Ion exchanger and method of producing the same

1. An ion exchanger comprising a melt-extrusion-formed body of a resin composition containing a granular ion-exchange resin and a low-melting polyolefin resin having a melting point of not higher than 150° C., said melt-extrusion-formed body satisfying the following conditions of:

(a) containing said granular ion-exchange resin at a ratio of not less than 30% by weight but less than 50% by weight, and said low-melting polyolefin resin in an amount of more than 100 parts by weight but not more than 150 parts by weight per 100 parts by weight of said granular ion-exchange resin;

(b) having a melt index in a range of 1 to 5 g/10 min, as measured at 190° C.; and

(c) having a saturated water content of not less than 30% as calculated from the wet weight of the melt-extrusion-formed body after being dipped in 1.0N NaCl aqueous solution maintained at 60° C. for 24 hours and the dry weight thereof according to the following formula (1):

(wet weight−dry weight)×100/wet weight  (1);

wherein said low-melting polyolefin resin is polyethylene;

wherein said granular ion-exchange resin has a saturated water content of not less than 50%, and the saturated water content is calculated from the wet weight of the resin after being dipped in 1.0N NaCl aqueous solution maintained at 60° C. for 3 hours and the dry weight thereof according to the above formula (1);

wherein said ion exchanger has an average surface roughness of not more than 50 μm; and

wherein the ion exchanger is of a tubular shape.