With the enhancement of people's awareness of environmental protection and the introduction of relevant environmental laws and regulations, water-based varnish has been gradually applied in the packaging of electronic products, daily necessities, cosmetics, medicine, cigarettes, etc. due to its environmental protection and low price. In this article, the author will introduce the characteristics and application of water-based varnish in detail for the reference of the industry.
Characteristics of water-based varnish
Advantage
Waterborne varnish has the following advantages over ordinary varnish.
(1) Environmentally friendly and non-toxic
The main component of water-based varnish is aqueous emulsion, which does not contain VOCs. Although it is often used to adjust the drying speed by adding a small amount of ethanol, it does not harm the health of the operator and is therefore a green product.
(2) Film formation speed is fast
The drying method of water-based varnish on paper surface is mainly osmotic drying and volatile drying, while the drying method on the surface of non-hygroscopic substrate is mainly volatile drying, but because water varnish has the characteristics of emulsion, when the moisture content is about 30% The film can be closed at the time, so there is no need to dry or produce quality problems such as stickiness. If it is dried by infrared or hot air, the drying effect is better.
(3) Good printability
The solvent-based resin of ordinary varnish exists in the form of a solution, the viscosity is relatively stable, the adjustable range is small, and the adaptability to the device is poor, and the UV varnish requires special UV curing equipment to match it. In contrast, water-based varnish is mainly composed of water-soluble resin and water-dispersible emulsion. As long as the ratio of the two is changed, the viscosity can be flexibly adjusted. This feature makes the aqueous varnish almost adaptable to all. Printing equipment .
2. insufficient
Of course, water-based varnish also has many shortcomings.
(1) Low gloss
In general, OPP film and UV glazing products can achieve a gloss of 80 or higher. In contrast, the gloss of waterborne varnish glazing products is generally low, generally between 55 and 75.
(2) Poor water resistance
The water-based varnish is mainly composed of two soft and hard water-based acrylic emulsions with different Tg values ​​and a solid styrene-acrylic resin alkali solution. There are a large number of hydrophilic carboxyl groups and hydrophilic emulsifiers in the system, which makes the water-based varnish poor in water repellency. . In recent years, with the implementation of emulsion emulsion-free polymerization technology and the emergence of reactive emulsifiers, the water repellency of water-based varnish has been greatly improved, which can meet the requirements of general printed matter for water repellency.
(3) Poor explosion-proof edge
In order to improve the wear resistance and anti-sticking property of water-based varnish, a large amount of hard emulsion is often added during the preparation process, so that the prepared aqueous varnish is obviously hard and brittle after film formation, resulting in the printed product after glazing The "burst" phenomenon is likely to occur in the subsequent die cutting process.
Waterborne varnish purchase
Due to the different production processes and technical levels of various manufacturers, the quality of water-based varnish is not the same. Pay attention to the following items when purchasing.
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