Use of molecular sieve paste
for water adsorption in polyurethane industrial floors
Industrial floor coating application
The requirement profile for the performance and appearance of modern industrial floor coatings remains high. In addition to epoxy coatings and polyaspartic systems, polyurethanes in particular have now established themselves on the market.
Polyurethane (PU) floor coatings can be highly resilient, abrasion-resistant and yet very elastic. Another advantage is their high UV resistance. The basic requirement for optimal performance is always a bubble-free curing reaction.
Isocyanate crosslinking
In the case of the desired crosslinking, the hydroxy functions in the polyol react with the isocyanate groups of the hardener. This gives the resulting PU resin its strength and high resistance. There is also a side reaction, however, in which the isocyanates react with water molecules. The problem is exacerbated by the frequently used hardening accelerators (catalysts). After the formation of an unstable carbamic acid, this leads to the release of carbon dioxide gas. Bubbles form in the polymer; Optics and performance are severely impaired.
To avoid this, all residual water must be bound in the polyol before the crosslinking takes place. A typical area of application for our molecular sieve products.
In addition to powders, the use of our molecular sieve paste Finma-Sorb 430 PR has proven itself in the field of PU applications. This is a dispersion of molecular sieve particles in castor oil.
The application advantage lies above all in the dust-free and simple dosing and processing. Finma-Sorb 430 PR is pumpable and can also be filled and delivered in road tankers.
High shear rates are not required for incorporation. We ensure and control the optimal dispersion fineness and stability already during paste production.
Castor oil is an ideal partner for the molecular sieve. It protects the water-drawing product from the surrounding humidity and increases its shelf life. Castor oil itself is a polyol based on renewable raw materials. It participates in the crosslinking reaction and therefore has little influence on the stability of the polyurethane.
The pore diameter
Molecular sieves are usually obtained with sodium as counterions after production. The pore diameter is then 4 angstroms. In order to make the adsorption even more selective compared to water, the molecular sieve is converted into the potassium form via an ion exchange. The pore diameter drops to 3 angstroms. The remaining portion of sodium zeolite should remain minimal.
The wetting properties
Depending on the washing process and the ion concentration on the surface of the molecular sieves, the dispersing properties, the influence of viscosity and the settling behavior can fluctuate greatly. Reproducibility can only be ensured by optimal process control.
Foreign ions
A high number of foreign ions such as iron (III) has a negative effect on the storage stability of polyols. Through catalytic processes they age faster and the pot life decreases.
Finma-Sorb 430 PR does not show this problem. We only use products with a high degree of purity.
