DIJAKOV NATASA (DE)
COLLIAS DIMITRIS (US)
JAMES MARTIN (US)
SUN YIPING (US)
STONEHOUSE JONATHAN (GB)
THOMAS JACQUELINE (US)
GILBERTSON GARY (US)
| WO2004020008A1 | 2004-03-11 | |||
| WO2000059430A1 | 2000-10-12 | |||
| WO1995010996A1 | 1995-04-27 | |||
| WO2002067809A2 | 2002-09-06 |
| US7329701B2 | 2008-02-12 | |||
| EP1621561A1 | 2006-02-01 | |||
| USPP62890631P | ||||
| USPP62890632P | ||||
| US201916548873A | 2019-08-23 | |||
| USPP62890880P | ||||
| EP19193221A | 2019-08-23 | |||
| USPP63039496P | ||||
| USPP63039498P | ||||
| US5700254A | 1997-12-23 | |||
| US7786341B2 | 2010-08-31 | |||
| US20030105190A1 | 2003-06-05 | |||
| EP2535027A1 | 2012-12-19 |
W. WILLKERD. LEIBFRITZR. KERSSEBAUMW. BERMEL, MAGN. RESON. CHEM., vol. 31, 1993, pages 287 - 292
| CLAIMS What is claimed is: 1. Method of making superabsorbent polymer material. The method comprises the steps of a) providing an aqueous solution of polymerizable acrylic acid monomers and/or polymerizable acrylic acid oligomers, optionally neutralizing at least some of the polymerizable acrylic acid monomers and/or polymerizable acrylic acid oligomers; b) optionally providing one or more ethylenically unsatured co-monomers, optionally neutralizing at least some of the ethylenically unsatured co-monomer of step b); c) optionally providing one or more crosslinker(s); d) providing one or more initiator(s); e) providing soluble polyacrylic acid polymers, wherein the soluble polyacrylic acid polymers have a molar percent of carbon-to-carbon double bonds of at least 0.03, preferably at least 0.05, more preferably at least 0.08, still more preferably at least 0.1; f) mixing the aqueous solution of monomers, oligomers, co-monomers, crosslinkers and initiators and soluble polyacrylic acid polymers provided in steps a) to e); and g) polymerizing the mixture obtained in step f) to obtain a superabsorbent polymer. 2. Method of claim 1, wherein the soluble polyacrylic acid polymers provided in step e) are provided at a weight-percent of at least 3 weight-%, preferably at least 5 weight-% based on the total weight of the soluble polyacrylic acid polymers provided in step e) and the monomers, oligomers, co-monomers, crosslinkers and initiators provided in steps a) to d). 3. Method of claim 1 or 2, wherein the soluble polyacrylic acid polymers provided in step e) are provided at a weight-percent of up to 60.0 weight-%, or up to 50.0 weight-%, based on the total weight of the soluble polyacrylic acid polymers provided in step e) and the monomers, oligomers, co-monomers, crosslinkers and initiators provided in steps a) to d). 4. Method of any of the preceding claims, wherein the method further comprises a step h) of drying the superabsorbent polymer material. 5. Method of any of the preceding claims, further comprising a step i) of comminuting the superabsorbent polymer material to obtain superabsorbent polymer particles. 6. Method of claim 5, further comprising the step of surface cross-linking the superabsorbent polymer particles. 7. Method of any of the preceding claims, wherein the soluble polyacrylic acid polymers are obtained from pre-existing recycled post-consumer superabsorbent polymer material, and/or obtained from pre-existing recycled post-industrial superabsorbent polymer material. 8. Method of any of claim 7, wherein the method further comprises the step of a1) obtaining the soluble polyacrylic acid polymers from pre-existing recycled post-consumer superabsorbent polymer material or from pre-existing recycled post-industrial superabsorbent polymer material by chemical degradation of the pre-existing recycled post-consumer superabsorbent polymer material, and wherein step a1) is carried out prior to step b). 9. Method of claim 8, wherein the chemical degradation is carried out with an oxidative water-soluble salt comprising at least one cation and at least one anion. 10. Method of claim 9, wherein the at least one anion is selected from the group consisting of: peroxydisulfate, peroxymonosulfate, peroxydicarbonate, peroxydiphosphate, peroxydiborate and mixtures and combinations thereof. 11. Method of claim 8, wherein the chemical degradation is mediated by redox couples, wherein the redox couples are selected from the group consisting of sodium peroxodisulfate/ascorbic acid; hydrogen peroxide/ascorbic acid; potassium peroxodisulfate /sodium bisulfite; sodium peroxodisulfate/sodium bisulfite; hydrogen peroxide/sodium bisulfite; potassium peroxodisulfate /ascorbic acid and combinations thereof. 12. Method of any of the preceding claims, wherein the soluble polyacrylic acid polymers have a weight average molecular weight Mw of from 500 kDa to 3 MDa, preferably from 100 kDa to 1 MDa. 13. Method of any of the preceding claims, wherein the superabsorbent polymer material obtained by the method has an amount of extractables of less than 15.0 weight-% based on the total weight of the superabsorbent polymer material, and the ratio of amount of the difference between extractables (weight-%) and s-PAA polymer add-on (%wt), to capacity (g/g) to less than 0.15. 14. Method of any of the preceding claims, wherein the superabsorbent polymer material obtained by the method has a capacity measured as Centrifuge Retention Capacity (CRC) in accordance the test method set out herein of at least 20 g/g. 15. Superabsorbent polymer material comprising cross-linked polyacrylic acid and salts thereof, the superabsorbent polymer material comprising polyacrylic acid as internal cross-linkers of the network. 16. Superabsorbent polymer material of claim 15 wherein polyacrylic acid are the only internal cross-linkers of the network. 17. Superabsorbent polymer material of any of claims 15 or 16, wherein the superabsorbent polymer material is in the form of superabsorbent polymer particles. 18. Superabsorbent polymer material of any of claims 15 to 17, wherein the superabsorbent polymer particles are surface cross-linked. 19. Superabsorbent polymer material of any of claims 15 to 18, wherein the superabsorbent polymer material has an amount of extractables of less than 15.0 weight-% based on the total weight of the superabsorbent polymer material. 20. Absorbent article comprising the superabsorbent polymer material of any of the preceding claims. 21. Method of any of claims 1 to 14, wherein the superabsorbent polymer material obtained by the method is a superabsorbent polymer material of any of claims 15 to 19. |
Preparation of Base Polymer BP C1/7 of Comparative Examples C1 and C7 A 20,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was charged with about 5097.0 g of ice (ca. 50% of the total amount of ice: 9676.1 g ice prepared from deionized water). A magnetic stirrer, capable of mixing the whole content (when liquid), was added and stirring was started. About 200.0 g of deionized water was taken to dissolve 5.181 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass beaker of 250 mL volume. The vessel with the “KPS” solution was closed and set aside. About 10.0 g of deionized water was taken to dissolve 0.112 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. 200.0 g of deionized water was taken to dissolve 33.589 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The full amount of 4600.3 g of glacial AA (= acrylic acid) was added to the ice in the resin kettle while stirring was continued. A thermometer was introduced and in total 3472.6 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) and the remaining amount of ice (prepared from de-ionized water) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of AA, NaOH solution and ice at a temperature below 30°C while stirring was continued. The beaker that contained the “PEG700-DA” solution was washed 2x with deionized water in an amount of about 10% of the “PEG700-DA” solution volume per wash. The wash water of both washing steps was added to the stirred mixture. Deionized water (the remaining amount required to achieve the total amount of (ice + water) of 11888.3 g was added to the stirred mixture. Then, the resin kettle was closed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 – 600 RPM. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about 1 hour of Argon purging and stirring, the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter, about 0.022 g of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then also added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Within 5 min of “KPS” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 80°Cwithin 60 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was ground with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Preparation of Base Polymer BP C2 of Comparative Example C2 A 20,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was charged with about 4528.9 g of ice (ca. 50% of the total amount of ice: 8941.1 g ice prepared from deionized water). A magnetic stirrer, capable of mixing the whole content (when liquid), was added and stirring was started. About 200.0 g of deionized water was taken to dissolve 5.177 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass beaker of 250 mL volume. The vessel with the “KPS” solution was closed and set aside. About 10.0 g of deionized water was taken to dissolve 1.124 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. 200.0 g of deionized water was taken to dissolve 80.44 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The full amount of 4600.0 g of glacial AA (= acrylic acid) was added to the ice in the resin kettle while stirring was continued. A thermometer was introduced and in total 3472.7 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) and the remaining amount of ice (prepared from de-ionized water) were added subsequently in portions such that the temperature is below 30°C. The “PEG700-DA” solution was added to the mixture of AA, NaOH solution and ice at a temperature below 30°C while stirring is continued. The beaker that contained the “PEG700- DA” solution was washed 2x with deionized water in an amount of about 10% of the “PEG700- DA” solution volume per wash. The wash water of both washing steps was added to the stirred mixture. The remaining amount of deionized water required to achieve the total amount of (ice + water) of 11838.6 g was added to the stirred mixture. Then, the resin kettle was closed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about 1 hour of Argon purging and stirring, the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter, about 0.25 g of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then also added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 2 min of “KPS” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 80°C within 60 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Preparation of Base Polymer BP C3 of Comparative Example C3 A 2,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was placed into an ice bath filled with about 1 liter of water, 100 g of sodium chloride and about 200 g of ice such that the mixture covers about half the height of the resin kettle. The resin kettle was charged with about 80.0 g of solution comprising aqueous polyacrylic acid (s-PAA polymer) of about 35%w concentration wherein the weight average molecular weight Mw reported by the supplier Sigma Aldrich is 100,000 Da. About 591.4 g water was added as ice prepared from DI water and DI water of weight about 443.6 g was also added to the mixture. A magnetic stirrer, capable of mixing the whole content, was added and stirring was started. As the PAA was fully dispersed, the full amount of 432.5 g of glacial AA (= acrylic acid) was added to the PAA solution in the resin kettle while stirring was continued. About 20.0 g of deionized water was taken to dissolve 0.4870 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “KPS” solution was closed with a plastic snap-on cap and set aside. About 10.0 g of deionized water was taken to dissolve 0.053 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. About 70 g of deionized water was taken to dissolve 3.15 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a 100 mL glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The remaining water up to a final weight of 1136.3 g was added to the resin kettle and stirring was continued as a homogeneous solution was obtained within 1-5 minutes. A thermometer was introduced and in total 347.5 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of PAA, AA and NaOH solution at a temperature below 30°C while stirring was continued. Then, the resin kettle was closed, the ice bath underneath removed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about 1 hour of Argon purging and stirring, about 0.026 g (about 1-2 droplets) of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 3 min of “ASC” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 70°C within 60 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was below about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Preparation of Base Polymer BP C4 of Comparative Example C4 A 10,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was charged with about 2392.1 g of ice (ca. 60% of the total amount of ice: 3622.5 g ice prepared from deionized water). A magnetic stirrer, capable of mixing the whole content (when liquid), was added and stirring was started. About 100.0 g of deionized water was taken to dissolve 2.296 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass beaker of 250 mL volume. The vessel with the “KPS” solution was closed and set aside. About 10.0 g of deionized water was taken to dissolve 0.492 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. 200.0 g of deionized water was taken to dissolve 14.71 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The full amount of 2020.3 g of glacial AA (= acrylic acid) was added to the ice in the resin kettle while stirring was continued. An amount of 798.5 g of solution (Sigma Aldrich) comprising aqueous polyacrylic acid of about 35%w concentration wherein the weight average molecular weight Mw as reported by the supplier Sigma Aldrich is 100,000 Da, was added to the mixture in the resin kettle while stirring was continued. A thermometer was introduced and in total 1735.5 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) and the remaining amount of ice (prepared from de-ionized water) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of AA, NaOH solution and ice at a temperature below 30°C while stirring was continued. The beaker that contained the “PEG700-DA” solution was washed 2x with deionized water in an amount of about 10% of the “PEG700-DA” solution volume per wash. The wash water of both washing steps was added to the stirred mixture. Deionized water (the remaining amount required to achieve the total amount of (ice + water) of 5429.5 g was added to the stirred mixture. Then, the resin kettle was closed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about 1 hour of Argon purging and stirring, the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter, about 0.99 g of 1%w aqueous solution of hydrogen peroxide H2O2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then also added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 2 min of “KPS” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 80°C within 60 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Preparation of Base Polymer BP C5 of Comparative Example C5 A 2,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was placed into an ice bath filled with about 1 liter of water, 100 g of sodium chloride and about 200 g of ice such that the mixture covers about half the height of the resin kettle. The resin kettle was charged with about 80.0 g of solution comprising aqueous polyacrylic acid (PAA) of about 35%w concentration wherein the weight average molecular weight Mw determined by Gel Permeation Chromatography reported by size exclusion chromatography was 223 kDa (test method as described herein above). About 496.6 g water was added as ice prepared from DI water and DI water of weight about 497.5 g was also added to the mixture. A magnetic stirrer, capable of mixing the whole content, was added and stirring was started. As the PAA was fully dispersed, the full amount of 432.5 g of glacial AA (= acrylic acid) was added to the PAA solution in the resin kettle while stirring was continued. About 13.6 g of deionized water was taken to dissolve 0.4874 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “KPS” solution was closed with a plastic snap-on cap and set aside. About 10.0 g of deionized water was taken to dissolve 0.0529 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. About 115 g of deionized water was taken to dissolve 3.15 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a 250 mL glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The remaining 3.60 g of water up to a final weight of 1136.3 g was added to the resin kettle and stirring was continued as a homogeneous solution was obtained within 1-5 minutes. A thermometer was introduced and in total 347.6 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of PAA, AA and NaOH solution at a temperature below 30°C while stirring was continued. Then, the resin kettle was closed, the ice bath underneath removed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about min 10 min to 1 hour of Argon purging and stirring, about 0.03 g (about 1- 2 droplets) of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 3 min of “ASC” solution, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 70°C within 60 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was below about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Preparation of Base Polymer BP C6 of Comparative Example C6 A 10,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was charged with about 2536.1 g of ice (ca. 60% of the total amount of ice: 3050.3 g ice prepared from deionized water). A magnetic stirrer, capable of mixing the whole content (when liquid), was added and stirring was started. About 100.0 g of deionized water was taken to dissolve 2.599 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass beaker of 250 mL volume. The vessel with the “KPS” solution was closed and set aside. About 10.0 g of deionized water was taken to dissolve 0.566 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. 200.0 g of deionized water was taken to dissolve 16.76 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The full amount of 2300.1 g of glacial AA (= acrylic acid) was added to the ice in the resin kettle while stirring was continued. An amount of 908.7 g of Sokalan ® PA 110 S (BASF) comprising aqueous polyacrylic acid solution of about 35%w concentration wherein the weight average molecular weight Mw determined by Gel Permeation Chromatography reported by size exclusion chromatography was 223 kDa (test method as described herein above), was added to the mixture in the resin kettle while stirring was continued. A thermometer was introduced and in total 1975.4 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) and the remaining amount of ice (prepared from de-ionized water) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of AA, NaOH solution and ice at a temperature below 30°C while stirring was continued. The beaker that contained the “PEG700-DA” solution was washed 2x with deionized water in an amount of about 10% of the “PEG700-DA” solution volume per wash. The wash water of both washing steps was added to the stirred mixture. Deionized water (the remaining amount required to achieve the total amount of (ice + water) of 4795.0 g was added to the stirred mixture. Then, the resin kettle was closed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about 1 hour of Argon purging and stirring, the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter, about 1.90 g of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then also added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 2 min of “KPS” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 80°C within 60 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Procedure to obtain the PAA used in Example A1 to A9 (i.e. from PAA A1 to PAA A9) from degradation of pre-existing SAP material: Persulfate mediated degradation of pre-existing SAP material The pre-existing SAP material used in all examples was polyacrylic acid-based pre- existing SAP material (in the form of pre-existing SAP particles) having a capacity (CRC) of 27.6 g/g, a moisture content of 0.4%, and D50 average particle size was 398 μm as measured according to ISO method 13322-2 (the Particle Size Distribution PSD was 63-710 um). The Absorption Against Pressure (AAP) of the SAP was 25.5 g/g, as determined by the EDANA method WSP 442.2-02. In deviation from EDANA WSP 442.2-02, a pressure of 0.7 psi is applied (whereas the EDANA method specifies a pressure of only 0.3 psi). The deionized water used below is MilliporeQ. Electrical conductivity was measured with lab conductometer COND 70 INSTRUMENT without CELL, #50010522, equipped with Cell VPT51-01 C=0.1 from XS Instruments or via LF 320 / Set, #300243 equipped with TetraCon ® 325 from WTW, conductivity is < 160 μS/cm at 0°C. Similar equipment for measuring electrical conductivity can be used accordingly. The deionized water used in the examples represents the aqueous carrier. The actual amount of deionized water (= aqueous carrier) in the sample is indicated in Table 1 in column “m_w_total”. Unless stated otherwise, the experimental procedure was performed in a climate conditioned room at standard conditions of 23°C ± 2°C temperature and 45% ± 10% relative humidity. Procedure: Preparation of potassium persulfate solution “KPS Solution”: The needed amount ( see the table with experimental settings) of potassium persulfate (KPS) was weighed on a balance as dry salt of weight m1 g (Sigma-Aldrich, >=99.0% purity, inventory number 216224-500G). It was then added into the respective grams of deionized water (i.e. the aqueous carrier in a 1 L plastic bottle (made of HDPE, Nalgene TM ) as given in Table 2 below and designated as “m2”. Complete dissolution of the KPS salt is observed when no visible salt crystals remain in the solution. Wherever Hydrogen peroxide was used (HPO), a resp. amount of “KPS Solution” and respective grams of 30 weight %HPO (a.k.a. Perhydrol, Sigma-Aldrich, inventory number 216763-500ML) as given in Table 2 below and designated as “mh” was added. The so obtained amount of of “Swelling Solution”, as given in Table 2 and designated as “ms1”, was placed in appropriately sized (2 to 5 L) plastic bottle (made of HDPE, Nalgene TM ). Amount of dry pre-existing SAP material (as given in Table 2 below and designated as “mSAP” was measured on a balance into a glass beaker of 500 mL volume and put into an appropriately sized glass reactor or glass beaker (2-5 L) (e.g. resp. made by Normag GmbH or Pyrex). The resp. amount of “Swelling Solution” was added into the reactor with pre-existing SAP material quickly w/o shaking, so that the dry pre-existing SAP material swells with the fluid uniformly to a resp. swelling degree defined via x-load in grams of swelling fluid per gram of dry pre-existing SAP material (x-load shown as xL in Table 2 below). Reactor was closed with the lid (standard lid with 4 openings all closed with rubber plugs). One syringe needle was put into one of the rubber plugs to ensure pressure equilibration during heating. When a glass beaker was used instead of a reactor, the beaker was covered with aluminum foil. A circulation oven (Model Binder FED720 from Binder GmbH) was preheated to the temperature given as “T1” in the Table 2 below. As temperature T1 was reached, the closed reactor or beaker was placed into the oven for the time period specified as “t1” in Table 2 below. The reactor with the sample was taken from the oven to cool down. The sample was filtered through a metal sieve with the mesh of 500μm (diameter 240mm from “Retch”) placed on the top of plastic beaker of 2-5L volume depending on the size of the example. Filtration took about 2 hours to allow for the liquid to pass into the collecting vessel. The sample can be mixed with the spoon to improve filtration rate. The yield after filtration is given as “Y1” in Table 2 below. (see table with experimental data). The extracted polymer was a clear solution. The pre-existing SAP material was a cross-linked network of polyacrylic acid, hence the clear solution comprises substantially soluble polyacrylic acid. The sample was transferred into one or more 2 L plastic bottles for further use. An aliquot part of the clear solution with mass ms_wet is measured via 5 ml plastic syringe into a pre-weighed 20 ml glass vial (without snap-on cap). The 20 ml vial with the clear solution is then put into a vacuum oven (Heraeus Vacutherm type, Thermo Scientific TM ) at 40°C and pressure between 5 and 50 mbar for 3 hours to ensure substantial evaporation of the water. The dry polymeric residue is weighed and its mass ms_dry is used to calculate the solid content S via the formula: S = ms_dry*100/ms_wet in %w
Preparation of PAA A1-containing Base Polymer BP A1 of Example A1 A 2,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was placed into an ice bath filled with about 1 liter of water, 100 g of sodium chloride and about 200 g of ice such that the mixture covers about half the height of the resin kettle. The resin kettle was charged with about 287.0 g of solution comprising aqueous polyacrylic acid PAA A1 obtained as described above of about 9.74%w concentration wherein the weight average molecular weight Mw determined by Gel Permeation Chromatography was 134 kDa (test method as described herein above). A magnetic stirrer, capable of mixing the whole content, was added to the resin kettle and stirring was started. The full amount of 432.1 g of glacial AA (= acrylic acid) was added to the PAA solution in the resin kettle while stirring was continued. About 10.0 g of deionized water was taken to dissolve 0.012 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. About 30 g of deionized water was taken to dissolve 3.15 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a 50 mL glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The remaining amount of water up to a final weight of 885.3 g was added to the resin kettle and stirring was continued as a homogeneous solution was obtained within 5 minutes. A thermometer was introduced and in total 347.3 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of PAA, AA and NaOH solution at a temperature below 30°C while stirring was continued. Then, the resin kettle was closed, the ice bath underneath removed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about minimum 10 min or up to 1 hour of Argon purging and stirring, the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solution “ASC” was mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 1 min of “ASC” solution addition, the solution characteristically started to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 70°C within 20 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Preparation of PAA A2-containing Base Polymer BP A2 of Example A2 A 2,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was placed into an ice bath filled with about 1 liter of water, 100 g of sodium chloride and about 200 g of ice such that the mixture covers about half the height of the resin kettle. The resin kettle was charged with about 274.7 g of solution comprising aqueous polyacrylic acid PAA A2 obtained as described above of about 10.0%w concentration wherein the weight average molecular weight Mw determined by Gel Permeation Chromatography was 277 Da (test method as described herein above). A magnetic stirrer, capable of mixing the whole content, was added to the resin kettle and stirring was started. The full amount of 432.0 g of glacial AA (= acrylic acid) was added to the PAA solution in the resin kettle while stirring was continued. About 20.0 g of deionized water was taken to dissolve 0.486 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “KPS” solution was closed with a plastic snap-on cap and set aside. About 10.0 g of deionized water was taken to dissolve 0.012 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. About 30 g of deionized water was taken to dissolve 3.15 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a 50 mL glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The remaining amount of water up to a final weight of 975.2 g was added to the resin kettle and stirring was continued as a homogeneous solution was obtained within 5 minutes. A thermometer was introduced and in total 313.6 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of PAA, AA and NaOH solution at a temperature below 30°C while stirring was continued. Then, the resin kettle was closed, the ice bath underneath removed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about minimum 10 min or up to 1 hour of Argon purging and stirring, about 0.025 g (about 1-2 droplets) of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 6 min of “ASC” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 80°C within 60 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Preparation of PAA A3-containing Base Polymer BP A3 of Example A3 A 2,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was placed into an ice bath filled with about 1 liter of water, 100 g of sodium chloride and about 200 g of ice such that the mixture covers about half the height of the resin kettle. The resin kettle was charged with about 811.0 g of solution comprising aqueous polyacrylic acid PAA A3 obtained as described above of about 6.67%w concentration wherein the weight average molecular weight Mw determined by Gel Permeation Chromatography was 517,500 Da (test method as described herein above). The 6.67%w aqueous solution of PAA A3 was prepared as a stock solution by diluting and stirring overnight of PAA A3 solution of 13.66%w concentration with the appropriate amount of DI water. A magnetic stirrer, capable of mixing the whole content (when liquid), was added to the resin kettle and stirring was started. The full amount of 405.9 g of glacial AA (= acrylic acid) was added to the PAA solution in the resin kettle while stirring was continued. About 20.0 g of deionized water was taken to dissolve 0.455 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “KPS” solution was closed with a plastic snap-on cap and set aside. About 10.0 g of deionized water was taken to dissolve 0.011 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. About 30 g of deionized water was taken to dissolve 2.95 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a 50 mL glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The remaining amount of water up to a final weight of 497.7 g was added to the resin kettle and stirring was continued as a homogeneous solution was obtained within 1-5 minutes. A thermometer was introduced and in total 281.8 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of PAA, AA and NaOH solution at a temperature below 30°C while stirring was continued. Then, the resin kettle was closed, the ice bath underneath removed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about minimum 10 min or up to 1 hour of Argon purging and stirring, about 0.025 g (about 1-2 droplets) of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 4 min of “ASC” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 70°C within 60 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Preparation of PAA A456 -containing Base Polymer BP A4 of Example A4 A 2,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was placed into an ice bath filled with about 1 liter of water, 100 g of sodium chloride and about 200 g of ice such that the mixture covers about half the height of the resin kettle. The resin kettle was charged with about 466.3 g of solution comprising aqueous polyacrylic acid PAA A456 obtained as described above of about 10.78%w concentration wherein the weight average molecular weight Mw determined by Gel Permeation Chromatography was 285 Da (test method as described herein above). A magnetic stirrer, capable of mixing the whole content, was added to the resin kettle and stirring was started. The full amount of 380.2 g of glacial AA (= acrylic acid) was added to the PAA solution in the resin kettle while stirring was continued. About 20.0 g of deionized water was taken to dissolve 0.431 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “KPS” solution was closed with a plastic snap-on cap and set aside. About 10.0 g of deionized water was taken to dissolve 0.047 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. About 30 g of deionized water was taken to dissolve 2.77 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a 50 mL glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The remaining amount of water up to a final weight of 899.6 g was added to the resin kettle and stirring was continued as a homogeneous solution was obtained within 5 minutes. A thermometer was introduced and in total 250.8 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of PAA, AA and NaOH solution at a temperature below 30°C while stirring was continued. Then, the resin kettle was closed, the ice bath underneath removed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about minimum 10 min of Argon purging and stirring, about 0.025 g (about 1-2 droplets) of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 13 min of “ASC” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 60°C within 90 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Preparation of PAA A456 -containing Base Polymer BP A5 of Example A5 A 2,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was placed into an ice bath filled with about 1 liter of water, 100 g of sodium chloride and about 200 g of ice such that the mixture covers about half the height of the resin kettle. The resin kettle was charged with about 1413.9 g of solution comprising aqueous polyacrylic acid PAA A456 obtained as described above of about 10.78%w concentration wherein the weight average molecular weight Mw determined by Gel Permeation Chromatography was 285 Da (test method as described herein above). A magnetic stirrer, capable of mixing the whole content, was added to the resin kettle and stirring was started. The full amount of 380.0 g of glacial AA (= acrylic acid) was added to the PAA solution in the resin kettle while stirring was continued. About 20.0 g of deionized water was taken to dissolve 0.348 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “KPS” solution was closed with a plastic snap-on cap and set aside. About 10.0 g of deionized water was taken to dissolve 0.085 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. About 30 g of deionized water was taken to dissolve 1.20 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a 50 mL glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The remaining amount of water up to a final weight of 137.2 g was added to the resin kettle and stirring was continued as a homogeneous solution was obtained within 5 minutes. A thermometer was introduced and in total 167.6 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of PAA, AA and NaOH solution at a temperature below 30°C while stirring was continued. Then, the resin kettle was closed, the ice bath underneath removed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about minimum 10 min of Argon purging and stirring, about 0.02 g (about 1-2 droplets) of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 4 min of “ASC” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 35°C within 90 minutes. Once the temperature started to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Preparation of PAA A456 -containing Base Polymer BP A6 of Example A6 A 2,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was placed into an ice bath filled with about 1 liter of water, 100 g of sodium chloride and about 200 g of ice such that the mixture covers about half the height of the resin kettle. The resin kettle was charged with about 740.5 g of solution comprising aqueous polyacrylic acid PAA A456 obtained as described above of about 10.78%w concentration wherein the weight average molecular weight Mw determined by Gel Permeation Chromatography was 285 Da (test method as described herein above). A magnetic stirrer, capable of mixing the whole content, was added to the resin kettle and stirring was started. The full amount of 380.1 g of glacial AA (= acrylic acid) was added to the PAA solution in the resin kettle while stirring was continued. About 20.0 g of deionized water was taken to dissolve 0.427 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “KPS” solution was closed with a plastic snap-on cap and set aside. About 10.0 g of deionized water was taken to dissolve 0.045 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. About 30 g of deionized water was taken to dissolve 2.78 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a 50 mL glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The remaining amount of water up to a final weight of 625.4 g was added to the resin kettle and stirring was continued as a homogeneous solution was obtained within 5 minutes. A thermometer was introduced and in total 250.8 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of PAA, AA and NaOH solution at a temperature below 30°C while stirring was continued. Then, the resin kettle was closed, the ice bath underneath removed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about minimum 10 min of Argon purging and stirring, about 0.025 g (about 1-2 droplets) of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 9 min of “ASC” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 65°C within 90 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Preparation of PAA A7 -containing Base Polymer BP A7 of Example A7 A 2,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was placed into an ice bath filled with about 1 liter of water, 100 g of sodium chloride and about 200 g of ice such that the mixture covers about half the height of the resin kettle. The resin kettle was charged with about 1192.7 g of solution comprising aqueous polyacrylic acid PAA A7 obtained as described above of about 11.36%w concentration wherein the weight average molecular weight Mw determined by Gel Permeation Chromatography was 285 Da (test method as described herein above). A magnetic stirrer, capable of mixing the whole content, was added to the resin kettle and stirring was started. The full amount of 460.1 g of glacial AA (= acrylic acid) was added to the PAA solution in the resin kettle while stirring was continued. About 20.0 g of deionized water was taken to dissolve 0.517 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “KPS” solution was closed with a plastic snap-on cap and set aside. About 5.0 g of deionized water was taken to dissolve 0.011 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. About 20 g of deionized water was taken to dissolve 1.78 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a 50 mL glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The remaining amount of water up to a final weight of 55.4 g was added to the resin kettle and stirring was continued as a homogeneous solution was obtained within 5 minutes. A thermometer was introduced and in total 289.6 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of PAA, AA and NaOH solution at a temperature below 30°C while stirring was continued. Then, the resin kettle was closed, the ice bath underneath removed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about minimum 10 min of Argon purging and stirring, about 0.020 g (about 1-2 droplets) of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 3 min of “ASC” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 70°C within 60 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Preparation of PAA A8 -containing Base Polymer BP A8 of Example A8 A 2,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was placed into an ice bath filled with about 1 liter of water, 100 g of sodium chloride and about 200 g of ice such that the mixture covers about half the height of the resin kettle. The resin kettle was charged with about 1085.4 g of solution comprising aqueous polyacrylic acid PAA A8 obtained as described above of about 14.34%w concentration wherein the weight average molecular weight Mw determined by Gel Permeation Chromatography was 239 Da (test method as described herein above). A magnetic stirrer, capable of mixing the whole content, was added to the resin kettle and stirring was started. The full amount of 530.0 g of glacial AA (= acrylic acid) was added to the PAA solution in the resin kettle while stirring was continued. About 20.0 g of deionized water was taken to dissolve 0.596 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “KPS” solution was closed with a plastic snap-on cap and set aside. About 5.0 g of deionized water was taken to dissolve 0.013 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. No additional crosslinker “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) was added. The remaining amount of water up to a final weight of 49.92 g was added to the resin kettle and stirring was continued as a homogeneous solution was obtained within 5 minutes. A thermometer was introduced and in total 334.1 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were added subsequently in portions such that the temperature was below 30°C. Then, the resin kettle was closed, the ice bath underneath removed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about minimum 10 min of Argon purging and stirring, about 0.030 g (about 2 droplets) of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 4 min of “ASC” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 100°C within 20 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Preparation of PAA A9 -containing Base Polymer BP A9 of Example A9 A 2,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was charged with about 896.7 g of solution comprising aqueous polyacrylic acid PAA A9 obtained as described above of about 17.10%w concentration wherein the weight average molecular weight Mw determined by Gel Permeation Chromatography was 229 Da (test method as described herein above). A magnetic stirrer, capable of mixing the whole content, was added to the resin kettle and stirring was started. The full amount of 76.6 g of glacial AA (= acrylic acid) was added to the PAA solution in the resin kettle while stirring was continued. About 10.0 g of deionized water was taken to dissolve 0.086 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “KPS” solution was closed with a plastic snap-on cap and set aside. About 5.0 g of deionized water was taken to dissolve 0.020 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. No additional crosslinker “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) was added. The remaining amount of water up to a final weight of 26.83 g was added to the resin kettle and stirring was continued as a homogeneous solution was obtained within 5 minutes. A thermometer was introduced. No further NaOH (sodium hydroxide) solution was added subsequently. Then, the resin kettle was closed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about minimum 10 min of Argon purging and stirring, the “ASC” solution was added to the “KPS” solution, and in turn the resulting mixture was then added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. The reaction mixture was at a temperature of about 20°C. After the initiator solution “KPS” (and therein the “ASC” solution), was mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 2 min of “ASC” solution addition, the solution characteristically became turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; it rose slightly from about 20°C to about 31°C within 20 minutes. Once the temperature started to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Procedure to obtain the PAA used in Example A10 (=PAA A10) from degradation of pre-existing SAP material: Ultraviolet light mediated degradation of pre-existing SAP material The pre-existing SAP material (in the form of pre-existing SAP particles) used for degradation is commercially available in Pampers Baby Dry as marketed in Germany in 2020. The pre-existing SAP material was mixed with RO (reverse osmosis) water in a Quadro mixer to produce a feed stream (in the form of a gel) with 2.5 %wt SAP and 97.5 % RO water. Starting viscosity of the gel was around 840 Pa.s. About 140 mL of the feed stream was loaded in a syringe and fed into a Fusion UV Curing system (FUSION UV SYSTEMS, Inc., Maryland, USA; Hg lamp (H-Bulb) with 300 W/in. and 2.74 W/cm 2 power measured by the UV PowerMAP ® #20082105 A/B/C/V (EIT, Inc.; Sterling, VA)) in a 6 mm external diameter (OD) (3.68 mm internal diameter (ID)) quartz tube and at a rate of 6 mL/min using a syringe pump (New Era Pump Systems, Inc., Farmingdale, NY; model NE-1000 single syringe pump). The UV lamp was set perpendicular to the quartz tube, the length of the quartz tube exposed to the UV irradiation was estimated to be 15 cm, the longitudinal axis of the quartz tube was about 8 mm above the focal point of the UV lamp, and the residence time of the feed stream in the irradiation zone was 16 s and UV irradiation energy calculated as 1.4 MJ/kg SAP. The viscosity of the product stream was measured with a cup and bob fixture in steady mode, and at 4 s-1 it was measured as 155 mPa.s Preparation of PAA A10-containing Base Polymer BP A10 of Example A10 A 2,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was placed into an ice bath filled with about 1 liter of water, 100 g of sodium chloride and about 200 g of ice such that the mixture covers about half the height of the resin kettle. The resin kettle was charged with about 1043.1 g of solution comprising aqueous PAA-A10 obtained as described above, of about 2.68%w concentration wherein the weight average molecular weight Mw determined by Gel Permeation Chromatography was 1,080 kDa (test method as described herein above). A magnetic stirrer, capable of mixing the whole content (when liquid), was added to the resin kettle and stirring was started. The full amount of 432.1 g of glacial AA (= acrylic acid) was added to the PAA solution in the resin kettle while stirring was continued. About 20.0 g of deionized water was taken to dissolve 0.483 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “KPS” solution was closed with a plastic snap-on cap and set aside. About 10.0 g of deionized water was taken to dissolve 0.011 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. About 30 g of deionized water was taken to dissolve 3.22 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a 50 mL glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The remaining amount of water up to a final weight of 174.0 g was added to the resin kettle and stirring was continued as a homogeneous solution was obtained within 1-5 minutes. A thermometer was introduced and in total 347.2 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of PAA, AA and NaOH solution at a temperature below 30°C while stirring was continued. Then, the resin kettle was closed, the ice bath underneath removed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about 1 hour of Argon purging and stirring, about 0.020 g (about 1-2 droplets) of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 4 min of “ASC” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 80°C within 60 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Procedure to obtain the PAA used in Example A11 (=PAA A11) from degradation of pre-existing SAP material: Liquid Whistle (LW) mediated mechanical energy degradation) The pre-existing SAP material (in the form of pre-existing SAP particles) used for degradation is commercially available in Pampers Baby Dry as marketed in Germany in 2020. The pre-existing SAP material was mixed with RO (=reverse osmosis) water in an agitation tank system similar to EnSight Solutions Likwifier LORSS series, equipped with approximately 20 gallon working capacity tank, top mounted scrap surface agitator, bottom 6 hole/3 wing rotor-stator high shear impeller to produce a feed stream (in the form of a gel) with 2.5 wt% SAP and 97.5 wt% RO water. The gel had a viscosity of 841 Pa.s. The feed stream was fed into the Liquid Whistle apparatus (LW; Model-A Sonolator; Sonic Corp., Stratford, CT); ellipsoidal orifice dimensions: width was 2 x 0.0375 in. = 1.9 mm, height was 2 x 0.012 in. = 0.6 mm (hydraulic diameter was calculated as 1.7 mm), land length was 1 mm, and volume V = π x (width) x (height) x (land length) / 4 = 0.9 mm 3 ) (the ellipsoidal orifice had a cross-sectional surface area of about 1.3 mm 2 ) with flowrate of about 8 L/min and pressure of about 4,500 psi (310 bar), and the product stream was recirculated back into the agitation tank system. The tank volume was passed through the LW apparatus about 8 times, representing a total residence time of about 40 ms in the LW chamber region (about 5 ms per pass). The energy density achieved from the mixing device was about 62 MJ/m 3 (about 2.48 MJ/kg SAP). The actual final solid content of the product was determined to be 2.73%wt via placing 3.00 g thereof in a pre-weighed glass vial of 40 mL volume and placing said vial without cap inside a vacuum oven Preparation of PAA A11-containing Base Polymer BP A11 of Example A11 A 2,000 ml resin kettle (equipped with a four-necked glass cover closed with septa, suited for the introduction of a thermometer, syringe needles) was placed into an ice bath filled with about 1 liter of water, 100 g of sodium chloride and about 200 g of ice such that the mixture covers about half the height of the resin kettle. The resin kettle was charged with about 1024.0 g of solution comprising aqueous PAA A11 obtained as described above, of about 2.73%w concentration wherein the weight average molecular weight Mw determined by Gel Permeation Chromatography was 418 kDa (test method as described herein above). A magnetic stirrer, capable of mixing the whole content (when liquid), was added to the resin kettle and stirring was started. The full amount of 432.1 g of glacial AA (= acrylic acid) was added to the PAA solution in the resin kettle while stirring was continued. About 20.0 g of deionized water was taken to dissolve 0.484 g of “KPS” (= potassium peroxydisulfate, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “KPS” solution was closed with a plastic snap-on cap and set aside. About 10.0 g of deionized water was taken to dissolve 0.012 g of “ASC” (= Ascorbic Acid, from Sigma Aldrich) e.g. in a glass vial of 40 mL volume. The vessel with the “ASC” solution was closed with a plastic snap-on cap and set aside. About 30 g of deionized water was taken to dissolve 3.14 g of “PEG700-DA” (= polyethylene glycol diacrylate of Mn ~ 700 Da from Sigma Aldrich) e.g. in a 50 mL glass beaker. The beaker with the “PEG700-DA” solution was covered e.g. with parafilm and set aside. The remaining amount of water up to a final weight of 193.0 g was added to the resin kettle and stirring was continued as a homogeneous solution was obtained within 1-5 minutes. A thermometer was introduced and in total 347.4 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were added subsequently in portions such that the temperature was below 30°C. The “PEG700-DA” solution was added to the mixture of PAA, AA and NaOH solution at a temperature below 30°C while stirring was continued. Then, the resin kettle was closed, the ice bath underneath removed, and a pressure relief was provided e.g. by puncturing two syringe needles through the septa. The solution was then purged vigorously with argon via an 80 cm injection needle at about 0.4 bar while stirring at about 400 rpm. The argon stream was placed close to the stirrer for efficient and fast removal of dissolved oxygen. After about 1 hour of Argon purging and stirring, about 0.025 g (about 1-2 droplets) of 1%w aqueous solution of hydrogen peroxide H 2 O 2 (Sigma-Aldrich) was added via 1 mL plastic pipette to the “KPS” solution, and the latter was then added to the reaction mixture via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. Thereafter the “ASC” solution was added to the reaction mixture at a temperature of about 20°C via plastic funnel inserted temporarily in one of the resin kettle cover necks while stirring and Argon purging was continued. After the initiator solutions “KPS” and “ASC” were mixed with the reaction mixture, stirring and Argon purging was continued but the Argon needle was pulled a few cm above the liquid. Typically, within 3 min of “ASC” solution addition, the solution characteristically starts to become turbid or a sudden increase in viscosity was observed, typically at temperatures about room temperature. A “gel point” was observed and recorded when the stirbar was not able to rotate freely at the bottom of the resin kettle and the stirring was therefore stopped. Purging with argon was continued at a reduced flow rate (0.2 bar). The temperature was monitored; typically, it rises from about 20°C to about 80°C within 60 minutes. Once the temperature starts to drop from a maximal value, the resin kettle was transferred into a circulation oven (e.g. Binder FED 720 from Binder GmbH) and kept at about 60°C for about 18 hours. After this time, the oven was switched off and the resin kettle was allowed to cool down for about 2 hours while remaining in the oven. After that, the gel was removed and broken manually or cut with scissors into smaller pieces. The gel was grinded with a grinder (X70G from Scharfen Slicing Machines GmbH with Unger R70 plate system: 3 pre-cutter kidney plates with straight holes at 17mm diameter), put onto perforated stainless steel dishes (hole diameter 4.8 mm, 50 cm x 50 cm, 0.55 mm caliper, 50% open area, from RS; max. height of gel before drying: about 3 cm) and transferred into a circulation oven (Binder FED 720 from Binder GmbH) at about 120°C for about 20 hours. The residual moisture content of the dried gel was about 3% by weight (see UPM test method for description of how to determine moisture content). The dried gel was then ground using a centrifuge mill (Retsch ZM 200 from Retsch GmbH with vibratory feeder DR 100 (setting 50-60), interchangeable sieve with 1.5 mm opening settings, rotary speed 8000 rpm). The milled polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieves DIN/ISO 3310-1 at about 250 rpm for about for 5-10 min) to the following particle size cuts with the following yields: The fractions “fines” and “crude” have been discarded and not used further. Surface crosslinking treatment (hereinafter referred to as “SXL”) of base polymer particles BP A1 to BP A11 and BP C1/7 to BP C6 in order to obtain examples A1 to A11 and comparative examples C1 to C7 Equipment list: o Glassware, one way pipette, spatula, spoon to prepare solution and weigh in absorbent materials o Glass Beaker: 250 ml opening ø 70mm o Balance: Sartorius or equivalent; accuracy 0.01g o Analytical balance: Mettler or equivalent; accuracy 0.0001g o Electrical stand stirrer: IKA Eurostar power control visc (Range 50-2000 rpm) or equivalent o With Stirrer: PTFE Propeller stirrer 4- bladed _ ø 50mm o Pipette: Eppendorf Multi stream or equivalent o Aluminum foil for covering o Circulation oven: Binder FD 240 or equivalent o Equipment to determine Moisture: Halogen Moisture Balance Mettler or equivalent o Sieve machine: Retch AS 200 control “g” or equivalent o With Sieves: stainless steel: DIN/ISO 3310-1 ø10mm Preparation of solutions: x Aluminum lactate solution Prepare 1 kg 15wt% Aluminum lactate stock solution in deionized water (MilliporeQ of conductivity <1.6 μS/cm) by adding 850 g of deionized water to 150 g of Aluminum lactate. x Surface crosslinking solutions (SXL solutions) (see table 2): The used Denacol concentrations were prepared according to Table 2, each in snap cap jars of volume about 50 ml. To prepare the solutions, the Denacol bottle or container (ca. 1 L) was taken out of the fridge and let to stay out to thermally equilibrate for ca. 30 min before preparing the solutions. Solutions were prepared as follows: Different respective concentrations, for the given examples, of Denacol EX-810, DN-810 ex Nagase Co. Ltd.) were prepared by adding the amount shown in Table 2 to the snap cap plastic jar which was then filled to 20 g with 1,2- Propanediol (Merck KGaA). Table 2: Execution of SXL procedure: Each of the respective dry base polymer particles BP A1 to BP A11 and BP C1 to BP C7 was weighed to be 20-30 g and recorded to ± 0.1 g and placed in a separate 250 ml glass beaker so that the filling height is ≤ 25% of the overall height. Exact amounts are given in Table 4. The base polymer particles were mixed at 600+/-50rpm with a PTFE stirrer into the beaker. The stirrer was just touching the bottom of the beaker. The base polymer particles needed to be stirred until good fluidization of the bed is achieved. The requested amounts of solutions were added with an Eppendorf pipette, step by step like described below and the actual quantities are given in Table 4. (Speed setting of Eppendorf pipette: Middle speed) Step 1: The amount of Aluminum Lactate Solution was added into the center of stirring agitation. Afterwards, the stirring speed was raised to 2000 +/-50 rpm. Stirred for approximately 15 seconds and continued with Step 2. If necessary, covered beaker with e.g. aluminum foil to avoid jumping out of material. Step 2: The amount of SXL solution was added into the center of stirring agitation. Stirred for approximately 15 seconds and continued with Step 3. Step 3: Amount of deionized water (3 wt% based on sample weight) was added into the center of stirring agitation. Stirred for approximately 15 seconds. After stopping stirrer transferred the material into a heat resistant wide-mouth glass vial (e.g. crystallizing dish) and distributed it evenly. Took loose material only and left strong stacked material on wall in beaker. Removed loose material by slight tapping outside on wall of beaker or by use of spatula. Avoided scratching out. Covered the wide mouth glass vial with aluminum foil and stored it into a fume hood at room temperature for approximately 16h to18h (overnight is recommended) and afterwards heated the material in the oven at requested temperature and time (e.g. Surface crosslinking Denacol heat up period of 20 min from room temperature to 120°C in addition to the 3 h heating time). After 2h 20 min heating time, the aluminum foil was half-way open and stayed like this for the remaining 1 h of heating to drive moisture lower than 1%w. After heating time, removed container from the oven and placed the material into a fume hood to cool down to room temperature, for approximately 15min. The final polymers were tested for moisture, the results are shown in Table 3. Table 3: Table 4 The quantities of Denacol EX-810 and Aluminum lactate add-on were selected such that the resulting examples and comparative examples exhibited SFC above 1 unit and CRC preferably above 18 g/g. (see Table 5) Table 5: Performance of Examples A1 to A11 and Comparative Examples C1 to C7 1 ) Value for base polymer particle 2 ) Value for SAP particle after surface cross-linking As is shown by the data in Table 5, the SAP particles of Examples A1 to A11 all exhibit good properties in terms of capacity (CRC), EFFC and permeability (UPM). The amount of extractables for comparable add-on level of the s-PAA polymers is significantly lower, as can be seen e.g. by comparing the amount of extractables of examples A1, A2, A10 and A11 with comparative examples C3 and C5, all having an add-on level of s-PAA polymers of 5 weight-%. This is also reflected by the ratio of (extractables minus s-PAA polymer add-on level) to CRC of the base polymer. This ratio reflects the impact of the add-on level of the s-PAA polymers on the overall amount of extractables – and put in relation to the capacity (as an increase of capacity generally leads to an increase of amount of extractables in SAP particles). Basically, the amount of extractables of comparative examples C3 and C5 is roughly 5 weight-% higher than the amount of extractables of examples A1 and A2, indicating that the s-PAA polymers of the comparative examples have leaked out of the SAP particles to a very high extent. Compared thereto, the s-PAA polymers of the inventive examples did not significantly leak out of the SAP particles, indicating that they are covalently bound into the network due to their carbon-to-carbon double bonds.By applying s-PAA polymers having carbon-to-carbon double bonds, even s-PAA polymers of relatively low average weight molecular weight do not significantly contribute to the amount of extractables, as can especially be seen in example A1, which has an average molecular weight as low as 134 kDa. Typically, molecules with low average weight molecular weight have a higher likelihood of leaking (thus contributing to the amount of extractables) as they can escape more readily out of a swollen polymer network. However, being able to get polymerized into the polymer network of the SAP particles due to their carbon-to-carbon double bonds, even such relatively small s-PAA polymers can be readily used in the making of SAP particles. Moreover, as s-PAA polymers having carbon-to-carbon double bonds can act to crosslink polymer chains during polymerization, therefore enabling the reduction or even elimination of additional cross-linkers that are commonly applied in the making of SAP material. This is reflected by the results of examples A5 and A7 (reduced amount of -additional- crosslinker vs. 0.075 mol. ratio) and of examples A8 and A9 (no -additional- crosslinker), which all exhibit good properties. The examples having the lowest molar percent of carbon-to-carbon double bonds among the inventive examples, namely A10 and A11, have a relatively higher amount of extractables, as well as higher ratio of (extractables minus s-PAA polymer add-on level) to CRC of the base polymer compared to the other inventive examples. However, these examples still have a considerably better ratio of ratio of (extractables minus s-PAA polymer add-on level) to CRC of the base polymer than the comparative examples. The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.” Further, every numerical range given throughout this specification includes every narrower numerical range that falls within such broader numerical range. Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern. While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.