UV coating application

In order to adapt to environmental protection requirements, the technology of surface gloss treatment of paper packaging products is gradually being developed toward ultraviolet curing (UV). Since the UV coating technology does not use solvents, there is no air pollution caused by solvent evaporation. At the same time, UV varnishing technology has a simple technological process, fast curing speed, low energy consumption, and can make the decorative surface of paper packaging products have good abrasion resistance, finger resistance and high light depth, and is increasingly affected by food and medicine. The importance of tobacco companies.

I. Composition of UV Varnish

UV varnish consists mainly of oligomers, reactive diluents, photoinitiators and other additives. Oligomers are the most basic components of UV varnish, and their properties play a decisive role in the curing process and curing quality. At present, commonly used oligomers include epoxy acrylates, urethane acrylates, and polyester acrylates. Among them, epoxy acrylates have the characteristics of fast curing, good adhesion, and low price, and are the most widely used oligomers.

Reactive diluents are used to adjust the UV coating viscosity, cure speed, and cured film properties. Most of the current use is acrylic monomers. According to the number of acrylic groups contained, they can be divided into monofunctional diluents and polyfunctional diluents.

UV varnishes commonly used additives are stabilizers, leveling agents, defoamers and so on.

Second, UV coating process

UV coating process is generally: In addition to powder - corona treatment - base oil UV glazing - cooling. There are many factors that affect its process, such as: the glazing adaptability of inks, prints, the selection of relevant conditions in the process (coating amount, drying temperature, and coating speed, etc.), and the influence of external environmental conditions.

The wetting of the ink layer, its particle size, and the drying of the ink layer directly affect the coating quality and rheology of the coating. The smoothness and absorbency of the paper have a significant effect on the quality of the coating. In the same conditions as other factors, the higher the smoothness of the paper, the better the glazing effect; vice versa, the local dents are likely to occur. In order to obtain a high-smoothness paper, a primer layer is often applied before coating. Different papers have different absorption of varnish. Absorption is too strong, it will make it difficult to form a smoother film coating oil, easy to appear similar to the paper surface roughness of the film layer. Absorption is too weak, and the penetration, coagulation, and conjunctival action in the leveling can be significantly reduced. Likewise, a high-quality film layer cannot be formed. So choose the appropriate absorption.

Third, the main way of UV polishing

(1) According to the relationship between polishing machine and printing machine can be divided into: offline and online coating.

(2) According to the glazing method can be divided into: roller coating and printing on-line coating.

(3) According to the type of glazing products can be divided into: full-format UV, partial UV, matt UV and artistic glazing and so on.

IV. Application of UV Polishing Technology

After the UV coating treatment of paper packaging products, the appearance effect can be improved, the printing quality is thick and full, the luster is full and nourishing, the decorating effect of the paper products is improved, and the folding resistance and chemical resistance are significantly improved, and the use performance thereof is improved. , To reduce the loss of products during transportation and storage. For products with high moisture-proof requirements (such as electrical appliances, etc.), their paper-based packaging products are treated with UV coating to increase the moisture resistance of the package.

UV glazing has developed rapidly in recent years, and its proportion in the packaging and printing industry is gradually increasing, but at the same time there are still many problems to be solved. The first is security issues. At present, reactive diluents used in UV varnish have certain volatility or irritation and are still polluted to the environment. The water-based UV varnish currently being developed is an ideal environment-friendly product because it replaces the active diluent with a thickener, which solves the problems of volatility and irritation.

Followed by the odor problem. Now it is gradually developing towards low odor. At present, UV-glazed packaging products have not been fully recognized by the international food and drug companies and cannot be directly contacted with food. Therefore, it is necessary to improve the working conditions and environment, improve the drying effect, and obtain a complete cure, thereby reducing the odor.

Again, there is a problem of adhesion on oxidative polymerization inks. There is not only the problem of odor, low gloss, but also difficulty in adhesive attachment. Double glossing is often used to improve the quality of UV coatings, but it also increases costs. Therefore, the adaptability of UV light oil and ink needs to be improved.

The last is to reduce the cost, although the current cost has dropped a lot, compared with the cost of BOPP composite film composite cheaper. However, in China, there are many types of UV coatings and their properties are different. So the price difference is greater. In general, the cost is still too high, and it is necessary to further reduce the cost of lacquer, coating costs, and equipment operating costs.