In recent years, the film is basically the use of pre-coated film. As the use of time is not long, there are many problems, according to process practice shows that the quality of pre-coated film coating is mainly temperature and pressure. Three major factors of speed, so the correct handling of the relationship between the three, to ensure the quality of pre-film coating and the impact of the next process to the production of the key.
Paper-plastic coating is a comprehensive result of thermal compression and physical effects. Temperature, pressure, and speed are the three basic factors for achieving this comprehensive physical function. Correctly handling the relationship between these three is the key to process technology.
Temperature: The first key to the film. The adhesive used for the precoat is a hot melt adhesive. The temperature determines the melt state of the hot melt adhesive, determines the leveling performance of the hot melt adhesive, and determines the molecular orientation of the hot melt adhesive. The diffusion ability of three kinds of substances, such as BOPP film, printing ink layer, and paper substrate, also determines the crystallinity of the hot melt adhesive. Only by correctly controlling the temperature of the working area, can the solid heat of the pre-coating film on the film be achieved. The melted layer is completely melted into a viscous state with proper fluidity to achieve wet adhesion to the surface of the printed material and at the same time to ensure immediate curing after compounding. The laminated product has a smooth appearance, enough light, good melting of the adhesive layer, and no crease. And can peel off the ink. The temperature control of the lamination process also influences and determines the change in the thermal resistance of the laminating film when it is heated, as well as its resistance to new thermal forces. Therefore, strict control of temperature is the primary key to precoat film coating. According to our practice. Temperature control in the range of 80 ~ 100C is more appropriate.
Pressure: Appropriate pressure should be used while properly controlling the lamination temperature, because the surface of the paper itself is not very smooth. Only under the effect of pressure, the sticky-flowing hot-melt adhesive will drive away the air on the surface of the printed material. Wet the surface of paper prints. Generates colloidal molecules to the ink layer of paper prints, diffusion between paper molecules, misalignment, and good bonding to form a complete coverage of the entire surface of the print, so that the prints reach a bright, non-foggy, flat, crease-free adhesive layer , Adhesion effect is good, in the case of no wrinkling, appropriate increase in pressure, in order to make full performance of the hot-melt adhesive thermoplastic curing machine. To ensure that the film products in the composite plus after the process. It has strong resistance to various physical peeling and impact forces. (such as indentation, hot stamping, hot melt adhesive, etc.) to achieve the perfect unity of the internal structure and surface state of the composite print.
Speed: Paper overlay is a compound motion that is occurring dynamically. The speed of the movement determines the time for the paper-plastic composite to stay on the hot-pressing work interface of the thermal-compression bond, as well as the temperature and pressure input by the laminating machine, as well as the cooperation between the paper and the plastic during the actual production process. Actual value. When the film temperature and pressure are fixed. The change of speed will cause the film coating effect to change accordingly, and due to the upper limit of temperature and pressure supply, it will only change from the direction less than the set value, and with the speed increase, the drop will be obvious, and the hot pressing force will decline. Deteriorating the compounding effect. Running too fast. Bonding is not strong. There will be fog, too slow it is inefficient. Even blistering. So composite speed. Determine the time for the precoating film and paper print to achieve bonding. According to our experience, the general speed control is appropriate for folio paper about 10-20 minutes a minute. (The speed of the electronic laminator is smaller due to the hot roller. The speed should be slower.)
The actual values ​​of the three factors of temperature, pressure, and speed have a certain range. Due to the different equipment. This requires us to find the best value in practice in order to ensure the composite effect of the pre-coated film and to create favorable conditions for the spine cover of the next process to keep the shell spine free of bubbles. The compounding of the pre-coated film and how to create favorable conditions for the next process (including indentation, bronzing, binding, etc.) is also one of the important factors that we should consider when using the pre-coating film to perform the laminating operation process. Pre-coated film and paper print composite. The lower limit is 80C and the upper limit is 100C. Intuitively, after the composite body is separated from the hot platen roller, it has high brightness, no fogging, good flatness, and no blistering as a benchmark. In such a temperature range, the hot melt adhesive can fully absorb heat from the outside to the inside. The effect of the modification of various raw materials in the gel can be fully utilized, and the entire adhesive layer is completely melted. The result is a true, firm bond, rather than a superficial, shallow, off-shell, blistering phenomenon that must not be bent or reheated.
When the lower limit temperature is slightly down, the brightness of the composite product will decrease. When the upper limit temperature rises slightly, uneven and differently shaped bubbles will be burned on the surface of the film. (This phenomenon is particularly evident in electronic laminating machines.) It is just right to grasp the critical working area of ​​coating temperature. Not only the composite effect is good, but also the hot-melt colloid is close to the cross-linking reaction hotspot, and the colloidal solidification is hardened, so that when it is heated again, it will not be easily softened. The correct temperature control method for the laminating operation is to grasp this finely. The coating temperature is very close to the crosslinking reaction temperature.