The basic preparation process of composite packaging bag includes printing, compounding, cutting and bag making. Compounding and bag making are the key processes that affect the product performance.
　　Composite process
　　In the design of product packaging process, in addition to the correct selection of various substrates, the selection of composite packaging bag composite adhesive is also very important, which should be selected according to the use, composition, post-processing conditions and quality requirements of the product. If the wrong adhesive is selected and the composite processing technology is improved, it will also cause problems such as poor adhesion, low post-processing adhesion, poor compounding, liquid leakage, broken bags and so on.

　　　　　　Many factors should be considered in the selection of composite packaging bags. Generally speaking, as a composite adhesive, the following conditions shall be met:
　　1. non toxic;
　　2. no harmful extract after liquid packaging;
　　3. temperature requirements applicable to food storage;
　　4. good weather resistance, no yellowing, no foaming, no chalking and no layering;
　　5. resistant to oil, essence, vinegar and alcohol;
　　6. it does not corrode ink and has high affinity for ink.
　　In addition, the flexibility, operability, adhesion durability, medium corrosion resistance and hygiene of composite packaging bags should not be ignored. In terms of medium corrosion resistance, the contents include spices, alcohol, water, sugar, fatty acids, etc., They have different characteristics. It is very likely that they will penetrate into the adhesive layer through the inner layer of the composite membrane, causing corrosion damage, leading to delamination and fracture of the packaging bag, resulting in failure. Therefore, the adhesive should have the ability to resist the erosion of the above substances and always maintain sufficient adhesive peel strength.
　　The composite processing methods of plastic film include dry composite method, wet composite method, extrusion composite method, hot melt composite method and co extrusion composite method.
　　Dry compounding is a common method in composite packaging bags. Under certain temperature, tension and speed, a layer of solvent based adhesive (one component hot melt adhesive or two-component reactive adhesive) is uniformly coated on the substrate. The solvent is volatilized and dried through the drying tunnel of the laminator (divided into three areas: evaporation area, hardening area and deodorization area), and then bonded with the substrate (plastic film, paper or aluminum foil) through the hot pressing roller to form a composite film.
　　Wet compounding refers to coating a layer of adhesive on the surface of composite base material (plastic film, aluminum foil) of composite packaging bag, compounding with other materials (paper, cellophane) through pressure roller, and then drying in oven to form composite film.