Patent ID: 8003733

Claim:
A process for preparing sulfonated block copolymers that are solid in water having at least two polymer end blocks A and at least one polymer interior block B, the process comprising sulfonating said interior block B until said block B is substantially sulfonated, and wherein: a. each A block is a polymer block resistant to sulfonation and each B block is a polymer block susceptible to sulfonation, said A and B blocks containing no significant levels of olefinic unsaturation; b. each A block independently having a number average molecular weight between 1,000 and 60,000 and each B block independently having a number average molecular weight between 10,000 and 300,000; c. each A block comprising at least one segment of one or more polymerized para-substituted styrene monomers and optionally one or more segments selected from polymerized (i) ethylene, (ii) alpha olefins of 3 to 18 carbon atoms; (iii) 1,3-cyclodiene monomers, (iv) monomers of conjugated dienes having a vinyl content less than 35 mol percent prior to hydrogenation, (v) acrylic esters, (vi) methacrylic esters, and (vii) mixtures thereof, wherein any segments containing polymerized 1,3-cyclodiene or conjugated dienes are subsequently hydrogenated; d. each B block comprising segments of one or more vinyl aromatic monomers selected from polymerized (i) unsubstituted styrene monomers, (ii) ortho-substituted styrene monomers, (iii) meta-substituted styrene monomers, (iv) alpha-methylstyrene, (v) 1,1-diphenylethylene, (vi) 1,2-diphenylethylene and (vii) mixtures thereof; e. said B blocks are sulfonated to the extent of 10 to 100 mol percent, based on the units of vinyl aromatic monomer in said B blocks; and f. the mol percent of vinyl aromatic monomers which are unsubstituted styrene monomers, ortho-substituted styrene monomers, meta-substituted styrene monomers, alpha-methylstyrene, 1,1-diphenylethylene and 1,2-diphenylethylene in each B block being between 10 mol percent and 100 mol percent; and g. said sulfonated block copolymer is non-dispersible and solid in water, and has a tensile strength greater than 100 psi in the presence of water according to ASTM D412 after immersion in water for 24 hours.