Process for the isolation of sulfonyl fluoride polymers and polymers obtained therefrom
The invention relates to a process for the isolation of (per)fluorinated polymers containing sulfonyl fluoride functional groups from a polymerization latex. The process comprises adding the polymerization latex to an aqueous electrolyte solution under high shear stirring at a temperature equal to or lower than the glass transition temperature of the polymer. The invention further relates to the (per)fluorinated polymers containing sulfonyl fluoride functional groups isolated by the process and characterised by a loss of weight at 200° C. lower than 1% as determined by thermogravimetric analysis.
1. A process for the isolation of a polymer from a polymerization latex, the process comprising adding said latex under high shear stirring to an aqueous electrolyte solution held at a temperature equal to or lower than the glass transition temperature of the polymer wherein said polymer comprises recurring units derived from at least one ethylenically unsaturated (per)fluorinated monomer (A) containing at least one sulfonyl fluoride group, wherein said polymer exhibits a loss of weight at 200° C. lower than 1% as measured by thermogravimetric analysis according to ASTM E1131-86, and wherein said polymer exhibits a melt flow rate measured according to ASTM D1238-04 at 200° C./5kg of less than 50 g/10 min.
2. The process of claim 1 wherein the rate of stirring is such that the Reynolds number Re=ρ·N·d I 2 /μ wherein ρ is the density of water (kg/m 3 ), N the number of revolutions per second of the impeller (1/s), d I the diameter of the impeller (m) and μ the dynamic viscosity of water (Pa·s) is greater than 10,000.
3. The process of claim 1 wherein the electrolyte is selected from the group consisting of HNO 3 , Al(NO 3 ) 3 , Al 2 (SO 4 ) 3 , Ca(NO 3 ) 2 , Zn(NO 3 ) 2 , ZnSO 4 , CaCl 2 , and MgSO 4 .