Detailed description of film packaging process for goods (I)

The role of commodity packaging in modern marketing is increasingly valued by commodity manufacturers. At present, commodity packaging methods are diversified, and the packaging process is also complicated. Here, I will discuss my opinion on the application of the film coating technology in the field of commodity packaging and discuss it with everyone.

Laminated film is the plastic film coated with adhesive, and the paper prints are heated and pressed together to form a paper-plastic product. It is one of the common post-printing processes for paper-based prints. After the film-covered prints have a thin and transparent plastic film on the surface, the surface is smoother and brighter. This not only improves the glossiness and fastness of the prints, but also prolongs the service life of the prints. At the same time, the plastic film is waterproof. Anti-fouling, wear-resisting, folding-resistant, chemical-resistant and other protective effects. If the film is covered with a transparent light film, the printed images of the film products are more vivid in color and more three-dimensional, which is particularly suitable for the packaging of products such as green foods, which can cause people's desire for appetite and consumption. If a matte film coating is used, the covered product will give the consumer a noble and elegant feeling. Therefore, the packaged printed product can significantly improve the grade and added value of product packaging. At present, common film-covered packaging products include cartons, cartons, handbags, fertilizer bags, seed bags, self-adhesive labels, and so on.

Film coating process classification

According to the different raw materials and equipment used, the coating process can be divided into coating film coating process and pre-coating film coating process. That is, the film used in the film coating process is currently coated. The used adhesives are generally of solvent type and emulsion type, and are used with the use. The film used for the precoating film coating process is pre-coated, and the adhesive used is generally of the hot melt type and the solvent-evaporation type.
According to the process of coating a paper print, the coating process can be divided into three categories: dry coating, wet coating, and pre-coating. The dry film coating method is currently the most commonly used film coating method in China. It is applied with a layer of adhesive on a plastic film, and then it is dried in a dry drying tunnel of a film laminator to remove the solvent from the adhesive, and then heated. Press-bonded paper products with paper products.

In the wet coating method, a layer of adhesive is coated on the surface of the plastic film, and under the condition that the adhesive is not dry, the film is adhered by a pressure roller and a paper print. Since the advent of the water laminating machine, the water-based laminating process has been popularized and applied. This has the advantages of simple operation, small amount of adhesive, and no organic solvent that destroys the environment. The lamination film has high strength, High grade, easy recycling and other characteristics are inseparable. At present, the coating process is increasingly favored by domestic packaging manufacturers and has been widely used in packaging such as gift boxes and handbags.

The pre-coating film method is a direct purchase of a plastic film coated with a binder by a film factory. When the film needs to be coated, the film is hot-pressed on the film-coating equipment together with the paper print to complete the film coating process. The pre-coating process began in the 1990s, and the hot-melt adhesive or low-temperature resin was uniformly coated on the film substrate by a special device. The pre-coated film was obtained. The pre-coating method eliminates the preparation, coating, and drying of adhesives. The entire coating process can be completed in a few seconds. No pollution to the environment, no fire hazard, and no need for cleaning. Plastic equipment and so on. At present, the process has been used in medicine, food packaging.

Film quality requirements

The plastic films commonly used in the film-covering process include polyvinyl chloride (PVC), polypropylene (PP) and polyester (PET) films. In order to comply with the requirements for the use of laminated prints, plastic films should meet the following requirements.

(1) The film thickness is between 0.01 and 0.02mm. After corona treatment or other methods, the surface tension should reach 4.0×10-2N/m, so as to have better wetting performance and adhesion performance.
(2) The treatment effect of the film corona treatment surface should be uniform and the transparency should be as high as possible in order to ensure the best clarity of the printed matter.
(3) The film should have good light fastness, and it is not easy to change color when light is irradiated for a long time, and the geometric dimensions remain stable.
(4) The film should have a certain degree of chemical stability because the film should be in contact with solvents, adhesives, inks, and other chemical substances.
(5) The appearance of the film should be smooth, free from unevenness and wrinkles, and free of bubbles, shrinkage holes, pinholes and pits.

Pre-painted film structure characteristics

The precoating film consists of a substrate and a binder layer. The substrate is usually a polyester (PET) film and a biaxially oriented polypropylene (BOPP) film. BOPP film has the characteristics of high transparency, good lightness, non-toxic, tasteless, water-resistant, heat-resistant, inexpensive and soft texture. It is an ideal material for the film coating process. Its thickness is 12 to 20 μm, and the thickness of the imported film is only About 10 μm, therefore, from the perspective of material cost and processing technology, most of the pre-coated film substrates use BOPP film.

The adhesive layer of the precoat film has two kinds of melting type and solvent evaporation type. According to different processing equipment and process conditions, people often use adhesive layers with different thicknesses. The thickness of the adhesive layer is generally between 5 and 15 μm. 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 the coating film coating process, ie, the organic solvent is used to dissolve the colloid and then coated on the film substrate, so there may be incomplete volatilization of the organic solvent and abnormal odor during the film coating operation. Injury to the operator (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 surface of the print.

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