In this paper, porous structures of the swollen hydrogels of the cross-linked CM-LBKP were examined by solute exclusion technique. Water absorbents prepared by cross-linking of CM-LBKP with different types of polyethylene glycol diglycidyl ethers (PEGDGEs) had very porous structures. The total pore volume of cross-linked CM-LBKP up to 560 A in width was about 100 times of that of untreated pulps. Increased amount of cross-linking agent bound to CM-LBKP not only decreased the total pore volume,

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... ut also decreased the pore size with increased contribution of small pores up to 560 A in width. Re-cross-linking of the water soluble fraction from the first cross-linking of CM-LBKP seemed to proceed more homogeneously and eventually to give more homogeneous distribution of cross-linkage. Thereby re-cross-linking products had higher water absorbency and lower water solubility.