Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1992-09-25
1994-11-01
Nutter, Nathan M.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
536 46, 536103, C08B 3716, C08G 6526, C08G 6524, B01D 1508
Patent
active
053608992
DESCRIPTION:
BRIEF SUMMARY
The invention relates to hydrophilic cyclodextrin polymers which are swellable in water and have a high cyclodextrin content, and a process for their preparation.
Cyclodextrins are cyclic, non-reducing oligosaccharides, consisting of .alpha.-D-glucose units which have exclusively 1,4-glucoside links. Currently .alpha.-, .beta.- and .gamma.-cyclodextrin, which are built up from 6, 7 and 8 anhydroglucose units respectively, are available in relatively large amounts. The most interesting property of the cyclodextrins is their ability to form inclusion complexes (host/guest compounds). In these compounds hydrophobic guest molecules of suitable size are enclosed in the cyclodextrin cavity and reversibly bonded by hydrophobic interactions, van der Waals forces and, in some cases, also hydrogen bridge bonds. By far the majority of applications of cyclodextrins are also based on the formation of these inclusion complexes. Thus, for example, they are suitable for chromatographic separations, as catalysts, as stabilizers, for solubilization or for converting liquid substances into the solid aggregate state.
Since, because of their chiral C atoms, cyclodextrins are able to act as enantion-selective receptors, chromatographic separations of suitable enantiomers are also possible with the participation of cyclodextrin inclusion compounds. As a result of these selective receptor characteristics, the stereoselectivity of chemical reactions can also be increased by cyclodextrins. However, if dissolved cyclodextrin is used as separating agent or extractant or as a catalyst, the separation of the inclusion compound from the system and the liberation of the included compound from the cyclodextrin are difficult. Therefore, an immobilization of cyclodextrins with maintenance of their inclusion capacity is advantageous. Immobilized cyclodextrins can be used, for example, as the stationary phase in separation processes in chromatography. Hitherto, an immobilization of cyclodextrins has been attempted in very diverse ways. However, all previously described immobilization methods have defects.
Insoluble (immobilized) cyclodextrins and their use in separation, processes have already been described by Solms and Egli (Helv. Chim. Actra 48, 1225 (1965)). In German Patent Specification DE 29 27 733, J. Szejtli et al. describe cyclodextrin-polyvinyl alcohol polymers and a process for their preparation. Compared with the cyclodextrin gels known hitherto, these have somewhat improved mechanical properties.
In J. Food Sci. 48, 646, (1983), P. E. Shaw and C. W. Wilson describe the use of such cyclodextrin polymers for separating bitter substances from citrus juices.
In Gordian 89 (3), 43 (1989) A. Ujhazy and J. Szejtli also describe the separation of a bitter substance (naringin) from aqueous solutions with the aid of a cyclodextrin bead polymer.
In the case of the already known cyclodextrin gels which have been mentioned, the immobilization of the cyclodextrins is achieved by bifunctional crosslinking agent units. A three-dimensional, hydrophilic cyclodextrin lattice which is swellable in water is formed. Material in bead form can be obtained by means of a method related to inverse suspension polymerization. The crosslinking agent units used are preferably epichlorohydrin or diepoxy compounds. However, all the cyclodextrin polymers prepared in this way which have been described hitherto are unsuitable for packing columns which are operated under a pressure distinctly higher than atmospheric pressure, since even under a pressure of 3 bar there is already a deformation of the packing such that the flow rates through a packed column are low. Even when the pressure is increased, the flow rates do not increase substantially because of the softness of the material. High flow rates are, however, desirable on economic grounds. Furthermore, by increasing the pressure for a given column packing material an increase in the separation efficiency can also be achieved.
In order to obtain a cyclodextrin-containing material which is suitable as column pac
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J. Solms et al., Helv. Chem. Acta 48 /1965), 1225, "Harze mit Einschlusshohlraumen von Cyclodextrin-Struktur".
P. E. Shaw et al., J. Food Sci., vol. 48 (1983), 646, "Debittering Citrus Juices with beta-Cyclodextrin Polymer".
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Kreuzer Franz-Heinrich
Nussstein Peter
Schmitt-Sody Wolfgang
Staudinger Guenther
Steinert Wolfram
Consortium fur elektrochemische Industries GmbH
Nutter Nathan M.
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