Pressure ethoxylation in dense gases to produce hydroxyalkyl ester monomer

A process for reacting dicarboxylic acid with alkylene oxide to produce hydroxyalkyl ester monomers and perhaps minor amounts of oligomers comprising:

• reacting dicarboxylic acid with alkylene oxide in a solvating compressed gas medium, at a pressure such that the density of the gas medium is greater than or equal to half the critical density of the compressed gas, at a mole ratio of less than about 2 moles of said alkylene oxide per mole of said dicarboxylic acid, at suitable reaction conditions to produce mono- or mono and bishydroxyalkyl ester monomers and perhaps minor amounts of oligomers, said monomers and any unreacted dicarboxylic acid having a carboxyl end group:
• hydroxyl end group ratio of greater than about 0.5;
• and wherein the mole ratio of monohydroxyalkyl ester monomer to bishydroxyalkyl ester monomer is greater than about 0.3,
• wherein said dicarboxylic acid is selected from the class of terephthalic, isophthalic, phthalic, sebacic, malonic, azelaic, glutaric, suberic, succinic, adipic, bibenzioc, oxalic, pimelic, maleic, fumaric, those derived from naphthalene, anthracene, anthraquinone and biphenyl, hemimellitic acid, or mixtures of these;
• anlydrides thereof, mixtures of anhydrides, or mixtures of dicarboxylic acid and dicarboxylic acid anhydride.