Table 1 -- Percent Phosphate Ester vs Properties of SOPEP %PO4 2 3 3.
It was found that by careful selection and formulation, SOPEPs can be successfully used for low-VOC waterborne coating formulations.
A series of SOPEPs was synthesized using phosphoric acid varying from 2-30% by weight of ESO.
SOPEPs containing ionizable acid phosphate groups are capable of self-emulsification in water, after neutralization with suitable amines.
The process and the reagents used in the synthesis of SOPEP makes them low cost polyols.
Results of the MEK double rub tests indicated that, in general, PU films based on SOPEP did not have good resistance to polar solvent.
3) Formulations based on SOPEP show a significantly higher degree of reaction at both ambient and elevated temperature curing conditions (Figures 2 and 3).
Based on the above, we believe that the poor solvent resistance (low MEK double rubs) was primarily a result of the SOPEP fatty acid chains rather than insufficient degree of curing.
We also observed similar results, in a separate study, for coatings based on SOPEP cured with melamine type crosslinker at elevated temperature.
SOPEP had good solubility in tertiary butyl acetate, which allows for the incorporation of this solvent in very low VOC formulations.
Incorporation of SOPEP into polyester polyol would be expected to reduce the film hardness and solvent resistance (MEK) of the cured film, for both aromatic and aliphatic systems.
Generally, hardness and solvent resistance are reduced by SOPEP systems, as compared to conventional polyester polyol-based systems.