To obtain the subject filter which shows high efficiency for removing leukocyte without adverse effect on living bodies and is excellent in withdrawing rates of platelets and red blood cells by applying chitosan or modified chitosan on the surface of unwoven cloth.
The objective filter is obtained by immersing unwoven cloth, which is made of synthetic or natural fibers and is preferably 3 μm or less in the space between adjacent fibers, into a solution of chitosan or modified chitosan (a graft polymer of chitosan and a blood affinitive polymer selected from polydimethylaminoethyl methacrylate, polymethyl methacrylate, polyacrylic acid and sodium polyvinyl sulfonic acid), which is contained in a concentration of 0.1-5 wt.% in an organic acid or an inorganic acid and possesses an average molecular weight of preferably 200,000-700,000, for 30-120 min., if necessary, carrying out ultrasonication for 2 hrs. or less during immersing and further irradiating ultraviolet ray to the resultant filter in 10 mJ/cm2 or less.
JO SHOHO
TEI HEIGYOKU
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