What are the materials used for laminating and gluing in printing technology

What are the materials used for laminating and gluing in printing technology

The main materials for laminating include plastic film, adhesives, and printed materials.

(1) Plastic film

The surface properties of plastic film, such as wetting, adhesion, polarity, crystallinity, and cleanliness, have a certain impact on the quality of the film coating. Therefore, in the process of laminating, it is necessary to strictly control the plastic film, conduct quality testing, and take pre-treatment measures.

(2) Adhesive

The performance of adhesives is related to their cohesive energy, molecular weight, and distribution, including internal stress, viscosity, solid content, affinity, and other properties that must meet the technical requirements of the film. In addition, during the lamination process, it is also necessary to pay attention to the different surface properties of plastic films and printed materials, so different adhesives should be selected.

① EVA hot melt adhesive, transparent colloid, has good adhesion to non-polar materials.

② Polyester adhesive is suitable for the composite of polyester film and printed products with large areas of gold and silver ink, as well as for the composite of aluminum foil printed products.

③ Polyurethane adhesive can improve the adhesion to various plastic films and printed materials, and can cure at room temperature or low temperature. The adhesive layer has high peel strength.

④ Styrene butadiene rubber adhesive has excellent adhesion to non-polar polyethylene polypropylene films, but its disadvantage is the use of toluene and cyclohexane solvents, which are highly toxic

(3) Printed materials

The ink layer condition, ink layer thickness, auxiliary materials, and paper properties of printed materials have a certain impact on the quality of film coating.

① Ink layer condition.

Covering printed materials with ink layers that are not yet dry can cause blistering in the coated products. If the ink layer is too thick, it will seal the fiber capillary pores, hinder the penetration and diffusion of the adhesive, and make it difficult to bond between the printed product and the plastic film. During the laminating process, delamination is prone to occur, especially for laminated products printed with gold or silver ink. Gold and silver ink particles are relatively coarse, and these particles float on the surface of the ink layer to form an irreversible barrier, which can seriously affect the quality of the coating. Therefore, the ink layer of gold and silver ink cannot be too thick.

② Auxiliary materials.

Drying oil, powder coating, and diluting agents are auxiliary materials required during the printing process. These auxiliary materials also have a certain impact on the quality of laminated products. Excessive addition of dry oil can easily form a shiny and smooth low interfacial layer on the surface of the ink layer, making it difficult for the adhesive to wet and penetrate, and affecting the film fastness.

Spraying powder can prevent printed materials from getting dirty, but if the amount of powder sprayed is too large, it will form a small particle layer on the surface of the ink layer. When laminating, it is easy to cause the adhesive to separate from the ink layer, resulting in false adhesion and seriously affecting the quality of the laminating. Therefore, laminated products should avoid or minimize the use of powder coating, and printed materials that have already been powder coated should be treated first.

Dilution agents include white oil, transparent oil (Villi oil), etc. There is a clear layer of powdery particles in the white oil, which is not tightly bound to the connecting material. After printing, these particles will float on the paper and have a certain hindering effect on adhesion. Transparent oil is a slurry made by dispersing and rolling aluminum hydroxide and dry vegetable oil connectors. Due to the light weight of aluminum hydroxide, it often floats on the surface of the ink layer after printing, causing a separation layer between the adhesive and the ink layer during lamination, resulting in adhesion failure or foaming problems.

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What are the materials used for laminating and gluing in printing technology