Color-stable superabsorbent polymer composition
AssigneeBASF SE
InventorsNorbert Herfert, Michael M. Azad, Peter W. Carrico, Guy Thomas Woodrum, Michael A. Mitchell, Ma-Ikay Kikama Miatudila
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Abstract
A color-stable superabsorbent polymer having long-term color stability, and methods of manufacturing the polymer, are disclosed. The superabsorbent polymer is prepared using a sulfinic acid derivative, like 2-hydroxy-2-sulfinatoacetic acid, a salt thereof, or a mixture thereof, as the reducing agent in a polymerization initiator system for the preparation of a superabsorbent polymer from monomers. The resulting superabsorbent polymer resists color degradation during periods of extended storage, even at an elevated temperature and humidity.
Claims31
A method of manufacturing color-stable superabsorbent polymer particles comprising the steps of:
- (a) forming a monomer mixture comprising:
- (i) at least one monomer capable of forming a superabsorbent polymer,
- (ii) a crosslinking agent,
- (iii) an initiator system comprising a sulfinic acid derivative having a structure
- wherein M is hydrogen, an ammonium ion, or a monovalent or a divalent metal ion of groups Ia, IIa, IIb, IVa, and VIIIb of the Periodic Table of the Elements;
- R1 is OH or NR4R5, wherein R4 and R5, independently, are H or C1-C6alkyl;
- R2 is H or an alkyl, alkenyl, cycloalkyl, or aryl group, optionally having 1-3 substituents independently selected from the group consisting of C1-C6alkyl, OH, O—C1-C6alkyl, halogen, and CF3;
- and
- R3 is COOM, SO3M, COR4, CONR4R5, or COOR4, wherein M, R4, and R5 are as defined above, or, if R2 is unsubstituted or unsubstituted aryl, R3 is H;
- and the salts thereof;
- or a mixture thereof;
- (iv) an optional photoinitiator, and
- (v) water;
- (b) polymerizing the monomer and the crosslinking agent in the monomer mixture to form a superabsorbent polymer hydrogel;
- (c) optionally subjecting the superabsorbent polymer hydrogel to a low dose of UV radiation;
- (d) comminuting the superabsorbent polymer hydrogel to provide superabsorbent hydrogel particles;
- and
- (e) drying the superabsorbent polymer hydrogel particles for a sufficient time at a sufficient temperature to provide the color-stable superabsorbent polymer particles, wherein the color-stable SAP particles, after storage for 30 days at 60° C. and 90% relative humidity, exhibit an HC60 color value of at least 60 and a maximum b-value of 10.
Dependencies are inferred from the claim text.