Process for coagulating sulfonated block copolymers
View Patent ↗Sulfonated block copolymers (SBCs) are coagulated from SBC solutions in one or more organic solvents, including reaction mixtures obtained in the sulfonation process, by a process in which the SBC solution is ejected into or onto water provided that no steam is added to the SBC solution prior to ejection and provided that the ejection velocity as well as the water temperature and convection are controlled and balanced. The coagulation process is easy to implement and avoids or at least diminishes problems due to foaming and the formation of micro dispersions of the SBC which cannot be separated successfully or easily by conventional filtration or centrifuging.
1. A process for coagulating a sulfonated block copolymer from a solution comprising the block copolymer and one or more organic solvents, the process comprising:
(a) an ejection stage which comprises ejecting the copolymer solution into or onto moderately stirred water to form a coagulation mixture, wherein
the ejected copolymer solution is substantially free of steam; and
the water is at an operating pressure and is at an operating temperature below its boiling point; and
(b) a holding stage which comprises subjecting the coagulation mixture formed in stage (a) to moderate stirring at a holding pressure and at a holding temperature below the boiling point of water for a period sufficient to substantially completely evaporate the one or more organic solvents.
2. The process of claim 1 , wherein the copolymer solution has a copolymer concentration of about 8 g/l to about 140 g/l.
3. The process of claim 1 , wherein the copolymer solution consists essentially of from about 0.5 to about 30%-wt. of the copolymer,
from about 60 to about 99.5%-wt. of the one or more organic solvents, and
up to about 10%-wt. of by-products and/or impurities.
4. The process of claim 1 , wherein, at the operating pressure, the boiling point of the one or more organic solvents is below the boiling point of water.
5. The process of claim 1 , wherein the boiling point of the one or more organic solvents at atmospheric pressure is less than 100° C.
6. The process of claim 1 , wherein at least one of the one of more organic solvents of the copolymer solution has one or more of the following properties:
i) the solvent is a hydrophobic solvent; and/or
ii) the solvent is an apolar solvent; and/or
iii) the solvent has a boiling point in the range of from about 45° C. to about 99° C. at standard atmospheric pressure; and/or
iv) the solvent has a density of at most 1 g/cm 3 ; and/or
v) at most 2 g of the solvent is soluble in 1 l of water at about 25° C.
7. The process of claim 1 , wherein the operating temperature in stage (a) is such that the one or more organic solvents have a vapor pressure which is greater than about 70% of the stage (a) operating pressure.
8. The process of claim 1 , wherein the copolymer solution is ejected continuously or intermittently as a non-atomized stream.
9. The process of claim 1 , wherein the copolymer solution is ejected onto the water surface at a region of the surface having low shear stress.
10. The process of claim 1 , wherein the copolymer solution is ejected at a velocity of from about 0.3 m/s to about 10 m/s.
11. The process of claim 10 , wherein the copolymer solution is ejected at a velocity of from about 0.3 m/s to about 5 m/s.
12. The process of claim 1 , wherein the holding temperature in stage (b) is below the boiling point of water at the holding pressure and the holding temperature is equal to, or greater than, the operation temperature in stage (a) when the holding pressure is equal to, or greater than, the operating pressure.
13. The process of claim 1 for producing a coagulate of the copolymer comprising coagulated copolymer in form of discrete hydrated copolymer particles having a D50 of from about 185 μm to about 25 mm.
14. The process of claim 13 , wherein the D50 is from about 300 μm to about 600 μm.
15. The process of claim 1 , wherein the copolymer has at least one end block A and at least one interior block B wherein each A block contains essentially no sulfonic acid or sulfonate functional groups and each B block is a polymer block containing from about 10 to about 100 mol-% sulfonic acid or sulfonate functional groups based on the number of monomer units of the B block.
16. The process of claim 15 , wherein each B block comprises 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.
17. The process of claim 15 , wherein the copolymer has a general configuration A-B-A, A-B-A-B-A, (A-B-A) x X, (A-B) x X, A-D-B-D-A, A-B-D-B-A, (A-D-B) x X, (A-B-D) x X or mixtures thereof, where n is an integer from 2 to about 30, and X is a coupling agent residue and wherein each D block is a polymer block resistant to sulfonation and the plurality of A blocks, B blocks, or D blocks are the same or different.
18. The process of claim 15 , wherein the copolymer comprises one or more blocks D each block D being independently 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.