The schoolbooks are basically coated with thermal lamination film in recent years. Due to the usage time is not long, there are many problems on the laminating process. According to the practice experience, temperature, pressure and speed are the three major factors have influenced the laminating quality. So, control these three factors well will be very important for ensuring the laminating quality and production process.
Paper/plastic compound is the physical effect by hot laminating. Temperature, pressure and speed are the three basic physical factors during this physical effect. Handle these three factors correctly will be the key operation technology.
Temperature: it is the first key factor in the laminating. Because the bonding adhesive is the hot melt glue, the temperature will determines their molten state, the diffusivity from colloidal molecular to the BOPP lamination film, print ink and paper these three kinds of material and the crystallinity of the hot melt glue. Only control the working temperature correctly, the solid hot melt glue on the lamination film surface will melt into flow state directly and bond with the printed paper well, also solidify after compound. This will make the printed paper be smooth, bright, glue melting good, no fold and the print ink can’t be detached.
Temperature controlling during the laminating process will influence and determine the heating change of the hot melt glue, as well as the counterbalance of new heating effort. Therefore, strictly control the temperature is the primary key in laminating. According to our practice, temperature controlling is between 80 ~ 100 ℃ is more appropriate.
Pressure: Be sure controlling the temperature correctly, at the same time, using the appropriate pressure. Because the surface of the paper is not very smooth, only under the pressure, the flow state of hot melt adhesive will wet the printed paper and run fully on its surface, the colloidal molecular will diffuse, dislocate and bond well with the molecular of print ink, paper, then fully laminating on the printed paper surface. Ensuring the printed paper be more light, no mist, level layer, no fold and good bonding. In case of the printed paper without folding, increased the pressure will let the hot melt glue works well and improves the resistance to physical dissection and wallop force during laminating (such as impression, gold stamping), let the internal structure and surface state of the printed paper achieve the perfect performance.
Speed: paper coating is the composite motion in dynamics, the speed will determines the residence time between paper/plastic and hot roller in working interface, also determines the effect of paper/plastic compound under the laminating machine input temperature, pressure. After the lamination temperature and pressure are constant, speed change will cause the lamination effect change. Due to the maximum temperature and pressure supply constraints, the working temperature only less than the set temperature. Faster the laminating speed, the working temperature will be much lower down and the laminating pressing force will decline, this will call the compound deterioration. Faster laminating speed will cause mist and bonding not strong. Slower laminating speed will cause blistering and no efficiency. So, the laminating temperature determines the bonding time between the lamination film and schoolbook. In our experience, the general speed of delivery paper in 10-20 sheet/minute will be appropriate. (Because of smaller laminating roller, the electronic laminator speed should be a little lower down)
Temperature, pressure and speed, this three factors have a certain range of values during the practical process. Because of different equipment, which requires us to find the best in practice range, to ensure that the composite effect of laminating be better.