A polypropylene plastic film is coated on the surface of the book cover and other printed products to improve the surface brightness, so that it has functions such as moisture resistance, antifouling, and folding resistance. After the film is printed, the printed products appear bright and luxurious, and the taste value is greatly improved.
In addition, the excellent adhesion of the hydrosol can produce good affinity to the ink layer. No more organic solvents, no erosion on the paper and ink of the printed matter, no wrinkling, loss of adhesion, and film release. At the same time, the potential fire hazards are eliminated at the production site and warehouse, ensuring safe production. No longer use organic solvents, no volatile pollution of harmful gases, comply with national environmental protection requirements, purify the production environment, and protect human health. In addition, it can perform lamination processing on the printed product that has just been printed and the ink layer is not completely dried, saving man-hours and shortening the processing cycle. And because of its light resistance, it does not cause bleeding and discoloration of ink pigments, and does not return to yellow due to aging. Hydrosols are cheap in price, low in dosage and low in cost. Hydrosols are now basically replacing the use of hot-melt resin adhesives.
However, due to operation and other reasons, the products after coating often appear unlit, blistering, wrinkling and other phenomena. Now talk about the handling of common problems in operation.
1. temperature control
In rainy or rainy seasons, if the temperature is not adjusted properly, the coated product will not shine. There is obvious water vapor on the silicone roller, which is caused by the paper absorbing a lot of moisture. At this time, the temperature of the hot pressing roller can be adjusted to 40 degrees Celsius. If the temperature is too high, it will foam. Some hydrosol laminating machines do not have a heating device, and it is necessary to add a drying lamp before pressing to dry the adhesive layer and reduce foaming.
2. Pressure control
When laminating, the pressure should be adjusted according to the thickness of the paper, generally 5Pa. If the pressure is too high, it will cause film wrinkles and paper deformation.
3. Glue control
The amount of glue is controlled by the gap between the glue roller and the glue roller, and the scraping film is added. Scratch film has a large amount of light glue and a small amount of heavy glue. The amount of glue should be well controlled, so that it can be coated evenly without generating crystal points. If the amount of glue is too large, it will make the product dull. Care should be taken during the gluing process to prevent the tiny particles and impurities after the gel solidifies from remaining in the rubber tray. If it is stuck on the scratched film, a white offset will be produced, causing linear blistering. Before starting the machine, clean the upper roller and the rubber hopper with alcohol-based solvents. If the upper roller is not cleaned, it will cause needle-eye blisters. The glue containing impurities can be diluted with water. After the impurities are precipitated, it is used as a thinner to reduce the waste of glue.
4. Roller cleaning
When the paper is separated, the glue will directly roll on the silicone roller, which will cause accumulation, which is easy to wrinkle the product or affect the brightness of the product. The roller should be cleaned frequently to keep it clean. The drum itself will wrinkle when it is uneven and needs to be replaced.
5. Temperature and humidity control
The temperature and humidity of the environment change greatly, and the paper absorbs moisture to produce a "lotus leaf edge". When the film is coated, the paper is easy to wrinkle, and the balance of temperature and humidity should be maintained. If the temperature of the heating roller is too high, the tight edges of the paper will also wrinkle, and the temperature needs to be controlled as required.
6. Paper feeding control
The skewed paper will wrinkle the paper, so be careful when handling, make the paper even, and the pressure is the same on both sides. When feeding paper, try to stack each paper by 3mm, and control the amount of glue to prevent the overflow of glue. This can reduce the adhesion of products after coating. If the connection is wrinkled or blistered, the pressure should be increased appropriately to maintain the temperature and humidity balance, so that the adhesive will be flat and reduce blistering.
7. Film roll control
Prevent wrinkles caused by inconsistent tension on both sides of the film roll. First select the film with the same elasticity on both sides, and then adjust the tension on both sides of the film to make it balanced and prevent wrinkling. When laminating the film, try to use the film size plus the width of the opening size. For example, if the size is 16 format, try to use 44Omm wide film instead of 460mm wide film, which can save 4% of the cost. When using a 780mm wide film for the 16 format, trim as much as possible to reduce the amount of glue and save glue.
8. Do not use additives in printing, control the amount of powder sprayed
Try not to use additives during the printing process, because it is not easy to dry, and it is easy to blister after coating. And also need to control the amount of powder spraying. Before the lamination, arrange someone to wipe the powder on the cover to reduce the phenomenon of lamination or blistering and make the product bright.
9. Speed ​​control
In the process of laminating, do not change the speed of the host at will. The speed is too fast, and the glue cannot meet the requirements. When the speed is slightly increased, the amount of glue is too large. If the speed is adjusted too low, the amount of glue is reduced and it is easy to foam. In order to ensure that the amount of glue is basically the same, the speed of the laminating machine can be limited to 60% of the highest speed, so that each class runs at the specified speed, and data management is implemented to reduce unnecessary losses.
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