Analysis of the hottest film covering technology

Under the analysis of film covering technology, composite strength refers to the adhesion fastness between plastic film and paper (board) printing in film covered products. Its size depends on the adhesion between plastic film, paper (board) printing and adhesive (or hot melt adhesive). When laminating, the adhesion mainly comes from the mechanical and physical-chemical adhesion between plastic film, paper (board) printing products and adhesives (or hot melt adhesives)

the key to film fastness lies in the affinity between glue and printed matter (ink and substrate). As a film coating industry, the printing ink is not optional, that is, only the film coating suitable for the ink market is the only choice, so as a pre coating, only the suitable test data are not the same, and the performance of all inks can be regarded as high quality. The composite strength of film coated products is affected by the process parameters in the film coating production process, such as the temperature, pressure, speed of the film coating process, the coating condition of the adhesive, film tension and environmental factors. At the same time, it is also affected by the printing process, such as the surface state of the printed matter formed after printing, such as the thickness of the ink layer, the area and distribution of graphics and texts, the characteristics of the ink, the use of diluent and powder, and the drying of the ink layer

factors affecting film covering quality

1 The ink layer condition of printed matter

refers to the paper property, ink performance, ink layer thickness, graphic area and printed graphic density. When the ink layer of the printed matter is thick and the image and text area is large, many paper fiber pores will be closed, preventing the penetration and diffusion of the adhesive, making it difficult for the printed matter to adhere to the plastic film, and prone to delamination, blistering and other failures

2. Environmental humidity

the water content between the adhesive and plastic film and printed matter changes with the change of air relative humidity. Printing materials sensitive to humidity will produce internal stress due to dimensional changes. For example, the longitudinal expansion rate of printed matter is 0.5%, and the longitudinal thermal shrinkage of BOPP film is 4%. If the printed matter is stretched due to excessive water absorption, it will cause internal stress between the printed matter and the heating shrinkage of the film, which will lead to curling, wrinkling and poor adhesion of the film covered products. In addition, in a high humidity environment, the equilibrium moisture value of the printed matter will also change. A large amount of moisture absorbed from the air medium will be released from the surface during the hot pressing process, stagnate at the bonding interface, and locally form a non bonding phenomenon. Moreover, the change of the equilibrium moisture value of the printed matter (moisture absorption from the air medium or moisture release to the air medium) mostly occurs at the edge of the printed matter, making it form a lotus leaf edge or tight edge, which is not easy to form a good adhesion with the film and produce wrinkles in the hot pressing composite, so that the production cannot proceed smoothly

3. Temperature control

heating can soften the film and make the paper adhere to the plastic film. However, the temperature is too high, and the film is easy to break, which seriously affects the product quality. Therefore, measures such as fan cooling and turning off the electric heating wire should be taken

green development trend of plastic film coating

the paper after film coating becomes a kind of white pollution because it cannot be recycled, and toxic substances such as toluene and Tianna water volatilize in the process of film coating, damaging people's health. Today, when advocating environmental protection and resource protection, plastic film covering technology has been eliminated in Europe and the United States, and Europe and the United States even refuse to import all kinds of packaging materials with plastic film. Although there are water-based plastic film coating process and hot-melt pre coating dry plastic composite process, the former still fails to solve the problem that the waste of film coated printing materials cannot be degraded and recycled. The latter requires a lot of heat in the production process, and the waste can be separated from paper and plastic only in 60 ℃ water, so the cost is high

with the improvement of environmental protection awareness, new scientific and technological achievements will eliminate the products of the old process and make qualitative changes in the coating process. Non toxic, harmless, green and environmental protection naturally become the inevitable development trend of the coating process. In addition, the glazing process is therefore favored. Glazing is to add a layer of colorless transparent paint on the surface of printed matter by painting, spraying or printing, that is, glazing oil. After calendering and drying, it increases the gloss and stiffness of the surface of printed matter. At the same time, the printing waste after glazing can be recycled or decomposed by itself, which does not pollute the environment. Therefore, glazing is a processing process with great development potential without manual handling of newly produced aluminum materials, It is possible to gradually occupy the plastic film covering process market. Although the diluting machines used in the oil-based glazing and alcohol-based glazing on the market are toluene and alcohol respectively, which are harmful to human body and environmental protection, water-based glazing has gradually become the mainstream of glazing process. At present, the water-based UV glazing process that has been developed is an ideal environmental friendly glazing process, and it is also the development direction of glazing process in the future