Crosslinked polysaccharide, obtained by crosslinking with substituted polyethylene glycol, as superabsorbent
New crosslinked polysaccharides useful as absorbents or superabsorbents alone or in a mixture are obtained by reacting polysaccharides (preferably containing carboxylates groups) with at least one crosslinker selected in the group constituted by activated polyethylene glycols such as for example halogenated (Cl, Br, I), mesylated, tosylated, or triflated activated polyethylene glycols.
1. A cross-linked polysaccharide said cross-linked polysaccharide being a polysaccharide cross-linked by a backbone chain of atoms, said backbone chain of atoms having the formula 2
wherein each Alkylene consists of one or more unsubstituted —CH 2 — groups, and wherein n is an integer ranging from 1 to 100.
2. A cross-linked polysacoharide as defined in claim 1 wherein n is 1, 2 or 3.
3. A cross-linked polysaccharide as defined in claim 1 , wherein each Alkylene comprises from 1 to 5 —CH 2 — groups.
4. A cross-linked polysaccharide as defined in claim 3 wherein said alkylene is a —CH 2 —CH 2 — group.
5. A cross-linked polysaccharide as defined in claim 4 wherein n is 1, 2 or 3.
6. A cross-linked polysaccharide as defined in claim 1 , wherein said backbone chain of atoms is a group of formula Polysaccharide-O—CH 2 —CH 2 —O—CH 2 —CH 2 —O-Polysaccharide.
7. A mixture for use in a food pad; in sanitary napkins; in diapers; in incontinence products; in agricultural and forestry applications to retain water in soil and to release water to the roots of plants; in fire-fighting techniques; bandages and surgical pads; for cleanup of acidic or basic aqueous solutions spills, including water soluble chemicals spills and; as polymeric gels for cosmetics and pharmaceuticals also known as drug delivery systems and slow release substances; and for artificial snow, said mixture comprising a cross-linked polysaccharide as defined in claim 1 and one or more other known absorbents.
8. A cross-linked polysaccharide as defined in claim 1 , wherein the polysaccharide is
a starch selected from the group consisting of starches derived from corn, wheat, rice, potato, tapioca, waxy maize, sorghum, sago and waxy sorghum;
a modified starch selected from the group consisting of dextrinated, hydrolysed, oxidized, alkylated, hydroxyalkylated, acetylated and fractionated starches;
a member selected from the group consisting of cellulose, dextrins, polygalactomannans, ionic and/or non ionic derivatized, chitin, chitosan, alginates, xanthan gum, carageenan gum, karaya gum, arabic gum, pectin and glass-like polysaccharides; or
a member selected from the group consisting of an anionic and a cationic polysaccharide.
9. A cross-linked polysaccharide as defined in claim 8 wherein the anionic polysaccharides are substituted with anionic groups selected from the group consisting of dicarboxylate and tricarboxylate groups.
10. A cross-linked polysaccharide as defined in claim 8 wherein the anionic polysaccharides are substituted with anionic groups selected from the group consisting of iminodiacetate groups and citrate groups.
11. A cross-linked polysaccharide as defined in claim 8 , wherein said anionic polysaccharide is an anionic starch.
12. A cross-linked polysaccharide as defined in claim 11 . wherein said anionic starch is a carboxyalkyl starch, wherein the alkyl comprises from 1 to 3 carbon atoms.
13. A cross-linked polysacchande as defined in claim 12 , wherein said carboxyalkyl starch is a carboxymethyl starch.
14. A cross-linked polysaccharide as defined in claim 8 , wherein said starch is a starch half ester selected from the group consisting of starch maleate half ester, starch succinate half ester, starch sulfosuccinate half ester, starch citraconate half ester, starch glutarate half ester and starch phthalate half ester.
15. A cross-linked polysaccharlde as defined in claim 1 , wherein said cross-linked polysaccharide is obtained by reacting a polysacchande with an activated polyalkylene glycol having the formula 2a
below
wherein each alkylene consists of one or more —CH 2 — groups, wherein n is an integer ranging from 1 to 100, and wherein X is selected from the group consisting of halogen, mesylate, tosylate and triflate.
16. A cross-linked polysaccharide as defined in claim 15 , wherein said halogen is selected from the group consisting of chloride, bromide and iodide.
17. A cross-linked polysaccharide as defined in claim 16 , wherein said halogen is chloride.
18. A cross-linked polysaccharide as defined in claim 17 , wherein said alkylene comprises from 1 to 5 —CH 2 — groups.
19. A cross-linked polysaccharide as defined in claim 18 , wherein said alkylene is an ethylene group.
20. A cross-linked polysaccharide as defined in claim 19 , wherein n is 1, 2 or 3.
21. A cross-linked polysaccharide as defined in claim 15 , wherein said activated polyalkylene glycol has an average molecular weight of 10,000 or less.
22. A cross-linked polysaccharide as defined in claim 21 , wherein said activated polyalkylene glycol has an average molecular weight of 300 or less.
23. A cross-linked polysaccharide as defined in claim 15 , wherein said activated polyalkylene glycol is selected from the group consisting of 1,5-dichloro-3-oxopentane, 1,8-dichloro-3,6-dioxooctane and 1,11-dichloro-3,6,9-trioxoundecane.