Written on 02.05.2012 - Technology
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Reactive moisture scavenger for polyurethane systems

The Korean company Young's Corporation has launched Supersorb TI (p-Toluenesulfonylisocyanate), a reactive monofuctional isocyanate of low viscosity which reacts with water generating an inert amide (fig. 1). The new product eliminates slight parts of humidity and prevents moisture-related problems in the formulation of polyurethane coatings.

Properties
Supersorb TI can be used for dehydration of solvents, fillers, pigments and bituminous tars. It rapidly reacts with water and generates carbon dioxide and toluenesulfonamide which is generally inert towards further reaction with alkyl and aryl isocyanates, and it is usually soluble in common coating solvents. According to the company, the product prevents gloss reduction, haze, yellowing and reaction foam in PU coatings.

Dosage
The dosage is dependant on the water content of the solvents. Supersorb TI works with the best results, when the amount of moisture is exactly measured. The product can be added in stoichiometric quantity. Supersorb TI reacts in a ratio 12 parts : 1 part with water calculated for a complete reaction.

Application

Supersorb TI can be used in the production phase to help prevent moisture-related problems. According to Young's Corporation, in 1- and 2-component PU systems Supersorb TI can effectively eliminate moisture in solvents, fillers, pigments and the atmosphere, before the hydroxyl- and isocyanate-component are added. Supersorb TI minimizes a lot of deleterious side reactions like CO₂-nascency and polyurea formation (gelling effects) in polyisocyanate systems during the storage period or surface defects (foam, haze, gloss problems) in the coated film.

The use of Supersorb TI in catalyst prepolymer systems depends on the type of catalyst used. Therefore special amine-based catalysts can additionally accelerate the reaction between p-toluenesulphonamide and the isocyanate prepolymer. This effect shows an influence on the NCO/OH-ratio and finally an incomplete cross-linking reaction.

Supersorb TI also dehydrates pigments/fillers. Both can be mixed in the solvent, the calculated dosage of Supersorb TI can be added. The required addition rate of Supersorb TI can vary strongly based on the total moisture content. The total dehydration can take a long time, up to 24 hours. Only then can this mixture be added to the polyol and isocyanate component.

Supersorb-TI reacts with water generating an inert amide

0.5 – 4.0 % of the total formulation weight is sufficient for 0.05-0.30% moisture, says the company. The product eliminates moisture introduced with solvents, pigments and fillers in 1-component as well as in classical 2-component PU systems. Further it is recommended for the storage stabilization of purified diisocyanates against decomposition and discoloration

Specifications of Supersorb TI

Test Item	Specification	Test result
Appearance	Colorless to light straw liquid	Pass
Purity	96.0 wt.-% min.	97.04
Density	Approximately 1.29 g/cm³
Flash point	> 150 °C