Radiation crosslinking of carboxymethyl starch

カルボキシメチルデンプンの放射線架橋

長澤 尚胤; 八木 敏明; 久米 民和; 吉井 文男

Nagasawa, Naotsugu; Yagi, Toshiaki; Kume, Tamikazu; Yoshii, Fumio

カルボキシメチルデンプン(CMS)をペースト状態の高濃度水溶液で照射して橋かけし、生分解性ハイドロゲルを合成した。CMSの橋かけに必要な濃度,蒸留水や生理食塩水中のゲルの吸水性及び生分解性について検討した。最適な濃度は、20から50%で、1gの乾燥ゲルは、蒸留水中で約500gを、生理食塩水中で約26gを吸水した。また、CMSゲルの生分解性は調整堆肥内で2週間後、約40%と未照射と変わらず、標準セルロース粉末よりも分解しやすいことがわかった。デンプンはアミロースとアミロペクチンの二成分からなっており、橋かけに寄与する成分をカルボキシメチルアミロースとカルボキシメチルアミロペクチンを用いて検討した結果、アミロペクチン成分が橋かけに寄与していることがわかった。

A new biodegradable starch derivative hydrogel, carboxymethyl starch (CMS) hydrogel, was synthesized by irradiation in high concentrated solution (in the so-called paste-like condition). The effect of the solution concentration on the crosslinking of CMS, the properties of formed hydrogel and the biodegradability were investigated. The crosslinking of CMS was induced by irradiation at concentration range from 20 to 50 %. 1 g of the dry gel formed from the solution at concentration of 40 % crosslinked at dose of 2 kGy was able to absorb about 500 and 26 g of distilled water and 0.9 % NaCl, respectively. Biodegradation of crosslinked CMS (irradiated in 50 % solution at a dose of 5 kGy) by controlled composting was about 40 % after 2 weeks which was faster than standard cellulose powder. The contribution of crosslinking in CMS was elucidated from crosslinking behaviors of carboxymethyl amylopectin (CMAP) and carboxymethyl amylose (CMA). The crosslinked CMAP (irradiated at a concentration range from 10 to 50 %) reveal higher gel fraction and water-uptake than that of CMA. The amylopectin region in CMS is predominantly responsible for crosslinking of CMS.