Key issues that cannot be ignored when adding color paste dispersants
In the production process of coatings, inks, plastics and other industries, color paste dispersants are important
additives to ensure uniform dispersion of pigments and improve product quality. However, if the addition process
is not properly operated, not only will the dispersant's effectiveness fail to play a role, but it may also cause a
series of quality problems. In order to make color paste dispersants better serve production, we need to fully
understand the key issues that need to be paid attention to when adding.
I. Compatibility of dispersants and systems
(I) Pigment property matching
Different types of pigments have unique surface properties and particle size characteristics, which requires the
selection of color paste dispersants that are compatible with them. For example, for organic pigments, due to
their low surface polarity, dispersants containing special functional groups are required to be adsorbed on the
pigment surface through intermolecular forces, reduce surface energy, and achieve dispersion. Inorganic pigments,
such as titanium dioxide, have relatively high surface polarity, and anionic or non-ionic dispersants can work better.
If the dispersant and the pigment do not match, the dispersant may not be effectively adsorbed on the pigment
surface, the pigment still agglomerates, and the expected dispersion effect cannot be achieved, which ultimately
affects the color and performance of the product.
(II) Carrier system adaptation
The properties of the carrier system, such as resins and solvents, are also crucial to the selection of dispersants.
In water-based systems, it is necessary to select dispersants with good hydrophilicity to ensure that they are stable
in water and play a dispersing role; in solvent-based systems, the compatibility of dispersants and solvents must be
considered to avoid phase separation. For example, in alkyd resin coatings, if a dispersant that is incompatible with
alkyd resin is used, the dispersant will precipitate, destroy the stability of the system, and cause problems such as
stratification and flocculation, which seriously affect the production and use of the coating.
II. Accurately control the amount of dispersant used
(I) The impact of insufficient dosage
The amount of color paste dispersant used is not determined at will. Insufficient dosage will lead to insufficient
pigment dispersion. When the amount of dispersant added is too small, it cannot completely cover the surface of the
pigment particles, and the attraction between the pigment particles still exists, making it easy to regroup. In the
production of plastic products, if the amount of dispersant is insufficient, color spots and color dots will appear on the
surface of the plastic products, reducing the appearance quality and mechanical properties of the products, and may
even cause the products to be unqualified and increase production costs.
(II) Disadvantages of excessive dosage
Adding too much color paste dispersant will also cause problems. On the one hand, too much dispersant will increase
production costs and cause unnecessary waste; on the other hand, excessive dispersant may change the rheological
properties of the system, causing abnormally high viscosity of the system and affecting the processing performance
of the product. In the ink industry, excessive dispersant will lead to poor ink fluidity, poor transfer and plate sticking
during printing, which will seriously affect the printing quality and efficiency. Therefore, it is necessary to accurately
determine the optimal amount of dispersant through small sample tests combined with the characteristics of the
pigment and system.
III. Reasonable selection of addition method
(I) Importance of addition order
When adding color paste dispersant, improper order may affect the dispersion effect. Generally speaking, the dispersant
should be mixed evenly with part of the carrier first, then the pigment should be added for pre-dispersion, and finally
the pre-dispersion should be added to the entire system. For example, in the production of paint, if the pigment is
added first and then the dispersant is added, the dispersant may not be able to fully contact with the pigment in time,
some pigments have agglomerated, and the difficulty of later dispersion increases, making it difficult to achieve an
ideal dispersion state. A reasonable order of addition can make the dispersant adsorb quickly and evenly on the surface
of the pigment particles, improving the dispersion efficiency.
(II) Control of the addition speed
The speed of adding dispersants should not be ignored. Adding dispersants too quickly may cause the local concentration
of dispersants in the system to be too high, forming lumps and unable to be evenly dispersed; while adding too slowly will
extend the production cycle and reduce production efficiency. Usually, a slow and uniform addition method should be adopted,
and appropriate stirring should be combined to ensure that the dispersant can be mixed with the system in time. For example,
during the stirring process of the high-speed disperser, the dispersant is slowly poured along the wall of the stirring kettle to
ensure that the dispersant is smoothly diffused in the system.
IV. Other precautions
(I) Influence of environmental factors
The environmental conditions for adding color paste dispersants have a certain influence on the dispersion effect. Too high or
too low ambient temperature will change the activity of the dispersant and the fluidity of the system. When the temperature is
too high, the active ingredients in the dispersant may volatilize or decompose, reducing the dispersion performance; too low
temperature will increase the viscosity of the system and make it difficult for the dispersant to disperse evenly. Generally speaking,
the suitable operating temperature is between 20℃ - 30℃. In addition, environmental humidity may also affect the performance
of some moisture-sensitive dispersants, and environmental control needs to be performed according to the characteristics of the
dispersant.
(II) Compatibility with other additives
In actual production, in addition to color paste dispersants, other additives such as defoamers, leveling agents, stabilizers, etc. are
also used. There may be interactions between these additives. If the compatibility is poor, it will affect the dispersion effect and
product performance. For example, some defoamers may destroy the stable structure of the dispersant and cause pigment
agglomeration; while some leveling agents may react chemically with the dispersant, change the surface tension of the system,
and affect the dispersion of the pigment. Therefore, before adding the dispersant, it is necessary to conduct an additive compatibility
test, reasonably adjust the type, dosage and order of addition of the additives, and ensure that the additives work synergistically.
Adding color paste dispersants is a key link in the production process. Only by paying full attention to the compatibility of the
dispersant with the system, accurately controlling the dosage, reasonably selecting the addition method, and considering
environmental factors and compatibility of additives, can the role of the dispersant be fully exerted, the pigment can be evenly
dispersed, and high-quality products can be produced. With the continuous development of industry technology, the research
on the process of adding color paste dispersants will become more in-depth, providing more powerful technical support for the
production of various industries.
