Water-absorbing polymer structures based on renewable raw materials and process for their production by dehydration

1. A superabsorbent polymer comprising:

i) acrylic acid, wherein said acrylic acid is made by the process comprising the steps of:

A heating an aqueous glycerine solution before entry into a dehydration reactor to a temperature of from 250° C. to 310° C. to form glycerine;

B transporting the glycerine of step A to the dehydration reactor;

C dehydrating the glycerine of step B to an acrolein-comprising dehydration product wherein the dehydrating occurs along a path wherein the glycerine concentration decreases, wherein along this path a pressure change occurs, and different flow rates exist;

D gas phase oxidating of the acrolein-comprising dehydration product to obtain an acrylic acid-comprising monomer gas;

E bringing into contact of the monomer gas with a quench agent to obtain an acrylic acid-comprising quench phase;

F working-up the quench phase to obtain an acrylic acid-comprising monomer phase; and

G polymerizing the acrylic acid-comprising monomer phase;

wherein at least about 25% of the acrylic acid is based on glycerine; and

ii) allyloxypolyethyleneglycol acrylic acid ester;

wherein during the dehydration a liquid phase al and a gas phase a2 is present;

wherein in the liquid phase a1, a plurality of gas bubbles is generated;

wherein the dehydration occurs at least partially in the liquid phase;

wherein the superabsorbent polymer has a biodegradability determined according to the modified Sturm-test according to appendix V to Guideline 67/548/EEC after 28 days of at least 25%; and

wherein the superabsorbent polymer has a sustainability factor of at least about 80%.

2. The superabsorbent polymer according to claim 1 with at least one of the following properties:

a) a Saline Flow Conductivity (SFC) determined according to the herein-described test method of more than 30×10 −7 cm 3 s/g;

b) an Absorption Against a Pressure of 0.7 psi (AAP 0.7 ) determined according to ERT 442.2-02 of more than 20 g/g; or

c) a Retention (CRC) determined according to ERT 441.2-02 of at least 20 g/g.

3. The superabsorbent polymer according to claim 1 wherein the superabsorbent polymer is based to at least 20 wt. %, based on the total weight of the superabsorbent polymer, on natural biodegradable polymers.

4. The superabsorbent polymer according to claim 1 further comprising a plurality of inorganic fine particles.

5. The superabsorbent polymer according to claim 4 wherein the inorganic fine particles comprise oxygen.

6. The superabsorbent polymer according to claim 4 wherein the inorganic fine particles comprise a metal.

7. The superabsorbent polymer according to claim 1 wherein the superabsorbent polymer comprises a post-crosslinked outer region.

8. The superabsorbent polymer according to claim 7 wherein the inorganic fine particles are provided on or in the outer region.

9. A composite comprising the superabsorbent polymer according to claim 1 and a substrate.

10. A hygiene article comprising a top-sheet, a bottom-sheet and a between-sheet arranged between the top-sheet and the bottom-sheet, which comprises the superabsorbent polymer according to claim 1