On the water-based coating technology of printed m

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As we all know, printing film covering is one of the surface finishing processing technologies of printing and an auxiliary process of printing. It is to bond the plastic film with the printing through adhesive to improve the gloss, strength and aesthetic effect of the printing surface, make it water-resistant and wear-resistant, and it is an effective means to improve the grade and commodity value of printing. Therefore, to measure the quality of film coating, we mainly examine the brightness, strength and adhesion of products

for the film covering process, it mainly adopts two kinds of materials: film and adhesive. The films used for film coating mainly include bidirectional drawing propylene film (BOPP), polyvinyl chloride (PVC), etc., among which BOPP film is the most widely used. The adhesive used in film coating can be divided into oily film coating adhesive and water-soluble film coating adhesive. For water-based glue, EVA resin (ethylene vinyl acetate copolymer resin) and acrylic resin are most commonly used in production; In terms of its chemical structure, there are single component and two-component

since the development of water-based film coating machine in the 1990s, the water-based film coating process has been vigorously promoted and applied. The water-based film coating is favored by the majority of customers because of its high brightness, high grade, easy recovery and no pollution. Since its establishment in 1995, Hengtai color printing company has produced many water-based coated products, such as wine boxes, wine boxes, wine labels, handbags, posters and so on. We have also accumulated some experience in the process of water-based film coating. Here, we will discuss with you through the following aspects:

① printing powder spraying

because the water-based glue can dissolve the powder spraying on the surface of printing products, it is incomprehensible when there are snowflakes on the film coated products. In fact, the reason is very simple, and the water-based glue itself will be limited by the solubility. When the powder spraying amount of the printed matter is greater than the dissolving capacity of the glue, the excess part cannot be dissolved or covered by the glue, and a large number of snowflakes will appear. In this case, there are the following solutions:

first, coordinate the upper and lower processes to minimize the powder spraying amount during printing. In our company, there are two types of machines, Roland and Heidelberg. Because the powder spraying device and mechanism are different, for the same product, Roland computer machine should spray powder more evenly and better controlled than Heidelberg machine

II. When laminating, appropriately increase the amount of glue and increase the ability of glue to dissolve and spray powder. In actual production, the maximum amount of glue hanging is when the edge of the product does not overflow

III. spray powder on the surface of the printed matter before coating. You can wipe the surface manually or set other powder removal devices on the machine

② cleaning

due to the rapid drying of water-based film coating adhesive, if it is still and does not flow and exposed to the air for too long, it will dry and crust and attach to the glue coating roller or pressure roller, resulting in local failure to apply glue or too thin adhesive layer and local pressure increase. Therefore, it is necessary to keep the glue coating roller and pressure roller clean during the film coating process, but with the enhancement of environmental protection awareness, There is too much dust in the surrounding environment or there are dry rubber and cut film fragments in the glue, which will also affect the quality of the film coating. Therefore, we must pay attention to cleanliness, pay attention to the storage of the glue, and add the glue filter device in the actual and production process

③ paper plastic separation

paper plastic separation is easy to occur in products with large printing area and large field. Due to the thick ink layer on the surface, the glue is difficult to wet, diffuse and penetrate, so the bonding is not firm. The solutions are as follows:

first, check the production date and shelf life of the glue to see whether the glue has deteriorated

II. Whether the film is within the shelf life and what is the surface corona value

III. refer to the technical indicators of glue and whether it is operated correctly according to the regulations in actual production

IV. replace other brands of glue with high viscosity value

v. improve the environmental humidity during film coating and product drying

④ deformation

there are the following reasons for the deformation of Chinalco Northeast Light Alloy Co., Ltd. taking this opportunity:

first, the amount of glue is too large, and the paper absorbs water and deforms. Therefore, under the premise of ensuring product quality, it is understood that the amount of glue should be reduced as far as possible

II. The film has serious tensile deformation. At this time, the elastic tension of the film should be adjusted appropriately. Under the condition of ensuring that the film fits smoothly with the paper, the smaller the tension, the better

III. the winding tension is too large. At this time, according to the situation, the smaller the tightening force is, the better when ensuring that the product is transferred to the winding roller

IV. the temperature and humidity of the external environment where the product is located vary greatly

generally speaking, with the rapid development of the printing and packaging industry, the continuous innovation of technology and the continuous emergence and replacement of new materials, we will also face new problems and challenges. Hengtai color printing will also keep up with the pace of the times and seek higher development

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