Super absorbent polymer recycling to pressure sensitive adhesives
Methods for upcycling crosslinked sodium polyacrylate to pressure sensitive adhesives via (a) mechanochemical chain-shortening and esterification or (b) esterifying with high conversion with a Fischer esterification process are disclosed. Also disclosed is a pressure sensitive adhesive prepared by the disclosed methods and articles comprising the pressure sensitive adhesive, including, but not limited to, pressure sensitive tape, a bandage, a label, note pads, a decal, a stamp, an envelope, a sticker, packaging, automobile trim, and a film.
1. A method for preparing a pressure sensitive adhesive from one or more sodium polyacrylate-based superabsorbent polymers, the method comprising:
(a) providing a solution comprising one or more sodium polyacrylate-based superabsorbent polymers;
(b) decrosslinking the one or more sodium polyacrylate-based superabsorbent polymers to provide one or more decrosslinked sodium poly acrylate-based superabsorbent polymers;
(c) optionally sonicating the one or more decrosslinked sodium polyacrylate-based superabsorbent polymers to provide one or more chain-shortened sodium polyacrylate-based superabsorbent polymers;
(d) protonating the one or more decrosslinked and/or chain-shortened sodium polyacrylate-based superabsorbent polymers to provide one or more protonated decrosslinked and/or chain-shortened polyacrylic acid-based superabsorbent polymers; and
(e) esterifying the one or more protonated decrosslinked and/or chain-shortened polyacrylic acid-based superabsorbent polymers to provide a pressure sensitive adhesive.
2. The method of claim 1 , wherein the one or more sodium polyacrylate-based superabsorbent polymers are derived from a disposable personal hygiene product.
3. The method of claim 1 , wherein the decrosslinking of the one or more sodium polyacrylate-based superabsorbent polymers comprises contacting the one or more sodium polyacrylate-based superabsorbent polymers with a base to provide one or more decrosslinked sodium polyacrylate-based superabsorbent polymers.
4. The method of claim 3 , wherein the base is an inorganic base.
5. The method of claim 4 , wherein the inorganic base is selected from the group consisting of NaOH, KOH, Na 2 CO 3 , and K 2 CO 3 .
6. The method of claim 1 , wherein the protonating of the one or more decrosslinked sodium polyacrylate-based superabsorbent polymers comprises (i) contacting the one or more decrosslinked sodium polyacrylate-based superabsorbent polymers with a cation exchange resin or (ii) titrating the one or more decrosslinked sodium polyacrylate-based superabsorbent polymers with HCL or H 2 SO 4 to provide one or more protonated polyacrylic add-based superabsorbent polymers.
7. The method of claim 1 , wherein the esterifying of the one or more protonated polyacrylic acid-based superabsorbent polymers comprises contacting the one or more protonated polyacrylic acid-based superabsorbent polymers with one or more organohalide compounds.
8. The method of claim 7 , wherein the one or more organohalide compounds is selected from the group consisting of methyl iodide, ethyl iodide, n-butyl bromide, n-octyl bromide, propargyl bromide (3-bromo-1-propyne), ethyl bromoacetate, ethyl chloroacetate, (1-bromoethyl)benzene, benzyl chloride, benzyl bromide, isobutenyl chloride (3-chloro-2-methylprop-1-ene), 2-ethylhexylbromide, and 2-ethylhexylchloride.
9. The method of claim 1 , wherein the esterifying of the one or more protonated polyacrylic acid-based superabsorbent polymers comprises contacting the one or more protonated polyacrylic acid-based superabsorbent polymers with one or more promoters.
10. The method of claim 9 , wherein the one or more promoters is selected from the group consisting of 1,1,3,3-tetramethylguanidine (TMG), triethylamine, and pyridine.
11. The method of claim 1 , wherein the esterifying of the one or more protonated polyacrylic acid-based superabsorbent polymers is done in a polar aprotic solvent.
12. A method for preparing a pressure sensitive adhesive from one or more sodium polyacrylate-based superabsorbent polymers, the method comprising:
(a) providing one or more sodium polyacrylate-based superabsorbent polymers; and
(b) contacting the one or more sodium polyacrylate-based superabsorbent polymers with one or more alcohols in the presence of an acid for a period of time at a predetermined temperature to provide a pressure sensitive adhesive.
13. The method of claim 12 , wherein the one or more sodium polyacrylate-based superabsorbent polymers are derived from a disposable personal hygiene product.
14. The method of claim 12 , wherein the one or more alcohols is selected from the group consisting of 2-ethylhexanol, 3-bromopropanol, and combinations thereof.
15. The method of claim 12 , wherein the one or more alcohols is selected from 2-ethylhexanol, 3-bromopropanol, and combinations thereof.
16. The method of claim 12 , wherein the acid is selected from the group consisting of tosylic acid and sulfuric acid.
17. The method of claim 12 , wherein the one or more alcohols is present in about a 1:2 ratio relative to an acrylic acid repeat unit of the one or more sodium poly acrylate-based superabsorbent polymers.
18. The method of claim 12 , wherein the one or more alcohols is present in about a 1:1 ratio relative to an amount of water.
19. The method of claim 12 , wherein the method does not require a step of removing water.