Reduction of molecular weight of poly(tetramethylene ether) glycol
AssigneeE. I. Du Pont de Nemours and Company
InventorSuriyanarayan Dorai
Life of this patent
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Abstract
A process for reducing the molecular weight of polytetramethylene ether glycol without significant conversion of polytetramethylene ether glycol to tetrahydrofuran monomer is disclosed. The process involves a two-step procedure. The first step comprises reacting polytetramethylene ether glycol with a perfluoroalkyl carboxylic acid to form a perfluoroalkyl ester of polytetramethylene ether glycol. That ester is, in the second step, converted back to polytetramethylene ether glycol of reduced molecular weight by hydrolysis or alcoholysis.
Claims22
A process for preparing poly(tetramethylene ether) glycols having reduced molecular weights, without significant conversion of said poly(tetramethylene ether) glycols to tetrahydrofuran, comprising:
- (a) reacting, as a starting material, a poly(tetramethylene ether) glycol having a number average molecular weight in the range between about 1000 and 25000 with a perfluorocarboxylic acid and an alkanol containing 1 to 3 carbon atoms, at a temperature of 100.degree. C. to 250.degree. C. for a reaction time of 0.1 to 8.0 hours under autogenous pressure to form a poly(tetramethylene ether) glycol ester said having a molecular weight lower than that of said poly(tetramethylene ether) glycol starting materials;
- (b) converting said lower molecular weight ester having a pH value of about 7 to a poly(tetramethylene ether) glycol by reaction with an alcohol or water;
- and
- (c) recovering from the reaction mixture a poly(tetramethylene ether) glycol having a number average molecular weight in the range between about 250 and 3500.
A process for preparing poly(tetramethylene ether) glycols having reduced molecular weights, without significant conversion of said poly(tetramethylene ether) glycols to tetrahydrofuran, comprising:
- (a) reacting, as a starting material, a poly(tetramethylene ether) glycol having a number average molecular weight in the range between about 1000 and 25000 and an ester of an alkanol containing 1 to 3 carbon atoms and a perfluorocarboxylic acid containing 2 to 4 carbon atoms, in the presence of water at a temperature of 100.degree. to 250.degree. C., and for a reaction time of 0.1 to 8.0 hours under autogenous pressure to provide a bis-perfluoroalkylcarboxylic ester of a lower molecular weight PTMEG;
- (b) separating said lower molecular weight PTMEG ester from the mixture of volatile components, including alcohol, perfluoroalkylcarboxylic ester and perfluoroalkylcarboxylic acid;
- (c) subjecting said lower molecular weight PTMEG ester having a pH value of about 7 to ester exchange with an alkanol containing 1 to 3 carbon atoms at a temperature of 55.degree. to 175.degree. C. for 1 to 8 hours;
- and
- (d) recovering a poly(tetramethylene ether) glycol having a number average molecular weight in the range between about 250 and 3500.
Dependencies are inferred from the claim text.