The hottest talk about pre film removal and film c

2022-09-27
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Talking about the operation technology of pre removing film and its influence on the binding suitability of binding cover

in recent years, the film covering of teaching materials basically uses pre coating. Because we haven't used it for a long time and there are many problems, according to our process practice, it is mainly temperature and pressure that affect the quality of pre coating film. Speed is the three major factors, so it is very important to correctly deal with the relationship between the three to ensure the quality of pre coating and the impact on the production of the next process

we know that paper plastic coating is the comprehensive result of the physical effect of hot pressing. Temperature, pressure and speed are the three basic factors to realize this physical comprehensive effect. Correctly handling the relationship between these three factors is the key to the process operation technology

temperature: it is the first key of film covering. The adhesive used for pre coating is hot melt adhesive. Temperature determines the melting state of hot melt adhesive, the leveling performance of hot melt adhesive, the diffusion ability of hot melt adhesive molecules to BOPP film, printing ink layer, paper substrate and other three substances, and also determines the crystallinity of hot melt adhesive. Only by correctly controlling the temperature of the working area, Only in this way can the solid-state hot-melt adhesive layer of the pre coating film on the film be completely melted into a viscous flow state, with appropriate fluidity to realize the wetting and bonding to the surface of the printed matter, and at the same time, ensure the real-time curing after compounding, so that the laminating product has a flat appearance, enough brightness, good melting degree of the adhesive layer, and no creases. And can peel off the ink. The temperature control of the film covering process also affects and determines the change when the film is heated with hot melt adhesive, as well as the resistance to new heat. Therefore, strict control of temperature is the primary key to precoating. According to our practice, it is appropriate to control the temperature in the range of 80 ~ 100 C

pressure: proper pressure should be used while correctly controlling the cladding temperature, because the surface of the paper itself is not very flat. Only under the action of pressure, the hot melt adhesive in viscous state can fully wet the surface of the paper print in the process of driving away the air on the surface of the print. Produce the diffusion and dislocation of colloidal molecules to the ink layer of paper prints and between paper molecules, realize good bonding, and form a complete coverage of the whole surface of the print, so that the print is bright, free of fog, the glue layer is flat, free of creases, and the bonding effect is good. Under the condition of no creases, appropriately increase the pressure, Only in this way can the thermoplastic curing function of the hot melt adhesive be fully displayed, so as to ensure that the coated products have strong resistance to various physical peeling, impact and other effects after compounding (such as indentation, bronzing, hot melt adhesive skin, etc.), so as to achieve the perfect unified speed of the internal structure and surface state of the composite printing products: the paper lamination is a dynamic compounding movement. Its movement speed determines the residence time of the paper plastic composite on the hot pressing working interface of the hot pressing body, as well as the input temperature and pressure of the laminating machine and the actual action value of the paper plastic composite in the actual production process. When the laminating temperature and pressure are fixed,

the change of speed will change the laminating effect, and due to the limitation of upper temperature limit and pressure supply, It will only change from the direction less than the set value, and with the acceleration of the speed, the decrease is obvious, and the hot pressing force declines, making the composite effect worse. If the operation speed is too fast and the bonding is not firm, it will be foggy, and if it is too slow, it will be inefficient and even foaming

therefore, the composite running speed determines the time for the pre coating and paper printing to achieve bonding. According to our experience, it is generally appropriate to control the speed at about one minute of split paper. (electronic lamination 5. Press to stop and start the CLR button machine. The speed should be slow because the hot pressing roller is small)

the actual action value of temperature, pressure and speed has a certain range. Due to the different equipment, we need to find the best action value of rail transit in practice, so as to ensure the composite effect of pre coating and create favorable conditions for the spine of the adhesive nail cover in the next process to not leave the shell and not blister. It is necessary to rotate the cord and its related parts by 90 degrees

the compounding of pre coating and how to create favorable conditions for the next process (including indentation, bronzing, wireless binding, cover, etc.) are also one of the important factors that we should consider in the process of using pre coating for coating operation

the lower limit is 80C and the upper limit is 100C when the pre coating film is combined with paper printed matter. It is intuitively based on the high brightness, no fogging, good flatness and no foaming of the composite after it is separated from the hot pressing roller. In such a temperature region, the hot melt adhesive can fully accept the role of heat from the outside to the deep inside. The modification of various raw materials in the colloid after blending can be brought into full play, and the whole adhesive layer is completely melted, resulting in real and firm bonding, rather than surface, shallow Do not bend or reheat the shell and blister

when the lower limit temperature is slightly lower, the brightness of the composite product will decrease. When the upper limit temperature rises slightly, uneven bubbles with different shapes will appear on the surface of the film. (this phenomenon is particularly obvious in the electronic laminating machine) properly grasp the critical working area of the lamination temperature. Not only the lamination effect is good, but also the hot-melt colloid is close to the hot spot of the cross-linking reaction, and the solidification of the colloid is almost hard, so it will not soften easily when it is heated again. The correct temperature control method of the lamination operation is to accurately grasp the lamination temperature which is very close to the cross-linking reaction temperature

recently, when we used the pre coated film to glue the cover and then hand it in for binding for wireless binding, we found that most of the binding skins that were divided after rewinding had the phenomenon of spine shelling and blistering, while the phenomenon did not occur when the film was separated from the heat source by means of water cooling and real-time automatic segmentation. (our equipment is equipped with water cooling system, automatic segmentation system and winding system for optional use) the curing time of hot melt adhesive for film coating is about 10 ~ 15s, and the time required for natural cooling at normal temperature in the production environment is greater than this standard time, especially if the semi-finished products are wound in layers before cutting. The temperature accumulation between each other is difficult to emit, which prolongs the natural cooling and curing, Usually, it will be cooled and solidified slowly naturally, which will gradually make the hot melt adhesive form crystals. The formation of crystals improves the sensitivity of the colloid to temperature, may cause the re softening of the hot melt adhesive, and weaken the heat resistance function of high-temperature film covering operation to make it approximate to cross-linking reaction. Therefore, we use water cooling and real-time automatic segmentation to prevent heat accumulation, Create a low-temperature quenching curing zone in real time for the coated product after it is separated from the heat source. Let it cool down quickly. The viscosity of the hot melt adhesive in the molten state increases rapidly. There is no time for the refining section to move. It is difficult to form crystals, which can make the coated product not melt and soften obviously when it is heated up again. For wireless binding, ensure that the spine will not be separated from the shell when it is heated again Blistering phenomenon. In order to ensure the adaptability of wireless binding, it creates good conditions for large-scale application in the field of intelligent textile, so as to ensure the quality of binding and film covered products

(Zhong Jiexiong)

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