Polyetheramidoamine superabsorbent hydrogels

Details Polyetheramidoamine superabsorbent hydrogels Polyetheramidoamine superabsorbent hydrogels

1994-11-22

1996-11-05

Seidleck, James J.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From carboxylic acid or derivative thereof

528170, 528176, 528183, 528192, 528194, 528220, 528223, 528224, 528228, 528229, 528310, 528322, 528345, 604368, C08G 7302, A61L 1500, A61L 1300

Patent

active

055718906

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to polyetheramidoamine hydrogels, to processes for the preparation thereof and to the use thereof as superabsorbent materials.
The commonly so called superabsorbent materials are hydrophilic polymers, having different chemical structure, which are capable of absorbing and retaining aqueous fluids even under moderate pressure in amounts equals to many time their own weight, without substantially dissolving into the liquid itself.
Superabsorption characteristics are given by the presence, in the fundamental structure, of ionizable groups, which are generally of the anionic type (carboxylates) and are partially or totally salified; when in contact with water, said groups dissociate and solvatate.
When dissociated, the functional groups along the polymeric chain have the same electric charge, therefore repel each other.
This fact causes a widening of the polymeric lattice, therefore a further absorption of water molecules is possible.
Generally, in order to avoid that such a process may lead to the dissolution of the polymer, this last is crosslinked by means of suitable agents as to make the gel substantially insoluble.
Accordingly, the absorption of water allows a substantial swelling of the polymer only.
Liquid absorption from polyelectrolytic superabsorbents is strongly adversed by the concentration of dissolved electrolytic salts.
In fact, the ions, coming from the dissociation of the salts, interact with the global charge of the macroion of the polymer, thus reducing the repelling potential between its functional groups, consequently also the absorbing capacity will decrease.
As a consequence, the absorbing capacity drastically decreases passing from deionized water to saline aqueous solutions.
To date all the commercially available superabsorbent materials, such as for example polyacrylates, CMC, etc, show such a sensitivity to saline concentration (K. Nukushina; Chem. Abs. 94:66783 e).
Moreover, the gels of said superabsorbent polymers show the highest absorbing capacity when the pH of the aqueous solutions, which they are contacted with, is between 8 and 10.
Said absorbing capacity is strongly reduced in the pH range lower than 5, as it can be seen from Table A ("Absorbency" by Pronoy Chatterjee, 1985, pag. 206).


TABLE A ______________________________________ Effect of pH on the absorbing capacity of sodium polyacrylate. Free swelling capacity pH (g H.sub.2 O/g) ______________________________________ 12 85 7 90 5 60 3 <10 ______________________________________
The superabsorbing materials presently known belong to two main classes: as carboxymethylcellulose, acrylonitrile grafted starches, etc; polyacrylamides, polyethyleneoxides, etc., which are obtained according to several processes, such as for example reverse phase polymerization, radiation-induced polymerization, etc..
Superabsorbent materials are applied in several industrial fields: their use has been proposed in agriculture as sowing adjuvant, in building, in alkaline batteries manufacturing, in filter media manufacturing.
However, their main use, in association with cellulose fibers, is in the field of the hygienic and sanitary products, as highly absorbing material, used in lady's napkins, diapers for infants and incontinent adults.
It has now been found that crosslinked polyetheramidoamine polymers, obtained from primary or secondary diamines and containing ether and bisacrylamido groups, can gelify when absorbing aqueous liquids in amounts which are many times their own weight, thus showing superabsorbency characteristics.
U.S. Pat. No. 3,865,723 discloses both linear and crosslinked polyamidoamine derivatives as heparin complexing agents useful in the biomedical field.
Polymers consisting of structures derived from primary amines or di-secondary amines and bisacrylamides, both linear and crosslinked, by means of primary diamine, are described by Ferruti and Barbucci, Adv. in Polym. Sci. 58, p.55-92, Springer Verlag, 1984, wherein their use in the biomedical field is provided.
In the

REFERENCES:
Journal of Applied Science, vol. 28, 1983, pp. 3361-3368, Pesavento, et al, "Applied Macroinorganics. IV. Effects of the Crosslinking Agent on Protonation, and Metal Ions Complexing Abilities, of Ion Exchange Resins with Poly(amido-Amine) Structure".
Biomaterials, vol. 5, Nov. 1984, pp. 357-361, Tanzi, et al, "Synthesis and characterization of poly(amido-amines)s belonging to two different homologous series".
Chemical Abstracts, vol. 106, No. 26, 29 Jun. 1987, Abstract No. 214758j, Kopylova, et al, "Structure and properties of cross-linked hydrogels based on a poly(acrylic acid)-polyethyeleneimine polyelectrolyte complex", p. 26, column 2.
Chemical Abstracts, vol. 114, No. 14, 8 Apr. 1991, Abstract No. 123814y, Penczek, et al, "Preparation of cross-linked hydrogels", p. 51, column 1.

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