Effect of Hanging Agents and Leveling Agents on Ink Properties (Part 2)

There are also treated ultrafine calcium carbonate (most of the particle size is 2llm' 601xm, the surface is treated with fatty acids and resins, etc.) used for long oil alkyd inks, vinyl printing inks, the amount is too large, often affect the ink Water resistance of the membrane.

The organic system is swell-dispersed in the ink to form a network structure, giving the structural viscosity of the printing ink, making it thixotropic. In recent years, this type of additive is slightly smaller than the scope of application of inorganic type B organic additive has little effect on the performance of printing ink, has a good anti-subsidence, and can maintain a good storage stability of the ink. However, depending on the type of binder and the operating temperature of the ink system, the effect and stability will not be the same. For example, castor oil derivatives are often divided into two major categories: aliphatic and aromatic solvent inks and aliphatic oils. Coupled with the different manufacturers of the brand, the use of temperature is not the same. Its greatest feature is that if the temperature is too high, the additive dissolves and the operation can be stopped to allow the swelled particles to precipitate. After heating under shear to the desired temperature, it can be restored to a fully activated state, and a stable ink thixotropic agent can still be prepared.

Organically modified bentonite (containing more than 85% montmorillonite, with high-quality clay for various purposes), it is a layered clay with 2:1, the upper and lower layers are silica tetrahedron, and the middle layer is octahedron. Aluminum or magnesium is coordinated with six oxygen atoms or hydrogen and oxygen radicals. The hydrogen bond structure is easily destroyed, resulting in a drop in viscosity; when the shear is removed, the hydrogen bond is restored and the viscosity is increased again. This is the basic principle that the organically modified bentonite can make the printing ink form a thixotropic fluid, and the bentonite has an anti-sinking effect. The reason for the effect. BENTONESD-1 on the market is a type that does not require polar activators, and does not need to be made into a gel. It only needs proper stirring and shear force. It can be directly added to the printing ink on the line. (Of course, the gelling is added directly to the dry powder. The effect is much better.)

Metal soaps, which are organic thixotropes, have a large swelling gelling ability and exhibit a thickening effect even at a relatively low temperature. In non-polar solvents, metal soap thixotropes can form micelles due to coordination bonds. These micelles can form a network structure, resulting in an increase in the viscosity of the ink. However, one common disadvantage of these thixotropic agents is that the temperature and the solvent are different, and the swelling effect is different; the resulting gel structure is unstable. Especially when water and a polar solvent are mixed in, precipitation or precipitation of particles tends to occur. The advantage of this additive is that it can be used under weak shear force and temperatures of 40°C-60°C.

To prevent poor scrapping of packaging and printing products, not only anti-settling and anti-sagging auxiliaries should be added, but also necessary leveling aids should be added to prevent the ink from shrinking, pinholes, bubbles, floating color, and white when printing. Frost failure.

Printing ink leveling agent

Auxiliary leveling agents for improving the leveling of the printing ink film (increasing the gloss and improving the film and composite flatness). After different printing inks are printed by different printing methods, there is a flow and dry film formation process, and finally a smooth, uniform ink film is gradually formed. Whether the printing ink film can achieve smooth and smooth characteristics is called leveling. In the actual packaging and printing process, we often have poor leveling properties, such as scratches, orange peel, and water marks during printing. Condensation, shrinkage, pinholes, and other phenomena that accompany the drying process are called poor leveling. These failures are related to the quality of the printing ink, the printing environment and the process. The general leveling agents are solvents and mixtures thereof, such as high-boiling aromatics, esters, ketones, and ether alcohols, which have excellent dissolving power, or a silicone resin that is miscible with the ink, such as a polyurethane ink. Wait. Because its components do not use solvent or use less solvent, it is easier to produce faults with poor leveling. Therefore, polymer-type leveling agents such as cellulose acetate monobutyrate and polyacrylic acid are often used to improve ink performance. Its purpose is to reduce the viscosity of the ink and improve the leveling of the ink film.

The addition of leveling agents tends to produce sagging as the flow increases, so an optimal range should be found between adjusting the sagging and leveling; the use of leveling agents will reduce the solid content of the ink, which is in line with today's development. The development trend of high solids inks that can save energy and reduce pollution is not consistent. Therefore, the use of the additive, the design of mixed solvent-based inks, the appropriate amount of coupling agent to form a gradient, is a major trend in today's ink formulations. This not only overcomes the reduction of solids content, but also avoids the defect of dry film formation when a portion of slow-drying solvent with low volatility flows. For example, the author has designed the PET gravure thick ink for the Buddha Ishan City Shunde Yingpeng Plastics Co., Ltd., which can reach 50um after a one-time printing and drying to form a new attempt to save energy.

Whether Germany's BYKETOL-OK, or domestic SF-723 leveling agent, are solvent-based, basically all have to prevent bubbles, pinholes, shrinkage, improve leveling, and increase the role of adhesion. According to the author's knowledge, in the past, it was very difficult to increase the leveling property of ink by increasing the surface tension of the ink, but the actual one was just the opposite.

The role of induction leveling agent is to: reduce the interfacial tension between the ink and the substrate, improve the wettability of the ink on the substrate, and reduce the phenomenon of shrinkage, poor adhesion and other failure phenomena caused by the substrate. In addition, it has the property of migrating to the surface of the ink film, which can form a monolayer on the surface of the ink film, lower the surface tension, and balance the surface tension, thereby reducing various surfaces and surfaces due to surface tension gradients. Fault phenomenon. The third is to adjust the volatilization rate of the solvent in the ink, especially to design the gradient balance of the mixed solvent in the system.

Author/Liu Jiaju Source: China Packaging News