Process for dissolution of highly fluorinated ion-exchange polymers
View Patent ↗Highly fluorinated ion-exchange polymers achieve dissolution in aqueous tetrahydrofuran at lower pressures and temperatures than in other solvents, with few or no side products being formed.
1. A process for making a liquid composition of ion-exchange polymer, at least about 50% of the total number of halogen and hydrogen atoms in said ion-exchange polymer being fluorine atoms, said process comprising:
a) contacting the polymer in the solid state with aqueous tetrahydrofuran, said aqueous tetrahydrofuran being comprised of water and tetrahydrofuran in a ratio of about 10:90 to about 90:10 weight %, and
b) heating said polymer in contact with aqueous tetrahydrofuran to a temperature of about 150° C. to about 300° C., in a vessel rated for the pressures encountered at these temperatures, to form the liquid composition, said liquid composition formed from said contacting and said heating containing less than about 3 weight % organic materials other than said tetrahydrofuran and those associated with said ion exchange polymer.
2. The process of claim 1 wherein said aqueous tetrahydrofuran is comprised of water and tetrahydrofuran in a ratio of about 45:55 to about 55:45 weight %.
3. The process of claim 1 wherein said aqueous tetrahydrofuran is comprised of less than about 50 weight % tetrahydrofuran.
4. The process of claim 1 wherein the polymer comprises about 1 to about 15 weight % of the combined weight of polymer and water and tetrahydrofuran.
5. The process of claim 1 wherein said polymer in contact with aqueous tetrahydrofuran is heated in an autoclave.
6. The process of claim 1 wherein said ion-exchange polymer is in the acid form, sodium ion form or potassium ion form, or a combination thereof.
7. The process of claim 1 wherein said ion-exchange polymer is in the acid form.
8. The process of claim 1 wherein said ion-exchange polymer is perfluorinated.
9. The process of claim 1 wherein said ion-exchange polymer has an ion-exchange ratio of about 3 to about 33.
10. The process of claim 1 wherein said ion-exchange polymer has an ion-exchange ratio of about 8 to about 23.