How to solve the problem of improper adhesion of laminating products?

[China Packaging News] In order to improve the surface gloss effect and mechanical resistance of printed products, laminating is a frequently used surface treatment method for printed products. It is suitable for the outer packaging of various products, which can protect and beautify the products and improve The role of added value of goods.

In the process of laminating printed materials, the most prone to quality failure is the poor adhesion of the film of the laminated product and the printed product, which is easy to fall off, which will directly affect the use effect and life of the subsequent laminating product. To solve this problem, we need to consider the printing ink, printing process, laminating process and other aspects.

Printing ink

The laminating process is relatively simple, mainly because the printed matter and the film are well bonded together with an adhesive. The porous structure on the surface of the non-graphic area of ​​the printed product is conducive to the penetration and diffusion of the adhesive, so the ink in the graphic area of ​​the printed product is the main reason for the poor adhesion of the printed product and the film.

The effect of the ink on the coating effect is mainly the effect of the surface properties of the dried ink on the adhesive. When the ink dries, the main component of the surface layer of the ink thinners, but also contain other substances, for example, white ink particles silty components due to insufficient binding force and binders, the ink floats on the surface, further drying; Dimension The aluminum hydroxide in the oil component will also float on the surface of the ink due to its light weight ; the film-forming resin of the bright pulp component can improve the film-forming effect of the ink and is also on the surface of the ink.

When coating, the white ink pigment particles on the surface of the ink will hinder the adhesive and affect the further penetration of the adhesive on the surface of the ink layer of the printed product ; aluminum hydroxide in Willy oil is easy to form an isolation layer and hinder the adhesion The interaction between the agent and the ink layer leads to foaming or poor adhesion ; the bright paste is beneficial to the coating effect, and its composition is similar to the adhesive (the main component is the conjugated multi-bond terpene resin ) , and the affinity effect it is good. Therefore, when adding the ink diluent, it is necessary to consider the product's coating effect.

In addition, the particle size of the ink will also affect the coating effect. If the particle size is too large, it will affect the bonding effect of the film and the surface of the printed product, and it is easy to cause blistering and thus poor adhesion. Especially for gold and silver inks, metal pigment particles will separate after the ink is dried, hindering the mutual bonding of the ink layer and the adhesive, so products printed with gold and silver inks are not suitable for coating.

printing art

The printed matter before lamination needs to be completed by printing. As mentioned above, the surface properties of the dried ink will affect the coating effect, and under the premise of using the appropriate ink, factors such as the printing format, the thickness of the ink layer, and the drying effect will also cause the coating to be poorly bonded.

If the printing area is too large ( or printing in the field ) , the contact area between the paper surface and the adhesive will be reduced, which will aggravate the reduction of the adhesion effect between the surface of the printed product and the adhesive, and greatly reduce the quality and service life of the coated product . Therefore, it is necessary to avoid laminating large-format or on-site printed products as much as possible.

If the ink layer of the printed product is too thick, the hindrance to the adhesive will be increased, which will directly cause delamination and will not bond. Comparing the characteristics of the ink layers obtained by various printing processes, the thickness of the ink layer of the offset printing is the lowest, which is 1 ~ 2 μ m . The final ink layer thickness of the printed product.

Similarly, undried ink will cause the film to swell and stretch, causing the coated product to foam and thus not bond properly. The key to solving this problem is to ensure that the ink is completely dried before laminating. You can use auxiliary drying to speed up production, but you should minimize the use of ink auxiliary agents, because excessive use of drying oil will increase the smoothness and fineness of the ink layer surface. , Thereby exacerbating the unsatisfactory adhesion of the film-coated products. At the same time, we should also pay attention to reducing the use of powder spray and the impact of the workshop environment on the printed film, because the powder spray on the surface of the print and the dust impurities attached to the surface of the print in the workshop will interact with the adhesive and cause The " false bonding " phenomenon makes it easier for the printed matter to separate from the film.

Laminating process

The film-coated product is finally completed by the film-coated process, and its film-coated quality depends on the implementation effect of the film-coated process. The coating process parameters mainly include drying effect ( that is, coating film process ) , compound temperature, compound pressure, adhesive coating condition, and film coating speed. Here, the author analyzes the effect of drying of the adhesive, the adhesive bonding force effects, pressure effects coating three aspects.

1. Drying effect of adhesive

The drying effect of the adhesive is similar to the effect of the drying of the ink on the surface of the printed matter on the quality of the film. If the solvent is not completely dried, the film will expand and stretch, causing foaming, which will result in poor adhesion.

2. The binding effect of the adhesive

The binding effect of the adhesive mainly considers two aspects. One is the application of adhesives, which requires that the adhesive on the film surface is uniform and effective, and the thickness of the adhesive must be controlled according to the surface characteristics and structure of the printed product: too thin the thickness will reduce the bonding of the adhesive Force ; the thickness is too thick, it will affect the drying speed. The second is the recombination temperature, which will affect the molecular energy and molecular force of the adhesive. When the molecular force is too small, the adhesion of the coated product will be too small. In addition, if the recombination temperature is too high, it will cause damage to the film structure. Generally, the recombination temperature should be controlled at 70 ~ 90 ℃.

3. The effect of film pressure

The effect of lamination pressure is affected by two factors, compound pressure and lamination speed. The compound pressure will promote the penetration and diffusion of the adhesive, and its size should be considered in conjunction with the coating material and other processes ; the coating speed is also a multiple influence parameter, and its size will affect the coating thickness and drying speed of the adhesive. Adjust simultaneously with other factors.