Water-absorbing polysaccharide and method for producing the same

A polysaccharide superabsorbent polymer particulate comprising:

• a. a polysaccharide polymer crosslinked with a polyphosphate or polyphosphoric acid as a crosslinking agent to form a polysaccharide polymer gel which is formed into a polysaccharide polymer particulate having a particle size ranging from about 150 μm to about 850 μm;
• b. a surface crosslinking agent selected from a polyphosphate or polyphosphoric acid forming crosslinks of the surface crosslinking agent and the polysaccharide superabsorbent polymer particulate resulting in a surface crosslinked polysaccharide superabsorbent polymer particulate wherein the level of functional cross links in the vicinity of the surface of the polysaccharide superabsorbent polymer particulate is greater than the level of functional cross links in the interior of the polysaccharide superabsorbent polymer particulate;
• and
• c. a post-crosslinking agent selected from a water soluble multivalent metal salt or an acid wherein the water soluble multivalent metal salt includes a metal cation selected from Al, Fe, Zr, Mg, or Zn and the acid is selected from phosphoric acid, acetic acid, lactic acid, citric acid, glyconic acid and gluconic acid wherein the post-crosslinking agent is applied to the surface of the surface crosslinked polysaccharide superabsorbent polymer particulate to form polysaccharide superabsorbent polymer particulate;
• wherein the polysaccharide superabsorbent polymer particulate has a permeability half life of between about 30 days and about 180 days and an absorption under load at 0.9 psi of from about 10 g/g to about 20 g/g as measured by the Absorbency Under Load (AUL0.9 psi) Test.

A superabsorbent material comprising:

• a. from about 1 to about 40 wt % of a polysaccharide superabsorbent polymer particulate having a permeability half life of between about 30 days and about 180 days and an absorption under load at 0.9 psi of from about 10 g/g to about 20 g/g as measured by the Absorbency Under Load (AUL0.9 psi) Test, wherein the polysaccharide superabsorbent polymer particulate comprises
• i) a polysaccharide polymer crosslinked with a polyphosphate or polyphosphoric acid as a crosslinking agent to form a polysaccharide polymer gel which is formed into a polysaccharide polymer particulate having a particle size ranging from about 150 μm to about 850 μm;
• ii). a surface crosslinking agent selected from a polyphosphate or polyphosphoric acid forming crosslinks of the surface crosslinking agent and the polysaccharide superabsorbent polymer particulate resulting in a surface crosslinked polysaccharide superabsorbent polymer particulate;
• and
• iii). a post-crosslinking agent selected from a water soluble multivalent metal salt or an acid wherein the water soluble multivalent metal salt includes a metal cation selected from Al, Fe, Zr, Mg, or Zn and the acid is selected from phosphoric acid, acetic acid, lactic acid, citric acid, glyconic acid and gluconic acid wherein the post-crosslinking agent is applied to the surface crosslinked polysaccharide superabsorbent polymer particulate to form polysaccharide superabsorbent polymer particulate;
• and
• b. from about 60 to about 99 wt % of a second superabsorbent polymer particulate that is different from the polysaccharide superabsorbent polymer particulate.

An absorbent article comprising a polysaccharide superabsorbent polymer particulate comprising:

• a. a polysaccharide polymer crosslinked with a polyphosphate or polyphosphoric acid as a crosslinking agent to form a polysaccharide polymer gel which is formed into a polysaccharide polymer particulate having a particle size ranging from about 150 μm to about 850 μm;
• b. a surface crosslinking agent selected from a polyphosphate or polyphosphoric acid forming crosslinks of the surface crosslinking agent and the polysaccharide superabsorbent polymer particulate resulting in a surface crosslinked polysaccharide superabsorbent polymer particulate;
• and
• c. a post-crosslinking agent selected from a water soluble multivalent metal salt or an acid wherein the water soluble multivalent metal salt includes a metal cation selected from Al, Fe, Zr, Mg, or Zn and the acid is selected from phosphoric acid, acetic acid, lactic acid, citric acid, glyconic acid and gluconic acid wherein the post-crosslinking agent is applied to the surface crosslinked polysaccharide superabsorbent polymer particulate to form polysaccharide superabsorbent polymer particulate and wherein the polysaccharide superabsorbent polymer particulate has a permeability half life of between about 30 days and about 180 days and an absorption under load at 0.9 psi of from about 10 g/g to about 20 g/g as measured by the Absorbency Under Load (AUL0.9 psi) Test.

A process for producing surface treated polysaccharide superabsorbent polymer particles, comprising the steps of:

• i. mixing a polysaccharide with a polyphosphate or polyphosphoric acid as a crosslinking agent in the presence of water to form a polysaccharide gel;
• ii. drying the polysaccharide gel;
• iii. comminuting the dried polysaccharide gel to form dried polysaccharide superabsorbent polymer particles having a particle size ranging from about 150 μm to about 850 μm as measured by screening through a U.S. standard 20 mesh screen and retained on a U.S. standard 100 mesh screen;
• iv. coating the polysaccharide superabsorbent polymer particles with a polyphosphate or polyphosphoric acid as a crosslinking agent
• v. heating the coated polysaccharide superabsorbent polymer particles to affect surface crosslinking of the coated polysaccharide superabsorbent polymer particle surface wherein the level of functional cross links in the vicinity of the surface of the polysaccharide superabsorbent polymer particulate is greater than the level of functional cross links in the interior of the polysaccharide superabsorbent polymer particulate;
• and
• vi. treating the surface of the dried polysaccharide superabsorbent polymer particles with a post-crosslinking agent selected from a water soluble multivalent metal salt or an acid wherein the water soluble multivalent metal salt includes a metal cation selected from Al, Fe, Zr, Mg, or Zn and the acid is selected from phosphoric acid, acetic acid, lactic acid, citric acid, glyconic acid and gluconic acid wherein the post-crosslinking agent is applied to the surface of the surface crosslinked polysaccharide superabsorbent polymer particulate to form polysaccharide superabsorbent polymer particulate wherein the polysaccharide superabsorbent polymer particulate has a permeability half life of between about 30 days and about 180 days and an absorption under load at 0.9 psi of from about 10 g/g to about 20 g/g as measured by the Absorbency Under Load (AUL0.9 psi) Test.