Patent ID: 7307157

Claim:
A process for producing a hydrogel of a chitin derivative having a crosslinked structure, comprising adding purified water to a water-soluble chitin derivative, kneading the resulting mixture to prepare a concentrated paste having a concentration of 30% to 50% which is thick enough not to flow out if the container is tilted, and irradiating the concentrated paste with an ionizing radiation to a dose of 5 to 300 kGy to obtain a water-insoluble gel of the chitin derivative having a crosslinked structure which is swelled upon immersion in a large volume of water to form a hydrogel and absorbs water in a volume at least 5 times as much as its own weight, wherein said chitin derivative is selected from the group consisting of carboxymethyl-chitin, carboxyethyl-chitin, methyl-chitin, ethyl-chitin, hydroxyethyl-chitin, hydroxypropyl-chitin, oxidized chitin, acetyl-chitin, aminoalkyl-chitin, allyl-chitin, and blends thereof.