1. The influence of polymer monomers on the glossiness of water-based Overprint Varnishes

The polymer monomers selected for the film-forming resin in the water-based varnish formulation have a significant impact on the glossiness of the finished product. In actual production, multiple monomers are usually used for copolymerization. The acrylic resin used in water-based varnish can be made from monomers such as methyl methacrylate, styrene, acrylic methyl ester, acrylic β-hydroxypropyl ester, and acrylic. Increasing the dosage of methyl methacrylate and styrene leads to a harder coating with good glossiness, but it is also more brittle and has poorer flexibility and solubility resistance.

2. The proportion of water-soluble resins and emulsions in the varnish formula

Increasing the dosage of emulsions can enhance the glossiness of the varnish, but it will reduce the leveling and processing suitability of the varnish; increasing the dosage of water-soluble resins can improve the leveling and processing suitability of the varnish, but the glossiness will decrease.

3. The influence of leveling on the glossiness of water-based varnish

Leveling is an important factor affecting the glossiness of water-based varnish. Leveling is influenced by product viscosity, pH value, and surface tension. Choosing an appropriate leveling agent can effectively improve the construction leveling performance. If the varnish has good leveling, it can quickly level before the coating dries, forming a smooth surface, and the coating will have high glossiness; if the varnish does not dry before leveling, it will leave some streaks, sand holes, etc., reducing the glossiness.

4. The influence of pH value on glossiness

The pH value of water-based varnish should generally be controlled between 8 and 9. The pH value is mainly adjusted with ammonia water. If the pH value is too high, the viscosity of the varnish will decrease, affecting the glossiness and causing a slower drying speed and poorer water resistance; if the pH value is too low, the viscosity will increase, and ammonia water will volatilize relatively quickly during leveling, causing the leveling process to end prematurely and affecting the final film formation glossiness.

5. The influence of viscosity and solid content of the finished product on glossiness

The viscosity of the finished product has an important impact on the leveling, wetting, and other properties during coating application. The surface of the printed product has a certain absorption capacity for the varnish, and the absorption rate of the printed surface for the varnish is proportional to the viscosity value of the varnish. If the viscosity value of the varnish is too small, when coating on paper with a high absorption rate, it will cause too large a change in the viscosity of the varnish during leveling, resulting in premature ending of leveling, causing uneven coating on the surface of the printed product, and affecting the smoothness and glossiness of the film layer after drying and calendering; if the coating is applied to printed products with a low absorption rate, a too low construction viscosity will cause runny phenomenon, resulting in uneven coating, poor drying, and other problems.

The solid content of water-based varnish should generally be controlled at 30-40%. The solid content of water-based varnish has a significant impact on glossiness, and the influence of solid content on the glossiness after film formation is similar to the influence of viscosity.

6. The influence of surface tension of the finished product on water-based varnish

The surface tension of the varnish not only affects glossiness, but is also an important factor affecting the overall quality of the varnish. The size of the surface tension of the varnish has a significant difference in the wetting, adhesion, and penetration effects on the same printed product, and the coating effect after coating and calendering is also very different.