Have you solved the delamination problem of water-based coatings?

The delamination phenomenon of paint is an important problem often encountered in the process of production, storage, and use.
It not only affects the can opening effect, but also changes the performance of the paint
.

Severe hard precipitation may cause the paint to be scrapped and unusable

So, what causes the delamination of the paint?

How can we solve this situation?

Different phenomena of paint delamination

1.

After the paint is stored for a period of time, a part of transparent light yellow or colorless transparent mucus paint is separated on the surface of the paint.
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.

2.

The surface layer of the paint separates a certain amount of liquid, sometimes the liquid has some blue light, in most cases the separated liquid is milky white
.

3.

During the storage of the finished paint, the uniformity of the paint changes.
The distribution of heavy and large particles in the paint is uneven, and there is a gradient change in the vertical direction.
From the top surface to the bottom, the paint changes from release to thick.
The change, even hard deposits appear at the bottom
.
This phenomenon of paint is called sedimentation of paint
.

In the above three cases, the separation of water emulsion is usually accompanied by sedimentation

What are the reasons for these stratification phenomena?

Stratification factors

 1.

The improper matching of hydration-type thickeners and associative thickeners in types and dosages results in incompatibility and rejection of the coating during storage
.

If the compatibility of the two networks in the system is not good, one is too hydrophobic and the other is too hydrophilic, using such a thickener to match, water separation is difficult to control

Too low a low shear viscosity will also cause delamination
.

Regarding the choice of thickeners, it is generally to choose several different thickeners to be used together to make the coating have suitable high, medium and low shear viscosity.
When necessary, use a post-anti-settling agent
.
Under the premise of stable storage, better workability is guaranteed
.

2.

Whether the pigment is well dispersed and stable, whether there is flocculation, etc.
, will affect many properties
.
Pigments and fillers have poor dispersibility, and particles agglomerate into large particles, thereby accelerating sedimentation
.

Many people may take it for granted that anti-sedimentation must be relied on anti-sedimentation agents.
In fact, this is one-sided
.
If the ground color paste is flocculated, the pigment particles will become larger and the specific gravity will increase, and it will settle quickly, especially the organic pigments
.
If a suitable dispersant is selected, the anti-settling agent can be omitted or added less
.

Therefore, if sedimentation occurs, consider replacing the dispersant

TIPS: The powder and the associative thickener are in the same aqueous medium and have competitive adsorption on the surface of the pigment and emulsion particles.
There is a complicated competitive relationship between the two.
Whether their combination is reasonable or not directly affects the performance of the coating And stratification issues
.

3.
The choice of anti-settling agent

In many cases, regarding the problem of delamination, people still choose to add anti-settling agents to the paint, that is, introduce a loose network thixotropic structure into the paint, which can make the pigment and filler particles suspend without agglomeration and prevent the pigment from settling
.

So, how to choose different types of anti-settling agents?

01 Organobentonite

Organobentonite usually does not exist as primary particles, but is generally agglomerates of multiple particles.
Primary particles can be produced through the process of wetting, dispersion and activation to form an efficient thixotropic effect
.

In the polar system, in addition to providing chemical energy to help the organic bentonite disperse, the polar activator makes countless bentonite flakes form a gel structure through the bridging of water molecules, and the hydrocarbon chains on the flake surface are solvated by its stronger solvation.
Ability to thicken the system and produce a thixotropic effect.
Under the action of external force, the structure is destroyed and the viscosity is reduced, while the elimination of external force will restore the original viscosity and structure.

SN-T9350 is a specially processed montmorillonite clay that can form a card house structure after being dispersed in an aqueous system, providing thickening, thixotropy, anti-settling, anti-sagging and anti-water separation functions
.

What are the advantages and disadvantages of bentonite anti-settling?

advantage:

Large application range; small addition amount, high efficiency, stable processing performance; good thixotropy performance; low price
.

shortcoming:

It has an impact on gloss, and there will be haze and turbidity in the varnish; poor resistance to strong solvents; poor leveling and anti-sagging effects; due to the need for good dispersion to achieve the best anti-settling effect, Therefore, it is difficult to use for post-addition.
If post-addition is required, it needs to be prepared into a pre-coagulated slurry
.

02 Fumed silica

Fumed silica has the greatest thickening effect in non-polar media
.
Fumed silica is produced by hydrolyzing silicon tetrachloride in a hydrogen-oxygen flame
.
It has a small particle size, a large specific surface area, and has silanol groups on the surface
.
These silanol groups can interact with adjacent fumed silica particles to form hydrogen bonds, and form a thixotropic structure in a three-dimensional space through hydrogen bonding
.

advantage:

It does not need to be activated and can be used directly
.

shortcoming:

Light weight, inconvenient construction; thixotropic effect is not very ideal; used on the top coat affects the gloss and affects the leveling
.

03 castor oil derivatives

Castor oil derivatives are dispersed and activated in a non-polar solvent, and the swollen long chains are entangled with each other to form a thixotropic structure and play a role in thickening
.

When subjected to shearing force, the winding is pulled apart, the structure is destroyed, and the viscosity will drop; when the shearing force disappears, the winding is re-wound
.
This re-winding process is slow, so the viscosity recovery is slower, allowing a longer flow time to level, and proper adjustment can make the paint still level to a certain extent when the sag limit thickness is larger
.

advantage:

The thixotropic performance is relatively good; the leveling property is good; the effect on the gloss is small; the price is lower
.

shortcoming:

It needs to be activated in advance when in use; it is not suitable for strong solvent systems; it is easy to return to coarse
.

04 Polyamide wax

Through the intertwining of macromolecular chains to form a network structure, it has thixotropy.
When sheared, the entangled molecules are pulled apart and the viscosity decreases; when the shearing stops, the macromolecules re-twist and increase the viscosity
.

Because the process of this new winding is relatively slow, the speed of viscosity recovery is also slow, and there is a long time for the wet film to flow and level, but it will not cause the sag to lose control
.

The thixotropic properties of polyamide wax are less dependent on temperature, and still have a good anti-sagging effect when used at higher temperatures.
It is baking coatings such as amino baking paint, acrylic baking paint, epoxy baking paint and high A very effective rheology modifier in solid coatings, metal coatings, and thick build coatings
.

For example, our SN-T9769 can be used for water-based paints, water-soluble paints and other resin systems, with excellent anti-settling, anti-sagging and other properties, and excellent thickening effect
.

advantage:

The thixotropic performance is the best; the leveling and anti-sagging properties are good; the effect on the gloss is small; it is not easy to return to roughness
.

shortcoming:

It needs to be activated in advance when used; the price is relatively high
.

In addition to the points introduced above, there are actually many factors that will affect the delamination of the coating, such as: improper selection of surfactants or excessive amounts, types and excessive amounts of co-solvents, the thickness and collocation of powders, and the composition of resins and emulsions.
species, PVC design, and so on
.
I won’t go into details here~

The problem of stratification should be prevention
.
For the new formula system, everyone should do a good job of storage experiment before production~

So, is there any remedy for the layered paint?

For the settled paint, it can be used after stirring evenly by hand or mechanically
.
For agglomeration, first pour out the flowable part, shovel the sediment from the bottom of the container with a spatula, grind it, and then pour the flowing medium back into the original bucket and mix it thoroughly
.

If it is still unable to mix according to this method, there is still dry precipitation, and the paint can only be scrapped or degraded for use
.