There are three types of coatings: oily, water-based and hot-pressed pre-coating (dry). The production process of oily and hot-pressed (dry) coatings is contaminated. It is a production process that has been gradually eliminated. Water-based coatings are both economical. Affordability is already a popular domestic production method of laminating.
The process of water-based coating is as follows: paper feeding in the paper feeding department—paper feeding at the paper table—adhesive coating on the film—printing film coating—winding—hanging and drying—slitting—flat setting. The plastic film used for water-based film is basically the same as the traditional oil-based film, mainly polypropylene film, but also PVC film, polyethylene film, polyester film, etc. The corona treatment of the film requires less. The storage time after coating is long, and the oily, hot-pressed (dry) coating requires high corona treatment of the film. The adhesive is also called water-based glue. The proportion of main raw materials is approximately: vinyl acetate · ethylene polymerization emulsion (VAE) 75% -85%, rosin 3% -5%, emulsifier 3% -5%, water 5% -10%, other additives 1% -2 %. The water-based film does not need to be heated and dried, and is directly wound up. The speed reaches 70-80 meters per minute, which is 2 to 3 times that of other film production methods.
The water-based coating process uses water-based environmentally friendly glue, does not require a heating and drying device, high speed energy saving and high gloss, because of its characteristics also have some shortcomings, it should be used with caution in some products. The water-based film glue that is not suitable for large-area graphic products contains a certain amount of water. When used in large-area (especially large-field film) graphic products, a large area of ​​snowflakes appears on the surface of the graphic. The spots affect the appearance quality of the product, and the increase in the amount of sizing is not much improved. Only oily or hot-pressed pre-coating processes can be used instead of construction.
Due to customer requirements, some products require double-sided lamination. If the water-based lamination process is used, the water content in the glue is large, which makes it difficult for the printed product to evaporate after a short period of time. This makes the printed product soft and fails to meet the customer's requirements. , A quality accident occurred. Concavo-convex processing is not easy to be processed within 3 to 5 days after coating. Because the water-based adhesive in the water-based coating contains water, sometimes it is difficult to completely dry in 3 to 5 days after coating. If the product is pressed and processed, it will stick on its contact surface. Problems such as looseness and blistering are most prominent on coated paper. For example, in some handbags, the indentation bar line after water-based coating is not very straight, and sometimes it will whitish and foam, which affects the appearance of the product. Subsequent processing waits, the preparation time is too long, the water-based coated product is laid flat for 24 to 48 hours after large-scale splitting, and sometimes it can be flowed into the next step of construction after baking at 35 to 40 ℃. The purpose is to glue its Water evaporates, stabilizes the adhesive strength and the stiffness of the film-covered products, so that subsequent processing can be carried out, and sometimes some special measures have to be taken to meet the requirements.
The discoloration of printed graphics and text mainly occurs on the large area of ​​spot color printed products, such as gold and silver ink products, the color will change after the water-based coating, due to some chemicals in the glue and water and gold ink (containing copper There is more powder) or silver ink (more aluminum powder is contained) due to chemical reaction. At this time, only oily or hot press pre-coating process can be used.
Water-based coating products have their unique features:
â‘ The cover for saddle stitching, especially the thin cover, will not curl due to moisture;
â‘¡ The production suitability requirements are not high, suitable for mass production lines;
â‘¢ The input price cost is not high, and the comprehensive cost is low;
â‘£It is not easy to pollute the environment, it is an environmentally friendly product, and it also represents the development direction of the film.
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