According to the process practice, the quality of the thermal lamination film is mainly caused by temperature, pressure and speed. Therefore, the correct treatment of the relationship between the three is crucial to ensure the quality of the thermal lamination film.
Temperature is the first key of film coating. The adhesive for thermal lamination film is hot melt adhesive(EVA). The temperature determines the melting state of hot melt adhesive, determines the leveling performance of hot melt adhesive, and determines the hot melt adhesive molecule to BOPP film. The diffusion ability between the three molecules of the printing ink layer and the paper substrate, and also determines the crystallinity of the hot melt adhesive. Only when the temperature of the working area is properly controlled, the solid hot melt adhesive of the laminating film on the film can be made. The layer is completely melted into a viscous flow state, and has suitable fluidity to achieve wet adhesion to the surface of the printed matter, and at the same time ensures immediate curing after compounding, so that the laminated product reaches a flat appearance, is bright enough, has a good degree of melting of the rubber layer, and has no fold. And can peel off the ink. The temperature control of the laminating process also affects and determines the thermal melting of the film to solve the change in heat and the resistance to new heat. Therefore, strict temperature control is the primary key to thermal laminating film coating. According to our practice. The temperature control is preferably in the range of about 80 to 100°C. Special printing the range is 100-120°C.
Appropriate pressure should be used while properly controlling the lamination temperature, because the surface of the paper itself is not very flat. Only under the action of pressure, the hot-melt adhesive in the viscous state will fully run through the air in the surface of the printed matter. And the surface of paper fully wetted.
The colloidal molecules are diffused into the ink layer of the paper print and the molecules of the paper to achieve good adhesion, forming a complete coverage of the entire surface of the printed paper, so that the printed paper reaches a bright, fog-free, flat layer of the adhesive layer, no creases, and sticks. The effect of the joint is good. If the pressure is not increased, the thermal laminating machine of the hot melt adhesive can be fully expressed to ensure the physical peeling of the coated product during the process of compounding. Impact effects such as impact force have strong resistance (such as indentation, bronzing, etc.) to achieve a perfect unity of the internal structure and surface state of the composite print. The general pressure control is suitable for 10-18Mpa.
The speed of laminating determines the time during which the paper-plastic composite is hot-pressed, and also determines the temperature and pressure of the laminator input and the actual effect on the paper-plastic composite during the actual production process. When the film temperature and pressure are fixed, the change of the speed will change the film coating effect, and due to the upper temperature limit and the pressure supply limit, it will only change from the direction smaller than the set value, and with the speed increase, The drop is obvious, the hot pressing force is degraded, the composite effect is deteriorated, the running speed is too fast, the bonding is not strong, there is fog, and if it is too slow, it is inefficient, and even foaming. Therefore, the speed of the composite operation determines the time for the lamination film and the paper print to achieve bonding. According to our experience, the general speed control is suitable for about 8-80m/min.
The actual action value of the three major factors of temperature, pressure and speed has a certain range. Due to the difference in equipment. This requires us to find the best value in practice.