Aromatic Polyester Polyols Based on Phthalic Anhydride PA

3 Aromatic Polyester Polyols Based on Phthalic Anhydride (PA) [25,26] 

PA is commercialised in large quantities (especially for use in plasticisers, such as dioctylphthalate and unsaturated polyesters), in high purity form. The aromatic polyester polyols based on PA, due to the purity of the raw materials, are colourless liquids and the process of fabrication, is very reproducible (good consistency). The polyester polyols based on PA and DEG are synthesised in two steps  

Of course during the polycondensation reaction superior oligomers are formed, such as the structure shown in reaction 16.7 and in the composition of the resulting polyester polyol, free DEG is present. 

As a representative example, an aromatic polyester polyol derived from PA and DEG has an equivalent weight of 178-239, a functionality of 2 OH groups/mol, an hydroxyl number in the range of 230-390 mg KOH/g and the viscosities are lower, around 2,000-4,500 mPa-s at 25 °C. 

All the aromatic polyester polyols have a high aromaticity, of around 20%. 

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