Users' first action upon opening a can of paint is generally to re-homogenise the paint to evaluate its consistency.
In this regard, a good formulation should ensure a positive impression of smoothness.
This impression may be correlated with a rheological measurement
conducted at a medium velocity gradient, i.e. approximately 100 s-1
. For each type of paint, there is a range of preferential values related to this viscosity called "Stormer viscosity" or "KU viscosity".
Some thickeners can prove more effective than others in increasing these viscosity values to 100 s-1
. Rheology modifiers imparting this behaviour themselves feature a sufficiently high rheology profile at 100 s-1
Figure 1: Rheological Behaviour of Acrylic Thickeners Rheotech™ X800 series
Rheotech™ 2800 and Rheotech™ 3800
are recommended to obtain excellent
appearence and creaminess:
Rheotech™ 2800 for semi-gloss or one coat matt paints
- Rheotech™ 3800 for matt or semi-matt paints
- Rheotech™ 4800 for matt paints or fillers
See the different rheological behaviors of wood stain formulations containing 3 different Coatex thickeners
(Thixol™ 53 L, Viscoatex™ 730 and Rheotech™ 4800)
Color acceptance / Tinting system
Architectural and decorative paints
with deep and vibrant colors are becoming a growing market to be addressed. Very good color acceptance
upon tinting should therefore not be overlooked. In some cases, lack of stability after color addition may occur thus leading to in can pigment separation or flooding issues often revealed by a rub out test.
No color float with Rheotech™
The use of universal colorant in tinting paints can also lead to important drops in viscosity, particularly when the paint is tinted to a deep tone.
In given cases, the interaction between the associative rheology modifiers and the binder can be disrupted resulting in a weaker thickening network.
The viscosity can be dramatically reduced affecting the application properties: poor sag resistance, hiding power and brush load.
Formulators are then driven towards more demanding rheology modifiers offering optimized behaviour after tinting.
The paint, based on Rheotech™ 4800 exhibits less viscosity drop than that of traditional acrylic rheology modifiers.
Figure 2: % viscosity drop after tinting of 5% black pigment T24h – Matt paint (PVC: 82%, styrene acrylic)
Viscosity drop upon tinting as well as color float can then be easily addressed with the associative acrylic rheology modifiers from the Rheotech™ range.
Rheotech™ thickener range
can ensure improved behavior after tinting comparatively to that of standard acrylic thickeners or HEC thickeners.
VOC water-based tinting coatings can benefit from the Rheotech™ thickeners offering excellent color acceptance performances even in the presence of high levels of deep colorants.