Method for preparing ester end-capped copolyether glycols

A process for preparing ester end-capped copolyether glycol, the process comprising

• (A) bringing together, under conditions suitable for reaction,
• (1) tetrahydrofuran;
• (2) an alkylene oxide containing 2 or 3 carbon atoms in its ring, or a cyclic acetal represented by the structure ##STR7## where n is 2-4 and
• X and X.sub.1 are hydrogen or an alkyl radical of 1-4 carbon atoms;
• (3) an acylium ion precursor;
• and
• (4) as a catalyst, a homopolymer of an ethylenically unsaturated monomer (a) containing groups such that the final polymer will contain groups of the formula ##STR8## where represents the polymer chain or a segment thereof;
• D is hydrogen, an aliphatic or aromatic hydrocarbon radical of 1-10 carbon atoms, halogen or a segment of the polymer chain;
• X and Y are hydrogen, halogen or an aliphatic or aromatic hydrocarbon radical of 1-10 carbon atoms, but at least one of X or Y must be fluorine;
• R is a linear or branched linking group having up to 40 carbon atoms in the principal chain;
• and
• Z is hydrogen, halogen or an aliphatic or aromatic hydrocarbon radical of 1-10 carbon atoms;
• or a copolymer of monomer (a) with at least one other copolymerizable ethylenically unsaturated monomer (b), the homopolymer or copolymer having an equivalent weight of 950-1500 and a solubility such that no more than about 5%, by weight, dissolves in the reaction medium at the reaction temperature, and then
• (B) separating the resulting ester end-capped copolyether glycol from the reaction mass.