Method of makig a superabsorbent polymer foam

Claim 1

A method of making an open-celled superabsorbent polymer foam, the method comprising the steps of: (I) forming a reaction mixture comprising: (a) a substantially water-soluble unsaturated monomer comprising neutralized carboxyl groups; (b) a substantially water-soluble internal crosslinking agent capable of reacting with said monomer to form a superabsorbent polymer material; and (c) a solvent selected from the group consisting of water, a substantially water-soluble solvent, and mixtures thereof; (II) dispersing a substantially water-insoluble blowing agent in said reaction mixture to form a dispersion of particles of said blowing agent in said reaction mixture, said blowing agent having a vaporization temperature at a pressure of 1 atmosphere in the range of about -20° C. to about 100° C.; (III) stabilizing said dispersion to form a stable dispersion of said blowing agent particles in said reaction mixture; (IV) expanding said blowing agent particles to form an expanded structure, wherein said expansion step comprises: (a) increasing the temperature of said stable dispersion to a temperature which is greater than or equal to the vaporization temperature of said blowing agent, less than or equal to the activation temperature of said reaction mixture, and less than the vaporization temperature of said solvent; and/or (b) decreasing the pressure on said stable dispersion; (V) reacting said monomer and said internal crosslinking agent to form a superabsorbent polymer material; and (VI) controlling said dispersion step (II), said stabilization step (III), said expansion step (IV) and said reaction step (V) to form a superabsorbent polymer foam comprising a plurality of mutually connected struts of said superabsorbent polymer material to form open cells such that the foam has: (a) a surface area to mass ratio of at least about 0.2 m 2 /g; (b) an average cell size of less than about 100 microns; and (c) a density of less than about 0.5 g/cm 3 .

Claim 2

A method of making an open-celled superabsorbent polymer foam, the method comprising the steps of: (I) forming a reaction mixture comprising: (a) a substantially water-soluble unsaturated monomer comprising neutralized carboxyl groups; (b) a substantially water-soluble internal crosslinking agent capable of reacting with said monomer to form a superabsorbent polymer material; and (c) a solvent selected from the group consisting of water, a substantially water-soluble solvent, and mixtures thereof; (II) dispersing a substantially water-insoluble blowing agent in said reaction mixture to form a dispersion of particles of said blowing agent in said reaction mixture, said blowing agent having a vaporization temperature at a pressure of 1 atmosphere in the range of about -20° C. to about 100° C.; (III) stabilizing said dispersion to form a stable dispersion of said blowing agent particles in said reaction mixture; (IV) expanding said blowing agent particles to form an expanded structure, wherein said expansion step comprises: (a) increasing the temperature of said stable dispersion to a temperature which is greater than or equal to the vaporization temperature of said blowing agent, less than or equal to the activation temperature of said reaction mixture, and less than the vaporization temperature of said solvent; and/or (b) decreasing the pressure on said stable dispersion; (V) reacting said monomer and said internal crosslinking agent to form a superabsorbent polymer material; and (VI) controlling said dispersion step (II), said stabilization step (III), said expansion step (IV) and said reaction step (V) to form a superabsorbent polymer foam comprising a plurality of mutually connected struts of said superabsorbent polymer material to form open cells such that the foam has: (a) a surface area to mass ratio of at least about 0.2 m 2 /g; (b) an average cell size of less than about 100 microns; and (c) a density of less than about 0.5 g/cm 3 .

Claim 21

A method of making an open-celled superabsorbent polymer foam; the method comprising the steps of: (I) forming a reaction mixture comprising: (a) a substantially water-soluble unsaturated monomer comprising neutralized carboxyl groups; (b) a substantially water-soluble internal crosslinking agent capable of reacting with said monomer to form a substantially water-insoluble polymer material; and (c) a solvent selected from the group consisting of water, a substantially water-soluble solvent, and mixtures thereof; said reaction mixture having a critical temperature and an activation temperature, said critical temperature being less than said activation temperature; (II) dispersing a blowing agent in said reaction mixture to form a dispersion of particles of said blowing agent in said reaction mixture, said blowing agent being substantially insoluble in said solvent and having a vaporization temperature at a pressure of 1 atmosphere in the range of about -20° C. to about 100° C.; (III) stabilizing said dispersion to form a stable dispersion of said blowing agent particles in said reaction mixture; (IV) expanding said blowing agent particles to form an expanded structure, wherein said expansion step comprises: (a) increasing the temperature of said stable dispersion to a temperature which is greater than or equal to the vaporization temperature of said blowing agent, less than or equal to said critical temperature, and less than the vaporization temperature of said solvent; and/or (b) decreasing the pressure on said stable dispersion; (V) reacting said monomer and said internal crosslinking agent to form a substantially water-insoluble polymer material by heating said expanded structure to a temperature which is greater than or equal to said critical temperature and less than said activation temperature; (VI) controlling said dispersion step (II), said stabilization step (III), said expansion step (IV) and said reaction step (V) to form a polymer foam comprising a plurality of mutually connected struts of said substantially water-insoluble polymer material to form cells; and (VII) reacting said substantially water-insoluble polymer material of said polymer foam to form a superabsorbent polymer foam comprising a plurality of mutually connected struts of superabsorbent polymer material to form cells, said reaction to form a superabsorbent polymer foam comprising: (a) heating said substantially water-insoluble polymer material to at least said activation temperature; and/or (b) reacting said substantially water-insoluble polymer material with an external crosslinking agent; the superabsorbent polymer foam having: (a) a surface area to mass ratio of at least about 0.2 m 2 /g; (b) an average cell size of less than about 100 microns; and (c) a density of less than about 0.5 g/cm 3 .

Claim 22

A method of making an open-celled superabsorbent polymer foam; the method comprising the steps of: (I) forming a reaction mixture comprising: (a) a substantially water-soluble unsaturated monomer comprising neutralized carboxyl groups; (b) a substantially water-soluble internal crosslinking agent capable of reacting with said monomer to form a substantially water-insoluble polymer material; and (c) a solvent selected from the group consisting of water, a substantially water-soluble solvent, and mixtures thereof; said reaction mixture having a critical temperature and an activation temperature, said critical temperature being less than said activation temperature; (II) dispersing a blowing agent in said reaction mixture to form a dispersion of particles of said blowing agent in said reaction mixture, said blowing agent being substantially insoluble in said solvent and having a vaporization temperature at a pressure of 1 atmosphere in the range of about -20° C. to about 100° C.; (III) stabilizing said dispersion to form a stable dispersion of said blowing agent particles in said reaction mixture; (IV) expanding said blowing agent particles to form an expanded structure, wherein said expansion step comprises: (a) increasing the temperature of said stable dispersion to a temperature which is greater than or equal to the vaporization temperature of said blowing agent, less than or equal to said critical temperature, and less than the vaporization temperature of said solvent; and/or (b) decreasing the pressure on said stable dispersion; (V) reacting said monomer and said internal crosslinking agent to form a substantially water-insoluble polymer material by heating said expanded structure to a temperature which is greater than or equal to said critical temperature and less than said activation temperature; (VI) controlling said dispersion step (II), said stabilization step (III), said expansion step (IV) and said reaction step (V) to form a polymer foam comprising a plurality of mutually connected struts of said substantially water-insoluble polymer material to form cells; and (VII) reacting said substantially water-insoluble polymer material of said polymer foam to form a superabsorbent polymer foam comprising a plurality of mutually connected struts of superabsorbent polymer material to form cells, said reaction to form a superabsorbent polymer foam comprising: (a) heating said substantially water-insoluble polymer material to at least said activation temperature; and/or (b) reacting said substantially water-insoluble polymer material with an external crosslinking agent; the superabsorbent polymer foam having: (a) a surface area to mass ratio of at least about 0.2 m 2 /g; (b) an average cell size of less than about 100 microns; and (c) a density of less than about 0.5 g/cm 3 .