高含量二甲戊灵微囊悬浮剂物理稳定性的影响因素及优化

Factors that affecting physical stability of high content pendimethalin capsule suspension and its optimization

采用界面聚合法制备了500 g/L的二甲戊灵微囊悬浮剂；考察了乳化剂和囊壁材料的质量分数、固化温度、分散剂和黏度调节剂等对微囊平均粒径、包封率、分散状态和物理稳定性的影响；通过红外光谱（FT-IR）表征了微囊的包封情况。结果表明：随着4，4’-二苯基甲烷二异氰酸酯（MDI）质量分数的增加，微囊的包封率逐渐增大；当MDI的质量分数为3.0%～4.0%时，可制备出包封率大于87.0%、载药量约为82.0%的微囊；当EL-40（蓖麻油聚氧乙烯醚）的质量分数为1.0%和3.0%时，平均粒径分别为15.5和4.00 μ m，热贮析水率分别为25.1%和1.73%；在固化温度为40、50和60℃下制备的样品，热贮（54 ℃±2 ℃，14 d）后分别表现为团聚严重，轻微粘连和保持良好形貌、囊间无粘连；当采用相对分子质量为1.0×104～1.2×104、磺化度0.85 mmol/g的木质素磺酸钠，且其质量分数为3.0%时，制剂的析水率（热贮）仅为4.76%，粒子间无粘连，囊形圆滑；黄原胶和硅酸镁铝配伍使用可明显提高制剂的贮存稳定性，当黄原胶的质量分数为0.07%、硅酸镁铝的质量分数为1.0%时，热贮析水率仅为2.12%，而且流动性良好；FT-IR结果表明，二甲戊灵原药大部分被包封于微囊中，且其在1 248和1 322 cm-1处硝基的吸收峰向低波段移动，变为1 231和1 307 cm-1。

Interfacial polymerization was adopted for pendimethalin 500 g/L capsule suspension. Effects of emulsifier content, wall material content, curing temperature, suspending agent and thickening agent on the average diameter, encapsulation efficiency, dispersed state, physical stability of microcapsule were investigated. Infrared spectroscopy （FT-IR） was used to characterize the encapsulation of microcapsule. It was indicated that encapsulation efficiency gradually enhanced with the amount of MDI increased. Microcapsule was prepared with encapsulation efficiency exceeding 87.0% and drug loading about 82.0% when MDI content（mass fraction） was 3.0% to 4.0%. When EL-40 content reached 1.0% and 3.0%, average diameter were 15.5 μ m and 4.00 μ m respectively and water separating proportions after thermal storage （54 ℃±2 ℃, 14 d） were 25.1% and 1.73%, respectively. The sample prepared with the curing temperature of 40, 50 and 60 ℃ were respectively severely agglomerated, agglomerated slightly and kept good morphology without agglomeration after thermal storage. Relative molecular mass and the sulfonation degree of sodium lignosulphonate were 1.0×104-1.2×104 and 0.85 mmol/g, respectively. When sodium lignosulphonate content was 3.0%, water separating proportion was only 4.76% and the particle shape kept smoothly without aggregation. Combination of xanthan gum and veegum could significantly improve the storage stability of the preparation. Water separating proportion of the preparation was only 2.12% and the flowability was fine after thermal storage when xanthan gum content was 0.07% and veegum content was 1.0%. Infrared spectroscopy results showed that the majority of pendimethalin was encapsulated in the microcapsule, but its absorption peak at 1 248 and 1 322 cm-1 were shifted to 1 231 and 1 307 cm-1.