Superabsorbent polymers and methods of making the same
View Patent ↗The invention relates to producing a superabsorbent polymer comprising (I) producing a (meth)acrylic acid comprising the steps of (a) synthesizing a crude (meth)acrylic acid phase; (b) distillatively working-up the crude (meth)acrylic acid phase to obtain a (meth)acrylic acid phase and a dimer phase comprising (meth)acrylic acid dimers and/or (meth)acrylic acid oligomers; (c) splitting at least a part of the (meth)acrylic acid dimers or of the (meth)acrylic acid oligomers or both from the dimer phase to obtain a (meth)acrylic acid-comprising a low boiling phase and a high boiling phase comprising less (meth)acrylic acid than the low boiling phase; (d) separating at least a part of the (meth)acrylic acid from the low boiling phase by forming crystals to obtain a pure (meth)acrylic acid, and a residue; (II) polymerizing a monomer phase comprising the pure (meth)acrylic acid to obtain a polymer phase; and (III) working-up the polymer phase to obtain the polymer.
1. A superabsorbent polymer made by the process comprising the steps of:
I. a) producing crude (meth)acrylic acid phase wherein crude (meth)acrylic acid comprises from about 1 to about 80 wt % of (meth)acrylic acid; wherein said producing crude (meth)acrylic acid phase is selected from the group consisting of gas phase oxidation, and dehydration of an organic molecule having at least one OH-group wherein the organic molecule is selected from the group consisting of glycerine, lactic acid and β-hydroxypropionic acid;
b) distilling the (meth)acrylic acid phase of a) to obtain a (meth)acrylic acid phase, and a dimer phase comprising (meth)acrylic acid dimers or (meth)acrylic acid oligomers or both;
c) splitting at least a part of the (meth)acrylic acid dimers or of the (meth)acrylic acid oligomers or both from the dimer phase to obtain a (meth)acrylic acid-comprising low boiling phase, and a high boiling phase comprising less (meth)acrylic acid than the low boiling phase, wherein said high boiling phase is discarded;
d) separating at least a part of the (meth)acrylic acid from the low boiling phase by forming one or more crystals to obtain a pure (meth)acrylic acid and a residue;
II. polymerizing the pure (meth)acrylic acid in the presence of a cross linker to obtain a superabsorber polymer phase; and
III. working-up the polymer phase to obtain the superabsorber polymer.
2. The superabsorbent polymer according to claim 1 , further comprising the step of I. e) crystallizing the residue of step d) into a (meth)acrylic acid-rich phase, and an impurity phase.
3. The superabsorbent polymer according to claim 1 , wherein at least a part of the low boiling phase in step d) is provided as fluid film over a cold source.
4. The superabsorbent polymer according to claim 1 , wherein at least a part of the fluid film comprises a falling film.
5. The superabsorbent polymer according to claim 1 , wherein the cold source comprises an at least partially planar form.
6. The superabsorbent polymer according to claim 1 , wherein at least a part of the crystals are subjected to a sweating.
7. The superabsorbent polymer according to claim 1 , wherein the crystals are melted after the sweating.
8. The superabsorbent polymer according to claim 1 , wherein the distillative work-up according to step b) occurs in at least two distillation steps following each other.
9. The superabsorbent polymer according to claim 1 , wherein the splitting according to step c) occurs thermally.
10. The superabsorbent polymer according to claim 1 , wherein the splitting according to step c) occurs under a pressure which is different from the ambient pressure.
11. The superabsorbent polymer according to claim 2 wherein the (meth)acrylic acid-rich phase is at least partially supplied to process step d).
12. The superabsorbent polymer according to claim 1 wherein the organic molecule is lactic acid.
13. The superabsorbent polymer according to claim 1 wherein the organic molecule is β-hydroxypropionic acid.