Composite Process of Printing

1. Corona treatment of plastic film surface:

       Before printing and compounding, the substrate PE, PP and even aluminum foil must be subject to surface corona treatment. The purpose is to improve the firmness of printing and compounding, make it achieve the expected effect.Composite Process of Printing

       And ensure that the critical surface tension during printing and compounding is greater than 38 Mn / M; For the composite film used for cooking, the thickness of the inner substrate shall be greater than 70 μ， To ensure sufficient heat sealing strength.Composite Process of Printing

2. Composite process:

       The composite film can improve various characteristics of a single film and improve the protection of the contents, including moisture resistance, oil resistance, barrier, shading and air tightness. According to different substrates and different applications, the processing methods of composite films can be roughly divided into the following five categories:Composite Process of Printing

A. Dry compound method

        In this method, the adhesive is coated on the surface of the substrate through a laminating machine and combined by heating and rolling on other films. This method can be applied to almost all substrates and can be compounded in many layers.Composite Process of Printing

          It has been widely popularized in all fields of packaging materials. The equipment cost is cheaper than that of extruder. Recently, due to the more strict requirements for packaging function due to cooking treatment and boiling sterilization, polyurethane series with excellent adhesion are mostly used as adhesives.Composite Process of Printing

        In addition, in the dry compounding process, residual solvents lead to hazardous problems such as public hazards, fire and explosion.Composite Process of Printing

        In order to solve these problems, a compounding system with different organic solvents should be developed, which has the following advantages:Composite Process of Printing

·Solvent free, reduce environmental pollution.

·No danger of fire and explosion.Composite Process of Printing

·No solvent drying process is required, which can save energy and equipment area.

·There is no etching of printing ink by solvent.Composite Process of Printing

·No solvent recovery unit investment is required.Composite Process of Printing

·The cost is reduced due to the increase of production speed.Composite Process of Printing

B. Wet composite method

        This method is mainly used for compounding aluminum foil with porous materials such as paper, sheet paper and ordinary cellophane. Composite Process of Printing

       Water soluble adhesives (gelatin, starch) and water dispersible adhesives (vinyl acetate latex, etc.) are coated on the surface of the substrate, combined with other materials in a wet state, and then rolled and dried. Composite Process of Printing

        This method is simple to operate, and can be combined with a small amount of adhesive. Aluminum foil with extremely thin thickness (5-6) μ） It can also be compounded. Compared with other compounding methods, it is fast and can be processed in large quantities.Composite Process of Printing

       The processing cost is very low. There is no organic solvent. It has good safety and no residual solvent. The market centered on paper-based materials is relatively stable.Composite Process of Printing

C. Extrusion compound method

        This is the most commonly used method in compound processing. PP, PE EVA (ethylene vinyl acetate copolymer) ionic resin is extruded into thin films, coated and adhered to various films mixed with processing agents (polyethyleneimine, polyurethane resin, etc.), and then cooled and solidified. Composite Process of Printing

       This method saves labor because of the use of adhesive resin (maleic anhydride modified olefin resin, maleic anhydride and other block modified olefin resin, etc.) therefore, no adhesive can be used, and the process can be reduced to reduce the cost.Composite Process of Printing

D. Hot melt composite method

          The method is based on heating molten EVA (ethylene vinyl acetate copolymer) and EEA (ethylene ethyl acrylate copolymer), PE, butyl rubber and other base resin mixed with adhesive such as rosin, xylene resin and styrene resin and adhesive base reducing agent such as paraffin system are coated on the surface of film, paper and aluminum foil, and immediately compounded on other base materials for cooling.Composite Process of Printing

       It is mainly used to produce cover materials for various containers and requires cooking resistance. Mixing adhesive in EVA and other base resin and extruding it as base material for coating can improve heat resistance.Composite Process of Printing

E. Co extrusion composite method

       This method is formed by two or three extruders at the same time, and more than two layers of films can be obtained. There are T-die method and blow molding method, which can carry out a variety of composites and produce ultra-thin films. Composite Process of Printing 

       Japan’s annual output is nearly 10000 tons, while more than a quarter of the composite films in the United States are coextruded films. Composite Process of Printing

         Although this method has no problem in the bonding of the same resin, it can not bond nylon or Eval with polyolefin. The composite membrane with good bonding can be prepared by using modified polyolefin with ionic resin maleic anhydride palace group. Composite Process of Printing

       These co extruded films have absolute advantages in the field of food packaging and have a high market share.Composite Process of Printing