Advice from the application of water-based film processing technology
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The film is a composite film of 15-20lJm thick and printed matter to improve the gloss and strength of the surface of the printed matter and enhance the visual beauty. The film is generally oily, water-based and hot-pressed. Water-based film is economical and is the most popular way of film coating in China. However, due to its inherent characteristics, it is inherently insufficient, and it should be used with caution in some products.
1. Not suitable for large area (especially large field) graphic product film
The water-based film glue contains a certain amount of water. When used for large-area (especially large-scale) graphic products, it will show a large area of snow-like spots on the surface of the image, thus affecting the appearance quality of the product. . Although the amount of sizing is not much improved, it can only be replaced by an oily or hot-press pre-coating film coating process.
2. Not suitable for sizing of offset paper
I have used water-based film glue from different regions and manufacturers for batch trial production. Compared with oil-based, especially two-component glue film, the film is coated on the offset paper product. The water-based film product is easy to cause paper-plastic. Disengagement, sometimes a tear, the film and the print are completely separable, which is easy to cause a quality accident.
3. Double-sided film products are used with caution
Some products require double-sided film coating due to customer requirements, such as water-based film coating process. Because of the high water content in the glue, the water is difficult to volatilize after the film is coated, which makes the crystals soft and can't reach. The customer's request brings unexpected quality accidents.
4. It is not easy to carry out concave and convex processing after film coating
When the water-based film is subjected to pressure-concave processing, white spots and wrinkles are formed on the contact surface, and the sticking is not strong, and when it is severe, foaming occurs, and the paper is more prominent on the coated paper. We can pay attention to the cover of some adhesive book covers. The cover side of the water-coated film is not very straight, and there are embossed marks on the uneven surface, which seriously affects the appearance of the product.
5. Subsequent processing waits, preparation time is too long
Water-based film products must be placed in a flat shape after 24-48 hours. Sometimes it can be poured into the next process after 40-500 degrees of baking. The main purpose is to volatilize the moisture of the glue to stabilize the bonding strength and the stiffness of the film product. Sometimes special aids are required to meet the requirements of post-press processing.
For a product to save costs, the cover uses 105g/m2 double-sided coated paper. After the water-based single-sided coating, the cover is too soft and static electricity is easily adhered. The method of baking 72h and lightly coating talcum powder also failed to solve the problem that the cover cannot be automatically conveyed on the disc binder. Finally, I came up with the trick: put it into the -40 degree freezer and freeze it. After freezing for 2 hours, it will become straight. After a certain degree of stiffness, it will be glued to the machine and then barely complete the production task.
6. Printed graphic color change
Mainly in the filming of large-area spot color prints, such as the color of the printing of gold, silver ink products will be unexpected changes. The reason is that this is due to the chemical reaction between some chemicals in the glue and water and gold ink (more copper powder) or silver ink (more aluminum powder). At this time, only the coating process can be changed, and the oil-based or hot-press pre-coating process is used instead.
Of course, water-based film products also have their own unique features. For the saddle-stitched cover, especially the thin cover, the water-based film will not be curled by moisture. At the same time, it also has the following requirements: low production suitability, suitable for large-scale production line production; low investment cost, low comprehensive cost, etc., and economical. The most commendable thing is that it is not easy to pollute the environment, it is an environmentally friendly product, it is the development direction of the film, and it will have a place in a specific product. If it can solve the defects of current water-based glue, its application prospect is broad.