Film coating is a kind of widely used printed surface finishing technology. With this technology, it can not only make the prints look bright and beautiful, but also give them waterproof, moisture-proof, oil-proof, abrasion-resistant and other characteristics. It also improves the artistic effect and practical value of prints. At present, this process is widely used in the printing of book covers, packaging cartons, maps, calendars, and exquisite pictures.
With the promotion and popularization of the lamination process, the demand for adhesives required by it has rapidly increased. At present, most of the adhesives used for the film are organic solvent adhesives. Due to the large amount of organic solvents used, it not only harms the health of employees but also seriously pollutes the environment. In response to these problems, many equipment manufacturers are constantly developing mechanisms and new processes, and the introduction and application of water-based special laminating machines have completely solved the problems of solvent-based adhesives being flammable, explosive, and polluting the environment. However, due to the large number of ready-to-use laminating machines (solvent-type coating machines) on the market, it is also an urgent and meaningful task to develop and use water-based film adhesives using existing equipment. After many efforts, a number of manufacturers of coated adhesives have developed and produced such water-based adhesives, which have been used by the film manufacturers.
First, the characteristics of water-based film
The biggest feature of the water-based film is that it is covered under the wet state without heating and drying. When the pressure is applied, the roll pressure is low. After the film is dried, the quality of the film is directly dependent on the uniformity of the coating. . The adhesive film is adhered to the color prints through a pressure roller. The wet water-based adhesive, when wetting the film and printing paper, can also diffuse, flow, and penetrate through the interface between the film and the print paper, filling up the paper defect and printing process. The powdered surface of the print is uneven. After the water in the glue is absorbed by the paper, the water-based glue forms an even and dense layer of film between the film and the color print, so that the surface smoothness, transparency, and gloss of the film product are much higher than those of the solvent-based adhesive film. product.
Second, water-based special laminator, that is, the composition of the coating laminator and technical requirements for water-based adhesive
Water-based special laminating machine is mainly composed of unwinding, gluing coating, compounding, winding four parts and mechanical drive, electrical control and other ancillary devices.
The coating type laminating machine is mainly composed of five parts, namely unwinding, sizing coating, drying, compounding, and winding, as well as mechanical driving and electrical control.
The sizing coating of the water-based special laminating machine adopts the roll-to-roll direct extrusion coating, and the sizing coating machine mostly uses the roll-to-roll reversal type indirect coating.
Due to the differences in the gluing devices of the two laminating machines, the technical requirements for water-based adhesives are also different.
The water-based special laminator chooses the VAE water emulsion adhesive with a solid content of ≥50% and a viscosity in the range of 800-1600CPS (25°C rotational viscosity).
That is, the coating type laminating machine chooses the acrylic type water emulsion adhesive whose solid content is ≥30% and the viscosity is in the range of 100-200CPS (25 degree Celsius rotation viscosity).
