Guide to the use of water-based ink leveling agent: make the printing effect better
Today, when the concept of environmental protection is deeply rooted in people's hearts, water-based ink has gradually
become the mainstream choice in the printing industry with its low VOC (volatile organic compound) emission characteristics.
However, water-based ink is prone to poor leveling problems during use, such as shrinkage, orange peel, brush marks, etc.,
which will seriously affect the quality and aesthetics of printed products. As a key auxiliary agent to solve this problem, the
correct use of water-based ink leveling agent can significantly improve the leveling performance of ink and enhance the printing
effect.
1. Understand the working principle of water-based ink leveling agent
The core function of water-based ink leveling agent is to reduce the surface tension of ink, improve the wettability and fluidity of
ink on the surface of substrate, so that the ink can be evenly spread during the drying process to form a flat and smooth ink film.
When the ink is applied to the surface of the substrate, the leveling agent molecules will quickly migrate to the surface of the ink,
reduce the surface tension, reduce the interfacial tension between the ink and the substrate, so that the ink can better wet the
substrate and avoid defects such as shrinkage. At the same time, the leveling agent can also inhibit the convection caused by solvent
volatilization and surface tension changes in the ink during the drying process, prevent the formation of unevenness such as orange
peel and brush marks, and finally achieve a good leveling effect.
Different types of leveling agents have slightly different mechanisms of action. For example, polyether-modified polysiloxane
leveling agents can not only effectively reduce surface tension, but also have a certain defoaming function, which can eliminate
bubbles generated by stirring and pumping during the ink coating process; acrylic leveling agents mainly adjust the rheological
properties of inks to improve the flow and leveling of inks, and perform well in some printing scenes with high requirements for
recoating.
2. Choose the right leveling agent according to actual needs
(I) Consider the material of the substrate
Different substrates have different surface characteristics, and the requirements for water-based ink leveling agents are also different.
For example, plastic substrates (such as PET, PP, etc.) have low surface energy, and it is difficult for ink to wet and level on their surfaces.
At this time, polysiloxane leveling agents with strong surface tension reduction capabilities should be selected. Such leveling agents can
significantly improve the wettability of ink and plastic surfaces and prevent the formation of shrinkage holes; for paper substrates, since
the paper surface has certain pores and roughness, acrylic leveling agents are more suitable. They can adjust the rheological properties
of inks, so that the ink can better fill the pores of the paper and obtain a smooth printing surface.
(II) Combined with printing process
Different printing processes will also affect the selection of leveling agents. In screen printing, the amount of ink transferred is large,
and poor leveling and ink piling are prone to occur. It is necessary to select a leveling agent with good leveling and anti-cratering properties,
such as silicone-modified acrylate leveling agents, which can not only reduce surface tension to achieve good leveling, but also control the
fluidity of ink to a certain extent and prevent ink piling; in gravure printing, the ink dries quickly, and the leveling agent is required to work
in a short time, quickly reduce surface tension, and make the ink level quickly. At this time, low molecular weight polyether-modified
polysiloxane leveling agents are more suitable.
(III) Pay attention to printing effect requirements
If there are high requirements for the glossiness of printed products, polysiloxane leveling agents that can improve surface smoothness
and glossiness can be selected. It can make the surface of the ink film smoother and enhance the ability to reflect light, thereby improving
the glossiness; if it is necessary to avoid defects such as fog and fish eyes on the surface of printed products, leveling agents with good
compatibility and no side effects should be selected, such as some special structured acrylate leveling agents, which will not affect the
transparency and adhesion of the ink while improving the leveling.
III. Master the correct usage and dosage
(I) Timing and method of addition
The timing of adding the leveling agent has an important influence on its effect. Generally speaking, in the preparation process of
water-based ink, it is recommended to slowly add the leveling agent after the main ingredients such as solvents and resins are evenly
mixed, and continue to stir to ensure that the leveling agent is fully dispersed in the ink system. Avoid adding the leveling agent after the
ink has leveling problems. At this time, the ink system may have changed and it is difficult for the leveling agent to play the best effect.
The addition method can be direct addition or pre-dilution. Direct addition is suitable for ink systems with good solubility in the leveling
agent. The leveling agent is directly added to the ink and stirred evenly; pre-dilution and addition are suitable for some inks with high
viscosity or poor solubility in the leveling agent. First, dilute the leveling agent with a suitable solvent (such as ethanol, propylene glycol, etc.)
to a solution of a certain concentration, and then slowly add it to the ink. This can avoid uneven dispersion of the leveling agent in the ink,
resulting in local poor leveling or shrinkage problems.
(II) Determine the reasonable dosage
The dosage of leveling agent is not the more the better. Excessive use of leveling agent may have negative effects, such as reducing the
adhesion of ink, generating fogging, affecting the drying speed, etc. In general, the amount of leveling agent added for water-based ink
is between 0.1% and 2% (mass percentage of the total ink). The specific amount needs to be determined by experiment based on factors
such as ink formula, printing process, substrate material, and requirements for printing effect.
When using a leveling agent for the first time, it is recommended to conduct a small test first. Start with a lower addition amount (such as
0.1%), gradually increase the dosage, observe the changes in the leveling effect, drying performance, adhesion and other indicators of the
ink, and find the best dosage that can meet the leveling requirements without adversely affecting other properties. For example, when
printing fine patterns, in order to obtain a better leveling effect, it may be necessary to appropriately increase the dosage of leveling agent,
but at the same time, pay attention to whether the drying speed and adhesion of the ink meet the requirements.
IV, pay attention to other matters during use
(I) Compatibility with other additives
A variety of additives are usually added to the water-based ink system, such as defoamers, thickeners, wetting agents, etc. The
compatibility of leveling agents with these additives is crucial. If the leveling agent is incompatible with other additives, stratification,
flocculation, precipitation and other phenomena may occur, affecting the stability and leveling effect of the ink. When selecting a leveling
agent, it is necessary to understand its compatibility with other additives in the ink, and conduct compatibility tests if necessary. For
example, some polysiloxane leveling agents may react with certain types of defoamers, resulting in weakened defoaming effects or
shrinkage holes. At this time, it is necessary to adjust the additive formula or select additives with better compatibility.
(II) Influence of environmental factors
Factors such as ambient temperature, humidity and ventilation conditions will also affect the effect of water-based ink leveling agents.
Generally speaking, when the temperature is low, the viscosity of the ink will increase, the fluidity will deteriorate, and it is not conducive
to the leveling agent to work. At this time, the ambient temperature can be appropriately increased or the ink can be preheated to improve
the fluidity of the ink; when the humidity is high, the evaporation rate of water in the water-based ink slows down, which can easily lead to
a longer drying time of the ink, which may cause poor leveling or other defects. Therefore, the humidity of the printing environment
should be controlled within an appropriate range (relative humidity is usually recommended to be between 40% and 60%); good
ventilation conditions help the volatilization of water in the water-based ink and accelerate the drying speed, but too strong
ventilation may cause the ink surface to dry too quickly, forming a surface tension gradient, resulting in poor leveling, so the
ventilation intensity should be reasonably controlled.
(III) Storage and transportation requirements
The storage and transportation conditions of the leveling agent will affect its performance. Most water-based ink leveling agents
should be stored in a cool, dry, ventilated environment, avoiding direct sunlight and high temperature. The storage temperature is
generally recommended to be controlled between 5℃ and 35℃. Too high or too low temperature may cause changes in the
performance of the leveling agent, such as stratification and deterioration. During transportation, the leveling agent should be
protected from severe vibration and collision, and the packaging container should be protected from leakage or impurities.
At the same time, the shelf life of the leveling agent should be paid attention to. Expired leveling agents may lose their effectiveness
and cannot be used.
In summary
The correct use of water-based ink leveling agents is the key to obtaining high-quality printed products. By
understanding the working principle of the leveling agent, selecting suitable products according to actual needs, mastering
the correct use method and dosage, and paying attention to other matters during use, the role of the leveling agent can be
fully utilized, the problem of poor leveling of water-based inks can be effectively solved, and the printing effect can be better.
With the continuous development of the printing industry, the performance and application requirements of water-based ink
leveling agents will become higher and higher. We need to continue to explore and learn to adapt to the new needs of the industry.
