Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Utility Patent
1999-06-25
2001-01-02
Fortuna, Ana (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S651000, C210S908000, C210S690000
Utility Patent
active
06168719
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for purification of an ionic polymer compound, and more specifically to a method for purification comprising efficiently removing ionic low-molecular impurities such as remaining monomers from the ionic polymer compound.
BACKGROUND ART
In general, when low-molecular impurities are separated and removed from polymer compounds, in many cases separation and removal are carried out by volatilization. However, in a case where the low-molecular impurities are ionic, as in the case of electrolytes, in many cases such low-molecular impurities are non-volatile, in which case this volatilizing method cannot be applied thereto.
In addition, although there can be considered a method of extracting polymer compounds with a solvent different from the solvent for a polymer solution, it would be difficult to choose an appropriate solvent therefor, and a large amount of a solvent is used, involving a risk. Also, the procedures become complicated, requiring a step of removing remaining solvents from the polymer compounds, thereby making it impractical.
Also, a method of removing low-molecular impurities with an ultrafiltration membrane is disclosed in Japanese Patent Laid-Open No. Hei 3-66705 and Japanese Examined Patent Publication No. Hei 7-59609. These methods are directed to separation of the polymer compound from the low-molecular impurities by the difference in the sizes of the molecules of the polymer compound and the low-molecular impurities. According to these methods, the concentration of the remaining low-molecular impurities can be lowered to a given level without further using an extract other than the polymer solution. However, there arises a problem that a great deal of time is required for purification.
In addition, Japanese Patent Laid-Open No. Hei 8-217802 discloses a method for removing a low-molecular compound having a molecular weight of 10,000 or less and unreacted monomers from the ionic polymer compound with an ultrafiltration membrane. However, even in this method, there is exemplified a method of removing these components with concentrating the polymer concentration during treatment from 1% by weight to about 5% by weight. Therefore, there has yet remained a problem that filtration must be carried out after diluting to a considerably low concentration.
Apart from the above methods, a method of removing low-molecular impurities comprising unreacted monomers as a main component from the cationic polymer compound utilizing electrodialytic method is disclosed in Japanese Examined Patent Publication No. Hei 7-68298. However, in this electrodialytic method, the ionic substances having a low molecular weight are removed by flowing an electric current therethrough. Therefore, when the concentration of the ionic substances having a low molecular weight is in the range of less than 0.1%, the electric current which is allowed to send becomes extremely small, so that a great deal of time would be required for purification.
DISCLOSURE OF INVENTION
Accordingly, an object of the present invention is to provide a method for purification of an ionic polymer compound comprising efficiently removing low-molecular impurities, such as ionic remaining monomers, which are charged identically to the ionic polymer compound from the ionic polymer compound with a shorter period of time.
As a result of the studies, the present inventors have found that the low-molecular impurities having counter ions common with the ionic polymer compound can be efficiently removed by the use of an ultrafiltration membrane and/or a reverse osmosis membrane from an aqueous solution containing the ionic polymer compound and the low-molecular impurities which are charged identically to the ionic polymer compound, under conditions that the concentration of the ionic polymer compound is from 7 to 20% by weight, and that the amount of electric charges of the ionic polymer compound in the aqueous solution is 0.30 gram-equivalent/liter or more. The present invention has been completed based on this finding.
Specifically, in sum, the present invention pertains to:
[1] a method for purification of an ionic polymer compound, characterized by removing low-molecular impurities by the use of an ultrafiltration membrane and/or a reverse osmosis membrane from an aqueous solution containing the ionic polymer compound and low-molecular impurities which are charged identically to the ionic polymer compound, under conditions that a concentration of the ionic polymer compound is from 7 to 20% by weight, and that an amount of charges of the ionic polymer compound in the aqueous solution is 0.30 gram-equivalent/liter or more;
[2] the method for purification of an ionic polymer compound according to item [1] above, characterized in that an amount of charges possessed by the ionic polymer compound in the aqueous solution is 3.0 gram-equivalent/kg or more;
[3] the method for purification of an ionic polymer compound according to item [1] above, characterized in that 60% by weight or more of solvents constituting the aqueous solution is water;
[4] the method for purification of an ionic polymer compound according to item [1] above, characterized in that the ultrafiltration membrane or reverse osmosis membrane is a ceramic filter;
[5] the method for purification of an ionic polymer compound according to item [1] above, characterized in that an average pore size of the ultrafiltration membrane or reverse osmosis membrane is from 4 to 100 nm;
[6] the method for purification of an ionic polymer compound according to item [1] above, characterized in that the ionic polymer compound has a weight-average molecular weight of 5,000 or more, and the low-molecular impurities have a molecular weight of 500 or less;
[7] the method for purification of an ionic polymer compound according to item [1] above, characterized in that the ionic polymer compound is a cationic polymer compound;
[8] the method for purification of an ionic polymer compound according to item [7] above, characterized in that the cationic polymer compound is synthesized from a cationic monomer which is a quaternary ammonium salt; and
[9] a method for purification of an ionic polymer compound characterized in that after purification of an ionic polymer compound by the use of the method for purification according to item [1] above, the ionic polymer compound is brought into contact with an ion exchange resin.
BEST MODE FOR CARRYING OUT THE INVENTION
The ionic polymer compound usable in the present invention will be explained hereinbelow. The dissociating group of the ionic polymer compound is not particularly limited, as long as the dissociating group is a group that forms a salt in the presence of an acid or base. The dissociating group may be any of anionic, cationic, or amphoteric group. For instance, in the preparation of the cationic polymer compound, in many cases cationic monomers with odors remain in the resulting reaction mixture, so that such a dissociating group is suitably used from the viewpoint of giving improved odors for the cationic polymer compound. Concrete examples of the salt-forming group includes carboxyl group, sulfonic acid residual group, sulfuric acid residual group, phosphoric acid residual group, nitric acid residual group, amino group, ammonium group, and the like. Two or more of these groups may be contained in one compound.
Concrete examples of the above polymer compounds include, for instance, natural or semisynthesized polymers, including mucopolysaccharides, such as hyaluronic acid, sodium hyaluronate, and sodium chondroitin sulfate; and hemi-celluloses, such as alginic acid, sodium alginate, ammonium alginate, a sodium salt of carboxymethyl cellulose, and carboxymethyl amylose, but synthesized polymers are more preferable. The synthesized polymer includes, for instance, those prepared from polymerizing one or more of the monomer
Hiramatsu Shinobu
Imaki Takuya
Nojiri Naoki
Shida Jun
Shimokawa Keishi
Fortuna Ana
Kao Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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