Highly-absorbent starch-containing polymeric compositions
AssigneeThe United States of America as represented by the Secretary of Agriculture
InventorsMary Ollidene Weaver, Edward B. Bagley, George F. Fanta, William M. Doane
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Abstract
Starch-containing polymer compositions are prepared which absorb amounts of water equaling up to more than 1000 times their own weight. The compositions find many applications including their incorporation into products such as disposable diapers, surgical pads and sheets, and paper towels.
Claims15
Aqueous fluid-absorbing compositions comprising water-insoluble alkali salts of aqueous alkali saponified gelatinized-starch-polyacrylonitrile graft polymers containing gelatinized starch (GS) and saponified polyacrylonitrile (HPAN) in molar ratios of from about 1:1.5 to 1:9 GS:HPAN, said water-insoluble alkali salts of aqueous alkali saponified gelatinized-starch-polyacrylonitrile graft polymers being further characterized as water-insoluble solids capable of absorbing in excess of 300 parts of water by weight per part of said water-insoluble solids.
A method of preparing water-insoluble aqueous fluid-absorbing compositions comprising the following steps:
- a. saponifying a gelatinized-starch-polyacrylonitrile graft polymer (GS-PAN) in an aqueous slurry with an alkali in amounts such that the molar ratio of alkali to the acrylonitrile repeating unit of said GS-PAN is from about 0.1:1 to 7:1 to form a water-soluble saponified GS-PAN (water-soluble GS-HPAN);
- and
- b. optionally adjusting the pH of said water-soluble GS-HPAN to about 3, followed by isolating the resulting water-insoluble acid form of GS-HPAN, and readjusting the pH of said water-insoluble acid form of GS-HPAN to from about 4 to 12 to reform said water-soluble GS-HPAN;
- and
- c. drying said water-soluble GS-HPAN to a moisture level of from about 1 to 15% water by weight.
A method of preparing insoluble aqueous-organic fluid-absorbing compositions comprising the steps of:
- a. saponifying a gelatinized-starch-polyacrylonitrile graft polymer (GS-PAN) in an aqueous slurry with an alkali in amounts such that the molar ratio of alkali to acrylonitrile repeating units of said GS-PAN is from about 0.1:1 to 7:1 to form a water-soluble saponified GS-PAN (water-soluble GS-HPAN);
- b. adjusting the pH of said water-soluble GS-HPAN to about 3, followed by isolating the resulting water-insoluble acid form of GS-HPAN;
- c. reacting said water-insoluble acid form of GS-HPAN in an aqueous slurry with an organic amine in amounts such that the pH of the reaction mixture is from 5 to 11;
- and
- d. drying the product of step (c) to a moisture content of about 1 to 15% water by weight.
A method of preparing a low viscosity aqueous dispersion of a water-soluble saponified gelatinized-starch-polyacrylonitrile graft polymer capable of forming a water-insoluble aqueous, fluid-absorbing composition comprising the steps of:
- a. saponifying a gelatinized-starch-polyacrylonitrile graft polymer (GS-PAN) in an aqueous slurry with an alkali in amounts such that the molar ratio of alkali to the acrylonitrile repeating unit of said GS-PAN is from about 0.0:1 to 7:1 to form a water-soluble saponified GS-PAN (water-soluble GS-HPAN);
- and
- b. optionally adjusting the pH of said water-soluble GS-HPAN to about 3, followed by isolating the resulting water-insoluble acid form of GS-HPAN, and readjusting the pH of said water-insoluble acid form of GS-HPAN to form about 4 to 12 to reform said water-soluble GS-HPAN;
- and
- c. sonifying a 1% by weight aqueous dispersion of said water-soluble GS-HPAN at a sonifying frequency and for a time sufficient to reduce the viscosity of said dispersion to about 30 cp.
A method of increasing the water absorbency of water-insoluble substrates comprising the steps of:
- a. saponifying a gelatinized-starch-polyacrylonitrile graft polymer (GS-PAN) in an aqueous slurry with an alkali in amounts such that the molar ratio of alkali to the acrylonitrile repeating unit of said GS-PAN is from about 0.1:1 to 7:1 to form a water-soluble saponified GS-PAN (water-soluble GS-HPAN);
- and
- b. optionally adjusting the pH of said water-soluble GS-HPAN to about 3, followed by isolating the resulting water-insoluble acid form of GS-HPAN, and readjusting the pH of said water-insoluble acid form of GS-HPAN to from about 4 to 12 to reform said water-soluble GS-HPAN;
- and
- c. mixing said water-soluble GS-HPAN in an aqueous slurry of a water-insoluble substrate;
- and
- d. drying the mixture resulting from step (c) to a moisture content of 1 to 15% water by weight.
Dependencies are inferred from the claim text.