1, environmental protection and safety
Waterborne varnish uses water as the dispersion medium. It can be diluted with water during the printing process. The equipment can be cleaned with water. It will not produce harmful gases containing aromatics, it will not burn and explode, and production and storage are very safe.
Solvent-based coating oils can be classified into aromatic hydrocarbons and alcohols. Aromatic varnish contains a large amount of benzene harmful substances, it will seriously damage the operator's health during the printing process, and pollute the environment, but also flammable and explosive; while the alcohol varnish is relatively low toxicity, However, there are also flammable and explosive issues. The safety issues in the production process are more prominent.
2, equipment adaptability
The water-based coating oil is mainly composed of a water-soluble resin and a water-dispersed resin. By changing the ratio of the two, the viscosity of the coating oil can be flexibly adjusted. Its characteristics make it possible for aqueous coatings to meet the requirements of almost any printing facility. Waterborne varnish is a volatile drying type, and drying devices such as infrared rays and hot air can be used for the drying of aqueous varnish.
Solvent-based varnish is present in the form of a resin solution with a small range of viscosity adjustment and poor adaptability to equipment.
UV Varnish requires specialized UV curing equipment to be supplied with it.
3, gloss
1) When processing high-gloss products, UV varnish has certain advantages, followed by solvent-based varnish, and waterborne varnish is the worst. The water-based coating has a low gloss, which is due to the slow volatilization rate of the water molecules, which makes the coating film uneven during evaporation of water. On the other hand, it is due to the presence of emulsion resin particles in the water-based coating oil. The surface smoothness of the coating is affected. In order to improve the gloss of the water-based varnishes, the particle size of the emulsion should be reduced as much as possible, and the flatness of the coating film should be increased accordingly. In recent years, with the development of microemulsion polymerization technology, the gloss of water-based coating oils has also been increasing. On the other hand, a small amount of high-boiling solvent can be added to the aqueous coating oil to moisturize the emulsion particles and promote the formation of a coating film with good flatness. After the above improvements, the gloss of the waterborne varnish coating can reach over 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, to make the coating film matt or matte, one method is to add matting agent to the coating oil; the other method is to use two kinds of mutual in the same system. Incompatible resin. In solvent-based varnish, the resin is present as a solution. The two resins that are incompatible with each other cannot exist in the same system. The matting agent can only be used to control the gloss. This is virtually invisible. Increased product costs. In waterborne varnish, the resin exists in the form of an aqueous dispersion, which creates conditions for the presence of two immiscible resins in the same system. By changing the ratio of the two resins, the product can be flexibly adjusted. The luster thus achieves matt or no effect. It can be said that in the field of matt and matt glazing, waterborne varnishes have a unique advantage.
4, waterproof
In the aqueous coating oil system, the water-resistance of the water-based coating oil is once restricted due to the presence of a large amount of carboxyl groups in the water-soluble resin and the hydrophilic property of the emulsifier in the emulsion. In recent years, with the progress of emulsion-free non-dairy polymerization technology and the appearance of functional hydrophobic additives, waterborne varnish has been greatly improved in terms of waterproof performance, and can meet the requirements of general printed materials for waterproof performance.
5, coating product smoothness
Due to the large number of water-based paint slip auxiliaries, the problem of the smoothness of the water-based coating oil has been completely solved, its performance in print smoothness is no less than any solvent products.
6, wear resistance
After the UV varnish is cured, the polymer resin will be crosslinked to form a body network structure, so its wear resistance is better. In solvent varnish, the resin is in the form of a solution. The molecular weight is generally about 10,000, and the wear resistance is the worst. In waterborne varnish, the molecular weight of the emulsion can reach more than 200,000, so its wear resistance is also good. If you add anti-wear additives, its wear resistance can also be greatly improved. Practice has shown that, in the development of wear-resistant polishing oil, the rational choice of anti-wear agent can make the abrasion resistance of the water-based varnishes increase from 20 times to more than 500 times, and the glazing effect is good.
7, high temperature resistance
The resins used in waterborne varnish and solvent varnish are all thermoplastic resins. Due to the softening point of the resin, their heat resistance limit can hardly exceed 150 degrees Celsius. Waterborne two-component resin systems that have just been introduced in recent years are expected to improve the high-temperature performance of water-based coating oils to a higher level, but from the current cost, curing conditions, product stability, and compatibility with other components in coating oils. Considering other aspects, there are certain difficulties in applying it to waterborne varnish. After the UV varnish is cured, its high temperature resistance performance is excellent due to the formation of a macromolecular network structure.
8, production efficiency
The solvent of the water-based coating oil is water. Since the heat of vaporization potential of water is large, the drying speed of the aqueous coating oil is slower than that of the solvent-based product at the same hot air temperature. However, we can solve this problem by moderately increasing the temperature of hot air.