Pre-coating film coating technology and its influence on the binding of bookbinding
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In recent years, the film is basically a pre-coated film. Since the use time is not long and there are many problems, according to the process practice, the quality of the precoat film is mainly temperature and pressure. Three factors of speed, so the correct handling of the relationship between the three is essential to ensure the quality of the precoat film and the impact on the production of the next process.
Paper-plastic coating is the comprehensive result of the physical interaction of thermal compression. Temperature, pressure and speed are the three basic factors to achieve this kind of physical integration. Correctly handling the relationship between these three is the key to the process operation technology.
Temperature: It is the first key of the film. The adhesive for the pre-coating film is hot melt adhesive. The temperature determines the melting state of the hot melt adhesive, which determines the leveling performance of the hot melt adhesive and determines the molecular direction of the hot melt adhesive. BOPP film, printing ink layer, paper substrate and other three molecules diffusion ability, but also determines the crystallinity of hot melt adhesive, only the correct control of the temperature of the working area, in order to make the precoat film solid heat on the film The molten rubber 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 to ensure immediate curing after compounding. The laminated product is made to have a flat appearance, is bright enough, has a good degree of melting of the rubber layer, and has no crease. 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 precoat film coating. According to our practice. The temperature control is preferably in the range of about 80 to 100C.
Pressure: 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 be in the process of driving away the air on the surface of the printed matter. Fully wet the surface of the paper print. Produce colloidal molecules to the ink layer of the paper print, the diffusion between the paper molecules, dislocation, and achieve good adhesion, forming a complete coverage of the entire surface of the printed matter, so that the printed matter reaches a bright, no fog, the rubber layer is level, no crease The bonding effect is good, and the pressure can be properly increased without wrinkles, so that the thermoplastic curing machine of the hot melt adhesive can be fully expressed. In order to ensure that the film product is added after the compounding process. It has strong resistance to various physical peeling, impact and other effects. (such as indentation, bronzing, hot melt glue, etc.) to achieve a perfect unity of the internal structure and surface state of the composite print.
Speed: Paper overlay is a composite motion that is in progress. The speed of movement determines the time during which the paper-plastic composite stays on the thermocompression working interface, and also determines the temperature and pressure of the laminator input and the cooperation of paper and plastic in the actual production process. Actual action value. When the film temperature and pressure are fixed. The change of speed will change the coating effect, and because of the upper limit of temperature and the limitation of pressure supply, it will only change from the direction less than the set value, and with the acceleration of speed, the amplitude will decrease obviously, and the hot pressing force will decline. Make the composite effect worse. Running too fast. Bonding is not strong. There will be fog, too slow to be inefficient. Even bubbling. So the compound runs at a speed. 4. Determine the time for the precoat film and paper print to achieve bonding. According to our experience, the general speed control is suitable for about 10-20 sheets of paper in one minute. (The speed of the electronic laminating machine is small due to the hot pressing roller. The speed should be slower)
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 to ensure the composite effect of the pre-coating film and create favorable conditions for the spine cover of the next process without leaving the shell and not blistering. The pre-coating compound, how to create favorable conditions for the next process (including indentation, bronzing, vinyl binding, etc.) is also one of the important factors that we should consider in the process of using the pre-coated film. When the precoat film is combined with the paper print. The lower limit is 80C and the upper limit is 100C. Intuitively, after the composite body is separated from the hot press roller, the brightness is high, no fog, good flatness, and no blistering. In such a temperature range, the hot melt adhesive can fully receive heat from the outside to the inside. Function, the modification of various raw materials in the gel body can be fully exerted, and the entire rubber layer is completely melted. Produces a true, firm bond, rather than a superficial, shallow, unshelled or blistering phenomenon that does not bend or reheat.
When the lower limit temperature is slightly downward, the brightness of the composite product will decrease. When the upper limit temperature is slightly increased, bubbles that are not smooth and have different shapes are burned on the surface of the film. (This phenomenon is particularly obvious in the electronic laminating machine) just right to grasp the critical working area of the film temperature. Not only the composite effect is good, but also the hot melt colloid is close to the hot spot of the cross-linking reaction. The solidification of the colloid is hard, so that it will not soften easily when it is heated again. The correct temperature control method for the film operation is to master this finely. The film temperature is very close to the crosslinking reaction temperature.