Method for preparing superabsorbent polymer material using soluble polyacrylic acid polymer having double bonds

Abstract

The present invention provides a method for preparing a superabsorbent polymer material, comprising providing a soluble polyacrylic acid polymer. The soluble polyacrylic acid polymer has a carbon-carbon double bond mole percentage of at least 0.03. The soluble polyacrylic acid polymer can be obtained from pre-existing recycled post-consumer superabsorbent polymer material and / or can be obtained from pre-existing recycled post-industrial superabsorbent polymer material. Also provided are superabsorbent polymer materials obtained by the method and absorbent articles containing the materials.

Description

Technical Field

[0001] The present invention relates to a method for preparing a superabsorbent polymer material, wherein the method uses a soluble polyacrylic acid polymer having a molar percentage of carbon-carbon double bonds of at least 0.03. The soluble polyacrylic acid polymer can be obtained from (partially) degraded recycled superabsorbent polymer particles.

[0002] Also provided is a superabsorbent polymer material obtainable by the process. Background Art

[0003] The use of superabsorbent polymer materials (hereinafter referred to as "SAP materials"), usually in the form of particles (hereinafter referred to as "SAP particles"), in particular in disposable absorbent articles is well known in the art. In view of the large number of used and discarded absorbent articles, there is a need to find methods for recycling the materials contained in the absorbent articles. SAP materials form a significant part of the materials contained in absorbent articles. Therefore, recycling SAP materials from used and discarded absorbent articles is important for the recycling of absorbent articles. SAP materials originating from used absorbent articles cannot usually be recycled as such, but need to be degraded in order to be recycled. Recently, various methods for the degradation of SAP materials have been developed, including chemical degradation, degradation via UV radiation, ultrasonic treatment, microwave radiation or mechanochemical degradation.

[0004] However, there is a need to recycle and reuse materials derived from the degradation of SAP materials. Summary of the Invention

[0005] SAP materials, such as SAP particles used in absorbent articles, are most commonly made from cross-linked polyacrylic acid polymers. Degrading cross-linked polyacrylic acid polymers into acrylic acid monomers is typically very energy-intensive and / or time-consuming. Depending on the SAP material degradation method, and also depending on how much time and / or energy is provided during the SAP material degradation method, such methods may not necessarily result in complete degradation, i.e., they do not produce acrylic acid monomers. Instead, such methods favor degradation into soluble polyacrylic acid polymers. As a result, the cross-links of the insoluble superabsorbent polymer material are disrupted, generating polyacrylic acid polymers (hereinafter also referred to as "s-PAA polymers") that are soluble in aqueous solutions.

[0006] It is known to use polyacrylic acid oligomers in the preparation of SAP materials, for example in combination with acrylic acid monomers. These oligomers generally polymerize into the cross-linked acrylic acid network of the SAP material. In contrast, it is believed that most acrylic acid polymers (i.e., molecules with a much higher molecular weight than the oligomers) do not readily polymerize or only polymerize to a small extent into the cross-linked acrylic acid network of the SAP.

[0007] For absorbent articles containing SAP particles that exhibit good absorption and containment functions, the SAP particles need to meet specific technical requirements, such as sufficient capacity and permeability of the SAP particles. Generally, high capacity and high permeability are desired. Another important parameter is the amount of extractables in the SAP material. High levels of extractables are generally undesirable for SAP particles because they negatively affect the performance of the SAP particles. Once the superabsorbent polymer material swells, the extractables tend to leach out from the cross-linked polymer network, thereby affecting the superabsorbent performance through both the loss of superabsorbent material and the competition of the extractables for penetration into the insoluble polymer matrix.

[0008] It has been found that when certain s-PAA polymers are introduced into SAP particles, the amount of extractables can undesirably increase. However, the present inventors have also discovered that s-PAA polymers containing carbon-carbon double bonds can be obtained. These double bonds are defined at the ends of each s-PAA polymer chain. The s-PAA polymers are obtained by degrading pre-existing SAP material.

[0009] Carbon-carbon double bonds were determined using an NMR alkylene content method. This method allows for the determination of the mole fraction of unsaturated alkylene moieties as a fraction of the mole fraction of tertiary proton moieties in the PAA polymer backbone in the sample. This method also allows for the inference of whether a carbon-carbon double bond is present at the end of the polymer chain or, more precisely, at some position in the chain spaced from the end of the chain.

[0010] By providing s-PAA polymers with such carbon-carbon double bonds, the s-PAA polymers are capable of reacting with other components provided in the method for preparing the SAP material of the present invention. They can react with monomers and / or oligomers and thereby become covalently bonded into the superabsorbent polymer network. Those s-PAA polymers with carbon-carbon double bonds at two or more of their chain ends (particularly, branched s-PAA polymers having more than two chain ends) can essentially function as crosslinkers within the polymer network. It has even been found that the use of s-PAA polymers with carbon-carbon double bonds facilitates the reduction of, or even the elimination of, conventional crosslinking agents in the SAP material preparation method.

[0011] When s-PAA polymers are covalently incorporated into the SAP material network, they are unable to leak out of the SAP material when the SAP material swells. Consequently, the amount of extractables can be reduced. At the same time, parameters reflecting capacity (measured as centrifuge retention capacity, CRC) and permeability (measured as urine permeability measurement, UPM) are not adversely affected compared to methods that do not employ soluble PAA polymers. This was demonstrated even for SAP materials containing relatively high amounts of soluble PAA polymer.

[0012] Different methods for degrading pre-existing SAP materials have been previously provided, such as chemical degradation (e.g., oxidative degradation), degradation using UV, and mechanical degradation. A non-limiting example of a SAP degradation method is to treat in the following manner: in an elongated flow device (e.g., U.S. Patent Application No. 62 / 890,631); using hydrothermal microwaves (e.g., U.S. Patent Application No. 62 / 890,632); using UV radiation in a flow system (e.g., U.S. Patent Application No. 16 / 548,873); using sound waves / ultrasound waves (e.g., U.S. Patent Application No. 62 / 890,880), using oxidative degradation (European Patent Application EP2019193221); using supercritical water; using a combination of elongated flow device, oxidative degradation, and enzymatic degradation (e.g., U.S. Patent Application No. 63 / 039,496); using an elongated flow device and oxidative degradation (e.g., U.S. Patent Application No. 63 / 039,498); and any combination thereof.

[0013] The present inventors have determined that whether chemical degradation results in a soluble polyacrylic acid polymer having carbon-carbon double bonds depends on the degradation method. Furthermore, the extent of carbon-carbon double bonds (i.e., the mole percentage of carbon-carbon double bonds) depends on the degradation method. Chemical degradation, particularly oxidative degradation, has been found to be particularly effective, resulting in soluble polyacrylic acid polymers obtained by such degradation having a high mole percentage of carbon-carbon double bonds.

[0014] Carbon-carbon double bonds have not been identified in commercially available soluble polyacrylic acid polymers.

[0015] The present invention relates to a method for producing a superabsorbent polymer material. The method comprises the following steps:

[0016] a) providing an aqueous solution of polymerizable acrylic monomers and / or polymerizable acrylic oligomers, optionally neutralizing at least some of the polymerizable acrylic monomers and / or the polymerizable acrylic oligomers;

[0017] b) optionally providing one or more ethylenically unsaturated comonomers, optionally neutralizing step b)

[0018] at least some of the ethylenically unsaturated comonomers of

[0019] c) optionally providing one or more cross-linking agents;

[0020] d) providing one or more initiators;

[0021] e) providing a soluble polyacrylic acid polymer, wherein the soluble polyacrylic acid polymer has a mole percentage of carbon-carbon double bonds of at least 0.02, preferably at least 0.04, more preferably at least 0.05, still more preferably at least 0.08, and even more preferably at least 0.1;

[0022] f) mixing the aqueous solutions of the monomers, oligomers, comonomers, crosslinkers and initiators provided in steps a) to e) with the soluble polyacrylic acid polymer; and

[0023] g) polymerizing the mixture obtained in step f) to obtain a superabsorbent polymer.

[0024] The ratio of the difference between the extractables [wt%] of the superabsorbent polymer material obtained by the process and the added level of s-PAA polymer [wt%] to the matrix polymer capacity (in g / g, measured as CRC according to the test method described herein) is less than 0.15, or less than 0.12, or less than 0.10.

[0025] The monomers and / or oligomers provided in process step a) may be neutralized with a degree of neutralization of 40 mol % to 95 mol %.

[0026] The optional comonomer may be provided at less than 30 wt%, or less than 20 wt%, or less than 15 wt%, or less than 10 wt%, or less than 5 wt%, or even less than 2 wt%, based on the total weight of the polymerizable acrylic monomer and / or polymerizable acrylic oligomer.

[0027] The present invention also relates to a superabsorbent polymer material comprising crosslinked polyacrylic acid and its salts, wherein the superabsorbent polymer material comprises polyacrylic acid as an internal crosslinker of the network. The polyacrylic acid internal crosslinker may be the only crosslinker of the SAP material (except for an optional surface crosslinker). Such a SAP material is obtainable by the process of the present invention.

[0028] Also provided are absorbent articles comprising the superabsorbent polymer material of the present invention.

[0029] The superabsorbent polymer material may be at least partially neutralized, preferably 50% to 95% neutralized.

[0030] The superabsorbent polymer material may have an EFFC of at least 25 g / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a top view of an exemplary absorbent article in the form of a diaper that may contain the agglomerated superabsorbent polymer particles of the present invention with some layers partially removed.

[0032] Figure 2 for Figure 1 A transverse cross-sectional view of a diaper.

[0033] Figure 3 A partial cross-sectional side view of a suitable permeability measurement system for performing a urine permeability measurement test.

[0034] Figure 4 A cross-sectional side view of a piston / cylinder assembly used to perform a urine permeability measurement test.

[0035] Figure 5 For Figure 4 Top view of the piston head of the piston / cylinder assembly shown in .

[0036] Figure 6 For the sintered plate placed on the swelling phase Figure 4 Cross-sectional side view of the piston / cylinder assembly. DETAILED DESCRIPTION

[0037] definition

[0038] "Absorbent article" refers to a device that absorbs and contains body exudates, especially urine and other aqueous liquids, and more specifically refers to a device that is placed against or adjacent to the wearer's body to absorb and contain various exudates discharged from the body. Absorbent articles may include diapers (both for infants and for adults with incontinence), pants (both for infants and for adults with incontinence), disposable absorbent inserts for diapers and pants with reusable outer covers, feminine care absorbent products such as sanitary napkins or pantiliners, breast pads, nursing pads, bibs, wipes, etc. As used herein, the term "exudates" includes, but is not limited to, urine, blood, vaginal discharge, breast milk, sweat, and feces. Preferred absorbent articles of the present invention are disposable absorbent articles, more preferably disposable diapers, disposable pants, and disposable absorbent inserts.

[0039] As used herein, "absorbent core" refers to a structure positioned between the topsheet and the backsheet of an absorbent article for absorbing and containing liquids received by the absorbent article.

[0040] As used herein, "airfelt" refers to comminuted wood pulp in the form of cellulose fibers.

[0041] As used herein, "base polymer particles" refer to SAP particles that have not undergone any surface treatment (such as surface cross-linking and / or surface coating) after having been polymerized and comminuted into superabsorbent polymer particles.

[0042] Typically, matrix polymer particles have higher capacity and lower permeability than surface treated SAP particles.

[0043] As used herein, the term "degradation" refers to the conversion of SAP into soluble PAA polymers via depolymerization, decrosslinking, molecular backbone scission, or any combination thereof.

[0044] "Disposable" is used in its ordinary sense to mean an article that is disposed of or discarded after a limited number of use events of varying lengths (e.g., less than 10 events, less than 5 events, or less than 2 events). If the disposable absorbent article is a diaper, pant, absorbent insert, sanitary napkin, catamenial pad, or wet wipe for personal hygiene, the disposable absorbent article is generally intended to be discarded after a single use.

[0045] "Diapers" and "pants" refer to absorbent articles that are generally worn by infants and incontinent patients around the lower torso so as to surround the wearer's waist and legs and are particularly suitable for receiving and containing urine and feces. In pants, as used herein, the longitudinal edges of the first waist region and the second waist region are attached to each other to pre-form a waist opening and leg openings. The pants are put on the wearer by inserting the wearer's legs into the leg openings and pulling the pants absorbent article into a position near the wearer's lower torso. Pants can be pre-formed using any suitable method, including but not limited to joining the parts of the absorbent article together using refastenable and / or non-refastenable bonding (e.g., stitching, welding, adhesives, cohesive bonding, fasteners, etc.). Pants can be pre-formed at any position along the periphery of the article (e.g., side fastening, front waist region fastening). In diapers, the waist opening and leg openings are only formed when the diaper is put on the wearer by attaching the longitudinal edges of the first waist region and the second waist region to each other (releasably) on both sides using a suitable fastening system.

[0046] "Superabsorbent polymer" ("SAP") is used herein to refer to cross-linked polymeric materials that are capable of absorbing at least 10 times their weight in an aqueous 0.9% saline solution when measured using the Centrifuge Retention Capacity (CRC) test described below. The superabsorbent polymer material of the present invention is made from polyacrylic acid polymers.

[0047] "Superabsorbent polymer particles" ("SAP" particles) are used herein to refer to superabsorbent polymer materials that are in particulate form so as to be flowable when dry.

[0048] "Pre-existing superabsorbent polymer material" ("pre-existing SAP material") is used herein to refer to SAP material that is not within the scope of the present invention, but is material that has been degraded to obtain the s-PAA polymer useful in the present invention.

[0049] "Soluble polyacrylic acid polymers" (hereinafter referred to as "s-PAA polymers") are polyacrylic acid polymers that are soluble in aqueous solution. They are not crosslinked above the gel point. The "gel point" is the abrupt change in viscosity of a solution containing the polymer. At the gel point, the solution undergoes gelation, as reflected by a loss of fluidity and the formation of a 3D network (i.e., crosslinked polymer chains), resulting in gel formation.

[0050] A "polymer backbone" is the longest series of covalently bonded atoms that together create a continuous chain of molecules. Polyacrylic acid polymers have a carbon backbone. As used herein, a polymer backbone can be unbranched (containing one straight chain) or branched (containing multiple chains).

[0051] "% wt," "%w," "weight-%," and "wt%" are used interchangeably herein and all refer to "percent by weight."

[0052] Method for preparing SAP material containing s-PAA polymer

[0053] The present invention relates to a method for producing a superabsorbent polymer material. The method comprises the following steps:

[0054] a) providing an aqueous solution of polymerizable acrylic monomers and / or polymerizable acrylic oligomers, optionally neutralizing at least some of the polymerizable acrylic monomers and / or the polymerizable acrylic oligomers;

[0055] b) optionally providing one or more ethylenically unsaturated comonomers, optionally neutralizing step b)

[0056] at least some of the ethylenically unsaturated comonomers of

[0057] c) optionally providing one or more cross-linking agents;

[0058] d) providing one or more initiators;

[0059] e) providing a soluble polyacrylic acid polymer, wherein the soluble polyacrylic acid polymer has a mole percentage of carbon-carbon double bonds of at least 0.02, preferably at least 0.04, more preferably at least 0.05, still more preferably at least 0.08, and even more preferably at least 0.1;

[0060] f) mixing the aqueous solutions of the monomers, oligomers, comonomers, crosslinkers and initiators provided in steps a) to e) with the soluble polyacrylic acid polymer; and

[0061] g) polymerizing the mixture obtained in step f) to obtain a superabsorbent polymer.

[0062] Having an s-PAA polymer in which the soluble polyacrylic acid polymer has a mole percentage of carbon-carbon double bonds of at least 0.02 ensures that the s-PAA polymer has a sufficiently high number of carbon-carbon double bonds to enable it to be readily polymerized into the polymer network of the SAP material obtained by the method. Not every single s-PAA polymer molecule may actually contain a carbon-carbon double bond; however, as long as a significant number of carbon-carbon double bonds can be determined (according to the method described below), the s-PAA polymer can be covalently bonded into the polymer network of the SAP material obtained by the method, thereby significantly reducing the amount of extractables. The higher the mole percentage of carbon-carbon double bonds, the higher the number of such double bonds in the s-PAA polymer.

[0063] When providing the s-PAA polymer in process step e), the s-PAA polymer can be provided in dry form (as a powder) into an aqueous solution, or it can be provided as an aqueous solution. Since s-PAA polymers are generally difficult to dissolve, providing the s-PAA polymer as an aqueous solution is advantageous. Furthermore, if the s-PAA polymer is obtained from the degradation of pre-existing post-consumer recycled SAP material, the degradation product (i.e., the s-PAA polymer) will most likely be an aqueous solution, and thus drying and re-dissolving the s-PAA polymer will be time-consuming and energy-intensive.

[0064] The s-PPA polymer may be provided in step e) at a weight percentage of at least 3 wt%, preferably at least 5 wt%, and more preferably at least 10 wt%, based on the total weight of the soluble polyacrylic acid polymer provided in step e) and the monomers, oligomers, comonomers, crosslinkers, and initiators provided in steps a) to d). The weight percentage of the s-PPA polymer based on the total weight of the soluble polyacrylic acid polymer provided in step e) and the monomers, oligomers, comonomers, crosslinkers, and initiators provided in steps a) to d) is also referred to below as the addition level.

[0065] The s-PPA polymer may be provided in step e) in an amount of up to 70.0 wt%, or up to 60.0 wt%, or up to 50.0 wt%, or up to 40.0 wt%, or up to 30 wt%, or up to 25.0 wt%, based on the total weight of the soluble polyacrylic acid polymer provided in step e) and the monomers, oligomers, comonomers, cross-linkers and initiators provided in steps a) to d).

[0066] Since it can be assumed that all components provided in steps a) to e) react in the polymerisation reaction, the weight % of step e) is the same as the weight % of s-PAA polymer in the superabsorbent polymer material obtained by the process.

[0067] The SAP material may be dried after polymerization. The SAP material may also be comminuted to obtain SAP particles. Comminution may be performed after drying or may be performed before drying (e.g. by so-called wet grinding).

[0068] The optional ethylenically unsaturated comonomers provided in process step b) may be water-soluble, i.e. their solubility in water at 23° C. is typically at least 1 g / 100 g water, preferably at least 5 g / 100 g water, more preferably at least 25 g / 100 g water and most preferably at least 35 g / 100 g water.

[0069] Suitable ethylenically unsaturated comonomers which are optionally provided in process step b) are, for example, ethylenically unsaturated carboxylic acids, such as methacrylic acid and itaconic acid.

[0070] Further suitable ethylenically unsaturated comonomers provided in process step b) are, for example, ethylenically unsaturated sulfonic acids, such as styrenesulfonic acid.

[0071] Further ethylenically unsaturated comonomers which can be added in combination with acrylic acid, methacrylic acid, itaconic acid or ethylenically unsaturated sulfonic acids are styrenesulfonic acid which is copolymerizable with the ethylenically unsaturated monomers provided in process step a), for example acrylamide, methacrylamide, hydroxyethyl acrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminopropyl acrylate, dimethylaminoethyl methacrylate and / or diethylaminoethyl methacrylate.

[0072] The acid groups of monomer a) and / or comonomer b) may be partially neutralized. Neutralization can be carried out at the monomer stage. This is usually accomplished by incorporating a neutralizing agent in the form of an aqueous solution or preferably a solid. The degree of neutralization is preferably 40 to 95 mol%, more preferably 40 to 80 mol%, and most preferably 50 to 75 mol%. Conventional neutralizing agents can be used, preferably alkali metal hydroxides, alkali metal oxides, alkali metal carbonates or alkali metal bicarbonates, and mixtures thereof. Ammonium salts may also be used instead of alkali metal salts. Particularly preferred alkali metals are sodium and potassium, but very particularly preferred are sodium hydroxide, sodium carbonate or sodium bicarbonate, and mixtures thereof.

[0073] Suitable crosslinking agents, optionally provided in process step b), are compounds having at least two groups suitable for crosslinking. Such groups are, for example, ethylenically unsaturated groups that can be free-radically polymerized into the polymer chain, and functional groups that can form covalent bonds with the acid groups of the monomers provided in process step a) and / or with the comonomers provided in process step b). Furthermore, polyvalent metal salts that can form coordinate bonds with at least two acid groups of the monomers provided in process step a) are also suitable crosslinking agents.

[0074] The optional crosslinker provided in process step c) is preferably a compound having at least two polymerizable groups which can be free-radically polymerized into the polymer network. Suitable crosslinkers provided in process step b) are, for example, methylenebisacrylamide, ethylene glycol dimethacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallylammonium chloride, tetraallyloxyethane or mixed acrylates which, in addition to acrylate groups, contain further ethylenically unsaturated groups.

[0075] The amount of crosslinker provided in process step c) is preferably from 0.0001 to 0.5% by weight, more preferably from 0.001 to 0.2% by weight, most preferably from 0.01 to 0.1% by weight, based on the total weight of the unneutralized monomer provided in process step a) and the unneutralized comonomer provided in process step b).

[0076] The optional cross-linking agent provided in step c) is different from the s-PAA polymer provided in step e). Thus, the optional cross-linking agent provided in step c) is not a polyacrylic acid polymer having carbon-carbon double bonds.

[0077] Since the s-PAA polymer having carbon-carbon double bonds provided in step e) is used as a crosslinking agent, providing an additional crosslinking agent is optional. If an additional crosslinking agent is provided, the amount (in wt %) can be kept relatively low.

[0078] The initiators provided in process step d) may be all compounds which generate free radicals under the polymerization conditions, for example thermal initiators, redox initiators or photoinitiators.

[0079] Suitable redox initiators are potassium or sodium peroxodisulfate / ascorbic acid, hydrogen peroxide / ascorbic acid, potassium or sodium peroxodisulfate / sodium bisulfite and hydrogen peroxide / sodium bisulfite. Preference is given to using mixtures of thermal initiators and redox initiators, such as potassium or sodium peroxodisulfate / hydrogen peroxide / ascorbic acid. However, the reducing component used is preferably a mixture of the sodium salt of 2-hydroxy-2-sulfinatoacetic acid, the disodium salt of 2-hydroxy-2-sulfinatoacetic acid and sodium bisulfite. This mixture can be used as FF6 and FF7 (Brüggemann Chemicals; Heilbronn; Germany) was obtained.

[0080] Suitable thermal initiators are especially azo initiators, for example 2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride and 2,2′-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2′-azobis(2-amidinopropane) dihydrochloride, 4,4″-azobis(4-cyanovaleric acid), 4,4′ and its sodium salt, 2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] and 2,2′-azobis(imino-1-pyrrolidinyl-2-ethylpropane) dihydrochloride.

[0081] Suitable photoinitiators are, for example, 2-hydroxy-2-methylpropiophenone and 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one.

[0082] The mixing and polymerization in process steps f) and g) can be carried out in a kneading reactor or a belt reactor. In a kneading reactor, the polymer gel formed during polymerization is continuously comminuted, for example, by counter-rotating agitator shafts. Polymerization in belt reactors is also well known in the art. Polymerization in a belt reactor forms a polymer gel, which must be comminuted in a further process step, for example, in an extruder or kneader.

[0083] The s-PAA polymer having carbon-carbon double bonds provided in step e) can be obtained from a pre-existing recycled post-consumer superabsorbent polymer material or from a pre-existing recycled post-industrial superabsorbent polymer material. Thus, the method can comprise a further step a1) of obtaining the s-PAA polymer from a pre-existing recycled post-consumer superabsorbent polymer material or from a pre-existing recycled post-industrial superabsorbent polymer material. These s-PAA polymers can be obtained by chemical degradation of a pre-existing recycled post-consumer superabsorbent polymer material. Step a1) can be performed before step b).

[0084] Chemical degradation can be accomplished using an oxidizing water-soluble salt comprising at least one cation and at least one anion. The at least one anion can be selected from the group consisting of peroxydisulfate, peroxymonosulfate, peroxydicarbonate, peroxydiphosphate, peroxydiborate, and mixtures and combinations thereof.

[0085] Instead of chemical degradation using oxidizing water-soluble salts, the chemical degradation can be mediated by a redox couple. It is well known in the art that primary free radicals can be generated via a redox couple, thereby allowing for a more controlled free radical flux at lower temperatures than thermal decomposition alone. The redox couple can be selected from: 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.

[0086] If the s-PAA polymer having carbon-carbon double bonds is derived from the degradation of a pre-existing SAP material (such as pre-existing SAP particles), the pre-existing SAP material can be a pre-existing virgin SAP material, a pre-existing post-consumer recycled SAP material, a pre-existing post-industrial recycled SAP material, or a combination of these materials. As used herein, "post-consumer recycled SAP material" refers to a pre-existing SAP material that has been contained within an absorbent article and the absorbent article has been used by a consumer (e.g., worn by an incontinent user). After use, the absorbent article is recycled, and the pre-existing post-consumer recycled SAP material is separated from the absorbent article and degraded into s-PAA polymer. As used herein, "post-industrial recycled SAP material" refers to a pre-existing SAP material that may or may not be contained within an absorbent article. Post-industrial recycled SAP has not been previously used, for example, it is not contained within an absorbent article that has been used by a consumer. Conversely, post-industrial recycled SAP material may be derived from absorbent articles that have been sorted out during production, for example, because they have defects. Post-industrial recycled SAP material that is not contained within an absorbent article may have been selected during the production of a previous SAP material, for example, because it did not meet desired performance targets (such as particle size distribution (PSD), capacity, whiteness, etc.).

[0087] The s-PAA polymer provided in step e) may have a weight average molecular weight Mw of at least 50 kDa, or at least 100 kDa, or at least 120 kDa, or at least 150 kDa, or at least 200 kDa.

[0088] The s-PAA polymer provided in step e) may have a weight average molecular weight Mw of no greater than 3 MDa, or no greater than 2 MDa, or no greater than 1.5 MDa, or no greater than 1 MDa.

[0089] The SAP material obtained by the process may have an amount of extractables of less than 15.0 wt%, or less than 13 wt%, or less than 12 wt%, based on the total weight of the superabsorbent polymer material.

[0090] The SAP material obtained by the method has a capacity of at least 20 g / g, as measured as centrifuge retention capacity (CRC) according to the test method described herein. The ratio of the difference between the amount of extractables (wt %) and the amount of s-PAA polymer added (% wt) of the SAP material obtained by the method to the capacity (g / g) may be less than 0.15, or less than 0.12, or less than 0.10.

[0091] The method may comprise the additional step of surface crosslinking the SAP particles obtained by the method (wherein the SAP particles are obtained by the additional method steps of drying the SAP material and comminuting the SAP material). The surface crosslinking may be performed by spraying a solution of the surface crosslinking agent (such as an aqueous solution) onto the dried SAP particles. After the spray application, the surface crosslinking agent-coated polymer particles are thermally surface crosslinked.

[0092] The spray application of the surface crosslinker solution onto the SAP particles is preferably carried out in mixers with moving mixing tools, such as screw mixers, disk mixers and paddle mixers.

[0093] Superabsorbent polymer materials comprising soluble polyacrylic acid polymers

[0094] The superabsorbent polymer material of the present invention comprises crosslinked polyacrylic acid and its salts, wherein the superabsorbent polymer material comprises polyacrylic acid as an internal crosslinking agent of the network. Polyacrylic acid may be the only internal crosslinking agent of the SAP material.

[0095] If polyacrylic acid is the only internal cross-linking agent, this indicates that no additional cross-linking agents should be used in the process of preparing the SAP material.

[0096] The SAP material can be in the form of superabsorbent polymer particles. The SAP particles can be surface cross-linked. In addition to or in place of being surface cross-linked, the SAP can be coated.

[0097] The SAP material of the present invention may have an amount of extractables of less than 15 wt%, or less than 13 wt%, or less than 12 wt%.If the capacity of the SAP material increases, the amount of extractables generally increases.

[0098] The SAP materials of the present invention may have a capacity of at least 20 g / g as measured according to the Centrifuge Retention Capacity (CRC) method described below.

[0099] The SAP material of the present invention may have an EFFC value of at least 25 g / g or at least 25 g / g. The EFFC value combines the capacity (CRC) and absorption under pressure (AAP) properties of the SAP material into

[0100] EFFC=(CRC+AAP) / 2.

[0101] If the SAP material is in the form of SAP particles, the SAP particles can have a variety of shapes. The term "particles" refers to granules, fibers, flakes, spheres, powders, thin plates, and other shapes and forms known to those skilled in the art of SAP particles. In some embodiments, the SAP particles can be in the shape of fibers, i.e., elongated needle-shaped superabsorbent polymer particles. In those embodiments, the SAP particle fibers have a small scale (i.e., the diameter of the fiber) of less than about 1 mm, typically less than about 500 μm, and preferably less than 250 μm down to 50 μm. The length of the fiber is preferably from about 3 mm to about 100 mm. The fiber can also be in the form of a long, braided filament.

[0102] Alternatively, the SAP particles of the present invention are spherical particles. According to the present invention and in contrast to fibers, "spherical particles" have a longest and a smallest dimension, and the ratio of the longest and smallest particle dimensions of the particles is in the range of 1-5, where a value of 1 would be equivalent to a perfectly spherical particle, while a value of 5 would account for some deviation from such a spherical particle. In this embodiment, the SAP particles may have a particle size of less than 850 μm, or from 50 μm to 850 μm, preferably from 100 μm to 500 μm, and more preferably from 150 μm to 300 μm, as measured according to EDANA method WSP 220.2-05. SAP particles with a relatively low particle size help increase the surface area in contact with liquid exudates and, therefore, support rapid absorption of liquid exudates.

[0103] The superabsorbent polymer material may be partially neutralized, for example by polymerizing acrylic acid monomers at 40 to 95 mol% neutralization, or 50 to 80 mol% neutralization, or 55 to 75 mol% neutralization. Alternatively or in addition, the superabsorbent polymer material may be neutralized after polymerization so that the total degree of neutralization is 40-95 mol%, or 50-80 mol%, or 55-75 mol%.

[0104] The term "surface" describes the outward-facing boundary of a particle. For porous SAP particles, the exposed interior surface can also be considered a surface. The term "surface-crosslinked SAP particle" refers to SAP particles whose molecular chains are crosslinked near the particle surface by a compound called a surface crosslinker. The surface crosslinker is applied to the surface of the particle. In surface-crosslinked SAP particles, the level of crosslinking near the SAP particle surface is generally higher than the level of crosslinking within the SAP interior.

[0105] Commonly used surface crosslinkers are heat-activatable. The term "heat-activatable surface crosslinker" refers to a surface crosslinker that reacts only upon exposure to elevated temperatures, typically around 150°C. Heat-activatable surface crosslinkers known in the art are, for example, difunctional or multifunctional agents capable of establishing additional crosslinks between the polymer chains of the SAP. Examples of heat-activatable surface crosslinkers include, but are not limited to, diols or polyols or derivatives thereof capable of forming diols or polyols, alkylene carbonates, ketals and diglycidyl or polyglycidyl ethers, halogenated epoxides, polyaldehydes, polyols, and polyamines. Crosslinking is based on reactions between functional groups contained in the polymer, such as esterification reactions between carboxyl groups (contained in the polymer) and hydroxyl groups (contained in the surface crosslinker). Because a relatively large fraction of the carboxyl groups of the polymer chains are typically neutralized prior to the polymerization step, only a small number of carboxyl groups are available for such surface crosslinking processes known in the art. For example, in a 70% neutralized polymer, only 3 out of 10 carboxyl groups are available for covalent surface crosslinking.

[0106] The surfaces of the SAP particles can be coated, either instead of surface crosslinking, or more preferably in addition to surface crosslinking (where coating is performed after surface crosslinking). Coating makes the surface tacky so that the SAP particles cannot easily rearrange themselves when wetted (so they cannot block interstices).

[0107] For example, the SAP particles may be coated with a cationic polymer. Preferred cationic polymers may include polyamine or polyimine materials that react with at least one component contained in body fluids, particularly urine. Preferred polyamine materials are selected from (1) polymers having primary amine groups (e.g., polyethyleneamine, polyallylamine); (2) polymers having secondary amine groups (e.g., polyethyleneimine); and (3) polymers having tertiary amine groups (e.g., poly-N,N-dimethylalkylamine). Specific examples of cationic polymers include polyethyleneimine, modified polyethyleneimine cross-linked by epihalohydrin within the water-soluble range, polyamines, modified polyamidoamines grafted by ethyleneimine, polyetheramines, polyethyleneamines, polyalkylamines, polyamidopolyamines, and polyallylamines.

[0108] The cationic polymer coated on the surface of the SAP particles may have a weight average molecular weight M of at least 500 Da, more preferably 5000 Da, and most preferably 10,000 Da or more. w The cationic polymer having a weight average molecular weight of 500 or more is not limited to polymers showing a single maximum value (peak) in molecular weight analysis by gel permeation chromatography, and even if it shows a plurality of maximum values ​​(peaks), a polymer having a weight average molecular weight of 500 or more can be used.

[0109] The amount of the cationic polymer is preferably about 0.05 to 20 parts by weight, more preferably about 0.3 to 10 parts by weight, and most preferably about 0.5 to 5 parts by weight, relative to 100 parts by weight of the superabsorbent polymer particles.

[0110] absorbent products

[0111] Typical disposable absorbent articles (in which the SAP materials of the present invention may be used) are placed against or adjacent to the wearer's body to absorb and contain the various exudates discharged from the body and are in the form of diapers 20. Figure 1 and Figure 2 Indicated in.

[0112] In more detail, Figure 1 is a plan view of an exemplary diaper 20 in a flattened position with portions of the diaper cut away to more clearly illustrate the construction of the diaper 20. The diaper 20 is shown for illustrative purposes only, as the SAP material of the present invention may be included in a wide variety of diapers or other absorbent articles.

[0113] like Figure 1 and Figure 2 As shown, absorbent article (here is diaper) can comprise liquid-permeable top sheet 24, liquid-impermeable back sheet 26, absorbent core 28 positioned between top sheet 24 and back sheet 26.Absorbent core 28 can absorb and hold the liquid received by described absorbent article, and can comprise absorbent material 60, other absorbent material commonly used in such as SAP material 66 of the present invention and / or cellulose fiber and absorbent article and non-absorbent material (for example thermoplastic adhesive fixing SAP particles).Absorbent material and non-absorbent material can be wrapped in substrate (for example one or more nonwovens, tissue), such as by facing the upper core cover layer 56 of top sheet and facing the lower core cover layer 58 of back sheet.Such upper core cover layer and lower core cover layer can be made by nonwoven, tissue etc. and can for example be attached to each other continuously or discontinuously along its periphery.

[0114] Absorbent cores may include one or more substrates (such as nonwoven webs or tissue paper), a SAP material (such as SAP particles) arranged on one or more substrates, and a thermoplastic composition generally arranged on a SAP material (such as SAP particles). Typically, the thermoplastic composition is a thermoplastic adhesive material. In one embodiment, the thermoplastic adhesive material forms a fiber layer that is at least partially in contact with the SAP material (such as SAP particles) on one or more substrates and partially in contact with one or more substrates. In order to enhance the adhesion of SAP material (such as SAP particles) and / or thermoplastic adhesive material to the corresponding substrate, an auxiliary adhesive may be deposited on one or more substrates before applying the SAP material (such as SAP particles). Absorbent cores may also include one or more cover layers so that the SAP material (such as SAP particles) is contained between one or more substrates and one or more cover layers. The one or more substrates and one or more cover layers may include or be composed of a nonwoven web. Absorbent cores may also include an odor control compound.

[0115] The absorbent core may consist essentially of one or more substrate layers, SAP material (eg, SAP particles), a thermoplastic composition, optionally an auxiliary binder, optionally a cover layer, and optionally an odor control compound.

[0116] The absorbent core may also comprise a mixture of SAP particles and airfelt, which may be embedded in one or more substrate layers such as a nonwoven web or tissue paper. Such absorbent cores may comprise 30% to 95%, or 50% to 95%, of SAP particles by weight of the absorbent material and may comprise 5% to 70%, or 5% to 50%, of airfelt by weight of the absorbent material (for these percentages, any embedded substrate layer is not considered absorbent material). The absorbent core may also be free of airfelt and may comprise 100% SAP particles by weight of the absorbent material.

[0117] The absorbent core may comprise a mixture or combination of the SAP material of the present invention and other SAP materials (such as other SAP particles and / or SAP foams). For example, the absorbent core may comprise at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or 100% SAP material by weight of the absorbent material, wherein the SAP material comprises at least 10%, or at least 20%, or at least 30%, or at least 50%, or at least 75%, or at least 90%, or 100% SAP material of the present invention based on the total weight of the SAP material in the absorbent core.

[0118] The absorbent articles of the present invention, particularly diapers and pants, may include an acquisition layer 52, a distribution layer 54, or a combination of the two (collectively referred to herein as an acquisition-distribution system "ADS" 50). The function of the ADS 50 is generally to quickly acquire the fluid and distribute it to the absorbent core in an efficient manner. The ADS may include one, two, or more layers. In the following example, the ADS 50 includes two layers: a distribution layer 54 and an acquisition layer 52 disposed between the absorbent core and the topsheet.

[0119] The ADS may not contain SAP materials. The prior art discloses various types of acquisition-dispensing systems, see for example WO2000 / 59430, WO95 / 10996, US5700254, WO02 / 067809. However, the SAP material of the present invention may also be contained in the ADS.

[0120] The function of the distribution layer 54 is to distribute the incoming fluid liquid over a larger surface area within the article, enabling a more efficient use of the absorbent capacity of the absorbent core. The distribution layer can be made of a nonwoven material based on synthetic or cellulosic fibers and having a relatively low density. The distribution layer can typically have a density of 30 g / m 2 Up to 400g / m 2 , specifically 80g / m 2 Up to 300g / m 2 The average basis weight of

[0121] The distribution layer may, for example, comprise at least 50%, or 60%, or 70%, or 80%, or 90%, or 100% cross-linked cellulose fibers by weight. The cross-linked cellulose fibers may be wrinkled, twisted, or curled, or combinations thereof (including wrinkled, twisted, and curled). The cross-linked cellulose fibers provide higher elasticity and, therefore, higher resistance to compression of the first absorbent layer under product packaging or use conditions (e.g., under the weight of an infant). This provides the core with relatively high void volume, permeability, and liquid absorption, thereby reducing leakage and improving dryness.

[0122] The absorbent article 20 may also include an acquisition layer 52, the function of which is to quickly acquire the fluid away from the top sheet in order to provide good dryness for the wearer. The acquisition layer 52 is typically placed directly below the top sheet and below the distribution layer. The acquisition layer can typically be or include a nonwoven material, such as an SMS or SMMS material, which includes a spunbond layer, a meltblown layer, and other spunbond layers or alternatively a carded chemically bonded nonwoven material. The nonwoven material can specifically be latex bonded. An exemplary upper acquisition layer 52 is disclosed in US7786341. Carded resin-bonded nonwoven materials can be used, especially when the fibers used are solid round or round and hollow PET staple fibers (e.g., a 50 / 50 or 40 / 60 mixture of 6 denier fibers and 9 denier fibers). An exemplary binder is butadiene / styrene latex.

[0123] The acquisition layer 52 may be stabilized by a latex binder, such as a styrene-butadiene latex binder (SB latex). Methods for obtaining such a lattice are known, for example, from EP 149 880 (Kwok) and US 2003 / 0105190 (Diehl et al.). The binder may be present in the acquisition layer 52 in excess of 12%, 14% or 16% by weight, but may be present in no more than 30%, or no more than 25% by weight of the acquisition layer. SB latex is available under the trade name GENFLO TM 3160 (OMNOVA Solutions Inc.; Akron, Ohio).

[0124] The diaper may also include elasticized leg cuffs 32 and barrier cuffs 34 that improve the containment of liquids and other body exudates, particularly in the leg opening areas. Typically, each leg cuff 32 and barrier cuff 34 will include one or more elastic threads 33 and 35, which are shown in enlarged form in FIG. Figure 1 and Figure 2 In addition, the diaper 20 may include other features such as rear ears 40, front ears 46, and / or attached barrier cuffs 34 to form a composite diaper structure. The diaper may also include a fastening system, such as an adhesive fastening system or a mechanical fastening system (e.g., a hook-and-loop fastening system), which may include tape tabs 42, such as adhesive tape tabs or tape tabs including hook elements that cooperate with landing zones 44 (e.g., a nonwoven web that provides the loops in the hook-and-loop fastening system). In addition, the diaper may include other elements, such as a rear elastic waist structure and a front elastic waist structure, side panels, or a lotion application.

[0125] like Figure 1 and 2As shown, the diaper 20 can be imaginary divided into a first waist region 36, a second waist region 38 opposite the first waist region 36, and a crotch region 37 located between the first waist region 36 and the second waist region 38. The longitudinal centerline 80 is an imaginary line that separates the diaper into two equal halves along its length. The transverse centerline 90 is an imaginary line that is perpendicular to the longitudinal centerline 80 in the plane of the diaper when flattened and passes through the middle of the length of the diaper. The perimeter of the diaper 20 is defined by the outer edges of the diaper 20. The longitudinal edges of the diaper can extend generally parallel to the longitudinal centerline 80 of the diaper 20, and the end edges extend generally parallel to the transverse centerline 90 of the diaper 20 between the longitudinal edges.

[0126] Bio-based materials

[0127] Using ASTM D6866-10, Method B, absorbent articles comprising the SAP material of the present invention may comprise a biobased content value of from about 10% to about 100%, or from about 25% to about 75%, or from about 50% to about 60%.

[0128] Using ASTM D6866-10, Method B, various components of an absorbent article, such as the topsheet, backsheet, fasteners, ADS, back ears, outer cover nonwoven material, elastic laminate (such as the elastic laminate forming the belt of the absorbent article), or any other component may include a biobased content value of about 10% to about 100%, or about 25% to about 75%, or about 50% to about 60%.

[0129] In order to determine the bio-based content of a single component material (i.e., nonwoven) using the method of ASTM D6866-10, the material is separated and cleaned so that the resulting sample reflects the composition starting material as closely as possible. For example, if a component needs to be deconstructed (e.g., elastic strands are removed from a laminate formed by one or more nonwovens and elastic strands), the nonwoven is washed with a suitable solvent to remove any residual adhesive present. In order to apply the method of ASTM D6866-10 to a sample assembly of two or more materials having different or unknown compositions, the sample is homogenized by grinding the material into a particle form (particle size of about 20 meshes or less) using a known grinding method (such as using a Wiley grinder). A representative sample of suitable quality is then taken out from the sample of the resulting randomly mixed particles.

[0130] Verification of polymers derived from renewable resources

[0131] A suitable verification technique is by 14C analysis. Small amounts of carbon dioxide in the atmosphere are radioactive. 14C carbon dioxide is produced when nitrogen is attacked by neutrons produced by ultraviolet light, causing it to lose a proton and form carbon with a molecular weight of 14, which is immediately oxidized to carbon dioxide. This radioactive isotope represents a small but measurable fraction of atmospheric carbon. Atmospheric carbon dioxide is recycled by green plants to produce organic molecules during photosynthesis. When green plants or other forms of life metabolize organic molecules to produce carbon dioxide, the cycle ends and the carbon dioxide is released back into the atmosphere. Almost all forms of life on Earth rely on green plants to produce organic molecules to grow and reproduce. Therefore, the 14C present in the atmosphere becomes part of all life forms and their biological products. In contrast, fossil fuel-based carbon does not have the labeled radiocarbon ratio of atmospheric carbon dioxide.

[0132] The assessment of renewable carbon in materials can be performed using standard test methods. By using radiocarbon and isotope ratio mass spectrometry, the biobased content of a material can be determined. ASTM International (formally known as the American Society for Testing and Materials) has established a standard method for assessing the biobased content of a material. The ASTM method is designated ASTM D6866-10.

[0133] The application of ASTM D6866-10 to derive "biobased content" is based on the same concepts as radiocarbon dating, but without the use of an age equation. The analysis is performed by deriving the ratio of the amount of organic radiocarbon (14C) in the unknown sample to the amount of radiocarbon in a modern reference standard. This ratio is reported as a percentage, using the unit "pMC" (percent modern carbon).

[0134] The modern reference standard used in radiocarbon dating is the NIST (National Institute of Standards and Technology) standard, which has a known radiocarbon content corresponding to approximately 1950 AD. 1950 AD was chosen because it represents a time before thermonuclear weapons testing, which introduced large amounts of excess radiocarbon into the atmosphere with each explosion (the term "carbon explosion"). The 1950 AD reference is expressed as 100 pM C.

[0135] Tests show that atmospheric radiocarbon levels peaked in 1963, nearly double normal levels, due to a "carbon explosion" before the end of thermonuclear weapons testing. The distribution of atmospheric radiocarbon levels remained roughly constant after reaching this peak, resulting in biological radiocarbon concentrations exceeding 100 pMc in both plants and animals after 1950 AD. This concentration has gradually decreased over time, reaching current values ​​closer to 107.5 pMc. This means that fresh biomass materials, such as corn, can produce radiocarbon signatures close to 107.5 pMc.

[0136] Combining fossil carbon with contemporary carbon in a material will result in a dilution of the contemporary pMC content. Assuming 107.5 pMC represents a contemporary biomass material and 0 pMC represents a petroleum derivative, the pMC value measured for that material will reflect the proportions of the two component types. A material derived 100% from contemporary soybeans should give a radiocarbon signature close to 107.5 pMC. If that material were diluted with, for example, 50% petroleum derivatives, it would give a radiocarbon signature close to 54 pMC (assuming petroleum derivatives have the same carbon percentage as soybeans).

[0137] The results for biomass content were derived by setting 100% equal to 107.5 pMC and 0% equal to 0 pMC. In this regard, a sample measuring 99 pMC would give an equivalent biobased content value of 92%.

[0138] The materials described herein can be evaluated according to ASTM D6866. The average values ​​quoted in this report cover an absolute range of 6% (±3% on either side of the biobased content value) to account for variations in the radiocarbon signature of the final components. It is assumed that all materials are modern or fossil in their original state, and that the desired result is the amount of biobased components "present" in the material, not the amount of biobased materials "used" in the manufacturing process.

[0139] Test Method

[0140] NMR olefin content method (determination of carbon-carbon double bonds in s-PAA polymers)

[0141] The NMR olefin content method is used to determine the mole percentage of the olefin terminal portion of each monomer present in a sample of SAP material. In this method, proton NMR spectroscopy is used to analyze a sample of SAP material in heavy water, and the peaks corresponding to olefin protons and backbone monomer protons, respectively, are identified, integrated, and ratioed to determine the mole percentage of the olefin terminal portion (referred to herein as a carbon-carbon double bond) of each polymer backbone monomer unit.

[0142] About 0.1mL SAP solution is diluted with about 1mL heavy water D2O and stirred for at least 5 minutes to ensure homogeneity.Then the sample is transferred to an NMR glass grade tube and placed in the sample holder of a proton NMR instrument. (The example of a suitable instrument is a Bruker NMR device with a 400MHz field strength. Instruments of other manufactures and other field strengths, even including "low field" instruments operating as low as 60MHz, can be successfully used to perform the method. The noesy-presat sequence is used to acquire data and suppress residual water signals. The technician will be familiar with the appropriate selection of other specific data collection parameters. The appropriate parameters used together with the above-mentioned exemplary 400MHz Bruker instrument are: 4.1s acquisition time (FID length), 8s relaxation time, 90 degree pulse width, 20ppm spectral width, 64k points in the FID and the 64 repetition scans used. In the Fourier transform step, an exponential apodization with a 0.3Hz line broadening is used, and the spectrum is phased to absorption. Spline baseline correction is used to ensure the flat baseline on either side of the peak to be integrated.

[0143] If present, determine and integrate the peak corresponding to one of the two terminal olefin protons at a chemical shift of about 5.35 ppm in the NMR spectrum. (In order to confirm that the proton peak at about 5.35 ppm is a terminal olefin proton, a standard edited H-C HSQC sequence (following, for example, W. Willker, D. Leibfritz, R. Kerssebaum and W. Bermel, Magn. Reson. Chem. 31, 287-292 (1993)) can be used to determine that the olefin signals seen in the 1D-1H spectrum are all connected to the same methylene (secondary) carbon (-CH ).) If there is no such peak, this is reported as having no measurable terminal olefin content. Otherwise, the CH backbone signal at about 1.8 ppm (generated by a single proton on the polyacrylic acid tertiary carbon of each monomer unit) is integrated. The ratio of the area of ​​the about 5.35 ppm olefin peak to the area of ​​the about 1.8 ppm CH backbone peak is calculated and reported as a percentage to the nearest 0.1%.

[0144] Gel Permeation Chromatography with Multi-Angle Light Scattering and Refractive Index Detection for Polymer Molecular Weight Distribution Measurements Method (GPC-MALS / RI)

[0145] Gel permeation chromatography (GPC) with multi-angle light scattering (MALS) and refractive index (RI) detection (GPC-MALS / RI) allows the determination of the absolute weight-average molecular weight, M, of polymers. w No column calibration methods or standards are required. GPC systems allow molecules to be separated as a function of their molecular size. MALS and RI allow information on number average (Mn) and weight average (Mw) molecular weights to be obtained.

[0146] M of water-soluble polymers such as s-PAA polymers w The distribution is typically measured by using a liquid chromatography system, which typically consists of a pump system, an autosampler (e.g., an Agilent 1260 Infinity pump system with OpenLab Chemstation software, Agilent Technology, Santa Clara, CA, USA), and an appropriately sized column set (e.g., a Waters Super Hydrogel guard column, 6 mm ID x 40 mm long, two Super Hydrogel linear columns, 7.8 mm ID x 300 mm long, Waters Corporation of Milford, MA, USA) typically operated at 40°C.

[0147] A column set comprises one or typically a plurality of subsequently connected columns having different pore sizes graded for polymers of different molecular weights, and the columns are generally selected to provide resolution over a broad and relevant molecular weight range.

[0148] Typically, the mobile phase is, for example, 0.1 M sodium nitrate in water containing 0.02% sodium azide and is pumped isocratically at a flow rate of about 1 mL / min. ) controlled multi-angle light scattering (MALS) detector (e.g. ) and a differential refractive index (RI) detector (e.g., Wyatt Technology of Santa Barbara, California, USA).

[0149] The samples were typically prepared by dissolving the polymer material (such as s-PAA polymer) at approximately 1 mg / ml in the mobile phase and hydrating the solution by mixing overnight at room temperature. Prior to GPC analysis, the samples were filtered through a membrane filter (e.g., 0.8 μm Versapor filter, PALL, Life Sciences, NY, USA) using a syringe into an LC autosampler vial.

[0150] The dn / dc (differential change of refractive index with concentration) values ​​are typically measured on the polymeric material of interest and used to determine the number average molecular weight and weight average molecular weight by the respective detector software.

[0151] Urine Permeability Measurement (UPM) Test Method

[0152] Laboratory conditions :

[0153] The test must be carried out in a climate-conditioned room under standard conditions of 23°C ± 2°C temperature and 45% ± 10% relative humidity.

[0154] Urine osmotic pressure measurement system

[0155] This method measures the permeability of the swollen hydrogel layer 1318. The apparatus used for this method is described below. This method is closely related to the prior art SFC (Saline Flow Conductivity) test method.

[0156] Figure 3 Shown is a permeability measurement system 1000 equipped with a constant hydrostatic head reservoir 1014, an open-ended tube 1010 for air entry, a plug 1012 for refilling, a test stand 1016, a transfer tube 1018 having a flexible tube 1045 with a Tygon tubular nozzle 1044, a stopcock 1020, a cover plate 1047 and a support ring 1040, a receiving container 1024, a balance 1026, and a piston / cylinder assembly 1028.

[0157] Figure 4 The piston / cylinder assembly 1028 is shown including a metal weight 1112, a piston shaft 1114, a piston head 1118, a cover 1116, and a cylinder 1120. The cylinder 1120 is made of a transparent polycarbonate (e.g., ) and has an inner diameter p of 6.00 cm, (area = 28.27 cm 2 ), wherein the inner cylindrical wall 1150 is smooth. The bottom 1148 of the cylinder 1120 is covered with a stainless steel mesh (ISO 9044 material 1.4401, mesh size 0.038 mm, wire diameter 0.025 mm) (not shown), which is biaxially stretched to a taut state before being connected to the bottom 1148 of the cylinder 1120. The piston shaft 1114 is made of a transparent polycarbonate (e.g., ) and has an overall length q of approximately 127 mm. The middle portion 1126 of the piston shaft 1114 has a diameter r of 22.15 (± 0.02) mm. The upper portion 1128 of the piston shaft 1114 has a diameter s of 15.8 mm, thereby forming the shoulder 1124. The lower portion 1146 of the piston shaft 1114 has a diameter t of approximately 5 / 8 inches (15.9 mm) and is threaded to be tightly screwed into the central hole 1218 of the piston head 1118 (see Figure 5 The piston head 1118 is perforated and made of a transparent polycarbonate (e.g., ) and is also screened with stretched stainless steel mesh (ISO 9044 material 1.4401, mesh size 0.038 mm, wire diameter 0.025 mm) (not shown). Weight 1112 is stainless steel with a central hole 1130, slides onto the upper portion 1128 of the piston shaft 1114 and rests on the shoulder 1124. The combined weight of the piston head 1118, piston shaft 1114, and weight 1112 is 596 g (± 6 g), which is equivalent to 0.30 psi on the inner area of ​​the cylinder 1120. The combined weight can be adjusted by drilling a blind hole down the central axis 1132 of the piston shaft 1114 to remove material and / or provide a cavity for adding weights. The cylinder cover 1116 has a first cover opening 1134 at its center for vertical alignment of the piston shaft 1114 and a second cover opening 1136 near the edge 1138 for introducing fluid from the constant static head reservoir 1014 into the cylinder 1120 .

[0158] A first linear indicator mark (not shown) is radially marked along the upper surface 1152 of the weight 1112, the first linear indicator mark being transverse to the central axis 1132 of the piston shaft 1114. A corresponding second linear indicator mark (not shown) is radially marked along the top surface 1160 of the piston shaft 1114, the second linear indicator mark being transverse to the central axis 1132 of the piston shaft 1114. A corresponding third linear indicator mark (not shown) is radially marked along the middle portion 1126 of the piston shaft 1114, the third linear indicator mark being parallel to the central axis 1132 of the piston shaft 1114. A corresponding fourth linear indicator mark (not shown) is radially marked along the upper surface 1140 of the cylinder cover 1116, the fourth linear indicator mark being transverse to the central axis 1132 of the piston shaft 1114. Furthermore, a corresponding fifth linear indicator mark (not shown) is marked along the lip 1154 of the cylinder cover 1116, the fifth linear indicator mark being parallel to the central axis 1132 of the piston shaft 1114. A corresponding sixth linear indicator mark (not shown) is scored along outer cylinder wall 1142 and is parallel to central axis 1132 of piston shaft 1114. Aligning the first, second, third, fourth, fifth, and sixth linear indicator marks allows weight 1112, piston shaft 1114, cylinder cover 1116, and cylinder 1120 to be repositioned with the same orientation relative to one another for each measurement.

[0159] Cylinder 1120 specification details are:

[0160] Outer diameter u of cylinder 1120: 70.35 mm (± 0.05 mm)

[0161] Inner diameter p of cylinder 1120: 60.0 mm (± 0.05 mm)

[0162] The height ν of the cylinder 1120 is 60.5 mm. The cylinder height must not be less than 55.0 mm!

[0163] The specifications of cylinder cap 1116 are as follows:

[0164] Outer diameter w of cylindrical cover 1116: 76.05 mm (± 0.05 mm)

[0165] Inner diameter x of cylindrical cover 1116: 70.5 mm (± 0.05 mm)

[0166] Thickness y of the cylindrical cover 1116 including the lip 1154: 12.7 mm

[0167] Thickness z of the drum cover 1116 without the lip 1154: 6.35 mm

[0168] Diameter a of the first cover opening 1134: 22.25 mm (± 0.02 mm)

[0169] Diameter b of the second cover opening 1136: 12.7 mm (± 0.1 mm)

[0170] Distance between the centers of the first cover opening 1134 and the second cover opening 1136:

[0171] 23.5mm

[0172] The specifications of weight 1112 are as follows:

[0173] Outer diameter c: 50.0mm

[0174] Diameter d of center hole 1130: 16.0 mm

[0175] Height e: 39.0mm

[0176] The specifications of piston head 1118 are as follows:

[0177] Diameter f: 59.7mm (±0.05mm)

[0178] Height g: 16.5mm. The piston head height must be no less than 15.0mm.

[0179] The outer holes 1214 (14 in total) have a diameter h of 9.30 (±0.25) mm and are equally spaced with the center being 23.9 mm from the center of the center hole 1218 .

[0180] The inner holes 1216 (7 in total) have a diameter i of 9.30 (±0.25) mm, and the inner holes 1216 are equally spaced, with their centers being 13.4 mm from the center of the center hole 1218.

[0181] The central bore 1218 has a diameter j of approximately 5 / 8 inch (15.9 mm) and is threaded to receive the lower portion 1146 of the piston shaft 1114 .

[0182] Before use, the stainless steel screens (not shown) of the piston head 1118 and cylinder 1120 should be checked for blockage, holes, or excessive stretching and replaced if necessary. A urine osmotic pressure measuring device with a damaged screen may output erroneous UPM results and should not be used until the screen is replaced.

[0183] A 5.00 cm mark 1156 is made on the cylinder 1120 at a height k of 5.00 cm (±0.05 cm) above the screen (not shown) attached to the bottom 1148 of the cylinder 1120. This marks the fluid level to be maintained during analysis. Maintaining a correct and constant fluid level (hydrostatic pressure) is critical to measurement accuracy.

[0184] The constant static head reservoir 1014 is used to deliver the saline solution 1032 to the cylinder 1120 and maintain the level of the saline solution 1032 at a height k of 5.00 cm above a screen (not shown) attached to the bottom 1148 of the cylinder 1120. The bottom 1034 of the inlet tube is positioned so as to maintain the level of the saline solution 1032 in the cylinder 1120 at the desired height k of 5.00 cm during measurement, i.e., the bottom 1034 of the inlet tube is located in approximately the same plane 1038 as the 5.00 cm mark 1156 on the cylinder 1120 when the cylinder is positioned on the cover plate 1047 and support ring 1040 (having a circular inner opening having a diameter of not less than 64 mm) above the receiving container 1024.

[0185] The cover plate 1047 and the support ring 1040 are components used in an apparatus for the method "K(t) test method (dynamic effective permeability and absorption kinetics measurement test method)" as described in EP 2 535 027 A1 and are referred to as " ” or “Time Dependent Permeability Tester”, equipment number 03-080578 and commercially available at BRAUN GmbH, Frankfurter Str. 145, 61476 Kronberg, Germany). Detailed technical drawings are also available upon request.

[0186] The proper height alignment of the air inlet tube with the 5.00 cm mark 1156 on the cylinder 1120 is critical for analysis. A suitable reservoir 1014 consists of a wide-mouth bottle 1030 containing a horizontally oriented L-shaped transfer tube 1018 connected to a flexible tube 1045 (e.g., Tygon tubing, capable of connecting the nozzle to the reservoir outlet) and a Tygon tubular nozzle 1044 (at least 6.0 mm inner diameter and approximately 5.0 cm long) for fluid transfer, a vertically oriented open-ended tube at a fixed height within the constant hydrostatic head reservoir 1014 for admitting air, and a stopcock 1012 for refilling the constant hydrostatic head reservoir 1014. The tube has an inner diameter of approximately 12 mm, but not less than 10.5 mm. The transfer tube 1018, located near the bottom 1042 of the constant hydrostatic head reservoir 1014, houses a stopcock 1020 for starting / stopping saline solution 1032 delivery. The outlet of the delivery flexible tube 1045 is sized (e.g., 10 mm outer diameter) to be inserted through the second cover opening 1136 on the cylinder cover 1116, with its end positioned below the surface of the saline solution 1032 in the cylinder 1120 (after the saline solution 1032 reaches a height of 5.00 cm in the cylinder 1120). The inlet tube is held in place by an O-ring gasket 1049. The constant static head reservoir 1014 can be positioned on the test stand 1016 at an appropriate height relative to the cylinder 1120. The components of the constant static head reservoir 1014 are sized to quickly fill the cylinder 1120 to the desired height (i.e., static head) and maintain that height throughout the measurement. The constant static head reservoir 1014 must be capable of delivering saline solution 1032 at a flow rate of at least 2.6 g / s for at least 10 minutes.

[0187] The piston / cylinder assembly 1028 is positioned on a support ring 1040 or a suitable alternative rigid support in the cover plate 1047. The saline solution 1032 that passes through the piston / cylinder assembly 1028, including the swollen hydrogel layer 1318, is collected in a receiving container 1024, which is positioned below (but not in contact with) the piston / cylinder assembly 1028.

[0188] The receiving container 1024 is placed on a balance 1026 accurate to at least 0.001 g. The digital output of the balance 1026 is connected to a computerized data acquisition system 1048.

[0189] Preparation of reagents (not shown)

[0190] Jayco Synthetic Urine (JSU) 1312 (See Figure 6) was used as the swelling phase (see UPM procedure below), and 1032 of a 0.118 M sodium chloride (NaCl) solution was used as the mobile phase (see UPM procedure below). The following preparations are based on a standard 1 liter volume. If preparing a volume other than 1 liter, all amounts were weighed accordingly.

[0191] JSU: Fill a 1 L volumetric flask to 80% of its volume with distilled water and place a magnetic stir bar inside the flask. Using an analytical balance, weigh the following dry ingredients to the nearest ±0.01 g using weighing paper or a beaker. Add them quantitatively to the flask in the same order listed below. Stir the solution on a suitable stir plate until all solids have dissolved. Remove the stir bar and dilute the solution to 1 L with distilled water. Replace the stir bar and continue stirring the solution for several minutes.

[0192] Amount of salt to prepare 1 liter of Jayco synthetic urine:

[0193] Potassium chloride (KCl) 2.00g

[0194] Sodium sulfate (Na2SO4) 2.00g

[0195] Ammonium dihydrogen phosphate (NH4H2PO4) 0.85g

[0196] Diammonium hydrogen phosphate ((NH4)2HPO4) 0.15g

[0197] Calcium chloride (CaCl2) 0.19g-[or calcium chloride hydrate (CaCl2·2H2O) 0.25g]

[0198] Magnesium chloride (MgCl2) 0.23g-[or hydrated magnesium chloride (MgCl2·6H2O) 0.50g]

[0199] To prepare more quickly, in a 1 L volumetric flask, potassium chloride, sodium sulfate, ammonium dihydrogen phosphate, ammonium phosphate (dibasic) and magnesium chloride (or hydrous magnesium chloride) are mixed and dissolved in 80% distilled water. Calcium chloride (or hydrous calcium chloride) is dissolved separately in approximately 50 ml of distilled water (e.g., in a glass beaker), and after the other salts are completely dissolved therein, the calcium chloride solution is transferred to a 1 L volumetric flask. Then, distilled water is added to 1 L (1000 ml ± 0.4 ml) and the solution is stirred for a few more minutes. Jayco synthetic urine can be stored in a clean plastic container for 10 days. If the solution becomes cloudy, it should not be used.

[0200] 0.118 M Sodium Chloride (NaCl) Solution: Use 0.118 M sodium chloride as salt solution 1032. Using weighing paper or a beaker, weigh 6.90 g (± 0.01 g) of sodium chloride and quantitatively transfer it to a 1 L volumetric flask (1000 ml ± 0.4 ml). Fill the flask to volume with distilled water. Add a stir bar and stir the solution on a stir plate until all solids have dissolved.

[0201] The conductivity of the prepared Jayco solution must be in the range of about 7.48-7.72 mS / cm, and the conductivity of the prepared 0.118 M sodium chloride (NaCl) solution must be in the range of about 12.34 mS / cm to 12.66 mS / cm (e.g., measured via a COND 70 instrument (#50010522) without CELL, equipped with a Cell VPT51-01C=0.1 from xs instruments, or via a LF 320 / Set, #300243, equipped with a TetraCon 325 from WTW, or via a COND 330i, #02420059, equipped with a TetraCon 325 from WTW). The surface tension of each solution must be in the range of 71-75 mN / m (measured, for example, via a tensiometer K100 from Kruess with a Pt plate).

[0202] Test Preparation

[0203] Using a solid reference cylindrical weight (not shown) (50 mm diameter, 128 mm height), set a caliper (not shown) (measuring range 25 mm, accurate to 0.01 mm, piston pressure maximum 0.50 g; e.g., a Mitutoyo digital height gauge) to read zero. This operation is conveniently performed on a smooth, level work surface (not shown) that is at least approximately 11.5 cm x 15 cm. Position the piston / cylinder assembly 1028, without superabsorbent polymer particles, under the caliper (not shown) and record the reading L1 to the nearest 0.01 mm.

[0204] The constant static head reservoir 1014 is filled with saline solution 1032. The bottom 1034 of the inlet tube is positioned so as to maintain the top (not shown) of the liquid meniscus (not shown) in the cylinder 1120 at the 5.00 cm mark 1156 during the measurement. Proper height alignment of the inlet tube at the 5.00 cm mark 1156 on the cylinder 1120 is critical to the analysis.

[0205] The receiving container 1024 is placed on a balance 1026, and the digital output of the balance 1026 is connected to a computerized data acquisition system 1048. A cover plate 1047 having a support ring 1040 is positioned over the receiving container 1024.

[0206] UPM Program

[0207] 1.5 g (± 0.05 g) of superabsorbent polymer particles are weighed onto a suitable weighing paper or weighing aid using an analytical balance. The moisture content of the superabsorbent polymer particles is measured according to the EDANA moisture content test method NWSP 230.0.R2 (15) or via a moisture analyzer (HX204, from Mettler Toledo, drying temperature 130° C., starting superabsorbent polymer particle weight 3.0 g (± 0.5 g), stop standard 1 mg / 140 s). If the moisture content of the superabsorbent polymer particles is greater than 3% by weight, the superabsorbent polymer particles are dried to a moisture content of <3% by weight, for example in an oven at 105° C. for 3 h or, for example, at 120° C. for 2 h. If the moisture content is greater than 5% by weight, the agglomerated superabsorbent polymer particles are dried, for example, in an oven at 105° C. for 3 h or, for example, at 120° C. for 2 h.

[0208] Empty cylinder 1120 is placed on horizontal workbench 1046 (not shown), and superabsorbent polymer particles are quantitatively transferred into cylinder 1120. Superabsorbent polymer particles are evenly dispersed on the screen (not shown) of the bottom 1148 attached to cylinder 1120, while cylinder 1120 is rotated, for example, via (manual or electric) turntable (for example, petriturn-E or petriturn-M, deriving from Schuett) assistance. The uniform distribution of particles on the screen (not shown) of the bottom 1148 connected to cylinder 1120 is very important, to obtain the highest precision result. After superabsorbent polymer particles have been evenly distributed on the screen (not shown) of the bottom 1148 attached to cylinder 1120, particles must not adhere to inner cylinder wall 1150. Insert piston shaft 1114 through first cover opening 1134, wherein the lip 1154 of cover 1116 faces piston head 1118. Carefully insert piston head 1118 into cylinder 1120 to a depth of several centimeters. Then place cap 1116 on the upper edge 1144 of cylinder 1120, while carefully keeping piston head 1118 away from superabsorbent polymer particles. Weight 1112 is placed on the top 1128 of piston shaft 1114 so that it rests on shoulder 1124 so that the first and second linear indicator marks are aligned. Then carefully rotate cap 1116 and piston shaft so that the third, fourth, fifth and sixth linear indicator marks are aligned and then aligned with the first and second linear indicator marks. Then gently lower piston head 1118 (by piston shaft 1114) to rest on dry superabsorbent polymer particles. The proper position of cap 1116 prevents the adhesion of weights on hydrogel layer 1318 and ensures uniform distribution.

[0209] Swelling phase :

[0210] A fritted disk 1310 of at least 8 cm in diameter (e.g., 8-9 cm in diameter) and at least 5.0 mm thick (e.g., 5-7 mm thick) with a "coarse" or "extra-coarse" porosity (e.g., Chemglass Inc. #CG 201-51, coarse porosity; or, e.g., Robu 1680, porosity 0) is placed in a wide, flat-bottomed petri dish 1314 and JSU 1312 is added by pouring it into the center of the fritted disk 1310 until the JSU 1312 reaches the top surface 1316 of the fritted disk 1310. The height of the JSU must not be greater than the height of the fritted disk 1310. It is important to avoid any air or bubbles being trapped in the fritted disk 1310 or the bottom layer.

[0211] The entire piston / cylinder assembly 1028 is lifted and placed on the fritted disk 1310 in the culture dish 1314. The JSU 1312 from the culture dish 1314 passes through the fritted disk 1310 and is absorbed by the superabsorbent polymer particles (not shown) to form a hydrogel layer 1318. The JSU 1312 available in the culture dish 1314 should be sufficient for all swelling phases. If necessary, more JSU 1312 can be added to the culture dish 1314 during hydration to maintain the JSU 1312 level at the top surface 1316 of the fritted disk 1310. After a period of 60 minutes, the piston / cylinder assembly 1028 is removed from the fritted disk 1310, taking care to ensure that the hydrogel layer 1318 does not lose JSU 1312 or absorb air during this step. The piston / cylinder assembly 1028 is placed under a calliper (not shown) and the reading L2 is recorded to the nearest 0.01 mm. If the reading changes over time, only the initial value is recorded. The thickness L0 of the hydrogel layer 1318 is determined by L2-L1, with an accuracy of 0.1 mm.

[0212] Transfer the piston / cylinder assembly 1028 to the support ring 1040 in the cover plate 1047. Position the constant static head reservoir 1014 so that the Tygon tubular nozzle 1044 is placed through the second cover opening 1136. Begin the measurement in the following order:

[0213] a) Open the stopcock 1020 of the constant hydrostatic head reservoir 1014 to allow the saline solution 1032 to reach the 5.00 cm mark 1156 on the cylinder 1120. This saline solution 1032 level should be achieved within 10 seconds of opening the stopcock 1020.

[0214] b) Once 5.00 cm of saline solution 1032 is obtained, the data collection procedure is initiated.

[0215] The mass of saline solution 1032 (in grams, to 0.001 grams) that passed through the hydrogel layer 1318 was recorded at 20-second intervals for 10 minutes using a computer 1048 attached to a balance 1026. At the end of the 10 minutes, the stopcock 1020 on the constant hydrostatic head reservoir 1014 was closed.

[0216] The UPM calculation uses data from 60 seconds to the end of the experiment. Data collected before 60 seconds are not included in the calculation.

[0217] For each 20-second period after the initial 60 seconds of the experiment (time t (i-1) to t i ), the corresponding flow rate Fs (t) (in g / s) and the corresponding midpoint in time t (1 / 2)t (in s) is calculated according to the following formula:

[0218]

[0219] Each time interval (t (i-1) to t i ) flow rate Fs (t) Relative to each time interval (t (i-1) to t i ) at the midpoint of time t (1 / 2) The intercept was calculated as Fs(t=0).

[0220] Calculation of the intercept :

[0221] The intercept is calculated by the best fit regression line, for example as follows: The formula for the regression line intercept a is:

[0222] a=y 平均 -b·x 平均 (XIII)

[0223] The slope b is calculated as:

[0224]

[0225] And where x 平均 and y 平均 are the sample means, i.e. the average of known_x and the average of known_y.

[0226] Calculation of urine osmotic pressure Q :

[0227] The intercept Fs(t=0) is used to calculate Q according to the following formula:

[0228]

[0229] where the flow rate Fs (t=0) is given in g / s, L0 is the initial thickness of the hydrogel layer 1318 in cm, and ρ is the density of the saline solution 1032 in g / cm 3 Units (e.g., 1.003 g / cm at room temperature 3 ). A (derived from the above formula) is in cm 2 The area of ​​the hydrogel layer 1318 (e.g., 28.27 cm 2 ), ΔP is in dynes / cm 2 The hydrostatic pressure of the gauge (e.g. 4920 dynes / cm 2 ), and urine osmotic pressure Q is measured in cm 3 The unit is sec / g. The average value of three measurements should be recorded.

[0230]

[0231] Capacity as described in EDANA NWSP 241.0.R2(15) Centrifuge retention capacity (CRC) Test Method Determination: Unlike EDANA NWSP 241.0.R2 (15), the CRC measurement starts at a lower limit of 24.2 g / g (instead of 27.19 g / g as stated in EDANA NWSP 241.0.R2 (15)).

[0232] In EDANA method NWSP 242.0.R2 (15) Absorption Against Pressure (AAP) Test Method: Unlike the EDANA method, a pressure of 0.7 psi was applied (instead of the 0.3 psi pressure provided in EDANA method NWSP 242.0.R2 (15)).

[0233] Amount of extractables Measured according to EDANA test method NWSP 270.0.R2(15). The following differences from EDANA test method NWSP 270.0.R2(15) apply to this article:

[0234] 9. Procedure (Procedural steps not described below are to be performed without deviating from EDANA test method NWSP 270.0.R2 (15)):

[0235] 9.2 Add exactly 200.0 ± 0.1 ml of saline solution to a 200 ml dispenser (not to a 250 ml beaker or Erlenmeyer flask as described in EDANA test method NWSP 270.0.R2 (15)).

[0236] 9.4 The saline solution was added to the 250 ml Erlenmeyer flask by weighing 0.95-1.05 g of the SAP granules sample directly into the flask and adding a magnetic coin (rather than adding the sample to a weighing container or laboratory paper and weighing the balance again as described in EDANA test method NWSP 270.0.R2 (15)). The flask was filled with saline solution only at the beginning of the extraction time.

[0237] 9.7 Stopper / cover / close beaker or Erlenmeyer flask and run at 250 ± 50 r.min -1 The solution was stirred at a rate of 100 μg / min for 16 hours (instead of 1 hour as described in EDANA test method NWSP 270.0.R2 (15)).

[0238] 9.8 Prepare a titration blank by treating 200.0 ± 0.1 ml of the same batch of saline solution as used for sample preparation in the same manner. Differences from EDANA test method NWSP 270.0.R2 (15): n = 2.

[0239] 9.9 Stop stirring the solution and filter the extracted sample directly through the flask covered with mesh (CCRC flask) with no downtime (instead of allowing the gel to completely settle to the bottom of the flask as described in EDANA test method NWSP 270.0.R2 (15)).

[0240] Example

[0241] Various examples of the present invention as well as comparative examples have been prepared and evaluated.

[0242] The difference of the embodiment of the present invention is that

[0243] a) Calculated as a mole percentage of carbon-carbon double bonds contained in the s-PAA polymer used to prepare SAP particles

[0244] b) The weight average molecular weight M of s-PAA polymer w count

[0245] c) The amount of s-PAA polymer used to prepare the SAP particles (in wt%) is 5 wt% to 66.7 wt%

[0246] d) in s-PAA polymer sources (i.e., s-PAA polymers obtained from different SAP particle degradation processes), and

[0247] e) The amount of crosslinking agent added during the process of preparing the SAP particles, including two examples (A8 and A9) in which no crosslinking agent is provided (i.e., only crosslinking agents are provided through s-

[0248] PAA polymer promotes cross-linking).

[0249] Comparative Examples were prepared using no s-PAA polymer at all (Comparative Examples C1, C2, and C7), or using commercially available s-PAA polymers in which no carbon-carbon double bonds were detected (Comparative Examples C3 to C6). This finding confirms the understanding that commercially available s-PAA polymers do not contain any carbon-carbon double bonds.

[0250]

[0251] Preparation of Base Polymer BP C1 / 7 of Comparative Examples C1 and C7

[0252] A 20,000 ml resin kettle (equipped with a four-necked glass stopper sealed with a septum, suitable for accommodating a thermometer and a syringe needle) was charged with approximately 5097.0 g of ice (approximately 50% of the total ice volume: 9676.1 g of ice prepared from deionized water). A magnetic stirrer capable of mixing the entire contents (when liquid) was added and stirring was initiated.

[0253] Take about 200.0 g of deionized water to dissolve 5.181 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass beaker of, for example, 250 ml volume. Close the container containing the "KPS" solution and set aside.

[0254] Take about 10.0 g of deionized water to dissolve 0.112 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 ml volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0255] Take 200.0 g of deionized water to dissolve 33.589 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn about 700 Da, from Sigma Aldrich) in, for example, a glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0256] The entire amount of 4600.3 g of glacial AA (=acrylic acid) was added to the ice in the resin kettle while continuing to stir.

[0257] A thermometer was inserted and a total of 3472.6 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) and the remaining amount of ice (prepared from deionized water) were subsequently added portionwise, bringing the temperature below 30°C.

[0258] While continuing to stir, add the PEG700-DA solution to the mixture of AA, NaOH solution, and ice at approximately 30°C. Wash the beaker containing the PEG700-DA solution twice with deionized water, using approximately 10% of the volume of the PEG700-DA solution for each wash. Add the wash water from both washes to the stirred mixture.

[0259] Deionized water (the remaining amount required to achieve a total of 11888.3 g (ice + water)) was added to the stirred mixture.

[0260] The resin kettle is then closed and the pressure is released, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar through an 80 cm syringe needle while stirring at approximately 400-600 RPM. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0261] 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 a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge. Then, about 0.022 g of a 1% w aqueous hydrogen peroxide H2O2 solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and the latter was then added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge.

[0262] After the initiator solutions "KPS" and "ASC" were mixed with the reaction mixture, stirring and argon purging were continued, but the argon needle was held a few centimeters above the liquid. Within 5 minutes of adding the "KPS" solution, the solution characteristically began to become cloudy or a sudden increase in viscosity was observed. The "gel point" was observed and recorded when the stir bar could no longer rotate freely at the bottom of the resin pot and stirring was therefore stopped. The argon purge was continued at a reduced flow rate (0.2 bar).

[0263] The temperature is monitored; typically it rises from about 20° C. to about 80° C. within 60 minutes. Once the temperature begins to drop from the maximum, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0264] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0265] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0266] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, at 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 10 minutes) into the following particle size fractions with the following yields:

[0267]

[0268]

[0269] The fractions "fines" and "crude" were discarded and not used further.

[0270] Preparation of Base Polymer BP C2 of Comparative Example C2

[0271] A 20,000 mL resin kettle (equipped with a four-necked glass stopper sealed with a septum, suitable for accommodating a thermometer and a syringe needle) was charged with approximately 4528.9 g of ice (approximately 50% of the total ice volume: 8941.1 g of ice prepared from deionized water). A magnetic stirrer capable of mixing the entire contents (when liquid) was added and stirring was initiated.

[0272] Take about 200.0 g of deionized water to dissolve 5.177 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass beaker of, for example, 250 mL volume. Close the container containing the "KPS" solution and set aside.

[0273] Take about 10.0 g of deionized water to dissolve 1.124 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0274] Take 200.0 g of deionized water to dissolve 80.44 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn of about 700 Da, from Sigma Aldrich) in, for example, a glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0275] The entire amount of 4600.0 g of glacial AA (=acrylic acid) was added to the ice in the resin kettle while continuing to stir.

[0276] A thermometer was inserted and a total of 3472.7 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) and the remaining amount of ice (prepared from deionized water) were subsequently added portionwise, bringing the temperature below 30°C.

[0277] While continuing to stir, add the PEG700-DA solution to the mixture of AA, NaOH solution, and ice at approximately 30°C. Wash the beaker containing the PEG700-DA solution twice with deionized water, using approximately 10% of the volume of the PEG700-DA solution for each wash. Add the wash water from both washes to the stirred mixture.

[0278] The remainder of the deionized water required to achieve a total amount of 11838.6 g (ice + water) was added to the stirred mixture.

[0279] The resin kettle is then closed and the pressure is released, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at about 0.4 bar through an 80 cm syringe needle while stirring at about 400°C. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0280] 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 a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while stirring and continuing the argon purge. Then, about 0.25 g of a 1% w aqueous hydrogen peroxide H2O2 solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and the latter was then also added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while stirring and continuing the argon purge.

[0281] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is pulled a few centimeters above the liquid. Typically, within 2 minutes of adding the "KPS" solution, typically at a temperature of about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. When the stirring rod cannot rotate freely at the bottom of the resin pot and stirring is therefore stopped, the "gel point" is observed and recorded. The argon purge is continued at a reduced flow rate (0.2 bar).

[0282] The temperature is monitored; typically it rises from about 20° C. to about 80° C. within 60 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0283] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0284] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0285] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, and a rotation speed of 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0286] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 4200g

[0287] The fractions "fines" and "crude" were discarded and not used further.

[0288] Preparation of Base Polymer BP C3 of Comparative Example C3

[0289] A 2,000 ml resin kettle (fitted with a four-necked glass lid sealed with a septum, suitable for accommodating a thermometer and syringe needle) was placed in an ice bath containing approximately 1 liter of water, 100 g of sodium chloride, and approximately 200 g of ice, such that the mixture covered approximately half the kettle's height. Approximately 80.0 g of a solution containing approximately 35% w / w aqueous polyacrylic acid (s-PAA polymer), with a weight-average molecular weight (Mw) of 100,000 Da as reported by the supplier, Sigma Aldrich, was added to the kettle. Approximately 591.4 g of water was added as ice prepared from DI water, and approximately 443.6 g of DI water was also added to the mixture. A magnetic stirrer capable of mixing the entire contents was added and stirring was initiated.

[0290] When the PAA is completely dispersed, the entire amount of 432.5 g of glacial AA (=acrylic acid) is added to the PAA solution in the resin kettle while continuing to stir.

[0291] Take about 20.0 g of deionized water to dissolve 0.4870 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in, for example, a 40 mL volume glass vial. The container with the "KPS" solution is closed with a plastic snap cap and set aside.

[0292] Take about 10.0 g of deionized water to dissolve 0.053 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0293] Take about 70 g of deionized water to dissolve 3.15 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn about 700 Da, from Sigma Aldrich) in, for example, a 100 mL glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0294] The remaining water, to a final weight of 1136.3 g, was added to the resin kettle and stirring was continued to obtain a homogeneous solution within 1-5 minutes.

[0295] A thermometer was inserted and a total of 347.5 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were subsequently added portionwise, bringing the temperature below 30°C.

[0296] While continuing to stir, the "PEG700-DA" solution was added to the mixture of AA, NaOH solution and ice at a temperature of about 30°C.

[0297] The resin kettle is then closed, the ice bath below is removed and the pressure is relieved, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar via an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0298] Then, after about 1 hour of argon purging and stirring, about 0.026 g (about 1-2 drops) of a 1% w aqueous hydrogen peroxide solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and then the latter was added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge. Thereafter, the "ASC" solution was added to the reaction mixture at a temperature of about 20° C. via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge.

[0299] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is held a few centimeters above the liquid. Typically, within 3 minutes of adding the "ASC" solution, typically at about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. The "gel point" is observed and recorded when the stir bar no longer rotates freely at the bottom of the resin pot and stirring is therefore stopped. Argon purging is continued at a reduced flow rate (0.2 bar).

[0300] The temperature is monitored; typically it rises from about 20° C. to about 70° C. within 60 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0301] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0302] The residual moisture content of the dried gel is less than about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0303] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, and a rotation speed of 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0304] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 350g

[0305] The fractions "fines" and "crude" were discarded and not used further.

[0306] Preparation of Base Polymer BP C4 of Comparative Example C4

[0307] A 10,000 mL resin kettle (equipped with a four-necked glass stopper sealed with a septum, suitable for accommodating a thermometer and a syringe needle) was charged with approximately 2392.1 g of ice (approximately 60% of the total ice volume: 3622.5 g of ice prepared from deionized water). A magnetic stirrer capable of mixing the entire contents (when liquid) was added and stirring was initiated.

[0308] Take about 100.0 g of deionized water to dissolve 2.296 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass beaker of, for example, 250 mL volume. Close the container containing the "KPS" solution and set aside.

[0309] Take about 10.0 g of deionized water to dissolve 0.492 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0310] Take 200.0 g of deionized water to dissolve 14.71 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn of about 700 Da, from Sigma Aldrich) in, for example, a glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0311] The entire amount of 2020.3 g of glacial AA (=acrylic acid) was added to the ice in the resin kettle while continuing to stir.

[0312] An amount of 798.5 g of a solution comprising polyacrylic acid in water at a concentration of about 35%w (Sigma Aldrich), with a weight average molecular weight Mw of 100,000 Da as reported by the supplier Sigma Aldrich, was added to the mixture in the resin kettle while continuing to stir.

[0313] A thermometer was inserted and a total of 1735.5 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) and the remaining amount of ice (prepared from deionized water) were subsequently added portionwise, bringing the temperature below 30°C.

[0314] While continuing to stir, add the PEG700-DA solution to the mixture of AA, NaOH solution, and ice at approximately 30°C. Wash the beaker containing the PEG700-DA solution twice with deionized water, using approximately 10% of the volume of the PEG700-DA solution for each wash. Add the wash water from both washes to the stirred mixture.

[0315] Deionized water (the remaining amount required to achieve a total of 5429.5 g (ice + water)) was added to the stirred mixture.

[0316] The resin kettle is then closed and the pressure is released, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar through an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0317] 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 a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while stirring and continuing the argon purge. Then, about 0.99 g of a 1% w aqueous hydrogen peroxide H2O2 solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and the latter was then added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while stirring and continuing the argon purge.

[0318] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is pulled a few centimeters above the liquid. Typically, within 2 minutes of adding the "KPS" solution, typically at a temperature of about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. When the stirring rod cannot rotate freely at the bottom of the resin pot and stirring is therefore stopped, the "gel point" is observed and recorded. The argon purge is continued at a reduced flow rate (0.2 bar).

[0319] The temperature is monitored; typically it rises from about 20° C. to about 80° C. within 60 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0320] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0321] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0322] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR 100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, at 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0323] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 2100g

[0324] The fractions "fines" and "crude" were discarded and not used further.

[0325] Preparation of base polymer BP C5 of comparative example C5

[0326] A 2,000 ml resin kettle (equipped with a four-necked glass lid closed with a septum, suitable for accommodating a thermometer and syringe needle) was placed in an ice bath containing approximately 1 liter of water, 100 g of sodium chloride, and approximately 200 g of ice, such that the mixture covered approximately half the height of the kettle. Approximately 80.0 g of a solution comprising an aqueous solution of polyacrylic acid (PAA) at a concentration of approximately 35% w / w, with a weight average molecular weight (Mw) of 223 kDa as determined by gel permeation chromatography and size exclusion chromatography (test method as described above) was added to the kettle. Approximately 496.6 g of water was added as ice prepared from DI water, and approximately 497.5 g of DI water was also added to the mixture. A magnetic stirrer capable of mixing the entire contents was added and stirring was initiated.

[0327] When the PAA is completely dispersed, the entire amount of 432.5 g of glacial AA (=acrylic acid) is added to the PAA solution in the resin kettle while continuing to stir.

[0328] Take about 13.6 g of deionized water to dissolve 0.4874 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. Close the container with the "KPS" solution with a plastic snap cap and set aside.

[0329] Take about 10.0 g of deionized water to dissolve 0.0529 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0330] Take about 115 g of deionized water to dissolve 3.15 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn about 700 Da, from Sigma Aldrich) in, for example, a 250 mL glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0331] The remaining 3.60 g of water for a final weight of 1136.3 g was added to the resin kettle and stirring was continued to obtain a homogeneous solution within 1-5 minutes.

[0332] A thermometer was inserted and a total of 347.6 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were subsequently added portionwise, bringing the temperature below 30°C.

[0333] While continuing to stir, the "PEG700-DA" solution was added to the mixture of AA, NaOH solution and ice at a temperature of about 30°C.

[0334] The resin kettle is then closed, the ice bath below is removed and the pressure is relieved, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar via an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0335] Then, after about a minimum of 10 minutes to 1 hour of argon purging and stirring, about 0.03 g (about 1-2 drops) of a 1% w aqueous hydrogen peroxide H2O2 solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and then the latter was added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge. Thereafter, the "ASC" solution was added to the reaction mixture at a temperature of about 20°C via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge.

[0336] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is held a few centimeters above the liquid. Typically, within 3 minutes of the "ASC" solution, typically at about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. The "gel point" is observed and recorded when the stir bar no longer rotates freely at the bottom of the resin pot and stirring is therefore stopped. The argon purge is continued at a reduced flow rate (0.2 bar).

[0337] The temperature is monitored; typically it rises from about 20° C. to about 70° C. within 60 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0338] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0339] The residual moisture content of the dried gel is less than about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0340] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR 100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, at 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0341] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 350g

[0342] The fractions "fines" and "crude" were discarded and not used further.

[0343] Preparation of base polymer BP C6 of comparative example C6

[0344] A 10,000 mL resin kettle (equipped with a four-necked glass stopper sealed with a septum, suitable for accommodating a thermometer and a syringe needle) was charged with approximately 2536.1 g of ice (approximately 60% of the total ice volume: 3050.3 g of ice prepared from deionized water). A magnetic stirrer capable of mixing the entire contents (when liquid) was added and stirring was initiated.

[0345] Take about 100.0 g of deionized water to dissolve 2.599 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass beaker of, for example, 250 mL volume. Close the container containing the "KPS" solution and set aside.

[0346] Take about 10.0 g of deionized water to dissolve 0.566 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0347] Take 200.0 g of deionized water to dissolve 16.76 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn of about 700 Da, from Sigma Aldrich) in, for example, a glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0348] The entire amount of 2300.1 g of glacial AA (=acrylic acid) was added to the ice in the resin kettle while continuing to stir.

[0349] An amount of 908.7 g of an aqueous solution of polyacrylic acid having a concentration of about 35% w PA 110S (BASF) was added to the mixture in the resin kettle while stirring was continued, with a weight average molecular weight Mw of 223 kDa as determined by gel permeation chromatography and reported by size exclusion chromatography (test method as described above).

[0350] A thermometer was inserted and a total of 1975.4 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) and the remaining amount of ice (prepared from deionized water) were subsequently added portionwise, bringing the temperature below 30°C.

[0351] While continuing to stir, add the PEG700-DA solution to the mixture of AA, NaOH solution, and ice at approximately 30°C. Wash the beaker containing the PEG700-DA solution twice with deionized water, using approximately 10% of the volume of the PEG700-DA solution for each wash. Add the wash water from both washes to the stirred mixture.

[0352] Deionized water (the remaining amount needed to achieve a total amount of 4795.0 g (ice + water)) was added to the stirred mixture.

[0353] The resin kettle is then closed and the pressure is released, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar through an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0354] 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 a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while stirring and continuing the argon purge. Then, about 1.90 g of a 1% w aqueous hydrogen peroxide H2O2 solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and the latter was then also added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while stirring and continuing the argon purge.

[0355] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is pulled a few centimeters above the liquid. Typically, within 2 minutes of adding the "KPS" solution, typically at a temperature of about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. When the stirring rod cannot rotate freely at the bottom of the resin pot and stirring is therefore stopped, the "gel point" is observed and recorded. The argon purge is continued at a reduced flow rate (0.2 bar).

[0356] The temperature is monitored; typically it rises from about 20° C. to about 80° C. within 60 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0357] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0358] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0359] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, and a rotation speed of 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0360] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 2100g

[0361] The fractions "fines" and "crude" were discarded and not used further.

[0362] The PAAs used in Examples A1 to A9 were obtained from the degradation of pre-existing SAP materials (i.e., from PAA A1 Procedure to PAA A9): Persulfate-mediated degradation of pre-existing SAP materials

[0363] The pre-existing SAP material used in all examples was a 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 water content of 0.4%, and a D50 average particle size of 398 μm, as measured according to ISO method 13322-2 (particle size distribution PSD of 63-710 μm). The SAP had an absorption against pressure (AAP) of 25.5 g / g, as determined by EDANA method WSP 442.2-02. In a deviation from EDANA WSP 442.2-02, a pressure of 0.7 psi was applied (whereas the EDANA method specifies a pressure of only 0.3 psi).

[0364] The deionized water used below was Millipore Q. The conductivity was measured using a laboratory conductivity meter COND 70 instrument (without CELL, #50010522, equipped with Cell VPT51-01 C=0.1, obtained from XS Instruments) or via LF 320 / Set (#300243, equipped with 325, obtained from WTW), the conductivity was <160 μS / cm at 0°C. Therefore, similar equipment for measuring conductivity can be used. The deionized water used in the examples represents the aqueous carrier. The actual amount of deionized water (= aqueous carrier) in the sample is shown in the "m_w_total" column in Table 1.

[0365] Unless otherwise stated, experimental procedures were performed in a climate-conditioned room under standard conditions of 23°C ± 2°C temperature and 45% ± 10% relative humidity.

[0366] program :

[0367] Preparation of potassium persulfate solution "KPS solution": Weigh the required amount (see table with experimental setup) of potassium persulfate (KPS) as a weight ml g of dry salt (Sigma-Aldrich, >= 99.0% purity, stock number 216224-500G) on a balance. Then add it to the respective grams of deionized water (i.e. in a 1 L plastic bottle (made of HDPE, Nalgene TM Complete dissolution of the KPS salt was observed when no visible salt crystals remained in solution.

[0368] Where hydrogen peroxide (HPO) was used, the corresponding amount of "KPS solution" as given in Table 2 below and designated as "mh" and the corresponding grams of 30 wt% HPO (also known as hydrogen peroxide, Sigma-Aldrich, stock number 216763-500ML) were added. The amount of "swelling solution" thus obtained (as given in Table 2 and designated as "ms1") was placed in a plastic bottle of appropriate size (2 to 5 L) (made of HDPE, Nalgene TM Manufacturing).

[0369] The amount of pre-existing dry SAP material (as given in Table 2 below and designated as "mSAP") is measured on a balance into a glass beaker of 500 mL volume and placed in a glass reactor or glass beaker of appropriate size (2 to 5 L) (e.g. manufactured by Normag GmbH or Pyrex, respectively). The corresponding amount of "swelling solution" is quickly added to the reactor together with the pre-existing SAP material without shaking, so that the dry pre-existing SAP material swells uniformly with the fluid to the corresponding degree of swelling, which is defined via x load in grams of swelling fluid per gram of dry pre-existing SAP material (x load is shown as xL in Table 2 below).

[0370] The reactor is sealed with a cap (standard cap with 4 openings, all of which are sealed with rubber stoppers). A syringe needle is placed in a rubber stopper to balance the pressure during heating. When using a glass beaker to replace the reactor, the beaker is covered with aluminum foil. A circulating oven (Binder FED720 model from Binder GmbH) is preheated to the temperature provided with " T1 " in the following table 2. When temperature T1 is reached, sealed reactor or beaker are placed in a baking oven, for the time period designated as " T1 " in the following table 2.

[0371] The reactor with the sample is taken out of the oven to cool. Depending on the size of the embodiment, the sample is filtered through a metal sieve with a 500 μm mesh (240 mm in diameter, from "Retch") placed on top of a 2-5 L plastic beaker. Filtration takes about 2 hours to allow the liquid to enter the collection container. The sample can be mixed with a spoon to increase the filtration rate. The yield after filtration is given as "Y1" in Table 2 below. (See table with experimental data). The extracted polymer is a clear solution. The pre-existing SAP material is a cross-linked network of polyacrylic acid, so the clear solution contains substantially soluble polyacrylic acid. The sample is transferred to one or more 2 L plastic bottles for further use.

[0372] An aliquot of the clear solution of mass ms_wet was measured into a pre-weighed 20 ml glass vial (without snap cap) via a 5 ml plastic syringe. The 20 ml vial with the clear solution was then placed in a vacuum oven (Heraeus Vacutherm model, Thermo Scientific) at 40° C. and a pressure of 5 to 50 mbar. TM ) for 3 hours to ensure significant evaporation of water. The dry polymer residue was weighed and its mass ms_dry was used to calculate the solid content S via the following formula:

[0373] S = ms_dry*100 / ms_wet, in %w

[0374]

[0375] Preparation of the base polymer BP A1 containing PAA A1 of Example A1

[0376] A 2,000 ml resin kettle (equipped with a four-necked glass lid closed with a septum, suitable for accommodating a thermometer and syringe needle) was placed in an ice bath containing approximately 1 liter of water, 100 g of sodium chloride, and approximately 200 g of ice, such that the mixture covered approximately half the kettle's height. Approximately 287.0 g of a solution comprising an approximately 9.74% w aqueous solution of polyacrylic acid PAA A1 obtained as described above, having a weight-average molecular weight (Mw) of 134 kDa as determined by gel permeation chromatography (testing method as described above), was added to the kettle. A magnetic stirrer capable of mixing the entire contents was added to the kettle and stirring was initiated.

[0377] The entire amount of 432.1 g of glacial AA (=acrylic acid) was added to the PAA solution in the resin kettle while continuing to stir.

[0378] Take about 10.0 g of deionized water to dissolve 0.012 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0379] Take about 30 g of deionized water to dissolve 3.15 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn about 700 Da, from Sigma Aldrich) in, for example, a 50 mL glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0380] The remaining amount of water to a final weight of 885.3 g was added to the resin kettle and stirring was continued to obtain a homogeneous solution within 5 minutes.

[0381] A thermometer was inserted and a total of 347.3 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were subsequently added portionwise, bringing the temperature below 30°C.

[0382] While continuing to stir, the "PEG700-DA" solution was added to the mixture of AA, NaOH solution and ice at a temperature of about 30°C.

[0383] The resin kettle is then closed, the ice bath below is removed and the pressure is relieved, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar via an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0384] After about a minimum of 10 minutes 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 a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge.

[0385] After the initiator solution "ASC" is mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is pulled a few centimeters above the liquid. Typically, within 1 minute of adding the "ASC" solution, typically at a temperature of about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. When the stir bar cannot rotate freely at the bottom of the resin pot and stirring is therefore stopped, the "gel point" is observed and recorded. The argon purge is continued at a reduced flow rate (0.2 bar).

[0386] The temperature is monitored; typically it rises from about 20° C. to about 70° C. within 20 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0387] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0388] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0389] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, and a rotation speed of 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0390] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 350g

[0391] The fractions "fines" and "crude" were discarded and not used further.

[0392] Preparation of the base polymer BP A2 containing PAA A2 of Example A2

[0393] A 2,000 ml resin kettle (equipped with a four-necked glass lid closed with a septum, suitable for accommodating a thermometer and syringe needle) was placed in an ice bath containing approximately 1 liter of water, 100 g of sodium chloride, and approximately 200 g of ice, such that the mixture covered approximately half the kettle's height. Approximately 274.7 g of a solution comprising an approximately 10.0% w aqueous solution of polyacrylic acid PAA A2 obtained as described above, having a weight-average molecular weight (Mw) of 277 kDa as determined by gel permeation chromatography (testing method as described above), was added to the kettle. A magnetic stirrer capable of mixing the entire contents was added to the kettle and stirring was initiated.

[0394] The entire amount of 432.0 g of glacial AA (=acrylic acid) was added to the PAA solution in the resin kettle while continuing to stir.

[0395] Take about 20.0 g of deionized water to dissolve 0.486 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "KPS" solution is closed with a plastic snap cap and set aside.

[0396] Take about 10.0 g of deionized water to dissolve 0.012 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0397] Take about 30 g of deionized water to dissolve 3.15 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn about 700 Da, from Sigma Aldrich) in, for example, a 50 mL glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0398] The remaining amount of water to a final weight of 975.2 g was added to the resin kettle and stirring was continued to obtain a homogeneous solution within 5 minutes.

[0399] A thermometer was inserted and a total of 313.6 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were subsequently added portionwise, bringing the temperature below 30°C.

[0400] While continuing to stir, the "PEG700-DA" solution was added to the mixture of AA, NaOH solution and ice at a temperature of about 30°C.

[0401] The resin kettle is then closed, the ice bath below is removed and the pressure is relieved, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar via an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0402] Then, after about a minimum of 10 minutes or a maximum of 1 hour of argon purging and stirring, about 0.025 g (about 1-2 drops) of a 1% w aqueous hydrogen peroxide H2O2 solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and then the latter was added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge. Thereafter, the "ASC" solution was added to the reaction mixture at a temperature of about 20°C via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge.

[0403] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is held a few centimeters above the liquid. Typically, within 6 minutes of adding the "ASC" solution, typically at about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. The "gel point" is observed and recorded when the stir bar no longer rotates freely at the bottom of the resin pot and stirring is therefore stopped. Argon purging is continued at a reduced flow rate (0.2 bar).

[0404] The temperature is monitored; typically it rises from about 20° C. to about 80° C. within 60 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0405] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0406] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0407] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR 100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, at 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0408] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 350g

[0409] The fractions "fines" and "crude" were discarded and not used further.

[0410] Preparation of the base polymer BP A3 containing PAA A3 of Example A3

[0411] A 2,000 ml resin kettle (fitted with a four-necked glass lid sealed with a septum, suitable for accommodating a thermometer and syringe needle) was placed in an ice bath containing approximately 1 liter of water, 100 g of sodium chloride, and approximately 200 g of ice, so that the mixture covered approximately half the kettle's height. Approximately 811.0 g of a solution containing an approximately 6.67% w aqueous solution of polyacrylic acid PAA A3, obtained as described above, with a weight-average molecular weight (Mw) of 517,500 kDa as determined by gel permeation chromatography (as described above) was added to the kettle. A 6.67% w aqueous solution of PAA A3 was prepared as a stock solution by diluting the 13.66% w solution with an appropriate amount of DI water and stirring overnight. A magnetic stirrer capable of mixing the entire contents (when liquid) was added to the kettle and stirring was initiated.

[0412] The entire amount of 405.9 g of glacial AA (=acrylic acid) was added to the PAA solution in the resin kettle while continuing to stir.

[0413] Take about 20.0 g of deionized water to dissolve 0.455 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. Close the container with the "KPS" solution with a plastic snap cap and set aside.

[0414] Take about 10.0 g of deionized water to dissolve 0.011 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0415] Take about 30 g of deionized water to dissolve 2.95 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn about 700 Da, from Sigma Aldrich) in, for example, a 50 mL glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0416] The remaining amount of water to a final weight of 497.7 g was added to the resin kettle and stirring was continued to obtain a homogeneous solution within 1-5 minutes.

[0417] A thermometer was inserted and a total of 281.8 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were subsequently added portionwise, bringing the temperature below 30°C.

[0418] While continuing to stir, the "PEG700-DA" solution was added to the mixture of AA, NaOH solution and ice at a temperature of about 30°C.

[0419] The resin kettle is then closed, the ice bath below is removed and the pressure is relieved, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar via an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0420] Then, after about a minimum of 10 minutes or a maximum of 1 hour of argon purging and stirring, about 0.025 g (about 1-2 drops) of a 1% w aqueous hydrogen peroxide H2O2 solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and then the latter was added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge. Thereafter, the "ASC" solution was added to the reaction mixture at a temperature of about 20°C via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge.

[0421] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is held a few centimeters above the liquid. Typically, within 4 minutes of adding the "ASC" solution, typically at about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. The "gel point" is observed and recorded when the stir bar no longer rotates freely at the bottom of the resin pot and stirring is therefore stopped. Argon purging is continued at a reduced flow rate (0.2 bar).

[0422] The temperature is monitored; typically it rises from about 20° C. to about 70° C. within 60 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0423] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0424] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0425] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, and a rotation speed of 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0426] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 350g

[0427] The fractions "fines" and "crude" were discarded and not used further.

[0428] Preparation of the base polymer BP A4 containing PAA A456 of Example A4

[0429] A 2,000 ml resin kettle (equipped with a four-necked glass lid closed with a septum, suitable for accommodating a thermometer and syringe needle) was placed in an ice bath containing approximately 1 liter of water, 100 g of sodium chloride, and approximately 200 g of ice, such that the mixture covered approximately half the kettle's height. Approximately 466.3 g of a solution comprising an approximately 10.78% w aqueous solution of polyacrylic acid PAA A456, obtained as described above, having a weight average molecular weight (Mw) of 285 Da as determined by gel permeation chromatography (testing method as described above), was added to the kettle. A magnetic stirrer capable of mixing the entire contents was added to the kettle and stirring was initiated.

[0430] The entire amount of 380.2 g of glacial AA (=acrylic acid) was added to the PAA solution in the resin kettle while continuing to stir.

[0431] Take about 20.0 g of deionized water to dissolve 0.431 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. Close the container with the "KPS" solution with a plastic snap cap and set aside.

[0432] Take about 10.0 g of deionized water to dissolve 0.047 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0433] Take about 30 g of deionized water to dissolve 2.77 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn about 700 Da, from Sigma Aldrich) in, for example, a 50 mL glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0434] The remaining amount of water to a final weight of 899.6 g was added to the resin kettle and stirring was continued to obtain a homogeneous solution within 5 minutes.

[0435] A thermometer was inserted and a total of 250.8 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were subsequently added portionwise, bringing the temperature below 30°C.

[0436] While continuing to stir, the "PEG700-DA" solution was added to the mixture of AA, NaOH solution and ice at a temperature of about 30°C.

[0437] The resin kettle is then closed, the ice bath below is removed and the pressure is relieved, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar via an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0438] After about a minimum of 10 minutes of argon purging and stirring, about 0.025 g (about 1-2 drops) of a 1% w aqueous hydrogen peroxide solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and then the latter was added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while continuing to stir and purge with argon. Thereafter, the "ASC" solution was added to the reaction mixture at a temperature of about 20° C. via a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while stirring and continuing to purge with argon.

[0439] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is held a few centimeters above the liquid. Typically, within 13 minutes of adding the "ASC" solution, typically at about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. The "gel point" is observed and recorded when the stir bar no longer rotates freely at the bottom of the resin pot and stirring is therefore stopped. Argon purging is continued at a reduced flow rate (0.2 bar).

[0440] The temperature is monitored; typically it rises from about 20° C. to about 60° C. within 90 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0441] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0442] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0443] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, and a rotation speed of 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0444] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 350g

[0445] The fractions "fines" and "crude" were discarded and not used further.

[0446] Preparation of the base polymer BP A5 containing PAA A456 of Example A5

[0447] A 2,000 ml resin kettle (fitted with a four-necked glass lid closed with a septum, suitable for accommodating a thermometer and syringe needle) was placed in an ice bath containing approximately 1 liter of water, 100 g of sodium chloride, and approximately 200 g of ice, such that the mixture covered approximately half the kettle's height. Approximately 1413.9 g of a solution comprising an approximately 10.78% w aqueous solution of polyacrylic acid PAA A456, obtained as described above, having a weight average molecular weight (Mw) of 285 Da as determined by gel permeation chromatography (testing method as described above), was added to the kettle. A magnetic stirrer capable of mixing the entire contents was added to the kettle and stirring was initiated.

[0448] The entire amount of 380.0 g of glacial AA (=acrylic acid) was added to the PAA solution in the resin kettle while continuing to stir.

[0449] Take about 20.0 g of deionized water to dissolve 0.348 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "KPS" solution is closed with a plastic snap cap and set aside.

[0450] Take about 10.0 g of deionized water to dissolve 0.085 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0451] Take about 30 g of deionized water to dissolve 1.20 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn about 700 Da, from Sigma Aldrich) in, for example, a 50 mL glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0452] The remaining amount of water to a final weight of 137.2 g was added to the resin kettle and stirring was continued to obtain a homogeneous solution within 5 minutes.

[0453] A thermometer was inserted and a total of 167.6 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were subsequently added portionwise, bringing the temperature below 30°C.

[0454] While continuing to stir, the "PEG700-DA" solution was added to the mixture of AA, NaOH solution and ice at a temperature of about 30°C.

[0455] The resin kettle is then closed, the ice bath below is removed and the pressure is relieved, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar via an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0456] After about a minimum of 10 minutes of argon purging and stirring, about 0.02 g (about 1-2 drops) of a 1% w aqueous hydrogen peroxide solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and then the latter was added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while continuing to stir and purge with argon. Thereafter, the "ASC" solution was added to the reaction mixture at a temperature of about 20° C. via a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while stirring and continuing to purge with argon.

[0457] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is held a few centimeters above the liquid. Typically, within 4 minutes of adding the "ASC" solution, typically at about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. The "gel point" is observed and recorded when the stir bar no longer rotates freely at the bottom of the resin pot and stirring is therefore stopped. Argon purging is continued at a reduced flow rate (0.2 bar).

[0458] The temperature is monitored; typically it rises from about 20° C. to about 35° C. within 90 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0459] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0460] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0461] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, and a rotation speed of 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0462] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 350g

[0463] The fractions "fines" and "crude" were discarded and not used further.

[0464] Preparation of the base polymer BP A6 containing PAA A456 of Example A6

[0465] A 2,000 ml resin kettle (equipped with a four-necked glass lid closed with a septum, suitable for accommodating a thermometer and syringe needle) was placed in an ice bath containing approximately 1 liter of water, 100 g of sodium chloride, and approximately 200 g of ice, such that the mixture covered approximately half the kettle's height. Approximately 740.5 g of a solution comprising an approximately 10.78% w aqueous solution of polyacrylic acid PAA A456, obtained as described above, having a weight average molecular weight (Mw) of 285 Da as determined by gel permeation chromatography (testing method as described above), was added to the kettle. A magnetic stirrer capable of mixing the entire contents was added to the kettle and stirring was initiated.

[0466] The entire amount of 380.1 g of glacial AA (=acrylic acid) was added to the PAA solution in the resin kettle while continuing to stir.

[0467] Take about 20.0 g of deionized water to dissolve 0.427 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "KPS" solution is closed with a plastic snap cap and set aside.

[0468] Take about 10.0 g of deionized water to dissolve 0.045 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0469] Take about 30 g of deionized water to dissolve 2.78 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn about 700 Da, from Sigma Aldrich) in, for example, a 50 mL glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0470] The remaining amount of water to a final weight of 625.4 g was added to the resin kettle and stirring was continued to obtain a homogeneous solution within 5 minutes.

[0471] A thermometer was inserted and a total of 250.8 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were subsequently added portionwise, bringing the temperature below 30°C.

[0472] While continuing to stir, the "PEG700-DA" solution was added to the mixture of AA, NaOH solution and ice at a temperature of about 30°C.

[0473] The resin kettle is then closed, the ice bath below is removed and the pressure is relieved, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar via an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0474] After about a minimum of 10 minutes of argon purging and stirring, about 0.025 g (about 1-2 drops) of a 1% w aqueous hydrogen peroxide solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and then the latter was added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while continuing to stir and purge with argon. Thereafter, the "ASC" solution was added to the reaction mixture at a temperature of about 20° C. via a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while stirring and continuing to purge with argon.

[0475] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is held a few centimeters above the liquid. Typically, within 9 minutes of adding the "ASC" solution, typically at about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. The "gel point" is observed and recorded when the stir bar no longer rotates freely at the bottom of the resin pot and stirring is therefore stopped. Argon purging is continued at a reduced flow rate (0.2 bar).

[0476] The temperature is monitored; typically it rises from about 20° C. to about 65° C. within 90 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0477] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0478] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0479] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, and a rotation speed of 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0480] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 350g

[0481] The fractions "fines" and "crude" were discarded and not used further.

[0482] Preparation of the base polymer BP A7 containing PAA A7 of Example A7

[0483] A 2,000 ml resin kettle (equipped with a four-necked glass lid closed with a septum, suitable for accommodating a thermometer and syringe needle) was placed in an ice bath containing approximately 1 liter of water, 100 g of sodium chloride, and approximately 200 g of ice, such that the mixture covered approximately half the kettle's height. Approximately 1192.7 g of a solution comprising an approximately 11.36% w aqueous solution of polyacrylic acid PAA A7, obtained as described above, having a weight average molecular weight (Mw) of 285 Da as determined by gel permeation chromatography (testing method as described above), was added to the kettle. A magnetic stirrer capable of mixing the entire contents was added to the kettle and stirring was initiated.

[0484] The entire amount of 460.1 g of glacial AA (=acrylic acid) was added to the PAA solution in the resin kettle while continuing to stir.

[0485] Take about 20.0 g of deionized water to dissolve 0.517 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "KPS" solution is closed with a plastic snap cap and set aside.

[0486] Take about 5.0 g of deionized water to dissolve 0.011 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0487] Take about 20 g of deionized water to dissolve 1.78 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn about 700 Da, from Sigma Aldrich) in, for example, a 50 mL glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0488] The remaining amount of water to a final weight of 55.4 g was added to the resin kettle and stirring was continued to obtain a homogeneous solution within 5 minutes.

[0489] A thermometer was inserted and a total of 289.6 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were subsequently added portionwise, bringing the temperature below 30°C.

[0490] While continuing to stir, the "PEG700-DA" solution was added to the mixture of AA, NaOH solution and ice at a temperature of about 30°C.

[0491] The resin kettle is then closed, the ice bath below is removed and the pressure is relieved, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar via an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0492] After about a minimum of 10 minutes of argon purging and stirring, about 0.020 g (about 1-2 drops) of a 1% w aqueous hydrogen peroxide solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and then the latter was added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while continuing to stir and purge with argon. Thereafter, the "ASC" solution was added to the reaction mixture at a temperature of about 20° C. via a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while stirring and continuing to purge with argon.

[0493] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is held a few centimeters above the liquid. Typically, within 3 minutes of adding the "ASC" solution, typically at about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. The "gel point" is observed and recorded when the stir bar no longer rotates freely at the bottom of the resin pot and stirring is therefore stopped. Argon purging is continued at a reduced flow rate (0.2 bar).

[0494] The temperature is monitored; typically it rises from about 20° C. to about 70° C. within 60 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0495] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0496] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0497] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR 100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, at 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0498] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 350g

[0499] The fractions "fines" and "crude" were discarded and not used further.

[0500] Preparation of the base polymer BP A8 containing PAA A8 of Example A8

[0501] A 2,000 ml resin kettle (equipped with a four-necked glass lid closed with a septum, suitable for accommodating a thermometer and syringe needle) was placed in an ice bath containing approximately 1 liter of water, 100 g of sodium chloride, and approximately 200 g of ice, such that the mixture covered approximately half the kettle's height. Approximately 1085.4 g of a solution comprising an approximately 14.34% w aqueous solution of polyacrylic acid PAA A8, obtained as described above, having a weight-average molecular weight (Mw) of 239 Da as determined by gel permeation chromatography (testing method as described above), was added to the kettle. A magnetic stirrer capable of mixing the entire contents was added to the kettle and stirring was initiated.

[0502] The entire amount of 530.0 g of glacial AA (=acrylic acid) was added to the PAA solution in the resin kettle while continuing to stir.

[0503] Take about 20.0 g of deionized water to dissolve 0.596 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "KPS" solution is closed with a plastic snap cap and set aside.

[0504] Take about 5.0 g of deionized water to dissolve 0.013 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0505] No additional cross-linker "PEG700-DA" (=polyethylene glycol diacrylate with Mn approximately 700 Da, from Sigma Aldrich) was added.

[0506] The remaining amount of water to a final weight of 49.92 g was added to the resin kettle and stirring was continued to obtain a homogeneous solution within 5 minutes.

[0507] A thermometer was inserted and a total of 334.1 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were subsequently added portionwise, bringing the temperature below 30°C.

[0508] The resin kettle is then closed, the ice bath below is removed and the pressure is relieved, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar via an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0509] After about a minimum of 10 minutes of argon purging and stirring, about 0.030 g (about 1-2 drops) of a 1% w aqueous hydrogen peroxide solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and then the latter was added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while continuing to stir and purge with argon. Thereafter, the "ASC" solution was added to the reaction mixture at a temperature of about 20° C. via a plastic funnel temporarily inserted into one of the necks of the resin pot lid, while stirring and continuing to purge with argon.

[0510] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is held a few centimeters above the liquid. Typically, within 4 minutes of adding the "ASC" solution, typically at about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. The "gel point" is observed and recorded when the stir bar no longer rotates freely at the bottom of the resin pot and stirring is therefore stopped. Argon purging is continued at a reduced flow rate (0.2 bar).

[0511] The temperature is monitored; typically it rises from about 20° C. to about 100° C. within 20 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0512] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0513] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0514] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR 100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, at 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0515] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 350g

[0516] The fractions "fines" and "crude" were discarded and not used further.

[0517] Preparation of the base polymer BP A9 containing PAA A9 of Example A9

[0518] About 896.7 g of a solution comprising an aqueous solution of polyacrylic acid PAA A9 obtained as described above at a concentration of about 17.10% w, wherein the weight average molecular weight Mw determined by gel permeation chromatography was 229 Da (test method as described above), was placed in a 2,000 ml resin kettle (equipped with a four-necked glass lid closed with a septum and suitable for introducing a thermometer and a syringe needle). A magnetic stirrer capable of mixing the entire contents was added to the resin kettle and stirring was initiated.

[0519] The entire amount of 76.6 g of glacial AA (=acrylic acid) was added to the PAA solution in the resin kettle while continuing to stir.

[0520] Take about 10.0 g of deionized water to dissolve 0.086 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "KPS" solution is closed with a plastic snap cap and set aside.

[0521] Take about 5.0 g of deionized water to dissolve 0.020 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0522] No additional cross-linker "PEG700-DA" (=polyethylene glycol diacrylate with Mn approximately 700 Da, from Sigma Aldrich) was added.

[0523] The remaining amount of water to a final weight of 26.83 g was added to the resin kettle and stirring was continued to obtain a homogeneous solution within 5 minutes.

[0524] Put a thermometer in. No more NaOH (sodium hydroxide) solution is added subsequently.

[0525] The resin kettle is then closed and the pressure is released, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar through an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0526] After about a minimum of 10 minutes of argon purging and stirring, the "ASC" solution was added to the "KPS" solution, and then the resulting mixture was added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge. The temperature of the reaction mixture was about 20°C.

[0527] After the initiator solution "KPS" (and the "ASC" solution therein) is mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is pulled a few centimeters above the liquid. Typically, within 2 minutes of adding the "ASC" solution, typically at a temperature of about room temperature, the solution characteristically becomes cloudy or a sudden increase in viscosity is observed. When the stirring rod cannot rotate freely at the bottom of the resin pot and stirring is therefore stopped, the "gel point" is observed and recorded. The argon purge is continued at a reduced flow rate (0.2 bar).

[0528] The temperature is monitored; it rises slightly from about 20° C. to about 31° C. within 20 minutes. As soon as the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0529] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0530] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0531] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR 100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, at 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0532] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 350g

[0533] The fractions "fines" and "crude" were discarded and not used further.

[0534] Procedure for obtaining the PAA used in Example A10 (=PAA A10) from the degradation of pre-existing SAP material: Exoray-mediated degradation of pre-existing SAP materials

[0535] Pre-existing SAP material for degradation (in the form of pre-existing SAP particles) is commercially available in Pampers Baby Dry sold in Germany in 2020.

[0536] The pre-existing SAP material was mixed with RO (reverse osmosis) water in a Quadro mixer to produce a feed stream (in gel form) having 2.5% wt SAP and 97.5% RO water. The initial viscosity of the gel was about 840 Pa.s. Approximately 140 mL of the feed stream was loaded into a syringe and fed to a Fusion UV curing system (FUSION UV SYSTEMS, Inc., Maryland, USA; Hg lamp (H-bulb) with a UV curing rate of 6 mL / min using a syringe pump (New Era Pump Systems, Inc., Farmdale, NY; Model NE-1000 single syringe pump) with a 6 mm outer diameter (OD) (3.68 mm inner diameter (ID)) quartz tube. 300 W / in. and 2.74 W / cm2 measured by #20082105A / B / C / V (EIT, Inc.; Sterling, VA) 2 The UV lamp was positioned perpendicular to the quartz tube. The length of the quartz tube exposed to UV radiation was estimated to be 15 cm, with the longitudinal axis of the quartz tube approximately 8 mm above the focal point of the UV lamp. The residence time of the feed stream in the irradiation zone was 16 s, and the UV radiation energy was calculated to be 1.4 MJ / kg SAP. The viscosity of the product stream was measured using a cup and swing fixture in steady-state mode and was found to be 155 mPa·s at 4 s.

[0537] Preparation of the base polymer BP A10 containing PAA A10 of Example A10

[0538] A 2,000 ml resin kettle (equipped with a four-necked glass lid closed with a septum, suitable for accommodating a thermometer and syringe needle) was placed in an ice bath containing approximately 1 liter of water, 100 g of sodium chloride, and approximately 200 g of ice, such that the mixture covered approximately half the height of the kettle. Approximately 1043.1 g of a solution comprising an approximately 2.68% w aqueous solution of PAA-A10 obtained as described above, having a weight average molecular weight (Mw) of 1,080 Da as determined by gel permeation chromatography (testing method as described above), was added to the kettle. A magnetic stirrer capable of mixing the entire contents (when liquid) was added to the kettle and stirring was initiated.

[0539] The entire amount of 432.1 g of glacial AA (=acrylic acid) was added to the PAA solution in the resin kettle while continuing to stir.

[0540] Take about 20.0 g of deionized water to dissolve 0.483 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "KPS" solution is closed with a plastic snap cap and set aside.

[0541] Take about 10.0 g of deionized water to dissolve 0.011 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0542] Take about 30 g of deionized water to dissolve 3.22 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn about 700 Da, from Sigma Aldrich) in, for example, a 50 mL glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0543] The remaining amount of water to a final weight of 174.0 g was added to the resin kettle and stirring was continued to obtain a homogeneous solution within 1-5 minutes.

[0544] A thermometer was inserted and a total of 347.2 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were subsequently added portionwise, bringing the temperature below 30°C.

[0545] While continuing to stir, the "PEG700-DA" solution was added to the mixture of AA, NaOH solution and ice at a temperature of about 30°C.

[0546] The resin kettle is then closed, the ice bath below is removed and the pressure is relieved, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar via an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0547] Then, after about 1 hour of argon purging and stirring, about 0.020 g (about 1-2 drops) of a 1% w aqueous hydrogen peroxide solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and then the latter was added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge. Thereafter, the "ASC" solution was added to the reaction mixture at a temperature of about 20° C. via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge.

[0548] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is held a few centimeters above the liquid. Typically, within 4 minutes of adding the "ASC" solution, typically at about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. The "gel point" is observed and recorded when the stir bar no longer rotates freely at the bottom of the resin pot and stirring is therefore stopped. Argon purging is continued at a reduced flow rate (0.2 bar).

[0549] The temperature is monitored; typically it rises from about 20° C. to about 80° C. within 60 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0550] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0551] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0552] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR 100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, at 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0553] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 350g

[0554] The fractions "fines" and "crude" were discarded and not used further.

[0555] Procedure for obtaining the PAA used in Example A11 (=PAA A11) from the degradation of pre-existing SAP material: Whistle (LW)-mediated mechanical degradation

[0556] Pre-existing SAP material for degradation (in the form of pre-existing SAP particles) is commercially available in Pampers Baby Dry sold in Germany in 2020.

[0557] The pre-existing SAP material was mixed with RO (= reverse osmosis) water in a stirred tank system similar to the EnSight Solutions Likwifier LORSS series equipped with an approximately 20-gallon working capacity tank, a top-mounted waste surface agitator, and a bottom 6-hole / 3-wing rotor-stator high shear impeller to produce a feed stream (in gel form) having 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 a liquid whistle device (LW; Sonolator Model A; Sonic Corp., Stratford, CT); the oval orifice dimensions were: width 2×0.0375 inches = 1.9 mm, height 2×0.012 inches = 0.6 mm (calculated hydraulic diameter 1.7 mm), segment length 1 mm, and volume V = π×(width)×(height)×(segment length) / 4 = 0.9 mm 3 ) (The oval orifice has a diameter of approximately 1.3 mm 2 The LW device was operated at a flow rate of about 8 L / min and a pressure of about 4,500 psi (about 310 bar), with the product stream being recycled back into the stirred tank system. The tank volume was passed through the LW device about 8 times, representing a total residence time in the LW chamber area of ​​about 40 ms (about 5 ms per pass). The energy density achieved by the mixing device was about 62 MJ / m 3 (approximately 2.48 MJ / kg SAP).

[0558] The actual final solids content of the product was determined to be 2.73 wt% by placing 3.00 g of product in a pre-weighed glass vial of 40 mL volume and placing the vial, uncovered, in a vacuum oven.

[0559] Preparation of the base polymer BP A11 containing PAA A11 of Example A11

[0560] A 2,000 ml resin kettle (equipped with a four-necked glass lid closed with a septum, suitable for accommodating a thermometer and syringe needle) was placed in an ice bath containing approximately 1 liter of water, 100 g of sodium chloride, and approximately 200 g of ice, such that the mixture covered approximately half the height of the kettle. Approximately 1024.0 g of a solution comprising an approximately 2.73% w aqueous solution of PAA A11 obtained as described above, having a weight average molecular weight (Mw) of 418 Da as determined by gel permeation chromatography (testing method as described above), was added to the kettle. A magnetic stirrer capable of mixing the entire contents (when liquid) was added to the kettle and stirring was initiated.

[0561] The entire amount of 432.1 g of glacial AA (=acrylic acid) was added to the PAA solution in the resin kettle while continuing to stir.

[0562] Take about 20.0 g of deionized water to dissolve 0.484 g of "KPS" (=potassium peroxodisulfate, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "KPS" solution is closed with a plastic snap cap and set aside.

[0563] Take about 10.0 g of deionized water to dissolve 0.012 g of "ASC" (=ascorbic acid, from Sigma Aldrich) in a glass vial of, for example, 40 mL volume. The container with the "ASC" solution is closed with a plastic snap cap and set aside.

[0564] Take about 30 g of deionized water to dissolve 3.14 g of "PEG700-DA" (= polyethylene glycol diacrylate with Mn about 700 Da, from Sigma Aldrich) in, for example, a 50 mL glass beaker. Cover the beaker with the "PEG700-DA" solution with parafilm and set aside.

[0565] The remaining amount of water to a final weight of 193.0 g was added to the resin kettle and stirring was continued to obtain a homogeneous solution within 1-5 minutes.

[0566] A thermometer was inserted and a total of 347.4 g of 50%w NaOH (sodium hydroxide) solution (for analysis, from Merck KGaA) were subsequently added portionwise, bringing the temperature below 30°C.

[0567] While continuing to stir, the "PEG700-DA" solution was added to the mixture of AA, NaOH solution and ice at a temperature of about 30°C.

[0568] The resin kettle is then closed, the ice bath below is removed and the pressure is relieved, for example, by piercing the septum with two syringe needles. The solution is then vigorously purged with argon at approximately 0.4 bar via an 80 cm syringe needle while stirring at approximately 400 rpm. The argon stream is placed close to the stirrer to effectively and quickly remove dissolved oxygen.

[0569] Then, after about 1 hour of argon purging and stirring, about 0.025 g (about 1-2 drops) of 1% w aqueous hydrogen peroxide H2O2 solution (Sigma-Aldrich) was added to the "KPS" solution via a 1 mL plastic pipette, and then the latter was added to the reaction mixture via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge. Thereafter, the "ASC" solution was added to the reaction mixture at a temperature of about 20°C via a plastic funnel temporarily inserted into one of the necks of the resin pot lid while stirring and continuing the argon purge.

[0570] After the initiator solutions "KPS" and "ASC" are mixed with the reaction mixture, stirring and argon purging are continued, but the argon needle is held a few centimeters above the liquid. Typically, within 3 minutes of adding the "ASC" solution, typically at about room temperature, the solution characteristically begins to become cloudy or a sudden increase in viscosity is observed. The "gel point" is observed and recorded when the stir bar no longer rotates freely at the bottom of the resin pot and stirring is therefore stopped. Argon purging is continued at a reduced flow rate (0.2 bar).

[0571] The temperature is monitored; typically it rises from about 20° C. to about 80° C. within 60 minutes. Once the temperature begins to drop from the maximum value, the resin kettle is transferred to a circulation oven (e.g., Binder FED 720 from Binder GmbH) and maintained at about 60° C. for about 18 hours.

[0572] The resin kettle of 100mg / ml is cooled to 400 DEG C and is kept in the baking oven for 2 hours.After this, close baking oven and make the resin kettle cool to approximately 2 hours simultaneously and remain in the baking oven.After this, take out gel, and manually fragment or be cut into smaller piece with scissors.Gel is ground with grinder (X70G from Scharfen Slicing Machines GmbH, it has Unger R70 plate system: 3 band diameters are the pre-cutter kidney-shaped plates of the straight hole of 17mm) grind, be placed on perforated stainless steel dish (aperture 4.8mm, 50cm * 50cm, 0.55mm caliper, 50% open area, from RS; The maximum height of gel before drying: approximately 3cm) and transfer in approximately 120 ℃ circulating oven (from the Binder FED720 of Binder GmbH) for approximately 20 hours.

[0573] The residual moisture content of the dried gel was about 3% by weight (see UPM test method for a description of how to determine the moisture content).

[0574] The dry gel was then ground using a centrifugal mill (Retsch ZM 200 from Retsch GmbH with a vibrating feeder DR 100 (setting 50-60), interchangeable sieves with a 1.5 mm opening setting, at 8000 rpm). The ground polymer was then sieved via a sieving machine (AS 400 control from Retsch with sieve DIN / ISO 3310-1, at about 250 rpm for about 5-10 minutes) into the following particle size fractions with the following yields:

[0575] powder Collected fractions Crude product Screening and classification <150μm 150-710μm >710μm Yield About 350g

[0576] The fractions "fines" and "crude" were discarded and not used further.

[0577] Surface crosslinking treatment of base polymer particles BPA1 to BPA11 and BPC1 / 7 to BP C6 (hereinafter referred to as "SXL") to obtain Examples A1 to A11 and Comparative Examples C1 to C7

[0578] Equipment List :

[0579] ○ Glassware, one-way pipettes, spatulas, and spoons to prepare solutions and weigh absorbent materials

[0580] ○Glass beaker: 250ml opening

[0581] ○Balance: Sartorius or equivalent; accuracy 0.01g

[0582] ○ Analytical balance: Mettler or equivalent; accuracy 0.0001g

[0583] Electric stand mixer: IKA Eurostar power-controlled (range 50-2000 rpm) or equivalent

[0584] ○With stirrer: PTFE Propeller stirrer 4 blades

[0585] ○Pipette: Eppendorf Multistream or equivalent

[0586] ○Aluminum foil for covering

[0587] Circulation oven: Binder FD 240 or equivalent

[0588] ○ Moisture measurement equipment: Halogen moisture balance Mettler or equivalent

[0589] ○ Screening machine: Retch AS200 control "g" or equivalent

[0590] ○ With sieve: stainless steel: DIN / ISO 3310-1

[0591] Solution preparation :

[0592] Aluminum lactate solution

[0593] A 1 kg solution of 15 wt% aluminum lactate in deionized water (Millipore Q, conductivity <1.6 μS / cm) was prepared by adding 850 g deionized water to 150 g aluminum lactate.

[0594] Surface cross-linking solution (SXL solution) (see Table 2) :

[0595] The Denacol concentrations used were prepared according to Table 2 and each was contained in a snap-top jar of approximately 50 ml volume.

[0596] To prepare solutions, remove the Denacol bottle or container (approximately 1 L) from the refrigerator and allow to thermally equilibrate for approximately 30 minutes before preparing solutions.

[0597] The solution was prepared as follows:

[0598] For a given example, different corresponding concentrations of Denacol EX810, DN-810ex Nagase Co. Ltd) were prepared by adding the amounts shown in Table 2 to snap-top plastic jars, which were then filled to 20 g with 1,2-propylene glycol.

[0599] Table 2 :

[0600]

[0601] Implementation of the SXL process :

[0602] Each of the dry base polymer particles BP A1 to BP A11 and BP C1 to BP C7 was weighed to 20-30 g and recorded to ±0.1 g and placed in a separate 250 ml glass beaker so that the filling height was ≤25% of the total height. The exact amounts are shown in Table 4.

[0603] The matrix polymer particles were mixed in a beaker using a PTFE stirrer at 600 + / - 50 rpm. The stirrer only touched the bottom of the beaker. The matrix polymer particles needed to be stirred until a good fluidization of the bed was achieved.

[0604] The required amount of solution was added using an Eppendorf pipette, proceeding stepwise as described below, and the actual amounts are given in Table 4. (Eppendorf pipette speed setting: medium)

[0605] Step 1 :

[0606] Add a certain amount of aluminum lactate solution to the center of the stirring beaker. Then, increase the stirring speed to 2000 + / - 50 rpm. Stir for about 15 seconds and continue with step 2. If necessary, cover the beaker with aluminum foil, for example, to prevent the material from popping out.

[0607] Step 2 :

[0608] Add a certain amount of SXL solution to the center of the stirring tube. Stir for about 15 seconds and continue with step 3.

[0609] Step 3 :

[0610] A certain amount of deionized water (3% by weight based on sample weight) is added to the center of the stirring. Stir for about 15 seconds. After the agitator stops, the material is transferred to a heat-resistant wide-mouthed glass bottle (such as a crystallizing dish) and evenly distributed. Only loose material is taken out, and the wall of the beaker leaves a strongly stacked material. Remove the loose material by gently tapping on the beaker wall or using a spatula. Avoid scratching. Cover the wide-mouthed glass bottle with aluminum foil and store it in a fume hood at room temperature for about 16h to 18h (recommended overnight), then heat the material in an oven at the required temperature and time (for example, except for the 3h heating time, the surface cross-linked Denacol is warmed up to 120°C from room temperature for 20min).

[0611] After a heating time of 2 h 20 min, the aluminum foil was half-opened and kept like this for the remaining 1 h of heating in order to drive the moisture below 1 %w.

[0612] After the heating time, the container was removed from the oven and the material was placed in a fume hood to cool to room temperature for approximately 15 min.

[0613] The final polymer was tested for moisture and the results are shown in Table 3.

[0614] Table 3 :

[0615] Example Moisture, weight % A1 0.4 A2 0.4 A3 0.4 A4 0.4 A5 0.4 A6 0.4 A7 0.4 A8 0.5 A9 0.4 A10 0.4 A11 0.5 C1 0.2 C2 0.8 C3 0.7 C4 0.6 C5 0.6 C6 0.6 C7 0.5

[0616] Table 4

[0617]

[0618] The amounts of Denacol EX-810 and aluminum lactate added were selected so that the resulting Examples and Comparative Examples exhibited an SFC greater than 1 unit and preferably a CRC greater than 18 g / g. (See Table 5)

[0619] Table 5: Properties of Examples A1 to A11 and Comparative Examples C1 to C7

[0620]

[0621] 1) The value of the matrix polymer particles

[0622] 2) The value of SAP particles after surface cross-linking

[0623] As shown in the data in Table 5, the SAP particles of Examples A1 to A11 all exhibited good performance in terms of capacity (CRC), EFFC, and permeability (UPM). For example, by comparing the extractable amounts of Examples A1, A2, A10, and A11 with Comparative Examples C3 and C5 (all having an addition level of 5 wt% s-PAA polymer), it can be seen that the extractable amounts were significantly lower despite having a comparable addition level of s-PAA polymer.

[0624] This is also reflected by the ratio of (extractables minus s-PAA polymer addition level) to the CRC of the base polymer. This ratio reflects the impact of the s-PAA polymer addition level on the total amount of extractables and is related to capacity (since an increase in capacity generally leads to an increase in the amount of extractables in the SAP particles). The extractable amounts of Comparative Examples C3 and C5 are substantially higher than those of Examples A1 and A2 by approximately 5% by weight, indicating that the s-PAA polymers of the Comparative Examples have leaked out of the SAP particles to a very high degree. In contrast, the s-PAA polymers of the inventive examples did not significantly leak out of the SAP particles, indicating that they were covalently bonded to the network due to their carbon-carbon double bonds. As particularly evident in Example A1, which has an average molecular weight as low as 134 kDa, even relatively low-average molecular weight s-PAA polymers do not significantly contribute to the amount of extractables by applying s-PAA polymers with carbon-carbon double bonds. Typically, molecules with low average molecular weight have a higher potential for leakage (thus contributing to the amount of extractables) because they can more easily escape from the swollen polymer network. However, due to their ability to polymerize into the polymer network of SAP particles due to their carbon-carbon double bonds, even such relatively small s-PAA polymers can be readily used to prepare SAP particles.

[0625] Furthermore, since s-PAA polymers with carbon-carbon double bonds can be used to crosslink polymer chains during polymerization, the amount of additional crosslinking agents typically used to prepare SAP materials can be reduced or even eliminated. This is reflected in the results of Examples A5 and A7 (reduced amounts of additional crosslinking agents to a 0.075 molar ratio) and A8 and A9 (no additional crosslinking agents), all of which exhibit good properties.

[0626] The inventive examples with the lowest mole percentage of carbon-carbon double bonds, namely A10 and A11, have relatively higher amounts of extractables and higher ratios of (extractables minus the s-PAA polymer addition level) to the CRC of the base polymer compared to the other inventive examples. However, these examples still have significantly better ratios of (extractables minus the s-PAA polymer addition level) to the CRC of the base polymer compared to the comparative examples.

[0627] The dimensions and values ​​disclosed herein are not to be construed as being strictly limited to the exact numerical values ​​recited. Instead, unless otherwise indicated, 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." Furthermore, every numerical range given throughout this specification includes every narrower numerical range falling within such broader numerical range.

[0628] Unless expressly excluded or otherwise limited, each document cited herein, including any cross-referenced or related patent or application, is hereby incorporated by reference in its entirety. The citation of any document is not an admission that it is prior art with respect to any of the present inventions disclosed or claimed herein, or that it, by itself or in combination with any one or more of the references, proposes, 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.

[0629] Although specific embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various other changes and modifications may be made without departing from the spirit and scope of the present invention. It is therefore intended that all such changes and modifications within the scope of the present invention be encompassed in the appended claims.

Claims

1. A method for preparing a superabsorbent polymer material, comprising the steps of: a) providing an aqueous solution of a polymerizable acrylic monomer and / or a polymerizable acrylic oligomer; b) providing one or more initiators; c) providing a soluble polyacrylic acid polymer, wherein the soluble polyacrylic acid polymer has at least 0.03 mole percent of carbon-carbon double bonds as determined using an NMR alkylene content method; d) mixing the aqueous solutions of monomers, oligomers and initiators provided in steps a) to c) with the soluble polyacrylic acid polymer; and e) polymerizing the mixture obtained in step d) to obtain a superabsorbent polymer, The soluble polyacrylic acid polymer is a polyacrylic acid polymer that is soluble in aqueous solution and is not cross-linked above the gel point, which is the abrupt change in viscosity of a solution containing the polymer. 2 . The method of claim 1 , further comprising neutralizing at least some of the polymerizable acrylic monomer and / or the polymerizable acrylic oligomer in step a).

3. The method according to claim 1, further comprising: f) providing one or more ethylenically unsaturated comonomers, wherein In said step d), the aqueous solutions of monomers, oligomers, comonomers and initiators provided in steps a) to c) and f) are mixed with a soluble polyacrylic acid polymer.

4. The method of claim 3, further comprising neutralizing at least some of the ethylenically unsaturated comonomer of step b).

5. The method according to claim 3, further comprising: g) providing one or more cross-linking agents, wherein In said step d), the aqueous solutions of the monomers, oligomers, comonomers, crosslinking agents and initiators provided in steps a) to c) and steps f) and g) are mixed with the soluble polyacrylic acid polymer.

6. The method according to claim 1, further comprising: g) providing one or more cross-linking agents, wherein In said step d), the aqueous solutions of the monomers, oligomers, crosslinking agents and initiators provided in steps a) to c) and g) are mixed with the soluble polyacrylic acid polymer.

7. The method according to claim 1, wherein In step c), the soluble polyacrylic acid polymer has a mole percentage of carbon-carbon double bonds of at least 0.

05.

8. The method according to claim 1, wherein In step c), the soluble polyacrylic acid polymer has a mole percentage of carbon-carbon double bonds of at least 0.

08.

9. The method according to claim 1, wherein In step c), the soluble polyacrylic acid polymer has a mole percentage of carbon-carbon double bonds of at least 0.

1.

10. The method of claim 5, wherein the soluble polyacrylic acid polymer provided in step c) is provided in an amount of at least 3 wt%, based on the total weight of the soluble polyacrylic acid polymer provided in step c) and the monomers, oligomers, comonomers, crosslinking agents and initiators provided in steps a), b), f) and g).

11. The method according to claim 10, the method according to claim 3, wherein the soluble polyacrylic acid polymer provided in step c) is provided in a weight percentage of at least 5 weight %, based on the total weight of the soluble polyacrylic acid polymer provided in step c) and the monomers, oligomers, comonomers, crosslinking agents and initiators provided in steps a), b), f) and g).

12. The method according to any one of claims 1 to 11, wherein the soluble polyacrylic acid polymer provided in step c) is provided in a weight percentage of up to 60.0 wt%, based on the total weight of the soluble polyacrylic acid polymer provided in step c) and the monomers, oligomers, comonomers, crosslinkers and initiators provided in steps a), b), f) and g).

13. The method according to claim 12, wherein the soluble polyacrylic acid polymer provided in step c) is provided in a weight percentage of up to 50.0 wt%, based on the total weight of the soluble polyacrylic acid polymer provided in step c) and the monomers, oligomers, comonomers, crosslinking agents and initiators provided in steps a), b), f) and g).

14. The method according to any one of claims 1 to 11, wherein the method further comprises a step h) of drying the superabsorbent polymer material.

15. The method according to any one of claims 1 to 11, further comprising the step i) of comminuting the superabsorbent polymer material to obtain superabsorbent polymer particles.

16. The method according to claim 15, further comprising the step of surface cross-linking the superabsorbent polymer particles.

17. The method according to any one of claims 1 to 11, wherein the soluble polyacrylic acid polymer is obtained from pre-existing recycled post-consumer superabsorbent polymer material, and / or from pre-existing recycled post-industrial superabsorbent polymer material.

18. The method according to claim 17, wherein the method further comprises a1) obtaining the soluble polyacrylic acid polymer from the pre-existing recycled post-consumer superabsorbent polymer material or from a 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 performed before step f).

19. The method of claim 18, wherein the chemical degradation is performed using an oxidizing water-soluble salt comprising at least one cation and at least one anion.

20. The method of claim 19, wherein the at least one anion is selected from the group consisting of peroxydisulfate, peroxymonosulfate, peroxydicarbonate, peroxydiphosphate, peroxydiborate, and mixtures and combinations thereof.

21. The method of claim 18, wherein the chemical degradation is mediated by a redox couple, wherein the redox couple is 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.

22. The method of any one of claims 1-11, wherein the soluble polyacrylic acid polymer has a weight average molecular weight Mw of 500 kDa to 3 MDa.

23. The method of claim 22, wherein the soluble polyacrylic acid polymer has a weight average molecular weight (Mw) of 100 kDa to 1 MDa.

24. The process according to any one of claims 1 to 11, wherein the superabsorbent polymer material obtained by the process has an amount of extractables of less than 15.0 wt.-%, based on the total weight of the superabsorbent polymer material, and a ratio of the difference between the amount of extractables in wt.-% and the amount of polyacrylic acid polymer added that is soluble in aqueous solution in wt.-% to the capacity in g / g of less than 0.15, wherein The amount of extractables is measured according to EDANA test method NWSP 270.0.R2 (15) and the capacity is determined according to the Centrifuge Retention Capacity CRC test method described in EDANA NWSP 241.0.R2 (15), except that the CRC measurement starts at a lower limit of 24.2 g / g, unlike EDANA NWSP 241.0.R2 (15).

25. The process according to any one of claims 1 to 11, wherein the superabsorbent polymer material obtained by said process has a capacity measured as Centrifuge Retention Capacity (CRC) of at least 20 g / g, said capacity being determined according to the Centrifuge Retention Capacity (CRC) test method described in EDANA NWSP 241.0.R2 (15), except that according to EDANA NWSP 241.0.R2 (15), the CRC measurement starts at a lower limit of 24.2 g / g.

26. Superabsorbent polymer material obtainable by the process according to any one of claims 1 to 25.

27. The superabsorbent polymer material according to claim 26, wherein after said polymerization said soluble polyacrylic acid polymer acts as the only internal cross-linking agent in the network of said superabsorbent polymer material.

28. The superabsorbent polymer material according to claim 26 or 27, wherein the superabsorbent polymer material is in the form of superabsorbent polymer particles.

29. The superabsorbent polymer material according to claim 26 or 27, wherein the superabsorbent polymer particles are surface cross-linked.

30. The superabsorbent polymer material according to claim 26 or 27, wherein the superabsorbent polymer material has an amount of extractables of less than 15.0 wt.-%, based on the total weight of the superabsorbent polymer material.

31. An absorbent article comprising the superabsorbent polymer material according to any one of claims 26 to 30.

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