INVESTIGATION OF THE ETHERIFICATION REACTION OF ORTHOPHOSPHORIC ACID WITH POLYETHYLENE OXIDE

Based on aromatic polyisocyanate and organophosphorus branched ionomeric polyols (PIP-PEO) obtained using triethanolamine (TEA), orthophosphoric acid (OPA) and hydrophobic polypropylene oxide (PPO), polyurethanes (PIP-PPO-PU) were synthesized as polyols. The catalytic activity of tertiary amines in the low-temperature etherification of ortho-phosphoric acid was established and the role of associative interactions with the participation of tertiary amines and polypropylene oxide in the catalytically activated low-temperature etherification of ortho-phosphoric acid was determined. The obtained PIP-PPO-PU were investigated as pervaporation membranes in the separation of aqueous-alcoholic solutions. To improve the first-generation characteristics, PPO was replaced with hydrophilic polyethylene oxide with MM=400 (PEO). It turned out that PIP-PEO-PU exhibit higher pervaporation characteristics in comparison with PIP-PPO-PU. This paper presents the results of a study of the reaction of etherification of orthophosphoric acid with polyethylene oxide activated by triethanolamine during the synthesis of PIP-PEO. According to IR spectroscopy data, for PIP-PEO, the high-intensity bands of phosphate ions of orthophosphoric acid disappear at 880 and 960 cm-1 and new bands appear at 950 and 1010 cm-1. Based on the results of titrimetric analysis, the conversion of orthophosphoric acid was determined depending on the molar excess of OPA and PEO relative to triethanolamine under various temperature conditions. For the TEA - OPA - PEO system, the molar ratio varied within [TEA]:[OPA]:[PEO]=1:5:(8-20). It was found that an increase in the molar fraction of polyethylene oxide relative to triethanolamine during the synthesis of PIP-PEO leads to an increase in the conversion of orthophosphoric acid from 23 to 46%. In order to confirm the catalytic effect of tertiary amines on the OPA etherification process with polyethylene oxide, triethanolamine was replaced with triethylamine. The increase in the reaction rate and conversion of orthophosphoric acid to 49% observed in this case indicates the direct involvement of amines as catalysts.