Bleaching and dyeing; fluid treatment and chemical modification – Chemical modification of textiles or fibers or products thereof – Cellulose fibers
Patent
1998-08-06
2000-02-22
Einsmann, Margaret
Bleaching and dyeing; fluid treatment and chemical modification
Chemical modification of textiles or fibers or products thereof
Cellulose fibers
1621576, H01J 845
Patent
active
060275367
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The invention pertains to a process for the preparation of a material with a high water and salt solutions absorbency, said material containing mainly cellulose.
A material with a high water and (isotonic) salt solutions absorbency is also known as a superabsorbent. Superabsorbents are used, int. al., in personal hygiene products, such as disposable diapers, tampons, sanitary napkins, and incontinence pads. Superabsorbents in the form of fibres can be used, int. al., in moisture-absorbing cloths or in towels.
DESCRIPTION OF RELATED ART
A superabsorbent mainly containing cellulose is known from WO 93/112275. In this patent application the preparation of cellulose based superabsorbents, notably cellulose based fibres, is described, which comprises cellulose fibres being spun and the thus formed fibres being subjected to chemical modification in a subsequent process to form carboxy-methyl-cellulose (CMC) fibres. However, preparing a material with a high water and salt solutions absorbency in two different process steps (spinning the fibres and subjecting them to chemical modification) constitutes a substantial drawback to this process.
CMC in the powdered form is known as a material with a high moisture absorbency and is used, int. al., as a thickener.
U.S. Pat. No. 3,658,790 also discloses a process for preparing cellulose based fibres with a high absorbent capacity for fluid. This process involves several steps, such as saturating cellulose fibres (in the form of pulp sheets) with an aqueous phosphoric acid/urea solution, drying and reacting the obtained product at elevated temperature, dispersing the obtained sheets in water, a washing treatment, a treatment with acid, a treatment with lye, a second washing treatment, and, optionally, mechanical refining of the obtained product. Shaping of the obtained fibres is only possible by an extra process step
In addition to these superabsorbents, superabsorbents containing salts of polyacrylic acids are known. A drawback to materials based on the salts of polyacrylic acids is their poor biodegradability as compared with cellulose based materials.
Surprisingly, a simple process for preparing superabsorbents which mainly contain cellulose has now been found. This process makes it possible to prepare a material with a high water and (isotonic) salt solutions absorbency which has better biodegradability than the materials based on polyacrylic acids.
SUMMARY OF THE INVENTION
The invention consists in that in the process mentioned in the opening paragraph cellulose is dissolved in a solvent containing phosphoric acid, with a solution being obtained which has 94-100 wt. % of the following constituents: 50 wt. % of water.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The term phosphoric acid in this patent application refers to all inorganic acids of phosphorus and their mixtures. Orthophosphoric acid is the acid of pentavalent phosphorus, i.e. H.sub.3 PO.sub.4. Its anhydrous equivalent, i.e. the anhydride, is phosphorus pentoxide (P.sub.2 O.sub.5). In addition to orthophosphoric acid and phosphorus pentoxide there is, depending on the quantity of water in the system, a series of acids of pentavalent phosphorus with a water-binding capacity in between those of phosphorus pentoxide and orthophosphoric acid, such as polyphosphoric acid (H.sub.6 P.sub.4 O.sub.13, PPA).
The weight percentage of phosphorus pentoxide in the solvent is calculated by starting from the overall quantity by weight of phosphoric acid including its anhydrides and the total quantity of water in the solvent, converting the acids into phosphorus pentoxide and water, and calculating the percentage of said overall quantity by weight made up by phosphorus pentoxide.
In this description water derived from cellulose or from substances which are part of the other constituents and water which is added to obtain the solution are not included in the calculation of the concentration of phosphorus pentoxide in the solvent.
The weight percentage of phosphorus pentoxide in the solution is
REFERENCES:
patent: 429535 (1890-06-01), Achilles de Khotinsky
patent: 3658790 (1972-04-01), Bernardin
patent: 3691154 (1972-09-01), Bernardin
Brian R. Shmaefsky, "How-to-do-it, Artificial Urine for Laboratory Testing", The American Biology Teacher, vol. 52, No. 3, Mar. 1990, pp. 170-172.
Boerstoel Hanneke
Maatman Hendrik
Westerink Jan Barend
Akzo Nobel N.V.
Einsmann Margaret
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