Characteristics of waterborne varnish
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1, environmental protection and safety
Water-based varnish uses water as a dispersion medium. It can be diluted with water during the printing process. The equipment is cleaned with water. It does not produce harmful gases containing aromatic hydrocarbons. It is not easy to burn and explode. It is very safe to produce and store.
Solvent-based varnishes can be classified into aromatic hydrocarbons and alcohols. Aromatic glazing oils contain a large amount of benzene harmful substances, which will seriously damage the operator's health during the printing process, pollute the environment, and be flammable and explosive. The alcohol varnish is relatively less toxic. However, there are also flammable and explosive problems, and the safety problems in the production process are more prominent.
2, equipment adaptability
The water-based glazing oil is mainly composed of a water-soluble resin and a water-dispersible resin, and the ratio of the two is changed, and the viscosity of the glazing oil can be flexibly adjusted. This feature makes water-based varnish suitable for almost all printing equipment. The water-based glazing oil is a volatile drying type, and drying devices such as infrared rays and hot air can be used for drying the aqueous glazing oil.
The solvent-based varnish is in the form of a resin solution, the viscosity is adjustable in a small range, and the adaptability to the device is poor.
UV coatings require special UV curing equipment to match them.
3, gloss
1) UV varnish has certain advantages in processing high-gloss products, solvent-based varnish is second, and water-based varnish is the worst. The gloss of the water-based varnish coating is low, on the one hand, due to the slow evaporation rate of water molecules, the coating film is easily uneven during the evaporation process of water; on the other hand, due to the presence of emulsion resin particles in the aqueous varnish, The surface flatness of the coating film is affected. In order to improve the gloss of the aqueous varnish coating, on the one hand, the particle size of the emulsion should be reduced as much as possible to improve the flatness of the coating film. In recent years, with the development of microemulsion polymerization technology, the gloss of waterborne glazing oil has also been continuously improved. On the other hand, a small amount of a high-boiling solvent can be added to the aqueous varnish to moisturize the emulsion particles to form a coating film having a good flatness. Through the above improvements, the gloss of the waterborne varnish coating can reach more than 90%, which is close to the coating gloss level of the UV varnish, which can meet the requirements of general high gloss products.
2) In the field of matt and matt products, one way to achieve a matt or matt effect of the coating is to add a matting agent to the coating; another method is to use two in the same system. Incompatible resin. In solvent-based varnish, the resin exists in the form of a solution, and the two resins that are incompatible with each other cannot exist in the same system, and only the method of adding a matting agent can be used to achieve the purpose of controlling gloss, which is invisible It increases the cost of the product. In aqueous varnish, the resin exists in the form of an aqueous dispersion, which creates conditions for the presence of two mutually incompatible resins in the same system. By changing the ratio of the two resins, the product can be flexibly adjusted. Gloss, thus achieving matt or no effect. It can be said that in the field of matt and matt glazing, water-based glazing oil has a unique advantage.
4, waterproof
In the aqueous varnish system, the water repellency of the aqueous varnish was once restricted due to the presence of a large amount of carboxyl groups in the water-soluble resin and the hydrophilic properties of the emulsifier in the emulsion. In recent years, with the advancement of emulsion emulsion-free polymerization technology and the emergence of functional hydrophobic additives, water-based glazing oil has been greatly improved in waterproof performance, which can meet the requirements of waterproof performance of general printed matter.
5, glazing product smoothness
Due to the large number of water-based paints and smoothing additives, the problem of smoothness of water-based glazing oil has been completely solved, and its performance in terms of print smoothness is no less than that of any solvent-based products.
6, wear resistance
After the UV varnish is cured, the polymer resin will crosslink to form a network structure, so the wear resistance is good. In the solvent-based varnish, the resin exists in the form of a solution, and the molecular weight is generally about 10,000, and the wear resistance is the worst. In the waterborne varnish, the molecular weight of the emulsion can reach more than 200,000, so the wear resistance is also good. If anti-wear additives are added, the wear resistance can be greatly improved. Practice has shown that in the development of wear-resistant varnish, the reasonable selection of anti-wear agent can increase the wear resistance of water-based varnish coating from about 20 times to more than 500 times, and the glazing effect is good.
7, high temperature resistance
The resins used in water-based varnishes and solvent-based varnishes are all thermoplastic resins. Due to the softening point of the resin, their heat resistance limits are difficult to break through 150 degrees Celsius. The water-based two-component resin system that has just been introduced in recent years is expected to improve the high temperature resistance of waterborne varnish to a higher level, but from the current cost, curing conditions, product stability and compatibility with other components in the varnish. In other respects, it has certain difficulties in applying to waterborne varnish. After the UV coating is cured, its high temperature resistance is excellent due to the formation of a macromolecular network structure.
8, production efficiency
The solvent of the aqueous glazing oil is water. Since the vaporization potential of water is relatively high, the drying speed of the aqueous glazing oil is slower than that of the solvent type product at the same hot air temperature. But we can solve this problem by moderately increasing the hot air temperature.