combination of plastic and plastic has not been used in batch, but it is only used in the wet combination of metal aluminum foil and paper. One component adhesive has strong odor, non curing, non temperature resistance and poor composite firmness, so it is not suitable to be used in food packaging
in addition, if PE film should be used as composite lining for a long time, especially for thick PE film, special attention should be paid to the surface tension of PE (polyethylene) film. Generally, it should be more than 42 ~ 52dyn to ensure the firmness after coating (it is recommended to install spark processor on the coating machine)
2. Wet compounding method
wet compounding method is to apply adhesive (glue) to the film (foil), press it with the compound, and then dry it through the drying channel. It is usually the composite method used in the composite processing of metal aluminum foil or plastic film and paper, and the water-soluble adhesive is used in the composite
3. Extrusion (tape casting and film coating) composite method
extrusion (tape casting and film coating) composite method refers to the composite processing process of extruding PE or PP material into film after hot melting, that is, melting the resin, extruding and pouring it on plastic film, web paper, calendered metal aluminum foil and vacuum aluminized film, and cooling after pressing. The composite finished product formed by hot pressing on the printing film is characterized by low cost and reduced glue pollution. However, it is necessary to select the model of extrusion material and control the extrusion temperature. In addition, adding a small amount of primer or AC agent as coupling agent between film-forming will have a better effect on the composite firmness. The method of extrusion (tape casting and film coating) composite is suitable for the production of large quantities of varieties, but the composite film (film above 0.05mm) cannot be used
4. Coextrusion compounding method
coextrusion compounding method is a processing technology that melts a single resin or multiple resins and extrudes and copolymerizes them into a film through several die heads (blowing film or tape casting film). This kind of composite does not use adhesive, so there is no residual solvent in the composite film
5. Solvent free compounding method
solvent free compounding method is to make plastic film with precoated hot melt adhesive layer. Press together with another layer of plastic film by hot roller. This kind of compound way is energy-saving, energy-saving, time-saving and less pollution, which is the direction of development in the future. However, due to the high cost of solvent-free composite equipment, composite glue and technology, it is rarely used in China.

dry compounding, extrusion compounding, solvent-free, dry compounding is the most common, and the future development trend is solvent-free

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