How to choose the best material for the laminating film lamination process

The plastic films that are commonly used in the film coating process are: polyvinyl chloride (PVC), polypropylene (PP), and polyester (PET Film, etc.) In order to meet the requirements for the use of the film-covered print, the plastic film should meet the following requirements.
(1) The film thickness is between 0.01 mm and 0.02 mm. After corona treatment or other methods, the surface tension should reach 4.0 x 10-2 N/m so as to have better wetting and bonding properties.
(2) The treatment effect of the film corona treatment surface is uniform, and the higher the transparency, the better, so as to ensure that the printed matter having the best clarity is covered.
(3) The film should have good light fastness, and it should not be discolored when irradiated with light for a long period of time, and the geometric dimensions remain stable.
(4) The film should be in contact with solvents, adhesives, inks and other chemical substances. The film should have a certain degree of chemical stability.
(5) The appearance of the film should be smooth, free of irregularities and wrinkles, and free from bubbles, shrinkage holes, and pitting.

Structure features of the pre-coating film The pre-coating film is composed of a substrate and a binder layer, and the substrate is usually a polyester (PET) film and a biaxially oriented polypropylene (BOPP) film. BOPP film has the characteristics of high transparency, good brightness, non-toxic and tasteless, water resistance, heat resistance, low cost, and soft texture. It is an ideal material for the film coating process, and its thickness is about 12-20um, therefore, from the material cost Considering the processing technology, most of the precoated substrates use BOPP Film.

The adhesive layer of the precoat film has two types of melting type and solvent evaporation type. According to different processing equipment and process conditions, adhesive layers with different thicknesses are selected. The thickness of the adhesive layer is generally between 5 and 15 um. At present, the adhesive layer of domestic pre-film is mainly composed of hot-melt adhesive or organic polymer low-temperature resin. Hot-melt adhesives are made by blending several kinds of materials such as main adhesive resin, tackifier and conditioner. The organic polymer resin is a single polymer low temperature copolymer. Since the hot melt adhesive is made of a mixture of several materials, the transparency after lamination is significantly lower than that of the low-temperature pure resin type.

The solvent evaporation type precoating film production process is similar to that of the coating film coating process. The organic solvent dissolves the colloid and then coats the film substrate, so there may be incomplete volatilization of the organic solvent and abnormal odor during lamination operation. Operators cause damage (relative to the film coating process, the damage is much smaller) and other issues, solvent evaporation after coating, it is easy to form bubbles on the print surface.

The film coating product has the following features
(1) Foaming and stripping are prone to occur, and blistering and stripping are particularly serious in large-area field printing or in high-humidity working environments.
(2) The surface of the product often produces bright spots or spots of uneven gloss.
(3) The product is prone to curling. If the pressure is too high when gluing or the temperature is too high during drying, this curling phenomenon is more serious.
(4) The chemical substances such as organic solvents will be volatilized into the atmosphere during the coating process, causing environmental pollution and even causing fire.

Pre-coated film products have the following features
(1) Film-coated products using melt-type pre-coated films do not exhibit blistering or release, and have a long product life.
(2) Film-coated products using solvent-evaporating precoating films will also have a relatively thick ink layer, folds, die-cuts, and indentation pressures, or in environments where the temperature of the shop is high. Blistering phenomenon.
(3) Solvent-evolving precoating film can easily adhere to dust and other impurities during production, thereby affecting the surface effect of the film-covered product.
(4) The film product basically does not appear curled.

It can be seen from the above that the precoating film coating process, especially the melted precoating film coating process, has an advantage that the coating film coating process cannot match, and is an inevitable choice for the film coating industry in the future.

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