Crosslinked superabsorbent polyaspartic acid or a salt thereof

Abstract

Provided herein is a crosslinked polyaspartic acid or a salt thereof, intermediates thereto, processes of manufacturing them, and articles of manufacture including crosslinked polyaspartic acid or a salt thereof.

Description

[0001]Atty. Dkt. No.: LYGOS-0066-01-WO CROSSLINKED SUPERABSORBENT POLYASPARTIC ACID OR A SALT THEREOF PRIORITY CLAIM This application claims priority to US Provisional Patent Application Nos.63 / 597,901 and 63 / 597,914 filed November 10, 2023; and 63 / 658,056 filed June 10, 2024, each of which is incorporated herein in its entirety by reference. FIELD Provided herein is a crosslinked polyaspartic acid or a salt thereof, preferably superabsorbent polyaspartic acid or a salt thereof, intermediates thereto, processes of preparing them, and articles of manufacture including such crosslinked polyaspartic acid or a salt thereof. BACKGROUND Polyanionic polymers such as polyacrylates persist. They are not amenable to hydrolysis. There is a need for polyanionic polymers, preferably superabsorbent polymers useful for example in absorbing large volumes of aqueous solutions, which are degradable, sustainable, and / or biobased. SUMMARY This invention arises in part out of the surprising observation that acidic polysuccinimide (PSI), as disclosed herein in detail, can be crosslinked, upon in situ neutralization, to provide a robust, commercially meaningful, and hitherto unknown process to prepare high performing super absorbent polymers comprising crosslinked polyaspartates polymers. Crosslinked polyaspartate (a polyaspartic acid salt) superabsorbents have a polymer backbone which, as opposed to polyacrylate, the constituent of Arctic Gel brand superabsorbents, is degradable. As used herein, degradable includes without limitation biodegradable. Crosslinked polyaspartate superabsorbents function substantially similar to or better than polyacrylate, while offering functional groups such as amine and carbonyl to further modify and fine-tune the function. Taken together with the degradability and / or the bio-based nature of the crosslinked polyaspartate superabsorbents, they offer distinct environmental advantages, while performing as a superabsorbent as demonstrated in the Examples herein. 1 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO In one aspect, provided herein is a crosslinked polyaspartic acid or a salt thereof (a crosslinked polyaspartate salt) comprising a polyaspartic acid or a salt thereof (a polyaspartate salt) and a crosslinker. In one embodiment, the crosslinked polyaspartic acid or a salt thereof has a particle size of up to about 1,000 micrometer, preferably up to about 850 micrometer, more preferably from about 150 micrometer to about 850 micrometer. In another embodiment, the crosslinked polyaspartic acid or a salt thereof has a particle size of about 1 – about 50 micrometer, preferably once saturated with a fluid the size is about 30 – about 40 micrometer, more preferably from about 36 micrometer. In another embodiment, the crosslinked polyaspartic acid or a salt thereof (a crosslinked polyaspartate salt) comprising a polyaspartic acid or a salt thereof (a polyaspartate salt) and a crosslinker, which has a particle size of about 30 micrometer to about 400 micrometer, preferably up to about 100 micrometer once swollen in fluid, more preferably up to about 50 micrometer. The crosslinked polyaspartate is formed by crosslinking a PSI with molecular weight ranges as given. The PSI can optionally be hydrolyzed to any degree prior to crosslinking depending on chemistry. In one embodiment, the crosslinked polyaspartic acid or a salt thereof is prepared from PSI having a weight average molecular weight (Mw) of at least about30,000, or at least about 70,000, or at least about 80,000 to about 200,000, preferably about 70,000 to about 85,000. In some embodiments, the Mwis less than 30,000. In another embodiment, the Mwis 4,000, or more. In another embodiment, the crosslinked polyaspartic acid or a salt thereof is prepared from PSI having a number average molecular weight (Mn) of about 15,000 to about 25,000, about 15,000 to about 20,000, or preferably about 17,000. In one embodiment, the crosslinked polyaspartic acid or a salt thereof is prepared from PSI having a weight average molecular weight (Mw) of at least about 50,000, or at least about 70,000 to about 200,000, preferably about 50,000 to about 85,000. In another embodiment, the crosslinked polyaspartic acid or a salt thereof is prepared from PSI having a number average molecular weight (Mn) of about 15,000 to about 90,000, about 15,000 to about 40,000, or preferably about 20,000 to 30,000. In another aspect, provided herein is a crosslinked polysuccinimide (PSI) comprising a polysuccinimide and a crosslinker. In one embodiment, crosslinked polysuccinimide has a particle size of up to about 1,000 micrometer, preferably up to about 850 micrometer, more 2 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO preferably from about 150 micrometer to about 850 micrometer. In another embodiment, crosslinked PSI has a particle size of 1-50 micrometer. In one embodiment, the crosslinked polysuccinimide has a weight average molecular weight (Mw) of at least about 30,000, or at least about 70,000, or at least about 80,000 to about 200,000, preferably about 70,000 to about 85,000. In another embodiment, the crosslinked polysuccinimide has a number average molecular weight (Mn) of about 15,000 to about 25,000, about 15,000 to about 20,000, or preferably about 17,000. In one embodiment, the crosslinked polysuccinimide has a weight average molecular weight (Mw) of at least about 30,000, or at least about 50,000, or at least about 70,000 to about 200,000, preferably about 50,000 to about 85,000. In another embodiment, the crosslinked polysuccinimide has a number average molecular weight (Mn) of about 15,000 to about 90,000, about 15,000 to about 40,000, or preferably about 20,000 to 30,000. In another aspect, provided herein is an aqueous composition comprising the crosslinked polyaspartic acid or a salt thereof provided herein. In one embodiment, the aqueous composition comprises a conductance of less than or equal to 1.5 mS. In one embodiment, the aqueous composition comprises a conductance of less than or equal to 1.25 mS. In one embodiment the crosslinked polyaspartate or the salt thereof has a free swell capacity (FSC) of at least about 20 g / g, or at least about 25 g / g, or about 50 g / g. In some embodiments, the FSC is less than 20 g / g. In some embodiments, the FSC is 5 g / g. In one embodiment, the crosslinked polyaspartate or the salt thereof has a centrifuge retention capacity (CRC) of at least about 5 g / g, or at least about 20 g / g, to about 40 g / g. In one embodiment, the CRC is less than 5 g / g. In one embodiment, the CRC is 1 g / g. In one embodiment the crosslinked polyaspartate or the salt thereof has a time in seconds for the superabsorbent to absorb 20 cubic centimeters of 0.9% saline (T-20) of about 40 – about 75, preferably about 45 – about 70, or about 45. In one embodiment, the T-20 is less than 40. In another embodiment, the T-20 is about 10. In one embodiment the crosslinked polyaspartate or the salt thereof has an FSC of at least about 20 g / g, or at least about 25 g / g, to about 50 g / g. In one embodiment the crosslinked 3 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO polyaspartate or the salt thereof has a CRC of at least about 15 g / g, or at least about 20 g / g, to about 40 g / g. In one embodiment the crosslinked polyaspartate or the salt thereof has a time in seconds for the superabsorbent to absorb 20 cubic centimeters of 0.9% saline (T-20) of about 100 to about 400, or preferably about 130 to about 210. In one embodiment the crosslinked polyaspartate or the salt thereof has a maximum free swell saline permeability of at least about 1.0 g / s, or at least 2.0 g / s to about 4.0 g / s. In another embodiment, less than: about 25%, about 5%, about 4%, about 3%, about 2%, preferably, less than about 1%, or less than about 0.5%, by mole of the polyaspartic acid or the salt thereof is a linear as opposed to a branched polymer. or is a branched as opposed to a linear polymer. As used herein, linear and branched polymers account for 100 mole% of the polymer. In another embodiment, the crosslinked polyaspartic acid or a salt thereof or the aqueous composition comprises a crosslinker which is: -HN-L-NH-, -HN(CH2)2X(CH2)2X(CH2)2NH-, -O-L-O-, or RNHCON(-)L(-)CONHR moiety, which is bound at each end to a carbonyl group of a polyaspartic acid or a salt thereof, wherein each X independently is O, S, SO or SO2; L is a C2-C12, preferably a C4-C8, alkylene or heteroalkylene, and R is a hydrocarbyl group; or comprises a crosslinker which is: -CH2CH(OH)-L-CH(OH)CH2- moiety, which is bound at each end to a -CO2- group of a polyaspartic acid or a salt thereof. In another embodiment, the crosslinker is: 4 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO -HN(CH2)2X(CH2)2X(CH2)2NH- or an -O-L-O-. In another embodiment, the crosslinker is: -CH2CH(OH)-L-CH(OH)CH2-. In another embodiment, the crosslinker is: -HN(CH2)2X(CH2)2X(CH2)2NH- or an -O-L-O-. In another embodiment, the crosslinker is: -CH2CH(OH)-L-CH(OH)CH2-. In another embodiment, the crosslinker is: -HN(CH2)2X(CH2)2X(CH2)2NH-. In another embodiment, the crosslinker is: -HN(CH2)2O(CH2)2O(CH2)2NH-. In another embodiment, the crosslinker is -HN-L-NH-. In one embodiment, L is alkylene, such as C2-C12, preferably a C4-C8, alkylene. In one embodiment, L is -(CH2)6-. In another embodiment, L is heterolkylene, such as C2-C12, preferably a C4-C8, heteroalkylene. In another embodiment, X is O. In another embodiment, X is S. In another embodiment, X is SO. In another embodiment, X is SO2. In another embodiment, the crosslinker is: -O-L-O-. In another embodiment, the crosslinker is: -CH2CH(OH)-L-CH(OH)CH2-. In another embodiment, L is alkylene. In another embodiment, L is heteroalkylene. In another embodiment, provided herein is the crosslinked polyaspartic acid or a salt thereof, or the aqueous composition, wherein the crosslinker is about 0.1% - about 15% by weight of rest of the crosslinked polyaspartic acid or a salt thereof. In another embodiment, provided herein is the crosslinked polyaspartic acid or a salt thereof, or the aqueous composition, wherein the crosslinker is about 0.1% - about 15% by weigh of the PSI reacted to prepare the crosslinked polyaspartic acid or a salt thereof. In another embodiment, the crosslinker is about 0.1% - about 10%, by weight of rest of the crosslinked polyaspartic acid or a salt thereof. 5 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO In another embodiment, the crosslinker is about 0.5% - about 8% by weight of rest of the crosslinked polyaspartic acid or a salt thereof. In another embodiment, the crosslinker is about 1%- about 6%, of rest of the crosslinked polyaspartic acid or a salt thereof. In another embodiment, the crosslinker is about 0.1% - about 10%, by weight of the PSI. In another embodiment, the crosslinker is about 0.5% - about 8% by weight of the PSI. In another embodiment, the crosslinker is about 1%- about 6%, of rest of the PSI. In certain instances, a polyaspartate or a polyaspartic acid is crosslinked with a crosslinker compound to provide a crosslinked polyaspartate polymer such as a SAP. Suitable crosslinker compounds useful thereby include epoxy, carbodiimide, aziridine, isocyanates, melamines, and the likes. Without being bound by theory, these crosslinker compounds have electrophilic functional groups. Polyaspartates are produced by hydrolyzing polysuccinimide. Various alkali compounds such as NH4OH, NaOH and the likes may be utilized for the hydrolysis. Polysuccinimides are prepared by thermal polymerization of aspartic acid. The polymerization of aspartic acid may be performed in presence of an acid. Suitable acids include phosphoric acids, sulfonic acids and the likes. Other suitable catalysts or reactants include without limitation phosphites. Non-limiting examples of phosphites include triphenyl phosphite. The thermal polymerization of aspartic acid may also be performed without an acid. In certain instances, a polysuccinimide is crosslinked with a crosslinker compound and hydrolyzed to provide a crosslinked polymer such as a SAP. Suitable crosslinker compounds useful thereby include nucleophilic crosslinkers, such as without limitation amine, hydroxy, and thiol containing crosslinker compounds. Polysuccinimides, which may be crosslinked and hydrolyzed to provide a SAP, are in certain preferred embodiments, prepared by thermal polymerization of aspartic acid in presence of an acid. In another embodiment, the crosslinker is about 3-4% by weight of rest of the crosslinked polyaspartic acid or a salt thereof. In another embodiment, the crosslinked polysuccinimide comprises a crosslinker which is a: 6 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO -HN-L-NH-, -HN(CH2)2-X-(CH2)2-X-(CH2)2NH-, or an -O-L-O- moiety, which is bound at each end to a carbonyl group of a polysuccinimide, wherein each X independently is O, S, SO or SO2and L is a C2-C12, preferably a C4-C8, alkylene or heteroalkylene,. In addition to ditopic or difunctional crosslinkers, in some embodiments, tritopic or trifunctional crosslinkers comprising -NH-, -O-, or -CH2CH(OH)- end groups are also contemplated. In some embodiments, the tritopic linkers have a formula: (L1)(NH-)3, where L1is N(-L-)3or CR1(-L-)3, where each L independently is defined as herein, and R1is hydrogen, hydroxy, or optionally substituted C1-C6alkyl, preferably, C1-C3alkyl. Suitable substituents include without limitation, hydroxy, amino, carboxamido, and the likes. In another embodiment, provided herein is the crosslinked polysuccinimide, wherein the crosslinker is about 0.1% - about 15% by weight of rest of the crosslinked polysuccinimide. In another embodiment, the crosslinker is about 0.1% - about 10%, by weight of rest of the crosslinked polysuccinimide. In another embodiment, the crosslinker is about 0.5% - about 8% by weight of rest of the crosslinked polysuccinimide. In another embodiment, the crosslinker is about 1% - about 6% by weight of rest of the crosslinked polysuccinimide. In another embodiment, the crosslinker is about 3-4% by weight of rest of the crosslinked polysuccinimide. In another aspect, provided herein is a process comprising: reacting a crosslinked polysuccinimide provided herein with alkali, adjusting the pH of the reaction to about pH 7, filtering the pH adjusted mixture, washing the residue with water and isopropanol, and drying the residue, to provide a crosslinked polyaspartic acid or a salt thereof. In one embodiment, the filtering is performed comprising a decanter centrifuge, a filter press, an agitated filter dryer, or a rotary vacuum and pressure drum filter. In one embodiment, the drying is performed comprising a drum dryer, a belt dryer, a paddle dryer, an agitated filter dryer, a static oven, a convection oven or a fluidized bed dryer. In one embodiment, the crosslinked polysuccinimide is produced comprising reacting a polysuccinimide, with a crosslinker compound of formula: 7 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO H2N-L-NH2, H2N(CH2)2-X-(CH2)2-X-(CH2)2NH2or a salt thereof; an HO-L-OH; or epoxy-L-epoxy wherein each X independently is O, S, SO or SO2and L is a C2-C12, preferably a C4-C8, alkylene or heteroalkylene, to provide the crosslinked polysuccinimide. In another embodiment, a crosslinker compound of formula carbodiimide-L-carbodiimide is reacted for crosslinking, where L is defined as above and carbodiimide refers to R-N=C=N- moiety where R is a hydrocarbyl group. In some embodiments, a heteroalkylene L moiety includes an -N=C=N- moiety. In some embodiments, R is C1-C8alkyl or cycloalkyl, preferably C1-C3alkyl. The hydrocarbyl group is optionally substituted with 1-3 amino, C1-C8alkylamino, or C1-C8dialkylamino groups. A schematic, illustrative, and nonlimiting representation of a carbodiimide crosslinker compound, employing a tritopic or trifunctional crosslinker compound, crosslinking a carboxyl group bearing polymer such as polyaspartate, referred to here as a “resin,” is shown below: in a polar the solvent is water. In one embodiment, the reaction of the polysuccinimide with a crosslinker compound is performed in the presence of a base. In some embodiments, the base includes alkali, ammonium hydroxide, or a mixture thereof. In one embodiment, the reaction of the polysuccinimide with a crosslinker compound is performed in the absence of additional base. 8 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO In one embodiment, the reaction of the polysuccinimide with a photoinitiated crosslinker compound is performed. The product of such a reaction can be crosslinked under light, e.g., by photoinitiation. The crosslinked or the PSI before crosslinking can be hydrolyzed to provide a polyaspartic acid or a salt thereof. Certain methods of functionalizing polysuccinimides with light sensitive crosslinkers is described in Grave et al., “Development of photo-crosslinked poly(aspartic acid) fiber networks via electrospinning,” Next Materials, Volume 3, April 2024, 100172, (incorporated herein in its entirety by reference) and can be adapted by a skilled artisan based on the disclosure herein. In one embodiment, the polysuccinimide reacted has less than: about 5%, about 4%, about 3%, about 2%, preferably, less than about 1%, or less than about 0.5%, by moles branched as opposed to linear polymer. In addition to ditopic crosslinker compounds, in some embodiments, tritopic crosslinker compounds comprising -NH2, -OH, or epoxy end groups are also contemplated. In some embodiments, non-limiting examples of tritopic crosslinker compounds include In some embodiments, the tritopic linkers have a formula: (L1)(NH2)3, (L1)(OH)3,or (L1)(epoxy)3, where L1is as defined herein. In some embodiments, the crosslinker is a polymeric crosslinkers. Non- limiting examples of polymeric crosslinkers include polyamines. Examples of polyamines include poly lysine, chitosan, poly vinyl amine, polyethyleneimine, and the likes. In another embodiment, H2N-L-NH2or a salt thereof is reacted. In one embodiment, L is -(CH2)6-. In another embodiment, H2N(CH2)2-X-(CH2)2-X-(CH2)2NH2 or a salt thereof is reacted. In one embodiment, each X is O. Within this embodiment, in certain embodiments, a base is reacted. In another embodiment, the base is ammonium hydroxide. In another embodiment, the base is an alkali. In another embodiment, the base is a metal hydroxide. In another embodiment, HO-L-OH is reacted. In another embodiment, epoxy-L-epoxy is reacted. In another embodiment, carbodiimide-L-carbodiimide is reacted, wherein carbodiimide is defined as above. In another embodiment, the crosslinker compound is reacted at about 0.1% - about 15%, by weight of the polysuccinimide. 9 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO In another embodiment, the crosslinker compound is reacted at about 0.1% - about 10%, by weight of the polysuccinimide. In another embodiment, the crosslinker compound is reacted at about 0.5% - about 8%, by weight of the polysuccinimide. In another embodiment, the crosslinker compound is reacted at about 1% - about 6%, by weight of the polysuccinimide. In another embodiment, the crosslinker compound is reacted at about 3-4% by weight of the polysuccinimide. In another embodiment, the crosslinker compound is reacted at about 0.1% - about 15%, by weight of the polyaspartate. In another embodiment, the crosslinker compound is reacted at about 0.1% - about 10%, by weight of the polyaspartate. In another embodiment, the crosslinker compound is reacted at about 0.5% - about 8%, by weight of the polyaspartate. In another embodiment, the crosslinker compound is reacted at about 1% - about 6%, by weight of the polyaspartate. In another embodiment, the crosslinker compound is reacted at about 3-4% by weight of the polyaspartate. In another embodiment, the crosslinker compound is reacted at about 3-4% by weight of a polyaspartate. In another embodiment, the polysuccinimide reacted has a weight average molecular weight (Mw) of at least about 30,000, or at least about 70,000, or at least about 80,000 to about 200,000, preferably about 70,000 to about 85,000. In another embodiment, the polysuccinimide reacted has a weight average molecular weight (Mw) of at about 50,000. In another embodiment, the polysuccinimide reacted has a number average molecular weight (Mn) of about 15,000 to about 20,000, or preferably about 17,000. In another embodiment, the crosslinked polyaspartic acid or a salt thereof is surface crosslinked. 10 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO In another embodiment, provided herein is a process comprising: reacting a crosslinked polysuccinimide provided herein with alkali or another base, adjusting the pH of the reaction to about pH 1, filtering the pH adjusted mixture, washing the residue with water and isopropanol, further adjusting the pH to 7, and drying the residue, to provide a crosslinked polyaspartic acid or a salt thereof. Without being bound by theory, reducing the pH to about 1 reduces the free swell capacity of swollen hydrogels. In one embodiment, the alkali is NaOH. In another embodiment, the alkali is KOH. In one embodiment, the alkali is NH4OH. A mixture of alkalis is also reacted in some embodiments. Suitable other bases include without limitation carbonates and bicarbonates. In another aspect, provided herein is a crosslinked polyaspartic acid or a salt thereof provided by the process provided herein. In another aspect, provided herein is an article of manufacture comprising the crosslinked polyaspartic acid or a salt thereof provided herein. In another aspect, provided herein is an article of manufacture comprising the aqueous composition provided herein. In one embodiment, the article is an absorbent hygiene product. In one embodiment, the article is a water blocking barrier. In one embodiment, the article is a fire retardant. In one embodiment, the article is or a rheology modifier. In one embodiment, the article is a medical device. In one embodiment, the article of manufacture is a pad, such as a diaper or a feminine hygiene product such as a sanitary napkin. In one embodiment, the article of manufacture is a diaper. In one embodiment, the article of manufacture is a baby diaper. In one embodiment, the article of manufacture is an incontinence diaper. In one embodiment, the article of manufacture is an incontinence pad which is an insert. In one embodiment, the article of manufacture is a feminine hygiene product. In one embodiment, the article of manufacture is a gel pack. In one embodiment, the article of manufacture comprises about 0.4 g to about 30 g of the SAP provided herein. In one embodiment, the article of manufacture comprises about 0.4 g to about 4 to about 30 g of the SAP provided herein. In one embodiment, the article of manufacture comprises about 8 g to about 14 g of the SAP provided herein. In one embodiment, the article of manufacture comprises about 10 g to about 12 g of the SAP provided herein. For larger incontinence pads use of even larger amounts of SAPs is 11 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO contemplated. In one embodiment, the article of manufacture comprises about 0.4 g to about 4.0 g of the SAP provided herein. In one embodiment, the article of manufacture comprises about 0.5 g of the SAP provided herein. In one embodiment, the article of manufacture comprises about 1.5 g of the SAP provided herein. In one embodiment, the article of manufacture comprises about 3.0 g of the SAP provided herein. In one embodiment, the article of manufacture, such as a pad, such as a diaper or a sanitary napkin comprises about 5% - about 50% (i.e., [wt of SAP / wt of (SAP+fluff)]x100)) of the SAP provided herein. In one embodiment, the article of manufacture, such as a pad, such as a diaper or a sanitary napkin comprises about 5% - about 100%. E.g., and without limitation, preformed cores comprise about 100% of the SAP. In one embodiment, the article of manufacture, such as a pad, such as a diaper or a sanitary napkin comprises about 9% - about 40% of the SAP provided herein. In one embodiment, the article of manufacture, such as a pad, such as a diaper or a sanitary napkin comprises about 5%, about 9%, about 15%, about 20%, about 25%, about 30%, or about 40% of the SAP provided herein. A SAP is used in, but not limited to, absorbent articles for infant care, period care, adult incontinence, lactation pads, pet pads, and the like. A SAP is incorporated into an article of manufacture in various ways. These include, without limitation, standard fluff and SAP mixtures made on a diaper machine; air laid, preformed roll goods that incorporate SAP, fluff, and, perhaps other fibers (different pulp, thermofusible fibers, and the like); inclusion of SAP into a nonwoven made from polypropylene or other fibers; printing of SAP onto a substrate; inclusion of SAP in pockets of varying sizes; SAP in foam format; SAP placed, such as layered on, a compressed core, the core comprising fibers, preferably hydrophilic fibers. In one embodiment, the crosslinked polyaspartic acid or a salt thereof provided herein are superabsorbent. In one embodiment, the crosslinked polymers and precursors thereof, such as polysuccinimides, provided herein, comprise biobased aspartic acid or aspartyl [(-NH- CH(CH2CO2H)CO-) or (-NH-CH(CO2H)CH2CO-)] moieties. In one embodiment, the superabsorbent polyaspartic acid or a salt thereof provided herein comprises biobased aspartic acid or aspartyl moieties. In one embodiment, the superabsorbent polymer is a polyaspartic acid sodium salt. 12 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO BRIEF DESCRIPTION OF FIGURES FIGURE 1A: Block flow diagram for catalyzed polymerization of L-aspartic to PSI.01 L- Aspartic acid; 02 Phosphoric acid (85%); 03 Water, acidic (waste); 04 Acidified Polysuccinimide (PSI) LY1; 05 Sodium bicarbonate, saturated solution; 06 Water, deionized or distilled; 07 Neutral PSI in water; 08 Wet neutral polysuccinimide (PSI); 09 Aqueous waste 10 Water, deionized or distilled; 11 Dry non-sized PSI; 12 Dry sized PSI. FIGURE 1B: Diagram of phosphoric acid catalyzed polymerization of L-aspartic acid to produce acidified linear polysuccinimide. FIGURE 1C: Diagram of neutralizing acidified PSI to produce dry PSI. FIGURE 1D: Diagram for producing crosslinked polyaspartate from acidic PSI without prior neutralization employing HMDA as an illustrative crosslinker. FIGURE 2: Block flow diagram for cross-linking PSI to produce a superabsorbent. 12 Polysuccinimide (PSI); 13 Crosslinker compound; 14 Ammonium hydroxide (28-30%); 15 Water, deionized or distilled; 16 Cross-linked PSI; 17 Water, deionized or distilled; 1850% sodium hydroxide; 19 Crude superabsorbent (SAP); 2060% sulfuric acid; 21 Neutral pH crude SAP; 22 Water, deionized or distilled; 23 Isopropyl alcohol (IPA); 24 Wet low salt SAP; 25 Spent water; 26 Spent IPA; 27 Water / IPA volatiles (waste); 28 Dry non-sized SAP; 29 Dry sized SAP FIGURE 3: Non-limiting illustration of a pads: a diaper and a sanitary napkin. FIGURE 4: Images depicting preparing a diaper including a SAP such as that provided herein. FIGURE 5: Bar graph showing crosslinked polyaspartate SAP containing pad rewet results. In this re-wet test 75mL of saline is applied to the flat configured diaper. After 10 mins a filter paper is placed on the test area and a weight is placed on the paper. The filter paper is left in contact with the test area for 2 minutes. After that time the filter paper is weighed to determine the amount of saline transferred to the filter paper. This is repeated a second (dose 2) and third time (dose 3). FIGURE 6: Images depicting preparing a feminine hygiene product such as a napkin or a period care including a SAP such as that provided herein. FIGURE 7: Image of blood absorption of a SAP provided herein. 13 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO FIGURE 8: Bar graph showing the beneficial effect of adding a SAP provided herein to a pad for saline rewet In this re-wet test 10mL of saline is applied to the flat configured period care product. After 10mins a filter paper is placed on the test area and a weight is placed on the paper. The filter paper is left in contact with the test area for 2 minutes. After that time the filter paper is weighed to determine the amount of water transferred to the filter paper. This is repeated a second time (dose 2). FIGURE 9: Bar graph showing the beneficial effect of adding a SAP provided herein to a pad for blood rewet In this re-wet test 10mL of defibrinated, sterile blood is applied to the flat configured period care product. After 10mins a filter paper is placed on the test area and a weight is placed on the paper. The filter paper is left in contact with the test area for 2 minutes. After that time the filter paper is weighed to determine the amount of blood transferred to the filter paper. This is repeated a second time (dose 2). FIGURE 10: Graphs of time course of saline absorbed over time (10A) and permeability test (10B) of crosslinked superabsorbent polymers provided herein as described in Example 5. DETAILED DESCRIPTION As used in the specification and claims, the singular form “a,” “an” and “the” include plural references unless the context clearly dictates otherwise. As used herein, the term “comprising” is intended to mean that the compounds, compositions and processes include the recited elements, but not exclude others. “Consisting essentially of" when used to define compounds, compositions and processes, shall mean excluding other elements of any essential significance to the combination. Thus, a composition consisting essentially of the elements as defined herein would not exclude trace contaminants, e.g., from the isolation and purification method. “Consisting of’ shall mean excluding more than trace elements of other ingredients. Embodiments defined by each of these transition terms are within the scope of this technology. 14 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO All numerical designations, e.g, pH, temperature, time, concentration, and molecular weight, including ranges, are approximations which are varied (+) or (-) by increments of 1, 5, or 10%, e.g., by using the prefix, “about.” It is to be understood, although not always explicitly stated that all numerical designations are preceded by the term “about.” It also is to be understood, although not always explicitly stated, that the reagents described herein are merely exemplary and that equivalents of such are known in the art. As used herein, the range, “about x to y” includes about x to about y. “Alkylene” refers to divalent saturated aliphatic hydrocarbyl groups having from 1 to 10 carbon atoms, preferably having from 1 to 6 and more preferably 1 to 3 carbon atoms that are either straight-chained- or branched. This term is exemplified by groups such as methylene (- CH2-), ethylene (-CH2CH2-), n-propylene (-CH2CH2CH2-), iso-propylene (-CH2CH(CH3)- or - CH(CH3)CH2-), butylene (-CH2CH2CH2CH2-), isobutylene (-CH2CH(CH3)CH2-), sec-butylene (- CH2CH2(CH3)CH), and the like. “Heteroalkylene” refers to an alkylene group wherein one or more carbons is replaced with -O-, -S-, SO2, a P containing moiety, or -NRQ- moieties where RQis H or C1-C6alkyl. A “salt” is derived from a variety of organic and inorganic counter ions well known in the art and include, when the compound contains an acidic functionality, by way of example only, sodium, potassium, calcium, magnesium, ammonium, and tetraalkylammonium; and when the molecule contains a basic functionality, salts of organic or inorganic acids, such as hydrochloride, hydrobromide, tartrate, mesylate, acetate, maleate, and oxalate. Salts include acid addition salts formed with inorganic acids or organic acids. Inorganic acids suitable for forming acid addition salts include, by way of example and not limitation, hydrohalide acids (e.g., hydrochloric acid, hydrobromic acid, hydroiodic acid, etc.), sulfuric acid, nitric acid, phosphoric acid, and the like. Salts include salts formed when an acidic proton present in the parent compound is either replaced by a metal ion (e.g., and without limitation an alkali metal ion, an alkaline earth metal ion, ) or by an ammonium ion (e.g., and without limitation an ammonium ion derived from ammonia, and an organic base, such as, ethanolamine, diethanolamine, triethanolamine, morpholine, piperidine, dimethylamine, diethylamine, and triethylamine). 15 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO Organic acids suitable for forming acid addition salts include, by way of example and not limitation, acetic acid, trifluoroacetic acid, propionic acid, hexanoic acid, cyclopentanepropionic acid, glycolic acid, oxalic acid, pyruvic acid, lactic acid, malonic acid, succinic acid, malic acid, maleic acid, fumaric acid, tartaric acid, citric acid, palmitic acid, benzoic acid, 3-(4- hydroxybenzoyl) benzoic acid, cinnamic acid, mandelic acid, alkylsulfonic acids (e.g., methanesulfonic acid, ethanesulfonic acid, 1,2- ethane-disulfonic acid, 2-hydroxyethanesulfonic acid, etc.), arylsulfonic acids (e.g., benzenesulfonic acid, 4-chlorobenzenesulfonic acid, 2- naphthalenesulfonic acid, 4- toluenesulfonic acid, camphorsulfonic acid, etc.), glutamic acid, hydroxynaphthoic- acid, salicylic acid, stearic acid, muconic acid, and the like. As used herein, renewable, bio-based, or a grammatical equivalent thereof refers to a compound containing carbon that has an isotopic distribution that is within measurement error of the isotopic distribution contained in terrestrial plant matter, indicating that the carbon was sourced from a renewable, sustainable source rather than petroleum. In some embodiments, renewable, non-petrochemical based component-containing compositions provided herein contain a14C amount substantially higher than zero, such as about 1 parts per trillion or more. As used herein, terrestrial plant matter or non-petrochemical based components include carbon atoms that have a non-petrochemical based origin. Such non-petrochemical based (or bio-based or renewable) components have a14C amount substantially higher than zero, such as about 1 parts per trillion or more, because they are derived from photosynthesis based starting material. Polysuccinimide is a polymer of formula: Polysuccinimide can be prepared by heating aspartic acid. E.g, and without limitation, polysuccinimide can be prepared by thermal polycondensation of aspartic acid as disclosed in Kokufuta et al., "Temperature Effect on the Molecular Weight and the Optical Purity of Acid," Bul. Chem. Soc. Japan, 61(5):1555-1556 (1978). See also, U.S. Pat. 16 Atty. Dkt. No.: LYGOS-0066-01-WO In some embodiments, polysuccinimide can be hydrolyzed to polyaspartic acid or a salt thereof. Polyaspartic acid is a random polyamide polymer of aspartic acid containing alpha (as in alpha amino acids) and beta (as in beta amino acids) amide links. Such linkages are determined among other methods by1H-NMR spectra. E.g, and without limitation, polyaspartic acid sodium salt can be illustrated, without limitation, as a compound having alpha and beta peptide linkages of formula: Aspartic acid can be prepared by fermentation employing a recombinant microorganism. A suitable microorganism includes Corneybacterieum glutamicum. See, e.g., PCT App. Pub. No. WO 2020 / 005834, incorporated herein by reference. See also, US Pat. App. Pub. No. US 20180258437, incorporated herein by reference. L-aspartic acid or a salt thereof can be which is e.g. and aqueous as can be prepared, e.g., and without limitation by known processes and can be adapted herein by a person skilled in the art. See, e.g., US 5,847,013, which is incorporated herein by reference in its entirety. Alternatively, in some embodiments, maleic acid or fumaric acid can be converted enzymatically to polyaspartic acid. In some embodiments, the maleic acid is bio-based. In some embodiments, the fumaric acid is bio-based. A product for absorption of bodily fluid comprising a superabsorbent, and methods for testing the same, are known to one of skilled in the art and can be adapted and modified by a person skilled in the art following this disclosure. 17 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO See, e.g., US 7,510,988 and US 7,696,401, each of which is incorporated herein in its entirety by reference. Superabsorbent polymers (SAPs) are crosslinked polymer networks of water-soluble building blocks. SAPs are generally composed of ionic monomers and are characterized, preferably, by a low cross-linking density, which results in a large fluid uptake capacity (e.g., and without limitation, up to 200 times, up to 500 times, or up to 1000 times their own weight). In one embodiment, the fluid is water. In one embodiment, the fluid is saline. In another embodiment, the fluid is urine. In one embodiment, the fluid is menstrual fluid. In one embodiment, the fluid is blood. In some embodiments, the superabsorbent polyaspartate provided herein have an FSC of about 100 – about 200 g water / g of SAP. In some embodiments, the superabsorbent polyaspartate provided herein have an FSC of about 26 - about 29 g saline / g SAP, or about 26 - about 48 g saline / g SAP, or about 30 - about 43 g saline / g SAP. Free swell capacity (FSC) refers to absorption capacity, e.g., in g of fluid absorbed / g of a superabsorbent, under zero pressure. In one embodiment, the molecular weight of the polymers was determined as follows. Characterization of base hydrolyzed PSI was performed by gel permeation chromatography (GPC), a type of size-exclusion chromatography (SEC), using the technique of relative molecular weight. The calibration standards used were polyacrylates of narrow dispersion and with a peak molecular weight (Mp) range of ~1,000 - 600,000 kilodalton (kDa). WinGPC software then derived a variety of molecular weight such as Mp and weight average molecular weight (Mw) of each sample from the polyacrylate molecular weight calibration; the calibration curves used could be of 4 or 9 points. In one embodiment, provided herein is a process comprising: reacting a crosslinked polysuccinimide of any one of claims 4-6 and 10 with alkali, adjusting the pH of the reaction to about pH 7, filtering the pH adjusted mixture, washing the residue with water and isopropanol, and optionally drying the residue, to provide a crosslinked polyaspartic acid or a salt thereof. In another embodiment, the crosslinked polysuccinimide is produced comprising reacting polysuccinimide with a crosslinker compound of formula: H2N(CH2)2-X-(CH2)2-X-(CH2)2NH2; HO-L-OH; or epoxy-L-epoxy 18 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO wherein each X independently is O, S, SO or SO2and L is a C2-C12, preferably a C4-C8, alkylene or heteroalkylene, to provide the crosslinked polysuccinimide; and the polysuccinimide is in a mixture comprising an acid and the polysuccinimide. In another embodiment, the crosslinker compound reacted is about 0.1% - 15%, about 0.1% - 10%, about 0.5% - 8%, about 1%-6%, preferably about 3-4% by weight of the polysuccinimide. In another embodiment, the crosslinker compound hexamethylene diamine reacted is about 3% by weight of the polysuccinimide. In another embodiment, the crosslinker compound H2N(CH2)2O(CH2)2O(CH2)2NH2reacted is about 4% by weight of the polysuccinimide. In another embodiment, the polysuccinimide reacted has a weight average molecular weight (Mw) of at least about 30,000, or at least about 50,000, or at least about 70,000 to about 200,000, preferably about 50,000 to about 85,000. In another embodiment, the polysuccinimide reacted has a number average molecular weight (Mn) of about 15,000 to about 90,000, or of about 15,000 to about 40,000 or preferably about 20,000 to 30,000. In another embodiment, the mixture comprising an acid and the polysuccinimide is prepared by a process comprising polymerizing aspartic acid by heating in presence of the acid. In another embodiment, provided herein is a crosslinked polyaspartic acid or a salt thereof provided by a process provided herein. Non limiting and illustrative preparations of PSI and crosslinking PSI to produce polyaspartic acid or a salt thereof are provided in FIGURES 1A-D and 2. For example, applications and articles of manufacture include the use of polymeric networks provided herein as superabsorbents in diapers, incontinence products and sanitary napkins; as humectants in agricultural products; as sludge coagulants in water treatment; as viscosity modifiers in the petroleum industry; as dehydrating agents; as chemical absorbents (for example for clean-up of chemical spills); for controlled release of chemicals; for microencapsulation; as thickening agents; rheology modifiers; agricultural water retention; environmental remediation; as media for electrophoresis and chromatography (for example for gel permeation chromatography, capillary electrophoresis, etc.); in soft contact lens 19 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO manufacture; and as moisturizing components in consumer products, such as personal care products or the like. A SAP provided herein is tested by the following illustrative and non-limiting method. The SAP is utilized in the production of: 12, A4 sized handsheets containing thermofibers and fluff pulp; and 12, A4 sized handsheets treated with a chemical binder. Said handsheets are calendered to a desired density. Handsheets are tested as follows: 5 handsheets from each group above will be evaluated for absorbency, acquisition time, and rewet using 0.9% saline; and 5 handsheets from each group above will be evaluated for absorbency, acquisition time, and rewet using a menstrual fluid proxy material (such as defibrinated ovine blood or the like). EXAMPLES Example 1: Phosphoric acid catalyzed polymerization of L-aspartic acid to produce acidified linear polysuccinimide. A planetary mixer bowl (Kitchen aid) was charged with L-aspartic acid (425.13 g) and 85% phosphoric acid (148.5 mL, 252.13 g). See Fig.1B. The bowl was placed on the planetary mixer stand and the bowl was equipped underneath with a hot water bath set at 50-60 °C. Mixing was done for 30-40 minutes, and the planetary mixer bowl contents were separated into two glass dishes having a PTFE film. A thermocouple was fixed (with Kapton tape) to the PTFE layer at the bottom of the glass dish; this was used to monitor the temperature throughout the reaction. The first glass dish contained 301.5 g of the reaction mixture paste and the second contained 306.6 g. The mixture was spread with a spatula to even thickness and both glass dishes were placed in the vacuum oven (preheated to 180 °C) equipped with a bucket condenser with dry ice / IPA for volatiles (water and phosphoric acid) condensation. The vacuum of the system was regulated throughout the first 2 hours of the reaction as bubbling (due to water evolution, a by-product of the polycondensation) and expansion occurred. Vacuum 20 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO regulation was done by opening the oven to the atmosphere slightly to prevent reaction mixture spillage. The final pressure reached was 29.5 mm Hg. After two hours of reaction time, the vacuum oven was opened to atmospheric pressure and the solid tacky reaction mixture was removed from the PTFE layer with a spatula. This intermediate polysuccinimide was ground in a blender resulting a yellowish powder; a sample was taken for characterization by gel permeation chromatography (GPC). The powder was spread evenly throughout the same PTFE coated glass dish and placed in the vacuum oven at 180 °C and 29.5 mm Hg of vacuum to continue the reaction. The process of removing the solid reaction mixture from the PTFE film, grinding in the blender, returning to the PTFE coated glass dish (and sampling in some instances), was repeated after 4 and 6 hours of reaction time, for a total of 3 times. Characterization of base hydrolyzed PSI was performed by gel permeation chromatography (GPC), a type of size-exclusion chromatography (SEC), using the technique of relative molecular weight. The calibration standards used were polyacrylates of narrow dispersion and with a peak molecular weight (Mp) range of ~1,000 - 600,000 kilodalton (kDa). WinGPC software then derived a variety of definitions of molecular weight such as Mpand weight average molecular weight (Mw) of each sample from the polyacrylate molecular weight calibration. From reaction time 6 hours to 22 hours, the reaction was allowed to continue undisturbed at 180 °C and 29.5 mm Hg vacuum. A sample of the final reaction mixture was analyzed by GPC and the Mwobtained ranged from 30 to 120 kDa. Mwof up to 200 kDa are contemplated in accordance with this procedure. Materials with low Mw(<70 kDa) were further reacted by placing in a PTFE coated glass dish for an additional 6 hours in the vacuum oven at 180 °C and 29.5 mm Hg. For example, PSI with Mwof 32.471 kDa subjected to 6 hours of further reaction time achieved a Mwof 70.476 kDa. Acidified PSI batches that met the required Mwof 60-80 kDa were combined in large batches. For example, a 5-gallon vessel equipped with overhead stirring was charged with 2.2 kg of combined acidified PSI followed by 15 L of saturated sodium bicarbonate solution and 21 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO mixed for 1 hour. See Fig.1C. Stirring was discontinued, the solids settled, and the pH was determined to be 6.43 while the conductance was 111.4 mS. Conductance measurements were made using an Oakton conductivity probe. The mixture was decanted and to the solids remaining in the 5-gal vessel was added 12 L of deionized water and mixed for 30 min. Mixing was discontinued and the mixture was allowed to settle; pH and conductance were determined, and the liquid was decanted. This water rinsing was repeated for a total of four (4) times and the resulting pH and conductance were 7.68 and 0.1142 mS, respectively. The 5-gal vessel was charged with wet low conductance PSI and 4 L of methanol and stirred for 30 min; the mixture was first decanted through a 400 µm stainless steel mesh then the solids were vacuum filtered. The water / methanol wet PSI was distributed amongst 2 glass dishes and both were dried overnight at 71 °C; results of each drying batch are as followed: Batch number, drying Water / methanol Dry non- Percent Moisture water / methanol wet wet PSI mass (g) sized PSI solids after balance (% PSI mass (g) drying (%) moisture)11 1082.2 714.0 65.98 8.149 2 1218.9 813.9 66.77 10.1291Moisture balance analysis done on 0.6 g sample heated to 150 °C until mass loss reached a plateau. The moisture balance indicated >8% moisture for both batches of PSI (totaling 1,527.9 g) so the two lots were combined and drying continued for 3 days under vacuum at 71 °C; 1422.3 g (93.1% solids after drying) of dry non-sized PSI were recovered. A. Sieving of dry non-sized polysuccinimide bot rtical and horizontal vibration. All dry PSI with particle size range of 106-850 µm was combined and 22 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO the resulting dry sized PSI was characterized by GPC (Mw77,766; Mn17,432) and Karl-Fischer (KF) water (4.42%). Example 2A: Cross-linking of polysuccinimide to form cross-linked polysuccinimide polyaspartatic acid superabsorbent on a planetary mixer A planetary mixer was charged with iced water (798.19 g), ammonium hydroxide (28- 30%, 88.8 g), and the crosslinker compound Jeffamine® EDR-148 (H2N(CH2)2O(CH2)2O(CH2)2NH2; 8.32 g) (Huntsman, Corp.); everything was thoroughly mixed. Finally dry sized PSI (200.76 g) was added to the reaction mixture and the planetary mixer bowl was placed in a hot water bath at 45 °C. Within 5 min of PSI addition, the reaction mixture became a gel. Without being bound by theory at this point the PSI has been at least partially hydrolyzed to polyaspartic acid or a salt thereof, that becomes partially water soluble and gels; there may exist dry section inside the gelled particles. Mixing was continued and the pH was determined to be 7.26; the hot water bath was removed from underneath the reaction bowl and 2 L of deionized or distilled water was added to the reaction mixture, swelling the cross-linked PSI. Use of another base (instead of or together with ammonium hydroxide) such as but not limited to metal hydroxides is contemplated. Use of or another diamine, diol, carbodiimide or diepoxide as utilized in this disclosure as a crosslinker compound is contemplated. A person of skill in the art will recognize after reading this disclosure that electrophilic crosslinker compounds are employed preferably with polyaspartates or polyaspartic acid as opposed to with PSI. Example 2B: Cross-linking of polysuccinimide to form cross-linked polysuccinimide polyaspartatic acid superabsorbent on a double planetary mixer A Ross Model LDM-4 Double Planetary jacketed mixer with 19.9 L full holding capacity equipped with traditional rectangular stirrer blades and a scraper arm with Teflon scraper blade as well as one Teflon scraper blade mounted to one stirrer bottom was charged dry sized PSI (1000.3 g), iced water (4000 g), then ammonium hydroxide (28-30%, 88.8 g), and the mixture was thoroughly mixed. Finally, the crosslinker compound Jeffamine® EDR-148 (H2N(CH2)2O(CH2)2O(CH2)2NH2; 40. g) was added to the reaction mixture; the reactor heater was started and set to 40 °C and the reaction proceeded for 1 hour resulting in a highly viscous 23 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO cross-linked PSI. Without being bound by theory at this point the PSI has been at least partially hydrolyzed to polyaspartic acid or a salt thereof, that becomes partially water soluble and gels; there may exist dry section inside the gelled particles. The reaction mixture was diluted with deionized or distilled water (7.2 kg), swelling the cross-linked PSI. Use of another base (instead of or together with ammonium hydroxide) such as but not limited to metal hydroxides is contemplated. Use of or another diamine, diol, or diepoxide as utilized in this disclosure as a crosslinker compound is contemplated. Example 3A: Hydrolysis of cross linked PSI to provide cross-linked polyaspartic acid superabsorbent Sodium hydroxide aqueous solution (50%) was added to the cross-linked PSI as followed, while mixing on the planetary mixer at ambient temperature: Reaction 50% sodium 50% sodium pH before Notes time hydroxide mass hydroxide molar base (hour) (g) equivalents2addition 0 15.59 0.09423 Over 3 min 0.05 15.82 0.09562 9.42 Over 3 min 0.42 15.51 0.09375 9.83 Over 2 min; pH spiked to 10.17 0.77 15.42 0.09320 10.012Molar equivalents are calculated using the following assumptions: 100% of the starting PSI mass; PSI molecular weight of 97.07 g / mol. The reaction mixture was transferred to a 3.5 gallon vessel equipped with overhead stirring. The mixture was charged with 2L of water and the pH measured was 9.59. Sodium 24 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO 5.70 6.22 0.0376 9.84 pH 10.11 after base addition After a total of 83.68 g (0.5058 molar equivalents) of 50% sodium hydroxide was added to the cross linked PSI, the hydrolysis was continued for a total of 22 hours at ambient temperature while stirring, resulting a pH of 9.82. A sample was taken for analysis under a microscope and there was no evidence of undissolved PSI so the pH of the cross-linked polyaspartatic acid was adjusted by adding 12.37 g (8.2 mL) of 60% sulfuric acid resulting a pH The superabsorbent polymer (SAP) filtration, deionized or distilled water, and isopropyl alcohol (IPA) rinses were performed using a 37 µm nylon mesh on a 24 inch table top polyethylene Büchner funnel with a porous removable plate. Removal of salts present in the SAP is important as their presence may lead to decreased superabsorbent performance. The SAP was filtered through a mesh and the 1.96 kg of filtrate were recovered; the latter is any non-cross-linked polymer or water-soluble cross- linked polymer. Water (7.98 kg) was added directly on top of the SAP located on the filter. The SAP and water were mixed until they appeared homogeneous; the material was constantly moved to help with water gravity filtering through the SAP. The total filtrate recovered was 4.87 kg which resulted in SAP conductance of 4.42 mS and pH 7.46. Subsequent water rinses are described in the table below. SAP Water Filtrate Filtrate SAP Water mass Water mass water mass mass conductance conductance retained by retained by SAP rinse (kg) (kg) (µS) (µ SAP (kg) (%) number S) 1 7.98 4.87 NA 4420 3.11 39.00 2 8.00 4.65 1,499 NA 3.35 41.89 25 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO 3 7.98 4.39 637 NA 3.59 44.96 4 8.14 4.13 432 1043 4.01 49.29 5 8.06 4.71 254 757 3.35 41.55 total 40.16 22.75 17.41 43.36 on g To affect SAP performance, in some processes the amount of isopropyl alcohol used to rinse the water washed neutral pH SAP is from about 5 g to about 500 g of IPA per gram of PSI; the amount of soaking time can be from about 1 min to about 2 hours; and the soaking temperature from about 10 to 50 °C; followed by drying. To affect SAP performance, in some processes the water and IPA rinses are alternated, where the final rinse is IPA followed by drying. Wet (water / IPA) low salt SAP drying and sizing Drying of the wet low salt SAP was done in glass dishes with PTFE liners using a convection oven at 60 °C for a minimum of 3 days. The dried SAP was milled using an IKA impact or cutting grinder at 3000-4500 rpm and a 2 mm sieve. A hammer was used to break up large chunks of SAP. • Combined starting SAP weight: 1181.4 g 26 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO • Combined SAP weight (post mill): 1166.8 g • SAP was analyzed for KF water showing 6.19-6.42% water The SAP was further dried overnight in a vacuum oven with setpoint at 100 °C. The post- drying mass was 1089 g, and the SAP had an average 1.49% water as determined by KF titration. The SAP was sieved using an 850 and 150 µm sieve stack mounted on a shaker that provides horizontal and vertical vibration. Shaking was done for 15 minutes resulting the following mass split: Particle size SAP mass (g) SAP mass percent (%) 1>850 µm 393.0 36.0 150-850 µm542.9 49.7<150 µm156.5 14.3Total 1092.4 100.0 The SAP with particle size > 850 was milled using a 1 mm sieve at 4500 rpm. The milled material was sieved with an 850 and 150 µm sieve stack on a shaker (described above). The final particle size distribution was as followed combining all SAP material that had been milled: ) Dry SAP with particle size ranging from 150-850 µm was placed in a convection oven at 100 °C to dry overnight. 27 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO Example 4: Perfor rabsorbent Tea bags ( bags are placed in 0.9% w / w sodium ed or deionized water) and remain submerged for 30 minutes. Excess saline is allowed to drip from the teabags and the freeswell capacity (FSC, g saline / g of SAP) is calculated from wet and dry SAP masses; this evaluates all of the fluid imbibed by a sample of SAP, including interstitial fluid in the polymer network. The wet SAP teabags are then centrifuged for 3 minutes and the removal of this interstitial fluid by centrifugation (CRC, centrifuge retention capacity) leads to a value for the capacity of the polymer only. FSC FSC percent of CRC CRC percent of (g / g) control3(%) (g / g) control*(%) 26.0 52.4 18.1 55.7*The control is a sodium acrylate-based superabsorbent polymer (arctic gel). Crosslinked polyaspartate (a polyaspartic acid salt) superabsorbents have a polymer backbone which, as opposed to polyacrylate, the constituent of Arctic Gel brand superabsorb ction substantially urther modify and fine-tun -based nature of the crosslinked polyaspartate superabsorbents, they offer distinct environmental advantages, while performing as a superabsorbent as demonstrated in the Examples herein. Example 5: Producing Crosslinked Polyaspartate SAP From Acidic PSI Without Prior Neutralization This example describes a process of reacting acidic PSI, without prior neutralization, with crosslinkers for preparing polyaspartate SAPs. This process is contemplated to have certain benefits, especially for commercial manufacturing, over a process utilizing prior neutralized PSI for crosslinking. 28 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO A planetary mixer (Kitchen aid) equipped with a double scrape blade, a temperature probe, and water bath with liquid temperature controlled by heater chiller, was heated to 40 °C and charged with hexamethylenediamine (HMDA, 3.85 g, 50% in water), followed by deionized or distilled water (189.47 g), and finally the acidified polysuccinimide (PSI, 100.00 g, containing 40.00% phosphoric acid) resulting a heterogeneous reaction mixture. Acidified PSI results from the polymerization of L-aspartic acid in the presence of phosphoric acid at 180 °C, under vacuum, with intermittent mixing, as described in Example 1. The crude polymerization reaction mixture is used as is for production of crosslinked polyaspartate SAP, without any further processing such as washing for phosphoric acid removal, drying, or sizing. Phosphoric acid content in acidified PSI can be from about 5 to 50%, or from about 20 to 40. Sodium hydroxide solution (50%, 152 g) was charged to the acidified PSI, HMDA, water reaction mixture at a rate of 0.030 g of NaOH / g of PSI / min (0.073 mol eq / min) resulting in a reaction exotherm. Heating was stopped upon sodium hydroxide addition and the reaction mixture was diluted with 1.3 L of deionized or distilled water; the reaction was allowed to stir at ambient temperature for 10 to 90 minutes. The pH was adjusted to 7 with 60% sulfuric acid and the mixture was filtered through a 37 µm nylon mesh mounted on a funnel. Deionized or distilled water rinsing of SAP uses 340-430 g water / g PSI until a conductance 1.50 mS or lower is achieved, followed by isopropyl alcohol rinse using 48 g IPA / g PSI and finally drying in a convection oven at 60°C for at least 24 hours. In some processes the isopropyl rinse uses 143 g IPA / g PSI followed by drying in a convection oven at 60 °C for at least 24 hours. The impact of water and IPA rinses on SAP performance can be observed in the following table where varying amounts were used. SAP Downstream Free Swell FSC % Centrifuge Retention CRC % Experiment Processing Capacity (FSC, g from Capacity (CRC, g from Method* saline / g SAP) control saline / g SAP) control A 1 34.8 ± 0.6 70.0% 29.6 ± 0.7 89.9% B 1 32.6 ± 2.5 65.6% 28.3 ± 2.1 86.2% C 2 47.3 ± 1.5 95.1% 35.4 ± 0.4 107.7% 29 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO *Method 1: filtration; rinse 1 uses 340-430 g water / g PSI; rinse 2 uses 48 g IPA / g PSI. Method 2: different rinse 2 which uses 143 g IPA / g PSI of i. A fritted glass filter is placed in a Petri dish and the dish is filled with 0.9% saline and a filter paper is placed on the glass filter and allowed to fully wet. The SAP is loaded into the AAP cell (a cylinder, approximately 50-60 centimeters in diameter with a mesh on one end), ensuring the SAP is evenly distributed, and nonwoven material placed over the SAP. A piston is loaded on the SAP and a metal weight is put on top of the piston; this assembly is placed on the glass filter in the Petri dish and the sample is left untouched for 30 min. The cell is removed from the petri dish and from the weight of the SAP, SAP and dry cell, and wet SAP and cell, the AAP is calculated. b. Absorption speed determined the rate of 0.9% saline absorption by a superabsorbent polymer. i. A sample of SAP is placed in an AAP cell, a piston is placed on the sample and the test cell assembly is held under the Linear Variable Inductance Transducer (LVIT, which is positioned vertically) and lowered onto the filter paper that is in the petri dish with the fritted glass filter and saline to start the test. As the SAP swells, the LVIT is pushed upward and the LVIT output is processed to record swelling as a function of time. ii. Example of data obtained from LVIT to determine absorption speed. iii. Absorption rate over time is calculated from saline absorbed over time. T-20 is the time in seconds for the SAP to absorb 20 g of saline. 30 DMS_US.367315943.1 Atty. Dkt. No.: LYGOS-0066-01-WO 1. A is for Artic GelTMSAP, our control here: 300-600 micro meter (um) PSD. L is for Lygos SAP - here 300-600 um PSD c. Freeswell Permeability measures the 0.9% saline flow through the superabsorbent polymer. beaker.50 mL of saline is poured through a funnel to the top of the gel bed. As fluid passes through the gel it drains into the beaker providing a time-dependent fluid mass curve which represents the permeability of the SAP. See also, FIGURES 10A and B. Example 6: Preparation and rewet tests of pads including a SAP provided herein FIGs.3-9 and the associated commentary illustrate preparation and results of rewet tests of pads including a SAP provided herein. A modified version of EDANA / INDA NSP570.9.R2 is used for the rewet testing. For the rewet test the following amounts of fluids and conditions were used: 3x 10 ml fluid; 1ml / min; 10 min wait; 2 min rewet. The results demonstrate the usefulness of the SAP in improving the dryness and absorption properties of pads. 31 DMS_US.367315943.1

Claims

Atty. Dkt. No.: LYGOS-0066-01-WO CLAIMS 1. A crosslinked polyaspartic acid or a salt thereof (a crosslinked polyaspartate salt) comprising a polyaspartic acid or a salt thereof (a polyaspartate salt) and a crosslinker, which has a particle size of up to about 1,000 micrometer, preferably up to about 850 micrometer, more preferably from about 150 micrometer to about 850 micrometer.

2. The crosslinked polyaspartic acid or a salt thereof of claim 1, which is prepared from a polysuccinimide (PSI) having a weight average molecular weight (Mw) of at least about 5,000, or at least about 50,000, or at least about 70,000 to about 200,000, preferably about 50,000 to about 85,000.

3. The crosslinked polyaspartic acid or a salt thereof of claim 1, which is prepared from a polysuccinimide (PSI) having a number average molecular weight (Mn) of about 15,000 to about 90,000, about 15,000 to about 40,000, or preferably about 20,000 to 30,000.

4. A crosslinked polysuccinimide (PSI) comprising a polysuccinimide and a crosslinker, which has a particle size of up to about 1,000 micrometer, preferably up to about 850 micrometer, more preferably from about 150 micrometer to about 850 micrometer.

5. The crosslinked polysuccinimide of claim 4, which has a weight average molecular weight (Mw) of at least about 30,000, or at least about 50,000, or at least about 70,000 to about 200,000, preferably about 50,000 to about 85,000.

6. The crosslinked polysuccinimide of claim 4, which has a number average molecular weight (Mn) of about 15,000 to about 90,000, about 15,000 to about 40,000, or preferably about 20,000 to 30,000.

7. An aqueous composition comprising the crosslinked polyaspartic acid or a salt thereof of any one of claims 1-3. 32 DMS_US.367315943.1Atty. Dkt. No.: LYGOS-0066-01-WO 8. The aqueous composition of claim 7, Having a conductance of less than or equal to 1.5 mS; or the crosslinked polyaspartic acid or a salt thereof of any one of claims 1-3 having a free swell capacity (fsc) of at least about 20 g / g, or at least about 25 g / g, to about 50 g / g; or having a centrifuge retention capacity (CRC) of at least about 5 g / g, or at least about 20 g / g, to about 40 g / g; or having a time in seconds for the superabsorbent to absorb 20 cubic centimeters of 0.9% saline (T-20) of about 40 to about 400, or preferably about 130 to about 210. having a maximum free swell saline permeability of at least about 1.0 g / s, or at least 2.0 g / s to about 4.0 g / s.

9. The crosslinked polyaspartic acid or a salt thereof of any one of clams 1-3 or the aqueous composition of claim 7 or 8, wherein less than: about 5%, about 4%, about 3%, about 2%, preferably, less than about 1%, or less than about 0.5% by moles of the polyaspartic acid or a salt thereof is a linear as opposed to a branched polymer.

10. The crosslinked polysuccinimide of any one of clams 4-6, wherein less than: about 5%, about 4%, about 3%, about 2%, preferably, less than about 1%, or less than about 0.5% by moles of the polysuccinimide is a branched as opposed to a linear polymer.

11. The crosslinked polyaspartic acid or a salt thereof of any one of clams 1-3 or the aqueous composition of claim 7 or 8, wherein the crosslinker is a: -HN-L-NH-, -HN(CH2)2X(CH2)2X(CH2)2NH-, an -O-L-O-, or RNHCON(-)L(-)CONHR moiety, which is bound at each end to a carbonyl group of a polyaspartic acid or a salt thereof via the “-” of the crosslinker, wherein each X independently is O, S, SO or SO2, L is a C2-C12, preferably a C4-C8, alkylene or heteroalkylene, and R is a hydrocarbyl group; or wherein the crosslinker is a: -CH2CH(OH)-L-CH(OH)CH2- 33 DMS_US.367315943.1Atty. Dkt. No.: LYGOS-0066-01-WO moiety, which is bound at each end to a -CO2- group of a polyaspartic acid or a salt thereof.

12. The crosslinked polyaspartic acid or a salt thereof of any one of clams 1-3 and 11, or the aqueous composition of claim 7 or 8, wherein the crosslinker is about 0.1% - 15%, about 0.1% - 10%, about 0.5% - 8%, about 1%-6%, preferably about 4% by weight of rest of the crosslinked polyaspartic acid or a salt thereof.

13. The crosslinked polysuccinimide of any one of claims 4-6, wherein the crosslinker is a: -HN-L-NH-; -HN(CH2)2-X-(CH2)2-X-(CH2)2NH-, or an -O-L-O- moiety, which is bound at each end to a carbonyl group of a polysuccinimide via the “-” of the crosslinker, wherein each X independently is O, S, SO or SO2, L is a C2-C12, preferably a C4-C8, alkylene or heteroalkylene, and R is a hydrocarbyl group.

14. The crosslinked polysuccinimide of any one of clams 4-6 and 13, wherein the crosslinker is about 0.1% - 15%, about 0.1% - 10%, about 0.5% - 8%, about 1%-6%, preferably about 4% of rest of the crosslinked polysuccinimide.

15. A process comprising: reacting a crosslinked polysuccinimide of any one of claims 4-6 and 10 with alkali, adjusting the pH of the reaction to about pH 7, filtering the pH adjusted mixture, washing the residue with water and isopropanol, and drying the residue, to provide a crosslinked polyaspartic acid or a salt thereof.

16. The process of claim 15, wherein the crosslinked polysuccinimide is produced comprising reacting a polysuccinimide, which is less than: about 5%, about 4%, about 3%, about 2%, preferably, less than about 1%, or or less than about 0.5% by moles branched as opposed to linear, with a crosslinker compound of formula: H2N-L-NH2; H2N(CH2)2-X-(CH2)2-X-(CH2)2NH2; or HO-L-OH; wherein each X independently is O, S, SO or SO2and L is a C2-C12, preferably a C4-C8, alkylene or heteroalkylene, 34 DMS_US.367315943.1Atty. Dkt. No.: LYGOS-0066-01-WO to provide the crosslinked polysuccinimide.

17. The process of claim 16, wherein the crosslinker compound reacted is about about 0.1% - 15%, about 0.1% - 10%, about 0.5% - 8%, about 1%-6%, preferably about 4% by weight of the polysuccinimide.

18. The process of claim 16, wherein the polysuccinimide reacted has a weight average molecular weight (Mw) of at least about 30,000, or at least about 50,000, or at least about 70,000 to about 200,000, preferably about 50,000 to about 85,000.

19. The process of claim 16, wherein the polysuccinimide reacted has a number average molecular weight (Mn) of about 15,000 to about 90,000, about 15,000 to about 40,000, or preferably about 20,000 to 30,000.

20. A process comprising: reacting a crosslinked polysuccinimide of any one of claims 4-6 and 10 with alkali or NH4OH, adjusting the pH of the reaction to about pH 1, filtering the pH adjusted mixture, washing the residue with water and isopropanol, further adjusting the pH to 7, and drying the residue, to provide a crosslinked polyaspartic acid or a salt thereof.

21. The process of claim 20, wherein the crosslinked polysuccinimide is produced comprising reacting polysuccinimide with a crosslinker compound of formula: H2N-L-NH2; H2N(CH2)2-X-(CH2)2-X-(CH2)2NH2; or HO-L-OH wherein each X independently is O, S, SO or SO2and L is a C2-C12, preferably a C4-C8, alkylene or heteroalkylene, to provide the crosslinked polysuccinimide.

22. The process of claim 21, wherein the crosslinker compound reacted is about 0.1% - 15%, about 0.1% - 10%, about 0.5% - 8%, about 1%-6%, preferably about 4% by weight of the polysuccinimide. 35 DMS_US.367315943.1Atty. Dkt. No.: LYGOS-0066-01-WO 23. The process of claim 21, wherein the polysuccinimide reacted has a weight average molecular weight (Mw) of at least about 30,000, or at least about 50,000, or at least about 50,000 to about 200,000, preferably about 50,000 to about 85,000.

24. The process of claim 21, wherein the polysuccinimide reacted has a number average molecular weight (Mn) of about 15,000 to about 90,000, about 15,000 to about 40,000, or preferably about 20,000 to 30,000.

25. The crosslinked polyaspartic acid or a salt thereof provided by the process of any one of claims 20-24.

26. An article of manufacture comprising the crosslinked polyaspartic acid or a salt thereof of any one of clams 1-3 and 25, or the aqueous composition of claim 7 or 8.

27. The article of manufacture of claim 26, which is a diaper, a feminine hygiene product, or a gel pack.

28. The article of manufacture of claim 26, which is a diaper or a feminine hygiene product, comprising about 0.4 g to about 4.0 g of the SAP provided herein, or comprising about 5% - about 50% (i.e., [wt of SAP / wt of (SAP+fluff)]x100)) of the SAP provided herein.

29. A process comprising: reacting a crosslinked polysuccinimide of any one of claims 4-6 and 10 with alkali, adjusting the pH of the reaction to about pH 7, filtering the pH adjusted mixture, washing the residue with water and isopropanol, and optionally drying the residue, to provide a crosslinked polyaspartic acid or a salt thereof.

30. The process of claim 29, wherein the crosslinked polysuccinimide is produced comprising reacting polysuccinimide with a crosslinker compound of formula: H2N-L-NH2; H2N(CH2)2-X-(CH2)2-X-(CH2)2NH2or HO-L-OH 36 DMS_US.367315943.1Atty. Dkt. No.: LYGOS-0066-01-WO wherein each X independently is O, S, SO or SO2, L is a C2-C12, preferably a C4-C8, alkylene or heteroalkylene, to provide the crosslinked polysuccinimide; and the reacted polysuccinimide is in a mixture comprising an acid and the polysuccinimide.

31. The process of claim 30, wherein the crosslinker compound reacted is about 0.1% - 15%, about 0.1% - 10%, about 0.5% - 8%, about 1%-6%, preferably about 4% by weight of the polysuccinimide.

32. The process of claim 30, wherein the polysuccinimide reacted has a weight average molecular weight (Mw) of at least about 30,000, or at least about 50,000, or at least about 70,000 to about 200,000, preferably about 50,000 to about 85,000.

33. The process of claim 30, wherein the polysuccinimide reacted has a number average molecular weight (Mn) of about 15,000 to about 90,000, about 15,000 to about 40,000, or preferably about 20,000 to 30,000.

34. The process of claim 30, wherein the mixture comprising the acid and the polysuccinimide is prepared by a process comprising polymerizing aspartic acid by heating in presence of the acid.

35. The process of any one of claims 30-34, wherein the crosslinker compound is hexamethylenediamine or a salt thereof.

36. The crosslinked polyaspartic acid or a salt thereof provided by the process of any one of claims 29-35. 37 DMS_US.367315943.1

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