IMPROVED METHOD FOR MAKING SULFONATED BLOCK COPOLYMERS, METHOD FOR MAKING MEMBRANES FROM SUCH BLOCK COPOLYMERS AND MEMBRANE STRUCTURES

摘要

The present invention relates to an improved method for making sulfonated block copolymers and to methods for making membranes from such block copolymers. In particular, the present invention relates to an improved method for making sulfonated block copolymers having at least two polymer end blocks that are resistant to sulfonation and at least one polymer interior block that is susceptible to sulfonation where the sulfonation agent is C2 to C8 acyl sulfate. In the improved process the residual carboxylic acid formed from the C2 to C8 acyl sulfate is converted to C1 to C4 alkyl esters by contacting the residual carboxylic acid with at least a 0.9:1 molar ratio of a C1 to C4 alcohol to residual carboxylic acid, resulting in an improved sulfonated block copolymer solution. The present invention further relates to the use of such sulfonated block copolymer solutions to prepare various membranes and other articles.