The operation of pre-removing film and its influence on the suitability of cover binding

In recent years, the coating of teaching materials is basically pre-coated. Because we have not used it for a long time and there are many problems, according to our process practice, the quality of the pre-coating film is mainly affected by the three factors of temperature, pressure, and speed. The quality of the coating film and the impact on the production of the next process are very important.

We know that the paper-plastic coating will be the comprehensive result of the physical function of thermocompression bonding. Temperature, pressure and speed are the three basic factors to realize this physical comprehensive effect. Correctly handling the relationship between these three is the key to the process operation technology.

Temperature: It is the first key to coating. The adhesive used for pre-coating is hot melt adhesive. Temperature determines the melting state of hot melt adhesive, determines the leveling performance of hot melt adhesive, and determines the molecular orientation of hot melt adhesive. The diffusion ability of three substances, such as BOPP film, printing ink layer, paper substrate, etc., 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-coated film on the film be made The melted adhesive layer is completely melted into a viscous state, with suitable fluidity to achieve wetting and bonding to the surface of the printed matter, while ensuring immediate curing after compounding, so that the laminated film product has a smooth appearance, bright enough, and the degree of melting of the adhesive layer No creases. And can peel off the ink. The temperature control of the coating process also affects and determines the hot-melt adhesive used for the coating to solve the changes when heated, and the resistance to the new heat. Therefore, strict temperature control is the primary key to pre-coating. According to our practice. It is more suitable to control the temperature in the range of 80 ～ 100 ℃.

Pressure: Appropriate pressure should be used while correctly controlling the lamination temperature, because the surface of the paper itself is not very smooth, only under the pressure, the hot melt adhesive in the state of viscous flow will drive away the air on the surface of the printed matter. Fully wet the paper print surface. Produce colloid molecules to the ink layer of paper printed matter, paper molecules, dislocation, and achieve good adhesion, forming a complete coverage of the entire surface of the printed matter, so that the printed matter is bright, no fog, leveling of the glue layer, no creases , The bonding effect is good, and the pressure should be increased properly without wrinkling, so that the thermoplastic curing function of the hot melt adhesive can be fully expressed, so as to ensure that the film products are added to the various processes after compounding. The physical peeling, impact force and other influences have strong resistance (such as indentation, bronzing, etc.) to achieve the perfect uniform speed of the internal structure and surface state of the composite print: the paper film is a dynamic compound motion in progress . The movement speed determines the time that the paper-plastic composite stays on the hot-pressed working interface of the hot-pressed body, and also determines the temperature and pressure input by the laminating machine and the paper-plastic complex cooperation in the actual production process. The actual value is when the temperature and pressure of the film are fixed. [next]

The change in speed will change the effect of the coating, and due to the upper temperature limit and the pressure supply limit, it will only change from the direction less than the set value, and with the speed increase, the decrease will be obvious, and the hot pressure force will decline. Make the composite effect worse. The running speed is too fast, the bonding is not strong, there will be mist, and if it is too slow, it will be inefficient, or even foam.

Therefore, the compound running speed determines the time for the pre-coated film and paper print to achieve bonding. According to our experience, it is generally appropriate to control the speed at about 10 to 20 sheets of paper in one minute (the speed of the electronic laminating machine should be slower due to the smaller heat pressing roller).

The actual action value of the three factors of temperature, pressure and speed has a certain range. Due to the different equipment, we need to find the best effect value in practice to ensure the composite effect of the pre-coating film and create favorable conditions for the spine of the cover of the next step of the nail cover to not leave the shell and not foam.

The compounding of the pre-coating film and how to create favorable conditions for the following processes (including indentation, bronzing, and wireless binding on the cover, etc.) are also one of the important factors worth considering in the process of using the pre-coating film for the laminating operation.

When the pre-coated film is combined with the paper print, the lower limit is 80 ° C and the upper limit is 100 ° C. Intuitively based on the high brightness, no fogging, good flatness and no blistering after the composite body is detached from the hot-pressing roller, in this temperature range, the hot melt adhesive can fully receive the heat from the outside to the deep inside Function, the modification of the various raw materials in the colloid can be fully exerted, and the entire adhesive layer is completely melted, resulting in a true and strong bond, rather than the surface, shallow layer, and must not be bent or The phenomenon of shelling and blistering after reheating. [next]

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 will be scalded on the surface of the film (this phenomenon is particularly obvious in electronic laminating machines). Just grasp the critical working temperature 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 curing of the colloid is almost hard, so that it will not be easily softened when it is heated again. This film temperature is very close to the cross-linking reaction temperature.

Recently, when we used a pre-coated film to cover the cover and then bound it for wireless binding, it was found that most of the binding and binding skins that were divided after rewinding had spine detachment and blistering, which made the cover After the film leaves the heat source, the method of water cooling and immediate automatic segmentation do not have this phenomenon (some equipment is equipped with a water cooling system, an automatic segmentation system, and a winding system for optional use). The curing time of the hot melt adhesive for coating is about 10-15s. 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 stacked and wound before division, the temperature accumulation between them is difficult Disperse to prolong the natural cooling and solidification, usually naturally cool and solidify slowly, and the hot melt adhesive will gradually form crystals. The formation of crystals improves the sensitivity of the colloid to temperature, may cause the hot melt adhesive to soften again, and weakens the high temperature coating operation to make it approximate the heat resistance function of the cross-linking reaction, so we use water cooling and immediate automatic Split to prevent heat accumulation, and to create a low temperature quenching and curing zone for the coated products immediately after being separated from the heat source. Let it cool down quickly, so that the viscosity of the hot melt adhesive in the molten state increases rapidly, the chain links are too late to move, and the crystals are difficult to form. This can make the coated product heat without remarkably melting and softening. Binding to ensure that the spine will not leave the case and blisters when the temperature is 30 ° again. In order to ensure the suitability of wireless perfect binding, it has created good conditions and made the quality of perfect binding and laminating products more guaranteed.

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