Pre-coating film coating process control points and matters needing attention

The pre-coating film coating film is a paper-plastic product formed by bonding a pre-coated adhesive film with a pressure and a heat of a rubber roller and a heating roller, and adhering to a paper product. The process flow of the precoating film coating is roughly as follows: the paper conveying platform feeds a printed product and the film is filled with the finished product.

Pre-film preparation

(1) The thickness of the BOPP film used for laminating should generally be between 0.01-0.02mm, the transparency should be above 90%, and the thermal shrinkage should be small.
(2) Before applying the machine, check whether the oPP film is in the shelf life, whether the coating layer on the film is even, whether the surface is scratched or crushed. The adhesive surface of the film passes through the heating roller and faces the print.
(3) The rubber roller and heating roller must be kept clean, and the pressure balance rollers on both sides must be flexible.
(4) Adjust and determine the gap of the paper feed roller according to the paper thickness.
(5) Select BOPP film with different width according to the product size, and adjust the side gauge according to the requirements of the product.
(6) Adjust the guide roller so that the tension on both sides of the film is consistent and the surface of the film is free from wrinkles.

Pre-coated film coating process control points

The key technologies of the precoating film coating process are mainly the control of the coating temperature, the coating pressure and the coating speed.

1. Film temperature

Temperature is the primary factor for precoat film coating because the adhesive on the precoat film is a hot melt adhesive, and the temperature determines the melt state of the hot melt adhesive, which determines the hot melt adhesive molecules to the BOPP film, print ink layer, paper, etc. The ability to penetrate and spread. Although the increase in film temperature contributes to the enhancement of the bond strength, excessively high temperatures will cause shrinkage of the film. The surface of the product will be shiny, blistering, and the product will wrinkle. According to practical experience, the film temperature should be controlled between 70 ~ 100 °C.

2. Lamination pressure

The surface of the paper is not even. Only under the appropriate pressure, the hot-melt adhesive in the molten state can completely cover the surface of the printed product, and the film-covered product is bright and has a good adhesive effect. The pressure is small and the adhesiveness is not strong; the pressure is higher, which helps to improve the binding force between the film and the paper product. However, if the pressure is too high, it is easy to wrinkle the product and it is easy to damage the surface of the rubber roller. Deformation reduces the life of the rubber roller. With the increase of pressure, the contact pressure between the rubber roller and the heating roller is increased, the axle head and bearing load of the two rollers are increased, the wear is aggravated, and at the same time, the load of the transmission system is aggravated, so too much pressure will affect the whole machine. Service life.

In actual production, the pressure should be adjusted according to the different paper. For example, for paper with loose paper, the pressure is greater, and vice versa. According to experience, the film pressure is generally set to 8 ~ 25MPa is appropriate.

3. Film speed

The speed of the coating film determines the melting time of the adhesive on the precoat film on the heating roller and the contact time between the film and the paper. With slow lamination, the heating time of the adhesive on the BOPP film is relatively long, the lamination time of the film and the paper is long, and the bonding effect is good, but the production efficiency is low. The film coating speed is fast, the heating time of the adhesive on the BOPP film on the heating roller is short, the contact time between the film and the paper is short, and the adhesive effect is poor. The production speed of domestic pre-film coating equipment is generally controlled between 5-30m/min.

Above the three key technologies in the pre-coating film coating - the coating temperature, the coating pressure and the coating speed have been simply analyzed, but the adjustment coordination between the three should be based on the different equipment used, film Different types of products and different types of films used are flexible, and only in this way can high-quality coated products be obtained.

4. Special printing film coating parameter control

Special print refers to a large print area. Thick ink, dark color, large paper content, large paper size. When laminating such prints, the lamination parameters are generally controlled as follows.
Film temperature: 95 ~ 5 °C
Film pressure: 16 to 25Mpa
Film speed: 5—10m/min