Radiation crosslinking of polysaccharide derivatives

多糖誘導体の放射線橋か

長澤 尚胤; Wasikiewicz, J. M.; 八木 敏明; 三友 宏志*; 吉井 文男; 玉田 正男

Nagasawa, Naotsugu; Wasikiewicz, J. M.; Yagi, Toshiaki; Mitomo, Hiroshi*; Yoshii, Fumio; Tamada, Masao

天然多糖類は自然界に多量に存在しており、生分解性を有する利点からに応用され、カルボキシメチルセルロース(CMC),カルボキシメチルデンプン(CMS)などの化学修飾された水溶性の多糖類誘導体は食品や医薬分野のような多くの産業に広く応用されている。これらの多糖類の水溶液に対する電離放射線の効果は分解を導くが、ペーストのような10-60%の高濃度状態で分子間の橋かけを引き起こすことを見いだした。これらの濃度が20%で、線量が20kGy照射したとき、CMC, CMS, カルボキシメチルキチン(CMCT)とカルボキシメチルキトサン(CMCS)のゲル分率は、それぞれ38, 54, 8, 0%で、CMCSのゲル分率は100kGyの高い線量において40%であった。得られたハイドロゲルは、乾燥ゲルを1とするとおよそ500倍吸水して膨潤した。分解や橋かけの収率とゲル化線量ような放射線パラメータをCharlesby-Rosiak式をもとにしてゾル-ゲル解析によって評価した。それらの結果から、ヒドロキシル基,カルボキシル基,アミノ基と-アセトアミノ基といった分子鎖中の官能基と分子量が多糖類誘導体の放射線橋かけに対して最も重要な因子であると結論した。これらのハイドロゲルの利点は、使用後に生分解することである。放射線橋かけした生分解性ハイドロゲルを家畜排せつ物を堆肥にするための吸水性材料や床擦れ防止マットでの体圧分散材料として応用したので報告する。

In the past few decades a great interest has been focused on the research of naturally occurring polymers, so called polysaccharides. Their main advantages are occurrence in large amounts in nature, as well as their biodegradability. The chemically modified, water-soluble polysaccharide derivatives such as carboxymethylcellulose (CMC), carboxymethylstarch (CMS), carboxymethylchitin (CMCT) and carboxymethylchitosan (CMCS) have been widely used in many industrial applications such as food and medicine fields. The effect of ionizing radiation on aqueous solution of these polysaccharides leads to their degradations. However, the -rays and the electron beam induced the intermolecular crosslinking in the paste-like conditions, i.e., concentration of 10-60%. When the concentration of these polymers was 20%, the gel fractions of CMC, CMS, CMCT and CMCS were 38, 54, 8, 0% at a dose of 20 kGy, respectively while that of CMCS was 40% at high dose of 100 kGy. The obtained biodegradable hydrogels swelled significantly up to about 500 times of dried gel in aqueous media. Radiation parameters of irradiation, such as yields of degradation and crosslinking and the gelation dose, were evaluated by sol-gel analysis on the basis of Charlesby-Rosiak equation. From comparison of the results, we concluded that the structure of functional groups as hydroxyl, carboxymethyl, amino and N-acetylamino groups and molecular weight of polymers are the most important factors for radiation crosslinking of polysaccharide derivatives. If the material has the branched chain structure with carboxymethyl group and high molecular weight, it was crosslinked easily by radiation. The great advantage of these hydrogels is that they might be biodegraded after utilization. The biodegradable hydrogel polymers, synthesized by radiation crosslinking were applied as pressure dispersion materials in the bedsore-prevention mat and water-adsorbent materials for the composting of the livestock excreta.