Process for preparing sulfonated block copolymers and various uses for such block copolymers

1. 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.

2. The process according to claim 1 , wherein said end blocks A have essentially no sulfonated monomers.

3. The process according to claim 1 , wherein the B block is sulfonated with acyl sulfate as a sulfonation reagent.

4. The process according to claim 2 , wherein the acyl sulfate is acetyl sulfate.

5. The process according to claim 1 , wherein the B block is sulfonated with sulfur trioxide as a sulfonation reagent.

6. The process according to claim 5 , wherein the sulfur trioxide is modified with an ether.

7. The process according to claim 1 , wherein 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.

8. The process according to claim 1 , wherein substantially sulfonated means that at least about 90 percent of the total sulfonation of the block copolymer occurs in the mid block B.

9. The process according to claim 1 , each A block is a segment of one or more polymerized para-substituted styrene monomers.

10. The process according to claim 1 , wherein said A block comprises up to 15 mol percent of polymerized monomers selected from (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.

11. The process according to claim 1 , wherein the block copolymer further comprises at least one polymer block D having a glass transition temperature of less than 20° C. and a number average molecular weight of between 1,000 and 50,000.

12. The process according to claim 1 , wherein the sulfonated block copolymer has a water permeability greater than 0.1 times 10 −6 grams per Pascal.meter.hour, according to ASTM E96-00 “desiccant” method, a wet tensile strength greater than 500 psi according to ASTM D412, and a swellability of less than 100% weight after immersion in water for 24 hours.

13. The process according to claim 1 , further comprising forming the sulfonated block copolymer into an article having a ratio of wet tensile strength to dry tensile strength greater than 0.3.

14. The process according to claim 1 , wherein the interior block B is a hydrogenated copolymer of one or more unsubstituted styrene monomers, and monomers of conjugated dienes having a vinyl content of 20 to 80 mol percent prior to hydrogenation.

15. The process according to claim 1 , wherein said B block is a random copolymer, a tapered copolymer or a controlled distribution copolymer.

16. The process according to claim 1 , wherein the block copolymer has the general configuration A-D-B-D-A, A-B-D-B-A, (A-D-B)nX, (A-B-D)nX, A-B-A, A-B-A-B-A, (A-B-A)nX, or (A-B)nX, or mixtures thereof, where n is an integer from 2 to about 30, and X is coupling agent residue.

17. The process according to claim 16 , wherein said D block is selected from the group consisting of (i) a polymerized or copolymerized conjugated diene selected from isoprene, 1,3-butadiene having a vinyl content prior to hydrogenation of between 20 and 80 mol percent, (ii) a polymerized acrylate monomer, (iii) a silicon polymer, (iv) polymerized isobutylene and (v) mixtures thereof, wherein any segments containing polymerized 1,3-butadiene or isoprene are subsequently hydrogenated.

18. An article formed at least in part from a composition prepared by the process according to claim 1 , said article being selected from the group consisting of fuel cells, fabrics, coated fabrics, membranes, filtration membranes, desalination membranes, air conditioning membranes, heat recovery membranes, coatings for membranes, personal hygiene articles, adhesives, hydrogels, antifouling coatings, water absorption articles, electrode assemblies, and marine coatings.