Quest: The "Chameleon" of Auxiliaries

Coating additives are used to improve or alter certain properties of coatings, including assisting in coating production, storage, transportation, construction, and final paint film. A single additive variety in the paint formula generally does not exceed 1%, really can be said to be a small add-on effect. Whether from function or chemical type, there are many types of additives

.
This paper introduces a common but relatively special class of additives from different chemical types -
silicone additives, which have the "additive world color changer" called
, let's see what kind of variant it has.
01
Silicone additive structure introduction
silicone additives, also known as modified sioxane additives, its molecular structure consists of two parts, silicone oxygen chain segment and organic modified chain segment. Of course, the position of organic change can be in the side chain, or at the end of the chain. The structure of the silicone additive shown in the figure below is only a side chain change.
"variant" trick of silicone additives stems from the flexible adjustment of the type and length of their silicone oxygen and organic modified chain segments. Different structures will give silicone additives different properties.
In which, the length of the silicon oxygen chain segment determines its ability to reduce static surface stress and shrink holes, we can effectively adjust the silicon oxygen chain segment (n value) to achieve different additive properties: such as substrate wetting, surface control (flat, feel, scratch and anti-adhesive, etc.), de-foaming/de-foaming, anti-graffiti and hammering, and so on.
of organic modified chain segments can also vary, usually with polyethers, polyesters, and alkyl fangs.
polyether steroid,
is the most common type of additive, especially for water-based and radiation curing formulations. Polyether modified silicone additives have good compatibility and regulate their water solubility and stability tendency by selecting different polar polyethers.
polyester and alkyl alkyl alkyl modified, and
mainly used in solvent-based formulations.
the length of the organic modified chain segment can also be adjusted to change its silicone properties and compatible by adjusting the length of the organic modified chain segment.
02
Silicone additive function
1, substrate wetting
for traditional solvent-based formulations, unless the substrate is contaminated by low surface energy pollutants (e.g. grease, etc.), generally speaking, the surface pressure of the formulation system is lower than the surface energy of most substrates, can wet the vast majority of substrates, do not need to use wetting agents to wet the substrate.
and water-based formula, due to the addition of high surface pressure water, the formula surface pressure is high, the need to add wetting agent to reduce surface pressure, so that the surface of the coating is slightly lower than the surface energy of the substrate, to achieve the coating on the substrate wetting.
the following are the common substrate wetting agent TEGO® Wet 270 to improve the effect of plastic substrate (pp) wetting.
2, flow and leveling
affect flow and leveling factors, such as paint fluidity, surface stress, construction methods and viscosity, coating thickness and drying speed and so on. The leveling time can be viewed by the following simplified formula:
t: the time required for full leveling
C: constant, the coating fluidity, drying speed and other factors into
ŋ: viscosity
γ: the surface pressure of the coating
d: film thickness
It is clear that the lower the viscosity of the coating, the shorter the leveling time; The higher the surface pressure described here, the better it is to moisturize. When wetting is good, the higher the surface pressure of the coating, the more conducive to flow leveling. In addition, it is necessary to take into account the elimination of different parts of the liquid surface pressure difference, so that the paint film surface pressure is at an average level, to avoid the Benaud vortex, in order to get a flat and beautiful paint film effect. The above functions can be implemented with the help of silicone surface control aids.
the following are common surface control aids TEGO® Glide 100 to improve leveling.
Three, feel, anti-adhesion, anti-scratch
due to the incompatible silicone oxygen chain segment in modified silicone, they will migrate to the gas-liquid interface, will be quickly directed to the coating surface. The coating surface is smooth, scratch-resistant and anti-adhesive due to the rich silicone oxygen chain segment.
the following are common surface control additives TEGO® Glide 482 to improve smoothness and anti-adhesion effect.
4, de-foaming, de-foaming
the infringing of air in coatings or wet films is unavoidable, with stirring or grinding during coating production, coating construction processes (e.g. high-pressure airless spraying/roller coating), and even CO2 due to chemical reactions (e.g. NCO and H20 reactions). Bubbles in water-based coatings can be stable, mainly caused by the stability of surfactants, such as the emulsifying agent of the resin itself. The defects caused by bubbles are very difficult, if the paint grinding too much foam will reduce grinding efficiency, thereby increasing energy consumption, the construction process of bubbles will affect the appearance of the paint film and even dry film corrosion resistance. This requires the use of defrosting agent to eliminate foam, especially the high viscosity thick film application system, but also rely on defrosting relatively strong silicone deblister to eliminate
foam.
following are the effects of the common debouling agent TEGO® Airex 902W to help remove the system microblisters.
, anti-graffiti
long-chain silica resin has a strong hydrophobic and oil-absorbing effect, which brings good easy cleaning performance, such as anti-graffiti, anti-fouling and so on.
6, hammer-print effect
long-chain polydymethane has low surface stress and low compatible, and the formula body resin formed Benaud vortex cells, bringing hammer-print effect. The hammer pattern effect is related to the amount of hammer coating and the thickness of the film.
03
Recommended additions, operations
recommended additions:
Silicone substrate wetting agent additions are 0.1-0.5% of the total formula
silicone surface control additive additions are 0.05 -2.0% of the total formula (smooth, scratch-resistant and anti-adhesive need for high additions, flow-promoting low additions)
Silicone deblister addition is 0.1-0.5% of the total formula
silicone anti-graffiti additive addition is 1-5% of the total formula
silicone hammer-pattern additive addition is 0.5-2.5% of the total formula
or more is only recommended to add the amount range, the amount of addition and formula resin system and construction methods, etc.
recommended process:
substrate wetting agent, surface control additives (flow leveling, smoothing, scratch resistance and anti-adhesion) as far as possible in the later stages of the production process to avoid stabilizing foam.
silicone-concentrated de-foaming agent needs to be added in the previous section to ensure sufficient shearing to be distributed equally into the formulation system.
anti-graffiti additives need to test their compatible with the main resin, recommended in the grinding phase, varnish recommended high-speed mixing added.
hammer-print additives are recommended to be added at the end of the production process to avoid the effect of hammer-print effects due to improved compatibleness caused by high shears such as grinding.

re-coatability of silicone additives
most formulators are more concerned with the re-coating of silicone additives when using them. First of all, silicone additives because of their different chemical structure, some may affect re-painting, and some have no effect on re-painting. This is not absolute and is related to many factors. For example, one of the factors: whether silicone additives contain reactive groups, in the reaction system (such as hydroxy and isocyanate curing agents), silicone additives will be locked in the paint film, when the next layer of coating, difficult to re-dissolve, float to the surface of the new coating, will lead to poor reappling.
other factors are not repeated here, the formulator if the re-coating of silicone additives is not clear, it is recommended that we can contact our technical service personnel for targeted answers.
source: Created coating additives