That is, the characteristics of coating film and precoat film coating product

That is, 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 a melt-type precoating film do not exhibit blistering and release, and have a long product life.

(2) Film-coated products using solvent-evaporating precoating films will also have a relatively thick ink layer, where folding, die-cutting, and indentation pressures are relatively high, 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.

Influencing Factors of Film Quality of Packaging Products

There are many factors that affect the quality of the packaging film products, including the following aspects.

(1) The printing materials have a great influence on the quality of the coating film. The paper packaging materials are mostly whiteboard paper, paperboard, etc. If the surface is clean and smooth, the thickness is uniform, and the folding strength is high, the film coating effect is ideal.

(2) The effect of ink on the quality of the coating film is also very obvious. If the printed ink layer is thick or the printed graphic area is large, the ink will close the pores of the paper fibers and hinder the penetration and diffusion of the adhesive, making it difficult for the printed matter and the plastic film to be bonded, and defects such as release and blistering will occur easily. If the film is not fully dried when the ink is completely dried, the high-boiling solvent contained in the ink can easily cause the plastic film to expand and elongate. After the film is covered, blistering and release occur.

(3) The printing process also affects the quality of the coating. In the packaging printing, a variety of printing processes are often used. In general, the ink layers of flexographic printing, gravure printing, and screen printing are relatively thick, and the ink layer of the offset printing ink is the thinnest. Therefore, compared with other printing materials, Offset products are best suited for laminating operations. In addition, gold and silver ink printing processes are usually involved in the field of packaging and printing, but gold and silver ink printing products are not suitable for the coating process because metal powders have poor uniformity and adhesion in the binder and dry in the ink layer. The process is easily separated. If a laminating process is used, these separated metal powders form a barrier between the ink layer and the adhesive layer, affecting the effective bonding of the two interfaces. Moreover, wrinkles, foaming, etc. may occur after the product is left for a period of time.

(4) Influence of environmental temperature and humidity on coating quality. The increase in temperature can soften the film and cause the paper to adhere to the plastic film. However, if the temperature is too high, the film is easily broken. Moreover, the internal stress formed by the heat shrinkage of the film may cause the film product to curl, wrinkle, and not adhere well. The change of the moisture content of the printed matter (absorbing moisture from the air medium or releasing moisture into the air medium) occurs at the edge of the printed matter, and it is not easy to form a good bond with the film in the hot press composite to cause wrinkles, which affects the smooth progress of production. .

The difficulties faced by the packaging and filming process

With the improvement of people’s quality of life, people’s awareness of environmental protection is also increasing. Over the years, the laminating process has also undergone qualitative changes. “Non-toxic, harmless, and green” has become an inevitable trend in the development of the lamination process. However, the current coating technology is being criticized by various parties.

First, there is a source of pollution in the filming process. Due to the extensive use of solvent-based coating technology in China, there are a large amount of benzene and alcohol chemical substances in solvent-based film adhesives and their diluents, which have strong volatility and toxicity and can cause harm to the health of operators. In addition, such organic chemicals are flammable, and are flammable in the event of an open flame or strong light, which is a great hidden danger in the production of fires.

Second, the film-covered product itself is a source of pollution. Since the benzenes and alcohols in the film adhesives and their diluents cannot completely volatilize during the film coating process and in a short period of time after the products are molded, it is possible for the residual substances to be delivered to the consumers along with the products. The odor and toxicity of these residual substances have to some extent contaminated the consumer's living environment and threaten the health of consumers. If the contents of the package are smoke, alcohol, or food, the hazard is even greater.

Third, packaging waste is the third source of pollution. Current technology cannot yet easily recycle coated paper.

Fourth, if the printed matter is coated on one side, it will easily cause warpage of the packaging products; if the double-sided coating is used, it will bring difficulties to the cutting of the subsequent processes.

Fifth, because the tension of the film is proportional to the speed of the machine, the speed of the machine is limited when the film is covered. Compared with the glazing process, the production efficiency is reduced, and the cost is increased accordingly.

Therefore, the current market for packaging film lamination products is being eroded by the glazing process. Given that the water-based glazing process and the UV glazing process can also increase the surface glossiness of printed products, improve the stiffness of the printed products, and have no pollution, packaging waste can be recycled. Reusing or self-decomposing features, more and more packaging and printing companies have adopted the glazing process.

Opportunities for Packaging Laminating Technology

The ancients said that "there is nothing but Xiao Xiao," and the development of modern technology brings crisis to the packaging and filming industry, and it also brings opportunities. At present, a fully-automated water-based laminator can be purchased on the domestic market. The operation of this machine is completely automated, which reduces man-machine contact time and reduces the contact time between the operator and the pollution source. At the same time, the market is also vigorously promoting the use of non-toxic, harmless, green and environmentally friendly adhesives. These technological advances have brought new springs to the packaging and lamination process.

Although the glazing process is a strong competitor for the lamination process, in some cases, the lamination process cannot be replaced by the glazing process. For example, laminating products can significantly increase the strength of printed products. Products are crucial. In addition, film-covered products can improve the waterproof performance of prints and are of great significance for product packaging involving long-distance transportation. Film-covered labels are also more prominent in dimensionality than glossy prints.

In short, for the laminating process, we must use a dialectical perspective, we must not only see its advantages, but also must face up to the current facts, consolidate the existing market share, and increase investment in scientific research, with the help of scientific and technological forces to solve the film The destruction of the environment will recapture the lost market.

Source "Printing Technology"

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